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Sample records for acid titration method

  1. Standard test method for total base number of petroleum products by potentiometric perchloric acid titration

    SciTech Connect

    Not Available

    1980-01-01

    This method covers the determination of basic constituents in petroleum products by titration with perchloric acid. For many materials the results obtained by this method will be similar to those obtained by Method D 664-IP 177. With certain compounds such as strongly overbased oil additives and nitrogenous polymeric compounds, higher results may be obtained. Summary of method: the sample is dissolved in an essentially anhydrous mixture of chlorobenzene and glacial acetic acid and titrated with a solution of perchloric acid in glacial acetic acid with a potentiometric titrimeter. A glass indicating electrode and a calomel reference electrode are used, the latter being connected with the sample solution by means of a salt bridge. The meter readings are plotted against the respective volumes of titrating solution, and the end point is taken at the inflection in the resulting curve. Occasionally certain used oils give no inflection in the standard titration, in which case a back titration modification with sodium acetate titrant is employed. Total base number is the quantity of perchloric acid expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 g of sample.

  2. Determining surface areas of marine alga cells by acid-base titration method.

    PubMed

    Wang, X; Ma, Y; Su, Y

    1997-09-01

    A new method for determining the surface area of living marine alga cells was described. The method uses acid-base titration to measure the surface acid/base amount on the surface of alga cells and uses the BET (Brunauer, Emmett, and Teller) equation to estimate the maximum surface acid/base amount, assuming that hydrous cell walls have carbohydrates or other structural compounds which can behave like surface Brönsted acid-base sites due to coordination of environmental H2O molecules. The method was applied to 18 diverse alga species (including 7 diatoms, 2 flagellates, 8 green algae and 1 red alga) maintained in seawater cultures. For the species examined, the surface areas of individual cells ranged from 2.8 x 10(-8) m2 for Nannochloropsis oculata to 690 x 10(-8) m2 for Dunaliella viridis, specific surface areas from 1,030 m2.g-1 for Dunaliella salina to 28,900 m2.g-1 for Pyramidomonas sp. Measurement accuracy was 15.2%. Preliminary studies show that the method may be more promising and accurate than light/electron microscopic measurements for coarse estimation of the surface area of living algae. PMID:9297794

  3. Determination of nitric acid in highly radioactive solutions by the method of coulometric titration

    SciTech Connect

    Gromov, V.S.; Kuperman, A.Ya.; Smirnov, Yu.A.

    1988-11-01

    A procedure, a cell, and an electronic block have been developed for a long-distance determination of nitric acid in highly radioactive industrial solutions by coulometric titration under hot chamber conditions. A solution of a mixture of ammonium and potassium oxalates was used for the background and anoide electrolytes. This solution prevents the hydrolysis of the metal ions and appreciably decreases the rate of accumulation of the acid in the anode chamber of the cell. Titration with 0.1-0.5 A currents is carried out with internal generation of hydroxyl ions. The cell was prepared from a radiation-resistant and transparent material, poly(methyl methacrylate). The anode and cathode chambers were separated by a cellophane membrane, reinforced by a porous glass filter. By using the electronic coulometric block working together with a pH-meter (EV-74 or I-130) and with an automatic titration block (BAT-15), the titration can be carried out automatically, and the determination results can be obtained in a digital form.

  4. Theoretical considerations and a simple method for measuring alkalinity and acidity in low-pH waters by gran titration

    USGS Publications Warehouse

    Barringer, J.L.; Johnsson, P.A.

    1996-01-01

    Titrations for alkalinity and acidity using the technique described by Gran (1952, Determination of the equivalence point in potentiometric titrations, Part II: The Analyst, v. 77, p. 661-671) have been employed in the analysis of low-pH natural waters. This report includes a synopsis of the theory and calculations associated with Gran's technique and presents a simple and inexpensive method for performing alkalinity and acidity determinations. However, potential sources of error introduced by the chemical character of some waters may limit the utility of Gran's technique. Therefore, the cost- and time-efficient method for performing alkalinity and acidity determinations described in this report is useful for exploring the suitability of Gran's technique in studies of water chemistry.

  5. Acid Rain Analysis by Standard Addition Titration.

    ERIC Educational Resources Information Center

    Ophardt, Charles E.

    1985-01-01

    The standard addition titration is a precise and rapid method for the determination of the acidity in rain or snow samples. The method requires use of a standard buret, a pH meter, and Gran's plot to determine the equivalence point. Experimental procedures used and typical results obtained are presented. (JN)

  6. Coulometric titration of acids in non-aqueous solvents.

    PubMed

    Fritz, J S; Gainer, F E

    1968-09-01

    Coulometric titrations of mineral acids, sulphonic acids, carboxylic acids, enols, imides and phenols have been carried out in t-butanol or in acetone with electrically generated tetrabutylammonium hydroxide. Either a potentiometric titration or a visual indicator end-point may be used. The amount of acid titrated ranges from 10 to 60 muequiv, and the precision and accuracy of the method are excellent. PMID:18960387

  7. Sequential injection titration method using second-order signals: determination of acidity in plant oils and biodiesel samples.

    PubMed

    del Río, Vanessa; Larrechi, M Soledad; Callao, M Pilar

    2010-06-15

    A new concept of flow titration is proposed and demonstrated for the determination of total acidity in plant oils and biodiesel. We use sequential injection analysis (SIA) with a diode array spectrophotometric detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS). This system is based on the evolution of the basic specie of an acid-base indicator, alizarine, when it comes into contact with a sample that contains free fatty acids. The gradual pH change in the reactor coil due to diffusion and reaction phenomenona allows the sequential appearance of both species of the indicator in the detector coil, recording a data matrix for each sample. The SIA-MCR-ALS method helps to reduce the amounts of sample, the reagents and the time consumed. Each determination consumes 0.413ml of sample, 0.250ml of indicator and 3ml of carrier (ethanol) and generates 3.333ml of waste. The frequency of the analysis is high (12 samples h(-1) including all steps, i.e., cleaning, preparing and analysing). The utilized reagents are of common use in the laboratory and it is not necessary to use the reagents of perfect known concentration. The method was applied to determine acidity in plant oil and biodiesel samples. Results obtained by the proposed method compare well with those obtained by the official European Community method that is time consuming and uses large amounts of organic solvents. PMID:20441941

  8. Determination of Acidity Constants by Gradient Flow-Injection Titration

    ERIC Educational Resources Information Center

    Conceicao, Antonio C. L.; Minas da Piedade, Manuel E.

    2006-01-01

    A three-hour laboratory experiment, designed for an advanced undergraduate course in instrumental analysis that illustrates the application of the gradient chamber flow-injection titration (GCFIT) method with spectrophotometric detection to determine acidity constants is presented. The procedure involves the use of an acid-base indicator to obtain…

  9. An Olfactory Indicator for Acid-Base Titrations.

    ERIC Educational Resources Information Center

    Flair, Mark N.; Setzer, William N.

    1990-01-01

    The use of an olfactory acid-base indicator in titrations for visually impaired students is discussed. Potential olfactory indicators include eugenol, thymol, vanillin, and thiophenol. Titrations performed with each indicator with eugenol proved to be successful. (KR)

  10. Simple and Automated Coulometric Titration of Acid Using Nonisolated Electrodes

    ERIC Educational Resources Information Center

    Kuntzleman, Thomas S.; Kenney, Joshua B.; Hasbrouck, Scott; Collins, Michael J.; Amend, John R.

    2011-01-01

    Coulometric titrations involve the quantification of analyte by measurements of current and time. In most coulometric titrations, the anode and cathode are placed in isolated cells that are connected by a salt bridge. By contrast, the experiments described here involve coulometric titrations (of acidic protons in solution) using a silver anode and…

  11. The Acid-Base Titration of a Very Weak Acid: Boric Acid

    ERIC Educational Resources Information Center

    Celeste, M.; Azevedo, C.; Cavaleiro, Ana M. V.

    2012-01-01

    A laboratory experiment based on the titration of boric acid with strong base in the presence of d-mannitol is described. Boric acid is a very weak acid and direct titration with NaOH is not possible. An auxiliary reagent that contributes to the release of protons in a known stoichiometry facilitates the acid-base titration. Students obtain the…

  12. A Variety of Electrochemical Methods in a Coulometric Titration Experiment

    NASA Astrophysics Data System (ADS)

    Lotz, Albert

    1998-06-01

    An experiment for a practical course is described in which the amounts of HCl and KI in a mixture of standardized solutions are determined by three coulometric titrations. The iodide content is titrated with bromine that is generated at the anode from bromide which oxidizes the I- to I2 and further to IBr2-. The titration is followed with a twin-polarizable platinum electrode which essentially records the I2 and (after the endpoint) Br2 levels. Analysis of the chloride content is performed indirectly by titration of the acid through cathodic reduction of H+ to H2. The titration is monitored with a glass electrode. Finally I- and Cl- are determined simultaneously by anodic dissolution of a silver wire with a silver electrode recording the course of the titration. The experiment provides an internal check of the quality of the analysis and presents a variety of electrochemical methods of pedagogical value. Hints for the practical performance of the experiment in laboratory courses are given, and the necessary electronic circuits for self-assembling are described. Laboratory experiences with students' data collection by hand, recorder and computer are dealt with in this experiment. A complete list of earlier papers is provided, which can be found in this Journal, on the subject of coulometric analysis.

  13. A Closer Look at Acid-Base Olfactory Titrations

    ERIC Educational Resources Information Center

    Neppel, Kerry; Oliver-Hoyo, Maria T.; Queen, Connie; Reed, Nicole

    2005-01-01

    Olfactory titrations using raw onions and eugenol as acid-base indicators are reported. An in-depth investigation on olfactory titrations is presented to include requirements for potential olfactory indicators and protocols for using garlic, onions, and vanillin as acid-base olfactory indicators are tested.

  14. Determination of the acidic sites of purified single-walled carbon nanotubes by acid base titration

    NASA Astrophysics Data System (ADS)

    Hu, H.; Bhowmik, P.; Zhao, B.; Hamon, M. A.; Itkis, M. E.; Haddon, R. C.

    2001-09-01

    We report the measurement of the acidic sites in three different samples of commercially available full-length purified single-walled carbon nanotubes (SWNTs) - as obtained from CarboLex (CLI), Carbon Solutions (CSI) and Tubes@Rice (TAR) - by simple acid-base titration methods. Titration of the purified SWNTs with NaOH and NaHCO 3 solutions was used to determine the total percentage of acidic sites and carboxylic acid groups, respectively. The total percentage of acidic sites in full length purified SWNTs from TAR, CLI and CSI are about 1-3%.

  15. Titratable acidity: a Pitts concept revisited.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2014-08-01

    Titratable Acidity (TA) in urine can be measured directly or calculated from actual and reference pH, by using the pKa₂ 6,8 for phosphate. In urine, H₂PO₄(-) represents the excretion of filtered H₂PO₄(-), filtrated HPO₄(2-) being completely reabsorbed by the proximal tubule (the Van Slyke approach). Since excretion of H₂PO₄(-) frequently exceeds its glomerular filtration, this approach is considered inadequate by Pitts. He claimed that it is the tubular H(+) secretion which converts filtered HPO₄(2-) to H₂PO₄(-), thereafter excreted in urine. This is only true under conditions of inorganic acid or neutral phosphate loading, when the maximum tubular phosphate reabsorption (TmPi) is overcharged. In controls, H₂PO₄(-) excretion is lower than its glomerular filtration, provided that acid-base status is normal and tubular phosphate reabsorption is below the TmPi. The TmPi is lower than its glomerular filtration, provided that acid-base status is normal and tubular phosphate reabsorption is below the TmPi. When the TmPi is exceeded, a portion of HPO₄(2-) escapes proximal reabsorption, reaching the distal tubule where its absorption is precluded, while tubular H(+) secretion converts HPO₄(2-) to H₂PO₄(-). In man and dog, the attainment of TmPi is evidenced by a FE% of 20%, and only beyond this limit H₂PO₄(-) excretion exceeds glomerular filtration. When FE% is lower than 20%, H₂PO₄(-) filtration exceeds excretion, HPO4(2-) being completely reabsorbed at the proximal tubule by NaPi-2a and 2c cotransporters. While Van Slyke's approach is always valid, Pitts' approach is only valid under loading conditions, when the two processes of H₂PO₄(-) excretion overlap each other. NH (+4) increases inversely to TA excretion in conditions of acidosis and tP restriction, but is independent of TA in Pi-replete dogs, independently of acidosis. PMID:24684475

  16. Titration of strong and weak acids by sequential injection analysis technique.

    PubMed

    Maskula, S; Nyman, J; Ivaska, A

    2000-05-31

    A sequential injection analysis (SIA) titration method has been developed for acid-base titrations. Strong and weak acids in different concentration ranges have been titrated with a strong base. The method is based on sequential aspiration of an acidic sample zone and only one zone of the base into a carrier stream of distilled water. On their way to the detector, the sample and the reagent zones are partially mixed due to the dispersion and thereby the base is partially neutralised by the acid. The base zone contains the indicator. An LED-spectrophotometer is used as detector. It senses the colour of the unneutralised base and the signal is recorded as a typical SIA peak. The peak area of the unreacted base was found to be proportional to the logarithm of the acid concentration. Calibration curves with good linearity were obtained for a strong acid in the concentration ranges of 10(-4)-10(-2) and 0.1-3 M. Automatic sample dilution was implemented when sulphuric acid at concentration of 6-13 M was titrated. For a weak acid, i.e. acetic acid, a linear calibration curve was obtained in the range of 3x10(-4)-8x10(-2) M. By changing the volumes of the injected sample and the reagent, different acids as well as different concentration ranges of the acids can be titrated without any other adjustments in the SIA manifold or the titration protocol. PMID:18967966

  17. Potentiometric titration and equivalent weight of humic acid

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    The "acid nature" of humic acid has been controversial for many years. Some investigators claim that humic acid is a true weak acid, while others feel that its behaviour during potentiometric titration can be accounted for by colloidal adsorption of hydrogen ions. The acid character of humic acid has been reinvestigated using newly-derived relationships for the titration of weak acids with strong base. Re-interpreting the potentiometric titration data published by Thiele and Kettner in 1953, it was found that Merck humic acid behaves as a weak polyelectrolytic acid having an equivalent weight of 150, a pKa of 6.8 to 7.0, and a titration exponent of about 4.8. Interdretation of similar data pertaining to the titration of phenol-formaldehyde and pyrogallol-formaldehyde resins, considered to be analogs for humic acid by Thiele and Kettner, leads to the conclusion that it is not possible to differentiate between adsorption and acid-base reaction for these substances. ?? 1960.

  18. Going Beyond, Going Further: The Preparation of Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    McClendon, Michael

    1984-01-01

    Background information, list of materials needed, and procedures used are provided for a simple technique for generating mechanically plotted acid-base titration curves. The method is suitable for second-year high school chemistry students. (JN)

  19. Acid-base titrations for polyacids: Significance of the pK sub a and parameters in the Kern equation

    NASA Technical Reports Server (NTRS)

    Meites, L.

    1978-01-01

    A new method is suggested for calculating the dissociation constants of polyvalent acids, especially polymeric acids. In qualitative form the most significant characteristics of the titration curves are demonstrated and identified which are obtained when titrating the solutions of such acids with a standard base potentiometrically.

  20. Ion-selective electrodes in potentiometric titrations; a new method for processing and evaluating titration data.

    PubMed

    Granholm, Kim; Sokalski, Tomasz; Lewenstam, Andrzej; Ivaska, Ari

    2015-08-12

    A new method to convert the potential of an ion-selective electrode to concentration or activity in potentiometric titration is proposed. The advantage of this method is that the electrode standard potential and the slope of the calibration curve do not have to be known. Instead two activities on the titration curve have to be estimated e.g. the starting activity before the titration begins and the activity at the end of the titration in the presence of large excess of titrant. This new method is beneficial when the analyte is in a complexed matrix or in a harsh environment which affects the properties of the electrode and the traditional calibration procedure with standard solutions cannot be used. The new method was implemented both in a method of linearization based on the Grans's plot and in determination of the stability constant of a complex and the concentration of the complexing ligand in the sample. The new method gave accurate results when using titrations data from experiments with samples of known composition and with real industrial harsh black liquor sample. A complexometric titration model was also developed. PMID:26320956

  1. On the accuracy of acid-base determinations from potentiometric titrations using only a few points from the titration curve.

    PubMed

    Olin, A; Wallén, B

    1977-05-01

    There are several procedures which use only a few points on the titration curve for the calculation of equivalence volumes in acid-base titrations. The accuracy of such determinations will depend on the positions of the points on the titration curve. The effects of errors in the stability constants and in the pH measurements on the accuracy of the analysis have been considered, and the results are used to establish the conditions under which these errors are minimized. PMID:18962087

  2. Using Spreadsheets to Produce Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    Cawley, Martin James; Parkinson, John

    1995-01-01

    Describes two spreadsheets for producing acid-base titration curves, one uses relatively simple cell formulae that can be written into the spreadsheet by inexperienced students and the second uses more complex formulae that are best written by the teacher. (JRH)

  3. Titratable acidity of beverages influences salivary pH recovery.

    PubMed

    Tenuta, Livia Maria Andaló; Fernández, Constanza Estefany; Brandão, Ana Carolina Siqueira; Cury, Jaime Aparecido

    2015-01-01

    A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conducted in vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control) were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively) and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and < 0.005 mmols OH- to reach pH 5.5, respectively). Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH. PMID:25715032

  4. Interaction between bisphenol A and tannic Acid: Spectroscopic titration approach

    NASA Astrophysics Data System (ADS)

    Omoike, Anselm; Brandt, Benjamin

    2011-06-01

    The interaction between tannic acid (TA) and bisphenol A (BPA), an endocrine disruptor, was studied by absorption and fluorescence titration techniques. The binding constants and corresponding thermodynamic parameters at different temperatures (294, 296, 298, 300 and 303 K) were determined. The intrinsic fluorescence of BPA was strongly quenched by TA and the quenching mechanism is attributed to static quenching. The thermodynamic data revealed that the formation of TA-BPA complex was exothermic, entropic-driven, and spontaneous. Furthermore, hydrogen and van der Waals interactions seem to be the major driving forces for the formation of the nonfluorescent TA-BPA complex.

  5. Developing a multipoint titration method with a variable dose implementation for anaerobic digestion monitoring.

    PubMed

    Salonen, K; Leisola, M; Eerikäinen, T

    2009-01-01

    Determination of metabolites from an anaerobic digester with an acid base titration is considered as superior method for many reasons. This paper describes a practical at line compatible multipoint titration method. The titration procedure was improved by speed and data quality. A simple and novel control algorithm for estimating a variable titrant dose was derived for this purpose. This non-linear PI-controller like algorithm does not require any preliminary information from sample. Performance of this controller is superior compared to traditional linear PI-controllers. In addition, simplification for presenting polyprotic acids as a sum of multiple monoprotic acids is introduced along with a mathematical error examination. A method for inclusion of the ionic strength effect with stepwise iteration is shown. The titration model is presented with matrix notations enabling simple computation of all concentration estimates. All methods and algorithms are illustrated in the experimental part. A linear correlation better than 0.999 was obtained for both acetate and phosphate used as model compounds with slopes of 0.98 and 1.00 and average standard deviations of 0.6% and 0.8%, respectively. Furthermore, insensitivity of the presented method for overlapping buffer capacity curves was shown. PMID:19542645

  6. A Computer-Based Simulation of an Acid-Base Titration

    ERIC Educational Resources Information Center

    Boblick, John M.

    1971-01-01

    Reviews the advantages of computer simulated environments for experiments, referring in particular to acid-base titrations. Includes pre-lab instructions and a sample computer printout of a student's use of an acid-base simulation. Ten references. (PR)

  7. Semi-automated potentiometric titration method for uranium characterization.

    PubMed

    Cristiano, B F G; Delgado, J U; da Silva, J W S; de Barros, P D; de Araújo, R M S; Lopes, R T

    2012-07-01

    The manual version of the potentiometric titration method has been used for certification and characterization of uranium compounds. In order to reduce the analysis time and the influence of the analyst, a semi-automatic version of the method was developed in the Brazilian Nuclear Energy Commission. The method was applied with traceability assured by using a potassium dichromate primary standard. The combined standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization. PMID:22154105

  8. Instrumentation and automated photometric titration procedure for total acidity determination in red wine employing a multicommuted flow system.

    PubMed

    Garcia, Ausberta Jesus Cabezas; Reis, Boaventura F

    2006-01-01

    An automated procedure for photometric titration of red wine and associated instrumentation is described. The procedure was based on the flow-batch approach implemented employing multicommutation. The photometric detection was carried out using a homemade LED-based photometer. The mixing device, LED, and photodetector were attached to the titration chamber in order to form a compact and small-sized unit. The flow system comprised an automatic injector and three-way solenoid valves, which were controlled by a microcomputer through an electronic interface card. The software, written in Quick BASIC 4.5, was designed with abilities to accomplish all steps of the titration procedure including data acquisition and real-time processing to decide about the course of titration in the following step and so forth, until the titration endpoint was reached. The usefulness of the proposed titration system was demonstrated by analyzing red wine samples. When results were compared with those obtained using the AOAC reference method, no significant difference was observed at the 95% confidence level. A relative standard deviation of ca 2% (n=9) was obtained when processing a typical red wine sample containing 7.3 gl-1 total acidity expressed as tartaric acid. PMID:17671625

  9. Instrumentation and Automated Photometric Titration Procedure for Total Acidity Determination in Red Wine Employing a Multicommuted Flow System

    PubMed Central

    Garcia, Ausberta Jesus Cabezas; Reis, Boaventura F.

    2006-01-01

    An automated procedure for photometric titration of red wine and associated instrumentation is described. The procedure was based on the flow-batch approach implemented employing multicommutation. The photometric detection was carried out using a homemade LED-based photometer. The mixing device, LED, and photodetector were attached to the titration chamber in order to form a compact and small-sized unit. The flow system comprised an automatic injector and three-way solenoid valves, which were controlled by a microcomputer through an electronic interface card. The software, written in Quick BASIC 4.5, was designed with abilities to accomplish all steps of the titration procedure including data acquisition and real-time processing to decide about the course of titration in the following step and so forth, until the titration endpoint was reached. The usefulness of the proposed titration system was demonstrated by analyzing red wine samples. When results were compared with those obtained using the AOAC reference method, no significant difference was observed at the 95% confidence level. A relative standard deviation of ca  2% (n=9 ) was obtained when processing a typical red wine sample containing 7.3 gl -1 total acidity expressed as tartaric acid. PMID:17671625

  10. Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

    ERIC Educational Resources Information Center

    Ueno, Keihei; Kina, Ken'yu

    1985-01-01

    "Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

  11. Automated titration method for use on blended asphalts

    DOEpatents

    Pauli, Adam T.; Robertson, Raymond E.; Branthaver, Jan F.; Schabron, John F.

    2012-08-07

    A system for determining parameters and compatibility of a substance such as an asphalt or other petroleum substance uses titration to highly accurately determine one or more flocculation occurrences and is especially applicable to the determination or use of Heithaus parameters and optimal mixing of various asphalt stocks. In a preferred embodiment, automated titration in an oxygen gas exclusive system and further using spectrophotometric analysis (2-8) of solution turbidity is presented. A reversible titration technique enabling in-situ titration measurement of various solution concentrations is also presented.

  12. Total Acid Value Titration of Hydrotreated Biomass Fast Pyrolysis Oil: Determination of Carboxylic Acids and Phenolics with Multiple End-Point Detection

    SciTech Connect

    Christensen, E.; Alleman, T. L.; McCormick, R. L.

    2013-01-01

    Total acid value titration has long been used to estimate corrosive potential of petroleum crude oil and fuel oil products. The method commonly used for this measurement, ASTM D664, utilizes KOH in isopropanol as the titrant with potentiometric end point determination by pH sensing electrode and Ag/AgCl reference electrode with LiCl electrolyte. A natural application of the D664 method is titration of pyrolysis-derived bio-oil, which is a candidate for refinery upgrading to produce drop in fuels. Determining the total acid value of pyrolysis derived bio-oil has proven challenging and not necessarily amenable to the methodology employed for petroleum products due to the different nature of acids present. We presented an acid value titration for bio-oil products in our previous publication which also utilizes potentiometry using tetrabutylammonium hydroxide in place of KOH as the titrant and tetraethylammonium bromide in place of LiCl as the reference electrolyte to improve the detection of these types of acids. This method was shown to detect numerous end points in samples of bio-oil that were not detected by D664. These end points were attributed to carboxylic acids and phenolics based on the results of HPLC and GC-MS studies. Additional work has led to refinement of the method and it has been established that both carboxylic acids and phenolics can be determined accurately. Use of pH buffer calibration to determine half-neutralization potentials of acids in conjunction with the analysis of model compounds has allowed us to conclude that this titration method is suitable for the determination of total acid value of pyrolysis oil and can be used to differentiate and quantify weak acid species. The measurement of phenolics in bio-oil is subject to a relatively high limit of detection, which may limit the utility of titrimetric methodology for characterizing the acidic potential of pyrolysis oil and products.

  13. Direct Sensing of Total Acidity by Chronopotentiometric Flash Titrations at Polymer Membrane Ion-Selective Electrodes

    PubMed Central

    Gemene, Kebede L.; Bakker, Eric

    2008-01-01

    Polymer membrane ion-selective electrodes containing lipophilic ionophores are traditionally interrogated by zero current potentiometry, which, ideally, gives information on the sample activity of ionic species. It is shown here that a discrete cathodic current pulse across an H+-selective polymeric membrane doped with the ionophore ETH 5294 may be used for the chronopotentiometric detection of pH in well buffered samples. However, a reduction in the buffer capacity leads to large deviations from the expected Nernstian response slope. This is explained by the local depletion of hydrogen ions at the sample-membrane interface as a result of the galvanostatically imposed ion flux in direction of the membrane. This depletion is found to be a function of the total acidity of the sample and can be directly monitored chronopotentiometrically in a flash titration experiment. The subsequent application of a baseline potential pulse reverses the extraction process of the current pulse, allowing one to interrogate the sample with minimal perturbation. In one protocol, total acidity is found to be proportional to the magnitude of applied current at the flash titration endpoint. More conveniently, the square root of the flash titration endpoint time observed at a fixed applied current is a linear function of the total acid concentration. This suggests that it is possible to perform rapid localized pH titrations at ion-selective electrodes without the need for volumetric titrimetry. The technique is explored here for acetic acid, MES and citric acid with promising results. Polymeric membrane electrodes on the basis of poly(vinyl chloride) plasticized with o-nitrophenyloctylether in a 1:2 mass ratio may be used for the detection of acids of up to ca. 1 mM concentration, with flash titration times on the order of a few seconds. Possible limitations of the technique are discussed, including variations of the acid diffusion coefficients and influence of electrical migration. PMID

  14. Characterization of acid functional groups of carbon dots by nonlinear regression data fitting of potentiometric titration curves

    NASA Astrophysics Data System (ADS)

    Alves, Larissa A.; de Castro, Arthur H.; de Mendonça, Fernanda G.; de Mesquita, João P.

    2016-05-01

    The oxygenated functional groups present on the surface of carbon dots with an average size of 2.7 ± 0.5 nm were characterized by a variety of techniques. In particular, we discussed the fit data of potentiometric titration curves using a nonlinear regression method based on the Levenberg-Marquardt algorithm. The results obtained by statistical treatment of the titration curve data showed that the best fit was obtained considering the presence of five Brønsted-Lowry acids on the surface of the carbon dots with constant ionization characteristics of carboxylic acids, cyclic ester, phenolic and pyrone-like groups. The total number of oxygenated acid groups obtained was 5 mmol g-1, with approximately 65% (∼2.9 mmol g-1) originating from groups with pKa < 6. The methodology showed good reproducibility and stability with standard deviations below 5%. The nature of the groups was independent of small variations in experimental conditions, i.e. the mass of carbon dots titrated and initial concentration of HCl solution. Finally, we believe that the methodology used here, together with other characterization techniques, is a simple, fast and powerful tool to characterize the complex acid-base properties of these so interesting and intriguing nanoparticles.

  15. Selective two-step titration of thorium by sulfate displacement of the diethylenetriaminepentaacetic acid complex

    SciTech Connect

    Kiefer, P.

    1980-07-01

    Thorium and other metals are complexed with excess diethylenetriaminepentaacetic acid (DTPA) at pH 1.4, the excess DTPA is titrated with Bi(III) to a xylenol orange end point, sulfate is added to complex Th(IV), and the displaced DTPA again is titrated with Bi(III). Of 61 metal ions and nonmetal anions tested, only Ga(III), Sc(III), tungstate, citrate, oxalate, and thiosulfate interfere seriously. Lesser interferences are In(III), Zr(IV), V(IV), and permanganate. The standard deviation is 2 ..mu..g for 56 to 840 ..mu..g Th.

  16. Comparison of HPLC, UV spectrophotometry and potentiometric titration methods for the determination of lumefantrine in pharmaceutical products.

    PubMed

    da Costa César, Isabela; Nogueira, Fernando Henrique Andrade; Pianetti, Gérson Antônio

    2008-09-10

    This paper describes the development and evaluation of a HPLC, UV spectrophotometry and potentiometric titration methods to quantify lumefantrine in raw materials and tablets. HPLC analyses were carried out using a Symmetry C(18) column and a mobile phase composed of methanol and 0.05% trifluoroacetic acid (80:20), with a flow rate of 1.0ml/min and UV detection at 335nm. For the spectrophotometric analyses, methanol was used as solvent and the wavelength of 335nm was selected for the detection. Non-aqueous titration of lumefantrine was carried out using perchloric acid as titrant and glacial acetic acid/acetic anhydride as solvent. The end point was potentiometrically determined. The three evaluated methods showed to be adequate to quantify lumefantrine in raw materials, while HPLC and UV methods presented the most reliable results for the analyses of tablets. PMID:18571353

  17. An automatic system for acidity determination based on sequential injection titration and the monosegmented flow approach.

    PubMed

    Kozak, Joanna; Wójtowicz, Marzena; Gawenda, Nadzieja; Kościelniak, Paweł

    2011-06-15

    An automatic sequential injection system, combining monosegmented flow analysis, sequential injection analysis and sequential injection titration is proposed for acidity determination. The system enables controllable sample dilution and generation of standards of required concentration in a monosegmented sequential injection manner, sequential injection titration of the prepared solutions, data collecting, and handling. It has been tested on spectrophotometric determination of acetic, citric and phosphoric acids with sodium hydroxide used as a titrant and phenolphthalein or thymolphthalein (in the case of phosphoric acid determination) as indicators. Accuracy better than |4.4|% (RE) and repeatability better than 2.9% (RSD) have been obtained. It has been applied to the determination of total acidity in vinegars and various soft drinks. The system provides low sample (less than 0.3 mL) consumption. On average, analysis of a sample takes several minutes. PMID:21641455

  18. A novel method for the determination of the degree of deacetylation of chitosan by coulometric titration.

    PubMed

    Wang, Chao; Yuan, Fang; Pan, Jiabao; Jiao, Shining; Jin, Ling; Cai, Hongwei

    2014-09-01

    A novel method to determine the degree of deacetylation of chitosan is described. In this method, the coulometric titrant OH- is generated by the electrolysis of water. The OH- reacted with the residual hydrochloric acid in chitosan solution and the degree of deacetylation was obtained by Faraday's law. The optimized experimental parameters in this study were 1.0 mol/L KCl as supporting electrolyte, 15.00 mA as the intensity of constant current, composite glass electrode as indicating electrode couples, double platinum generated electrode-platinum wire auxiliary electrode as working electrode pairs, pH 3.80 as the titration end-point. The degree of deacetylation in the four samples, which varied from 70 to 95% were measured. The results were similar to those from 1H NMR and the standard deviations were lower than 0.5%. With merit of simplicity, convenience, quickness, high accuracy and precision, automatic detection of titration end-point and low-cost, the proposed method will be very useful in the industrial production. PMID:25020083

  19. A numerical method of finding potentiometric titration end-points by use of approximative spline functions.

    PubMed

    Ren, K

    1990-07-01

    A new numerical method of determining potentiometric titration end-points is presented. It consists in calculating the coefficients of approximative spline functions describing the experimental data (e.m.f., volume of titrant added). The end-point (the inflection point of the curve) is determined by calculating zero points of the second derivative of the approximative spline function. This spline function, unlike rational spline functions, is free from oscillations and its course is largely independent of random errors in e.m.f. measurements. The proposed method is useful for direct analysis of titration data and especially as a basis for construction of microcomputer-controlled automatic titrators. PMID:18964999

  20. Comparison of methods for accurate end-point detection of potentiometric titrations

    NASA Astrophysics Data System (ADS)

    Villela, R. L. A.; Borges, P. P.; Vyskočil, L.

    2015-01-01

    Detection of the end point in potentiometric titrations has wide application on experiments that demand very low measurement uncertainties mainly for certifying reference materials. Simulations of experimental coulometric titration data and consequential error analysis of the end-point values were conducted using a programming code. These simulations revealed that the Levenberg-Marquardt method is in general more accurate than the traditional second derivative technique used currently as end-point detection for potentiometric titrations. Performance of the methods will be compared and presented in this paper.

  1. Hydrogen-ion titrations of amino acids and proteins in solutions containing concentrated electrolyte

    SciTech Connect

    Fergg, F.; Kuehner, D.E.; Blanch, H.W.; Prausnitz, J.M.

    1994-12-01

    This report describes a first attempt to quantify the net charge as a function of solution pH for lysozyme and {alpha}-chymotrypsin at 0.1 M, 1.0 M and 3.0 M ionic strength, (IS). The calculations are based on the residue (titratable group) pK{sub a}`s in the amino-acid sequence of the protein. To determine these pK{sub a}`s, a simple theory was used which assumes that the pK{sub a}`s are independent from each other in the protein and are equal to their pK{sub a} values in free amino-acid solution (Independent-Site Theory, IST). Residue pK{sub a}`s were obtained from amino-acid hydrogen-ion titrations at three different KCl concentrations corresponding to 0.1M, 1.0M and 3.0M ionic strength. After construction of a suitable apparatus, the experimental procedure and data reduction were computerized to perform a large number of titrations. Most measured pK{sub a}`s showed high reproducibility (the difference of pK{sub a} values observed between two experiments was less than 0.05). For IS = 0.1M, observed pK{sub a}`s agreed with literature values to within a few hundredths of a pH unit. Furthermore, the ionic-strength dependence of the pK{sub a}`s followed the trends reported in the literature, viz. pK{sub a} values decrease with increasing ionic strength until they reach a minimum at about IS = 0.5M. At still higher IS, pK{sub a}`s increase as the ionic strength rises to 3M. The known pK{sub a}`s of all titratable groups in a protein were used with the IST to give a first approximation of how the protein net charge varies with pH at high ionic strength. A comparison of the titration curves based on the IST with experimental lysozyme and {alpha}-chymotrypsin titration data indicates acceptable agreement at IS = 0.1M. However, comparison of measured and calculated titration curves at IS = 1M and IS = 3M indicates only quantitative agreement.

  2. Titration Techniques

    NASA Astrophysics Data System (ADS)

    Jacobsen, Jerrold J.; Houston Jetzer, Kelly; Patani, Néha; Zimmerman, John; Zweerink, Gerald

    1995-07-01

    Significant attention is paid to the proper technique for reading a meniscus. Video shows meniscus-viewing techniques for colorless and dark liquids and the consequences of not reading a meniscus at eye level. Lessons are provided on approaching the end point, focusing on end point colors produced via different commonly used indicators. The concept of a titration curve is illustrated by means of a pH meter. Carefully recorded images of the entire range of meniscus values in a buret, pipet, and graduated cylinder are included so that you can show your students, in lecture or pre-lab discussion, any meniscus and discuss how to read the buret properly. These buret meniscus values are very carefully recorded at the rate of one video frame per hundredth of a milliliter, so that an image showing any given meniscus value can be obtained. These images can be easily incorporated into a computer-based multimedia environment for testing or meniscus-reading exercises. Two of the authors have used this technique and found the exercise to be very well received by their students. Video on side two shows nearly 100 "bloopers", demonstrating both the right way and wrong ways to do tasks associated with titration. This material can be used in a variety of situations: to show students the correct way to do something; to test students by asking them "What is this person doing wrong?"; or to develop multimedia, computer-based lessons. The contents of Titration Techniques are listed below: Side 1 Titration: what it is. A simple titration; Acid-base titration animation; A brief redox titration; Redox titration animation; A complete acid-base titration. Titration techniques. Hand technique variations; Stopcock; Using a buret to measure liquid volumes; Wait before reading meniscus; Dirty and clean burets; Read meniscus at eye level (see Fig. 1); Meniscus viewing techniques--light colored liquids; Meniscus viewing techniques--dark liquids; Using a magnetic stirrer; Rough titration

  3. Effect of temperature on the acid-base properties of the alumina surface: microcalorimetry and acid-base titration experiments.

    PubMed

    Morel, Jean-Pierre; Marmier, Nicolas; Hurel, Charlotte; Morel-Desrosiers, Nicole

    2006-06-15

    Sorption reactions on natural or synthetic materials that can attenuate the migration of pollutants in the geosphere could be affected by temperature variations. Nevertheless, most of the theoretical models describing sorption reactions are at 25 degrees C. To check these models at different temperatures, experimental data such as the enthalpies of sorption are thus required. Highly sensitive microcalorimeters can now be used to determine the heat effects accompanying the sorption of radionuclides on oxide-water interfaces, but enthalpies of sorption cannot be extracted from microcalorimetric data without a clear knowledge of the thermodynamics of protonation and deprotonation of the oxide surface. However, the values reported in the literature show large discrepancies and one must conclude that, amazingly, this fundamental problem of proton binding is not yet resolved. We have thus undertaken to measure by titration microcalorimetry the heat effects accompanying proton exchange at the alumina-water interface at 25 degrees C. Based on (i) the surface sites speciation provided by a surface complexation model (built from acid-base titrations at 25 degrees C) and (ii) results of the microcalorimetric experiments, calculations have been made to extract the enthalpic variations associated respectively to first and second deprotonation of the alumina surface. Values obtained are deltaH1 = 80+/-10 kJ mol(-1) and deltaH2 = 5+/-3 kJ mol(-1). In a second step, these enthalpy values were used to calculate the alumina surface acidity constants at 50 degrees C via the van't Hoff equation. Then a theoretical titration curve at 50 degrees C was calculated and compared to the experimental alumina surface titration curve. Good agreement between the predicted acid-base titration curve and the experimental one was observed. PMID:16504204

  4. A combination of synchronous fluorescence spectroscopy with chemometric treatment and internal standards in non-aqueous potentiometric titrations of fulvic acids.

    PubMed

    Esteves da Silva, J C; Machado, A A

    1994-12-01

    The acid properties of a soil fulvic acid (sfua) were characterized by potentiometric titration with tetrabutylammonium hydroxide in two non-aqueous solvents with high acid-base resolution power N,N-dimethylformamide (DMF) and acetonitrile. Synchronous fluorescence spectroscopy (SyF) was also used to monitor directly the sfua status during the potentiometric titration in DMF. The potentiometric titration curves showed no clear end-point and the analysis of the sets of spectra obtained at increasing neutralization degree, with a self-modeling curve resolution method (SIMPLISMA), revealed the existence of two components with featureless concentration profiles. Internal standards (maleic, salicylic and p-hydroxylbenzoic acids) were used to determine the amounts of acid groups with different acid strengths in the two non-aqueous solvents. It was shown that the variations observed in the SyF spectra sets of the internal standards are not correlated with those observed in the sfua data. The splitting of the sfua groups in the non-aqueous titration curves seems to be forced artificially depending on the standards used. PMID:18966177

  5. Quantitative analysis of citric acid/sodium hypophosphite modified cotton by HPLC and conductometric titration.

    PubMed

    Ye, Tao; Wang, Bijia; Liu, Jian; Chen, Jiangang; Yang, Yiqi

    2015-05-01

    Isocratic HPLC was used in conjunction with conductometric titration to quantitatively examine the modification of cotton cellulose by citric acid (CA)/sodium hypophosphite (SHP). CA/SHP had been extensively used as a green crosslinking agent for enhancement of cellulose and other carbohydrate polymers without in-depth understanding of the mechanisms. The current study investigated all identifiable secondary polycarboxylic acids from CA decomposition in the CA/SHP-cellulose system under various curing conditions. It was found that CA decomposition was more sensitive to temperature compared with the desirable esterification reaction. Two crosslinking mechanisms, namely ester crosslinking and SHP crosslinking were responsible for the observed improvement in crease resistance of CA/SHP treated cotton fabrics. An oligomer of citraconic acid (CCA) and/or itaconic acid (IA) was identified as a possible contributor to fabric yellowing. Finally, the crease resistance of fabrics correlated strongly with CA preservation in polyol-added CA/SHP crosslinking systems. The dosage of polyol should be held below an inflexion point to keep the undesirable competition against cellulose minimum. The combination of HPLC and conductometric titration was demonstrated to be useful in studying the CA/SHP-cellulose crosslinking system. The findings have implications for better application of CA/SHP in polysaccharide modifications in general. PMID:25659676

  6. Tested Demonstrations: Comparison of Strong Acid and Weak Acid Titration Curves.

    ERIC Educational Resources Information Center

    Gilbert, George L., Ed.

    1979-01-01

    A lecture demonstration is presented for comparing titration curves. A plot of pH vs volume of strong base is produced by connecting the external output of a pH meter to a strip recorder. Thus, pH is recorded as a function of time. (BB)

  7. Studies on the acidity of mordenite and ZSM-5. 1. Determination of Broensted acid site concentrations in mordenite and ZSM-5 by conductometric titration

    SciTech Connect

    Crocker, M.; Herold, R.H.M.; Sonnemans, M.H.W.; Emeis, C.A.; Wilson, A.E.; Moolen, J.N. van der )

    1993-01-14

    The Broensted acidity of H-mordenite and H-ZSM-5 samples of varying proton concentration has been studied using aqueous conductometric titration, IR spectroscopy, and aqueous potentiometric titration. Good agreement is observed between Broensted acid site concentrations determined by conductometric titration and IR measurements, while indirect potentiometric titration affords acid site concentrations consistently lower than those measured using the conductometric technique. This finding is rationalized on the basis that, in a conductometric titration, all the accessible Broensted acid sites are direct;y titrated, whereas in the potentiometric procedure utilized, only those protons which can be ion-exchanged out of the zeolite are titrated. After allowing for the presence of extraframework aluminum in the zeolites (determined by [sup 27]Al NMR), the measured acidity for H-mordenite is found to increase linearly with increasing Al content within the range 0-1.5 mmol Al/g but appears to reach a limiting value at higher Al concentrations. For H-ZSM-5, the experimentally determined number of Broensted acid sites is also found to be linearly dependent on the Al molar fraction within the range measured (0-1.20 mmol Al/g). For both series of zeolite samples, the measured acidity is generally found to be less than the theoretical maximum calculated on the basis of an H[sup +]/Al ratio of 1. 43 refs., 10 figs., 4 tabs.

  8. A Universal Method for Fishing Target Proteins from Mixtures of Biomolecules using Isothermal Titration Calorimetry

    SciTech Connect

    Zhou, X.; Sun, Q; Kini, R; Sivaraman, J

    2008-01-01

    The most challenging tasks in biology include the identification of (1) the orphan receptor for a ligand, (2) the ligand for an orphan receptor protein, and (3) the target protein(s) for a given drug or a lead compound that are critical for the pharmacological or side effects. At present, several approaches are available, including cell- or animal-based assays, affinity labeling, solid-phase binding assays, surface plasmon resonance, and nuclear magnetic resonance. Most of these techniques are not easy to apply when the target protein is unknown and the compound is not amenable to labeling, chemical modification, or immobilization. Here we demonstrate a new universal method for fishing orphan target proteins from a complex mixture of biomolecules using isothermal titration calorimetry (ITC) as a tracking tool. We took snake venom, a crude mixture of several hundred proteins/peptides, as a model to demonstrate our proposed ITC method in tracking the isolation and purification of two distinct target proteins, a major component and a minor component. Identities of fished out target proteins were confirmed by amino acid sequencing and inhibition assays. This method has the potential to make a significant advancement in the area of identifying orphan target proteins and inhibitor screening in drug discovery and characterization.

  9. MOISTURE IN COTTON BY THE KARL FISCHER TITRATION REFERENCE METHOD

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Moisture is a critical parameter that influences many aspects of cotton fiber from harvesting and ginning to various fiber properties. Because of their importance, reference moisture methods that are more accurate than the existing oven-drying techniques and relatively easy to generate results are ...

  10. The active titration method for measuring local hydroxyl radical concentration

    NASA Technical Reports Server (NTRS)

    Sprengnether, Michele; Prinn, Ronald G.

    1994-01-01

    We are developing a method for measuring ambient OH by monitoring its rate of reaction with a chemical species. Our technique involves the local, instantaneous release of a mixture of saturated cyclic hydrocarbons (titrants) and perfluorocarbons (dispersants). These species must not normally be present in ambient air above the part per trillion concentration. We then track the mixture downwind using a real-time portable ECD tracer instrument. We collect air samples in canisters every few minutes for roughly one hour. We then return to the laboratory and analyze our air samples to determine the ratios of the titrant to dispersant concentrations. The trends in these ratios give us the ambient OH concentration from the relation: dlnR/dt = -k(OH). A successful measurement of OH requires that the trends in these ratios be measureable. We must not perturb ambient OH concentrations. The titrant to dispersant ratio must be spatially invariant. Finally, heterogeneous reactions of our titrant and dispersant species must be negligible relative to the titrant reaction with OH. We have conducted laboratory studies of our ability to measure the titrant to dispersant ratios as a function of concentration down to the few part per trillion concentration. We have subsequently used these results in a gaussian puff model to estimate our expected uncertainty in a field measurement of OH. Our results indicate that under a range of atmospheric conditions we expect to be able to measure OH with a sensitivity of 3x10(exp 5) cm(exp -3). In our most optimistic scenarios, we obtain a sensitivity of 1x10(exp 5) cm(exp -3). These sensitivity values reflect our anticipated ability to measure the ratio trends. However, because we are also using a rate constant to obtain our (OH) from this ratio trend, our accuracy cannot be better than that of the rate constant, which we expect to be about 20 percent.

  11. Canadian Tire Money: An Analogy for Use When Discussing Weak Acid Strong Base Titrations

    NASA Astrophysics Data System (ADS)

    Last, Arthur M.

    2003-12-01

    A simple analogy can often provide an instructor with a means of helping students to understand an unfamiliar concept. An analogy involving money can be particularly helpful as most students have experience in dealing with a range of financial transactions in their everyday lives. In this article, use is made of the practice of one well-known Canadian retail chain in returning to its customers a small percentage of an item's purchase price in the form of imitation bank notes that can subsequently be spent in the chain's stores. An analogy is drawn between this practice and the determination of the pKa of a weak acid by titrating it with a strong base, taking into account the hydrolysis of the anion produced.

  12. Semi-automatic version of the potentiometric titration method for characterization of uranium compounds.

    PubMed

    Cristiano, Bárbara F G; Delgado, José Ubiratan; da Silva, José Wanderley S; de Barros, Pedro D; de Araújo, Radier M S; Dias, Fábio C; Lopes, Ricardo T

    2012-09-01

    The potentiometric titration method was used for characterization of uranium compounds to be applied in intercomparison programs. The method is applied with traceability assured using a potassium dichromate primary standard. A semi-automatic version was developed to reduce the analysis time and the operator variation. The standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization and compatible with those obtained by manual techniques. PMID:22406220

  13. The pH at the First Equivalence Point in the Titration of a Diprotic Acid

    NASA Astrophysics Data System (ADS)

    Ault, Addison

    2003-12-01

    Some readers will note a similarity between this approach and the one I took in a paper entitled “Do pH in Your Head” (2). In an example in that article the isoelectric pH of glycine (the pH at which the average charge of a glycine molecule is zero), has the value of 6.0, which is exactly half-way between 2.4, the pKa of the carboxyl group of glycine, and 9.6, the pKa of the ammonium group of glycine. This is what one would expect when realizing that a solution of neutral glycine right out of the bottle is equivalent to glycine obtained by titration of the conjugate acid of glycine to the first equivalence point. Those who are interested might want to consider why the isoelectric pH of an “acidic” amino acid, such as alanine, is exactly half-way between the pKa values of the two carboxyl groups, and why the isoelectric pH of a “basic” amino acid such as lysine is exactly half-way between the pKa values of the two ammonium groups.

  14. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  15. Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Luo, Wensui; Spalding, Brian Patrick; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-01-01

    Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.

  16. Kinetic properties of two Rhizopus exo-polygalacturonase enzymes hydrolyzing galacturonic acid oligomers using isothermal titration calorimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The kinetic characteristics of two Rhizopus oryzae exo-polygalacturonases acting on galacturonic acid oligomers (GalpA) were determined using isothermal titration calorimetry (ITC). RPG15 hydrolyzing (GalpA)2 demonstrated a Km of 55 uM and kcat of 10.3 s^-1^ while RPG16 was shown to have greater af...

  17. Assembling and Using an LED-Based Detector to Monitor Absorbance Changes during Acid-Base Titrations

    ERIC Educational Resources Information Center

    Santos, Willy G.; Cavalheiro, E´der T. G.

    2015-01-01

    A simple photometric assembly based in an LED as a light source and a photodiode as a detector is proposed in order to follow the absorbance changes as a function of the titrant volume added during the course of acid-base titrations in the presence of a suitable visual indicator. The simplicity and low cost of the electronic device allow the…

  18. Amperometric, Bipotentiometric, and Coulometric Titration.

    ERIC Educational Resources Information Center

    Stock, John T.

    1984-01-01

    Reviews literature on amperometric, bipotentiometric, and coulometric titration methods examining: apparatus and methodology; acid-base reactions; precipitation and complexing reactions (considering methods involving silver, mercury, EDTA or analogous reagents, and other organic compounds); and oxidation-reduction reactions (considering methods…

  19. Flow cytometry as an improved method for the titration of Chlamydiaceae and other intracellular bacteria.

    PubMed

    Käser, T; Pasternak, J A; Hamonic, G; Rieder, M; Lai, K; Delgado-Ortega, M; Gerdts, V; Meurens, F

    2016-05-01

    Chlamydiaceae is a family of intracellular bacteria causing a range of diverse pathological outcomes. The most devastating human diseases are ocular infections with C. trachomatis leading to blindness and genital infections causing pelvic inflammatory disease with long-term sequelae including infertility and chronic pelvic pain. In order to enable the comparison of experiments between laboratories investigating host-chlamydia interactions, the infectious titer has to be determined. Titer determination of chlamydia is most commonly performed via microscopy of host cells infected with a serial dilution of chlamydia. However, other methods including fluorescent ELISpot (Fluorospot) and DNA Chip Scanning Technology have also been proposed to enumerate chlamydia-infected cells. For viruses, flow cytometry has been suggested as a superior alternative to standard titration methods. In this study we compared the use of flow cytometry with microscopy and Fluorospot for the titration of C. suis as a representative of other intracellular bacteria. Titer determination via Fluorospot was unreliable, while titration via microscopy led to a linear read-out range of 16 - 64 dilutions and moderate reproducibility with acceptable standard deviations within and between investigators. In contrast, flow cytometry had a vast linear read-out range of 1,024 dilutions and the lowest standard deviations given a basic training in these methods. In addition, flow cytometry was faster and material costs were lower compared to microscopy. Flow cytometry offers a fast, cheap, precise, and reproducible alternative for the titration of intracellular bacteria like C. suis. © 2016 International Society for Advancement of Cytometry. PMID:26849001

  20. Utilizing the virus-induced blocking of apoptosis in an easy baculovirus titration method

    PubMed Central

    Niarchos, Athanasios; Lagoumintzis, George; Poulas, Konstantinos

    2015-01-01

    Baculovirus-mediated protein expression is a robust experimental technique for producing recombinant higher-eukaryotic proteins because it combines high yields with considerable post-translational modification capabilities. In this expression system, the determination of the titer of recombinant baculovirus stocks is important to achieve the correct multiplicity of infection for effective amplification of the virus and high expression of the target protein. To overcome the drawbacks of existing titration methods (e.g., plaque assay, real-time PCR), we present a simple and reliable assay that uses the ability of baculoviruses to block apoptosis in their host cells to accurately titrate virus samples. Briefly, after incubation with serial dilutions of baculovirus samples, Sf9 cells were UV irradiated and, after apoptosis induction, they were viewed via microscopy; the presence of cluster(s) of infected cells as islets indicated blocked apoptosis. Subsequently, baculovirus titers were calculated through the determination of the 50% endpoint dilution. The method is simple, inexpensive, and does not require unique laboratory equipment, consumables or expertise; moreover, it is versatile enough to be adapted for the titration of every virus species that can block apoptosis in any culturable host cells which undergo apoptosis under specific conditions. PMID:26490731

  1. Estimating iron and aluminum content of acid mine discharge from a north-central Pennsylvania coal field by use of acidity titration curves

    USGS Publications Warehouse

    Ott, A.N.

    1986-01-01

    Determination of acidity provides a value that denotes the quantitative capacity of the sample water to neutralize a strong base to a particular pH. However, much additional information can be obtained from this determination if a titration curve is constructed from recorded data of titrant increments and their corresponding pH values. The curve can be used to identify buffer capabilities, the acidity with respect to any pH value within the curve limit, and, in the case of acid mine drainage from north-central Pennsylvania, the identification and estimation of the concentration of dissolved ferrous iron, ferric iron, and aluminum. Through use of titration curves, a relationship was observed for the acid mine drainage between: (1) the titratable acidity (as milligrams per liter calcium carbonate) to pH 4.0 and the concentration of dissolved ferric iron; and (2) the titratable acidity (as milligrams per liter calcium carbonate) from pH 4.0 to 5.0 and the concentration of dissolved aluminum. The presence of dissolved ferrous iron can be detected by the buffering effect exhibited in the area between pH 5.5 to 7.5. The concentration of ferrous iron is estimated by difference between the concentrations of ferric iron in an oxidized and unoxidized sample. Interferences in any of the titrations from manganese, magnesium, and aluminate, appear to be negligible within the pH range of interest.

  2. A new numerical method of finding potentiometric titration end-points by use of rational spline functions.

    PubMed

    Ren, K; Ren-Kurc, A

    1986-08-01

    A new numerical method of determining the position of the inflection point of a potentiometric titration curve is presented. It consists of describing the experimental data (emf, volume data-points) by means of a rational spline function. The co-ordinates of the titration end-point are determined by analysis of the first and second derivatives of the spline function formed. The method also allows analysis of distorted titration curves which cannot be interpreted by Gran's or other computational methods. PMID:18964159

  3. The generalized lewis acid-base titration of palladium and niobium

    NASA Astrophysics Data System (ADS)

    Cima, M.; Brewer, L.

    1988-12-01

    The high thermodynamic stability of alloys composed of platinum group metals and group IVB and VB metals has been explained by an electronic interaction analogous to the Lewis acid-base concept for nontransition elements. The analogy is further demonstrated by the titration of palladium by addition of niobium. The activity of niobium in solid palladium was measured as a function of concentration by solid-state galvanic cells and study of the ternary oxide phase diagram. The galvanic cells were of the type Pt/NbO2,Nb2O4.8/YDTJNbOy,Nbpd/Pt where the solid electrolyte is yttria-doped thoria (YDT). Ternary phase diagrams for the Pd-Nb-0 and Rh-Nb-0 systems were obtained by characterizing samples equilibrated at 1000 °C. The phase relationships found in the ternary diagrams were also used to derive thermochemical data for the alloys. Thermochemical quantities for other acid-base stabilized alloys such as Nb-Rh, Ti-Pd, and Ti-Rh were also measured. The excess partial molar ΔGxs/R of niobium at infinite dilution was determined to be -31 kilo-Kelvin at 1000 °C, and the AG°JR of formation of a mole of NbPd3.55 is —21 kilo-Kelvin. These results and those for the other systems are used to assess the importance of valence electron configuration, nuclear charge, and crystal field effects in the context of generalized Lewis acid-base theory. It is concluded that both the nuclear charge of the atom and crystal field splitting of the valence orbitals significantly affect the basicity of the platinum group metals.

  4. Electrostatic calculations of amino acid titration and electron transfer, Q-AQB-->QAQ-B, in the reaction center.

    PubMed Central

    Beroza, P; Fredkin, D R; Okamura, M Y; Feher, G

    1995-01-01

    The titration of amino acids and the energetics of electron transfer from the primary electron acceptor (QA) to the secondary electron acceptor (QB) in the photosynthetic reaction center of Rhodobacter sphaeroides are calculated using a continuum electrostatic model. Strong electrostatic interactions between titrating sites give rise to complex titration curves. Glu L212 is calculated to have an anomalously broad titration curve, which explains the seemingly contradictory experimental results concerning its pKa. The electrostatic field following electron transfer shifts the average protonation of amino acids near the quinones. The pH dependence of the free energy between Q-AQB and QAQ-B calculated from these shifts is in good agreement with experiment. However, the calculated absolute free energy difference is in severe disagreement (by approximately 230 meV) with the observed experimental value, i.e., electron transfer from Q-A to QB is calculated to be unfavorable. The large stabilization energy of the Q-A state arises from the predominantly positively charged residues in the vicinity of QA in contrast to the predominantly negatively charged residues near QB. The discrepancy between calculated and experimental values for delta G(Q-AQB-->QAQ-B) points to limitations of the continuum electrostatic model. Inclusion of other contributions to the energetics (e.g., protein motion following quinone reduction) that may improve the agreement between theory and experiment are discussed. PMID:7647231

  5. Improving the prediction ability of FT-MIR spectroscopy to assess titratable acidity in cow's milk.

    PubMed

    Calamari, Luigi; Gobbi, Laura; Bani, Paolo

    2016-02-01

    This study investigated the potential application of Fourier transform mid-infrared spectroscopy (FT-MIR) for the determination of titratable acidity (TA) in cow's milk. The prediction model was developed on 201 samples collected from cows in early and late lactation, and was successively used to predict TA on samples collected from cows in early lactation and in samples with high somatic cell count. The root mean square error of cross-validation of the model by using external validation dataset was 0.09 °Soxhlet-Henkel/50 mL. Applying the model on milk samples from cows in early lactation or with high somatic cell count, the root mean square error of prediction was 0.163 °Soxhlet-Henkel/50 mL, with a RER and RPD of 23.9 and 5.1, respectively. Our results seem to indicate that FT-MIR can be used in individual milk samples to accurately predict TA, and has the potential to be adopted to measure routinely the TA of milk. PMID:26304375

  6. Prediction of uranium and technetium sorption during titration of contaminated acidic groundwater

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Watson, David B; Jardine, Philip M; Gu, Baohua

    2010-01-01

    This study investigates uranium and technetium sorption onto aluminum and iron hydroxides during titration of acidic groundwater. The contaminated groundwater exhibits oxic conditions with high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U, Tc, and various metal cations. More than 90% of U and Tc was removed from the aqueous phase as Al and Fe precipitated above pH 5.5, but was partially resolublized at higher pH values. An equilibrium hydrolysis and precipitation reaction model adequately described variations in aqueous concentrations of metal cations. An anion exchange reaction model was incorporated to simulate sulfate, U and Tc sorption onto variably charged (pH-dependent) Al and Fe hydroxides. Modeling results indicate that competitive sorption/desorption on mixed mineral phases needs to be considered to adequately predict U and Tc mobility. The model could be useful for future studies of the speciation of U, Tc and co-existing ions during pre- and post-groundwater treatment practices.

  7. The relationship between turgor pressure and titratable acidity in mesophyll cells of intact leaves of a Crassulacean-acid-metabolism plant, Kalanchoe daigremontiana Hamet et Perr.

    PubMed

    Rygol, J; Winter, K; Zimmermann, U

    1987-12-01

    Day/night changes in turgor pressure (P) and titratable acidity content were investigated in the (Crassulacean-acid-metabolism (CAM) plant Kalanchoe daigremontiana. Measurements of P were made on individual mesophyll cells of intact attached leaves using the pressure-probe technique. Under conditions of high relative humidity, when transpiration rates were minimal, changes in P correlated well with changes in the level of titratable acidity. During the standard 12 h light/12 h dark cycle, maximum turgor pressure (0.15 MPa) occurred at the end of the dark period when the level of titratable acidity was highest (about 300 μeq H(+)·g(-1) fresh weight). A close relationship between P and titratable acidity was also seen in leaves exposed to perturbations of the standard light/dark cycle. (The dark period was either prolonged, or else only CO2-free air was supplied in this period). In plants deprived of irrigation for five weeks, diurnal changes in titratable acidity of the leaves were reduced (ΔH=160 μeq H(+)·g(-1) fresh weight) and P increased from essentially zero at the end of the light period to 0.02 MPa at the end of the dark period. Following more severe water stress (experiments were made on leaves which had been detached for five weeks), P was zero throughout day and night, yet small diurnal changes in titratable acidity were still measured. These findings are discussed in relation to a hypothesis by Lüttge et al. 1975 (Plant Physiol. 56,613-616) for the role of P in the regulation of acidification/de-acidification cycles of plants exhibiting CAM. PMID:24226067

  8. pH Titratable Superparamagnetic Iron Oxide for Improved Nanoparticle Accumulation in Acidic Tumor Microenvironments

    PubMed Central

    Crayton, Samuel H.; Tsourkas, Andrew

    2011-01-01

    A wide variety of nanoparticle platforms are being developed for the diagnosis and treatment of malignancy. While many of these are passively targeted or rely on receptor-ligand interactions, metabolically directed nanoparticles provide a complementary approach. It is known that both primary and secondary events in tumorigensis alter the metabolic profile of developing and metastatic cancers. One highly conserved metabolic phenotype is a state of up-regulated glycolysis and reduced use of oxidative phosphorylation, even when oxygen tension is not limiting. This metabolic shift, termed the Warburg effect, creates a “hostile” tumor microenvironment with increased levels of lactic acid and low extracellular pH. In order to exploit this phenomenon and improve the delivery of nanoparticle platforms to a wide variety of tumors, a pH-responsive iron oxide nanoparticle was designed. Specifically, glycol chitosan (GC), a water-soluble polymer with pH titratable charge, was conjugated to the surface of superparamagnetic iron oxide nanoparticles (SPIO) to generate a T2*-weighted MR contrast agent that responds to alterations in its surrounding pH. Compared to control nanoparticles that lack pH sensitivity, these GC-SPIO nanoparticles demonstrated potent pH-dependent cellular association and MR contrast in vitro. In murine tumor models GC-SPIO also generated robust T2*-weighted contrast, which correlated with increased delivery of the agent to the tumor site, measured quantitatively by inductively coupled plasma mass spectrometry. Importantly, the increased delivery of GC-SPIO nanoparticles cannot be solely attributed to the commonly observed enhanced permeability and retention effect, since these nanoparticles have similar physical properties and blood circulation times as control agents. PMID:22035454

  9. Drug-binding energetics of human α-1-acid glycoprotein assessed by isothermal titration calorimetry and molecular docking simulations

    PubMed Central

    Huang, Johnny X.; Cooper, Matthew A.; Baker, Mark A.; Azad, Mohammad A.K.; Nation, Roger L.; Li, Jian; Velkov, Tony

    2012-01-01

    This study utilizes sensitive, modern isothermal titration calorimetric (ITC) methods to characterize the microscopic thermodynamic parameters that drive the binding of basic drugs to α-1-acid glycoprotein (AGP) and thereby rationalize the thermodynamic data in relation to docking models and crystallographic structures of the drug-AGP complexes. The binding of basic compounds from the tricyclic antidepressant series, together with miaserine, chlorpromazine, disopyramide and cimetidine all displayed an exothermically driven binding interaction with AGP. The impact of protonation/deprotonation events, ionic strength, temperature and the individual selectivity of the A and F1*S AGP variants on drug-binding thermodynamics were characterized. A correlation plot of the thermodynamic parameters for all of the test compounds revealed enthalpy-entropy compensation is in effect. The exothermic binding energetics of the test compounds were driven by a combination of favorable (negative) enthalpic (ΔH°) and favorable (positive) entropic (ΔS°) contributions to the Gibbs free energy (ΔG°). Collectively, the data imply that the free energies that drive drug binding to AGP and its relationship to drug-serum residency evolve from the complex interplay of enthalpic and entropic forces from interactions with explicit combinations of hydrophobic and polar side-chain sub-domains within the multi-lobed AGP ligand binding cavity. PMID:23192962

  10. Titration of a Solid Acid Monitored by X-Ray Diffraction

    ERIC Educational Resources Information Center

    Dungey, Keenan E.; Epstein, Paul

    2007-01-01

    An experiment is described to introduce students to an important class of solid-state reactions while reinforcing concepts of titration by using a pH meter and a powder X-ray diffractometer. The experiment was successful in teaching students the abstract concepts of solid-state structure and diffraction by applying the diffraction concepts learned…

  11. A one-step colorimetric acid-base titration sensor using a complementary color changing coordination system.

    PubMed

    Cho, Hui Hun; Kim, Si Hyun; Heo, Jun Hyuk; Moon, Young Eel; Choi, Young Hun; Lim, Dong Cheol; Han, Kwon-Hoon; Lee, Jung Heon

    2016-06-21

    We report the development of a colorimetric sensor that allows for the quantitative measurement of the acid content via acid-base titration in a single-step. In order to create the sensor, we used a cobalt coordination system (Co-complex sensor) that changes from greenish blue colored Co(H2O)4(OH)2 to pink colored Co(H2O)6(2+) after neutralization. Greenish blue and pink are two complementary colors with a strong contrast. As a certain amount of acid is introduced to the Co-complex sensor, a portion of greenish blue colored Co(H2O)4(OH)2 changes to pink colored Co(H2O)6(2+), producing a different color. As the ratio of greenish blue and pink in the Co-complex sensor is determined by the amount of neutralization reaction occurring between Co(H2O)4(OH)2 and an acid, the sensor produced a spectrum of green, yellow green, brown, orange, and pink colors depending on the acid content. In contrast, the color change appeared only beyond the end point for normal acid-base titration. When we mixed this Co-complex sensor with different concentrations of citric acid, tartaric acid, and malic acid, three representative organic acids in fruits, we observed distinct color changes for each sample. This color change could also be observed in real fruit juice. When we treated the Co-complex sensor with real tangerine juice, it generated diverse colors depending on the concentration of citric acid in each sample. These results provide a new angle on simple but quantitative measurements of analytes for on-site usage in various applications, such as in food, farms, and the drug industry. PMID:27143645

  12. Natural monocrystalline pyrite as a sensor in non-aqueous solution Part I: Potentiometric titration of weak acids in, N,N-dimethylformamide, methylpyrrolidone and pyridine.

    PubMed

    Mihajlović, Lj V; Mihajlović, R P; Antonijević, M M; Vukanović, B V

    2004-11-15

    The possibility of applying natural monocrystaline pyrite as a sensor for the potentiometric titration of weak acids in N,N-dimethylformamide, methylpyrrolidone and pyridine was investigated. The potential of this electrode in N,N-dimethylformamide, methylpyrrolidone and pyridine exhibits a sub-Nernst dependence. In N,N-dimethylformamide the slope (mV/pH) is 39.0 and in methylpyrrolidone it is 45.0. The potential jumps at the titration end-point obtained in the titration of weak acids are higher than those obtained by the application of a glass electrode as the indicator electrode The potential in the course of the titration and at the titration end-point (TEP) are rapidly established. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be very suitable titrating agents for these titrations. The results obtained in the determination of the investigated weak acids deviate by 0.1-0.35% with respect to those obtained by using a glass electrode as the indicator electrode. PMID:18969684

  13. MODIFICATION OF THE IODIMETRIC TITRATION METHOD FOR THE DETERMINATION OF BROMIDE AND ITS APPLICATION TO MIXED DOMESTIC - INDUSTRIAL WASTE EFFLUENTS

    EPA Science Inventory

    The iodimetric titration method for the determination of bromide involves the observation of various color changes, making the method unsuitable for use with samples that are highly colored. A modification is described, which extends the usefulness of the method to highly colored...

  14. Application of flow injection gradient titration based on the standard addition and dilution procedure to the determination of total acidity in vinegars and soft drinks.

    PubMed

    Wójtowicz, Marzena; Kozak, Joanna; Górnacka, Dorota; Koscielniak, Pawel

    2008-12-01

    The proposed approach relies on successive dilution of a solution containing a sample with standard addition and on titration of the solutions obtained until receiving a signal lower than the signal measured for the sample alone. Equations are derived for subsequent dilution factors for the automatic flow injection system applied. The overall calibration strategy including the possibility of prediction of the number of required standard solutions and of positioning the sample signal within the calibration range is presented. The method has been tested on the spectrophotometric determination of hydrochloric acid at two concentration levels (0.193 and 1.21 mol L(-1)) with sodium hydroxide as titrant. The results of accuracy better than |3.9|% (RE) and repeatability better than 1.3% (RSD) were obtained. The method has been applied to the determination of total acidity in vinegars and soft drinks. The average time necessary to analyze one sample is about 10 min. PMID:19075470

  15. A protocol analysis of the influence of technology on students' actions, verbal commentary, and thought processes during the performance of acid-base titrations

    NASA Astrophysics Data System (ADS)

    Nakhleh, Mary B.; Krajcik, Joseph S.

    We investigated students' initial and final understanding of acid-base concepts and their concurrent thought processes and actions during the process of acid-base titrations. Here we report students' actions and thought processes while titrating. Different levels of information were presented by three technologies: chemical indicators, pH meters, and microcomputer-based laboratories. We speculated that the level of information would influence students' actions and thought processes, as expressed in verbal commentary. Data were collected from 14 secondary chemistry students. Each student used one technology to titrate a strong acid, a weak acid, and a polyprotic acid with a strong base. They verbalized their thoughts while titrating. Students then graphed pH versus volume of base and discussed the titration with the investigator. Verbal commentaries were coded and analyzed for patterns in actions and for frequency of statement categories. Drawings were analyzed for shape, scale, and direction; discussions were analyzed for understanding of acid-base neutralization. We found that the technology's level of information affected the focus of students' observations. The microcomputer group focused primarily on the graph; other groups exhibited multiple foci. We speculate the screen display functions as an auxiliary short-term memory. The discussion data also reveal that students held three main ideas about how acids and bases behave when mixed. Implications for instruction are discussed.

  16. Midpoint potentials of cytochromes in vesicles of anaerobically-grown Paracoccus denitrificans determined by the indirect coulometric titration method.

    PubMed

    Kula, T; Stellwagen, E; Szentirmay, R; Kuwana, T

    1981-02-12

    1. Multiplicity of redox components with spectral properties similar to b-type cytochromes was established in vesicles derived fro anaerobically-grown Paracoccus denitrificans. 2. Multiplicity of c-type cytochromes was not apparent either from low temperature spectroscopy or potentiometric titrations. 3. Cytochromes a + a3 and a component, only observable at liquid nitrogen temperature, with a spectral maximum at 582.5 nm were detected. 4. Redox cycling of electron transport components using the indirect coulometric titration method was a convenient means of pairing redox potentials and was reproducible in total absorbance changes, midpoint potentials and spectral maxima. PMID:7470501

  17. Reference test methods for total water in lint cotton by Karl Fischer Titration and low temperature distillation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In a study of comparability of total water contents (%) of conditioned cottons by Karl Fischer Titration (KFT) and Low Temperature Distillation (LTD) reference methods, we demonstrated a match of averaged results based on a large number of replications and weighing the test specimens at the same tim...

  18. Filtrates & Residues: Olfactory Titration.

    ERIC Educational Resources Information Center

    Wood, John T.; Eddy, Roberta M.

    1996-01-01

    Presents an experiment that uses a unique acid-base indicator--the odor of raw onion--to indicate the end point of the titration of sodium hydroxide with hydrochloric acid. Allows the student to detect the completion of the neutralization reaction by olfaction rather than sight. (JRH)

  19. Repeated dose titration versus age-based method in electroconvulsive therapy: a pilot study.

    PubMed

    Aten, Jan Jaap; Oudega, Mardien; van Exel, Eric; Stek, Max L; van Waarde, Jeroen A

    2015-06-01

    In electroconvulsive therapy (ECT), a dose titration method (DTM) was suggested to be more individualized and therefore more accurate than formula-based dosing methods. A repeated DTM (every sixth session and dose adjustment accordingly) was compared to an age-based method (ABM) regarding treatment characteristics, clinical outcome, and cognitive functioning after ECT. Thirty-nine unipolar depressed patients dosed using repeated DTM and 40 matched patients treated with ABM were compared. Montgomery-Åsberg Depression Rating Scale (MADRS) and Mini-Mental State Examination (MMSE) were assessed at baseline and at the end of the index course, as well as the total number of ECT sessions. Both groups were similar regarding age, sex, psychotic features, mean baseline MADRS, and median baseline MMSE. At the end of the index course, the two methods showed equal outcome (mean end MADRS, 11.6 ± 8.3 in DTM and 9.5 ± 7.6 in ABM (P = 0.26); median end MMSE, 28 (25-29) and 28 (25-29.8), respectively (P = 0.81). However, the median number of all ECT sessions differed 16 (11-22) in DTM versus 12 (10-14.8) in ABM; P = 0.02]. Using regression analysis, dosing method and age were independently associated with the total number of ECT sessions, with less sessions needed in ABM (P = 0.02) and in older patients (P = 0.001). In this comparative cohort study, ABM and DTM showed equal outcome for depression and cognition. However, the median ECT course duration in repeated DTM appeared longer. Additionally, higher age was associated with shorter ECT courses regardless of the dosing method. Further prospective studies are needed to confirm these findings. PMID:25804765

  20. Analysis of the sorption properties of different soils using water vapour adsorption and potentiometric titration methods

    NASA Astrophysics Data System (ADS)

    Skic, Kamil; Boguta, Patrycja; Sokołowska, Zofia

    2016-07-01

    Parameters of specific surface area as well as surface charge were used to determine and compare sorption properties of soils with different physicochemical characteristics. The gravimetric method was used to obtain water vapour isotherms and then specific surface areas, whereas surface charge was estimated from potentiometric titration curves. The specific surface area varied from 12.55 to 132.69 m2 g-1 for Haplic Cambisol and Mollic Gleysol soil, respectively, and generally decreased with pH (R=0.835; α = 0.05) and when bulk density (R=-0.736; α = 0.05) as well as ash content (R=-0.751; α = 0.05) increased. In the case of surface charge, the values ranged from 63.00 to 844.67 μmol g-1 Haplic Fluvisol and Mollic Gleysol, respecively. Organic matter gave significant contributions to the specific surface area and cation exchange capacity due to the large surface area and numerous surface functional groups, containing adsorption sites for water vapour molecules and for ions. The values of cation exchange capacity and specific surface area correlated linearly at the level of R=0.985; α = 0.05.

  1. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234... with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot... should be prepared in a hood. Store in a tightly stoppered container. 4. Preparation of 0.05M...

  2. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234... be precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the... barium chloride solution: Dissolve 12-13 g. barium chloride dihydrate in 1 liter of distilled water....

  3. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234... with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot... should be prepared in a hood. Store in a tightly stoppered container. 4. Preparation of 0.05M...

  4. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234... be precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the... barium chloride solution: Dissolve 12-13 g. barium chloride dihydrate in 1 liter of distilled water....

  5. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234... be precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the... barium chloride solution: Dissolve 12-13 g. barium chloride dihydrate in 1 liter of distilled water....

  6. Surface properties of bacillus subtilis determined by acid/base titrations, and the implications for metal adsorption in fluid-rock systems

    SciTech Connect

    Fein, J.B.; Davis, T.A.

    1996-10-01

    Bacteria are ubiquitous in low temperature aqueous systems, but quantifying their effects on aqueous mass transport remains a problem. Numerous studies have qualitatively examined the metal binding capacity of bacterial cell walls. However, quantitative thermodynamic modeling of metal-bacteria-mineral systems requires a detailed knowledge of the surface properties of the bacterial functional groups. In this study, we have conducted acid/base titrations of suspensions of B. subtilis, a common subsurface species whose surface properties are largely controlled by carboxyl groups. Titrations were conducted between pH 2 and 11 at several ionic strengths. The data are analyzed using a constant capacitance model to account for the surface electric field effects on the acidity constant. The pK{sub a} value that best fits the titration data is 3.9 {plus_minus} 0.3. This result represents the first step toward quantifying bacteria-metal and mineral-bacteria-metal interactions using equilibrium thermodynamics.

  7. Digital image-based titrations.

    PubMed

    Gaiao, Edvaldo da Nobrega; Martins, Valdomiro Lacerda; Lyra, Wellington da Silva; de Almeida, Luciano Farias; da Silva, Edvan Cirino; Araújo, Mário César Ugulino

    2006-06-16

    The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H3PO4 in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H3PO4, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection. PMID:17723410

  8. Microscale Titration in Schools Titration Competition.

    ERIC Educational Resources Information Center

    Clark, Michael J.

    1998-01-01

    Reviews the requirements of the National Titration Competition and describes how a team in a local competition used the technique. Compares microscale titration to conventional titration. Outlines the benefits of employing microscale techniques. (DDR)

  9. A comparison of the use of BrimA versus soluble solids/titratable acidity ratio as a maturity standard for navel oranges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maturity and time of harvest for California navel oranges is primarily determined by the ratio of the soluble solids concentration (SSC) to titratable acidity (TA). This standard has been used in the industry for decades but its usefulness and relationship to flavor have often been questioned. In re...

  10. Volumetric Titrations Using Electrolytically Generated Reagents for the Determination of Ascorbic Acid and Iron in Dietary Supplement Tablets: An Undergraduate Laboratory Experiment

    ERIC Educational Resources Information Center

    Scanlon, Christopher; Gebeyehu, Zewdu; Griffin, Kameron; Dabke, Rajeev B.

    2014-01-01

    An undergraduate laboratory experiment for the volumetric quantitative analysis of ascorbic acid and iron in dietary supplement tablets is presented. Powdered samples of the dietary supplement tablets were volumetrically titrated against electrolytically generated reagents, and the mass of dietary reagent in the tablet was determined from the…

  11. Determination of soluble solids content and titratable acidity of intact fruit and juice of Satsuma mandarin using a hand-held NIR instrument in transmittance mode

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determination of soluble solids content (SSC) and titratable acidity (TA) of intact fruit and juice of Satsuma mandarin was investigated using a hand-held NIR instrument “NIR-Gun” in transmittance mode. The resulting calibration equation measured SSC of intact fruit and juice with a standard error o...

  12. Automated Potentiometric Titrations in KCl/Water-Saturated Octanol: Method for Quantifying Factors Influencing Ion-Pair Partitioning

    PubMed Central

    2009-01-01

    The knowledge base of factors influencing ion pair partitioning is very sparse, primarily because of the difficulty in determining accurate log PI values of desirable low molecular weight (MW) reference compounds. We have developed a potentiometric titration procedure in KCl/water-saturated octanol that provides a link to log PI through the thermodynamic cycle of ionization and partitioning. These titrations have the advantage of being independent of the magnitude of log P, while maintaining a reproducibility of a few hundredths of a log P in the calculated difference between log P neutral and log P ion pair (diff (log PN − I)). Simple model compounds can be used. The titration procedure is described in detail, along with a program for calculating pKa′′ values incorporating the ionization of water in octanol. Hydrogen bonding and steric factors have a greater influence on ion pairs than they do on neutral species, yet these factors are missing from current programs used to calculate log PI and log D. In contrast to the common assumption that diff (log PN − I) is the same for all amines, they can actually vary more than 3 log units, as in our examples. A major factor affecting log PI is the ability of water and the counterion to approach the charge center. Bulky substituents near the charge center have a negative influence on log PI. On the other hand, hydrogen bonding groups near the charge center have the opposite effect by lowering the free energy of the ion pair. The use of this titration method to determine substituent ion pair stabilization values (IPS) should bring about more accurate log D calculations and encourage species-specific QSAR involving log DN and log DI. This work also brings attention to the fascinating world of nature’s highly stabilized ion pairs. PMID:19265385

  13. Kinetic characteristics of polygalacturonase enzymes hydrolyzing galacturonic acid oligomers using isothermal titration calorimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polygalacturonase enzymes hydrolyze the polygalacturonic acid chains found in pectin. Interest in polygalacturonase enzymes continues as they are useful in a number of industrial processes and conversely, detrimental, as they are involved in maceration of economically important crops. While a good...

  14. Titration and exchange studies of liver fatty acid-binding protein with 13C-labeled long-chain fatty acids.

    PubMed

    Wang, Hsin; He, Yan; Kroenke, Christopher D; Kodukula, Sarala; Storch, Judith; Palmer, Arthur G; Stark, Ruth E

    2002-04-30

    Uniformly (13)C-labeled long-chain fatty acids were used to probe ligand binding to rat liver fatty acid-binding protein (LFABP), an atypical member of the fatty acid-binding protein (FABP) family that binds more than one molecule of long-chain fatty acid, accommodates a variety of diverse ligands, and exhibits diffusion-mediated lipid transport to membranes. Two sets of (1)H-(13)C resonances were found in a titration series of NMR spectra for oleate-LFABP complexes, indicating that two molecules of the fatty acid are situated in the protein cavity. However, no distinct resonances were observed for the excess fatty acid in solution, suggesting that at least one ligand undergoes rapid exchange with oleate in the bulk solution. An exchange rate of 54 +/- 6 s(-1) between the two sets of resonances was measured directly using (13)C z,z-exchange spectroscopy. In light of these NMR measurements, possible molecular mechanisms for the ligand-exchange process are evaluated and implications for the anomalous fatty acid transport mechanism of LFABP are discussed. PMID:11969406

  15. Molecular Characterization of the Gas-Particle Interface of Soot Sampled from a Diesel Engine Using a Titration Method.

    PubMed

    Tapia, A; Salgado, M S; Martín, María Pilar; Lapuerta, M; Rodríguez-Fernández, J; Rossi, M J; Cabañas, B

    2016-03-15

    Surface functional groups of two different types of combustion aerosols, a conventional diesel (EN 590) and a hydrotreated vegetable oil (HVO) soot, have been investigated using heterogeneous chemistry (i.e., gas-particle surface reactions). A commercial sample of amorphous carbon (Printex XE2-B) was analyzed as a reference substrate. A Knudsen flow reactor was used to carry out the experiments under molecular flow conditions. The selected gases for the titration experiments were: N(CH3)3 for the identification of acidic sites, NH2OH for the presence of carbonyl groups, CF3COOH and HCl for basic sites of different strength, and O3 and NO2 for reducing groups. Reactivity with N(CH3)3 indicates a lower density of acidic functionalities for Printex XE2-B in relation to diesel and HVO soot. Results for NH2OH experiments indicates that commercial amorphous carbon exhibits a lower abundance of available carbonyl groups at the interface compared to the results from diesel and HVO soot, the latter being the one with the largest abundance of carbonyl functions. Reactions with acids indicate the presence of weak basic oxides on the particle surface that preferentially interact with the strong acid CF3COOH. Finally, reactions with O3 and NO2 reveal that diesel and especially HVO have a significantly higher reactivity with both oxidizers compared to that of Printex XE2-B because they have more reducing sites by roughly a factor of 10 and 30, respectively. The kinetics of titration reactions have also been investigated. PMID:26886850

  16. Colorblindness and Titrations with Visual Indicators.

    ERIC Educational Resources Information Center

    Diehl, Harvey; And Others

    1985-01-01

    Discusses various issues related to colorblind students performing titrations with visual indicators. Includes tables showing precisions in the titration of a weak acid by colorblind students using phenolphthalein and thymolphthalein and in the titration of a weak base by colorblind persons using methyl red and bromcresol green. (JN)

  17. Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like

    DOEpatents

    Smith, D.D.; Hiller, J.M.

    1998-02-24

    The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration. 1 fig.

  18. Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like

    DOEpatents

    Smith, Douglas D.; Hiller, John M.

    1998-01-01

    The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration.

  19. Modeling Precipitation and Sorption of Al, U and Co-contaminants during Titration of Acidic Sediments in Recirculation Flow-Through Experiments

    SciTech Connect

    Tang, Guoping; Luo, Wensui; Brooks, Scott C; Watson, David B; Gu, Baohua

    2013-01-01

    We conducted batch and recirculating column titration tests with contaminated acidic sediments with controlled CO2 in the headspace, and extended the geochemical model by Gu et al. (2003, GCA) to better understand and quantify the reactions governing trace metal fate in the subsurface. The sediment titration curve showed slow pH increase due to strong buffering by Al precipitation and CO2 uptake. Assuming precipitation of basaluminite at low saturation index (SI=-4), and decreasing cation exchange selectivity coefficient (kNa\\Al=0.3), the predictions are close to the observed pH and Al; and the model explains 1) the observed Ca, Mg, and Mn concentration decrease by cation exchange with sorbed Al, and 2) the decrease of U by surface complexation with Fe hydroxides at low pH, and precipitation as liebigite (Ca2UO2(CO3)3:10H2O) at pH>5.5. Without further adjustment geochemical parameters, the model describes reasonably well previous sediment and column titration tests without CO2 in the headspace, as well as the new large column test. The apparent inhibition of U and Ni decrease in the large column can be explained by formation of aqueous carbonate complexes and/or competition with carbonate for surface sites. These results indicated that ignoring labile solid phase Al would underestimate base requirement in titration of acidic aquifers.

  20. The use of graphite electrodes in potentiometric titrations

    SciTech Connect

    Selig, W.S.

    1987-04-01

    The use of various types of graphite as indicator electrodes in potentiometry has been limited to acid-base and redox titrations. We have expanded the range of feasible titrations to: (1) precipitation titrations; (2) acid-base titrations; (3) compleximetric titrations; and (4) redox titrations. Graphite covered with an organic membrane containing poly(vinyl chloride) (PVC) and a plasticizer is particularly useful in monitoring the endpoints of titrations in which insoluble ion-pairs are formed. The potentiometric titration of fluoride vs La(III) or Th(IV), or of sulfate vs Pb (II) or Ba(II), which can be monitored with a plain carbon rod, is discussed.

  1. Iodine losses during Winkler titrations

    NASA Astrophysics Data System (ADS)

    Knapp, George P.; Stalcup, Marvel C.; Stanley, Robert J.

    1991-01-01

    An experiment designed to measure iodine loss during the aliquot version of the Winkler titration for dissolved oxygen in seawater shows that 0.01-0.03 ml l -1 equivalent oxygen is lost at typical oceanic concentrations in the method presently used. A standardization technique, which mimics that employed during the titration of seawater samples, compensates for this iodine loss throughout the oceanic range. This result, contradicting an earlier report by GREEN and CARRITT (1966, Analyst, 91, 207-208), demonstrates that the whole-bottle method of oxygen titration is not to be preferred over the aliquot method.

  2. Tracer-monitored flow titrations.

    PubMed

    Sasaki, Milton K; Rocha, Diogo L; Rocha, Fábio R P; Zagatto, Elias A G

    2016-01-01

    The feasibility of implementing tracer-monitored titrations in a flow system is demonstrated. A dye tracer is used to estimate the instant sample and titrant volumetric fractions without the need for volume, mass or peak width measurements. The approach was applied to spectrophotometric flow titrations involving variations of sample and titrant flow-rates (i.e. triangle programmed technique) or concentration gradients established along the sample zone (i.e. flow injection system). Both strategies required simultaneous monitoring of two absorbing species, namely the titration indicator and the dye tracer. Mixing conditions were improved by placing a chamber with mechanical stirring in the analytical path aiming at to minimize diffusional effects. Unlike most of flow-based titrations, the innovation is considered as a true titration, as it does not require a calibration curve thus complying with IUPAC definition. As an application, acidity evaluation in vinegars involving titration with sodium hydroxide was selected. Phenolphthalein and brilliant blue FCF were used as indicator and dye tracer, respectively. Effects of sample volume, titrand/titrant concentrations and flow rates were investigated aiming at improved accuracy and precision. Results were reliable and in agreement with those obtained by a reference titration procedure. PMID:26703261

  3. Microbiological profiles, pH, and titratable acidity of chorizo and salchichón (two Spanish dry fermented sausages) manufactured with ostrich, deer, or pork meat.

    PubMed

    Capita, Rosa; Llorente-Marigómez, Sandra; Prieto, Miguel; Alonso-Calleja, Carlos

    2006-05-01

    Microbial counts, pH, and titratable acidity were determined in 102 Spanish dry fermented sausages (chorizo and salchichón) made with ostrich, deer, or pork meat. Average microbial counts (log CFU per gram) varied from 5.46 +/- 0.24 to 8.25 +/- 0.80 (total viable counts), from 4.79 +/- 0.36 to 7.99 +/- 0.20 (psychrotrophs), from 0.00 +/- 0.00 to 0.99 +/- 1.10 (undetectable values were assumed to be zero) (Enterobacteriaceae), from 0.00 +/- 0.00 to 4.27 +/- 1.47 (enterococci), from 5.15 +/- 1.15 to 8.46 +/- 0.49 (lactic acid bacteria), from 3.08 +/- 0.44 to 6.59 +/- 1.76 (Micrococcaceae), from 2.27 +/- 1.53 to 5.11 +/- 1.81 (molds and yeasts), from 0.00 +/- 0.00 to 2.25 +/- 0.81 (pseudomonads), and from 0.00 +/- 0.00 to 2.78 +/- 0.46 (Brochothrix thermosphacta). Average pH and titratable acidity varied from 5.07 +/- 0.25 to 5.63 +/- 0.51 (pH units) and from 0.30 +/- 0.01 to 0.86 +/- 0.19 (% lactic acid). Both type of sausage (P < 0.05) and species of meat (P < 0.001) influenced microbial counts. Salchich6n samples showed lower average values than chorizo samples for most microbial groups (significant for Enterobacteriaceae, lactic acid bacteria, and B. thermosphacta) and titratable acidity. Sausages made from pork showed the highest microbial loads for total viable counts, psychrotrophs, Enterobacteriaceae, enterococci, lactic acid bacteria, and yeasts and molds. Higher counts were observed only for pseudomonads in ostrich sausages. B. thermosphacta levels were similar for all species of meat. The highest average pH value was observed in sausages made from ostrich meat, and the lowest titratable acidity level was found in pork sausages. PMID:16715825

  4. Calcium-buffering effects of gluconate and nucleotides, as determined by a novel fluorimetric titration method

    PubMed Central

    Woehler, Andrew; Lin, Kun-Han; Neher, Erwin

    2014-01-01

    Significantly more Ca2+ influx is required for eliciting release of neurotransmitter during whole cell patch clamp recording in the Calyx of Held, when gluconate with 3 mm free ATP is used as pipette filling solution, as compared to a methanesulfonate-based solution with excess Mg2+. This reduction in efficiency of Ca2+ in eliciting release is due to low-affinity Ca2+ binding of both gluconate and ATP2− anions. To study these effects we developed a simple fluorimeteric titration procedure, which reports the dissociation constant, KD, of a given Ca2+ indicator dye, multiplied by 1 plus the sum of Ca2+ binding ratios of any anions, which act as low-affinity Ca2+ ligands. For solutions without Ca2+ binding anions we find KD values for Fura2FF ranging from 11.5 ± 1.7 to 15.6 ± 7.47 μm depending on the dominant anion used. For Fura6F and KCl-based solutions we find KD = 17.8 ± 1.3 μm. For solutions with gluconate as the main anion and for solutions that contain nucleotides, such as ATP and GTP, we find much higher values for the product. Assuming that the KD of the indicator dye is equal to that of KCl-based solutions we calculate the summed Ca2+ binding ratios and find a value of 3.55 for a solution containing 100 mm potassium gluconate and 4 mm ATP. Gluconate contributes a value of 1.75 to this number, while the contribution of ATP depends strongly on the presence of Mg2+ and varies from 0.8 (with excess Mg2+) to 13.8 (in the presence of 3 mm free ATP). Methanesulfonate has negligible Ca2+ binding capacity. These results explain the reduced efficiency of Ca2+ influx in the presence of gluconate or nucleotides, as these anions are expected to intercept Ca2+ ions at short distance. PMID:25194050

  5. Responses of grape berry anthocyanin and titratable acidity to the projected climate change across the Western Australian wine regions.

    PubMed

    Barnuud, Nyamdorj N; Zerihun, Ayalsew; Mpelasoka, Freddie; Gibberd, Mark; Bates, Bryson

    2014-08-01

    More than a century of observations has established that climate influences grape berry composition. Accordingly, the projected global climate change is expected to impact on grape berry composition although the magnitude and direction of impact at regional and subregional scales are not fully known. The aim of this study was to assess potential impacts of climate change on levels of berry anthocyanin and titratable acidity (TA) of the major grapevine varieties grown across all of the Western Australian (WA) wine regions. Grape berry anthocyanin and TA responses across all WA wine regions were projected for 2030, 2050 and 2070 by utilising empirical models that link these berry attributes and climate data downscaled (to ∼5 km resolution) from the csiro_mk3_5 and miroc3_2_medres global climate model outputs under IPCC SRES A2 emissions scenario. Due to the dependence of berry composition on maturity, climate impacts on anthocyanin and TA levels were assessed at a common maturity of 22 °Brix total soluble solids (TSS), which necessitated the determination of when this maturity will be reached for each variety, region and warming scenario, and future period. The results indicate that both anthocyanin and TA levels will be affected negatively by a warming climate, but the magnitude of the impacts will differ between varieties and wine regions. Compared to 1990 levels, median anthocyanins concentrations are projected to decrease, depending on global climate model, by up to 3-12 % and 9-33 % for the northern wine regions by 2030 and 2070, respectively while 2-18 % reductions are projected in the southern wine regions for the same time periods. Patterns of reductions in the median Shiraz berry anthocyanin concentrations are similar to that of Cabernet Sauvignon; however, the magnitude is lower (up to 9-18 % in southern and northern wine regions respectively by 2070). Similarly, uneven declines in TA levels are projected across the study regions. The largest reductions

  6. Responses of grape berry anthocyanin and titratable acidity to the projected climate change across the Western Australian wine regions

    NASA Astrophysics Data System (ADS)

    Barnuud, Nyamdorj N.; Zerihun, Ayalsew; Mpelasoka, Freddie; Gibberd, Mark; Bates, Bryson

    2014-08-01

    More than a century of observations has established that climate influences grape berry composition. Accordingly, the projected global climate change is expected to impact on grape berry composition although the magnitude and direction of impact at regional and subregional scales are not fully known. The aim of this study was to assess potential impacts of climate change on levels of berry anthocyanin and titratable acidity (TA) of the major grapevine varieties grown across all of the Western Australian (WA) wine regions. Grape berry anthocyanin and TA responses across all WA wine regions were projected for 2030, 2050 and 2070 by utilising empirical models that link these berry attributes and climate data downscaled (to ˜5 km resolution) from the csiro_mk3_5 and miroc3_2_medres global climate model outputs under IPCC SRES A2 emissions scenario. Due to the dependence of berry composition on maturity, climate impacts on anthocyanin and TA levels were assessed at a common maturity of 22 °Brix total soluble solids (TSS), which necessitated the determination of when this maturity will be reached for each variety, region and warming scenario, and future period. The results indicate that both anthocyanin and TA levels will be affected negatively by a warming climate, but the magnitude of the impacts will differ between varieties and wine regions. Compared to 1990 levels, median anthocyanins concentrations are projected to decrease, depending on global climate model, by up to 3-12 % and 9-33 % for the northern wine regions by 2030 and 2070, respectively while 2-18 % reductions are projected in the southern wine regions for the same time periods. Patterns of reductions in the median Shiraz berry anthocyanin concentrations are similar to that of Cabernet Sauvignon; however, the magnitude is lower (up to 9-18 % in southern and northern wine regions respectively by 2070). Similarly, uneven declines in TA levels are projected across the study regions. The largest reductions

  7. Comparison of methods for acid quantification: impact of resist components on acid-generating efficiency

    NASA Astrophysics Data System (ADS)

    Cameron, James F.; Fradkin, Leslie; Moore, Kathryn; Pohlers, Gerd

    2000-06-01

    Chemically amplified deep UV (CA-DUV) positive resists are the enabling materials for manufacture of devices at and below 0.18 micrometer design rules in the semiconductor industry. CA-DUV resists are typically based on a combination of an acid labile polymer and a photoacid generator (PAG). Upon UV exposure, a catalytic amount of a strong Bronsted acid is released and is subsequently used in a post-exposure bake step to deprotect the acid labile polymer. Deprotection transforms the acid labile polymer into a base soluble polymer and ultimately enables positive tone image development in dilute aqueous base. As CA-DUV resist systems continue to mature and are used in increasingly demanding situations, it is critical to develop a fundamental understanding of how robust these materials are. One of the most important factors to quantify is how much acid is photogenerated in these systems at key exposure doses. For the purpose of quantifying photoacid generation several methods have been devised. These include spectrophotometric methods, ion conductivity methods and most recently an acid-base type titration similar to the standard addition method. This paper compares many of these techniques. First, comparisons between the most commonly used acid sensitive dye, tetrabromophenol blue sodium salt (TBPB) and a less common acid sensitive dye, Rhodamine B base (RB) are made in several resist systems. Second, the novel acid-base type titration based on the standard addition method is compared to the spectrophotometric titration method. During these studies, the make up of the resist system is probed as follows: the photoacid generator and resist additives are varied to understand the impact of each of these resist components on the acid generation process.

  8. Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-01-01

    This study investigated sorption of uranium and technetium onto aluminum and iron hydroxides during titration of a contaminated groundwater using both Na hydroxide and carbonate as titrants. The contaminated groundwater has a low pH of 3.8 and high concentrations of NO3-, SO42-, Al, Ca, Mg, Mn, trace metals such as Ni and Co, and radionuclides such as U and Tc. During titration, most Al and Fe were precipitated out at pH above ~4.5. U as well as Tc was found to be removed from aqueous phase at pH below ~5.5, but to some extent released at higher pH values. An earlier geochemical equilibrium reaction path model that considered aqueous complexation and precipitation/dissolution reactions predicted mineral precipitation and adequately described concentration variations of Al, Fe and some other metal cations, but failed to predict sulfate, U and Tc concentrations during titration. Previous studies have shown that Fe- and Al-oxyhydroxides strongly sorb dissolved sulfate, U and Tc species. Therefore, an anion exchange model was developed for the sorption of sulfate, U and Tc onto Al and Fe hydroxides. With the additional consideration of the anion exchange reactions, concentration profiles of sulfate, U and Tc were more accurately predicted. Results of this study indicate that consideration of complex reactions such as sorption/desorption on mixed mineral phases, in addition to hydrolysis and precipitation, could improve the prediction of various contaminants during pre- and post-groundwater treatment practices.

  9. Cetylpyridinium tetrachlorozincate as standard for tenside titration. Analytical methods with 1,3-dibromo-5,5-dimethylhydantoin (DBH) in respect to environmental and economical concern, part 19.

    PubMed

    Hilp, M; Zembatova, S

    2004-08-01

    The determination of the cationic active disinfectants benzalkonium chloride, benzethonium chloride, cetrimide, and cetylpyridinium chloride according to PH. EUR. 2002 resp. supplement 4.3/2003 can be improved using the DBH-method. By application of column extraction the iodide determination can be performed in the organic layer by visual indication. However, titration in aqueous solution with sodium dodecyl sulphate as titrant and methyl orange resp. bromophenol blue as indicator can be performed more simple. Cetylpyridinium tetrachlorozincate is recommended as a standard for tenside titration. PMID:15378850

  10. A desk-computer program for calculation of the parameters of acid-base titration curves and protonation or metal-complex stability constants from potentiometric data.

    PubMed

    Gaizer, F; Puskás, A

    1981-08-01

    The program MINIPOT is designed to run on a desk-computer with 16-kbyte of memory. It can calculate the optimum values of the parameters of a blank acid-base titration in any solvent, and the protonation/deprotonation or overall stability constants of a maximum of four species with compositions H(q)L(p) or M(q)L(p) from potential, titrant volume and analytical concentration data. The program, written in BASIC, is based on the least-squares principle and is capable of simultaneous refinement of a maximum of four parameters. PMID:18962959

  11. Metal and metalloid indicator electrodes for the non-aqueous potentiometric titration of weak acids: comparative evaluation of group III, IV and V main-group elements.

    PubMed

    Greenhow, E J; Al-Mudarris, B F

    Indicator electrodes constructed from aluminium, gallium, indium, thallium, carbon, silicon, germanium, tin, lead, arsenic, antimony and bismuth have been evaluated for the potentiometric titration of solutions of benzoic acid in dimethylformamide and 4-methyl-2-pentanone. The aluminium, gallium, silicon and arsenic electrodes have also been evaluated for the determination of 3,5-xylenol in the same two solvents. Aluminium, gallium, indium, silicon, germanium, antimony and bismuth electrodes are superior to, or compare favourably with, a glass electrode for the determination of benzoic acid, when the criterion of efficiency is the sharpness of the end-point inflexion. In non-aqueous titrations of 3,5-xylenol, aluminium and gallium electrodes are similar in efficiency to the glass electrode for determinations in dimethylformamide solution, while the gallium electrode is superior to the glass electrode when 4-methyl-2-pentanone is the solvent. Possible relationships between the properties of the electrode element and the end-point sharpness when it is used as an indicator electrode are briefly considered. PMID:18961658

  12. Method for isolating nucleic acids

    DOEpatents

    Hurt, Jr., Richard Ashley; Elias, Dwayne A.

    2015-09-29

    The current disclosure provides methods and kits for isolating nucleic acid from an environmental sample. The current methods and compositions further provide methods for isolating nucleic acids by reducing adsorption of nucleic acids by charged ions and particles within an environmental sample. The methods of the current disclosure provide methods for isolating nucleic acids by releasing adsorbed nucleic acids from charged particles during the nucleic acid isolation process. The current disclosure facilitates the isolation of nucleic acids of sufficient quality and quantity to enable one of ordinary skill in the art to utilize or analyze the isolated nucleic acids for a wide variety of applications including, sequencing or species population analysis.

  13. Determination of sulphite in wine by coulometric titration.

    PubMed

    Lowinsohn, D; Bertotti, M

    2001-09-01

    A method for the determination of both free and bound S(IV) in white wine samples by coulometric titration with electrogenerated iodine is described, the S(IV) speciation being performed by extracting SO2 from samples acidified wiith hydrochloric acid. Titrations of samples treated with NaOH led to the total S(IV) concentration, the results being in agreement with the ones obtained by the distillation procedure as well as by using the classical Monier-Williams method. An average recovery of 97% was obtained for samples spiked with S(IV) in the range 0.4-1.2 mM, which demonstrated the validity of the proposed procedure. The repeatability was 1.3% and the limit of detection was estimated as 0.01 mM. Results from direct titrations of wine added to the electrochemical cell are reported, which give indications of the stability of adducts towards the reaction with iodine. PMID:11552744

  14. Digital movie-based on automatic titrations.

    PubMed

    Lima, Ricardo Alexandre C; Almeida, Luciano F; Lyra, Wellington S; Siqueira, Lucas A; Gaião, Edvaldo N; Paiva Junior, Sérgio S L; Lima, Rafaela L F C

    2016-01-15

    This study proposes the use of digital movies (DMs) in a flow-batch analyzer (FBA) to perform automatic, fast and accurate titrations. The term used for this process is "Digital movie-based on automatic titrations" (DMB-AT). A webcam records the DM during the addition of the titrant to the mixing chamber (MC). While the DM is recorded, it is decompiled into frames ordered sequentially at a constant rate of 26 frames per second (FPS). The first frame is used as a reference to define the region of interest (ROI) of 28×13pixels and the R, G and B values, which are used to calculate the Hue (H) values for each frame. The Pearson's correlation coefficient (r) is calculated between the H values of the initial frame and each subsequent frame. The titration curves are plotted in real time using the r values and the opening time of the titrant valve. The end point is estimated by the second derivative method. A software written in C language manages all analytical steps and data treatment in real time. The feasibility of the method was attested by application in acid/base test samples and edible oils. Results were compared with classical titration and did not present statistically significant differences when the paired t-test at the 95% confidence level was applied. The proposed method is able to process about 117-128 samples per hour for the test and edible oil samples, respectively, and its precision was confirmed by overall relative standard deviation (RSD) values, always less than 1.0%. PMID:26592600

  15. Reference method for total water in lint cotton by automated oven drying combined with volumetric Karl Fischer titration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In a preliminary study to measure total water in lint cotton we demonstrated that volumetric Karl Fischer Titration of moisture transported by a carrier gas from an attached small oven is more accurate than standard oven drying in air. The objective of the present study was to assess the measuremen...

  16. Nucleic acid detection methods

    DOEpatents

    Smith, C.L.; Yaar, R.; Szafranski, P.; Cantor, C.R.

    1998-05-19

    The invention relates to methods for rapidly determining the sequence and/or length a target sequence. The target sequence may be a series of known or unknown repeat sequences which are hybridized to an array of probes. The hybridized array is digested with a single-strand nuclease and free 3{prime}-hydroxyl groups extended with a nucleic acid polymerase. Nuclease cleaved heteroduplexes can be easily distinguish from nuclease uncleaved heteroduplexes by differential labeling. Probes and target can be differentially labeled with detectable labels. Matched target can be detected by cleaving resulting loops from the hybridized target and creating free 3-hydroxyl groups. These groups are recognized and extended by polymerases added into the reaction system which also adds or releases one label into solution. Analysis of the resulting products using either solid phase or solution. These methods can be used to detect characteristic nucleic acid sequences, to determine target sequence and to screen for genetic defects and disorders. Assays can be conducted on solid surfaces allowing for multiple reactions to be conducted in parallel and, if desired, automated. 18 figs.

  17. Nucleic Acid Detection Methods

    DOEpatents

    Smith, Cassandra L.; Yaar, Ron; Szafranski, Przemyslaw; Cantor, Charles R.

    1998-05-19

    The invention relates to methods for rapidly determining the sequence and/or length a target sequence. The target sequence may be a series of known or unknown repeat sequences which are hybridized to an array of probes. The hybridized array is digested with a single-strand nuclease and free 3'-hydroxyl groups extended with a nucleic acid polymerase. Nuclease cleaved heteroduplexes can be easily distinguish from nuclease uncleaved heteroduplexes by differential labeling. Probes and target can be differentially labeled with detectable labels. Matched target can be detected by cleaving resulting loops from the hybridized target and creating free 3-hydroxyl groups. These groups are recognized and extended by polymerases added into the reaction system which also adds or releases one label into solution. Analysis of the resulting products using either solid phase or solution. These methods can be used to detect characteristic nucleic acid sequences, to determine target sequence and to screen for genetic defects and disorders. Assays can be conducted on solid surfaces allowing for multiple reactions to be conducted in parallel and, if desired, automated.

  18. Determination of carbonate carbon in geological materials by coulometric titration

    USGS Publications Warehouse

    Engleman, E.E.; Jackson, L.L.; Norton, D.R.

    1985-01-01

    A coulometric titration is used for the determination of carbonate carbon in geological materials. Carbon dioxide is evolved from the sample by the addition of 2 M perchloric acid, with heating, and is determined by automated coulometric titration. The coulometric titration showed improved speed and precision with comparable accuracy to gravimetric and gasometric techniques. ?? 1985.

  19. Identification of Weak Acids and Bases by Titration with Primary Standards. A Modern Version of an Old Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Thompson, Robert Q.

    1988-01-01

    Describes a laboratory exercise in which acid dissociation constants and molecular weights are extracted from sample data and the sample is identified. Emphasizes accurate volumetric work while bringing to practice the concepts of acid-base equilibria, activity coefficients, and thermodynamic constants. (CW)

  20. Potentiometric titration of metal ions in ethanol.

    PubMed

    Gibson, Graham T T; Mohamed, Mark F; Neverov, Alexei A; Brown, R S

    2006-09-18

    The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented. PMID:16961382

  1. High-sensitivity titration microcalorimeter

    NASA Astrophysics Data System (ADS)

    Velikov, A. A.; Grigoryev, S. V.; Chuikin, A. V.

    2015-02-01

    A differential titration microcalorimeter for studying intermolecular interactions in solutions has been designed. To increase the speed of the instrument, the dynamic correction method has been used. It has been shown that electrical calibration of the microcalorimeter is consistent with its chemical calibration. The use of the instrument for measuring the integral heats of dilution of 1-propanol has been demonstrated.

  2. Symmetry Properties of Potentiometric Titration Curves.

    ERIC Educational Resources Information Center

    Macca, Carlo; Bombi, G. Giorgio

    1983-01-01

    Demonstrates how the symmetry properties of titration curves can be efficiently and rigorously treated by means of a simple method, assisted by the use of logarithmic diagrams. Discusses the symmetry properties of several typical titration curves, comparing the graphical approach and an explicit mathematical treatment. (Author/JM)

  3. A high-throughput microtiter plate based method for the determination of peracetic acid and hydrogen peroxide.

    PubMed

    Putt, Karson S; Pugh, Randall B

    2013-01-01

    Peracetic acid is gaining usage in numerous industries who have found a myriad of uses for its antimicrobial activity. However, rapid high throughput quantitation methods for peracetic acid and hydrogen peroxide are lacking. Herein, we describe the development of a high-throughput microtiter plate based assay based upon the well known and trusted titration chemical reactions. The adaptation of these titration chemistries to rapid plate based absorbance methods for the sequential determination of hydrogen peroxide specifically and the total amount of peroxides present in solution are described. The results of these methods were compared to those of a standard titration and found to be in good agreement. Additionally, the utility of the developed method is demonstrated through the generation of degradation curves of both peracetic acid and hydrogen peroxide in a mixed solution. PMID:24260173

  4. Hydrogen bonding and molecular association in 2-(quinuclidinium)-butyric acid bromide hydrate studied by X-ray diffraction, DFT calculations, FTIR and NMR spectroscopy, and potentiometric titration

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Z.; Katrusiak, A.; Szafran, M.; Barczyński, P.

    2010-06-01

    The structure of 2-(quinuclidinium)-butyric acid bromide hydrate (QNBu·H 2O·HBr, 3) has been determined by X-ray diffraction, DFT calculations and characterized by FTIR and NMR spectroscopy. Crystals of 3 are monoclinic, space group P2 1. The water molecule interacts with the carboxylic group of 2-(quinuclidinium)-butyric acid and with the bromide anion by the COOH⋯OH 2 and HOH⋯Br hydrogen bonds of 2.575(3) and 3.293(2) Å, respectively. The structures of monomer ( 4) and dimeric cation ( 5) of the title complex have been optimized by the B3LYP/6-31G(d,p) approach, yielding conformations consistent with this in the crystal. The solid-state FTIR spectra of 3 and its deuterated analogue have been measured and compared with the theoretical spectrum of 4. The assignments of the observed and predicted bands have been proposed. The molecule of 3 has a chiral center at the C(9) atom, which is responsible for the non-magnetically equivalence of the α-ring and C(11)H 2 methylene protons in 1H NMR spectrum. The values of p Ka of quinuclidinium-acetate (quinuclidine betaine), 2-(quinuclidinium)-propionate and 2-(quinuclidinium)-butyrate have been determined by the potentiometric titration of their hydrohalides.

  5. Potentiometric titrations using pencil and graphite sensors

    SciTech Connect

    Selig, W.S.

    1984-01-01

    The cost of various commercial indicating electrodes ranges from about $40 for pH electrodes to as much as $355 for a potassium ion-selective electrode. This cost can be reduced to less than $1.50, and in some cases to mere pennies by making sensors from graphite rods and pencils for use in potentiometric titrations. The same sensor can be used for many types of these titrations (acid/base, compleximetric, precipitation, and redox). 8 references, 2 tables.

  6. Modeling complexometric titrations of natural water samples.

    PubMed

    Hudson, Robert J M; Rue, Eden L; Bruland, Kenneth W

    2003-04-15

    Complexometric titrations are the primary source of metal speciation data for aquatic systems, yet their interpretation in waters containing humic and fulvic acids remains problematic. In particular, the accuracy of inferred ambient free metal ion concentrations and parameters quantifying metal complexation by natural ligands has been challenged because of the difficulties inherent in calibrating common analytical methods and in modeling the diverse array of ligands present. This work tests and applies a new method of modeling titration data that combines calibration of analytical sensitivity (S) and estimation of concentrations and stability constants for discrete natural ligand classes ([Li]T and Ki) into a single step using nonlinear regression and a new analytical solution to the one-metal/two-ligand equilibrium problem. When applied to jointly model data from multiple titrations conducted at different analytical windows, it yields accurate estimates of S, [Li]T, Ki, and [Cu2+] plus Monte Carlo-based estimates of the uncertainty in [Cu2+]. Jointly modeling titration data at low-and high-analytical windows leads to an efficient adaptation of the recently proposed "overload" approach to calibrating ACSV/CLE measurements. Application of the method to published data sets yields model results with greater accuracy and precision than originally obtained. The discrete ligand-class model is also re-parametrized, using humic and fulvic acids, L1 class (K1 = 10(13) M(-1)), and strong ligands (L(S)) with K(S) > K1 as "natural components". This approach suggests that Cu complexation in NW Mediterranean Sea water can be well represented as 0.8 +/- 0.3/0.2 mg humic equiv/L, 13 +/- 1 nM L1, and 2.5 +/- 0.1 nM L(S) with [CU]T = 3 nM. In coastal seawater from Narragansett Bay, RI, Cu speciation can be modeled as 0.6 +/- 0.1 mg humic equiv/L and 22 +/- 1 nM L1 or approximately 12 nM L1 and approximately 9 nM L(S), with [CU]T = 13 nM. In both waters, the large excess

  7. Non-aqueous titration of quinine and quinidine sulphates by use of barium perchlorate.

    PubMed

    Zakhari, N; Ibrahim, F; Kovar, K A

    1989-07-01

    A simple non-aqueous titration method has been devised for determining the sulphates of quinine and quinidine. The sulphate is precipitated by addition of excess of barium perchlorate solution in acetic and the liberated alkaloid is then titrated in 1:2 anhydrous acetic-dioxan mixture, with an acetic acid solution of perchloric acid. The end-point is determined either visually with Crystal Violet as indicator or potentiometrically with a glass-Ag/AgCl combination electrode. The method is accurate, precise and suitable for routine analysis of pure materials and tablets. PMID:18964803

  8. Micro coulometric titration in a liquid drop.

    PubMed

    Kanyanee, Tinakorn; Fuekhad, Pongwasin; Grudpan, Kate

    2013-10-15

    Miniaturized coulometric titration in a liquid drop has been investigated. Assays of ascorbic acid and thiosulfate with iodine titration were chosen as models. Constant volumes of falling liquid drops containing sample or reagent are manipulated via gravimetrical force to move along a slope hydrophobic path and directed to stop or to move out from an electrode. Such manipulation is useful for delivery of sample and reagents, in a way of flow without tubing. Electrochemical generation of titrant, in this case, iodine, is started at the electrode and micro coulometric titration can be performed in a drop by applying constant current. Timing in the titration can be made via naked eye with a stopwatch or via recording with a webcam camera connecting to a computer to detect the change due to the blue color complex of the excess iodine and starch. PMID:24054589

  9. Derivative analysis of potentiometric titration data to obtain protonation constants

    SciTech Connect

    Chen, J.F.; Xia, Y.X.; Choppin, G.R.

    1996-11-15

    A methodology is described to calibrate glass electrodes and to analyze potentiometric titration data to calculate protonation constants. The analysis uses the variation of dV/dpH with titrant addition in terms of two physical parameters which involve the concentrations of H{sup +}, OH{sup -}, and H{sub m}A. The data for titration of acetic acid and 8-hydroxyquinoline in 0.10-5.0 m NaCl media are analyzed by this method to obtain the stoichiometric protonation constants of the acids, the ionization constants of water, and the parameters s and b in the pH electrode calibration equation, pcH = spH{sub m} + b, where pcH = -log[H{sup +}], pH{sub m} is the pH meter reading. 31 refs., 3 figs., 6 tabs.

  10. Students' integration of multiple representations in a titration experiment

    NASA Astrophysics Data System (ADS)

    Kunze, Nicole M.

    A complete understanding of a chemical concept is dependent upon a student's ability to understand the microscopic or particulate nature of the phenomenon and integrate the microscopic, symbolic, and macroscopic representations of the phenomenon. Acid-base chemistry is a general chemistry topic requiring students to understand the topics of chemical reactions, solutions, and equilibrium presented earlier in the course. In this study, twenty-five student volunteers from a second semester general chemistry course completed two interviews. The first interview was completed prior to any classroom instruction on acids and bases. The second interview took place after classroom instruction, a prelab activity consisting of a titration calculation worksheet, a titration computer simulation, or a microscopic level animation of a titration, and two microcomputer-based laboratory (MBL) titration experiments. During the interviews, participants were asked to define and describe acid-base concepts and in the second interview they also drew the microscopic representations of four stages in an acid-base titration. An analysis of the data showed that participants had integrated the three representations of an acid-base titration to varying degrees. While some participants showed complete understanding of acids, bases, titrations, and solution chemistry, other participants showed several alternative conceptions concerning strong acid and base dissociation, the formation of titration products, and the dissociation of soluble salts. Before instruction, participants' definitions of acid, base, and pH were brief and consisted of descriptive terms. After instruction, the definitions were more scientific and reflected the definitions presented during classroom instruction.

  11. Gasometric titration for dimethylaluminum chloride analysis.

    PubMed

    Wang, Lin; Maligres, Peter; Eckenroad, Kyle; Simmons, Bryon

    2016-06-01

    A gasometric titration method was developed to quantitate active alkylaluminum content in dimethylaluminum chloride solution to perform the stoichiometry calculation for the reaction charge. The procedure was reproducible with good precision, and the results showed good correlation with ICP-MS method. The gasometric titration is a simple, inexpensive alternative to analysis via ICP-MS which provides more selective analysis of methylaluminum species without the need for inertion. PMID:27017569

  12. Comparative assessment of the methods for exchangeable acidity measuring

    NASA Astrophysics Data System (ADS)

    Vanchikova, E. V.; Shamrikova, E. V.; Bespyatykh, N. V.; Zaboeva, G. A.; Bobrova, Yu. I.; Kyz"yurova, E. V.; Grishchenko, N. V.

    2016-05-01

    A comparative assessment of the results of measuring the exchangeable acidity and its components by different methods was performed for the main mineral genetic horizons of texturally-differentiated gleyed and nongleyed soddy-podzolic and gley-podzolic soils of the Komi Republic. It was shown that the contents of all the components of exchangeable soil acidity determined by the Russian method (with potassium chloride solution as extractant, c(KCl) = 1 mol/dm3) were significantly higher than those obtained by the international method (with barium chloride solution as extractant, c(BaCl2) = 0.1 mol/dm3). The error of the estimate of the concentration of H+ ions extracted with barium chloride solution equaled 100%, and this allowed only qualitative description of this component of the soil acidity. In the case of the extraction with potassium chloride, the error of measurements was 50%. It was also shown that the use of potentiometric titration suggested by the Russian method overestimates the results of soil acidity measurement caused by the exchangeable metal ions (Al(III), Fe(III), and Mn(II)) in comparison with the atomic emission method.

  13. Titration Calculations with Computer Algebra Software

    ERIC Educational Resources Information Center

    Lachance, Russ; Biaglow, Andrew

    2012-01-01

    This article examines the symbolic algebraic solution of the titration equations for a diprotic acid, as obtained using "Mathematica," "Maple," and "Mathcad." The equilibrium and conservation equations are solved symbolically by the programs to eliminate the approximations that normally would be performed by the student. Of the three programs,…

  14. Comparison between dot-immunoblotting assay and clinical sign determination method for quantifying avian infectious bronchitis virus vaccine by titration in embryonated eggs.

    PubMed

    Yuk, Seong-su; Kwon, Jung-Hoon; Noh, Jin-Yong; Hong, Woo-tack; Gwon, Gyeong-Bin; Jeong, Jei-Hyun; Jeong, Sol; Youn, Ha-Na; Heo, Yong-Hwan; Lee, Joong-Bok; Park, Seung-Yong; Choi, In-Soo; Song, Chang-Seon

    2016-04-01

    A sensitive and specific method for measuring the vaccine titer of infectious bronchitis virus (IBV) is important to commercial manufacturers for improving vaccine quality. Typically, IBV is titrated in embryonated chicken eggs, and the infectivity of the virus dilutions is determined by assessing clinical signs in the embryos as evidence of viral propagation. In this study, we used a dot-immunoblotting assay (DIA) to measure the titers of IBV vaccines that originated from different pathogenic strains or attenuation methods in embryonated eggs, and we compared this assay to the currently used method, clinical sign evaluation. To compare the two methods, we used real-time reverse transcription-PCR, which had the lowest limit of detection for propagated IBV. As a clinical sign of infection, dwarfism of the embryo was quantified using the embryo: egg (EE) index. The DIA showed 9.41% higher sensitivity and 15.5% higher specificity than the clinical sign determination method. The DIA was particularly useful for measuring the titer of IBV vaccine that did not cause apparent stunting but propagated in embryonated chicken eggs such as a heat-adapted vaccine strain. The results of this study indicate that the DIA is a rapid, sensitive, reliable method for determining IBV vaccine titer in embryonated eggs at a relatively low cost. PMID:26802454

  15. Standard test method for water in lint cotton by oven evaporation combined with volumetric Karl Fischer Titration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The referenced test method for total water content and water regain in lint cotton was developed by USDA scientists in New Orleans at the request of the cotton industry. The method covers the determination of the total water (free and bound) in raw and lint cotton at moisture equilibrium from con...

  16. [Alkalimetric titrations of salts of organic bases in the Pharmacopoeia].

    PubMed

    Bezáková, Zelmíra; Stankovičová, Mária

    2013-12-01

    Modified methods - alkalimetry in ethanol 70% with a defined small volume of hydrochloric acid 0.01 mol/l added to the solution of the sample before the titration and alkalimetry in ethanol 70% or ethanol 96% alone with potentiometric end-point detection for the assay of halide salts of 11 organic N-bases has been investigated. The results were compared to those obtained by the method of the European Pharmacopoeia 7th Ed. (Ph. Eur. 7th Ed.). The Ph. Eur. 7th Ed. use for 8 investigated substances alkalimetry in alcohol 96 % with a defined small volume of hydrochloric acid 0.01 mol/l (5 ml) with potentiometric end-point detection: Cinchocaine hydrochloride, Codeine hydrochloride dihydrate, Ethylmorphine hydrochloride, Lidocaine hydrochloride, Papaverine hydrochloride, Pilocarpine hydrochloride, Quinine hydrochloride, Tetracaine hydrochloride. Our results revealed that the Ph. Eur. 7th Ed. method did not work for 5 drugs from this group: Cinchocaine hydrochloride, Ethylmorphine hydrochloride, Papaverine hydrochloride, Pilocarpine hydrochloride and Tetracaine hydrochloride. In the group of investigated substances we included also drugs with the character of weak organic bases for which Ph. Eur. 7th Ed. prescribed different methods for their assay: Thiamine hydrochloride and Pyridoxine hydrochloride - acidimetric titration in non-aqueous solvents with perchloric acid and Procaine hydrochloride - determination of primary aromatic amino-nitrogen (Ph. Eur. 7th Ed., chapter 2.5.8). PMID:24393115

  17. Probing the binding mechanisms of α-tocopherol to trypsin and pepsin using isothermal titration calorimetry, spectroscopic, and molecular modeling methods.

    PubMed

    Li, Xiangrong; Ni, Tianjun

    2016-06-01

    α-Tocopherol is a required nutrient for a variety of biological functions. In this study, the binding of α-tocopherol to trypsin and pepsin was investigated using isothermal titration calorimetry (ITC), steady-state and time-resolved fluorescence measurements, circular dichroism (CD) spectroscopy, and molecular modeling methods. Thermodynamic investigations reveal that α-tocopherol binds to trypsin/pepsin is synergistically driven by enthalpy and entropy. The fluorescence experimental results indicate that α-tocopherol can quench the fluorescence of trypsin/pepsin through a static quenching mechanism. The binding ability of α-tocopherol with trypsin/pepsin is in the intermediate range, and one molecule of α-tocopherol combines with one molecule of trypsin/pepsin. As shown by circular dichroism (CD) spectroscopy, α-tocopherol may induce conformational changes of trypsin/pepsin. Molecular modeling displays the specific binding site and gives information about binding forces and α-tocopherol-tryptophan (Trp)/tyrosine (Tyr) distances. In addition, the inhibition rate of α-tocopherol on trypsin and pepsin was studied. The study provides a basic data set for clarifying the binding mechanisms of α-tocopherol with trypsin and pepsin and is helpful for understanding its biological activity in vivo. PMID:27094449

  18. Recruitment Maneuvers and PEEP Titration.

    PubMed

    Hess, Dean R

    2015-11-01

    The injurious effects of alveolar overdistention are well accepted, and there is little debate regarding the importance of pressure and volume limitation during mechanical ventilation. The role of recruitment maneuvers is more controversial. Alveolar recruitment is desirable if it can be achieved, but the potential for recruitment is variable among patients with ARDS. A stepwise recruitment maneuver, similar to an incremental PEEP titration, is favored over sustained inflation recruitment maneuvers. Many approaches to PEEP titration have been proposed, and the best method to choose the most appropriate level for an individual patient is unclear. A PEEP level should be selected that balances alveolar recruitment against overdistention. The easiest approach to select PEEP might be according to the severity of the disease: 5-10 cm H2O PEEP in mild ARDS, 10-15 cm H2O PEEP in moderate ARDS, and 15-20 cm H2O PEEP in severe ARDS. Recruitment maneuvers and PEEP should be used within the context of lung protection and not just as a means of improving oxygenation. PMID:26493593

  19. Isothermal titration calorimetry of RNA.

    PubMed

    Salim, Nilshad N; Feig, Andrew L

    2009-03-01

    Isothermal titration calorimetry (ITC) is a fast and robust method to study the physical basis of molecular interactions. A single well-designed experiment can provide complete thermodynamic characterization of a binding reaction, including K(a), DeltaG, DeltaH, DeltaS and reaction stoichiometry (n). Repeating the experiment at different temperatures allows determination of the heat capacity change (DeltaC(P)) of the interaction. Modern calorimeters are sensitive enough to probe even weak biological interactions making ITC a very popular method among biochemists. Although ITC has been applied to protein studies for many years, it is becoming widely applicable in RNA biochemistry as well, especially in studies which involve RNA folding and RNA interactions with small molecules, proteins and with other RNAs. This review focuses on best practices for planning, designing and executing effective ITC experiments when one or more of the reactants is an RNA. PMID:18835447

  20. Modeling data from titration, amide H/D exchange, and mass spectrometry to obtain protein-ligand binding constants.

    PubMed

    Zhu, Mei M; Rempel, Don L; Gross, Michael L

    2004-03-01

    We recently reported a new method for quantification of protein-ligand interaction by mass spectrometry, titration and H/D exchange (PLIMSTEX) for determining the binding stoichiometry and affinity of a wide range of protein-ligand interactions. Here we describe the method for analyzing the PLIMSTEX titration curves and evaluate the effect of various models on the precision and accuracy for determining binding constants using H/D exchange and a titration. The titration data were fitted using a 1:n protein:ligand sequential binding model, where n is the number of binding sites for the same ligand. An ordinary differential equation was used for the first time in calculating the free ligand concentration from the total ligand concentration. A nonlinear least squares regression method was applied to minimize the error between the calculated and the experimentally measured deuterium shift by varying the unknown parameters. A resampling method and second-order statistics were used to evaluate the uncertainties of the fitting parameters. The interaction of intestinal fatty-acid-binding protein (IFABP) with a fatty-acid carboxylate and that of calmodulin with Ca(2+) are used as two tests. The modeling process described here not only is a new tool for analyzing H/D exchange data acquired by ESI-MS, but also possesses novel aspects in modeling experimental titration data to determine the affinity of ligand binding. PMID:14998541

  1. Microscale pH Titrations Using an Automatic Pipet.

    ERIC Educational Resources Information Center

    Flint, Edward B.; Kortz, Carrie L.; Taylor, Max A.

    2002-01-01

    Presents a microscale pH titration technique that utilizes an automatic pipet. A small aliquot (1-5 mL) of the analyte solution is titrated with repeated additions of titrant, and the pH is determined after each delivery. The equivalence point is determined graphically by either the second derivative method or a Gran plot. The pipet can be…

  2. Nucleic acid arrays and methods of synthesis

    DOEpatents

    Sabanayagam, Chandran R.; Sano, Takeshi; Misasi, John; Hatch, Anson; Cantor, Charles

    2001-01-01

    The present invention generally relates to high density nucleic acid arrays and methods of synthesizing nucleic acid sequences on a solid surface. Specifically, the present invention contemplates the use of stabilized nucleic acid primer sequences immobilized on solid surfaces, and circular nucleic acid sequence templates combined with the use of isothermal rolling circle amplification to thereby increase nucleic acid sequence concentrations in a sample or on an array of nucleic acid sequences.

  3. Explicit formulation of titration models for isothermal titration calorimetry.

    PubMed

    Poon, Gregory M K

    2010-05-15

    Isothermal titration calorimetry (ITC) produces a differential heat signal with respect to the total titrant concentration. This feature gives ITC excellent sensitivity for studying the thermodynamics of complex biomolecular interactions in solution. Currently, numerical methods for data fitting are based primarily on indirect approaches rooted in the usual practice of formulating biochemical models in terms of integrated variables. Here, a direct approach is presented wherein ITC models are formulated and solved as numerical initial value problems for data fitting and simulation purposes. To do so, the ITC signal is cast explicitly as a first-order ordinary differential equation (ODE) with total titrant concentration as independent variable and the concentration of a bound or free ligand species as dependent variable. This approach was applied to four ligand-receptor binding and homotropic dissociation models. Qualitative analysis of the explicit ODEs offers insights into the behavior of the models that would be inaccessible to indirect methods of analysis. Numerical ODEs are also highly compatible with regression analysis. Since solutions to numerical initial value problems are straightforward to implement on common computing platforms in the biochemical laboratory, this method is expected to facilitate the development of ITC models tailored to any experimental system of interest. PMID:20100451

  4. Alkylated lariat ethers as solvent extraction reagents: Surveying the extraction of alkali metals by bis-t-octylbenzo-14-crown-4-acetic acid by use of potentiometric two-phase titration

    SciTech Connect

    Sachleben, R.A.; Moyer, B.A.; Case, F.I.; Garmon, S.A.

    1993-01-01

    Two-phase potentiometric titrimetry was used to survey the extraction of alkali metal cations from aqueous chloride solution by the lipophilic, ionizable lariat ether bis-(t-octylbenzo)-14-crown-4-acetic acid (BOB14C4AA) in o-xylene. Analysis of the data indicates that ion-exchange extraction by the crown-carboxylic acid at low loading (i.e., low conversion of BOB14C4AA to its salt form) is stronger for lithium ion than for the other alkali metals. Little or no selectivity occurs at high loadings. In comparison with the long-chain carboxylic acid 2-methyl-2-heptylnonanoic acid (HMHN), BOB14C4AA extracts lithium and sodium at significantly lower pH; in the loading range of 0.1 to 0.7, the pH shift is 1.4-1.8 pH units for sodium ion and 1.7-2.3 pH units for lithium ion. The titration data are interpreted in terms of aggregated organic-phase species. In the case of lithium extraction, clear evidence was found for a species in which neutral BOB14C4AA participates in the organic-phase complexation of the metal cation.

  5. Photometric method for determination of acidity constants through integral spectra analysis.

    PubMed

    Zevatskiy, Yuriy Eduardovich; Ruzanov, Daniil Olegovich; Samoylov, Denis Vladimirovich

    2015-04-15

    An express method for determination of acidity constants of organic acids, based on the analysis of the integral transmittance vs. pH dependence is developed. The integral value is registered as a photocurrent of photometric device simultaneously with potentiometric titration. The proposed method allows to obtain pKa using only simple and low-cost instrumentation. The optical part of the experimental setup has been optimized through the exclusion of the monochromator device. Thus it only takes 10-15 min to obtain one pKa value with the absolute error of less than 0.15 pH units. Application limitations and reliability of the method have been tested for a series of organic acids of various nature. PMID:25668697

  6. Photometric method for determination of acidity constants through integral spectra analysis

    NASA Astrophysics Data System (ADS)

    Zevatskiy, Yuriy Eduardovich; Ruzanov, Daniil Olegovich; Samoylov, Denis Vladimirovich

    2015-04-01

    An express method for determination of acidity constants of organic acids, based on the analysis of the integral transmittance vs. pH dependence is developed. The integral value is registered as a photocurrent of photometric device simultaneously with potentiometric titration. The proposed method allows to obtain pKa using only simple and low-cost instrumentation. The optical part of the experimental setup has been optimized through the exclusion of the monochromator device. Thus it only takes 10-15 min to obtain one pKa value with the absolute error of less than 0.15 pH units. Application limitations and reliability of the method have been tested for a series of organic acids of various nature.

  7. Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter

    NASA Astrophysics Data System (ADS)

    Ritchie, Jason D.; Perdue, E. Michael

    2003-01-01

    The acid-base properties of 14 standard and reference materials from the International Humic Substances Society (IHSS) were investigated by potentiometric titration. Titrations were conducted in 0.1 M NaCl under a nitrogen atmosphere, averaging 30 min from start to finish. Concentrations of carboxyl groups and phenolic groups were estimated directly from titration curves. Titration data were also fit to a modified Henderson-Hasselbalch model for two classes of proton-binding sites to obtain "best fit" parameters that describe proton-binding curves for the samples. The model was chosen for its simplicity, its ease of implementation in computer spreadsheets, and its excellent ability to describe the shapes of the titration curves. The carboxyl contents of the IHSS samples are in the general order: terrestrial fulvic acids > aquatic fulvic acids > Suwannee River natural organic matter (NOM) > aquatic humic acids > terrestrial humic acids. Overall, fulvic acids and humic acids have similar phenolic contents; however, all of the aquatically derived samples have higher phenolic contents than the terrestrially derived samples. The acid-base properties of reference Suwannee River NOM are surprisingly similar to those of standard Suwannee River humic acid. Results from titrations in this study were compared with other published results from both direct and indirect titrations. Typically, carboxyl contents for the IHSS samples were in agreement with the results from both methods of titration. Phenolic contents for the IHSS samples were comparable to those determined by direct titrations, but were significantly less than estimates of phenolic content that were based on indirect titrations with Ba(OH) 2 and Ca(OAc) 2. The average phenolic-to-carboxylic ratio of the IHSS samples is approximately 1:4. Models that assume a 1:2 ratio of phenolic-to-carboxylic groups may overestimate the relative contribution of phenolic groups to the acid-base chemistry of humic substances.

  8. Kinetic titration series with biolayer interferometry.

    PubMed

    Frenzel, Daniel; Willbold, Dieter

    2014-01-01

    Biolayer interferometry is a method to analyze protein interactions in real-time. In this study, we illustrate the usefulness to quantitatively analyze high affinity protein ligand interactions employing a kinetic titration series for characterizing the interactions between two pairs of interaction patterns, in particular immunoglobulin G and protein G B1 as well as scFv IC16 and amyloid beta (1-42). Kinetic titration series are commonly used in surface plasmon resonance and involve sequential injections of analyte over a desired concentration range on a single ligand coated sensor chip without waiting for complete dissociation between the injections. We show that applying this method to biolayer interferometry is straightforward and i) circumvents problems in data evaluation caused by unavoidable sensor differences, ii) saves resources and iii) increases throughput if screening a multitude of different analyte/ligand combinations. PMID:25229647

  9. Automatic photometric titrations of calcium and magnesium in carbonate rocks

    USGS Publications Warehouse

    Shapiro, L.; Brannock, W.W.

    1955-01-01

    Rapid nonsubjective methods have been developed for the determination of calcium and magnesium in carbonate rocks. From a single solution of the sample, calcium is titrated directly, and magnesium is titrated after a rapid removal of R2O3 and precipitation of calcium as the tungstate. A concentrated and a dilute solution of disodium ethylenediamine tetraacetate are used as titrants. The concentrated solution is added almost to the end point, then the weak solution is added in an automatic titrator to determine the end point precisely.

  10. Well acidizing compositions and method

    SciTech Connect

    Gardener, T.R.; Dill, W.R.; Ford, W.G.F.; King, K.L.

    1991-07-23

    This patent describes a concentrate which forms an acid internal microemulsion well treatment composition when added to an acid treatment fluid. It comprises in the range of from about 20% to about 98% by weight of a hydrocarbon carrier fluid; in the range of from about 1% to about 50% by weight of an alkyl alcohol having in the range of from about 4 to 18 carbon atoms; and in the range of from about 1% to about 50% by weight of an emulsifying agent comprising at least one compound selected from the group consisting of amine salts having ester or amide linkages and propoxylated alcohols, each of the components being different compounds or different mixtures of compounds.

  11. [Indirect hemagglutination inhibition reactions as a method of titrating immune serums. V. Application of the reaction to the quantitative determination of immunoglobulins A, M and G in human blood sera].

    PubMed

    Konikova, R E; Semenova, B N; Noskov, F S; Shakhanina, K L; Malkina, L A

    1975-01-01

    The authors present the results of using the indirect hemagglutination inhibition test (IHIT) for quantitative determination of A, M and G immunoglobulins in the blood sera of humans in comparison with the method of radial immunodiffusion in agar (RID) after Mancini. The results of IHIT were no less precise and reproducible than those of RID. The significance of the correlation coefficient of grades after Spirman constituted greater than 99.9% for both tests. On this basis a conclusion was made that, having a number of advantages over RID, IHIT could be recommended for quantitative titration of immunoglobulins of various classes. PMID:804778

  12. Metrological assessment of the methods for measuring the contents of acids and ion metals responsible for the exchangeable acidity of soils

    NASA Astrophysics Data System (ADS)

    Vanchikova, E. V.; Shamrikova, E. V.; Bespyatykh, N. V.; Kyz"yurova, E. V.; Kondratenok, B. M.

    2015-02-01

    Metrological characteristics—precision, trueness, and accuracy—of the results of measurements of the exchangeable acidity and its components by the potentiometric titration method were studied on the basis of multiple analyses of the soil samples with the examination of statistical data for the outliers and their correspondence to the normal distribution. Measurement errors were estimated. The applied method was certified by the Metrological Center of the Uralian Branch of the Russian Academy of Sciences (certificate no. 88-17641-094-2013) and included in the Federal Information Fund on Assurance of Measurements (FR 1.31.2013.16382).

  13. Method for sequencing nucleic acid molecules

    DOEpatents

    Korlach, Jonas; Webb, Watt W.; Levene, Michael; Turner, Stephen; Craighead, Harold G.; Foquet, Mathieu

    2006-05-30

    The present invention is directed to a method of sequencing a target nucleic acid molecule having a plurality of bases. In its principle, the temporal order of base additions during the polymerization reaction is measured on a molecule of nucleic acid, i.e. the activity of a nucleic acid polymerizing enzyme on the template nucleic acid molecule to be sequenced is followed in real time. The sequence is deduced by identifying which base is being incorporated into the growing complementary strand of the target nucleic acid by the catalytic activity of the nucleic acid polymerizing enzyme at each step in the sequence of base additions. A polymerase on the target nucleic acid molecule complex is provided in a position suitable to move along the target nucleic acid molecule and extend the oligonucleotide primer at an active site. A plurality of labelled types of nucleotide analogs are provided proximate to the active site, with each distinguishable type of nucleotide analog being complementary to a different nucleotide in the target nucleic acid sequence. The growing nucleic acid strand is extended by using the polymerase to add a nucleotide analog to the nucleic acid strand at the active site, where the nucleotide analog being added is complementary to the nucleotide of the target nucleic acid at the active site. The nucleotide analog added to the oligonucleotide primer as a result of the polymerizing step is identified. The steps of providing labelled nucleotide analogs, polymerizing the growing nucleic acid strand, and identifying the added nucleotide analog are repeated so that the nucleic acid strand is further extended and the sequence of the target nucleic acid is determined.

  14. Method for sequencing nucleic acid molecules

    DOEpatents

    Korlach, Jonas; Webb, Watt W.; Levene, Michael; Turner, Stephen; Craighead, Harold G.; Foquet, Mathieu

    2006-06-06

    The present invention is directed to a method of sequencing a target nucleic acid molecule having a plurality of bases. In its principle, the temporal order of base additions during the polymerization reaction is measured on a molecule of nucleic acid, i.e. the activity of a nucleic acid polymerizing enzyme on the template nucleic acid molecule to be sequenced is followed in real time. The sequence is deduced by identifying which base is being incorporated into the growing complementary strand of the target nucleic acid by the catalytic activity of the nucleic acid polymerizing enzyme at each step in the sequence of base additions. A polymerase on the target nucleic acid molecule complex is provided in a position suitable to move along the target nucleic acid molecule and extend the oligonucleotide primer at an active site. A plurality of labelled types of nucleotide analogs are provided proximate to the active site, with each distinguishable type of nucleotide analog being complementary to a different nucleotide in the target nucleic acid sequence. The growing nucleic acid strand is extended by using the polymerase to add a nucleotide analog to the nucleic acid strand at the active site, where the nucleotide analog being added is complementary to the nucleotide of the target nucleic acid at the active site. The nucleotide analog added to the oligonucleotide primer as a result of the polymerizing step is identified. The steps of providing labelled nucleotide analogs, polymerizing the growing nucleic acid strand, and identifying the added nucleotide analog are repeated so that the nucleic acid strand is further extended and the sequence of the target nucleic acid is determined.

  15. Studying Current-Potential Curves Using a Bipotentiometric Lodometric Back-Titration for the Determination of Ascorbic Acid in Fruits and Vegetables

    ERIC Educational Resources Information Center

    Verdini, Roxana A.; Lagier, Claudia M.

    2004-01-01

    Voltammetry principles are introduced to students by means of a bipotentiometric method to determine vitamin C in fruits and vegetables. The aim is to draw attention to voltammetric methods, particular to the study of current-potential curves, stressing the potential applicability in areas of food quality control.

  16. A Laser-Pointer-Based Spectrometer for Endpoint Detection of EDTA Titrations

    ERIC Educational Resources Information Center

    Dahm, Christopher E.; Hall, James W.; Mattioni, Brian E.

    2004-01-01

    A laser spectrometer for the ethylenediaminetetra-acetic acid (EDTA) titration of magnesium or calcium ions that is designed around a handheld laser pointer as the source and a photoresistor as the detector is developed. Findings show that the use of the spectrometer reduces the degree of uncertainty and error in one part of the EDTA titrations,…

  17. Methods for analyzing nucleic acid sequences

    DOEpatents

    Korlach, Jonas; Webb, Watt W.; Levene, Michael; Turner, Stephen; Craighead, Harold G.; Foquet, Mathieu

    2011-05-17

    The present invention is directed to a method of sequencing a target nucleic acid. The method provides a complex comprising a polymerase enzyme, a target nucleic acid molecule, and a primer, wherein the complex is immobilized on a support Fluorescent label is attached to a terminal phosphate group of the nucleotide or nucleotide analog. The growing nucleic acid strand is extended by using the polymerase to add a nucleotide analog to the nucleic acid strand. The nucleotide analog added to the oligonucleotide primer as a result of the polymerizing step is identified. The time duration of the signal from labeled nucleotides or nucleotide analogs that become incorporated is distinguished from freely diffusing labels by a longer retention in the observation volume for the nucleotides or nucleotide analogs that become incorporated than for the freely diffusing labels.

  18. Phenolic acid esterases, coding sequences and methods

    DOEpatents

    Blum, David L.; Kataeva, Irina; Li, Xin-Liang; Ljungdahl, Lars G.

    2002-01-01

    Described herein are four phenolic acid esterases, three of which correspond to domains of previously unknown function within bacterial xylanases, from XynY and XynZ of Clostridium thermocellum and from a xylanase of Ruminococcus. The fourth specifically exemplified xylanase is a protein encoded within the genome of Orpinomyces PC-2. The amino acids of these polypeptides and nucleotide sequences encoding them are provided. Recombinant host cells, expression vectors and methods for the recombinant production of phenolic acid esterases are also provided.

  19. Determination of lanthanum by flame photometric titration.

    PubMed

    Svehla, G; Slevin, P J

    1968-09-01

    The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere. PMID:18960392

  20. Complexometric titrations: new reagents and concepts to overcome old limitations.

    PubMed

    Zhai, Jingying; Bakker, Eric

    2016-07-21

    Chelators and end point indicators are the most important parts of complexometric titrations. The most widely used universal chelator ethylenediamine tetraacetic acid (EDTA) and its derivatives can strongly coordinate with different metal ions. Their limited selectivity often requires the use of masking agents, and the multiple pKa values of the chelators necessitate a careful adjustment of pH during the procedure. Real world requirements for pH independent, selective and sensitive chelators and indicators call for a new design of these reagents. New concepts and structures of chelators and indicators have indeed recently emerged. We present here recent developments on chelators and indicators for complexometric titrations. Many of these advances were made possible only recently by moving the titration from a homogeneous to a heterogeneous phase using a new class of chelators and indicators based on highly selective ionophores embedded in ion-selective nanosphere emulsions. In view of achieving titrations in situ by complete instrumental control, thin layer electrochemistry has recently been shown to be an attractive concept that replaces the traditional cumbersome titration protocol with a direct reagent free sensing tool. PMID:27272695

  1. Titration of Isolated Cell Walls of Lemna minor L 1

    PubMed Central

    Morvan, Claudine; Demarty, Maurice; Thellier, Michel

    1979-01-01

    A theoretical model has been built to bypass the equation of titration of the cell wall. This equation, which is an extension of the Henderson-Hasselbach equation, underlines the importance of the exchange constant, the ionic strength as well as the rate of neutralization. The model is restricted to the case when the ionization degree is equal to the neutralization degree. The shape of the titration curve is shown to be strongly dependent on the valency of the base used. Experimental results have shown that isolated cell walls bear at least two kinds of sites. The first sites which are titrated after a short time of equilibration are attributed to polyuronic acids (capacity: 0.3 milliequivalents per gram fresh cell walls). The second sites, are obtained after a long time of equilibration (capacity: 1.2 to 1.3 milliequivalents per gram, fresh cell walls). Titrations have been performed with different bases [KOH, NaOH, and Ca(OH)2] and under different ionic strengths. The results obtained with NaOH and KOH do not exhibit any difference of selectivity. Conversely, the sites have a much bigger affinity for the Ca2+ ions than for the monovalent ones. The apparent pKa of the uronic acids was estimated to lie between 3.0 and 3.4; this is consistent with the values obtained with polyuronic acid solutions. PMID:16660868

  2. A Geochemical Reaction Model for Titration of Contaminated Soil and Groundwater at the Oak Ridge Reservation

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Parker, J. C.; Gu, B.; Luo, W.; Brooks, S. C.; Spalding, B. P.; Jardine, P. M.; Watson, D. B.

    2007-12-01

    This study investigates geochemical reactions during titration of contaminated soil and groundwater at the Oak Ridge Reservation in eastern Tennessee. The soils and groundwater exhibits low pH and high concentrations of aluminum, calcium, magnesium, manganese, various trace metals such as nickel and cobalt, and radionuclides such as uranium and technetium. The mobility of many of the contaminant species diminishes with increasing pH. However, base additions to increase pH are strongly buffered by various precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior and associated geochemical effects is thus critical to evaluate remediation performance of pH manipulation strategies. This study was undertaken to develop a practical but generally applicable geochemical model to predict aqueous and solid-phase speciation during soil and groundwater titration. To model titration in the presence of aquifer solids, an approach proposed by Spalding and Spalding (2001) was utilized, which treats aquifer solids as a polyprotic acid. Previous studies have shown that Fe and Al-oxyhydroxides strongly sorb dissolved Ni, U and Tc species. In this study, since the total Fe concentration is much smaller than that of Al, only ion exchange reactions associated with Al hydroxides are considered. An equilibrium reaction model that includes aqueous complexation, precipitation, ion exchange, and soil buffering reactions was developed and implemented in the code HydroGeoChem 5.0 (HGC5). Comparison of model results with experimental titration curves for contaminated groundwater alone and for soil- water systems indicated close agreement. This study is expected to facilitate field-scale modeling of geochemical processes under conditions with highly variable pH to develop practical methods to control contaminant mobility at geochemically complex sites.

  3. Evaluation of an automatic uranium titration system

    SciTech Connect

    Lewis, K.

    1980-01-01

    The titration system utilizes the constant current coulometric titration of Goldbeck and Lerner. U(VI) is reduced to U(IV) by Fe(II). V(V) is generated to titrate the U(IV), and the titration is followed potentiometrically. The evaluation shows that the recovery of uranium is 100% at the 40-mg level. The accuracy is generally +-0.10% or better. The smallest sample weight at which reliable results were obtained was 40 mg of uranium. Time for one analysis is 15 minutes. Advantages and disadvantages of the automated titrator are listed. (DLC)

  4. Determination of free acid by standard addition method in potassium thiocyanate

    SciTech Connect

    Baumann, E W

    1982-06-01

    The free acid content of solutions containing hydrolyzable ions has been determined potentiometrically by a standard addition method. Two increments of acid are added to the sample in 1M potassium thiocyanate solution. The sample concentration is calculated by solution of three simultaneous Nernst equations. The method has been demonstrated for solutions containing Al/sup 3 +/, Cr/sup 3 +/, Fe/sup 3 +/, Hg/sup 2 +/, Ni/sup 2 +/, Th/sup 4 +/, or UO/sub 2//sup 2 +/ with a metal-to-acid ratio of < 2.5. The method is suitable for determination of 10 ..mu..moles acid in 10 mL total volume. The accuracy can be judged from the agreement of the Nernst slopes found in the presence and absence of hydrolyzable ions. The relative standard deviation is < 2.5%. The report includes a survey of experiments with thermometric, pH, and Gran plot titrations in a variety of complexants, from which the method was evolved. Also included is a literature survey of sixty references, a discussion of the basic measurements, and a complete analytical procedure.

  5. Biochemical Titration of Glycogen In vitro

    PubMed Central

    Pelletier, Joffrey; Bellot, Grégory; Pouysségur, Jacques; Mazure, Nathalie M.

    2013-01-01

    Glycogen is the main energetic polymer of glucose in vertebrate animals and plays a crucial role in whole body metabolism as well as in cellular metabolism. Many methods to detect glycogen already exist but only a few are quantitative. We describe here a method using the Abcam Glycogen assay kit, which is based on specific degradation of glycogen to glucose by glucoamylase. Glucose is then specifically oxidized to a product that reacts with the OxiRed probe to produce fluorescence. Titration is accurate, sensitive and can be achieved on cell extracts or tissue sections. However, in contrast to other techniques, it does not give information about the distribution of glycogen in the cell. As an example of this technique, we describe here the titration of glycogen in two cell lines, Chinese hamster lung fibroblast CCL39 and human colon carcinoma LS174, incubated in normoxia (21% O2) versus hypoxia (1% O2). We hypothesized that hypoxia is a signal that prepares cells to synthesize and store glycogen in order to survive1. PMID:24300406

  6. A novel approach for high precision rapid potentiometric titrations: Application to hydrazine assay

    NASA Astrophysics Data System (ADS)

    Sahoo, P.; Malathi, N.; Ananthanarayanan, R.; Praveen, K.; Murali, N.

    2011-11-01

    We propose a high precision rapid personal computer (PC) based potentiometric titration technique using a specially designed mini-cell to carry out redox titrations for assay of chemicals in quality control laboratories attached to industrial, R&D, and nuclear establishments. Using this technique a few microlitre of sample (50-100 μl) in a total volume of ˜2 ml solution can be titrated and the waste generated after titration is extremely low comparing to that obtained from the conventional titration technique. The entire titration including online data acquisition followed by immediate offline analysis of data to get information about concentration of unknown sample is completed within a couple of minutes (about 2 min). This facility has been created using a new class of sensors, viz., pulsating sensors developed in-house. The basic concept in designing such instrument and the salient features of the titration device are presented in this paper. The performance of the titration facility was examined by conducting some of the high resolution redox titrations using dilute solutions--hydrazine against KIO3 in HCl medium, Fe(II) against Ce(IV) and uranium using Davies-Gray method. The precision of titrations using this innovative approach lies between 0.048% and 1.0% relative standard deviation in different redox titrations. With the evolution of this rapid PC based titrator it was possible to develop a simple but high precision potentiometric titration technique for quick determination of hydrazine in nuclear fuel dissolver solution in the context of reprocessing of spent nuclear fuel in fast breeder reactors.

  7. A Low-Cost Device for Automatic Photometric Titrations

    NASA Astrophysics Data System (ADS)

    Rocha, Fábio R. P.; Reis, Boaventura F.

    2000-02-01

    Electronics is an important topic in chemistry courses. However, the introduction of basic concepts is often difficult and the lab instruments are frequently seen as "black boxes". To address this problem, we propose the construction of a simple, low-cost (about $150 U.S.) automatic photometric titrator employing a light-emitting diode (LED) and a phototransistor. The electronic circuit can be assembled by the students themselves. The device was employed to implement a common procedure in chemical labs, making feasible the introduction of concepts related to electronics in undergraduate chemistry courses. The titrator is able to work automatically, since a feedback system permits stopping the addition of titrant solution when the end-point is achieved. With this demonstration, it can be stressed that automatic procedures can be implemented without expensive instruments. Additionally, a classical procedure becomes more attractive to the students and its importance to chemical analysis can be emphasized. The feasibility of the titrator was demonstrated by acid-base titrations of HCl solutions with NaOH in the presence of phenolphthalein and by iodimetric determination of ascorbic acid in vitamin C tablets and lemon juice. Precise results (0.7% relative standard deviation, n = 10) in agreement at the 95% confidence level with those attained by a conventional procedure were obtained.

  8. Determination of manganese in grain by potential titration with catalytic end-point indication.

    PubMed

    Xuezhi, D; Deliang, L; Chunshan, C; Jingwei, Z

    1999-12-01

    A method of catalytic potential titration for the determination of trace manganese by using crystal violet ion selective electrode is reported in this paper. It is based on the catalytic effect of manganese (II) on the oxidation of crystal violet by potassium periodate in the presence of nitrilotriacetic acid (NTA). The experiments indicated that this technique showed high sensitivity and high accuracy. The results of determination of trace manganese in grain could be compared with the results obtained by means of atomic absorption spectrometry. PMID:18967787

  9. Precipitation titration of perchlorate using new titrants

    SciTech Connect

    Selig, W.

    1980-05-01

    We have evaluated the following new titrants for the potentiometric precipitation titration of perchlorate: cetyltrimethylammonium chloride (CETAC), cetyltrimethylammonium bromide (CETAB), cetylpyridinium chloride (CPC), and benzyldimethyltetradecylammonium chloride (BDTAC). Titrations were monitored with a fluoroborate ion-selective electrode (ISE) and a double-junction reference electrode. The titration system was controlled by a Tektronix 4051 graphics system. The perchlorate, nitrate, and calcium ISE may also be used to monitor emf's. 7 tables, 2 figures.

  10. Risks and Benefits of Rapid Clozapine Titration

    PubMed Central

    Lochhead, Jeannie D.; Nelson, Michele A.; Schneider, Alan L.

    2016-01-01

    Clozapine is often considered the gold standard for the treatment of schizophrenia. Clinical guidelines suggest a gradual titration over 2 weeks to reduce the risks of adverse events such as seizures, hypotension, agranulocytosis, and myocarditis. The slow titration often delays time to therapeutic response. This raises the question of whether, in some patients, it may be safe to use a more rapid clozapine titration. The following case illustrates the potential risks associated with the use of multiple antipsychotics and rapid clozapine titration. We present the case of a young man with schizophrenia who developed life threatening neuroleptic malignant syndrome (NMS) during rapid clozapine titration and treatment with multiple antipsychotics. We were unable to find another case in the literature of NMS associated with rapid clozapine titration. This case is meant to urge clinicians to carefully evaluate the risks and benefits of rapid clozapine titration, and to encourage researchers to further evaluate the safety of rapid clozapine titration. Rapid clozapine titration has implications for decreasing health care costs associated with prolonged hospitalizations, and decreasing the emotional suffering associated with uncontrolled symptoms of psychosis. Clozapine is considered the most effective antipsychotic available thus efforts should focus on developing strategies that would allow for safest and most efficient use of clozapine to encourage its utilization for treatment resistance schizophrenia. PMID:27403276

  11. Molecular Titration Promotes Oscillations and Bistability in Minimal Network Models with Monomeric Regulators.

    PubMed

    Cuba Samaniego, Christian; Giordano, Giulia; Kim, Jongmin; Blanchini, Franco; Franco, Elisa

    2016-04-15

    Molecular titration is emerging as an important biochemical interaction mechanism within synthetic devices built with nucleic acids and the CRISPR/Cas system. We show that molecular titration in the context of feedback circuits is a suitable mechanism to enhance the emergence of oscillations and bistable behaviors. We consider biomolecular modules that can be inhibited or activated by input monomeric regulators; the regulators compete with constitutive titrating species to determine the activity of their target. By tuning the titration rate and the concentration of titrating species, it is possible to modulate the delay and convergence speed of the transient response, and the steepness and dead zone of the stationary response of the modules. These phenomena favor the occurrence of oscillations when modules are interconnected to create a negative feedback loop; bistability is favored in a positive feedback interconnection. Numerical simulations are supported by mathematical analysis showing that the capacity of the closed loop systems to exhibit oscillations or bistability is structural. PMID:26797494

  12. Determination of free acid by standard addition method in potassium thiocyanate

    SciTech Connect

    Not Available

    1981-06-01

    An analytical method for determination of free acidity in all SRP process solutions has been developed. Free acidity was successfully determined in solutions of nitric acid and the nitrates of aluminum, chromium(III), iron(III), mercury(II), nickel(II), thorium, and uranium(VI), at metal-to-acid ratios <2.5. Sample requirements, instrumentation, and mode of operation are similar to those currently used in the Laboratories Department free acid procedures. The simple procedure would be suitable for automation and microprocessor control. The method consists of two additions of known increments of acid into a solution containing the sample aliquot (10 ..mu..moles free acid) and 10 mL 1M potassium thiocyanate. The potential is determined in the initial solution and after each addition with a glass electrode and pH meter. The sample concentration is calculated by solution of three simultaneous Nernst equations. Two programs for this iterative computation are available: one written for the PDP-15 computer and another for a Hewlett-Packard 67 (or 97) programmable calculator. The accuracy of the result is verified by a slope that approximates the theoretical Nernst value. The relative standard deviation is <2.5%. This memorandum includes a survey of experiments with thermometric, pH, and Gran plot titrations in a variety of complexants, from which this particular system and technique logically evolved. The appendix includes a literature survey of sixty references, a discussion of the basic measurements, and a complete analytical procedure. The final step for completion of this RTA is training and consultation at the convenience of the Laboratories Department for demonstration of the method with process samples.

  13. Method for the production of dicarboxylic acids

    DOEpatents

    Nghiem, Nhuan Phu; Donnelly, Mark; Millard, Cynthia S.; Stols, Lucy

    1999-01-01

    The present invention is an economical fermentation method for the production of carboxylic acids comprising the steps of a) inoculating a medium having a carbon source with a carboxylic acid-producing organism; b) incubating the carboxylic acid-producing organism in an aerobic atmosphere to promote rapid growth of the organism thereby increasing the biomass of the organism; c) controllably releasing oxygen to maintain the aerobic atmosphere; d) controllably feeding the organism having increased biomass with a solution containing the carbon source to maintain the concentration of the carbon source within the medium of about 0.5 g/L up to about 1 g/L; e) depriving the aerobic atmosphere of oxygen to produce an anaerobic atmosphere to cause the organism to undergo anaerobic metabolism; f) controllably feeding the organism having increased biomass a solution containing the carbon source to maintain the concentration of the carbon source within the medium of .gtoreq.1 g/L; and g) converting the carbon source to carboxylic acids using the anaerobic metabolism of the organism.

  14. Method for the production of dicarboxylic acids

    DOEpatents

    Nghiem, N.P.; Donnelly, M.; Millard, C.S.; Stols, L.

    1999-02-09

    The present invention is an economical fermentation method for the production of carboxylic acids comprising the steps of (a) inoculating a medium having a carbon source with a carboxylic acid-producing organism; (b) incubating the carboxylic acid-producing organism in an aerobic atmosphere to promote rapid growth of the organism thereby increasing the biomass of the organism; (c) controllably releasing oxygen to maintain the aerobic atmosphere; (d) controllably feeding the organism having increased biomass with a solution containing the carbon source to maintain the concentration of the carbon source within the medium of about 0.5 g/l up to about 1 g/l; (e) depriving the aerobic atmosphere of oxygen to produce an anaerobic atmosphere to cause the organism to undergo anaerobic metabolism; (f) controllably feeding the organism having increased biomass a solution containing the carbon source to maintain the concentration of the carbon source within the medium of {>=}1 g/l; and (g) converting the carbon source to carboxylic acids using the anaerobic metabolism of the organism. 7 figs.

  15. Isothermal Titration Calorimetry Can Provide Critical Thinking Opportunities

    ERIC Educational Resources Information Center

    Moore, Dale E.; Goode, David R.; Seney, Caryn S.; Boatwright, Jennifer M.

    2016-01-01

    College chemistry faculties might not have considered including isothermal titration calorimetry (ITC) in their majors' curriculum because experimental data from this instrumental method are often analyzed via automation (software). However, the software-based data analysis can be replaced with a spreadsheet-based analysis that is readily…

  16. A Tabular Approach to Titration Calculations

    ERIC Educational Resources Information Center

    Lim, Kieran F.

    2012-01-01

    Titrations are common laboratory exercises in high school and university chemistry courses, because they are easy, relatively inexpensive, and they illustrate a number of fundamental chemical principles. While students have little difficulty with calculations involving a single titration step, there is a significant leap in conceptual difficulty…

  17. Development of highly sensitive cadmium iondashselective electrodes by titration method and its application to cadmium ion determination in industrial waste water.

    PubMed

    Ito, S; Asano, Y; Wada, H

    1997-04-01

    Characteristics of cadmium iondashselective electrode made cadmium sulphide (CdS)-silver sulphide (Ag(2)S) mixture were studied. CdS-Ag(2)S mixtures were obtained by gas/solid-phase reaction between silver-cadmium mixed powder and hydrogen sulphide gas (dry method) and by ionic reaction between cadmium-silver mixed ions and sulphide ion (wet method). As a result, it was found that the CdS-Ag(2)S mixture had to be made in the condition of excess existence of sulfur and had better regulate the excess sulfur quantity minimum, for the CdS-Ag(2)S pressed membrane gave a good Nernstian response against the cadmium ion concentration change. As the best way, CdS-Ag(2)S mixture was obtained by adding sulphide ion solution to 5 mol% cadmium ion and 95 mol% silver ion mixed solution while measuring silver sulphide (Ag(2)S) electrode potential as an indicator electrode. According to the reaction was stopped when the potential variation from the initial potential in the sulphide ion solution reached at 87-116 mV which the sulphide ion concentration became 10(-3) - 10(-4) of the initial concentration, the cadmium ion membrane pressed diameter of 8 mm and thickness of 2 mm showed a Nernstian response from 10(-8) to 10(-1) M of cadmium ion concentration. Furthermore, aiming to its application for industrial waste water, masking buffer for interfering metal ions such as lead ion (Pb(2+)) and copper ion (Cu(2+)), which were possibly coexisted and to adjust total ionic strength and pH of sample was developed. The present Cd(2+) iondashselective electrode was applied to the determination of Cd(2+) in the industrial waste water. The good regression line with correlation factor of 0.984 was obtained compared with the conventional atomic absorption spectroscopy. PMID:18966791

  18. Kinetics of bacterial potentiometric titrations: the effect of equilibration time on buffering capacity of Pantoea agglomerans suspensions.

    PubMed

    Kapetas, Leon; Ngwenya, Bryne T; Macdonald, Alan M; Elphick, Stephen C

    2011-07-15

    Several recent studies have made use of continuous acid-base titration data to describe the surface chemistry of bacterial cells as a basis for accurately modelling metal adsorption to bacteria and other biomaterials of potential industrial importance. These studies do not share a common protocol; rather they titrate in different pH ranges and they use different stability criteria to define equilibration time during titration. In the present study we investigate the kinetics of bacterial titrations and test the effect they have on the derivation of functional group concentrations and acidity constants. We titrated suspensions of Pantoea agglomerans by varying the equilibration time between successive titrant additions until stability of 0.1 or 0.001 mV s(-1) was attained. We show that under longer equilibration times, titration results are less reproducible and suspensions exhibit marginally higher buffering. Fluorescence images suggest that cell lysis is not responsible for these effects. Rather, high DOC values and titration reversibility hysterisis after long equilibration times suggest that variability in buffering is due to the presence of bacterial exudates, as demonstrated by titrating supernatants separated from suspensions of different equilibration times. It is recommended that an optimal equilibration time is always determined with variable stability control and preliminary reversibility titration experiments. PMID:21543082

  19. Improvement of end-point detection in the non-aqueous titration of sulphacetamide sodium.

    PubMed

    Soliman, S A; Belal, S; Bediar, M

    1984-04-01

    The sluggish end-point in the non-aqueous titration of sulphacetamide sodium in glacial acetic acid can be improved by addition of acetic anhydride to the titration medium, and selective determination of sulphacetamide sodium in presence of phenylephrine hydrochloride in eye drops then becomes possible. A mixture of sulphacetamide sodium and the antihistamine drug phenyltoloxamine dihydrogen citrate can also be analysed. PMID:18963589

  20. Method of increasing conversion of a fatty acid to its corresponding dicarboxylic acid

    DOEpatents

    Craft, David L.; Wilson, C. Ron; Eirich, Dudley; Zhang, Yeyan

    2004-09-14

    A nucleic acid sequence including a CYP promoter operably linked to nucleic acid encoding a heterologous protein is provided to increase transcription of the nucleic acid. Expression vectors and host cells containing the nucleic acid sequence are also provided. The methods and compositions described herein are especially useful in the production of polycarboxylic acids by yeast cells.

  1. Analytical method for determination of benzene-arsenic acids

    SciTech Connect

    Mitchell, G.L.; Bayse, G.S.

    1988-01-01

    A sensitive analytical method has been modified for use in determination of several benzenearsonic acids, including arsanilic acid (p-aminobenzenearsonic acid), Roxarsone (3-nitro-4-hydroxybenzenearsonic acid), and p-ureidobenzene arsonic acid. Controlled acid hydrolysis of these compounds produces a quantitative yield of arsenate, which is measured colorimetrically as the molybdenum blue complex at 865 nm. The method obeys Beer's Law over the micromolar concentration range. These benzenearsonic acids are routinely used as feed additives in poultry and swine. This method should be useful in assessing tissue levels of the arsenicals in appropriate extracts.

  2. Potentiometric titration of gold, platinum, and some other precious metals

    SciTech Connect

    Selig, W.S.

    1991-02-04

    Gold, platinum, and several other platinum metals can be determined by titration with cetylpyridinium chloride (CPC). CPC forms a precipitate with AuCl{sub 4}{sup {minus}} and PtCl{sub 6}{sup 2{minus}}. Differentiation of AuCl{sub 4{minus}} and PtCl{sub 6}{sup 2{minus}} with this titrant is not possible; however, their sum can be determined. Titration with tetraphenylarsonium chloride at pH 1 is selective for tetrachloroaurate, which thus can be determined in the presence of hexachloroplatinate. Hexachloroosmate(IV), tetrachloroplatinite(II), tetrachloropalladate(II), hexachloropalladate(IV), and hexachloroiridate(IV) can also be determined potentiometrically vs. CPC. The indicating electrode is prepared by coating a spectroscopic graphite rod with a solution of poly(vinyl chloride) (PVC) and dioctylphthalate (DOP) in tetrahydrofuran (THF). Gold in gold cyanide plating baths and in potassium aurocyanide can be determined by potentiometric titration vs standard silver nitrate, using a silver ion-selective indicating electrode. The monovalent gold need not be converted to the trivalent state with aqua regia, resulting in a considerable saving of time and effort. Free cyanide and aurocyanide can be titrated sequentially by this method. Chloride does not interfere and can, in fact, also be sequentially determined. 17 refs., 2 figs., 3 tabs.

  3. A hot-cell titration system

    SciTech Connect

    Klatt, L.N.

    1988-07-01

    Operation of nuclear fuel reprocessing plant requires an analytical support laboratory capable of meeting the process control, product quality, and nuclear safeguard requirements. Because of the radioactivity accompanying many of the samples, the analytical instruments must be selected, modified, or specifically developed for use in hot cells. Titrimetric procedures have been successfully used in hot cells and are generally immune to radiation induced bias. This report describes a titration system designed for operation in a hot-cell environment. The potentiometric titration system has operated successfully for four years in support of nuclear fuel reprocessing research and development activities. Details of the hardware, electronic, and software control and data analysis systems are presented. Interchangeable burets with a capacity of 5, 10, and 25 mL are available; the means of the absolute error in delivered volume for these burets are 0.9, 1.1, and 1.8 ..mu..L, respectively. Results of evaluation studies how that the accuracy and precision of analysis results obtained with the potentiometric system are limited by statistical uncertainties associated with the standard titrant, sample preparation procedure, and the equilibrium constant of the titration reaction and not by titrator performance factors. The system is also capable of performing amperometric titrations. Changing between the potentiometric and amperometric modes of operation involves changing the in-cell transducers, the in-cell electronics, and the titrator control program. 22 refs., 13 figs., 9 tabs.

  4. Subsite binding energies of an exo-polygalacturonase using isothermal titration calorimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thermodynamic parameters for binding of a series of galacturonic acid oligomers to an exo-polygalacturonase, RPG16 from Rhizopus oryzae, were determined by isothermal titration calorimetry. Binding of oligomers varying in chain length from two to five galacturonic acid residues is an exothermic proc...

  5. Volumetric determination of uranium using titanous sulfate as reductant before oxidimetric titration

    USGS Publications Warehouse

    Wahlberg, James S.; Skinner, Dwight L.; Rader, Lewis F.

    1956-01-01

    A new method for determining uranium in samples containing 0.05 percent or more U3O8, using titanous sulfate as reducing agent, is much shorter, faster, and has fewer interferences than conventional methods using reductor columns. The sample is dissolved with sulfuric, nitric, perchloric, and hydrofluoric acids. Elements that would otherwise form insoluble fluorides are kept in solution by complexing the fluoride ion with boric acid. A precipitation is made with cupferron to remove interfering elements. The solution is filtered to remove the precipitated cupferrates instead of extracting them with chloroform as is usually done. Filtration is preferred to extraction because any niobium that may be in solution forms an insoluble cupferrate that may be removed by filtering but is very difficult to extract with chloroform. Excess cupferron is destroyed by oxidizing with nitric and perchloric acids, and evaporating to dense fumes of sulfuric acid. The uranium is reduced to U(IV) by the addition of titanous sulfate, with cupric sulfate used as an indicator of the completeness of the reduction. Metallic copper is formed when all the uranium is reduced. The reduced copper is then reoxidized by the addition of mercuric perchlorate, an excess of ferric sulfate added, and the solution titrated immediately with standard ceric sulfate with ferroin as an indicator. Precision of the method compared favorable with methods in common use, both for uranium ores and for most types of uranium-rich materials.

  6. Method for nucleic acid isolation using supercritical fluids

    DOEpatents

    Nivens, D.E.; Applegate, B.M.

    1999-07-13

    A method is disclosed for detecting the presence of a microorganism in an environmental sample involves contacting the sample with a supercritical fluid to isolate nucleic acid from the microorganism, then detecting the presence of a particular sequence within the isolated nucleic acid. The nucleic acid may optionally be subjected to further purification. 4 figs.

  7. Method for nucleic acid isolation using supercritical fluids

    DOEpatents

    Nivens, David E.; Applegate, Bruce M.

    1999-01-01

    A method for detecting the presence of a microorganism in an environmental sample involves contacting the sample with a supercritical fluid to isolate nucleic acid from the microorganism, then detecting the presence of a particular sequence within the isolated nucleic acid. The nucleic acid may optionally be subjected to further purification.

  8. Unusual properties of crocodilian ovomacroglobulin shown in its methylamine treatment and sulfhydryl titration

    SciTech Connect

    Arakawa, H.; Osada, T.; Ikai, A.

    1986-02-01

    The inhibitory activity of chicken and crocodilian ovomacroglobulins against trypsin was measured before and after their incubation with methylamine. The result for crocodilian ovomacroglobulin showed that methylamine treatment destroyed half of its activity, in unique contrast to human alpha 2-macroglobulin and chicken ovomacroglobulin for which methylamine either destroys the inhibitory activity of the former completely or does not affect that of the latter at all. Free sulfhydryl groups of chicken and crocodilian ovomacroglobulins were titrated with 5,5'-dithiobis(2-nitrobenzoic acid) before and after incubation with trypsin. Prior to the incubation with trypsin the chicken and crocodilian proteins respectively had 0 and 1 titratable sulfhydryl per molecule of Mr 720,000. After treatment with trypsin the crocodilian protein had 3.5-4 titratable sulfhydryls, whereas there were no titratable sulfhydryls in the chicken protein. After denaturation of the crocodilian protein in sodium dodecyl sulfate at 100 degrees C the number of titratable sulfhydryls was 4. Chicken ovomacroglobulin again did not have an appreciable number of titratable sulfhydryls under similar denaturing conditions. Incubation of crocodilian protein with (14C)methylamine showed an incorporation of at least 2 mol of methylamine per molecule. The result indicated the presence of three intramolecular thiol ester bonds in crocodilian ovomacroglobulin with differential stability against external perturbations.

  9. Use of the ion exchange method for the determination of stability constants of trivalent metal complexes with humic and fulvic acids--part I: Eu3+ and Am3+ complexes in weakly acidic conditions.

    PubMed

    Wenming, Dong; Hongxia, Zhang; Meide, Huang; Zuyi, Tao

    2002-06-01

    The conditional stability constants for tracer concentrations of Eu(III) and Am(III) with a red earth humic acid (REHA), a red earth fulvic acid (REFA) and a fulvic acid from weathered coal (WFA) were determined at pH 5.2-6.4 (such values are similar to those in non-calcareous soils) in the presence of HAc/NaAc or NaNO3 by using the cation exchange method. It was found that 1:1 complexes were predominately formed in weakly acidic conditions. The total exchangeable proton capacities and the degrees of dissociation of these humic substances were determined by using a potentiometric titration method. The key parameters necessary for the experimental determination of the conditional stability constants of metal ions with humic substances in weakly acidic conditions by using the cation exchange method were discussed. The conditional stability constants of 1:1 complexes obtained in this paper were compared with the literature data of Am(III) determined by using the ion exchange method and the solvent extraction method and with the stability constants of 1:1 complexes of UO2(2+) and Th4+ with the same soil humic substances. These results indicate the great stability of bivalent UO2(2+), trivalent Eu3+, Am3+ and tetravalent Th4+ complexes with humic and fulvic acids in weakly acidic conditions. PMID:12102358

  10. Method for identifying and quantifying nucleic acid sequence aberrations

    DOEpatents

    Lucas, Joe N.; Straume, Tore; Bogen, Kenneth T.

    1998-01-01

    A method for detecting nucleic acid sequence aberrations by detecting nucleic acid sequences having both a first and a second nucleic acid sequence type, the presence of the first and second sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. The method uses a first hybridization probe which includes a nucleic acid sequence that is complementary to a first sequence type and a first complexing agent capable of attaching to a second complexing agent and a second hybridization probe which includes a nucleic acid sequence that selectively hybridizes to the second nucleic acid sequence type over the first sequence type and includes a detectable marker for detecting the second hybridization probe.

  11. Method for identifying and quantifying nucleic acid sequence aberrations

    DOEpatents

    Lucas, J.N.; Straume, T.; Bogen, K.T.

    1998-07-21

    A method is disclosed for detecting nucleic acid sequence aberrations by detecting nucleic acid sequences having both a first and a second nucleic acid sequence type, the presence of the first and second sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. The method uses a first hybridization probe which includes a nucleic acid sequence that is complementary to a first sequence type and a first complexing agent capable of attaching to a second complexing agent and a second hybridization probe which includes a nucleic acid sequence that selectively hybridizes to the second nucleic acid sequence type over the first sequence type and includes a detectable marker for detecting the second hybridization probe. 11 figs.

  12. Continuous-flow free acid monitoring method and system

    DOEpatents

    Strain, J.E.; Ross, H.H.

    1980-01-11

    A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

  13. Continuous-flow free acid monitoring method and system

    DOEpatents

    Strain, James E.; Ross, Harley H.

    1981-01-01

    A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

  14. Comparison of polarimetry and crown ether-based HPLC chiral stationary phase method to determine (L)-amino acid optical purity.

    PubMed

    Lee, Mee Sung; Khan, F Nawaz; Shin, Sung Chul; Jeong, Euh Duck; Kim, Hae Gyeong; Kim, Mi Jin; Cho, Yoon Jae; Cha, Jae-Young; Hyun, Myung Ho; Jin, Jong Sung

    2012-11-15

    Although various pharmacopoeias provide titration methods to assay (L)-amino acid content, none of these methods distinguish between (L)- and (D)-amino acids and do not consider the presence of enantiomeric impurities. Consequently, these methods are limited in scope to describe the relationship between content and specific rotation, [α]. In this study, the US Pharmacopoeia method was compared with the crown ether-based high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) method to determine (L)-amino acid content and specific rotation. The (L)-amino acid content specified by the US Pharmacopoeia method was not consistent with the specific rotation in the presence of enantiomeric impurities, whereas the HPLC-CSP method was very effective for determining the (L)-amino acid content and the optical purity. The other advantage is that the HPLC-CSP method requires amino acid samples of quite low concentration (as low as 1 μg/mL), whereas the pharmacopoeia method requires higher concentrations (20-110 mg/mL). PMID:22868097

  15. Methods of refining and producing isomerized fatty acid esters and fatty acids from natural oil feedstocks

    DOEpatents

    Snead, Thomas E.; Cohen, Steven A.; Gildon, Demond L.; Beltran, Leslie V.; Kunz, Linda A.; Pals, Tessa M.; Quinn, Jordan R; Behrends, Jr., Raymond T.; Bernhardt, Randal J.

    2016-07-05

    Methods are provided for refining natural oil feedstocks and producing isomerized esters and acids. The methods comprise providing a C4-C18 unsaturated fatty ester or acid, and isomerizing the fatty acid ester or acid in the presence of heat or an isomerization catalyst to form an isomerized fatty ester or acid. In some embodiments, the methods comprise forming a dibasic ester or dibasic acid prior to the isomerizing step. In certain embodiments, the methods further comprise hydrolyzing the dibasic ester to form a dibasic acid. In certain embodiments, the olefin is formed by reacting the feedstock in the presence of a metathesis catalyst under conditions sufficient to form a metathesized product comprising olefins and esters, separating the olefins from the esters in the metathesized product, and transesterifying the esters in the presence of an alcohol to form a transesterified product having unsaturated esters.

  16. Titrating and evaluating multi-drug regimens within subjects.

    PubMed

    Shih, Margaret; Gennings, Chris; Chinchilli, Vernon M; Carter, Walter H

    2003-07-30

    The dosing of combination therapies is commonly undertaken empirically by practising physicians, and a coherent algorithm to approach the problem of combination dosing is currently lacking. Current methods of evaluating multiple drug combinations in clinical trials fail to provide information regarding the location of more effective doses when the combination is not found to differ from the standard, even though the absence of a difference does not necessarily mean the new combination is ineffective. Moreover, in studies where the new combination is found more effective, often a large proportion of the study participants obtain no benefit from the trial. Even with early stopping rules, the time these subjects spend on inferior treatments can have lasting detrimental effects, leading to problems with patient enrolment and adherence to study protocol. This paper describes an evolutionary operation (EVOP) direct-search procedure to titrate combination doses within individual patients. The Nelder-Mead simplex direct-search algorithm is used to titrate combinations of drugs within individual subjects. Desirability functions are utilized to define the main response of interest and additional responses or constraints. Statistical methodology for determining whether the titrated treatment combination has resulted in an improvement in subject response and for evaluating for therapeutic synergism is developed. Inferences can then be made about the efficacy of the combination or about the individual drugs that comprise the combination. The advantages of this approach include affording every patient the potential to benefit from the combination under study and permitting the consideration of multiple endpoints simultaneously. PMID:12854092

  17. Sulfuric acid thermoelectrochemical system and method

    DOEpatents

    Ludwig, Frank A.

    1989-01-01

    A thermoelectrochemical system in which an electrical current is generated between a cathode immersed in a concentrated sulfuric acid solution and an anode immersed in an aqueous buffer solution of sodium bisulfate and sodium sulfate. Reactants consumed at the electrodes during the electrochemical reaction are thermochemically regenerated and recycled to the electrodes to provide continuous operation of the system.

  18. Method for the separation of acid from acid-laden vapors

    SciTech Connect

    Hansen, L.J.

    1992-02-11

    This patent describes a method for the removal of hydrochloric or sulfuric acid from vapor laden with the acid. It comprises: contacting the acid-laden vapors with packing materials in a zone containing the packing materials wherein the packing materials are formed of polyester resin containing from about 5 to 40 weight percent aluminum sulfate crystals.

  19. Isothermal Titration Calorimetry in the Student Laboratory

    ERIC Educational Resources Information Center

    Wadso, Lars; Li, Yujing; Li, Xi

    2011-01-01

    Isothermal titration calorimetry (ITC) is the measurement of the heat produced by the stepwise addition of one substance to another. It is a common experimental technique, for example, in pharmaceutical science, to measure equilibrium constants and reaction enthalpies. We describe a stirring device and an injection pump that can be used with a…

  20. Virtual Titrator: A Student-Oriented Instrument.

    ERIC Educational Resources Information Center

    Ritter, David; Johnson, Michael

    1997-01-01

    Describes a titrator system, constructed from a computer-interfaced pH-meter, that was designed to increase student involvement in the process. Combines automatic data collection with real-time graphical display and interactive controls to focus attention on the process rather than on bits of data. Improves understanding of concepts and…

  1. Boron containing amino acid compounds and methods for their use

    SciTech Connect

    Glass, J.D.; Coderre, J.A.

    2000-01-25

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  2. Boron containing amino acid compounds and methods for their use

    DOEpatents

    Glass, John D.; Coderre, Jeffrey A.

    2000-01-01

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  3. Acid-base properties of titanium-antimony oxides catalysts

    SciTech Connect

    Zenkovets, G.A.; Paukshtis, E.A.; Tarasova, D.V.; Yurchenko, E.N.

    1982-06-01

    The acid-base properties of titanium-antimony oxide catalysts were studied by the methods of back titration and ir spectroscopy. The interrelationship between the acid-base and catalytic properties in the oxidative ammonolysis of propylene was discussed. 3 figures, 1 table.

  4. Mutant fatty acid desaturase and methods for directed mutagenesis

    DOEpatents

    Shanklin, John; Whittle, Edward J.

    2008-01-29

    The present invention relates to methods for producing fatty acid desaturase mutants having a substantially increased activity towards substrates with fewer than 18 carbon atom chains relative to an unmutagenized precursor desaturase having an 18 carbon chain length specificity, the sequences encoding the desaturases and to the desaturases that are produced by the methods. The present invention further relates to a method for altering a function of a protein, including a fatty acid desaturase, through directed mutagenesis involving identifying candidate amino acid residues, producing a library of mutants of the protein by simultaneously randomizing all amino acid candidates, and selecting for mutants which exhibit the desired alteration of function. Candidate amino acids are identified by a combination of methods. Enzymatic, binding, structural and other functions of proteins can be altered by the method.

  5. Method for Enzyme Design with Genetically Encoded Unnatural Amino Acids.

    PubMed

    Hu, C; Wang, J

    2016-01-01

    We describe the methodologies for the design of artificial enzymes with genetically encoded unnatural amino acids. Genetically encoded unnatural amino acids offer great promise for constructing artificial enzymes with novel activities. In our studies, the designs of artificial enzyme were divided into two steps. First, we considered the unnatural amino acids and the protein scaffold separately. The scaffold is designed by traditional protein design methods. The unnatural amino acids are inspired by natural structure and organic chemistry methods, and synthesized by either organic chemistry methods or enzymatic conversion. With the increasing number of published unnatural amino acids with various functions, we described an unnatural amino acids toolkit containing metal chelators, redox mediators, and click chemistry reagents. These efforts enable a researcher to search the toolkit for appropriate unnatural amino acids for the study, rather than design and synthesize the unnatural amino acids from the beginning. After the first step, the model enzyme was optimized by computational methods and directed evolution. Lastly, we describe a general method for evolving aminoacyl-tRNA synthetase and expressing unnatural amino acids incorporated into a protein. PMID:27586330

  6. Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations

    NASA Astrophysics Data System (ADS)

    Ebling, A. M.; Schijf, J.

    2008-12-01

    In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and

  7. Gallic Acid: Review of the Methods of Determination and Quantification.

    PubMed

    Fernandes, Felipe Hugo Alencar; Salgado, Hérida Regina Nunes

    2016-05-01

    Gallic acid (3,4,5 trihydroxybenzoic acid) is a secondary metabolite present in most plants. This metabolite is known to exhibit a range of bioactivities including antioxidant, antimicrobial, anti-inflammatory, and anticancer. There are various methods to analyze gallic acid including spectrometry, chromatography, and capillary electrophoresis, among others. They have been developed to identify and quantify this active ingredient in most biological matrices. The aim of this article is to review the available information on analytical methods for gallic acid, as well as presenting the advantages and limitations of each technique. PMID:26440222

  8. Determination of vanadium(V) by direct automatic potentiometric titration with EDTA using a chemically modified electrode as a potentiometric sensor.

    PubMed

    Quintar, S E; Santagata, J P; Cortinez, V A

    2005-10-15

    A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure. The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste. Automatic potentiometric titration curves were obtained for V(V) within 5 x 10(-5) to 2 x 10(-3)M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prosthesis. PMID:18970248

  9. Compositions and method for controlling precipitation when acidizing sour wells

    SciTech Connect

    Dill, W.R.; Walker, M.L.

    1990-08-21

    This patent describes a method of treating a sour well penetrating a subterranean formation. It comprises: introducing into the well a treating fluid comprising an acid solution having a pH below 1.9, an iron sequestering agent comprising at least one compound selected from the group consisting of aminopolycarboxylic acids, hydroxycarboxylic acids, cyclic polyethers and derivatives of the acids and ethers, present in an amount of from about 0.25 to about 5 percent by weight of the acid solution, and a sulfide modifier comprising at least one compound selected from the group consisting of an aldehyde, acetal, hemiacetal and any other compound capable of forming aldehydes in the acid solution, present in an amount of from about 0.25 to about 5 percent of the acid solution; and treating the subterranean formation with the treating fluid.

  10. A titration model for evaluating calcium hydroxide removal techniques

    PubMed Central

    PHILLIPS, Mark; McCLANAHAN, Scott; BOWLES, Walter

    2015-01-01

    Objective Calcium hydroxide (Ca(OH)2) has been used in endodontics as an intracanal medicament due to its antimicrobial effects and its ability to inactivate bacterial endotoxin. The inability to totally remove this intracanal medicament from the root canal system, however, may interfere with the setting of eugenol-based sealers or inhibit bonding of resin to dentin, thus presenting clinical challenges with endodontic treatment. This study used a chemical titration method to measure residual Ca(OH)2 left after different endodontic irrigation methods. Material and Methods Eighty-six human canine roots were prepared for obturation. Thirty teeth were filled with known but different amounts of Ca(OH)2 for 7 days, which were dissolved out and titrated to quantitate the residual Ca(OH)2 recovered from each root to produce a standard curve. Forty-eight of the remaining teeth were filled with equal amounts of Ca(OH)2 followed by gross Ca(OH)2 removal using hand files and randomized treatment of either: 1) Syringe irrigation; 2) Syringe irrigation with use of an apical file; 3) Syringe irrigation with added 30 s of passive ultrasonic irrigation (PUI), or 4) Syringe irrigation with apical file and PUI (n=12/group). Residual Ca(OH)2 was dissolved with glycerin and titrated to measure residual Ca(OH)2 left in the root. Results No method completely removed all residual Ca(OH)2. The addition of 30 s PUI with or without apical file use removed Ca(OH)2 significantly better than irrigation alone. Conclusions This technique allowed quantification of residual Ca(OH)2. The use of PUI (with or without apical file) resulted in significantly lower Ca(OH)2 residue compared to irrigation alone. PMID:25760272

  11. Human jagged polypeptide, encoding nucleic acids and methods of use

    DOEpatents

    Li, Linheng; Hood, Leroy

    2000-01-01

    The present invention provides an isolated polypeptide exhibiting substantially the same amino acid sequence as JAGGED, or an active fragment thereof, provided that the polypeptide does not have the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:6. The invention further provides an isolated nucleic acid molecule containing a nucleotide sequence encoding substantially the same amino acid sequence as JAGGED, or an active fragment thereof, provided that the nucleotide sequence does not encode the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:6. Also provided herein is a method of inhibiting differentiation of hematopoietic progenitor cells by contacting the progenitor cells with an isolated JAGGED polypeptide, or active fragment thereof. The invention additionally provides a method of diagnosing Alagille Syndrome in an individual. The method consists of detecting an Alagille Syndrome disease-associated mutation linked to a JAGGED locus.

  12. Determination of uranium in uranium metal, uranium oxides, and uranyl nitrate solutions by potentiometric titration

    SciTech Connect

    Tucker, H.L.; McElhaney, R.J.

    1983-01-01

    A simple, fast method for the determination of uranium in uranium metal, uranium oxides, and uranyl nitrate solutions has been adapted from the Davies-Gray volumetric method to meet the needs of Y-12. One-gram duplicate aliquots of uranium metal or uranium oxide are dissolved in 1:1 HNO/sub 3/ and concentrated H/sub 2/SO/sub 4/ to sulfur trioxide fumes, and then diluted to 100-mL volume. Duplicate aliquots are then weighed for analysis. For uranyl nitrate samples, duplicate aliquots containing between 50 and 150 mg of U are weighed and analyzed directly. The weighed aliquot is transferred to a Berzelius beaker; 1.5 M sulfamic acid is added, followed in order by concentrated phosphoric acid, 1 M ferrous sulfate, and (after a 30-second interval) the oxidizing reagent. After a timed 3-minute waiting period, 100 mL of the 0.1% vanadyl sulfate-sulfuric acid mixture is added. The sample is then titrated past its endpoint with standard potassium dichromate, and the endpoint is determined by second derivative techniques on a mV/weight basis.

  13. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, Gary A [Kennewick, WA; Smith, Jeffrey W [Lancaster, OH; Ihle, Nathan C [Walla Walla, WA

    1984-01-01

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH).sub.2 to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with portland cement to form concrete.

  14. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, G.A.; Smith, J.W.; Ihle, N.C.

    1982-07-08

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH)/sub 2/ to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with Portland cement to form concrete.

  15. The influence of mechanochemical modification on prevention of toxic ability of humic acids towards phenanthrene in aquatic environment

    NASA Astrophysics Data System (ADS)

    Shekhovtsova, N. S.; Maltseva, E. V.; Glyzina, T. S.; Ovchinnikova, I. S.

    2015-11-01

    The aim of the research work is to quantify interaction between phenanthrene with modified humic acids in aquatic environment. The changes in the structure and properties of humic acids after modifications were studied with 1H NMR spectroscopy and potentiometric titration methods. Our research demonstrates that the application of thiourea as a modified agent increases the binding capacity of humic acids towards phenanthrene.

  16. A monosegmented-flow Karl Fischer titrator.

    PubMed

    de Aquino, Emerson Vidal; Rohwedder, Jarbas José Rodrigues; Pasquini, Celio

    2007-02-28

    A monosegmented volumetric Karl Fischer titrator is described to mechanize the determination of water content in organic solvents. The system is based on the flow-batch characteristics of the monosegmented analysis concept and employs biamperometry to monitor the progress of the titration. The system shows accuracy and precision that are highly independent of the flow rate, does not require calibration, and is carried out in a closed system capable of minimizing contact of the sample and reagents with ambient moisture. Sample volumes in the range of 40-300muL are employed, depending on the water concentration. An automatic dilution is provided to deal with concentrated samples. The consumption of Karl Fischer reagent depends on the water content of the sample but is not larger than 100muL. The system was evaluated for determination of water in ethanol and methanol in the range 0.02-0.5% (w/w). The average relative precision estimated in that range (9-3%) is comparable to that obtained with a larger volume commercial system and no significant difference was observed between the results obtained for the two systems at the 95% confidence level. A complete titration can be performed in less than 5min employing the proposed system. PMID:19071447

  17. Modified semiautomated method for free fatty acids in serum.

    PubMed Central

    Crane, B; Lane, C

    1977-01-01

    Modifications have been made to the reagent system of the semiautomated method for the determination of plasma free fatty acids by Baird et al. (1967), and results are reported of investigations into parameters affecting sensitivity and analytical range. PMID:599188

  18. Method for producing iron-based acid catalysts

    SciTech Connect

    Farcasiu, M.; Kathrein, H.; Kaufman, P.B.; Diehl, J.R.

    1998-04-01

    A method for preparing an acid catalyst with a long shelf-life is described. Crystalline iron oxides are doped with lattice compatible metals which are heated with halogen compounds at elevated temperatures.

  19. Method for protecting plant life from acidic atmospheric pollutants

    SciTech Connect

    Lengyel, A.D.

    1986-10-14

    A method is described for treating a stand of coniferous trees growing by natural processes and exposed to an atmosphere containing inorganic nitric acid or nitrate compounds to improve the resistance of the trees to damage by acid rain. The method consists of foliarly applying at least one sugar selected from the group consisting of monosaccharides and disaccharides to the coniferous trees naturally growing in the stand exposed to the atmosphere.

  20. Methods and compositions for efficient nucleic acid sequencing

    DOEpatents

    Drmanac, Radoje

    2002-01-01

    Disclosed are novel methods and compositions for rapid and highly efficient nucleic acid sequencing based upon hybridization with two sets of small oligonucleotide probes of known sequences. Extremely large nucleic acid molecules, including chromosomes and non-amplified RNA, may be sequenced without prior cloning or subcloning steps. The methods of the invention also solve various current problems associated with sequencing technology such as, for example, high noise to signal ratios and difficult discrimination, attaching many nucleic acid fragments to a surface, preparing many, longer or more complex probes and labelling more species.

  1. Methods and compositions for efficient nucleic acid sequencing

    DOEpatents

    Drmanac, Radoje

    2006-07-04

    Disclosed are novel methods and compositions for rapid and highly efficient nucleic acid sequencing based upon hybridization with two sets of small oligonucleotide probes of known sequences. Extremely large nucleic acid molecules, including chromosomes and non-amplified RNA, may be sequenced without prior cloning or subcloning steps. The methods of the invention also solve various current problems associated with sequencing technology such as, for example, high noise to signal ratios and difficult discrimination, attaching many nucleic acid fragments to a surface, preparing many, longer or more complex probes and labelling more species.

  2. High concentration aqueous sodium fluoride certified reference materials for forensic use certified by complexometric titration.

    PubMed

    Archer, Marcellé; Brits, Martin; Prevoo-Franzsen, Désirée; Quinn, Laura

    2015-04-01

    Sodium fluoride in concentrations of 1 to 2 % is used to prevent the formation of ethanol in blood and urine samples that are to be analysed for ethanol content. The majority of such samples form part of forensic investigations into alleged drunken driving. In South Africa, the laboratory performing the tests is required to prove that the sodium fluoride concentration in the blood samples is above 1 g/100 ml on receipt. This is done by using a fluoride ion-selective electrode calibrated with external aqueous solutions of sodium fluoride. The National Metrology Institute of South Africa (NMISA) prepares sodium fluoride solutions in concentrations from 0.3 to 3.0 g/100 ml. No other certified sodium fluoride reference solutions in these concentrations are available commercially. The sodium fluoride is certified by precipitation of the fluoride as lead chlorofluoride (PbClF) through the addition of a known excess of lead nitrate. The excess lead is back-titrated with ethylenediamine tetraacetic acid (EDTA) using a photometric electrode to detect the endpoint. Aqueous sodium fluoride solutions are prepared and the concentrations verified by the precipitation/back-titration method. This paper shows the application of a classical complexometric method to the certification of reference materials and describes the procedures for the preparation of the sodium fluoride solutions, verification of the concentrations, homogeneity and stability by primary titrimetry. It also briefly covers the calculation of uncertainty, the establishment of traceability and the quality control measures applied to ensure the quality of the certified reference materials (CRMs). PMID:25326884

  3. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Provisions § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration... the potassium ferricyanide titration method for the determination of sulfide in wastewaters...

  4. New method for the estimation of platelet ascorbic acid

    PubMed Central

    Lloyd, J. V.; Davis, P. S.; Lander, Harry

    1969-01-01

    Present techniques for the estimation of platelet ascorbic acid allow interference by other substances in the sample. A new and more specific method of analysis is presented. The proposed method owes its increased specificity to resolution of the extract by thin-layer chromatography. By this means ascorbic acid is separated from other reducing substances present. The separated ascorbic acid is eluted from the thin layer and estimated by a new and very sensitive procedure: ascorbic acid is made to react with ferric chloride and the ferrous ions so formed are estimated spectrophotometrically by the coloured derivative which they form with tripyridyl-Striazine. Results obtained with normal blood platelets were consistently lower than simultaneous determinations by the dinitrophenylhydrazine (DNPH) method. PMID:5798633

  5. A rapid automated procedure for laboratory and shipboard spectrophotometric measurements of seawater alkalinity: continuously monitored single-step acid additions

    NASA Astrophysics Data System (ADS)

    Liu, X.; Byrne, R. H.; Lindemuth, M.; Easley, R. A.; Patsavas, M. C.

    2012-12-01

    An automated system for shipboard and laboratory alkalinity measurements is presented. The simple system, which consists of a Dosimat titrator to deliver acid volumetrically and a USB 4000 spectrophotometer to monitor the titration progress, provides fast, precise and accurate measurements of total alkalinity for oceanographic research. The analytical method is based on single-point HCl titrations of seawater samples of a known volume; bromol cresol purple is used as an indicator to determine the final pH. Field data from an Arctic cruise demonstrates accuracy and precision around 1 micro mol/kg and a sample processing rate of 6 min per sample.

  6. Phenol-Sulfuric Acid Method for Total Carbohydrates

    NASA Astrophysics Data System (ADS)

    Nielsen, S. Suzanne

    The phenol-sulfuric acid method is a simple and rapid colorimetric method to determine total carbohydrates in a sample. The method detects virtually all classes of carbohydrates, including mono-, di-, oligo-, and polysaccharides. Although the method detects almost all carbohydrates, the absorptivity of the different carbohydrates varies. Thus, unless a sample is known to contain only one carbohydrate, the results must be expressed arbitrarily in terms of one carbohydrate.

  7. Multiwavelength spectrophotometric determination of acidity constants of some azo dyes.

    PubMed

    Shamsipur, Mojtaba; Maddah, Bozorgmehr; Hemmateenejad, Bahram; Rouhani, Shohreh; Haghbeen, Kamaladin; Alizadeh, Kamal

    2008-06-01

    A multiwavelength spectrophotometric titration method was applied to study the acidity constants of some azo dyes in water. The UV-vis absorption spectra of azo dye solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated. The quantitative effects of the substituents on the acidity of the studied azo dyes were investigated by the linear free energy relationship (LFER) using Hammet sigma constant (sigma) and field and resonance effects of Kamlet and Taft (f and Re, respectively). PMID:17719268

  8. Multiwavelength spectrophotometric determination of acidity constants of some azo dyes

    NASA Astrophysics Data System (ADS)

    Shamsipur, Mojtaba; Maddah, Bozorgmehr; Hemmateenejad, Bahram; Rouhani, Shohreh; Haghbeen, Kamaladin; Alizadeh, Kamal

    2008-06-01

    A multiwavelength spectrophotometric titration method was applied to study the acidity constants of some azo dyes in water. The UV-vis absorption spectra of azo dye solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated. The quantitative effects of the substituents on the acidity of the studied azo dyes were investigated by the linear free energy relationship (LFER) using Hammet sigma constant ( σ) and field and resonance effects of Kamlet and Taft ( f and ℜ, respectively).

  9. Potentiometric/turbidometric titration of antiperspirant actives.

    PubMed

    Johnston, Clifford T; Hem, Stanley L; Guenin, Eric; Mattai, Jairajh; Afflito, John

    2003-01-01

    A titration procedure that simultaneously monitors the pH and turbidity of an antiperspirant solution during neutralization with sodium hydroxide was developed to characterize antiperspirant actives. Aluminum chloride, aluminum chlorohydrate (ACH), and aluminum zirconium glycine complex (AZG) gave distinctive pH/turbidity profiles. The activated forms of aluminum chlorohydrate (ACH') and aluminum zirconium glycine complex (AZG') produced more turbidity than the non-activated forms. On an equimolar basis, AZG' produced more turbidity than any of the antiperspirant actives tested. PMID:12715089

  10. A modified colorimetric method for phytic acid analysis in soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A quantitative, reproducible, and efficient phytic acid assay procedure is needed to screen breeding populations and support genetic studies in soybeans. The objective of this study was to modify the colorimetric Wade reagent method and compare the accuracy and applicability of this new method in de...

  11. Method to produce succinic acid from raw hydrolysates

    DOEpatents

    Donnelly, Mark I.; Sanville-Millard, Cynthia Y.; Nghiem, Nhuan Phu

    2004-06-01

    A method for producing succinic acid from industrial-grade hydrolysates is provided, comprising supplying an organism that contains mutations for the genes ptsG, pflB, and ldhA, allowing said organism to accumulate biomass, and allowing said organism to metabolize the hydrolysate. Also provided is a bacteria mutant characterized in that it produces succinic acid from substrate contained in industrial-grade hydrolysate in a ratio of between 0.6:1 and 1.3:1 succinic acid to substrate.

  12. Spectrophotometric method for the estimation of 6-aminopenicillanic acid.

    PubMed

    Shaikh, K; Talati, P G; Gang, D M

    1973-02-01

    A simple, rapid, and sensitive method is described whereby 6-aminopenicillanic acid can be spectrophotometrically determined in the presence of penicillins and their degradation products without prior separation. d-(+)-Glucosamine is used as reagent. The effect of such parameters as pH, temperature, and time of heating on the formation of the chromophore is described. The recommended range is from 25 to 250 mug of 6-aminopenicillanic acid. PMID:4364173

  13. Method for distinctive estimation of stored acidity forms in acid mine wastes.

    PubMed

    Li, Jun; Kawashima, Nobuyuki; Fan, Rong; Schumann, Russell C; Gerson, Andrea R; Smart, Roger St C

    2014-10-01

    Jarosites and schwertmannite can be formed in the unsaturated oxidation zone of sulfide-containing mine waste rock and tailings together with ferrihydrite and goethite. They are also widely found in process wastes from electrometallurgical smelting and metal bioleaching and within drained coastal lowland soils (acid-sulfate soils). These secondary minerals can temporarily store acidity and metals or remove and immobilize contaminants through adsorption, coprecipitation, or structural incorporation, but release both acidity and toxic metals at pH above about 4. Therefore, they have significant relevance to environmental mineralogy through their role in controlling pollutant concentrations and dynamics in contaminated aqueous environments. Most importantly, they have widely different acid release rates at different pHs and strongly affect drainage water acidity dynamics. A procedure for estimation of the amounts of these different forms of nonsulfide stored acidity in mining wastes is required in order to predict acid release rates at any pH. A four-step extraction procedure to quantify jarosite and schwertmannite separately with various soluble sulfate salts has been developed and validated. Corrections to acid potentials and estimation of acid release rates can be reliably based on this method. PMID:25178979

  14. Determination of quaternary ammonium compounds by potentiometric titration with an ionic surfactant electrode: single-laboratory validation.

    PubMed

    Price, Randi; Wan, Ping

    2010-01-01

    A potentiometric titration for determining the quaternary ammonium compounds (QAC) commonly found in antimicrobial products was validated by a single laboratory. Traditionally, QACs were determined by using a biphasic (chloroform and water) manual titration procedure. Because of safety considerations regarding chloroform, as well as the subjectivity of color indicator-based manual titration determinations, an automatic potentiometric titration procedure was tested with quaternary nitrogen product formulations. By using the Metrohm Titrando system coupled with an ionic surfactant electrode and an Ag/AgCl reference electrode, titrations were performed with various QAC-containing formulation products/matrixes; a standard sodium lauryl sulfate solution was used as the titrant. Results for the products tested are sufficiently reproducible and accurate for the purpose of regulatory product enforcement. The robustness of the method was measured by varying pH levels, as well as by comparing buffered versus unbuffered titration systems. A quantitation range of 1-1000 ppm quaternary nitrogen was established. Eight commercially available antimicrobial products covering a variety of matrixes were assayed; the results obtained were comparable to those obtained by the manual titration method. Recoveries of 94 to 104% were obtained for spiked samples. PMID:21140668

  15. A visual detection of protein content based on titration of moving reaction boundary electrophoresis.

    PubMed

    Wang, Hou-Yu; Guo, Cheng-Ye; Guo, Chen-Gang; Fan, Liu-Yin; Zhang, Lei; Cao, Cheng-Xi

    2013-04-24

    A visual electrophoretic titration method was firstly developed from the concept of moving reaction boundary (MRB) for protein content analysis. In the developed method, when the voltage was applied, the hydroxide ions in the cathodic vessel moved towards the anode, and neutralized the carboxyl groups of protein immobilized via highly cross-linked polyacrylamide gel (PAG), generating a MRB between the alkali and the immobilized protein. The boundary moving velocity (V(MRB)) was as a function of protein content, and an acid-base indicator was used to denote the boundary displacement. As a proof of concept, standard model proteins and biological samples were chosen for the experiments to study the feasibility of the developed method. The experiments revealed that good linear calibration functions between V(MRB) and protein content (correlation coefficients R>0.98). The experiments further demonstrated the following merits of developed method: (1) weak influence of non-protein nitrogen additives (e.g., melamine) adulterated in protein samples, (2) good agreement with the classic Kjeldahl method (R=0.9945), (3) fast measuring speed in total protein analysis of large samples from the same source, and (4) low limit of detection (0.02-0.15 mg mL(-1) for protein content), good precision (R.S.D. of intra-day less than 1.7% and inter-day less than 2.7%), and high recoveries (105-107%). PMID:23567122

  16. Purity of potassium hydrogen phthalate, determination with precision coulometric and volumetric titration--a comparison.

    PubMed

    Recknagel, Sebastian; Breitenbach, Martin; Pautz, Joachim; Lück, Detlef

    2007-09-19

    The mass fraction of potassium hydrogen phthalate (KHP) from a specific batch was certified as an acidimetric standard. Two different analytical methods on a metrological level were used to carry out certification analysis: precision constant current coulometric and volumetric titration with NaOH. It could be shown that with a commercial automatic titration system in combination with a reliable software for the end-point detection it is possible to produce equivalent results with the same accuracy in comparison to a definite method handled by a fundamental apparatus for traceable precision coulometry. Prerequisite for titrations are that a high number of single measurement are applied which are calibrated with a high precision certified reference material. PMID:17870288

  17. Dissociation constants of phosphoric acid in dimethylformamide-water mixtures at 298.15 K

    NASA Astrophysics Data System (ADS)

    Safonova, L. P.; Fadeeva, Yu. A.; Pryakhin, A. A.

    2009-10-01

    The dissociation constants of phosphoric acid (p K 1 and p K 2) in water-dimethylformamide (DMFA) mixtures (0-0.65 mole fractions of DMFA) were determined at 298.15 K by potentiometric titration. The extrapolation of these data to pure DMFA and the comparative calculation method were used to estimate the dissociation constants of the acid in DMFA.

  18. Fast and selective determination of total protein in milk powder via titration of moving reaction boundary electrophoresis.

    PubMed

    Guo, Cheng-ye; Wang, Hou-yu; Liu, Xiao-ping; Fan, Liu-yin; Zhang, Lei; Cao, Cheng-xi

    2013-05-01

    In this paper, moving reaction boundary titration (MRBT) was developed for rapid and accurate quantification of total protein in infant milk powder, from the concept of moving reaction boundary (MRB) electrophoresis. In the method, the MRB was formed by the hydroxide ions and the acidic residues of milk proteins immobilized via cross-linked polyacrylamide gel (PAG), an acid-base indicator was used to denote the boundary motion. As a proof of concept, we chose five brands of infant milk powders to study the feasibility of MRBT method. The calibration curve of MRB velocity versus logarithmic total protein content of infant milk powder sample was established based on the visual signal of MRB motion as a function of logarithmic milk protein content. Weak influence of nonprotein nitrogen (NPN) reagents (e.g., melamine and urea) on MRBT method was observed, due to the fact that MRB was formed with hydroxide ions and the acidic residues of captured milk proteins, rather than the alkaline residues or the NPN reagents added. The total protein contents in infant milk powder samples detected via the MRBT method were in good agreement with those achieved by the classic Kjeldahl method. In addition, the developed method had much faster measuring speed compared with the Kjeldahl method. PMID:23483553

  19. Titration of chaos with added noise

    PubMed Central

    Poon, Chi-Sang; Barahona, Mauricio

    2001-01-01

    Deterministic chaos has been implicated in numerous natural and man-made complex phenomena ranging from quantum to astronomical scales and in disciplines as diverse as meteorology, physiology, ecology, and economics. However, the lack of a definitive test of chaos vs. random noise in experimental time series has led to considerable controversy in many fields. Here we propose a numerical titration procedure as a simple “litmus test” for highly sensitive, specific, and robust detection of chaos in short noisy data without the need for intensive surrogate data testing. We show that the controlled addition of white or colored noise to a signal with a preexisting noise floor results in a titration index that: (i) faithfully tracks the onset of deterministic chaos in all standard bifurcation routes to chaos; and (ii) gives a relative measure of chaos intensity. Such reliable detection and quantification of chaos under severe conditions of relatively low signal-to-noise ratio is of great interest, as it may open potential practical ways of identifying, forecasting, and controlling complex behaviors in a wide variety of physical, biomedical, and socioeconomic systems. PMID:11416195

  20. Methods And Devices For Characterizing Duplex Nucleic Acid Molecules

    DOEpatents

    Akeson, Mark; Vercoutere, Wenonah; Haussler, David; Winters-Hilt, Stephen

    2005-08-30

    Methods and devices are provided for characterizing a duplex nucleic acid, e.g., a duplex DNA molecule. In the subject methods, a fluid conducting medium that includes a duplex nucleic acid molecule is contacted with a nanopore under the influence of an applied electric field and the resulting changes in current through the nanopore caused by the duplex nucleic acid molecule are monitored. The observed changes in current through the nanopore are then employed as a set of data values to characterize the duplex nucleic acid, where the set of data values may be employed in raw form or manipulated, e.g., into a current blockade profile. Also provided are nanopore devices for practicing the subject methods, where the subject nanopore devices are characterized by the presence of an algorithm which directs a processing means to employ monitored changes in current through a nanopore to characterize a duplex nucleic acid molecule responsible for the current changes. The subject methods and devices find use in a variety of applications, including, among other applications, the identification of an analyte duplex DNA molecule in a sample, the specific base sequence at a single nulceotide polymorphism (SNP), and the sequencing of duplex DNA molecules.

  1. A GC-ECD method for estimation of free and bound amino acids, gamma-aminobutyric acid, salicylic acid, and acetyl salicylic acid from Solanum lycopersicum (L.).

    PubMed

    Meher, Hari Charan; Gajbhiye, Vijay T; Singh, Ghanendra

    2011-01-01

    A gas chromatograph with electron capture detection method for estimation of selected metabolites--amino acids (free and bound), gamma-aminobutyric acid (GABA), salicylic acid (SA), and acetyl salicylic acid (ASA) from tomato--is reported. The method is based on nitrophenylation of the metabolites by 1-fluoro-2, 4-dinitrobenzene under aqueous alkaline conditions to form dinitophenyl derivatives. The derivatives were stable under the operating conditions of GC. Analysis of bound amino acids comprised perchloric acid precipitation of protein, alkylation (carboxymethylation) with iodoacetic acid, vapor-phase hydrolysis, and derivatization with 1-fluoro-2,4-dinitrobenzene in that order. The metabolites were resolved in 35 min, using a temperature-programmed run. The method is rapid, sensitive, and precise. It easily measured the typical amino acids (aspartate, asparagine, glutamate, glutamine, alanine, leucine, lysine, and phenylalanine) used for identification and quantification of a protein, resolved amino acids of the same mass (leucine and isoleucine), satisfactorily measured sulfur amino acid (methionine, cystine, and cysteine), and quantified GABA, SA, and ASA, as well. The developed method was validated for specificity, linearity, and precision. It has been applied and recommended for estimation of 25 metabolites from Solanum lycopersicum (L.). PMID:21391500

  2. A Simple and Universal Method for Making up Buffer Solutions.

    ERIC Educational Resources Information Center

    Dennison, Clive

    1988-01-01

    Uses a method which involves weighing out an amount of the appropriate weak acid or base and dissolving it in distilled water close to the final volume. Solution is then titrated with strong acid or base to give the desired pH. Provides three examples. (MVL)

  3. Method to attenuate U(VI) mobility in acidic waste plumes using humic acids.

    PubMed

    Wan, Jiamin; Dong, Wenming; Tokunaga, Tetsu K

    2011-03-15

    Acidic uranium (U) groundwater plumes have resulted from acid-extraction of plutonium during the Cold War and from U mining and milling operations. A sustainable method for in situ immobilization of U under acidic conditions is not yet available. Here, we propose to use humic acids (HAs) for in situ U immobilization in acidic waste plumes. Our laboratory batch experiments show that HA can adsorb onto aquifer sediments rapidly, strongly and practically irreversibly. Adding HA greatly enhanced U adsorption capacity to sediments at pH below 5.0. Our column experiments using historically contaminated sediments from the Savannah River Site under slow flow rates (120 and 12 m/year) show that desorption of U and HA were nondetectable over 100 pore-volumes of leaching with simulated acidic groundwaters. Upon HA-treatment, 99% of the contaminant [U] was immobilized at pH ≤ 4.5, compared to 5% and 58% immobilized in the control columns at pH 3.5 and 4.5, respectively. These results indicate that HA-treatment is a promising in situ remediation method for acidic U waste plumes. As a remediation reagent, HAs are resistant to biodegradation, cost-effective, nontoxic, and easily introducible to the subsurface. PMID:21319737

  4. A method to attenuate U(VI) mobility in acidic waste plumes using humic acids

    SciTech Connect

    Wan, J.; Dong, W.; Tokunaga, T.K.

    2011-02-01

    Acidic uranium (U) contaminated plumes have resulted from acid-extraction of plutonium during the Cold War and from U mining and milling operations. A sustainable method for in-situ immobilization of U under acidic conditions is not yet available. Here, we propose to use humic acids (HAs) for in-situ U immobilization in acidic waste plumes. Our laboratory batch experiments show that HA can adsorb onto aquifer sediments rapidly, strongly and practically irreversibly. Adding HA greatly enhanced U adsorption capacity to sediments at pH below 5.0. Our column experiments using historically contaminated sediments from the Savannah River Site under slow flow rates (120 and 12 m/y) show that desorption of U and HA were non-detectable over 100 pore-volumes of leaching with simulated acidic groundwaters. Upon HA-treatment, 99% of the contaminant [U] was immobilized at pH < 4.5, compared to 5% and 58% immobilized in the control columns at pH 3.5 and 4.5, respectively. These results demonstrated that HA-treatment is a promising in-situ remediation method for acidic U waste plumes. As a remediation reagent, HAs are resistant to biodegradation, cost effective, nontoxic, and easily introducible to the subsurface.

  5. THE AMPHOTERIC PROPERTIES OF SOME AMINO-ACIDS AND PEPTIDES.

    PubMed

    Eckweiler, H; Noyes, H M; Falk, K G

    1921-01-20

    The titration curves of solutions of glycine, alanine, alpha-ammo-butyric acid, leucine, glycyl-glycine, alanyl-glycine, alanyl-alanine, acetone, acetamide, urea, acetic acid, and aceturic acid were determined and some of the relations as dependent upon the chemical structures discussed. The isoelectric points of some of the amphoteric electrolytes were found experimentally. The definition of isoelectric point, its theoretical significance, and method of calculation were considered in some detail. PMID:19871865

  6. Dissecting electrostatic interactions in Bacillus circulans xylanase through NMR-monitored pH titrations.

    PubMed

    McIntosh, Lawrence P; Naito, Daigo; Baturin, Simon J; Okon, Mark; Joshi, Manish D; Nielsen, Jens E

    2011-09-01

    NMR-monitored pH titration curves of proteins provide a rich source of structural and electrostatic information. Although relatively straightforward to measure, interpreting pH-dependent chemical shift changes to obtain site-specific acid dissociation constants (pK (A) values) is challenging. In order to analyze the biphasic titrations exhibited by the side chain (13)C(γ) nuclei of the nucleophilic Glu78 and general acid/base Glu172 in Bacillus circulans xylanase, we have revisited the formalism for the ionization equilibria of two coupled acidic residues. In general, fitting NMR-monitored pH titration curves for such a system will only yield the two macroscopic pK (A) values that reflect the combined effects of both deprotonation reactions. However, through the use of mutations complemented with ionic strength-dependent measurements, we are able to extract the four microscopic pK (Ai) values governing the branched acid/base equilibria of Glu78 and Glu172 in BcX. These data, confirmed through theoretical calculations, help explain the pH-dependent mechanism of this model GH11 xylanase by demonstrating that the kinetically determined pK (A) values and hence catalytic roles of these two residues result from their electrostatic coupling. PMID:21947911

  7. A full automatic device for sampling small solution volumes in photometric titration procedure based on multicommuted flow system.

    PubMed

    Borges, Sivanildo S; Vieira, Gláucia P; Reis, Boaventura F

    2007-01-01

    In this work, an automatic device to deliver titrant solution into a titration chamber with the ability to determine the dispensed volume of solution, with good precision independent of both elapsed time and flow rate, is proposed. A glass tube maintained at the vertical position was employed as a container for the titrant solution. Electronic devices were coupled to the glass tube in order to control its filling with titrant solution, as well as the stepwise solution delivering into the titration chamber. The detection of the titration end point was performed employing a photometer designed using a green LED (lambda=545 nm) and a phototransistor. The titration flow system comprised three-way solenoid valves, which were assembled to allow that the steps comprising the solution container loading and the titration run were carried out automatically. The device for the solution volume determination was designed employing an infrared LED (lambda=930 nm) and a photodiode. When solution volume delivered from proposed device was within the range of 5 to 105 mul, a linear relationship (R = 0.999) between the delivered volumes and the generated potential difference was achieved. The usefulness of the proposed device was proved performing photometric titration of hydrochloric acid solution with a standardized sodium hydroxide solution and using phenolphthalein as an external indicator. The achieved results presented relative standard deviation of 1.5%. PMID:18317510

  8. A Full Automatic Device for Sampling Small Solution Volumes in Photometric Titration Procedure Based on Multicommuted Flow System

    PubMed Central

    Borges, Sivanildo S.; Vieira, Gláucia P.; Reis, Boaventura F.

    2007-01-01

    In this work, an automatic device to deliver titrant solution into a titration chamber with the ability to determine the dispensed volume of solution, with good precision independent of both elapsed time and flow rate, is proposed. A glass tube maintained at the vertical position was employed as a container for the titrant solution. Electronic devices were coupled to the glass tube in order to control its filling with titrant solution, as well as the stepwise solution delivering into the titration chamber. The detection of the titration end point was performed employing a photometer designed using a green LED (λ=545 nm) and a phototransistor. The titration flow system comprised three-way solenoid valves, which were assembled to allow that the steps comprising the solution container loading and the titration run were carried out automatically. The device for the solution volume determination was designed employing an infrared LED (λ=930 nm) and a photodiode. When solution volume delivered from proposed device was within the range of 5 to 105 μl, a linear relationship (R = 0.999) between the delivered volumes and the generated potential difference was achieved. The usefulness of the proposed device was proved performing photometric titration of hydrochloric acid solution with a standardized sodium hydroxide solution and using phenolphthalein as an external indicator. The achieved results presented relative standard deviation of 1.5%. PMID:18317510

  9. Method for preparing 6-.beta.-halopenicillanic acids

    DOEpatents

    Hansen, Erik I.; Kran-Nielsen, Mogens P.; Von Daehne, Welf

    1989-01-01

    The present invention relates to a new and improved method for the preparation of a compound of the formula I ##STR1## in which R stands for halogen, giving rise to high yields of substantially pure 6.beta.-halopenicillanic acids, obtained in one step.

  10. An equilibrium model for ligand-modified micellar-enhanced ultrafiltration. Selective separation of metal ions using iminoacetic substituted polyamines and a theoretical model for the titration behavior of polyamines

    SciTech Connect

    Dharmawardana, Udeni Rajaratna

    1992-01-01

    This thesis consists of three chapters. Chapter 1, An equilibrium model for ligand-modified micellar-enhanced ultrafiltration, describes a theoretical model and experimental investigations which used the semi-equilibrium-dialysis method with N-n-dodecyl iminodiacetic acid as the ligand. In Chapter 2, Selective separation of metal ions using iminoacetic substituted polyamines, polyamines with a substituted ligand group are synthesized and used in investigating selective separation of copper ions from aqueous solution. In Chapter 3, A theoretical model for the titration behavior of polyamines, a novel approach to explain the titration behavior of polymeric amines based on the binding behavior of counterions is described. The application of this study is to the investigation of inexpensive and efficient methods of industrial waste water treatment.

  11. Spectrophotometric methods for the evaluation of acidity constants-I Numerical methods for single equilibria.

    PubMed

    Asuero, A G; Navas, M J; Jiminez-Trillo, J L

    1986-02-01

    The spectrophotometric methods applicable to the numerical evaluation of acidity constants of monobasic acids are briefly reviewed. The equations are presented in a form suitable for easy calculation with a programmable pocket calculator. The aim of this paper is to cover a gap in the education analytical literature. PMID:18964064

  12. Estimation of free acid content in lanthanide salt solutions used for potentiometric determination of stability constant of lanthanide complexes with organic ligands

    SciTech Connect

    Zheltvai, T.I.; Tishchenko, M.A.

    1985-08-20

    This paper studies the possibility of alkalimetric titration of free acid after binding the metal ions by the disodium salt of ethylenediaminetetraacetic (complexone III). The proposed method of free acid determination in lanthanide salt solutions is very simple and helps to avoid gross methodical errors in works involving determination of stability constants of lanthanide complexes.

  13. Combining pH and electrical conductivity measurements to improve titrimetric methods to determine ammonia nitrogen, volatile fatty acids and inorganic carbon concentrations.

    PubMed

    Charnier, C; Latrille, E; Lardon, L; Miroux, J; Steyer, J P

    2016-05-15

    Volatile fatty acids (VFA), inorganic carbon (IC) and total ammonia nitrogen (TAN) are key variables in the current context of anaerobic digestion (AD). Accurate measurements like gas chromatography and infrared spectrometry have been developed to follow the concentration of these compounds but none of these methods are affordable for small AD units. Only titration methods answer the need for small plant monitoring. The existing methods accuracy was assessed in this study and reveals a lack of accuracy and robustness to control AD plants. To solve these issues, a new titrimetric device to estimate the VFA, IC and TAN concentrations with an improved accuracy was developed. This device named SNAC (System of titration for total ammonia Nitrogen, volatile fatty Acids and inorganic Carbon) has been developed combining the measurement of electrical conductivity and pH. SNAC were tested on 24 different plant samples in a range of 0-0.16 mol.L(-1) TAN, 0.01-0.21 mol.L(-1) IC and 0-0.04 mol.L(-1) VFA. The standard error was about 0.012 mol.L(-1) TAN, 0.015 mol.L(-1) IC and 0.003 mol.L(-1) VFA. The coefficient of determination R(2) between the estimated and reference data was 0.95, 0.94 and 0.95 for TAN, IC and VFA respectively. Using the same data, current methods based on key pH points lead to standard error more than 14.5 times higher on VFA and more than 1.2 times higher on IC. These results show that SNAC is an accurate tool to improve the management of AD plant. PMID:27010787

  14. Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment

    ERIC Educational Resources Information Center

    Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

    2012-01-01

    An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

  15. Potentiometric titration of bisarenechromium compounds with an ion-selective electrode

    SciTech Connect

    Gur'ev, I.A.; Gur'eva, Z.M.; Sankova, E.V.; Sirotkin, N.I.

    1986-06-10

    A liquid-membrane ion-selective electrode was developed for determining bisbenzene-chromium and its electrochemical and analytical characteristics studied. Methods have also been developed for determining bisarenechromium compounds in the industrial product and its waste waters by potentiometric titration with sodium tetraphenylborate solution.

  16. Determination of fluoride in potable waters by ion-exchange and potentiometric titration.

    PubMed

    Light, T S; Mannion, R F; Fletcher, K S

    1969-10-01

    A procedure is described for the accurate titration of fluoride at the 1 mg l . level in potable water. The procedure employs an ion-exchange step for concentration of fluoride and removal of interfering ions, and Tb(IV) as titrant. Precision and relative error of the method are both 1%. PMID:18960653

  17. Method comparison study for weak acid dissociation cyanide analysis.

    PubMed

    Evans, Joseph D; Thompson, Leslie; Clark, Patrick J; Beckman, Scott W

    2003-02-01

    Method comparison studies of two different methods for the analysis of weak acid dissociable (WAD) cyanide revealed analytical flaws and/or matrix interference problems with both procedures. EPA "draft" method 1677 using a Perstorp 3202 CN analyzer was compared to Standard Method 4500 CN I. It was discovered that the Perstorp analyzer produced more precise and more accurate results once appropriate and necessary procedural steps from the EPA draft method were modified. Comparison of these two methods, was based on "real world" samples collected from a mine-tailing solution. The mine-tailing solution contained high concentrations of cyanide and metals. Inconsistencies in method procedures were traced to sulfide interferences and high concentrations of WAD metals. Conclusions were based upon a large sample base collected from a mine site over a 90-day period. PMID:12630477

  18. Predicting proton titration in cationic micelle and bilayer environments

    SciTech Connect

    Morrow, Brian H.; Shen, Jana K.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.

    2014-08-28

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pK{sub a}’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pK{sub a} of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pK{sub a} of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  19. Predicting proton titration in cationic micelle and bilayer environments

    NASA Astrophysics Data System (ADS)

    Morrow, Brian H.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.; Shen, Jana K.

    2014-08-01

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pKa's in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pKa of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pKa of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  20. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment..., 2011 § 60.648 Optional procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas... dilute solutions are used. In principle, this method consists of titrating hydrogen sulfide in a...

  1. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment... procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas Engineers Handbook, Fuel.... In principle, this method consists of titrating hydrogen sulfide in a gas sample directly with...

  2. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment..., 2011 § 60.648 Optional procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas... dilute solutions are used. In principle, this method consists of titrating hydrogen sulfide in a...

  3. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment... procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas Engineers Handbook, Fuel.... In principle, this method consists of titrating hydrogen sulfide in a gas sample directly with...

  4. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment... procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas Engineers Handbook, Fuel.... In principle, this method consists of titrating hydrogen sulfide in a gas sample directly with...

  5. Acid pre-treatment method for in situ ore leaching

    DOEpatents

    Mallon, R.G.; Braun, R.L.

    1975-10-28

    An acid leaching method is described for the recovery of a desired element from a subterranean rubblized body of primary ore containing the element and also having associated therewith a carbonate mineral wherein the rubblized ore body is flooded with an aqueous acidic solution in order to release carbon dioxide from the associated carbonate mineral. After a substantial portion of the available carbon dioxide is released and removed from the ore body, as by venting to the atmosphere, an oxidizing gas is introduced into the flooded, rubblized ore to oxidize the ore and form an acid leach solution effective in the presence of the dissolved oxidizing gas to dissolve the ore and cause the desired element to go into solution. The leach solution is then circulated to the surface where the metal values are recovered therefrom.

  6. Titration of thiol groups in non-aqueous solvents.

    PubMed

    Verma, K K

    Thiols are titrated in acetone or dimethylformamide with sodium methoxide, employing visual end-point detection with Thymol Blue, Victoria Blue, p-hydroxyazobenzene or Azo Violet. Aromatic thiols are titrated in the presence of aliphatic thiols in acetone, with Thymol Blue as indicator. PMID:18961758

  7. Spectrophotometric Titration of a Mixture of Calcium and Magnesium.

    ERIC Educational Resources Information Center

    Fulton, Robert; And Others

    1986-01-01

    Describes a spectrophotometric titration experiment which uses a manual titration spectrophotometer and manually operated buret, rather than special instrumentation. Identifies the equipment, materials, and procedures needed for the completion of the experiment. Recommends the use of this experiment in introductory quantitative analysis…

  8. Quantitative Analysis of Sulfate in Water by Indirect EDTA Titration

    ERIC Educational Resources Information Center

    Belle-Oudry, Deirdre

    2008-01-01

    The determination of sulfate concentration in water by indirect EDTA titration is an instructive experiment that is easily implemented in an analytical chemistry laboratory course. A water sample is treated with excess barium chloride to precipitate sulfate ions as BaSO[subscript 4](s). The unprecipitated barium ions are then titrated with EDTA.…

  9. pH Static Titration: A Quasistatic Approach

    ERIC Educational Resources Information Center

    Michalowski, Tadeusz; Toporek, Marcin; Rymanowski, Maciej

    2007-01-01

    The pH-static titration is applicable to those systems where at least two types of reactions occur in comparable intensities. The commonalities in titrimetric procedure realized according to pH-static titration, irrespective of the kind of chemical processes occurring are discussed.

  10. Number of independent parameters in the potentiometric titration of humic substances.

    PubMed

    Lenoir, Thomas; Manceau, Alain

    2010-03-16

    With the advent of high-precision automatic titrators operating in pH stat mode, measuring the mass balance of protons in solid-solution mixtures against the pH of natural and synthetic polyelectrolytes is now routine. However, titration curves of complex molecules typically lack obvious inflection points, which complicates their analysis despite the high-precision measurements. The calculation of site densities and median proton affinity constants (pK) from such data can lead to considerable covariance between fit parameters. Knowing the number of independent parameters that can be freely varied during the least-squares minimization of a model fit to titration data is necessary to improve the model's applicability. This number was calculated for natural organic matter by applying principal component analysis (PCA) to a reference data set of 47 independent titration curves from fulvic and humic acids measured at I = 0.1 M. The complete data set was reconstructed statistically from pH 3.5 to 9.8 with only six parameters, compared to seven or eight generally adjusted with common semi-empirical speciation models for organic matter, and explains correlations that occur with the higher number of parameters. Existing proton-binding models are not necessarily overparametrized, but instead titration data lack the sensitivity needed to quantify the full set of binding properties of humic materials. Model-independent conditional pK values can be obtained directly from the derivative of titration data, and this approach is the most conservative. The apparent proton-binding constants of the 23 fulvic acids (FA) and 24 humic acids (HA) derived from a high-quality polynomial parametrization of the data set are pK(H,COOH)(FA) = 4.18 +/- 0.21, pK(H,Ph-OH)(FA) = 9.29 +/- 0.33, pK(H,COOH)(HA) = 4.49 +/- 0.18, and pK(H,Ph-OH)(HA) = 9.29 +/- 0.38. Their values at other ionic strengths are more reliably calculated with the empirical Davies equation than any existing model fit. PMID

  11. Preparation of polyaniline nanostructures doped with different dicarboxylic acids through template-free method

    NASA Astrophysics Data System (ADS)

    Sun, Chuanyu; Wang, Yu

    2014-09-01

    In this article nanoscaled polyanilines (PANI) were prepared based on template-free method in the presence of dicarboxylic acid dopants (e.g. D-tartaric acid, succinic acid, maleic acid and fumaric acid). The trans-cis isomerization of butenedioic acid played an important role in the formation of nanostructures from the plane-like to nanofibers, and the PANI doped with maleic acid (MA) had larger diameter, higher crystallinity and conductivity than PANI doped with fumaric acid (FA).

  12. Method for liquid chromatographic extraction of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  13. New method for administration of hydrochloric acid in metabolic alkalosis.

    PubMed

    Knutsen, O H

    1983-04-30

    In a new method for peripheral intravenous infusion of hydrochloric acid the HCl is buffered in an aminoacid solution and infused with a fat emulsion. The aminoacids and the fat emulsions are stable in the presence of HCl, and the transfusion set is resistant to the chemical actin of 0.15 mol/l HCl. Two case-reports show that HCl can be administered safely through a peripheral vein. PMID:6132269

  14. Method and apparatus for staining immobilized nucleic acids

    DOEpatents

    Ramsey, J. Michael; Foote, Robert S.; Jacobson, Stephen C.

    2000-01-01

    A method for staining immobilized nucleic acids includes the steps of affixing DNA probes to a solid substrate, moving target DNA material into proximity with the DNA probes, whereby the target DNA hybridized with specific ones of the DNA probes, and moving a fluorescent dye into proximity with the hybridized target DNA, whereby the fluorescent dye binds to the hybridized DNA to enable subsequent detection of fluorescence.

  15. Properties of nanocellulose isolated from corncob residue using sulfuric acid, formic acid, oxidative and mechanical methods.

    PubMed

    Liu, Chao; Li, Bin; Du, Haishun; Lv, Dong; Zhang, Yuedong; Yu, Guang; Mu, Xindong; Peng, Hui

    2016-10-20

    In this work, nanocellulose was extracted from bleached corncob residue (CCR), an underutilized lignocellulose waste from furfural industry, using four different methods (i.e. sulfuric acid hydrolysis, formic acid (FA) hydrolysis, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and pulp refining, respectively). The self-assembled structure, morphology, dimension, crystallinity, chemical structure and thermal stability of prepared nanocellulose were investigated. FA hydrolysis produced longer cellulose nanocrystals (CNCs) than the one obtained by sulfuric acid hydrolysis, and resulted in high crystallinity and thermal stability due to its preferential degradation of amorphous cellulose and lignin. The cellulose nanofibrils (CNFs) with fine and individualized structure could be isolated by TEMPO-mediated oxidation. In comparison with other nanocellulose products, the intensive pulp refining led to the CNFs with the longest length and the thickest diameter. This comparative study can help to provide an insight into the utilization of CCR as a potential source for nanocellulose production. PMID:27474618

  16. Titration and hysteresis in epigenetic chromatin silencing

    NASA Astrophysics Data System (ADS)

    Dayarian, Adel; Sengupta, Anirvan M.

    2013-06-01

    Epigenetic mechanisms of silencing via heritable chromatin modifications play a major role in gene regulation and cell fate specification. We consider a model of epigenetic chromatin silencing in budding yeast and study the bifurcation diagram and characterize the bistable and the monostable regimes. The main focus of this paper is to examine how the perturbations altering the activity of histone modifying enzymes affect the epigenetic states. We analyze the implications of having the total number of silencing proteins, given by the sum of proteins bound to the nucleosomes and the ones available in the ambient, to be constant. This constraint couples different regions of chromatin through the shared reservoir of ambient silencing proteins. We show that the response of the system to perturbations depends dramatically on the titration effect caused by the above constraint. In particular, for a certain range of overall abundance of silencing proteins, the hysteresis loop changes qualitatively with certain jump replaced by continuous merger of different states. In addition, we find a nonmonotonic dependence of gene expression on the rate of histone deacetylation activity of Sir2. We discuss how these qualitative predictions of our model could be compared with experimental studies of the yeast system under anti-silencing drugs.

  17. EPA (ENVIRONMENTAL PROTECTION AGENCY) METHOD STUDY 30, METHOD 625 - BASE/NEUTRALS, ACIDS AND PESTICIDES

    EPA Science Inventory

    The work which is described in this report was performed for the purpose of validating, through an interlaboratory study, Method 625 for the analysis of the base/neutral, acid, and pesticide priority pollutants. This method is based on the extraction and concentration of the vari...

  18. Comparison of ozone determinations by ultraviolet photometry and gas-phase titration

    NASA Technical Reports Server (NTRS)

    Demore, W. B.; Patapoff, M.

    1976-01-01

    A comparison of ozone determinations based on ultraviolet absorption photometry and gas-phase titration (GPT) shows good agreement between the two methods. Together with other results, these findings indicate that three candidate reference methods for ozone, UV photometry, IR photometry, and GPT are in substantial agreement. However, the GPT method is not recommended for routine use by air pollution agencies for calibration of ozone monitors because of susceptibility to experimental error.

  19. Catalytic thermometric titrations in non-aqueous solvents by coulometrically generated titrant.

    PubMed

    Vajgand, V J; Gaál, F F; Brusin, S S

    1970-05-01

    Catalytic thermometric titrations have been developed for tertiary amines and salts of organic acids in acetic and propionic anhydride with titrant coulometrically generated at a mercury and/or platinum anode, hydroquinone being added to the solution titrated if the platinum anode is used. The results obtained are compared with those obtained by coulometric titration with the end-point detected either photometrically or potentiometrically. On a élaboré des titrages thermométriques catalytiques pour les amines tertiaires et les sels d'acides organiques en anhydrides aétique et propionique avec l'agent de titrage engendré coulométriquement sur une anode de mercure et/ou platine, de l'hydroquinone étant ajoutée à la solution titrée si l'on emploie l'anode de platine. Les résultats obtenus sont comparés avec ceux obtenus par titrage coulométrique avec le point de fin de réaction détecté soit photométriquement soit potentioétriquement. PMID:18960753

  20. Rapid Clozapine Titration in Patients with Treatment Refractory Schizophrenia.

    PubMed

    Poyraz, Cana Aksoy; Özdemir, Armağan; Sağlam, Nazife Gamze Usta; Turan, Şenol; Poyraz, Burç Çağrı; Tomruk, Nesrin; Duran, Alaattin

    2016-06-01

    The aim of this study is to evaluate the safety and effectiveness of rapid clozapine titration in patients with schizophrenia in hospital settings. We conducted a retrospective two-center cohort study to compare the safety and effectiveness of clozapine with different titration rates in treatment-refractory patients with schizophrenia. In the first center, clozapine was started at 25-50 mg followed by 50-100 mg as needed every 6 h on day 1, followed by increases of 50-100 mg/day. In the second center, titration was slower; clozapine initiated with 12.5-50 mg on day 1 followed by increases of 25-50 mg/day. The number of days between starting of clozapine until discharge was shorter in the rapid titration group (22.4 ± 8.72 vs 27.0 ± 10.5, p = 0.1). Number of days of total hospital stay were significantly shorter in the rapid titration group (29.6 ± 10.6 vs 41.2 ± 14.8, p = 0.002). Hypotension was more common in the rapid titration group and one patient had suspected myocarditis. Rapid clozapine titration appeared safe and effective. The length of stay following initiation of clozapine was shorter in the rapid-titration group, although this was not statistically significant. However starting clozapine earlier together with rapid titration has significantly shortened the length of hospital stay in patients with treatment refractory schizophrenia. PMID:26433727

  1. Hydroxyapatite-phosphonoformic acid hybrid compounds prepared by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Turki, Thouraya; Othmani, Masseoud; Bantignies, Jean-Louis; Bouzouita, Khaled

    2014-01-01

    Hydroxyapatites were prepared in the presence of different amounts of phosphonoformic acid (PFA) via the hydrothermal method. The obtained powders were characterized through chemical analysis, XRD, IR, 31P MAS-NMR, TEM, and TG-TDA. The XRD showed that the PFA did not affect the apatite composition. Indeed, only a reduction of the crystallite size was noted. After grafting of PFA, the IR spectroscopy revealed the appearance of new bands belonging to HPO42- and carboxylate groups of the apatite and organic moiety, respectively. Moreover, the 31P MAS-NMR spectra exhibited a peak with a low intensity assigned to the terminal phosphonate group of the organic moiety in addition to that of the apatite. Based on these results, a reaction mechanism involving the surface hydroxyl groups (tbnd Casbnd OH) of the apatite and the carboxyl group of the acid was proposed.

  2. The Mobile Insulin Titration Intervention (MITI) for Insulin Glargine Titration in an Urban, Low-Income Population: Randomized Controlled Trial Protocol

    PubMed Central

    Levy, Natalie; Nilo, Annielyn; Singer, Karyn; Bernik, Lidia S; Etiebet, Mary-Ann; Fang, Yixin; Cho, James; Natarajan, Sundar

    2015-01-01

    Background Patients on insulin glargine typically visit a clinician to obtain advice on how to adjust their insulin dose. These multiple clinic visits can be costly and time-consuming, particularly for low-income patients. It may be feasible to achieve insulin titration through text messages and phone calls with patients instead of face-to-face clinic visits. Objective The objectives of this study are to (1) evaluate if the Mobile Insulin Titration Intervention (MITI) is clinically effective by helping patients reach their optimal dose of insulin glargine, (2) determine if the intervention is feasible within the setting and population, (3) assess patient satisfaction with the intervention, and (4) measure the costs associated with this intervention. Methods This is a pilot study evaluating an approach to insulin titration using text messages and phone calls among patients with insulin-dependent type 2 diabetes in the outpatient medical clinic of Bellevue Hospital Center, a safety-net hospital in New York City. Patients will be randomized in a 1:1 ratio to either the MITI arm (texting/phone call intervention) or the usual-care arm (in-person clinic visits). Using a Web-based platform, weekday text messages will be sent to patients in the MITI arm, asking them to text back their fasting blood glucose values. In addition to daily reviews for alarm values, a clinician will rereview the texted values weekly, consult our physician-approved titration algorithm, and call the patients with advice on how to adjust their insulin dose. The primary outcome will be whether or not a patient reaches his/her optimal dose of insulin glargine within 12 weeks. Results Recruitment for this study occurred between June 2013 and December 2014. We are continuing to collect intervention and follow-up data from our patients who are currently enrolled. The results of our data analysis are expected to be available in 2015. Conclusions This study explores the use of widely-available text

  3. Microscale chemistry-based design of eco-friendly, reagent-saving and efficient pharmaceutical analysis: a miniaturized Volhard's titration for the assay of sodium chloride.

    PubMed

    Rojanarata, Theerasak; Sumran, Krissadecha; Nateetaweewat, Paksupang; Winotapun, Weerapath; Sukpisit, Sirarat; Opanasopit, Praneet; Ngawhirunpat, Tanasait

    2011-09-15

    This work demonstrates the extended application of microscale chemistry which has been used in the educational discipline to the real analytical purposes. Using Volhard's titration for the determination of sodium chloride as a paradigm, the reaction was downscaled to less than 2 mL conducted in commercially available microcentrifuge tubes and using micropipettes for the measurement and transfer of reagents. The equivalence point was determined spectrophotometrically on the microplates which quickened the multi-sample measurements. After the validation and evaluation with bulk and dosage forms, the downsized method showed good accuracy comparable to the British Pharmacopeial macroscale method and gave satisfactory precision (intra-day, inter-day, inter-analyst and inter-equipment) with the relative standard deviation of less than 0.5%. Interestingly, the amount of nitric acid, silver nitrate, ferric alum and ammonium thiocyanate consumed in the miniaturized titration was reduced by the factors of 25, 50, 50 and 215 times, respectively. The use of environmentally dangerous dibutyl phthalate was absolutely eliminated in the proposed method. Furthermore, the release of solid waste silver chloride was drastically reduced by about 25 folds. Therefore, microscale chemistry is an attractive, facile and powerful green strategy for the development of eco-friendly, safe, and cost-effective analytical methods suitable for a sustainable environment. PMID:21807190

  4. Solvatochromic Dyes as pH-Independent Indicators for Ionophore Nanosphere-Based Complexometric Titrations.

    PubMed

    Zhai, Jingying; Xie, Xiaojiang; Bakker, Eric

    2015-12-15

    For half a century, complexometric titrations of metal ions have been performed with water-soluble chelators and indicators that typically require careful pH control. Very recently, ion-selective nanosphere emulsions were introduced that exhibit ion-exchange properties and are doped with lipophilic ionophores originally developed for chemical ion sensors. They may serve as novel, highly selective and pH independent complexometric reagents. While ion optode emulsions have been demonstrated as useful indicators for such titrations, they exhibit a pH cross-response that unfortunately complicates the identification of the end point. Here, we present pH-independent optode nanospheres as indicators for complexometric titrations, with calcium as an initial example. The nanospheres incorporate an ionic solvatochromic dye (SD), ion exchanger and ionophore. The solvatochromic dye will be only expelled from the core of the nanosphere into the aqueous solution at the end point at which point it results in an optical signal change. The titration curves are demonstrated to be pH-independent and with sharper end points than with previously reported chromoionophore-based optical nanospheres as indicator. The calcium concentration in mineral water was successfully determined using this method. PMID:26595520

  5. Potentiometric Titrations for Measuring the Capacitance of Colloidal Photodoped ZnO Nanocrystals.

    PubMed

    Brozek, Carl K; Hartstein, Kimberly H; Gamelin, Daniel R

    2016-08-24

    Colloidal semiconductor nanocrystals offer a unique opportunity to bridge molecular and bulk semiconductor redox phenomena. Here, potentiometric titration is demonstrated as a method for quantifying the Fermi levels and charging potentials of free-standing colloidal n-type ZnO nanocrystals possessing between 0 and 20 conduction-band electrons per nanocrystal, corresponding to carrier densities between 0 and 1.2 × 10(20) cm(-3). Potentiometric titration of colloidal semiconductor nanocrystals has not been described previously, and little precedent exists for analogous potentiometric titration of any soluble reductants involving so many electrons. Linear changes in Fermi level vs charge-carrier density are observed for each ensemble of nanocrystals, with slopes that depend on the nanocrystal size. Analysis indicates that the ensemble nanocrystal capacitance is governed by classical surface electrical double layers, showing no evidence of quantum contributions. Systematic shifts in the Fermi level are also observed with specific changes in the identity of the charge-compensating countercation. As a simple and contactless alternative to more common thin-film-based voltammetric techniques, potentiometric titration offers a powerful new approach for quantifying the redox properties of colloidal semiconductor nanocrystals. PMID:27444048

  6. Volumetric determination of uranium titanous sulfate as reductant before oxidimetric titration

    USGS Publications Warehouse

    Wahlberg, J.S.; Skinner, D.L.; Rader, L.F., Jr.

    1957-01-01

    Need for a more rapid volumetric method for the routine determination of uranium in uranium-rich materials has led to the development of a method that uses titanous sulfate as a reductant before oxidimetric titration. Separation of the hydrogen sulfide group is not necessary. Interfering elements precipitated by cupferron are removed by automatic filtrations made simultaneously rather than by the longer chloroform extraction method. Uranium is reduced from VI to IV by addition of an excess of titanous sulfate solution, cupric ion serving as an indicator by forming red metallic copper when reduction is complete. The copper is reoxidized by addition of mercuric perchlorate. The reduced uranium is then determined by addition of excess ferric sulfate and titration with ceric sulfate. The method has proved to be rapid, accurate, and economical.

  7. A method to find palindromes in nucleic acid sequences.

    PubMed

    Anjana, Ramnath; Shankar, Mani; Vaishnavi, Marthandan Kirti; Sekar, Kanagaraj

    2013-01-01

    Various types of sequences in the human genome are known to play important roles in different aspects of genomic functioning. Among these sequences, palindromic nucleic acid sequences are one such type that have been studied in detail and found to influence a wide variety of genomic characteristics. For a nucleotide sequence to be considered as a palindrome, its complementary strand must read the same in the opposite direction. For example, both the strands i.e the strand going from 5' to 3' and its complementary strand from 3' to 5' must be complementary. A typical nucleotide palindromic sequence would be TATA (5' to 3') and its complimentary sequence from 3' to 5' would be ATAT. Thus, a new method has been developed using dynamic programming to fetch the palindromic nucleic acid sequences. The new method uses less memory and thereby it increases the overall speed and efficiency. The proposed method has been tested using the bacterial (3891 KB bases) and human chromosomal sequences (Chr-18: 74366 kb and Chr-Y: 25554 kb) and the computation time for finding the palindromic sequences is in milli seconds. PMID:23515654

  8. Molecular Dynamics Simulation of the Titration of Polyoxocations in Aqueous Solution

    SciTech Connect

    Rustad, James R.

    2005-09-01

    The aqueous complex ion Al30O8(OH)56(H2O)26 18+(Al30) has a variety of bridging and terminal amphoteric surface functional groups which deprotonate over a pH range of 4–7. Their relative degree of protonation is calculated here from a series of molecular dynamics simulations in what appear to be the first molecular dynamics simulations of an acidometric titration. In these simulations, a model M30O8(OH)56(H2O)26 18+ ion is embedded in aqueous solution and titrated with hydroxide ions in the presence of a charge-compensating background of perchlorate ions. Comparison with titration of a model M13O4(OH)24(H2O)12 7+ reveals that the M30 ion is more acidic than the M13 ion due to the presence of acidic nH2O functional groups. The higher acidities of the functional groups on the M30 ion appear to result from enhanced hydration. Metal–oxygen bond lengths are calculated for the ion in solution, an isolated ion in the gas phase, and in its crystalline hydrate sulfate salt. Gas-phase and crystalline bond lengths do not correlate well with those calculated in solution. The acidities do not relate in any simple way to the number of metals coordinating the surface functional group or the M-O bond length. Moreover, the calculated acidity in solution does not correlate with proton affinities calculated for the isolated ion in the absence of solvent. It is concluded that the search for simple indicators of structure–reactivity relationships at the level of individual reactive sites faces major limitations, unless specific information on the hydration states of the functional groups is available.

  9. Method of encapsulating polyaminopolycarboxylic acid chelating agents in liposomes

    DOEpatents

    Rahman, Yueh Erh

    1977-11-10

    A method is provided for transferring a polyaminopolycarboxylic acid chelating agent across a cellular membrane by encapsulating the charged chelating agent within liposomes, which liposomes will be taken up by the cells, thereby transferring the chelating agent across the cellular membrane. The chelating agent is encapsulated within liposomes by drying a lipid mixture to form a thin film and wetting the lipid film with a solution containing the chelating agent. Mixing then results in the formation of a suspension of liposomes encapsulating the chelating agent, which liposomes can then be separated.

  10. A Titration Technique for Demonstrating a Magma Replenishment Model.

    ERIC Educational Resources Information Center

    Hodder, A. P. W.

    1983-01-01

    Conductiometric titrations can be used to simulate subduction-setting volcanism. Suggestions are made as to the use of this technique in teaching volcanic mechanisms and geochemical indications of tectonic settings. (JN)

  11. Microscope Titration and Extraction of DNA from Liver.

    ERIC Educational Resources Information Center

    Mayo, Lois T.; And Others

    1993-01-01

    Describes a simple and inexpensive, one-period activity to extract DNA to make the study of DNA less abstract. A microscope titration is used to determine when cells are ready for DNA extraction. (PR)

  12. Method for continuous production of aromatic carboxylic acid

    SciTech Connect

    Abrams, K.J.

    1988-12-20

    This patent describes a method for the continuous production of an aromatic carboxylic acid product in a pressurized oxidation reactor by liquid-phase, exothermic oxidation of an aromatic alkyl feed with an oxygen-containing gas, in the presence of an aromatic alkyl feed with an oxygen-containing gas, in the presence of an oxidation catalyst and in an aqueous monocarboxylic C/sub 2/ to C/sub 6/ aliphatic acid solvent medium, wherein the heat generated during the course of the oxidation is removed from the reactor by vaporization of a portion of the reaction medium and water, wherein the resulting vapors are condensed in part in a reflux loop externally of the oxidation reactor to produce a condensate and a gaseous phase, and wherein at least a portion of the condensate is returned to the oxidation reactor, the improvement comprising a method for controlling within desired limits the concentration of water in the oxidation reactor, which comprises: partitioning the vapors into a parallel condensate having a relatively lesser water-to-solvent weight ratio and a vapor phase having a relatively greater water-to-solvent weight ratio; returning the partial condensate directly to the oxidation reactor as a direct reflux stream; withdrawing the vapor phase from the reflux loop as a vapor stream; subjecting the withdrawn vapor stream to heat exchange while decreasing the vapor stream pressure to less than the oxidation reactor pressure to thereby produce an aqueous aliphatic acid stream having a water-to-solvent weight ratio greater than that of the direct reflux stream.

  13. Method for production of petroselinic acid and OMEGA12 hexadecanoic acid in transgenic plants

    DOEpatents

    Ohlrogge, J.B.; Cahoon, E.B.; Shanklin, J.; Somerville, C.R.

    1995-07-04

    The present invention relates to a process for producing lipids containing the fatty acid, petroselinic acid, in plants. The production of petroselinic acid is accomplished by genetically transforming plants which do not normally accumulate petroselinic acid with a gene for a {omega}12 desaturase from another species which does normally accumulate petroselinic acid. 19 figs.

  14. Method for production of petroselinic acid and OMEGA12 hexadecanoic acid in transgenic plants

    DOEpatents

    Ohlrogge, John B.; Cahoon, Edgar B.; Shanklin, John; Somerville, Christopher R.

    1995-01-01

    The present invention relates to a process for producing lipids containing the fatty acid petroselinic acid in plants. The production of petroselinic acid is accomplished by genetically transforming plants which do not normally accumulate petroselinic acid with a gene for a .omega.12 desaturase from another species which does normally accumulate petroselinic acid.

  15. Simple method of isolating humic acids from organic soils

    NASA Astrophysics Data System (ADS)

    Ahmed, O. H.; Susilawati, K.; Nik Muhamad, A. B.; Khanif, M. Y.

    2009-04-01

    Humic substances particularly humic acids (HA) play a major role in soil conditioning e.g. erosion control, soil cation exchange capacity, complexation of heavy metal ions and pesticides, carbon and nitrogen cycles, plant growth and reduction of ammonia volatilization from urea. Humified substances such as coal, composts, and peat soils have substantial amounts of HA but the isolation of these acids is expensive, laborious, and time consuming. Factors that affect the quality and yield of HA isolated from these materials include extraction, fractionation, and purification periods. This work developed a simple, rapid, and cost effective method of isolating HA from peat soils. There was a quadratic relationship between extraction period and HA yield. Optimum extraction period was estimated at 4 h instead of the usual range of 12 to 48 h. There was no relationship between fractionation period and HA yield. As such 2 h instead of the usual range of 12 to 24 h fractionation period could be considered optimum. Low ash content (5%), remarkable reduction in K, coupled with the fact that organic C, E4/E6, carboxylic COOH, phenolic OH, and total acidity values of the HA were consistent with those reported by other authors suggest that the HA dealt with were free from mineral matter. This was possible because the distilled water used to purify the HA served as Bronsted-Lowry acid during the purification process of the HA. Optimum purification period using distilled waster was 1 h instead of the usual range of 1 and 7 days (uses HF and HCl and dialysis). Humic acids could be isolated from tropical peat soils within 7 h (i.e. 4 h extraction, 2 h fractionation, and 1 h purification) instead of the existing period of 2 and 7 days. This could facilitate the idea of producing organic fertilizers such as ammonium-humate and potassium-humate from humified substances since techniques devised in this study did not alter the true nature of the HA. Besides, the technique is rapid, simple

  16. Cholinium-amino acid based ionic liquids: a new method of synthesis and physico-chemical characterization.

    PubMed

    De Santis, Serena; Masci, Giancarlo; Casciotta, Francesco; Caminiti, Ruggero; Scarpellini, Eleonora; Campetella, Marco; Gontrani, Lorenzo

    2015-08-28

    In the present work we report the synthesis and physico-chemical characterization in terms of the viscosity and density of a wide series of cholinium-amino acid based room temperature ionic liquids ([Ch][AA] RTILs). 18 different amino acids were used to obtain 14 room temperature ILs. Among the most common AAs, only valine did not form an RTIL but it is a liquid above 80 °C. With respect to the methods reported in the literature we propose a synthesis based on potentiometric titration which has several advantages such as shorter preparation time, stoichiometry within ±1%, very high yields (close to 100%), high reproducibility, and no use of organic solvents, thus being more environmentally friendly. We tried to prepare dianionic ILs with some AAs with two potentially ionisable groups but in all cases the salts were solids at room temperature. All the ILs were characterized by (1)H NMR to confirm the stoichiometry. Physico-chemical properties such as density, viscosity, refractive index and conductivity were measured as a function of temperature and correlated with empirical equations. The values were compared with the data already reported in the literature for some [Ch][AA] ILs. The thermal expansion coefficient αp and the molar volume Vm were also calculated from the experimental density values. Due to the high number of AAs explored and their structural heterogeneity we have been able to find some interesting correlations between the data obtained and the structural features of the AAs in terms of the alkyl chain length, hydrogen bonding ability, stacking and cyclization. Some parameters were also found to be in good agreement with those reported for other ILs. We think that these data can give an important contribution to the understanding of the structure-property relationship of ILs because they focused on the structural effect of the anions, while most data in the literature are focussed on the cations. PMID:26206450

  17. Potentiometric determination of free acidity in presence of hydrolysable ions and a sequential determination of hydrazine.

    PubMed

    Ganesh, S; Khan, Fahmida; Ahmed, M K; Pandey, S K

    2011-08-15

    A simple potentiometric method for the determination of free acidity in presence of hydrolysable ions and sequential determination of hydrazine is developed and described. Both free acid and hydrazine are estimated from the same aliquot. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 1.2% relative standard deviation. Hydrazine content has also been determined in the same aliquot with a recovery of nitric acid is 99% with 2% relative standard deviation. The major advantage of the method is that generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal. PMID:21726724

  18. Method of Identifying a Base in a Nucleic Acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    1999-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  19. Rational Catalyst Design of Titanium-Silica Materials Aided by Site-Specific Titration Tools

    NASA Astrophysics Data System (ADS)

    Eaton, Todd Robert

    Silica-supported titanium materials are widely used for thermocatalytic applications such as hydroxylation of alkanes and aromatics, oxidation of alcohols and ethers, ammoximation of carbonyls, and sulfoxidations, while Ti-based materials are widely studied for photocatalytic applications such as photo-oxidation of organic substrates and photo-reduction of CO 2. However, the underlying phenomena of how to synthesize, identify, and control the active structures in these materials is not well understood because of the narrow scope of previous work. Studies of titanium-based catalysts typically focus on materials where the metal is present as either highly-dispersed Ti cations or in bulk crystalline TiO2 form, neglecting the numerous and potentially useful intermediate structures. Furthermore, these works typically focus on a single synthesis technique and rely upon bulk characterization techniques to understand the materials. Here rigorous titanium-silica synthesis-structure-function relationships are established by examining several different synthetic method and utilizing characterization techniques that enable an atomic-level understanding of the materials. The materials studied span the range from isolated Ti cations to clustered TiOx domains, polymeric TiO x domains, anatase-like 2D TiO2 domains, and 3D crystalline TiO2. Tools to quantify accessible TiO x and tetrahedral Ti sites are developed, utilizing the selective titration of titanium with phenylphosphonic acid (PPA). Catalytic properties are probed with the photocatalytic oxidation of benzyl alcohol and the thermocatalytic epoxidation of cis-cyclooctene with H2O2 . PPA titration data indicate that the rate of benzyl alcohol photo-oxidation is independent of titanium coordination, while the rate of alkene epoxidation with H2O2 is proportional to the number of tetrahedral titanium sites on the catalyst. PPA titration data also enables the estimation of TiO2 particle size and reveals an important distinction

  20. Diagnostic Methods for Bile Acid Malabsorption in Clinical Practice

    PubMed Central

    Vijayvargiya, Priya; Camilleri, Michael; Shin, Andrea; Saenger, Amy

    2013-01-01

    Altered bile acid (BA) concentrations in the colon may cause diarrhea or constipation. BA malabsorption (BAM) accounts for >25% of patients with irritable bowel syndrome (IBS) with diarrhea and chronic diarrhea in Western countries. As BAM is increasingly recognized, proper diagnostic methods are desired in clinical practice to help direct the most effective treatment course for the chronic bowel dysfunction. This review appraises the methodology, advantages and disadvantages of 4 tools that directly measure BAM: 14C-glycocholate breath and stool test, 75Selenium HomotauroCholic Acid Test (SeHCAT), 7 α-hydroxy-4-cholesten-3-one (C4) and fecal BAs. 14C-glycocholate is a laborious test no longer widely utilized. 75SeHCAT is validated, but not available in the United States. Serum C4 is a simple, accurate method that is applicable to a majority of patients, but requires further clinical validation. Fecal measurements to quantify total and individual fecal BAs are technically cumbersome and not widely available. Regrettably, none of these tests are routinely available in the U.S., and a therapeutic trial with a BA binder is used as a surrogate for diagnosis of BAM. Recent data suggest there is an advantage to studying fecal excretion of the individual BAs and their role in BAM; this may constitute a significant advantage of the fecal BA method over the other tests. Fecal BA test could become a routine addition to fecal fat measurement in patients with unexplained diarrhea. In summary, availability determines the choice of test among C4, SeHCAT and fecal BA; more widespread availability of such tests would enhance clinical management of these patients. PMID:23644387

  1. Physical methods of nucleic acid transfer: general concepts and applications

    PubMed Central

    Villemejane, Julien; Mir, Lluis M

    2009-01-01

    Physical methods of gene (and/or drug) transfer need to combine two effects to deliver the therapeutic material into cells. The physical methods must induce reversible alterations in the plasma membrane to allow the direct passage of the molecules of interest into the cell cytosol. They must also bring the nucleic acids in contact with the permeabilized plasma membrane or facilitate access to the inside of the cell. These two effects can be achieved in one or more steps, depending upon the methods employed. In this review, we describe and compare several physical methods: biolistics, jet injection, hydrodynamic injection, ultrasound, magnetic field and electric pulse mediated gene transfer. We describe the physical mechanisms underlying these approaches and discuss the advantages and limitations of each approach as well as its potential application in research or in preclinical and clinical trials. We also provide conclusions, comparisons, and projections for future developments. While some of these methods are already in use in man, some are still under development or are used only within clinical trials for gene transfer. The possibilities offered by these methods are, however, not restricted to the transfer of genes and the complementary uses of these technologies are also discussed. As these methods of gene transfer may bypass some of the side effects linked to viral or biochemical approaches, they may find their place in specific clinical applications in the future. This article is part of a themed section on Vector Design and Drug Delivery. For a list of all articles in this section see the end of this paper, or visit: http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009 PMID:19154421

  2. Rapid and simple method for purification of nucleic acids.

    PubMed Central

    Boom, R; Sol, C J; Salimans, M M; Jansen, C L; Wertheim-van Dillen, P M; van der Noordaa, J

    1990-01-01

    We have developed a simple, rapid, and reliable protocol for the small-scale purification of DNA and RNA from, e.g., human serum and urine. The method is based on the lysing and nuclease-inactivating properties of the chaotropic agent guanidinium thiocyanate together with the nucleic acid-binding properties of silica particles or diatoms in the presence of this agent. By using size-fractionated silica particles, nucleic acids (covalently closed circular, relaxed circular, and linear double-stranded DNA; single-stranded DNA; and rRNA) could be purified from 12 different specimens in less than 1 h and were recovered in the initial reaction vessel. Purified DNA (although significantly sheared) was a good substrate for restriction endonucleases and DNA ligase and was recovered with high yields (usually over 50%) from the picogram to the microgram level. Copurified rRNA was recovered almost undegraded. Substituting size-fractionated silica particles for diatoms (the fossilized cell walls of unicellular algae) allowed for the purification of microgram amounts of genomic DNA, plasmid DNA, and rRNA from cell-rich sources, as exemplified for pathogenic gram-negative bacteria. In this paper, we show representative experiments illustrating some characteristics of the procedure which may have wide application in clinical microbiology. Images PMID:1691208

  3. Use of chicken cell line LSCC-H32 for titration of animal viruses and exogenous chicken interferon.

    PubMed

    Roth, S; Kaaden, O R

    1985-03-01

    The chicken embryo cell line LSCC-H32 was tested for the propagation and titration of several animal viruses of the families Toga-, Reo-, Rhabdo-, Herpeto-, Orthomyxo-, Paramyxo-, and Poxviridae and compared with secondary chicken embryo cells. The LSCC-H32 cells were demonstrated to be as susceptible for most of the tested viruses as were secondary chicken embryo cells. Both produced comparably sized virus plaques. The titers of Sindbis and Semliki Forest viruses in LSCC-H32 cells were 5- to 40-fold higher than in secondary chicken embryo cells or BHK-21 cells, respectively. Furthermore, exogenous chicken standard interferon was titrated in the LSCC-H32 cells, and a 50% plaque titer reduction of the challenging vesicular stomatitis virus was achieved by 0.12 IU of a standard chicken interferon preparation. Endogenous chicken interferon could not be induced by treatment of the cells with polyinosinic acid-polycytidylic acid. Due to its high plating efficiency and metabolic activities, the LSCC-H32 cell line provides a useful cell system for the titration and large-scale production of the tested animal viruses and for the titration of exogenous chicken interferon. PMID:2581511

  4. An acidic method of zein extraction from DDGS.

    PubMed

    Xu, Weijie; Reddy, Narendra; Yang, Yiqi

    2007-07-25

    Zein with a higher intrinsic viscosity and phosphorus content, similar protein content, lower yellowness, and at potentially much lower cost than commercially available zein was obtained from distillers dried grains with solubles (DDGS). A novel extraction method using acidic conditions in the presence of a reducing agent has been used to obtain about 10% aqueous ethanol soluble zein from DDGS. The optimum pH, time, temperature, and amount of reducing agent that can produce zein with high quality and yield have been developed. In addition to the zein, about 17% oil based on the dry weight of DDGS has also been obtained during zein extraction. The zein obtained from this research is expected to be suitable for use as fibers, films, and binders and in paints. PMID:17590006

  5. Kinetic titration with differential thermometric determination of the end-point.

    PubMed

    Sajó, I

    1968-06-01

    A method has been described for the determination of concentrations below 10(-4)M by applying catalytic reactions and using thermometric end-point determination. A reference solution, identical with the sample solution except for catalyst, is titrated with catalyst solution until the rates of reaction become the same, as shown by a null deflection on a galvanometer connected via bridge circuits to two opposed thermistors placed in the solutions. PMID:18960338

  6. Rapid semi-micro potentiometric titration of Ir(IV) with hydrazine sulphate

    SciTech Connect

    Lichtig, J.; ALves, J.C.

    1994-07-01

    A rapid potentiometric titration of Ir(IV) with hydrazine sulphate is described. 1.0 mg, 0.25 mg and 0.10 mg are determined with precision of 0.5%, 0.8% and 3.0%, respectively. Most of the common ions do not interfere as well as Rh(III). Some determinations of Ir(IV) in ores made with good precision and compared with a spectrophotometric method.

  7. Method for producing labeled single-stranded nucleic acid probes

    DOEpatents

    Dunn, John J.; Quesada, Mark A.; Randesi, Matthew

    1999-10-19

    Disclosed is a method for the introduction of unidirectional deletions in a cloned DNA segment. More specifically, the method comprises providing a recombinant DNA construct comprising a DNA segment of interest inserted in a cloning vector, the cloning vector having an f1 endonuclease recognition sequence adjacent to the insertion site of the DNA segment of interest. The recombinant DNA construct is then contacted with the protein pII encoded by gene II of phage f1 thereby generating a single-stranded nick. The nicked DNA is then contacted with E. coli Exonuclease III thereby expanding the single-stranded nick into a single-stranded gap. The single-stranded gapped DNA is then contacted with a single-strand-specific endonuclease thereby producing a linearized DNA molecule containing a double-stranded deletion corresponding in size to the single-stranded gap. The DNA treated in this manner is then incubated with DNA ligase under conditions appropriate for ligation. Also disclosed is a method for producing single-stranded DNA probes. In this embodiment, single-stranded gapped DNA, produced as described above, is contacted with a DNA polymerase in the presence of labeled nucleotides to fill in the gap. This DNA is then linearized by digestion with a restriction enzyme which cuts outside the DNA segment of interest. The product of this digestion is then denatured to produce a labeled single-stranded nucleic acid probe.

  8. Compositions and method for controlling precipitation when acidizing sour wells

    SciTech Connect

    Dill, W.R.; Walker, M.L.

    1989-12-19

    This patent describes an acidizing composition for treating a sour well. It comprises: a base acid solution having an initial ph below 1.9; an iron sequestering agent to combine with iron present in the solution comprising at least one compound selected from the group consisting of aminopolycarboxylic acids, hydroxycarboxylic acids, cyclic polyethers and derivatives of the acids and ethers present in an amount of from about 0.25 to about 5 percent by weight of the acid solution; and a sulfide modifier to combine with sulfides present in the solution comprising at least one member selected from the group consisting of an aldehyde, acetal, hemiacetal and any other compound capable of forming an aldehyde in solution, present in an amount of from about 1 to about 4 percent by weight of the acid solution, whereby precipitation of ferric hydroxide, ferrous sulfide and elemental sulfur is inhibited as acid spending occurs.

  9. In situ synthesis carbonated hydroxyapatite layers on enamel slices with acidic amino acids by a novel two-step method.

    PubMed

    Wu, Xiaoguang; Zhao, Xu; Li, Yi; Yang, Tao; Yan, Xiujuan; Wang, Ke

    2015-09-01

    In situ fabrication of carbonated hydroxyapatite (CHA) remineralization layer on an enamel slice was completed in a novel, biomimetic two-step method. First, a CaCO3 layer was synthesized on the surface of demineralized enamel using an acidic amino acid (aspartic acid or glutamate acid) as a soft template. Second, at the same concentration of the acidic amino acid, rod-like carbonated hydroxyapatite was produced with the CaCO3 layer as a sacrificial template and a reactant. The morphology, crystallinity and other physicochemical properties of the crystals were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX), respectively. Acidic amino acid could promote the uniform deposition of hydroxyapatite with rod-like crystals via absorption of phosphate and carbonate ions from the reaction solution. Moreover, compared with hydroxyapatite crystals coated on the enamel when synthesized by a one-step method, the CaCO3 coating that was synthesized in the first step acted as an active bridge layer and sacrificial template. It played a vital role in orienting the artificial coating layer through the template effect. The results show that the rod-like carbonated hydroxyapatite crystals grow into bundles, which are similar in size and appearance to prisms in human enamel, when using the two-step method with either aspartic acid or acidic glutamate (20.00 mmol/L). PMID:26046278

  10. Soil CO2 respiration: Comparison of chemical titration, CO2 IRGA analysis and the Solvita gel system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this research is to compare the results of measured soil CO2 respiration using three methods: (1) titration method; (2) Infrared gas analysis (IRGA); and (3) the Solvita gel system for soil CO2 analysis. We acquired 36 soil samples from across the USA for comparison which ranged in pH...

  11. Method of preparing and using and composition for acidizing subterranean formations

    SciTech Connect

    Dill, W.R.

    1984-08-21

    A composition and method of acidizing or fracturing a subterranean formation comprises contacting the formation with a composition comprising an acid, urea, and a selected gelling agent. The urea is present in an amount sufficient to extend the viscous stability of the gelled acid composition in comparison to the acid and gelling agent alone.

  12. HPLC method for the simultaneous quantification of the major organic acids in Angeleno plum fruit

    NASA Astrophysics Data System (ADS)

    Wang, Yanwei; Wang, Jing; Cheng, Wei; Zhao, Zhilei; Cao, Jiankang

    2014-08-01

    A method was developed to profile major organic acids in Angeleno fruit by high performance liquid chromatography. Organic acids in plum were extracted by water with ultra- sonication at 50°C for 30 min. The extracts were chromatographed on Waters Atlantis T3 C18 column (4.6 mm×250 mm, 5 μm) with 0.01mol/L sulfuric acid and water as mobile phase, and flow rate was 0.5 ml/min. The column temperature was 40C, and chromatography was monitored by a diode array detector at 210 nm. The result showed that malic acid, citric acid, tartaric acid, oxalic acid, pyruvic acid, acetic acid, succinic acid in Angeleno plum, and the malic acid was the major organic acids. The coefficient of determination of the standard calibration curve is R2 > 0.999. The organic acids recovery ranged from 99.11% for Malic acid to 106.70% for Oxalic acid, and CV (n=6) ranged from 0.95% for Malic acid to 6.23% for Oxalic acid, respectively. The method was accurate, sensitive and feasible in analyzing the organic acids in Angeleno plum.

  13. Functional hyaluronic acid hydrogels prepared by a novel method.

    PubMed

    Cui, Ning; Qian, Junmin; Zhao, Na; Wang, Hongjie

    2014-12-01

    In this study, a novel simple method was developed to prepare functional hyaluronic acid (HA) hydrogels simultaneously containing hydrazone and disulfide bonds in their crossbridges. The HA hydrogels were formed by directly reacting 2,5-hexanedione and 3,3'-dithiodipropionate hydrazide-modified HA, and were characterized by FT-IR, SEM, TGA and mechanical tests. The results showed that the formation of HA hydrogels was a result of the reaction between ketone and hydrazide groups. The resultant HA hydrogels exhibited a porous morphology with a pore size range of 50 μm to 400 μm, and their compressive modulus and G″/G' ratio were 18.8±0.6 kPa and 0.002, respectively. Both swelling and degradation ratios gradually decreased with the increasing degree of crosslinking. However, the degree of crosslinking had a slight effect on the decomposition temperature of the HA hydrogels. It can be concluded that the simple method presented in this study is feasible to prepare HA hydrogels through hydrazone bond crosslinking by reacting diketone molecules and hydrazide-modified HA, and the HA hydrogels have potential in biomedical applications. PMID:25491866

  14. 40 CFR Appendix A to Subpart Ddd... - Free Formaldehyde Analysis of Insulation Resins by the Hydroxylamine Hydrochloride Method

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... this method is the titration of the hydrochloric acid that is liberated when hydroxylamine... prestandardized pH meter, 1.0 N hydrochloric acid, 0.1 N hydrochloric acid, and 0.1 N sodium hydroxide. 5.5Add 50... adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N. 4.4Sodium hydroxide solution, 0.1 N....

  15. Universal nucleic acids sample preparation method for cells, spores and their mixture

    DOEpatents

    Bavykin, Sergei

    2011-01-18

    The present invention relates to a method for extracting nucleic acids from biological samples. More specifically the invention relates to a universal method for extracting nucleic acids from unidentified biological samples. An advantage of the presently invented method is its ability to effectively and efficiently extract nucleic acids from a variety of different cell types including but not limited to prokaryotic or eukaryotic cells and/or recalcitrant organisms (i.e. spores). Unlike prior art methods which are focused on extracting nucleic acids from vegetative cell or spores, the present invention effectively extracts nucleic acids from spores, multiple cell types or mixtures thereof using a single method. Important that the invented method has demonstrated an ability to extract nucleic acids from spores and vegetative bacterial cells with similar levels effectiveness. The invented method employs a multi-step protocol which erodes the cell structure of the biological sample, isolates, labels, fragments nucleic acids and purifies labeled samples from the excess of dye.

  16. Conformation and hydrogen ion titration of proteins: a continuum electrostatic model with conformational flexibility.

    PubMed

    You, T J; Bashford, D

    1995-11-01

    A new method for including local conformational flexibility in calculations of the hydrogen ion titration of proteins using macroscopic electrostatic models is presented. Intrinsic pKa values and electrostatic interactions between titrating sites are calculated from an ensemble of conformers in which the positions of titrating side chains are systematically varied. The method is applied to the Asp, Glu, and Tyr residues of hen lysozyme. The effects of different minimization and/or sampling protocols for both single-conformer and multi-conformer calculations are studied. For single-conformer calculations it is found that the results are sensitive to the choice of all-hydrogen versus polar-hydrogen-only atomic models and to the minimization protocol chosen. The best overall agreement of single-conformer calculations with experiment is obtained with an all-hydrogen model and either a two-step minimization process or minimization using a high dielectric constant. Multi-conformational calculations give significantly improved agreement with experiment, slightly smaller shifts between model compound pKa values and calculated intrinsic pKa values, and reduced sensitivity of the intrinsic pKa calculations to the initial details of the structure compared to single-conformer calculations. The extent of these improvements depends on the type of minimization used during the generation of conformers, with more extensive minimization giving greater improvements. The ordering of the titrations of the active-site residues, Glu-35 and Asp-52, is particularly sensitive to the minimization and sampling protocols used. The balance of strong site-site interactions in the active site suggests a need for including site-site conformational correlations. PMID:8580316

  17. Method for analyzing nucleic acids by means of a substrate having a microchannel structure containing immobilized nucleic acid probes

    DOEpatents

    Ramsey, J. Michael; Foote, Robert S.

    2002-01-01

    A method and apparatus for analyzing nucleic acids includes immobilizing nucleic probes at specific sites within a microchannel structure and moving target nucleic acids into proximity to the probes in order to allow hybridization and fluorescence detection of specific target sequences.

  18. Method for analyzing nucleic acids by means of a substrate having a microchannel structure containing immobilized nucleic acid probes

    DOEpatents

    Ramsey, J. Michael; Foote, Robert S.

    2003-12-09

    A method and apparatus for analyzing nucleic acids includes immobilizing nucleic probes at specific sites within a microchannel structure and moving target nucleic acids into proximity to the probes in order to allow hybridization and fluorescence detection of specific target sequences.

  19. AMDTreat 5.0+ with PHREEQC titration module to compute caustic chemical quantity, effluent quality, and sludge volume

    USGS Publications Warehouse

    Cravotta, Charles A., III; Means, Brent P; Arthur, Willam; McKenzie, Robert M; Parkhurst, David L.

    2015-01-01

    Alkaline chemicals are commonly added to discharges from coal mines to increase pH and decrease concentrations of acidity and dissolved aluminum, iron, manganese, and associated metals. The annual cost of chemical treatment depends on the type and quantities of chemicals added and sludge produced. The AMDTreat computer program, initially developed in 2003, is widely used to compute such costs on the basis of the user-specified flow rate and water quality data for the untreated AMD. Although AMDTreat can use results of empirical titration of net-acidic or net-alkaline effluent with caustic chemicals to accurately estimate costs for treatment, such empirical data are rarely available. A titration simulation module using the geochemical program PHREEQC has been incorporated with AMDTreat 5.0+ to improve the capability of AMDTreat to estimate: (1) the quantity and cost of caustic chemicals to attain a target pH, (2) the chemical composition of the treated effluent, and (3) the volume of sludge produced by the treatment. The simulated titration results for selected caustic chemicals (NaOH, CaO, Ca(OH)2, Na2CO3, or NH3) without aeration or with pre-aeration can be compared with or used in place of empirical titration data to estimate chemical quantities, treated effluent composition, sludge volume (precipitated metals plus unreacted chemical), and associated treatment costs. This paper describes the development, evaluation, and potential utilization of the PHREEQC titration module with the new AMDTreat 5.0+ computer program available at http://www.amd.osmre.gov/.

  20. Separating acetic acid from furol (furfural) by electrodialysis method

    SciTech Connect

    Guan, S.F.; Li, C.S. Ye, S.T.; Shen, S.Y.; Wang, Y.T.; Yu, S.H.

    1981-01-01

    Furfural production by hydrolysis of fibrous plant materials is accompanied by formation of acetic acid in amounts depending on the material used. The amount of acetic formed in the hydrolysis of the fruit shell of oil-tea camellia (Camellia oleosa) (an oilseed-bearing tree) is equal to the amount of furfural. The acetic acid can be separated from the furfural and concentrated to 10% by electrodialysis. A smaller amount of furfural is separated with acetic acid.

  1. A Novel Method for Presenting the Amino Acids in an Introductory Biochemistry Course.

    ERIC Educational Resources Information Center

    Kuehl, LeRoy

    1978-01-01

    Introduces an approach to teaching amino acids that employs the use of a poem containing information on the structure and properties of amino acids, and of slides illustrating the poem. Student response to the method was positive. (MA)

  2. VOLTAMMETRIC METHODS FOR DETERMINATION OF METAL BINDING BY FULVIC ACID

    EPA Science Inventory

    The use of anodic stripping voltammetry (ASV) and differential pulse polarography (DPP) for the measurement of the concentrations of aquo ions in the presence of fulvic acid, and the subsequent use of these data for estimation of the metal--fulvic acid conditional stability const...

  3. Positive End-expiratory Pressure Titration after Alveolar Recruitment Directed by Electrical Impedance Tomography

    PubMed Central

    Long, Yun; Liu, Da-Wei; He, Huai-Wu; Zhao, Zhan-Qi

    2015-01-01

    Background: Electrical impedance tomography (EIT) is a real-time bedside monitoring tool, which can reflect dynamic regional lung ventilation. The aim of the present study was to monitor regional gas distribution in patients with acute respiratory distress syndrome (ARDS) during positive-end-expiratory pressure (PEEP) titration using EIT. Methods: Eighteen ARDS patients under mechanical ventilation in Department of Critical Care Medicine of Peking Union Medical College Hospital from January to April in 2014 were included in this prospective observational study. After recruitment maneuvers (RMs), decremental PEEP titration was performed from 20 cmH2O to 5 cmH2O in steps of 3 cmH2O every 5–10 min. Regional over-distension and recruitment were monitored with EIT. Results: After RMs, patient with arterial blood oxygen partial pressure (PaO2) + carbon dioxide partial pressure (PaCO2) >400 mmHg with 100% of fractional inspired oxygen concentration were defined as RM responders. Thirteen ARDS patients was diagnosed as responders whose PaO2 + PaCO2 were higher than nonresponders (419 ± 44 mmHg vs. 170 ± 73 mmHg, P < 0.0001). In responders, PEEP mainly increased recruited pixels in dependent regions and over-distended pixels in nondependent regions. PEEP alleviated global inhomogeneity of tidal volume and end-expiratory lung volume. PEEP levels without significant alveolar derecruitment and over-distension were identified individually. Conclusions: After RMs, PEEP titration significantly affected regional gas distribution in lung, which could be monitored with EIT. EIT has the potential to optimize PEEP titration. PMID:26021494

  4. Clinical predictors of central sleep apnea evoked by positive airway pressure titration

    PubMed Central

    Moro, Marilyn; Gannon, Karen; Lovell, Kathy; Merlino, Margaret; Mojica, James; Bianchi, Matt T

    2016-01-01

    Purpose Treatment-emergent central sleep apnea (TECSA), also called complex apnea, occurs in 5%–15% of sleep apnea patients during positive airway pressure (PAP) therapy, but the clinical predictors are not well understood. The goal of this study was to explore possible predictors in a clinical sleep laboratory cohort, which may highlight those at risk during clinical management. Methods We retrospectively analyzed 728 patients who underwent PAP titration (n=422 split-night; n=306 two-night). Demographics and self-reported medical comorbidities, medications, and behaviors as well as standard physiological parameters from the polysomnography (PSG) data were analyzed. We used regression analysis to assess predictors of binary presence or absence of central apnea index (CAI) ≥5 during split-night PSG (SN-PSG) versus full-night PSG (FN-PSG) titrations. Results CAI ≥5 was present in 24.2% of SN-PSG and 11.4% of FN-PSG patients during titration. Male sex, maximum continuous positive airway pressure, and use of bilevel positive airway pressure were predictors of TECSA, and rapid eye movement dominance was a negative predictor, for both SN-PSG and FN-PSG patients. Self-reported narcotics were a positive predictor of TECSA, and the time spent in stage N2 sleep was a negative predictor only for SN-PSG patients. Self-reported history of stroke and the CAI during the diagnostic recording predicted TECSA only for FN-PSG patients. Conclusion Clinical predictors of treatment-evoked central apnea spanned demographic, medical history, sleep physiology, and titration factors. Improved predictive models may be increasingly important as diagnostic and therapeutic modalities move away from the laboratory setting, even as PSG remains the gold standard for characterizing primary central apnea and TECSA. PMID:27555802

  5. Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt

    NASA Technical Reports Server (NTRS)

    Sermon, Paul A.; Self, Valerie A.; Vong, Mariana S. W.; Wurie, Alpha T.

    1990-01-01

    The value of in situ analysis on CO chemisorption, titration and oxidation over supported Pt catalysts using calorimetry, catalytic and micro-FTIR methods is illustrated using silica- and titania-supported samples. Isothermal CO-O and O2-CO titrations have not been widely used on metal surfaces and may be complicated if some oxide supports are reduced by CO titrant. However, they can illuminate the kinetics of CO oxidation on metal/oxide catalysts since during such titrations all O and CO coverages are scanned as a function of time. There are clear advantages in following the rates of the catalyzed CO oxidation via calorimetry and gc-ms simultaneously. At lower temperatures the evidence they provide is complementary. CO oxidation and its catalysis of CO oxidation have been extensively studied with hysteresis and oscillations apparent, and the present results suggest the benefits of a combined approach. Silica support porosity may be important in defining activity-temperature hysteresis. FTIR microspectroscopy reveals the chemical heterogeneity of the catalytic surfaces used; it is interesting that the evidence with regard to the dominant CO surface species and their reactivities with regard to surface oxygen for present oxide-supported Pt are different from those seen on graphite-supported Pt.

  6. Protein-salt binding data from potentiometric titrations of lysozyme in aqueous solutions containing KCl

    SciTech Connect

    Engmann, J.; Blanch, H.W.; Prausnitz, J.M. |

    1997-03-01

    An existing method for potentiometric titrations of proteins was improved, tested and applied to titrations of the enzyme hen-egg-white lysozyme in aqueous solutions containing KCl at ionic strengths from 0.1 M to 2.0 M at 25 C. Information about the protein`s net charge dependence on pH and ionic strength were obtained and salt binding numbers for the system were calculated using a linkage concept. For the pH range 2.5--11.5, the net charge slightly but distinctly increases with increasing ionic strength between 0.1 M and 2.0 M. The differences are most distinct in the pH region below 5. Above pH 11.35, the net charge decreases with increasing ionic strength. Preliminary calculation of binding numbers from titration curves at 0.1 M and 1.0 M showed selective association of chloride anions and expulsion of potassium ions at low pH. Ion-binding numbers from this work will be used to evaluate thermodynamic properties and to correlate crystallization or precipitation phase-equilibrium data in terms of a model based on the integral-equation theory of fluids which is currently under development.

  7. EPR monitored redox titration of the cofactors of Saccharomyces cerevisiae Nar1.

    PubMed

    Hagedoorn, Peter-Leon; van der Weel, Laura; Hagen, Wilfred R

    2014-01-01

    Electron Paramagnetic Resonance (EPR) monitored redox titrations are a powerful method to determine the midpoint potential of cofactors in proteins and to identify and quantify the cofactors in their detectable redox state. The technique is complementary to direct electrochemistry (voltammetry) approaches, as it does not offer information on electron transfer rates, but does establish the identity and redox state of the cofactors in the protein under study. The technique is widely applicable to any protein containing an electron paramagnetic resonance (EPR) detectable cofactor. A typical titration requires 2 ml protein with a cofactor concentration in the range of 1-100 µM. The protein is titrated with a chemical reductant (sodium dithionite) or oxidant (potassium ferricyanide) in order to poise the sample at a certain potential. A platinum wire and a Ag/AgCl reference electrode are connected to a voltmeter to measure the potential of the protein solution A set of 13 different redox mediators is used to equilibrate between the redox cofactors of the protein and the electrodes. Samples are drawn at different potentials and the Electron Paramagnetic Resonance spectra, characteristic for the different redox cofactors in the protein, are measured. The plot of the signal intensity versus the sample potential is analyzed using the Nernst equation in order to determine the midpoint potential of the cofactor. PMID:25490157

  8. Concentration-related response potentiometric titrations to study the interaction of small molecules with large biomolecules.

    PubMed

    Hamidi-Asl, Ezat; Daems, Devin; De Wael, Karolien; Van Camp, Guy; Nagels, Luc J

    2014-12-16

    In the present paper, the utility of a special potentiometric titration approach for recognition and calculation of biomolecule/small-molecule interactions is reported. This approach is fast, sensitive, reproducible, and inexpensive in comparison to the other methods for the determination of the association constant values (Ka) and the interaction energies (ΔG). The potentiometric titration measurement is based on the use of a classical polymeric membrane indicator electrode in a solution of the small-molecule ligand. The biomolecule is used as a titrant. The potential is measured versus a reference electrode and transformed into a concentration-related signal over the entire concentration interval, also at low concentrations, where the millivolt (y-axis) versus log canalyte (x-axis) potentiometric calibration curve is not linear. In the procedure, Ka is calculated for the interaction of cocaine with a cocaine binding aptamer and with an anticocaine antibody. To study the selectivity and cross-reactivity, other oligonucleotides and aptamers are tested, as well as other small ligand molecules such as tetrakis(4-chlorophenyl)borate, metergoline, lidocaine, and bromhexine. The calculated Ka compared favorably to the value reported in the literature using surface plasmon resonance. The potentiometric titration approach called "concentration-related response potentiometry" is used to study molecular interaction for seven macromolecular target molecules and four small-molecule ligands. PMID:25390494

  9. Method for removing acid gases from a gaseous stream

    DOEpatents

    Gorin, Everett; Zielke, Clyde W.

    1981-01-01

    In a process for hydrocracking a heavy aromatic polynuclear carbonaceous feedstock containing reactive alkaline constituents to produce liquid hydrocarbon fuels boiling below about 475.degree. C. at atmospheric pressure by contacting the feedstock with hydrogen in the presence of a molten metal halide catalyst, thereafter separating a gaseous stream containing hydrogen, at least a portion of the hydrocarbon fuels and acid gases from the molten metal halide and regenerating the molten metal halide, thereby producing a purified molten metal halide stream for recycle to the hydrocracking zone, an improvement comprising; contacting the gaseous acid gas, hydrogen and hydrocarbon fuels-containing stream with the feedstock containing reactive alkaline constituents to remove acid gases from the acid gas containing stream. Optionally at least a portion of the hydrocarbon fuels are separated from gaseous stream containing hydrogen, hydrocarbon fuels and acid gases prior to contacting the gaseous stream with the feedstock.

  10. Method for nucleic acid hybridization using single-stranded DNA binding protein

    DOEpatents

    Tabor, Stanley; Richardson, Charles C.

    1996-01-01

    Method of nucleic acid hybridization for detecting the presence of a specific nucleic acid sequence in a population of different nucleic acid sequences using a nucleic acid probe. The nucleic acid probe hybridizes with the specific nucleic acid sequence but not with other nucleic acid sequences in the population. The method includes contacting a sample (potentially including the nucleic acid sequence) with the nucleic acid probe under hybridizing conditions in the presence of a single-stranded DNA binding protein provided in an amount which stimulates renaturation of a dilute solution (i.e., one in which the t.sub.1/2 of renaturation is longer than 3 weeks) of single-stranded DNA greater than 500 fold (i.e., to a t.sub.1/2 less than 60 min, preferably less than 5 min, and most preferably about 1 min.) in the absence of nucleotide triphosphates.

  11. Titrating-Delay Matching-to-Sample in the Pigeon

    ERIC Educational Resources Information Center

    Kangas, Brian D.; Vaidya, Manish; Branch, Marc N.

    2010-01-01

    The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and…

  12. Titrating-delay matching-to-sample in the pigeon.

    PubMed

    Kangas, Brian D; Vaidya, Manish; Branch, Marc N

    2010-07-01

    The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and incorrect matches decrease the delay, and steady-state titrated delays serve as the primary dependent measure. The present series of experiments investigated the effects of several procedural variables on performance in TDMTS procedures in an effort to elucidate better its features to allow for more precision in future use. Experiment 1 reports results from a parametric analysis of fixed-ratio response requirements on the sample key that indicated improved remembering in the form of higher daily titrated delay values as the requirement was increased. Experiment 2 investigated the extent to which the initial delay value in each session affected session-wide delay values. Results indicated that regardless of value of the initial delay, the subjects' performances adjusted the delay values in the direction of the known baseline delay-value levels. Experiment 3 manipulated the step size by which delay values were adjusted and the results indicated that larger step sizes increased both session-to-session variability and within-session range of titrated delay values, although the average values remained approximately the same. These results suggest that the TDMTS task serves as a promising procedure to study what many refer to as memory. PMID:21279163

  13. Coulometric calcium pump for thin layer sample titrations.

    PubMed

    Ghahraman Afshar, Majid; Crespo, Gastón A; Bakker, Eric

    2015-10-01

    A selective electrochemical calcium pump based on a fast diffusive calcium ionophore-based membrane is reported. An initially nonpolarized ionophore-based membrane allows one to establish a net calcium flux by applying a potential step function (i.e., 250 mV for 30 s). The resulting calcium flux is released into a microliter scale thin layer reservoir, and the resulting ion perturbation is monitored by either a potentiometric or a coulometric readout. This chemical perturbation in the thin layer thus acts as a titration agent that is precisely controlled by coulometry. A linear correlation between released and detected calcium is confirmed by the two different readout modes. Having demonstrated the efficiency of the calcium pump in background electrolyte solutions, a complexometric titration with known concentrations of EDTA in the thin layer sample was performed. With the potentiometric readout, titrations in the range of 0.25-0.75 mM gave a precision of 3%, whereas the coulometric readout gave a range of 0.02-0.12 mM and a precision of 2%. Improved precision is expected by better control of the thin layer geometry by microfabrication. The significance of this work is that the coupling of a selective calcium pump with a thin layer element can give rise to rapid and complete sample concentration changes and result in a promising platform for titrations either on the laboratory bench or for in situ measurements in environmental or diagnostic settings. PMID:26348131

  14. Nucleic acid detection system and method for detecting influenza

    SciTech Connect

    Cai, Hong; Song, Jian

    2015-03-17

    The invention provides a rapid, sensitive and specific nucleic acid detection system which utilizes isothermal nucleic acid amplification in combination with a lateral flow chromatographic device, or DNA dipstick, for DNA-hybridization detection. The system of the invention requires no complex instrumentation or electronic hardware, and provides a low cost nucleic acid detection system suitable for highly sensitive pathogen detection. Hybridization to single-stranded DNA amplification products using the system of the invention provides a sensitive and specific means by which assays can be multiplexed for the detection of multiple target sequences.

  15. Reliability and uncertainty in the estimation of pKa by least squares nonlinear regression analysis of multiwavelength spectrophotometric pH titration data.

    PubMed

    Meloun, Milan; Syrový, Tomás; Bordovská, Sylva; Vrána, Ales

    2007-02-01

    When drugs are poorly soluble then, instead of the potentiometric determination of dissociation constants, pH-spectrophotometric titration can be used along with nonlinear regression of the absorbance response surface data. Generally, regression models are extremely useful for extracting the essential features from a multiwavelength set of data. Regression diagnostics represent procedures for examining the regression triplet (data, model, method) in order to check (a) the data quality for a proposed model; (b) the model quality for a given set of data; and (c) that all of the assumptions used for least squares hold. In the interactive, PC-assisted diagnosis of data, models and estimation methods, the examination of data quality involves the detection of influential points, outliers and high leverages, that cause many problems when regression fitting the absorbance response hyperplane. All graphically oriented techniques are suitable for the rapid estimation of influential points. The reliability of the dissociation constants for the acid drug silybin may be proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data. The uncertainty in the measurement of the pK (a) of a weak acid obtained by the least squares nonlinear regression analysis of absorption spectra is calculated. The procedure takes into account the drift in pH measurement, the drift in spectral measurement, and all of the drifts in analytical operations, as well as the relative importance of each source of uncertainty. The most important source of uncertainty in the experimental set-up for the example is the uncertainty in the pH measurement. The influences of various sources of uncertainty on the accuracy and precision are discussed using the example of the mixed dissociation constants of silybin, obtained using the SQUAD(84) and SPECFIT/32 regression programs. PMID:17216158

  16. Comparative Oxidative Stability of Fatty Acid Alkyl Esters by Accelerated Methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several fatty acid alkyl esters were subjected to accelerated methods of oxidation, including EN 14112 (Rancimat method) and pressurized differential scanning calorimetry (PDSC). Structural trends elucidated from both methods that improved oxidative stability included decreasing the number of doubl...

  17. Ketol-acid reductoisomerase enzymes and methods of use

    DOEpatents

    Govindarajan, Sridhar; Li, Yougen; Liao, Der-Ing; O'Keefe, Daniel P.; Minshull, Jeremy Stephen; Rothman, Steven Cary; Tobias, Alexander Vincent

    2016-07-12

    Provided herein are polypeptides having ketol-acid reductoisomerase activity as well as microbial host cells comprising such polypeptides. Polypeptides provided herein may be used in biosynthetic pathways, including, but not limited to, isobutanol biosynthetic pathways.

  18. Methods for producing 3-hydroxypropionic acid and other products

    DOEpatents

    Lynch, Michael D.; Gill, Ryan T.; Lipscomb, Tanya E. W.

    2016-07-12

    This invention relates to metabolically engineered microorganism strains, such as bacterial strains, in which there is an increased utilization of malonyl-CoA for production of a chemical product, which includes 3-hydroxypropionic acid.

  19. Materials and methods for efficient lactic acid production

    DOEpatents

    Zhou, Shengde; Ingram, Lonnie O'Neal; Shanmugam, Keelnatham T.; Yomano, Lorraine; Grabar, Tammy B.; Moore, Jonathan C.

    2009-12-08

    The present invention provides derivatives of ethanologenic Escherichia coli K011 constructed for the production of lactic acid. The transformed E. coli of the invention are prepared by deleting the genes that encode competing pathways followed by a growth-based selection for mutants with improved performance. These transformed E. coli are useful for providing an increased supply of lactic acid for use in food and industrial applications.

  20. Materials and methods for efficient lactic acid production

    SciTech Connect

    Zhou, Shengde; Ingram, Lonnie O'Neal; Shanmugam, Keelnatham T; Yomano, Lorraine; Grabar, Tammy B; Moore, Jonathan C

    2013-04-23

    The present invention provides derivatives of Escherichia coli constructed for the production of lactic acid. The transformed E. coli of the invention are prepared by deleting the genes that encode competing pathways followed by a growth-based selection for mutants with improved performance. These transformed E. coli are useful for providing an increased supply of lactic acid for use in food and industrial applications.

  1. A method for measuring fatty acid oxidation in C. elegans.

    PubMed

    Elle, Ida Coordt; Rødkær, Steven Vestergaard; Fredens, Julius; Færgeman, Nils Joakim

    2012-01-01

    The nematode C. elegans has during the past decade proven to be a valuable model organism to identify and examine molecular mechanisms regulating lipid storage and metabolism. While the primary approach has been to identify genes and pathways conferring alterations in lipid accumulation, only a few recent studies have recognized the central role of fatty acid degradation in cellular lipid homeostasis. In the present study, we show how complete oxidation of fatty acids can be determined in live C. elegans by examining oxidation of tritium-labeled fatty acids to tritiated H2O that can be measured by scintillation counting. Treating animals with sodium azide, an inhibitor of the electron transport chain, reduced (3)H2O production to approximately 15%, while boiling of animals prior to assay completely blocked the production of labeled water. We demonstrate that worms fed different bacterial strains exhibit different fatty acid oxidation rates. We show that starvation results in increased fatty acid oxidation, which is independent of the transcription factor NHR-49. On the contrary, fatty acid oxidation is reduced to approximately 70% in animals lacking the worm homolog of the insulin receptor, DAF-2. Hence, the present methodology can be used to delineate the role of specific genes and pathways in the regulation of β-oxidation in C. elegans. PMID:24058820

  2. ASSESSMENT OF ATTENTION THRESHOLD IN RATS BY TITRATION OF VISUAL CUE DURATION DURING THE FIVE CHOICE SERIAL REACTION TIME TASK

    PubMed Central

    Martin, Thomas J.; Grigg, Amanda; Kim, Susy A.; Ririe, Douglas G.; Eisenach, James C.

    2014-01-01

    Background The 5 choice serial reaction time task (5CSRTT) is commonly used to assess attention in rodents. We sought to develop a variant of the 5CSRTT that would speed training to objective success criteria, and to test whether this variant could determine attention capability in each subject. New Method Fisher 344 rats were trained to perform a variant of the 5CSRTT in which the duration of visual cue presentation (cue duration) was titrated between trials based upon performance. The cue duration was decreased when the subject made a correct response, or increased with incorrect responses or omissions. Additionally, test day challenges were provided consisting of lengthening the intertrial interval and inclusion of a visual distracting stimulus. Results Rats readily titrated the cue duration to less than 1 sec in 25 training sessions or less (mean ± SEM, 22.9 ± 0.7), and the median cue duration (MCD) was calculated as a measure of attention threshold. Increasing the intertrial interval increased premature responses, decreased the number of trials completed, and increased the MCD. Decreasing the intertrial interval and time allotted for consuming the food reward demonstrated that a minimum of 3.5 sec is required for rats to consume two food pellets and successfully attend to the next trial. Visual distraction in the form of a 3 Hz flashing light increased the MCD and both premature and time out responses. Comparison with existing method The titration variant of the 5CSRTT is a useful method that dynamically measures attention threshold across a wide range of subject performance, and significantly decreases the time required for training. Task challenges produce similar effects in the titration method as reported for the classical procedure. Conclusions The titration 5CSRTT method is an efficient training procedure for assessing attention and can be utilized to assess the limit in performance ability across subjects and various schedule manipulations. PMID

  3. Humic substance charge determination by titration with a flexible cationic polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Tan, Wen-Feng; Norde, Willem; Koopal, Luuk K.

    2011-10-01

    The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1-1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the "Mütek particle charge detector" which allows determination of the Mütek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mütek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC-HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS-polyDADMAC complex can be obtained. In general, for polyDADMAC-HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1-1 background electrolyte. Cation incorporation can be neglected at 1-1 electrolyte concentrations ⩽ 1 mmol L -1 and a 1-1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L -1 KCl by 30% and at 150 mmol L -1 KCl by 12%. On the other hand, increasing amounts of K + become incorporated in the complex: at 5 mmol L -1 KCl 5% and at 150 mmol L -1 KCl 24% of the PAHA charge is balanced by K +. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K + incorporation, it is found that

  4. Rapid detection method for fusaric acid-producing species of Fusarium by PCR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fusaric acid is a mycotoxin produced by species of the fungus Fusarium and can act synergistically with other Fusarium toxins. In order to develop a specific detection method for fusaric acid-producing fungus, PCR prim¬ers were designed to amplify FUB10, a transcription factor gene in fusaric acid ...

  5. Titration of African swine fever (ASF) virus.

    PubMed

    Enjuanes, L; Carrascosa, A L; Moreno, M A; Viñuela, E

    1976-09-01

    A haemadsorption microtest for African swine fever (ASF) virus is described. This assay is as sensitive and its response is faster than the conventional assay which uses buffy coat cultures in Leighton tubes. The method can also process a larger number of samples by using smaller amounts of swine blood and laboratory space. A plaque assay for ASF virus adapted to grow in VERO cells gives a titre similar to that obtained using the haemadsorption microtest. In both the micromethod and the plaque assay infection may be produced by a single infective particle. PMID:823294

  6. Determination of Calcium in Dietary Supplements: Statistical Comparison of Methods in the Analytical Laboratory

    ERIC Educational Resources Information Center

    Garvey, Sarah L.; Shahmohammadi, Golbon; McLain, Derek R.; Dietz, Mark L.

    2015-01-01

    A laboratory experiment is described in which students compare two methods for the determination of the calcium content of commercial dietary supplement tablets. In a two-week sequence, the sample tablets are first analyzed via complexometric titration with ethylenediaminetetraacetic acid and then, following ion exchange of the calcium ion present…

  7. Study on the interaction of morphine chloride with deoxyribonucleic acid by fluorescence method

    NASA Astrophysics Data System (ADS)

    Li, J. F.; Dong, C.

    2009-01-01

    The mode and mechanism of the interaction of morphine chloride, an important alkaloid compound to calf thymus deoxyribonucleic acid (ct DNA) was investigated from absorption and fluorescence titration techniques. Hypochromic effect was founded in the absorption spectra of morphine when concentration of DNA increased. The decreased fluorescence study revealed non-cooperative binding of the morphine to DNA with an affinity of 3.94 × 10 3 M -1, and the stoichiometry of binding was characterized to be about one morphine molecule per nucleotide. Stern-Volmer plots at different temperatures proved that the quenching mechanism was static. Ferrocyanide quenching study showed that the magnitude of KSV of the bound morphine was lower than that of the free one. In addition, it was found that ionic strength could affect the binding of morphine and DNA. Fluorescence polarization and denatured DNA studies also applied strong evidences that morphine molecule was partially intercalated between every alternate base pairs of ct DNA. As observed from above experiments, intercalation was well supported as the binding mode of morphine and ct DNA.

  8. A new method for quantitative determination of two uronic acids by CZE with direct UV detection.

    PubMed

    Xia, Yong-gang; Liang, Jun; Yang, Bing-you; Wang, Qiu-hong; Kuang, Hai-xue

    2011-09-01

    A new method using capillary zone electrophoresis was developed for the rapid quantification of two common uronic acids, galacturonic acid and glucuronic acid, based on utilization of an alkaline background electrolyte with reversed electroosmotic flow (EOF) within 16 min. The method relies on in-capillary reaction and direct UV detection at the wavelength 270 nm. The optimum electrolyte solution was prepared of 130 mm sodium hydroxide, 36 mm disodium hydrogen phosphate dihydrate and 0.5 mm cetyltrimethylammonium bromide. EOF was reversed to detect uronic acids and to improve the separation of neutral sugars. The established method was validated and the results showed good linearity, high precision and satisfactory sensitivity. The newly developed method was successfully applied to analyze galacturonic acid and glucuronic acid content in Forsythia suspensa polysaccharides. The method is fast since only sample hydrolysis and dilution are required in the sample preparation. PMID:21154888

  9. Application of isothermal titration calorimeter for screening bitterness-suppressing molecules of quinine.

    PubMed

    Zhang, Yifan; Zhu, Youwei; Zhao, Na; Wu, Jinhui; Hu, Yiqiao

    2016-01-01

    Bitterness-suppressing molecules have drawn ever-increasing attention these years for some unique advantages like low molecular weight, tastelessness and no interference on drug bioavailability. L-Arg was reported to suppress the bitterness of quinine, and we happened to find that the suppressing effects could be demonstrated by isothermal titration calorimeter (ITC). In this study, we investigated the possibility of using ITC to screen bitterness-suppressing molecules for quinine. Among the amino acids we screened, L-Lys bond quinine with high affinity. The results of ITC correlated well with the results of human sensory experiments. L-Arg and L-Lys could suppress the bitterness of quinine while other amino acids could not. Therefore, ITC has the potential to screen bitterness-suppressing molecules. PMID:26213068

  10. Method for promoting specific alignment of short oligonucleotides on nucleic acids

    DOEpatents

    Studier, F. William; Kieleczawa, Jan; Dunn, John J.

    1996-01-01

    Disclosed is a method for promoting specific alignment of short oligonucleotides on a nucleic acid polymer. The nucleic acid polymer is incubated in a solution containing a single-stranded DNA-binding protein and a plurality of oligonucleotides which are perfectly complementary to distinct but adjacent regions of a predetermined contiguous nucleotide sequence in the nucleic acid polymer. The plurality of oligonucleotides anneal to the nucleic acid polymer to form a contiguous region of double stranded nucleic acid. Specific application of the methods disclosed include priming DNA synthesis and template-directed ligation.

  11. Spectrophotometric determination of tranexamic acid with chloranil.

    PubMed

    Wahbi, A A; Lotfi, E A; Aboul-Enein, H Y

    1984-01-01

    Tranexamic acid is reacted with aqueous alcoholic chloranil, buffered at pH 9, to give a complex with maximum absorption at 346 nm and with an apparent molar absorptivity of 15.7 x 10(3) l.mole(-1).cm(-1). A(max) is linearly related to concentration over the range 2-10 mug ml . When applied to tablets labelled as containing 500 mg each, the mean found was 496 +/- 4 mg. The results were comparable with those of the traditional formol titration method for amino-acids. PMID:18963530

  12. Cadmium binding to a histidine-rich glycoprotein from marine mussel blood plasma: potentiometric titration and equilibrium speciation modeling.

    PubMed

    Nair, P S; Robinson, W E

    2001-07-01

    Cadmium-binding parameters (conditional stability constants and carrying capacities) of Mytilus edulis blood plasma histidine-rich glycoprotein (HRG) were investigated by potentiometric titrations using a Cd ion-specific electrode. Titration data were applied to a single-component complexation model and expressed as Scatchard plots that were analyzed using the graphical curve peeling method and the algebraic statistical mechanical method. These sets of binding parameters, derived for the purified HRG, were subsequently entered into the geochemical speciation model MINTEQA2 and then used to simulate the experimental titration, thereby determining which set of log K and CL values best represented the titration data. The Cd binding to HRG was best described by a two-class model with log K values of 7.65 +/- 0.10 and 5.41 +/- 0.06 M-1 and carrying capacities of 6.0 +/- 1.2 and 9.5 +/- 0.4 sites/molecule, respectively. At concentration of total Cd measured in the blood plasma of field-collected mussels (< or = 2 x 10(-7) M), plasma Cd speciation would be dominated by the strong affinity sites of HRG (> 93.5% of total Cd binds to HRG), whereas HRG itself would only be 0.05% saturated with Cd, indicating a high-capacity, apparently nonsaturable Cd transport system. PMID:11434304

  13. Titrating the Cost of Plant Toxins Against Predators: a Case Study with Common Duikers, Sylvicapra grimmia.

    PubMed

    Abu Baker, Mohammad A

    2015-10-01

    Foragers face many variables that influence their food intake. These may include habitat structure, time, climate, resource characteristic, food quality, and plant defenses. I conducted foraging experiments using common duikers that involved: 1) testing the effect of plant toxins on foraging, and 2) titrating toxin intake against safety. I used giving up densities (GUDs, food remaining after foraging) to test for selection among trays containing alfalfa pellets treated with water, with 10% oxalic acid, or 10% quebracho tannin. Pairs of trays were placed within islands of woody vegetation and out in open grass. I also conducted a titration experiment by offering the duikers a choice between a patch with water-treated pellets placed at a risky site, or a patch with one of three oxalic acid-treated pellets at a safe site. This made it possible to determine the concentration of oxalic acid at which the cost of toxin in the safe site equals the predation cost at the risky site. The common duikers showed no selectivity among the three treatments at 10% concentration, however, GUDs in the open grass (i.e., safe) were significantly lower than in the wooded islands (i.e., risky). As the oxalic acid concentration increased at the safe sites, the duiker's food intake from the risky sites increased significantly. The results demonstrate that foraging hazards may come in different forms such as predation and plant toxins, and their interactions may alter habitat use, foraging patterns, and perceptions of risk. These variables occur under natural situations, altering the overall habitat quality. PMID:26364293

  14. Development and Validation of an LC-MS-MS Method for Determination of Simvastatin and Simvastatin Acid in Human Plasma: Application to a Pharmacokinetic Study.

    PubMed

    Partani, Pankaj; Verma, Saurabh Manaswita; Monif, Tausif

    2016-09-01

    A liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of simvastatin (SV) and simvastatin acid (SVA) in human plasma. To improve assay sensitivity and achieve simultaneous analysis, SVA monitored in (-)ESI (electrospray ionization) mode within the first 4.5 min and SV thereafter in (+)ESI mode. The separation of all compounds was achieved in about 6.2 min using a C18 reverse-phase fused-core(®) column (Ascentis(®) Express C18) and a mobile phase, which was composed of 2.00 ± 0.05 mM ammonium acetate buffer titrated to pH 3.8 with glacial acetic acid-acetonitrile (25:75, v/v), in isocratic mode at a flow rate of 0.500 mL/min. Additionally, a solid-phase extraction step was performed to reduce any ion-suppression and/or enhancement effects. The developed method was linear in the concentration range of 0.100-74.626 ng/mL for SV, and 0.100-48.971 ng/mL for SVA, with correlation coefficient greater than 0.99 for both analytes. The method has shown tremendous reproducibility, with intra- and inter-day precision <7.6%, and intra- and interday accuracy within ±10.9% of nominal values, for the both analytes. The method was successfully applied to characterize the pharmacokinetic profiles of SV and SVA following an oral administration of 40 mg SV tablet to healthy human volunteers. PMID:27226460

  15. NITRIC ACID SHOOTOUT: FIELD COMPARISON OF MEASUREMENT METHODS (JOURNAL VERSION)

    EPA Science Inventory

    Eighteen instruments for measuring atmospheric concentrations of nitric acid were compared in an eight-day field study at Pomona College, situated in the eastern portion of the Los Angeles Basin, in September 1985. The study design included collocated and separated duplicate samp...

  16. Improved method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.; Kaplan, L.; Mason, G.W.

    1983-07-26

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions uses a new series of neutral bi-functional extractants, the alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high-level nuclear reprocessing waste solutions.

  17. Scopolamine Effects Under a Titrating-Delayed-Nonmatching-to-Position Procedure

    ERIC Educational Resources Information Center

    Porritt, M.; Poling, A.

    2008-01-01

    In a study of working memory, the performance of rats under titrating-delayed-nonmatching- to-position (TDNMTP) procedures was examined. Overall accuracy and the number of trials completed were inversely related to titration value, whereas the highest delay attained was directly related to titration value. When given intraperitoneally,…

  18. COMPARISON OF THREE METHODS FOR MEASUREMENT OF ATMOSPHERIC NITRIC ACID AND AEROSOL NITRATE AND AMMONIUM

    EPA Science Inventory

    Three methods for measuring gaseous ambient nitric acid in the low concentration range 0-15 mcg/cum were compared under field conditions in southwestern Ontario during June 1-14, 1982. The methods employed were (1) tunable diode laser absorption, (2) a tungstic acid denuder tube,...

  19. Methods for point-of-care detection of nucleic acid in a sample

    DOEpatents

    Bearinger, Jane P.; Dugan, Lawrence C.

    2015-12-29

    Provided herein are methods and apparatus for detecting a target nucleic acid in a sample and related methods and apparatus for diagnosing a condition in an individual. The condition is associated with presence of nucleic acid produced by certain pathogens in the individual.

  20. Acid retardation method in analysis of strongly acidic solutions by inductively coupled plasma mass-spectrometry.

    PubMed

    Seregina, I F; Perevoznik, O A; Bolshov, M A

    2016-10-01

    Acid retardation on the sorbents as a technique for reduction of the acidity of the solutions prior to their analysis by inductively coupled plasma mass spectrometry was proposed and investigated. The proposed scheme provides substantial separation of the analytes and nitric acid, which allows direct introduction of the eluates in plasma without dilution. Two sorbents were examined - AV-17 anion-exchange resin and the Stirosorb 584 sorbent. Sorption and desorption of 38 elements on these sorbents were investigated. The efficiencies of the REEs' sorption on the anion-exchange and neutral sorbents were compared. The higher efficiency of the REEs and HNO3 separation was revealed for the neutral Stirosorb 584 sorbent. It was also found that most elements come out quantitatively of the column filled with the AV-17 resin after pumping 2-4mL of the solution. Wherein, the concentration of nitric acid decreased by 20 times. The anomalous behaviour of Ag, Pb, Th and U on the AV-17 resin was found. These analytes were eluted only after pumping 4 column volumes of deionized water. Na, K, Fe, Al and Li in concentrations within (50-1000mgL(-1)) range did not affect the recovery of REEs. The potential of ARM technique was demonstrate by the analysis of puriss. HNO3 and silverware. ARM enables to avoid dilution of highly acidic solutions prior to their introduction in ICP-MS. PMID:27474322

  1. Propagation and Titration of West Nile Virus on Vero Cells.

    PubMed

    McAuley, Alexander J; Beasley, David W C

    2016-01-01

    The propagation and titration of viruses are key virological techniques. Unlike other flaviviruses, such as the dengue viruses, West Nile virus (WNV) grows and plaques very efficiently on Vero cells, usually inducing strong cytopathic effect (CPE) and forming clear plaques. Here, we outline the steps for propagating WNV from culture supernatant stocks and homogenized organ/mosquito samples, as well as for determining virus titers in samples by serial-dilution plaque assay using neutral red or crystal violet stains. PMID:27188547

  2. Potentiometric titrations of rutile suspensions to 250 C

    SciTech Connect

    Machesky, M.L.; Wesolowski, D.J.; Palmer, D.A.; Ichiro-Hayashi, Ken

    1998-04-15

    A stirred hydrogen electrode concentration cell was used to conduct potentiometric titrations of rutile suspensions from 25 to 250 C in NaCl and tetramethylammonium chloride media (0.03 to 1.1 m). Hydrothermal pretreatment of the rutile improved titration reproducibility, decreased titration hysteresis, and facilitated determination of the point of zero net proton charge (pHznpc). These pHznpc values are 5.4, 5.1, 4.7, 4.4, 4.3 ({+-} 0.2 pH units), and 4.2 ({+-} 0.3 pH units) at 25, 50, 100, 150, 200, and 250 C, respectively. The difference between these pHznpc values and 1/2 pK{sub w} (the neutral pH of water) is rather constant between 25 and 250 C ({minus} 1.45 {+-} 0.2). This constancy is useful for predictive purposes and, more fundamentally, may reflect similarities between the hydration behavior of surface hydroxyl groups and water. A three-layer, 1pKa surface complexation model with three adjustable parameters (two capacitance values and one counterion binding constant) adequately described all titration data. The most apparent trend in these data for pH values greater than the pHznpc was the increase in proton release (negative surface charge) with increasing temperature. This reflects more efficient screening by Na{sup +} relative to Cl{sup {minus}}. Replacing Na{sup +} with the larger tetramethylammonium cation for some conditions resulted in decreased proton release due to the less efficient screening of negative surface charge by this larger cation.

  3. Chelate titrations of Ca(2+) and Mg(2+) using microfluidic paper-based analytical devices.

    PubMed

    Karita, Shingo; Kaneta, Takashi

    2016-06-14

    We developed microfluidic paper-based analytical devices (μPADs) for the chelate titrations of Ca(2+) and Mg(2+) in natural water. The μPAD consisted of ten reaction zones and ten detection zones connected through narrow channels to a sample zone located at the center. Buffer solutions with a pH of 10 or 13 were applied to all surfaces of the channels and zones. Different amounts of ethylenediaminetetraacetic acid (EDTA) were added to the reaction zones and a consistent amount of a metal indicator (Eriochrome Black T or Calcon) was added to the detection zones. The total concentrations of Ca(2+) and Mg(2+) (total hardness) in the water were measured using a μPAD containing a buffer solution with a pH of 10, whereas only Ca(2+) was titrated using a μPAD prepared with a potassium hydroxide solution with a pH of 13. The μPADs permitted the determination of Ca(2+) and Mg(2+) in mineral water, river water, and seawater samples within only a few minutes using only the naked eye-no need of instruments. PMID:27181645

  4. STATISTICAL VALIDATION OF SULFATE QUANTIFICATION METHODS USED FOR ANALYSIS OF ACID MINE DRAINAGE

    EPA Science Inventory

    Turbidimetric method (TM), ion chromatography (IC) and inductively coupled plasma atomic emission spectrometry (ICP-AES) with and without acid digestion have been compared and validated for the determination of sulfate in mining wastewater. Analytical methods were chosen to compa...

  5. The potentiometric titration of fluoride using pH electrodes

    SciTech Connect

    Selig, W.S.

    1987-07-01

    Sodium fluoride solutions with an initial pH of 4.46 yielded poorly defined endpoint breaks with a pH electrode system and Ce(III) or La(III) as titrants. At this initial pH, however, the fluoride ISE yielded acceptable S-shaped titration curves. At an initial pH of 6.30, both electrode systems and titrant combinations yielded acceptable endpoint breaks and titration curves. While a partially nonaqueous medium (50% methanol) enhanced the steepness of the endpoint breaks, the standard deviation also increased. This was possibly caused by evaporation of some of the solvent. We therefore do not see the necessity for, nor recommend a partially nonaqueous medium. There is no advantage in using Ce(III) rather than La(III) as titrant. Increasing the initial pH from 4.46 to 6.3 decreased the mean normality of the titrant (or increased the titration volume) for both electrode systems and titrants. We therefore recommend that the sodium fluoride standard solutions be adjusted to the same pH as the samples to be determined. For the most accurate results, the standardization should be done with a good approximation of the salt content of the unknown solution.

  6. Impact of Residual Inducer on Titratable Expression Systems

    PubMed Central

    Afroz, Taliman; Luo, Michelle L.; Beisel, Chase L.

    2015-01-01

    Inducible expression systems are widely employed for the titratable control of gene expression, yet molecules inadvertently present in the growth medium or synthesized by the host cells can alter the response profile of some of these systems. Here, we explored the quantitative impact of these residual inducers on the apparent response properties of inducible systems. Using a simple mathematical model, we found that the presence of residual inducer shrinks the apparent dynamic range and causes the apparent Hill coefficient to converge to one. We also found that activating systems were more sensitive than repressing systems to the presence of residual inducer and the response parameters were most heavily dependent on the original Hill coefficient. Experimental interrogation of common titratable systems based on an L-arabinose inducible promoter or a thiamine pyrophosphate-repressing riboswitch in Escherichia coli confirmed the predicted trends. We finally found that residual inducer had a distinct effect on “all-or-none” systems, which exhibited increased sensitivity to the added inducer until becoming fully induced. Our findings indicate that residual inducer or repressor alters the quantitative response properties of titratable systems, impacting their utility for scientific discovery and pathway engineering. PMID:26348036

  7. Fentanyl buccal tablet for breakthrough cancer pain: why titrate?

    PubMed

    Kleeberg, Ulrich R; Filbet, Marilène; Zeppetella, Giovambattista

    2011-01-01

    Breakthrough cancer pain is a significant problem for many patients with cancer because of the fast onset and often unpredictable nature of the pain episodes. The rapid onset opioids therefore have a central role to play in the management of breakthrough cancer pain. The rapid onset opioid fentanyl buccal tablet provides a fast analgesic effect and is easy to administer. However, titration of the medication is essential in order to optimize the management of pain. This is because individual patient characteristics, comorbidities, and other treatments may influence the absorption, pharmacokinetics, and pharmacodynamics of drugs. It is therefore important to individualize treatment by determining the effective dose for each patient, which is the dose that provides adequate analgesia and minimizes undesirable adverse effects. Data from clinical studies of fentanyl buccal tablet show that patients' effective doses ranged from 100 to 800 µg per episode, highlighting the need for the titration process. Following successful dose titration, treatment with fentanyl buccal tablet can achieve significant pain relief as early as 10 minutes after administration, resulting in a high level of patient satisfaction. PMID:20807349

  8. Impact of Residual Inducer on Titratable Expression Systems.

    PubMed

    Afroz, Taliman; Luo, Michelle L; Beisel, Chase L

    2015-01-01

    Inducible expression systems are widely employed for the titratable control of gene expression, yet molecules inadvertently present in the growth medium or synthesized by the host cells can alter the response profile of some of these systems. Here, we explored the quantitative impact of these residual inducers on the apparent response properties of inducible systems. Using a simple mathematical model, we found that the presence of residual inducer shrinks the apparent dynamic range and causes the apparent Hill coefficient to converge to one. We also found that activating systems were more sensitive than repressing systems to the presence of residual inducer and the response parameters were most heavily dependent on the original Hill coefficient. Experimental interrogation of common titratable systems based on an L-arabinose inducible promoter or a thiamine pyrophosphate-repressing riboswitch in Escherichia coli confirmed the predicted trends. We finally found that residual inducer had a distinct effect on "all-or-none" systems, which exhibited increased sensitivity to the added inducer until becoming fully induced. Our findings indicate that residual inducer or repressor alters the quantitative response properties of titratable systems, impacting their utility for scientific discovery and pathway engineering. PMID:26348036

  9. Method for construction of bacterial strains with increased succinic acid production

    DOEpatents

    Donnelly, Mark I.; Sanville-Millard, Cynthia; Chatterjee, Ranjini

    2000-01-01

    A fermentation process for producing succinic acid is provided comprising selecting a bacterial strain that does not produce succinic acid in high yield, disrupting the normal regulation of sugar metabolism of said bacterial strain, and combining the mutant bacterial strain and selected sugar in anaerobic conditions to facilitate production of succinic acid. Also provided is a method for changing low yield succinic acid producing bacteria to high yield succinic acid producing bacteria comprising selecting a bacterial strain having a phosphotransferase system and altering the phosphotransferase system so as to allow the bacterial strain to simultaneously metabolize different sugars.

  10. Validated UPLC method for determination of unbound bile acids in colesevelam HCl tablets.

    PubMed

    Vallapragada, Venkata Vivekanand; Inti, Gopichand; Vidiyala, Sudhakar Rao; Jadi, Sreeramulu

    2015-01-01

    A simple, precise and accurate gradient reverse-phase ultra-performance liquid chromatographic method was developed for the quantitative determination of bile acids [glycocholic acid (GCA), glycochenodeoxycholic acid (GCDA) and taurodeoxycholic acid (TDCA)) in in vitro bile acid-binding study of Welchol tablets. The method was developed using Phenomenex Kinetex C18 (50 × 2.10 mm, 1.7 µm) column with mobile phase containing a gradient mixture of solvent A consisting of 0.02 M tetrabutylammonium phosphate (pH 7.5) and solvent B consists acetonitrile. The eluted compounds were monitored at 210 nm and the runtime was within 2 min. The binding parameter constants of Colesevelam HCl tablets 625 mg were determined using the Langmuir approximation at pH 6.8 by UPLC. The method is selective and capable of detecting bile acids in the presence of placebo matrix. The method has been validated with a lower limit of quantitation of 0.01 mM for bile acids. A linear response function was established for the range of concentrations 0.01-30.0 mM (r > 0.99) for GCA, GCDA and TDCA. The intra- and interday precision values for bile acids met the acceptance as per Food and Drug Administrations guidelines. The developed method was applied to in vitro bile acid-binding studies of Colesevelam HCl tablets. PMID:24795077

  11. Determination of phosphorous in titanium bearing minerals by potentiometric titration using Pb-ion selective electrode.

    PubMed

    Ramadoss, K; Murty, D S; Mahanta, P L; Gomathy, B; Rangaswamy, R

    2000-01-24

    A method for phosphorous determination in titanium bearing minerals by potentiometric titration using a Pb-ion selective electrode has been developed. Sample decomposition is achieved by means of K(2)CO(3) fusion in a platinum crucible at 800 degrees C for 30 min in a muffle furnace, and subsequent leaching with water of the fused melt. The aqueous leachate is neutralised with HClO(4) and subsequent boiling. The obtained solution is used for titration with Pb(ClO(4))(2), and the Pb-ion selective electrode detects the end point. The lowest concentration determinable is 0.02% P(2)O(5) in a solid sample. The method was applied on in-house titanium bearing mineral samples and on IGS-31 ilmenite sample (British Geological Survey, UK). Synthetic samples were prepared and analysed, and phosphorous recovery is in the range 98-106%. The recovery and accuracy of the present method have been validated by spiking experiments and by comparing with the spectrophotometric values, respectively. The precision of the proposed method in terms of relative standard deviation is 2.0%. PMID:18967837

  12. An exact definition of total alkalinity and a procedure for the estimation of alkalinity and total inorganic carbon from titration data

    NASA Astrophysics Data System (ADS)

    Dickson, A. G.

    1981-06-01

    The total (or titration) alkalinity of a natural water sample can be regarded as a measure of the proton deficit of the solution relative to an arbitrarily defined zero level of protons. The problem of unambiguously incorporating any particular acid-base system into the definition of alkalinity is thus the one of deciding which form to specify as the zero level of protons, and it is proposed that it be defined so that acids with a dissociation constant K > 10-4·5 (at 25°C and zero ionic strength) are considered as proton donors, whilst those bases formed from weak acids with K ⪕ 10-4·5 are cosidered proton acceptors. A non-linear least squares procedure is suggested in order to estimate the total alkalinity (AT) and total inorganic carbon (CT) of a seawater sample from potentiometric titration data. The approach offers a significant conceptual improvement over the currently used refined Gran functions. In addition, an estimate of the statistical uncertainty of the estimated values of AT and CT is available. As it unnecessary to titrate beyond the alkalinity equivalence point, it may also be possible to speed up the titrations.

  13. Acid-base accounting assessment of mine wastes using the chromium reducible sulfur method.

    PubMed

    Schumann, Russell; Stewart, Warwick; Miller, Stuart; Kawashima, Nobuyuki; Li, Jun; Smart, Roger

    2012-05-01

    The acid base account (ABA), commonly used in assessment of mine waste materials, relies in part on calculation of potential acidity from total sulfur measurements. However, potential acidity is overestimated where organic sulfur, sulfate sulfur and some sulfide compounds make up a substantial portion of the sulfur content. The chromium reducible sulfur (CRS) method has been widely applied to assess reduced inorganic sulfur forms in sediments and acid sulfate soils, but not in ABA assessment of mine wastes. This paper reports the application of the CRS method to measuring forms of sulfur commonly found in mine waste materials. A number of individual sulfur containing minerals and real waste materials were analyzed using both CRS and total S and the potential acidity estimates were compared with actual acidity measured from net acid generation tests and column leach tests. The results of the CRS analysis made on individual minerals demonstrate good assessment of sulfur from a range of sulfides. No sulfur was measured using the CRS method in a number of sulfate salts, including jarosite and melanterite typically found in weathered waste rocks, or from dibenzothiophene characteristic of organic sulfur compounds common to coal wastes. Comparison of ABA values for a number of coal waste samples demonstrated much better agreement of acidity predicted from CRS analysis than total S analysis with actual acidity. It also resulted in reclassification of most samples tested from PAF to NAF. Similar comparisons on base metal sulfide wastes generally resulted in overestimation of the acid potential by total S and underestimation of the acid potential by CRS in comparison to acidity measured during NAG tests, but did not generally result in reclassification. In all the cases examined, the best estimate of potential acidity included acidity calculated from both CRS and jarositic S. PMID:22444067

  14. Method for high specific bioproductivity of {alpha},{omega}-alkanedicarboxylic acids

    SciTech Connect

    Mobley, D.P.; Shank, G.K.

    2000-05-23

    This invention provides a low-cost method of producing {alpha},{omega}-alkanedicarboxylic acids. Particular bioconversion conditions result in highly efficient conversion of fatty acid, fatty acid ester, or alkane substrates to diacids. Candida tropicalis AR40 or similar yeast strains are grown in a medium containing a carbon source and a nitrogen source at a temperature of 31 C to 38 C, while additional carbon source is continuously added, until maximum cell growth is attained. Within 0--3 hours of this point, substrate is added to the culture to initiate conversion. An {alpha},{omega}-alkanedicarboxylic acid made according to this method is also provided.

  15. Method for high specific bioproductivity of .alpha.,.omega.-alkanedicarboxylic acids

    DOEpatents

    Mobley, David Paul; Shank, Gary Keith

    2000-01-01

    This invention provides a low-cost method of producing .alpha.,.omega.-alkanedicarboxylic acids. Particular bioconversion conditions result in highly efficient conversion of fatty acid, fatty acid ester, or alkane substrates to diacids. Candida tropicalis AR40 or similar yeast strains are grown in a medium containing a carbon source and a nitrogen source at a temperature of 31.degree. C. to 38.degree. C., while additional carbon source is continuously added, until maximum cell growth is attained. Within 0-3 hours of this point, substrate is added to the culture to initiate conversion. An .alpha.,.omega.-alkanedicarboxylic acid made according to this method is also provided.

  16. Dissolution behavior of Caldag lateritic nickel ore subjected to a sequential organic acid leaching method

    NASA Astrophysics Data System (ADS)

    Kursunoglu, Sait; Kaya, Muammer

    2015-11-01

    The dissolution behavior of Caldag lateritic nickel ore subjected to a sequential organic acid leaching method was investigated. The effects of the type of organic acid, acid concentration, leaching time, and leaching temperature on the lateritic nickel ore were examined. Organic acids were used individually prior to sequential leaching. Citric acid was more effective than the other two acids for the selective leaching of nickel and cobalt. An increase in the citric acid concentration negligibly affected the dissolution of the metals, whereas temperature exhibited a strong beneficial effect. Oxalic acid was determined to be the most appropriate organic acid for the second leaching step. After 8 h (4 h + 4 h) of leaching with organic acids (0.5 M citric + 0.5 M oxalic) in sequence at 90°C, 89.63% Ni, 82.89% Co, and 69.63% Fe were leached from the lateritic nickel ore. A sequential citric + oxalic acid leaching method could represent a viable alternative for the dissolution of metals from lateritic nickel ore.

  17. Method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E. Philip; Kalina, Dale G.; Kaplan, Louis; Mason, George W.

    1985-01-01

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high level nuclear reprocessing waste solutions.

  18. A review on methods of recovery of acid(s) from spent pickle liquor of steel industry.

    PubMed

    Ghare, N Y; Wani, K S; Patil, V S

    2013-04-01

    Pickling is the process of removal of oxide layer and rust formed on metal surface. It also removes sand and corrosion products from the surface of metal. Acids such as sulfuric acid, hydrochloric acid are used for pickling. Hydrofluoric acid-Nitric acid mixture is used for stainless steel pickling. Pickling solutions are spent when acid concentration in pickling solutions decreases by 75-85%, which also has metal content up to 150-250 g/ dm3. Spent pickling liquor (SPL) should be dumped because the efficiency of pickling decreases with increasing content of dissolved metal in the bath. The SPL content depends on the plant of origin and the pickling method applied there. SPL from steel pickling in hot-dip galvanizing plants contains zinc(II), iron, traces of lead, chromium. and other heavy metals (max. 500 mg/dm3) and hydrochloric acid. Zinc(II) passes tothe spent solution after dissolution of this metal from zinc(II)-covered racks, chains and baskets used for transportation of galvanized elements. Unevenly covered zinc layers are usually removed in another pickling bath. Due to this, zinc(II) concentration increases even up to 110 g/dm3, while iron content may reach or exceed even 80 g/dm3 in the same solution. This review presents an overview on different aspects of generation and treatment of SPL with recourse to recovery of acid for recycling. Different processes are described in this review and higher weightage is given to membrane processes. PMID:25464702

  19. A review on methods of recovery of acid(s) from spent pickle liquor of steel industry.

    PubMed

    Ghare, N Y; Wani, K S; Patil, V S

    2013-04-01

    Pickling is the process of removal of oxide layer and rust formed on metal surface. It also removes sand and corrosion products from the surface of metal. Acids such as sulfuric acid, hydrochloric acid are used for pickling. Hydrofluoric acid-Nitric acid mixture is used for stainless steel pickling. Pickling solutions are spent when acid concentration in pickling solutions decreases by 75-85%, which also has metal content up to 150-250 g/ dm3. Spent pickling liquor (SPL) should be dumped because the efficiency of pickling decreases with increasing content of dissolved metal in the bath. The SPL content depends on the plant of origin and the pickling method applied there. SPL from steel pickling in hot-dip galvanizing plants contains zinc(II), iron, traces of lead, chromium. and other heavy metals (max. 500 mg/dm3) and hydrochloric acid. Zinc(II) passes tothe spent solution after dissolution of this metal from zinc(II)-covered racks, chains and baskets used for transportation of galvanized elements. Unevenly covered zinc layers are usually removed in another pickling bath. Due to this, zinc(II) concentration increases even up to 110 g/dm3, while iron content may reach or exceed even 80 g/dm3 in the same solution. This review presents an overview on different aspects of generation and treatment of SPL with recourse to recovery of acid for recycling. Different processes are described in this review and higher weightage is given to membrane processes. PMID:25508333

  20. A Simple Spectrophotometric Method for the Determination of Thiobarbituric Acid Reactive Substances in Fried Fast Foods.

    PubMed

    Zeb, Alam; Ullah, Fareed

    2016-01-01

    A simple and highly sensitive spectrophotometric method was developed for the determination of thiobarbituric acid reactive substances (TBARS) as a marker for lipid peroxidation in fried fast foods. The method uses the reaction of malondialdehyde (MDA) and TBA in the glacial acetic acid medium. The method was precise, sensitive, and highly reproducible for quantitative determination of TBARS. The precision of extractions and analytical procedure was very high as compared to the reported methods. The method was used to determine the TBARS contents in the fried fast foods such as Shami kebab, samosa, fried bread, and potato chips. Shami kebab, samosa, and potato chips have higher amount of TBARS in glacial acetic acid-water extraction system than their corresponding pure glacial acetic acid and vice versa in fried bread samples. The method can successfully be used for the determination of TBARS in other food matrices, especially in quality control of food industries. PMID:27123360

  1. A Simple Spectrophotometric Method for the Determination of Thiobarbituric Acid Reactive Substances in Fried Fast Foods

    PubMed Central

    Zeb, Alam; Ullah, Fareed

    2016-01-01

    A simple and highly sensitive spectrophotometric method was developed for the determination of thiobarbituric acid reactive substances (TBARS) as a marker for lipid peroxidation in fried fast foods. The method uses the reaction of malondialdehyde (MDA) and TBA in the glacial acetic acid medium. The method was precise, sensitive, and highly reproducible for quantitative determination of TBARS. The precision of extractions and analytical procedure was very high as compared to the reported methods. The method was used to determine the TBARS contents in the fried fast foods such as Shami kebab, samosa, fried bread, and potato chips. Shami kebab, samosa, and potato chips have higher amount of TBARS in glacial acetic acid-water extraction system than their corresponding pure glacial acetic acid and vice versa in fried bread samples. The method can successfully be used for the determination of TBARS in other food matrices, especially in quality control of food industries. PMID:27123360

  2. The effect of copper on iron reduction and its application to the determination of total iron content in iron and copper ores by potassium dichromate titration.

    PubMed

    Hu, Hanjun; Tang, Yang; Ying, Haisong; Wang, Minghai; Wan, Pingyu; Jin Yang, X

    2014-07-01

    The International Standard Organization (ISO) specifies two titrimetric methods for the determination of total iron content in iron ores using potassium dichromate as titrant after reduction of the iron(III) by tin(II) chloride and/or titanium(III) chloride. These two ISO methods (ISO2597-1 and ISO2597-2) require nearly boiling-point temperature for iron(III) reduction and suffer from copper interference and/or mercury pollution. In this study, potassium borohydride was used for reduction of iron(III) catalyzed by copper ions at ambient temperatures. In the absence of copper, iron(III) reduction by potassium borohydride was sluggish while a trace amount of copper significantly accelerated the reduction and reduced potassium borohydride consumption. The catalytic mechanism of iron(III) reduction in sulfuric acid and hydrochloric acid was investigated. Potassium borohydride in sodium hydroxide solution was stable without a significant degradation within 24h at ambient conditions and the use of potassium borohydride prepared in sodium hydroxide solution was safe and convenient in routine applications. The applicability of potassium borohydride reduction for the determination of total iron content by potassium dichromate titration was demonstrated by comparing with the ISO standard method using iron and copper ore reference materials and iron ore samples. PMID:24840467

  3. Hydrochloric acid method of beneficiating magnesite using a pilot plant

    SciTech Connect

    Sertin, V.A.; Galkin, Y.M.; Gemusova, I.B.; Glezer, E.B.; Khaltyurin, V.A.; Kislitsyn, V.I.; Rodde, T.V.; Simonov, K.V.; Vetlugina, N.A.; Yurlova, L.N.; Zakutinskii, V.L.

    1985-07-01

    One feature of the HCl treatment of magnesite is the possibility of using the main mass of HCl in a closed cycle. Regeneration of the HCl takes place during the thermal hydrolysis of the purified solution of magnesium chloride. In accordance with the plan drawn up by the Eastern Institute of Refractories and the Ukranian Institute of Chemistry, a pilot plant has been built at the Magnesite Combine; this has been mastered and is used for the hydrochloric acid treatment of magnesite; the annual productivity of the equipment is 400 tons. Some features of the process of dissolution of natural and caustic magnesite in HCL and the sintering of the beneficiated product have been considered elsewhere. This paper pays particular attention to the apparatus-process character and considers in more detail the hydrolysis of magnesium chloride.

  4. Hydrofluoric acid-resistant composite window and method for its fabrication

    DOEpatents

    Ostenak, C.A.; Mackay, H.A.

    1985-07-18

    A hydrofluoric acid-resistant composite window and method for its fabrication are disclosed. The composite window comprises a window having first and second sides. The first side is oriented towards an environment containing hydrofluoric acid. An adhesive is applied to the first side. A layer of transparent hydrofluoric acid-resistant material, such as Mylar, is applied to the adhesive and completely covers the first side. The adhesive is then cured.

  5. Hydrofluoric acid-resistant composite window and method for its fabrication

    DOEpatents

    Ostenak, Carl A.; Mackay, Harold A.

    1987-01-01

    A hydrofluoric acid-resistant composite window and method for its fabrication are disclosed. The composite window comprises a window having first and second sides. The first side is oriented towards an environment containing hydrofluoric acid. An adhesive is applied to the first side. A layer of transparent hydrofluoric acid-resistant material, such as Mylar, is applied to the adhesive and completely covers the first side. The adhesive is then cured.

  6. The Ca(2+)-EDTA chelation as standard reaction to validate Isothermal Titration Calorimeter measurements (ITC).

    PubMed

    Ràfols, Clara; Bosch, Elisabeth; Barbas, Rafael; Prohens, Rafel

    2016-07-01

    A study about the suitability of the chelation reaction of Ca(2+)with ethylenediaminetetraacetic acid (EDTA) as a validation standard for Isothermal Titration Calorimeter measurements has been performed exploring the common experimental variables (buffer, pH, ionic strength and temperature). Results obtained in a variety of experimental conditions have been amended according to the side reactions involved in the main process and to the experimental ionic strength and, finally, validated by contrast with the potentiometric reference values. It is demonstrated that the chelation reaction performed in acetate buffer 0.1M and 25°C shows accurate and precise results and it is robust enough to be adopted as a standard calibration process. PMID:27154686

  7. Methods for immobilizing nucleic acids on a gel substrate

    DOEpatents

    Mirzabekov, Andrei Darievich; Proudnikov, Dimitri Y.; Timofeev, Edward N.; Kochetkova, Svetlana V.; Florentiev, Vladimir L.; Shick, Valentine V.

    1999-01-01

    A method for labeling oligonucleotide molecules, and for immobilizing oligonucleotide and DNA molecules is provided comprising modifying the molecules to create a chemically active group, and contacting activated fluorescent dyes to the region. A method for preparing an immobilization substrate is also provided comprising modifying a gel to contain desired functional groups which covalently interact with certain moieties of the oligonucleotide molecules. A method for immobilizing biomolecules and other molecules within a gel by copolymerization of allyl-substituted oligonucleotides, DNA and proteins with acrylamide is also provided.

  8. Collection and analysis of organic acids in exhaust gas. Comparison of different methods

    NASA Astrophysics Data System (ADS)

    Zervas, E.; Montagne, X.; Lahaye, J.

    This paper reports the development of a specific method to identify organic acids in exhaust gases. The organic acids are collected in two impingers containing liquids (pure water or Na 2CO 3 1% aqueous solution) and four cartridges containing solids (silica, fluorisil, alumina B and alumina N). Once collected, the acids are eluted of the solids by a hot water stream. These traps performances, in terms of organic acids collection and elution efficiency, are evaluated and compared. Two sources are used to produce the gas flow containing organic acids: one generates a flow whose concentration is known and stable, the other produces organic acids among other combustion products. For eluted solutions analysis, two methods are used: isocratic ionic chromatography/conductivity detection and GC/FID. Their efficiency in separating 10 aliphatic acids are compared. Their characteristics such as detection limits, detection linearity, repeatability and possible interferences with other components found in exhaust gases are determined. The stability of the organic acids solutions is also studied. Lastly, the use of these methods is illustrated by the analysis of the gas-phase organic acids exhausted by a spark ignition and by a diesel engine.

  9. Thermodynamic characterization of drug binding to human serum albumin by isothermal titration microcalorimetry.

    PubMed

    Aki, H; Yamamoto, M

    1994-12-01

    Binding sites on human serum albumin (HSA) for anionic drugs and fatty acids have been thermodynamically characterized by microcalorimetry. The binding and the thermodynamic parameters were directly computed from the calorimetric titration data at 37 degrees C in a phosphate buffer (pH 7.4) using one- and two-class binding models. From compensation analyses plotting the molar enthalpy change (delta Hm,i) versus those of the molar free energy (delta Gm,i) and molar entropy (delta Sm,i) for each class of binding sites, HSA binding sites were classified into groups S1, S2, and S3. Group S1 included high-affinity binding sites for site II-bound drugs, such as ibuprofen, flufenamic acid, and ethacrynic acid, and short- or medium-length alkyl-chain fatty acids; group S2 included low-affinity binding sites of site II-bound drugs and long-length alkyl-chain fatty acids; and group S3 contained the high-affinity binding sites for site I-bound drugs, such as phenylbutazone, oxphenbutazone, and warfarin, and long-length alkyl-chain fatty acids. High- and low-affinity bindings sites for salicylic acid and acetylaslicylic acid agreed with the regions of groups S3 and S2, respectively. Groups S1 and S2 were characterized by large negative values of delta Hm,i and delta Sm,i, reflecting van der Waals interaction and hydrogen-bonding formation in low dielectric media, and the main force to stabilize the binding complex in group S3 was a hydrophobic interaction, characterized by a small negative delta Hm,i and minor or positive values of delta Sm,i (entropy-driven). PMID:7891299

  10. A new method for the removal of toxic metal ions from acid-sensitive biomaterial

    SciTech Connect

    Seki, Hideshi; Suzuki, Akira

    1997-06-01

    A new method (competitive adsorption method) for the removal of toxic heavy metals from acid-sensitive biomaterials was proposed and it was applied to the removal of cadmium from the midgut gland (MG) of scallop, Patinopecten yessoensis. Insolubilized humic acid, which has been developed in the laboratory, was used as a competitive adsorbent. A metal-complexation model was used to determine the adsorption characteristics of cadmium onto MG. Furthermore, the model was applied to the competitive adsorption system. The results showed that the competitive adsorption method enabled the simultaneous removal of toxic cadmium from both liquid and MG phase under mild acidic condition (pH 5).

  11. Evaluation of two enzymatic methods of determining unsulphated serum bile acids.

    PubMed

    Hedenborg, G; Norman, A; Samuelson, K

    1984-12-01

    Two enzymatic methods of determining unsulphated 3 alpha-hydroxylated and 7 alpha-hydroxylated bile acids, respectively, were evaluated. Both methods are based on a coupled enzyme reaction involving a coloured redox indicator and absorbance measurement as the final step. Recovery and specificity were tested on human serum pools containing different bile acids added in various amounts, and by comparison of the results with those obtained by gas-liquid chromatography after group separation of bile acids from patient sera. Results from the two enzymatic methods were also compared with those determined with radioimmunoassay on a large number of patient sera. The results indicate that the enzymatic methods are useful for serum bile acid screening but more sensitive methods are necessary for investigations within the normal range. PMID:6597529

  12. Constant-pH MD Simulations of an Oleic Acid Bilayer.

    PubMed

    Vila-Viçosa, Diogo; Teixeira, Vitor H; Baptista, António M; Machuqueiro, Miguel

    2015-05-12

    Oleic acid is a simple molecule with an aliphatic chain and a carboxylic group whose ionization and, consequently, intermolecular interactions are strongly dependent on the solution pH. The titration curve of these molecules was already obtained using different experimental methods, which have shown the lipid bilayer assemblies to be stable between pH 7.0 and 9.0. In this work, we take advantage of our recent implementations of periodic boundary conditions in Poisson-Boltzmann calculations and ionic strength treatment in simulations of charged lipid bilayers, and we studied the ionization dependent behavior of an oleic acid bilayer using a new extension of the stochastic titration constant-pH MD method. With this new approach, we obtained titration curves that are in good agreement with the experimental data. Also, we were able to estimate the slope of the titration curve from charge fluctuations, which is an important test of thermodynamic consistency for the sampling in a constant-pH MD method. The simulations were performed for ionizations up to 50%, because an experimentally observed macroscopic transition to micelles occurs above this value. As previously seen for a binary mixture of a zwitterionic and an anionic lipid, we were able to reproduce experimental results with simulation boxes usually far from neutrality. This observation further supports the idea that a charged membrane strongly influences the ion distribution in its vicinity and that neutrality is achieved significantly far from the bilayer surface. The good results obtained with this extension of the stochastic titration constant-pH MD method strongly supports its usefulness to sample the coupling between configuration and protonation in these types of biophysical systems. This method stands now as a powerful tool to study more realistic lipid bilayers where pH can influence both the lipids and the solutes interacting with them. PMID:26574431

  13. Polyelectrolyte assisted charge titration spectrometry: Applications to latex and oxide nanoparticles.

    PubMed

    Mousseau, F; Vitorazi, L; Herrmann, L; Mornet, S; Berret, J-F

    2016-08-01

    The electrostatic charge density of particles is of paramount importance for the control of the dispersion stability. Conventional methods use potentiometric, conductometric or turbidity titration but require large amount of samples. Here we report a simple and cost-effective method called polyelectrolyte assisted charge titration spectrometry or PACTS. The technique takes advantage of the propensity of oppositely charged polymers and particles to assemble upon mixing, leading to aggregation or phase separation. The mixed dispersions exhibit a maximum in light scattering as a function of the volumetric ratio X, and the peak position XMax is linked to the particle charge density according to σ∼D0XMax where D0 is the particle diameter. The PACTS is successfully applied to organic latex, aluminum and silicon oxide particles of positive or negative charge using poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). The protocol is also optimized with respect to important parameters such as pH and concentration, and to the polyelectrolyte molecular weight. The advantages of the PACTS technique are that it requires minute amounts of sample and that it is suitable to a broad variety of charged nano-objects. PMID:27153216

  14. Single-antibody in situ enzyme immunoassay for infectivity titration of hepatitis A virus.

    PubMed

    Borovec, S; Uren, E

    1997-10-01

    Hepatitis A virus (HAV) establishes a persistent infection in cultured cells, with minimal effect on host cell metabolism. As a result, the virus produces very little, if any, cytopathic effect (CPE), even with cell culture-adapted strains. This feature precludes the use of a plaque or standard endpoint assay (using CPE as an indicator of infection) for the titration of infectious virus. The radioimmunofocus assay (RIFA) is the standard method for HAV titration, though this method is labour intensive and requires the use of radioisotopes. To this end, a single-antibody in situ enzyme immunoassay (EIA) has been developed, using binding of a perioxidase-labelled monoclonal antibody to fixed cell monolayers as an indicator of infection. This novel assay is highly reproducible, can be read by eye, and is suitable for high throughput situations. Furthermore, the assay has been validated against the RIFA making it suitable for use in studies validating the safety of therapeutic biologicals for human use. PMID:9395142

  15. Thermal and acid tolerant beta xylosidases, arabinofuranosidases, genes encoding, related organisms, and methods

    DOEpatents

    Thompson, David N; Thompson, Vicki S; Schaller, Kastli D; Apel, William A; Reed, David W; Lacey, Jeffrey A

    2013-04-30

    Isolated and/or purified polypeptides and nucleic acid sequences encoding polypeptides from Alicyclobacillus acidocaldarius and variations thereof are provided. Further provided are methods of at least partially degrading xylotriose, xylobiose, and/or arabinofuranose-substituted xylan using isolated and/or purified polypeptides and nucleic acid sequences encoding polypeptides from Alicyclobacillus acidocaldarius and variations thereof.

  16. Thermal and acid tolerant beta-xylosidases, genes encoding, related organisms, and methods

    DOEpatents

    Thompson, David N.; Thompson, Vicki S.; Schaller, Kastli D.; Apel, William A.; Lacey, Jeffrey A.; Reed, David W.

    2011-04-12

    Isolated and/or purified polypeptides and nucleic acid sequences encoding polypeptides from Alicyclobacillus acidocaldarius and variations thereof are provided. Further provided are methods of at least partially degrading xylotriose and/or xylobiose using isolated and/or purified polypeptides and nucleic acid sequences encoding polypeptides from Alicyclobacillus acidocaldarius and variations thereof.

  17. USEPA METHOD STUDY 37 - SW-846 METHOD 3050, ACID DIGESTION OF SEDIMENTS, SLUDGES AND SOILS BY AA-DIRECT ASPIRATION

    EPA Science Inventory

    An interlaboratory collaborative study was conducted to determine the precision and accuracy of Method 3050 for the analysis of 23 elements in sediments, sludqes and soils. Method 3050 is entitled, "Acid Digestion of Sediments, Sludges and Soils." It includes instructions for qua...

  18. Evaluation of a rapid, portable and easy-to-use device to measure acidity in citrus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determination of titratable acidity in citrus is a time-consuming and sometimes tedious process, but is commonly practiced in the measurement of citrus maturity. Recently, a new acidity meter has come onto the market that measures titratable acidity using conductivity. This instrument is easy-to-u...

  19. Using Conductivity Measurements to Determine the Identities and Concentrations of Unknown Acids: An Inquiry Laboratory Experiment

    ERIC Educational Resources Information Center

    Smith, K. Christopher; Garza, Ariana

    2015-01-01

    This paper describes a student designed experiment using titrations involving conductivity measurements to identify unknown acids as being either HCl or H[subscript 2]SO[subscript 4], and to determine the concentrations of the acids, thereby improving the utility of standard acid-base titrations. Using an inquiry context, students gain experience…

  20. Method for replicating an array of nucleic acid probes

    DOEpatents

    Cantor, C.R.; Przetakiewicz, M.; Smith, C.L.; Sano, T.

    1998-08-18

    The invention relates to the replication of probe arrays and methods for replicating arrays of probes which are useful for the large scale manufacture of diagnostic aids used to screen biological samples for specific target sequences. Arrays created using PCR technology may comprise probes with 5{prime}- and/or 3{prime}-overhangs. 16 figs.

  1. Method for replicating an array of nucleic acid probes

    DOEpatents

    Cantor, Charles R.; Przetakiewicz, Marek; Smith, Cassandra L.; Sano, Takeshi

    1998-01-01

    The invention relates to the replication of probe arrays and methods for replicating arrays of probes which are useful for the large scale manufacture of diagnostic aids used to screen biological samples for specific target sequences. Arrays created using PCR technology may comprise probes with 5'- and/or 3'-overhangs.

  2. Stress degradation studies and stability-indicating TLC-densitometric method of glycyrrhetic acid

    PubMed Central

    2013-01-01

    Background Glycyrrhetic acid, a pentacyclic triterpenoid, possesses a broad range of pharmacological activities and serves as template to synthesize many bioactive drugs. This paper describes a simple, accurate, and sensitive stability-indicating TLC densitometric method for the determination of glycyrrhetic acid and its degradation product as per the ICH guidelines. Results Separation was carried out on TLC aluminium sheet pre-coated with silica gel 60F254 using chloroform, methanol and formic acid (9:0.9:0.1, v/v). Compact spot for glycyrrhetic acid was found at Rf value of 0.42 ± 0.03. Densitometric analysis was carried out in the absorbance mode at λmax 254 nm. Glycyrrhetic acid was found to be stable to the exposure of base, neutral, oxidation, dry heating treatment and wet heating treatment, but showed degradation under acidic and photochemical conditions. Moreover, fragmentation pattern of glycyrrhetic acid was developed by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. A photo-degraded product was characterized through comparison of mass spectrometric studies with glycyrrhetic acid. Conclusion The developed stability-indicating TLC-densitometric method can be applied for routine analysis of glycyrrhetic acid in the presence of its degradation products. PMID:23327365

  3. Preservation Methods for Retaining n-3 Polyunsaturated Fatty Acids in Alaska Coho Salmon (Oncorhynchus kisutch) Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Coho salmon (Oncorhynchus kisutch) fillets were processed using five different methods (smoking, canning, freezing, acidifying, and salting) to evaluate the effect of preservation choice on the quality of polyunsaturated fatty acids (PUFA). Salmon preserved by smoking, canning, or freezing retained ...

  4. Improved Butanol-Methanol (BUME) Method by Replacing Acetic Acid for Lipid Extraction of Biological Samples.

    PubMed

    Cruz, Mutya; Wang, Miao; Frisch-Daiello, Jessica; Han, Xianlin

    2016-07-01

    Extraction of lipids from biological samples is a critical step in lipidomics, especially for shotgun lipidomics where lipid extracts are directly infused into a mass spectrometer. The butanol-methanol (BUME) extraction method was originally developed to extract lipids from plasma samples with 1 % acetic acid. Considering some lipids are sensitive to acidic environments, we modified this protocol by replacing acetic acid with lithium chloride solution and extended the modified extraction to tissue samples. Although no significant reduction of plasmalogen levels in the acidic BUME extracts of rat heart samples was found, the modified method was established to extract various tissue samples, including rat liver, heart, and plasma. Essentially identical profiles of the majority of lipid classes were obtained from the extracts of the modified BUME and traditional Bligh-Dyer methods. However, it was found that neither the original, nor the modified BUME method was suitable for 4-hydroxyalkenal species measurement in biological samples. PMID:27245345

  5. Analysis of acid rain patterns in northeastern China using a decision tree method

    NASA Astrophysics Data System (ADS)

    Zhang, Xiuying; Jiang, Hong; Jin, Jiaxin; Xu, Xiaohua; Zhang, Qingxin

    2012-01-01

    Acid rain is a major regional-scale environmental problem in China. To control acid rain pollution and to protect the ecological environment, it is urgent to document acid rain patterns in various regions of China. Taking Liaoning Province as the study area, the present work focused on the spatial and temporal variations of acid rains in northeastern China. It presents a means for predicting the occurrence of acid rain using geographic position, terrain characteristics, routinely monitored meteorological factors and column concentrations of atmospheric SO 2 and NO 2. The analysis applies a decision tree approach to the foregoing observation data. Results showed that: (1) acid rain occurred at 17 stations among the 81 monitoring stations in Liaoning Province, with the frequency of acid rain from 0 to 84.38%; (2) summer had the most acid rain occurrences followed by spring and autumn, and the winter had the least; (3) the total accuracy for the simulation of precipitation pH (pH ≤ 4.5, 4.5 < pH ≤ 5.6, and pH > 5.6) was 98.04% using the decision tree method known as C5. The simulation results also indicated that the distance to coastline, elevation, wind direction, wind speed, rainfall amount, atmospheric pressure, and the precursors of acid rain all have a strong influence on the occurrence of acid rains in northeastern China.

  6. Fused liposome and acid induced method for liposome fusion

    SciTech Connect

    Huang, L.; Connor, J.

    1988-12-06

    This patent describes a method of fusing liposomes. It comprises: preparing a suspension of liposomes containing at least one lipid which has a tendency to form the inverted hexagonal phase and at least 20 mol percent of palmitoylhomocysteine; and in the absence of externally added divalent cations, proteins or other macromolecules, acidifying the liposome suspension to reduce the pH of the liposomes to below pH 7, such that at least about 20% of the liposomes fuse to one another.

  7. Closed cycle ion exchange method for regenerating acids, bases and salts

    DOEpatents

    Dreyfuss, Robert M.

    1976-01-01

    A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof are ions also produced as a by-product in the closed reaction cycle, and then regenerating the spent ion exchanger by contact with the by-product counter ions. The method is particularly applicable to closed cycle processes for the thermochemical production of hydrogen.

  8. Development of a rapid and confirmatory method to identify ganoderic acids in ganoderma mushrooms.

    PubMed

    Qi, Ying; Zhao, Lingling; Sun, Hao H

    2012-01-01

    To examine the composition of lanostanoids in Ganoderma lucidum, we have developed a liquid chromatography-mass spectrometry (LC-MS) method by using the ganoderic acids isolated in our laboratory as reference standards. The identity of 14 peaks in the high performance liquid chromatogram (HPLC) of G. lucidum has been confirmed. By using the HPLC retention times of these ganoderic acids and their mass fragmentation patterns established in this paper, one can use LC-MS to analyze G. lucidum without requiring the reference standards of these 14 ganoderic acids. Subsequently, only the HPLC-UV method would be needed to analyze routine samples of G. lucidum. PMID:22586399

  9. Surface composition determination of Pt--Sn alloys by chemical titration with carbon monoxide

    SciTech Connect

    Haner, A.H.; Ross, P.N. ); Bardi, U.; Atrei, A. )

    1992-07-01

    The use of chemical titration with carbon monoxide to determine the surface composition of Pt--Sn alloys was studied using Pt{sub 3}Sn single crystals of known surface composition. The surface composition of the (111) and (100) faces were determined independently by the combination of low-energy electron diffraction (LEED) crystallography and low-energy ion scattering (LEIS). CO was adsorbed on these surfaces to saturation at 250 K and thermally desorbed into a mass spectrometer. The area under the thermal desorption spectroscopy curve for the alloy surface was compared to the area under the curve for the pure Pt surface of the same orientation. The ratios were 0.5{plus minus}0.05 for Pt{sub 3}Sn(100) and 0.7{plus minus}0.05 for Pt{sub 3}Sn(111), in excellent agreement with the 50% Pt and 75% Pt surface compositions derived from LEED and LEIS. The success of the titration method in this case appears to be due to (a) selective adsorption of CO on Pt atoms and (b) the relatively weak effect of the Pt--Sn intermetallic bond on the Pt--CO bonding.

  10. Sleep Apnea in Patients with Acromegaly. Frequency, Characterization and Positive Pressure Titration

    PubMed Central

    Hernández-Gordillo, Daniel; Ortega-Gómez, María del Rocío; Galicia-Polo, Lourdes; Castorena-Maldonado, Armando; Vergara-López, Alma; Guillén-González, Miguel Ángel; Torre-Bouscoulet, Luis

    2012-01-01

    Objectives: to describe the frequency of sleep apnea in patients with acromegaly;to identify the proportion of candidates for treatment with positive airway pressure;to report our experience with the positive pressure titration process in acromegaly patients. Methods: A cross-sectional study that included the acromegaly cohort at the Centro Medico Nacional “20 de Noviembre” in Mexico City (n=44). A standard polysomnography (PSG) was carried out for each patient. A second PSG was done for purposes of CPAP titration. Results: A total of 35 patients were studied (80% of the cohort, 20 [57%] women). Polysomnography results showed that 34 subjects (97%, 95%CI 91-100%) had apnea hypopnea indexes (AHI) ≥ 5. No patient had central apnea. We identified 19 subjects with AHI ≥5 and Epworth ≥10, for a frequency of obstructive sleep apnea syndrome of 54% (95%CI 36-71%). A total of 31 patients (88%; 95%CI 77-99%) were deemed to be candidates for positive pressure treatment, but only 8 of them accepted CPAP. They required pressures that ranged from 10 to 18 cmH2O. Conclusions: Our results confirm a high prevalence of sleep apnea in patients with acromegaly, and provide evidence that the majority of those patients are candidates for treatment with positive pressure. Contrary to what has been reported, we identified no patients with central apnea. PMID:22754597

  11. A microfabrication-based approach to quantitative isothermal titration calorimetry.

    PubMed

    Wang, Bin; Jia, Yuan; Lin, Qiao

    2016-04-15

    Isothermal titration calorimetry (ITC) directly measures heat evolved in a chemical reaction to determine equilibrium binding properties of biomolecular systems. Conventional ITC instruments are expensive, use complicated design and construction, and require long analysis times. Microfabricated calorimetric devices are promising, although they have yet to allow accurate, quantitative ITC measurements of biochemical reactions. This paper presents a microfabrication-based approach to integrated, quantitative ITC characterization of biomolecular interactions. The approach integrates microfabricated differential calorimetric sensors with microfluidic titration. Biomolecules and reagents are introduced at each of a series of molar ratios, mixed, and allowed to react. The reaction thermal power is differentially measured, and used to determine the thermodynamic profile of the biomolecular interactions. Implemented in a microdevice featuring thermally isolated, well-defined reaction volumes with minimized fluid evaporation as well as highly sensitive thermoelectric sensing, the approach enables accurate and quantitative ITC measurements of protein-ligand interactions under different isothermal conditions. Using the approach, we demonstrate ITC characterization of the binding of 18-Crown-6 with barium chloride, and the binding of ribonuclease A with cytidine 2'-monophosphate within reaction volumes of approximately 0.7 µL and at concentrations down to 2mM. For each binding system, the ITC measurements were completed with considerably reduced analysis times and material consumption, and yielded a complete thermodynamic profile of the molecular interaction in agreement with published data. This demonstrates the potential usefulness of our approach for biomolecular characterization in biomedical applications. PMID:26655185

  12. Automatic set-point titration for monitoring nitrification in SBRs.

    PubMed

    Fiocchi, N; Ficara, E; Bonelli, S; Canziani, R; Ciappelloni, F; Mariani, S; Pirani, M; Ratini, P; Mazouni, D; Harmand, J

    2008-01-01

    Nitrification is usually the bottleneck of biological nitrogen removal processes. In SBRs systems, it is not often enough to monitor dissolved oxygen, pH and ORP to spot problems which may occur in nitrification processes. Therefore, automated supervision systems should be designed to include the possibility of monitoring the activity of nitrifying populations. Though the applicability of set-point titration for monitoring biological processes has been widely demonstrated in the literature, the possibility of an automated procedure is still at its early stage of industrial development. In this work, the use of an at-line automated titrator named TITAAN (TITrimetric Automated ANalyser) is presented. The completely automated sensor enables us to track nitrification rate trend with time in an SBR, detecting the causes leading to slower specific nitrification rates. It was also possible to perform early detection of toxic compounds in the influent by assessing their effect on the nitrifying biomass. Nitrifications rates were determined with average errors+/-10% (on 26 tests), never exceeding 20% as compared with UV-spectrophotometric determinations. PMID:18701782

  13. Selection of direct transesterification as the preferred method for assay of fatty acid content of microalgae.

    PubMed

    Griffiths, M J; van Hille, R P; Harrison, S T L

    2010-11-01

    Assays for total lipid content in microalgae are usually based on the Folch or the Bligh and Dyer methods of solvent extraction followed by quantification either gravimetrically or by chromatography. Direct transesterification (DT) is a method of converting saponifiable lipids in situ directly to fatty acid methyl esters which can be quantified by gas chromatography (GC). This eliminates the extraction step and results in a rapid, one-step procedure applicable to small samples. This study compared the effectiveness of DT in quantifying the total fatty acid content in three species of microalgae to extraction using the Folch, the Bligh and Dyer and the Smedes and Askland methods, followed by transesterification and GC. The use of two catalysts in sequence, as well as the effect of reaction water content on the efficiency of DT were investigated. The Folch method was the most effective of the extraction methods tested, but comparison with DT illustrated that all extraction methods were incomplete. Higher levels of fatty acid in the cells were obtained with DT in comparison with the extraction-transesterification methods. A combination of acidic and basic transesterification catalysts was more effective than each individually when the sample contained water. The two-catalyst reaction was insensitive to water up to 10% of total reaction volume. DT proved a convenient and more accurate method than the extraction techniques for quantifying total fatty acid content in microalgae. PMID:20820931

  14. Standard addition method for free acid determination in solutions with hydrolyzable ions

    SciTech Connect

    Baumann, E.W.

    1981-01-01

    The free acid content of solutions containing hydrolyzable ions has been determined potentiometrically by a standard addition method. Two increments of acid are added to the sample in a 1M potassium thiocyanate solution. The sample concentration is calculated by solution of three simultaneous Nernst equations. The method has been demonstrated for solutions containing Al/sup 3 +/, Cr/sup 3 +/, Fe/sup 3 +/, Ni/sup 2 +/, Th/sup 4 +/, or UO/sub 2//sup 2 +/ with a metal-to-acid ratio of < 2.5. The method is suitable for determination of 10 ..mu..moles acid in 10 mL total volume. The accuracy is verifiable by reasonable agreement of the Nerst slopes found in the presence and absence of hydrolyzable ions. The relative standard deviation is < 2.5 percent.

  15. Enzyme catalysis-electrophoresis titration for multiplex enzymatic assay via moving reaction boundary chip.

    PubMed

    Zhong, Ran; Xie, Haiyang; Kong, Fanzhi; Zhang, Qiang; Jahan, Sharmin; Xiao, Hua; Fan, Liuyin; Cao, Chengxi

    2016-09-21

    In this work, we developed the concept of enzyme catalysis-electrophoresis titration (EC-ET) under ideal conditions, the theory of EC-ET for multiplex enzymatic assay (MEA), and a related method based on a moving reaction boundary (MRB) chip with a collateral channel and cell phone imaging. As a proof of principle, the model enzymes horseradish peroxidase (HRP), laccase and myeloperoxidase (MPO) were chosen for the tests of the EC-ET model. The experiments revealed that the EC-ET model could be achieved via coupling EC with ET within a MRB chip; particularly the MEA analyses of catalysis rate, maximum rate, activity, Km and Kcat could be conducted via a single run of the EC-ET chip, systemically demonstrating the validity of the EC-ET theory. Moreover, the developed method had these merits: (i) two orders of magnitude higher sensitivity than a fluorescence microplate reader, (ii) simplicity and low cost, and (iii) fairly rapid (30 min incubation, 20 s imaging) analysis, fair stability (<5.0% RSD) and accuracy, thus validating the EC-ET method. Finally, the developed EC-ET method was used for the clinical assay of MPO activity in blood samples; the values of MPO activity detected via the EC-ET chip were in agreement with those obtained by a traditional fluorescence microplate reader, indicating the applicability of the EC-ET method. The work opens a window for the development of enzymatic research, enzyme assay, immunoassay, and point-of-care testing as well as titration, one of the oldest methods of analysis, based on a simple chip. PMID:27464600

  16. Growth behavior of gold nanoparticles synthesized in unsaturated fatty acids by vacuum evaporation methods.

    PubMed

    Fujita, Akito; Matsumoto, Yusuke; Takeuchi, Mitsuaki; Ryuto, Hiromichi; Takaoka, Gikan H

    2016-02-21

    Physical vapor evaporation of metals on low vapor pressure liquids is a simple and clean method to synthesize nanoparticles and thin films, though only little work has been conducted so far. Here, gold nanoparticles were synthesized by vacuum evaporation (VE) methods in ricinoleic acid and oleic acid, two typical unsaturated fatty acids (UFAs). The two solvents formed black aggregates after deposition and then shrunk and finally disappeared with the progress of time. By transmission electron microscopy (TEM) images, nanoparticles in ricinoleic acids formed aggregates and then dispersed by time, while in oleic acid big aggregates were not observed in all timescales. From TEM images and small angle X-ray scattering (SAXS) measurements, the mean size of the nanoparticles was about 4 nm in both ricinoleic and oleic acids. UV-Vis spectra were also taken as a function of time and the results were consistent with the growth behavior presumed by TEM images. Air exposure had an influence on the behavior of the sample triggering the nanoparticle formation in both solvents. From control experiments, we discovered that oxygen gas triggered the phenomenon and nanoparticles function as a catalyst for the oxidation of the UFAs. It stimulates the phenomenon and in ricinoleic acid, specifically, electrons are transferred from riconleic acid to the gold nanoparticles, enhancing the surface potential of the nanoparticles and the repulsive force between their electronic double layers. PMID:26821883

  17. Isothermal titration calorimetry with micelles: Thermodynamics of inhibitor binding to carnitine palmitoyltransferase 2 membrane protein.

    PubMed

    Perspicace, Samantha; Rufer, Arne C; Thoma, Ralf; Mueller, Francis; Hennig, Michael; Ceccarelli, Simona; Schulz-Gasch, Tanja; Seelig, Joachim

    2013-01-01

    Carnitine palmitoyl transferase 2 (CPT-2) is a key enzyme in the mitochondrial fatty acid metabolism. The active site is comprised of a Y-shaped tunnel with distinct binding sites for the substrate acylcarnitine and the cofactor CoA. We investigated the thermodynamics of binding of four inhibitors directed against either the CoA or the acylcarnitine binding sites using isothermal titration calorimetry (ITC). CPT-2 is a monotopic membrane protein and was solubilized by β-octylglucoside (β-OG) above its critical micellar concentration (CMC) to perform inhibitor titrations in solutions containing detergent micelles. The CMC of β-OG in the presence of inhibitors was measured with ITC and small variations were observed. The inhibitors bound to rat CPT-2 (rCPT-2) with 1:1 stoichiometry and the dissociation constants were in the range of K D = 2-20 μM. New X-ray structures and docking models of rCPT-2 in complex with inhibitors enable an analysis of the thermodynamic data in the context of the interaction observed for the individual binding sites of the ligands. For all ligands the binding enthalpy was exothermic, and enthalpy as well as entropy contributed to the binding reaction, with the exception of ST1326 for which binding was solely enthalpy-driven. The substrate analog ST1326 binds to the acylcarnitine binding site and a heat capacity change close to zero suggests a balance of electrostatic and hydrophobic interactions. An excellent correlation of the thermodynamic (ITC) and structural (X-ray crystallography, models) data was observed suggesting that ITC measurements provide valuable information for optimizing inhibitor binding in drug discovery. PMID:23772395

  18. Isothermal titration calorimetry with micelles: Thermodynamics of inhibitor binding to carnitine palmitoyltransferase 2 membrane protein☆

    PubMed Central

    Perspicace, Samantha; Rufer, Arne C.; Thoma, Ralf; Mueller, Francis; Hennig, Michael; Ceccarelli, Simona; Schulz-Gasch, Tanja; Seelig, Joachim

    2013-01-01

    Carnitine palmitoyl transferase 2 (CPT-2) is a key enzyme in the mitochondrial fatty acid metabolism. The active site is comprised of a Y-shaped tunnel with distinct binding sites for the substrate acylcarnitine and the cofactor CoA. We investigated the thermodynamics of binding of four inhibitors directed against either the CoA or the acylcarnitine binding sites using isothermal titration calorimetry (ITC). CPT-2 is a monotopic membrane protein and was solubilized by β-octylglucoside (β-OG) above its critical micellar concentration (CMC) to perform inhibitor titrations in solutions containing detergent micelles. The CMC of β-OG in the presence of inhibitors was measured with ITC and small variations were observed. The inhibitors bound to rat CPT-2 (rCPT-2) with 1:1 stoichiometry and the dissociation constants were in the range of KD = 2–20 μM. New X-ray structures and docking models of rCPT-2 in complex with inhibitors enable an analysis of the thermodynamic data in the context of the interaction observed for the individual binding sites of the ligands. For all ligands the binding enthalpy was exothermic, and enthalpy as well as entropy contributed to the binding reaction, with the exception of ST1326 for which binding was solely enthalpy-driven. The substrate analog ST1326 binds to the acylcarnitine binding site and a heat capacity change close to zero suggests a balance of electrostatic and hydrophobic interactions. An excellent correlation of the thermodynamic (ITC) and structural (X-ray crystallography, models) data was observed suggesting that ITC measurements provide valuable information for optimizing inhibitor binding in drug discovery. PMID:23772395

  19. LC/ESI-MS/MS method for determination of salivary eicosapentaenoic acid concentration to arachidonic acid concentration ratio.

    PubMed

    Ogawa, Shoujiro; Tomaru, Koki; Matsumoto, Nagisa; Watanabe, Shui; Higashi, Tatsuya

    2016-01-01

    A simple liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method for determination of the eicosapentaenoic acid (EPA) concentration to arachidonic acid (AA) concentration ratio in human saliva has been developed. The EPA/AA ratio in serum or plasma is widely recognized as a useful indicator in identifying the risk of cardiovascular disease, especially atherosclerosis. The salivary EPA/AA ratio is expected to be a convenient alternative to the serum or plasma EPA/AA ratio, because saliva offers the advantages of easy and noninvasive sampling. The saliva was deproteinized with acetonitrile, purified using an Oasis HLB cartridge, and derivatized with 1-[(4-dimethylaminophenyl)carbonyl]piperazine (DAPPZ). The derivatized EPA and AA were subjected to LC/ESI-MS/MS, and the EPA/AA ratio was determined using the selected reaction monitoring mode. The DAPPZ-derivatization increased the ESI sensitivity by 100- and 300-fold for EPA and AA, respectively, and enabled the detection of trace fatty acids in saliva using a 200 μL sample. The assay reproducibility was satisfactory (relative standard deviation, <5.0%). The method was successfully applied to the measurement of the salivary EPA/AA ratios of healthy Japanese subjects and their changes owing to the supplementation of EPA. PMID:25620210

  20. Concentration methods for high-resolution THz spectroscopy of nucleic-acid biomolecules and crystals

    NASA Astrophysics Data System (ADS)

    Brown, E. R.; Zhang, W.; Mendoza, E. A.; Kuznetsova, Y.; Brueck, S. R. J.; Rahman, M.; Norton, M. L.

    2012-03-01

    Biomolecules can exhibit low-lying vibrational modes in the THz region which are detectable in transmission given a strong molecular dipole moment and optical depth, and a spectrometer of adequate sensitivity. The nucleic acids are particularly interesting because of applications such as label-free gene assay, bio-agent detection, etc. However for nucleic acids, sample preparation and THz coupling are of paramount importance because of the strong absorption by liquid water and the small concentration of molecules present in physiological solutions. Concentration methods become necessary to make the THz vibrational modes detectable, either by concentrating the nucleic-acid sample itself in a small volume but large area, or by concentrating the THz radiation down to the volume of the sample. This paper summarizes one type of the first method: nanofluidic channel arrays for biological nucleic acids; and two types of the second method: (1) a circular-waveguide pinhole, and (2) a circular-waveguide, conical-horn coupling structure, both for DNA crystals. The first method has been demonstrated on a very short artificial nucleic acid [small-interfering (si) RNA (17-to-25 bp)] and a much longer, biological molecule [Lambda-phage DNA (48.5 kbp)]. The second method has been demonstrated on small (~100 micron) single crystals of DNA grown by the sitting-drop method.

  1. Broiler skin color as affected by organic acids: influence of concentration and method of application.

    PubMed

    Bilgili, S F; Conner, D E; Pinion, J L; Tamblyn, K C

    1998-05-01

    Color of broiler skin was evaluated after exposure to organic acids under various concentrations and simulated potential plant application conditions. Breast skin from chilled broiler carcasses was treated with acetic (AA), citric (CA), lactic (LA), malic (ML), mandelic (MN), propionic (PA), or tartaric (TA) acids at 0.5, 1, 2, 4, and 6% concentrations. Each acid and concentration was applied in simulated dip (23 C for 15 s), scalder (50 C for 2 min), and immersion chiller (1 C for 60 min) conditions. A tap water control was included with each application method. Objective color values of L* (lightness), a* (redness), and b* (yellowness) were measured before and after the treatments to calculate color differentials under a factorial arrangement of organic acids and concentrations. Skin lightness increased (P < 0.01) in simulated chiller as compared to dip and scalder applications. Skin redness was reduced significantly in scalder, and yellowness in dip and scalder applications, respectively. In simulated dip application, with the exception of PA, all acids decreased lightness and increased redness and yellowness values. Propionic acid had little affect on lightness and redness values, but decreased yellowness values. In simulated scalder application, with the exception of PA, all acids decreased lightness with increasing concentration. The redness values changed little in scalder application. However, yellowness values were increased with all acids, except for PA, which decreased yellowness values. In simulated chiller conditions, all acids, except for PA, decreased lightness and redness and increased yellowness values. Propionic acid increased lightness and decreased yellowness values significantly in chiller conditions. Alterations in skin color should be taken into account in the selection and application of organic acids as carcass disinfectants. PMID:9603365

  2. A method for analysis of vanillic acid in polar ice cores

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Greaves, J.; Saltzman, E. S.

    2015-02-01

    Biomass burning generates a wide range of organic compounds that are transported via aerosols to the polar ice sheets. Vanillic acid is a product of conifer lignin combustion, which has previously been observed in laboratory and ambient biomass burning aerosols. In this study a method was developed for analysis of vanillic acid in melted polar ice core samples. Vanillic acid was chromatographically separated using reversed-phase liquid chromatography (HPLC) and detected using electrospray ionization-triple quadrupole mass spectrometry (ESI-MS/MS). Using a 100 μL injection loop and analysis time of 4 min, we obtained a detection limit of 77 ppt (parts per trillion by mass) and an analytical precision of ±10%. Measurements of vanillic acid in Arctic ice core samples from the Siberian Akademii Nauk core are shown as an example application of the method.

  3. Development of a Method for the N-Arylation of Amino Acid Esters with Aryl Triflates.

    PubMed

    King, Sandra M; Buchwald, Stephen L

    2016-08-19

    A general method for the N-arylation of amino acid esters with aryl triflates is described. Both α- and β-amino acid esters, including methyl, tert-butyl, and benzyl esters, are viable substrates. Reaction optimization was carried out by design of experiment (DOE) analysis using JMP software. The mild reaction conditions, which use t-BuBrettPhos Pd G3 or G4 precatalyst, result in minimal racemization of the amino acid ester. This method is the first synthetic application of the t-BuBrettPhos Pd G4 precatalyst. Mechanistic studies show that the observed erosion in enantiomeric excess is due to racemization of the amino acid ester starting material and not of the product. PMID:27498618

  4. Methods and kits for nucleic acid analysis using fluorescence resonance energy transfer

    DOEpatents

    Kwok, Pui-Yan; Chen, Xiangning

    1999-01-01

    A method for detecting the presence of a target nucleotide or sequence of nucleotides in a nucleic acid is disclosed. The method is comprised of forming an oligonucleotide labeled with two fluorophores on the nucleic acid target site. The doubly labeled oligonucleotide is formed by addition of a singly labeled dideoxynucleoside triphosphate to a singly labeled polynucleotide or by ligation of two singly labeled polynucleotides. Detection of fluorescence resonance energy transfer upon denaturation indicates the presence of the target. Kits are also provided. The method is particularly applicable to genotyping.

  5. Biophysical and computational methods to analyze amino acid interaction networks in proteins.

    PubMed

    O'Rourke, Kathleen F; Gorman, Scott D; Boehr, David D

    2016-01-01

    Globular proteins are held together by interacting networks of amino acid residues. A number of different structural and computational methods have been developed to interrogate these amino acid networks. In this review, we describe some of these methods, including analyses of X-ray crystallographic data and structures, computer simulations, NMR data, and covariation among protein sequences, and indicate the critical insights that such methods provide into protein function. This information can be leveraged towards the design of new allosteric drugs, and the engineering of new protein function and protein regulation strategies. PMID:27441044

  6. Methods of staining target chromosomal DNA employing high complexity nucleic acid probes

    DOEpatents

    Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Ol'li-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

    2006-10-03

    Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

  7. Spectrophotometric and spectrofluorimetric methods for the determination of tranexamic acid in pharmaceutical formulation.

    PubMed

    El-Aroud, Khalifa Abulghasem; Abushoffa, Adel Mohamed; Abdellatef, Hisham Ezzat

    2007-03-01

    Two simple and sensitive spectrophotometric and fluorimetric methods for the determination of tranexamic acid in tablets are developed. The methods are based on condensation the primary amino group of tranexamic acid with acetyl acetone and formaldehyde producing a yellow coloured product, which is measured spectrophotometrically at 335 nm or fluorimetrically at 480 nm the colour was stable for at least 1 h. Beer's law was valid within a concentration rang of 0.05-2.0 microg ml-1 spectrophotometrically and 0.05-0.25 microg ml-1 fluorimetrically. All the variables were studied to optimize the reaction conditions. No interference was observed in the presence of common pharmaceutical excipints. The validity of both methods was tested by analyzing tranexamic acid in its pharmaceutical preparations. Good recoveries were obtained and the results were comparable with those obtained by standard method. PMID:17329872

  8. Study of acid diffusion behaves form PAG by using top coat method

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Atsushi; Matsumoto, Yoko

    2014-03-01

    Our past research on measurements of simulation parameters for ArF resists focused on establishing methods for measuring the following parameters:[1]-[4] • Development parameters[1] • PEB parameters[2] • Dill's ABC parameters[3] • Quencher parameter[4] We entered these parameters into a lithography simulator and performed ArF resist simulations.We then explored ways to optimize the ArF resist material and process. This paper reports on our study of methods for measuring the diffusion length of acid generated from PAG during exposures. In our experiment, we applied a PAG-containing top coat (TC) material (second layer) to a PAG-free ArF resist (first layer), then performed the exposure and PEB processes. The acid generated in the TC during the exposure diffused into the ArF resist in the lower layer (first layer) when PEB was performed. The process of developing this sample removed the TC in the second layer and the parts of the first layer into which the acid had diffused.We obtained the acid diffusion length based on the quantity of film removed by the development. We calculated the acid diffusion coefficient after varying the exposure value and repeating the measurement. For this report, we also performed measurements to determine how differences in PAG anion size, amount of quencher additive, and PEB temperature affected the acid diffusion coefficient.We entered the measurements obtained into the PROLITH simulator and explored the effects of acid diffusion on pattern profile.

  9. A method for determining thermophysical properties of organic material in aqueous solutions: Succinic acid

    NASA Astrophysics Data System (ADS)

    Riipinen, I.; Svenningsson, B.; Bilde, M.; Gaman, A.; Lehtinen, K. E. J.; Kulmala, M.

    2006-12-01

    A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets. Evaporation rates of succinic acid solution droplets have been measured using a TDMA system at controlled relative humidity (65%) and temperature (298 K). A temperature-dependent expression for the saturation vapour pressure of pure liquid phase succinic acid at atmospheric temperatures has been derived by analysing the evaporation rate data with a numerical model. The obtained saturation vapour pressure of liquid phase succinic acid is ln( p) = 118.41 - 16204.8/ T - 12.452ln( T). The vapour pressure is in unit of Pascal and the temperature in Kelvin. A linear expression for the enthalpy of vaporization for liquid state succinic acid is also presented. According to the results presented in the following, a literature expression for the vapour pressure of liquid phase succinic acid defined for temperatures higher than 461 K [Yaws, C.L., 2003. Yaws' Handbook of Thermodynamic and Physical Properties of Chemical Compounds, Knovel] can be extrapolated to atmospheric temperatures with very good accuracy. The results also suggest that at 298 K the mass accommodation coefficient of succinic acid is unity or very close to unity.

  10. Analysis of essential oils and fatty acids from Platycodi Radix using chemometric methods and retention indices.

    PubMed

    He, Min; Li, Yaping; Yan, Jun; Cao, Dongsheng; Liang, Yizeng

    2013-04-01

    The chemical composition of the essential oils and fatty acids among nine groups of Platycodi Radix in China was analyzed by gas chromatography-mass spectrometry. Complicated components were resolved using chemometric methods. Simultaneously, the various features among heuristic evolving latent projections, selective ion analysis and alternative moving window factor analysis were compared by using some experimental data. Temperature-programmed retention indices were applied in further identification of the chemical composition of the essential oils. The equivalent chain length, fraction chain length, and an established special retention indices library integrated with mass spectrometry were also applied to further identify the composition of fatty acids, including total fatty acids, esterified fatty acids and free fatty acids. A total of 121 different compounds accounting for 95.12-98.74% were identified among the essential oils. Chemical polymorphisms and variation existed in the essential oils of Platycodi Radix. Sixteen components were identified in fatty acids, and linoleic acid (18:2n-6c) and other unsaturated acid possess a characteristic majority. PMID:22964951

  11. Understanding the sprayed boric acid method for bulk doping of silicon ribbons

    NASA Astrophysics Data System (ADS)

    Silva, J. A.; Pêra, David; Brito, Miguel C.; Alves, Jorge Maia; Serra, João; Vallêra, A. M.

    2011-07-01

    The sprayed boric acid (SBA) method for bulk doping of silicon ribbons is investigated. Experimental procedures and main results are reviewed. Computational fluid dynamics and experimental tests using partial spraying suggest the role of gas transported evaporated boron oxide to explain the boron incorporation profiles along the sample. The industrial applicability of the SBA method is discussed.

  12. Method for separating mono- and di-octylphenyl phosphoric acid esters

    DOEpatents

    Arnold, Jr., Wesley D.

    1977-01-01

    A method for separating mono-octylphenyl phosphoric acid ester and di-octylphenyl phosphoric acid ester from a mixture thereof comprises reacting the ester mixture with a source of lithium or sodium ions to form a mixture of the phosphate salts; contacting the salt mixture with an organic solvent which causes the dioctylphenyl phosphate salt to be dissolved in the organic solvent phase and the mono-octylphenyl phosphate salt to exist in a solid phase; separating the phases; recovering the phosphate salts from their respective phases; and acidifying the recovered salts to form the original phosphoric acid esters.

  13. Isothermal titration calorimetry of ion-coupled membrane transporters

    PubMed Central

    SeCheol, Oh

    2015-01-01

    Binding of ligands, ranging from proteins to ions, to membrane proteins is associated with absorption or release of heat that can be detected by isothermal titration calorimetry (ITC). Such measurements not only provide binding affinities but also afford direct access to thermodynamic parameters of binding - enthalpy, entropy and heat capacity. These parameters can be interpreted in a structural context, allow discrimination between different binding mechanisms and guide drug design. In this review, we introduce advantages and limitations of ITC as a methodology to study molecular interactions of membrane proteins. We further describe case studies where ITC was used to analyze thermodynamic linkage between ions and substrates in ion-coupled transporters. Similar type of linkage analysis will likely be applicable to a wide range of transporters, channels, and receptors. PMID:25676707

  14. Solubility of strontium-substituted apatite by solid titration.

    PubMed

    Pan, H B; Li, Z Y; Lam, W M; Wong, J C; Darvell, B W; Luk, K D K; Lu, W W

    2009-06-01

    Solid titration was used to explore the solubility isotherms of partially (Srx-HAp, x=1, 5, 10, 40, 60 mol.%) and fully substituted strontium hydroxyapatite (Sr-HAp). Solubility increased with increasing strontium content. No phase other than strontium-substituted HAp, corresponding to the original titrant, was detected in the solid present at equilibrium; in particular, dicalcium hydrogen phosphate was not detected at low pH. The increase in solubility with strontium content is interpreted as a destabilization of the crystal structure by the larger strontium ion. Carbonated HAp was formed in simulated body fluid containing carbonate on seeding with Sr10-HAp, but the precipitate was strontium-substituted on seeding with Sr-HAp. Strontium-substituted HAp might be usable as a template for the growth of new bone, since nucleation appears to be facilitated. PMID:19135423

  15. Sailing on the "C": A Vitamin Titration with a Twist

    NASA Astrophysics Data System (ADS)

    Sowa, S.; Kondo, A. E.

    2003-05-01

    The experiment takes the traditional redox titration of vitamin C using iodine with starch as an indicator, and presents it to the student as a challenge in guided-inquiry format. Two versions, with different levels of difficulty, are provided, to accommodate students with varying levels of problem-solving skills. The "challenge" is both quantitative and qualitative: if you were an eighteenth-century sea captain packing for a voyage to the New World, would you take oranges, lemons, limes, or grapefruits to prevent your crew from getting scurvy? The challenge ties in history, nutrition, and health with chemistry, and provides students an opportunity to work with familiar food products in the laboratory.

  16. Preparation To Minimize Buffer Mismatch in Isothermal Titration Calorimetry Experiments.

    PubMed

    Bian, Xuelin; Lockless, Steve W

    2016-05-17

    There is a growing need to study ligand binding to proteins in native or complex solution using isothermal titration calorimetry (ITC). For example, it is desirable to measure ligand binding to membrane proteins in more native lipid-like environments such as bicelles, where ligands can access both sides of the membrane in a homogeneous environment. A critical step to obtain high signal-to-noise is matching the reaction chamber solution to the ligand solution, typically through a final dialysis or gel filtration step. However, to obtain reproducible bicelles, the lipid concentrations must be carefully controlled which eliminates the use of dialysis that can disrupt these parameters. Here, we report and validate a rapid preparation ITC (RP-ITC) approach to measure ligand binding without the need for a dialysis step. This general approach is used to quantify ion binding to a K(+) channel embedded in bicelles and can be applied to complex, less defined systems. PMID:27092566

  17. Discriminability of nicotine in tobacco smoke: implications for titration.

    PubMed

    Rose, J E

    1984-01-01

    Cigarette smokers were presented with puffs from either high (2.5 mg), medium (1.5 mg) or low (.5 mg) nicotine cigarettes in order to determine their ability to discriminate nicotine delivery in tobacco smoke. Puffs were presented in random order during each of two conditions and tar content was controlled by using research cigarettes and a smoke mixing device that varied only nicotine. The first condition allowed olfactory stimuli to be used in discrimination, while the second condition blocked olfaction by occluding subjects' nostrils. In both conditions, subjects discriminated between the nicotine content of different puffs, with higher nicotine puffs rated as significantly stronger (by roughly 50%). Subjective desirability ratings did not vary with nicotine delivery. The implications of the magnitude of change in subjects' ratings for theories of nicotine titration are discussed. PMID:6741679

  18. Ultrasensitivity by Molecular Titration in Spatially Propagating Enzymatic Reactions

    PubMed Central

    Semenov, Sergey N.; Markvoort, Albert J.; Gevers, Wouter B.L.; Piruska, Aigars; de Greef, Tom F.A.; Huck, Wilhelm T.S.

    2013-01-01

    Delineating design principles of biological systems by reconstitution of purified components offers a platform to gauge the influence of critical physicochemical parameters on minimal biological systems of reduced complexity. Here we unravel the effect of strong reversible inhibitors on the spatiotemporal propagation of enzymatic reactions in a confined environment in vitro. We use micropatterned, enzyme-laden agarose gels which are stamped on polyacrylamide films containing immobilized substrates and reversible inhibitors. Quantitative fluorescence imaging combined with detailed numerical simulations of the reaction-diffusion process reveal that a shallow gradient of enzyme is converted into a steep product gradient by addition of strong inhibitors, consistent with a mathematical model of molecular titration. The results confirm that ultrasensitive and threshold effects at the molecular level can convert a graded input signal to a steep spatial response at macroscopic length scales. PMID:23972857

  19. Fast and Sensitive Method for Determination of Domoic Acid in Mussel Tissue.

    PubMed

    Barbaro, Elena; Zangrando, Roberta; Barbante, Carlo; Gambaro, Andrea

    2016-01-01

    Domoic acid (DA), a neurotoxic amino acid produced by diatoms, is the main cause of amnesic shellfish poisoning (ASP). In this work, we propose a very simple and fast analytical method to determine DA in mussel tissue. The method consists of two consecutive extractions and requires no purification steps, due to a reduction of the extraction of the interfering species and the application of very sensitive and selective HILIC-MS/MS method. The procedural method was validated through the estimation of trueness, extract yield, precision, detection, and quantification limits of analytical method. The sample preparation was also evaluated through qualitative and quantitative evaluations of the matrix effect. These evaluations were conducted both on the DA-free matrix spiked with known DA concentration and on the reference certified material (RCM). We developed a very selective LC-MS/MS method with a very low value of method detection limit (9 ng g(-1)) without cleanup steps. PMID:26904720

  20. Fast and Sensitive Method for Determination of Domoic Acid in Mussel Tissue

    PubMed Central

    Barbaro, Elena; Zangrando, Roberta; Barbante, Carlo; Gambaro, Andrea

    2016-01-01

    Domoic acid (DA), a neurotoxic amino acid produced by diatoms, is the main cause of amnesic shellfish poisoning (ASP). In this work, we propose a very simple and fast analytical method to determine DA in mussel tissue. The method consists of two consecutive extractions and requires no purification steps, due to a reduction of the extraction of the interfering species and the application of very sensitive and selective HILIC-MS/MS method. The procedural method was validated through the estimation of trueness, extract yield, precision, detection, and quantification limits of analytical method. The sample preparation was also evaluated through qualitative and quantitative evaluations of the matrix effect. These evaluations were conducted both on the DA-free matrix spiked with known DA concentration and on the reference certified material (RCM). We developed a very selective LC-MS/MS method with a very low value of method detection limit (9 ng g−1) without cleanup steps. PMID:26904720

  1. Spectrophotometric method for fast quantification of ascorbic acid and dehydroascorbic acid in simple matrix for kinetics measurements.

    PubMed

    Gómez Ruiz, Braulio; Roux, Stéphanie; Courtois, Francis; Bonazzi, Catherine

    2016-11-15

    A simple, rapid and reliable method was developed for quantifying ascorbic (AA) and dehydroascorbic (DHAA) acids and validated in 20mM malate buffer (pH 3.8). It consists in a spectrophotometric measurement of AA, either directly on the solution added with metaphosphoric acid or after reduction of DHAA into AA by dithiothreitol. This method was developed with real time measurement of reactions kinetics in bulk reactors in mind, and was checked in terms of linearity, limits of detection and quantification, fidelity and accuracy. The linearity was found satisfactory on the range of 0-6.95mM with limits of detection and quantification of 0.236mM and 0.467mM, respectively. The method was found acceptable in terms of fidelity and accuracy with a coefficient of variation for repeatability and reproducibility below 6% for AA and below 15% for DHAA, and with a recovery range of 97-102% for AA and 88-112% for DHAA. PMID:27283671

  2. [Effect of drying methods on monoterpenes, phenolic acids and flavonoids in Mentha haplocalyx].

    PubMed

    Zhu, Shao-qing; Zhu, Zhen-hua; Guo, Sheng; Zhao, Yu-yang; Lu, Xue-jun; Sha, Xiu-xiu; Qian, Da-wei; Duan, Jin-ao

    2015-12-01

    To provide a scientific basis for the selection of the appropriate drying method for Mentha Haplocalyx Herba (MHH), determine 2 monoterpenes, 4 phenolic acids and 5 flavonoids in MHH by GC-MS and UPLC-TQ-MS methods, and investigate the effects of the drying methods on the changes in contents of these analytes. The qualities of products obtained with different drying methods were evaluated by the multivariate statistical method of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Results showed that the drying methods had the greatest impact on menthol, caffeic acid, and rosemary acid, which were followed by chlorogenic acid and diosmetin-7-O-glucoside. The contents in these analytes processed with hot-air-drying method were higher than those with microwave-drying and infrared-drying methods at the same temperatures. The contents in these analytes processed under low temperature (40-45 °C) were higher than those under higher temperature (60-70 °C). Above all, the contents in phenolic acids processed with microwave fixation (exposed under microwave at 100 °C for several minutes) were obviously higher than those of not being processed, showing an inhibition of some enzymes in samples after fixation. The TOPSIS evaluation showed that the variable temperature drying method of 'Hot-Air 45-60 °C' was the most suitable approach for the primary drying processing of MHH. The results could provide the scientific basis for the selection of appropriate drying method for MHH, and helpful reference for the primary drying proces of herbs containing volatile chemical components. PMID:27245035

  3. Penta- and hexa-coordinate ferric hemoglobins display distinct pH titration profiles measured by Soret peak shifts.

    PubMed

    Uppal, Sheetal; Kumar, Amit; Shandilya, Manish; Mukhi, Nitika; Singh, Amit Kumar; Kateriya, Suneel; Kaur, Jagreet; Kundu, Suman

    2016-10-01

    Hemoglobins with diverse characteristics have been identified in all kingdoms of life. Their ubiquitous presence indicates that these proteins play important roles in physiology, though function for all hemoglobins are not yet established with certainty. Their physiological role may depend on their ability to bind ligands, which in turn is dictated by their heme chemistry. However, we have an incomplete understanding of the mechanism of ligand binding for these newly discovered hemoglobins and the measurement of their kinetic parameters depend on their coordination at the heme iron. To gain insights into their functional role, it is important to categorize the new hemoglobins into either penta- or hexa-coordinated varieties. We demonstrate that simple pH titration and absorbance measurements can determine the coordination state of heme iron atom in ferric hemoglobins, thus providing unambiguous information about the classification of new globins. This method is rapid, sensitive and requires low concentration of protein. Penta- and hexa-coordinate hemoglobins displayed distinct pH titration profiles as observed in a variety of hemoglobins. The pentacoordinate distal histidine mutant proteins of hexacoordinate hemoglobins and ligand-bound hexacoordinate forms of pentacoordinate hemoglobins reverse the pH titration profiles, thus validating the sensitivity of this spectroscopic technique. PMID:27449132

  4. Developing a Physiotherapy-Specific Preliminary Clinical Decision-Making Tool for Oxygen Titration: A Modified Delphi Study

    PubMed Central

    Duong, Michelle; Bertin, Kendra; Henry, Renee; Singh, Deepti; Timmins, Nolla; Brooks, Dina; Mathur, Sunita

    2014-01-01

    ABSTRACT Purpose: To develop and evaluate a preliminary clinical decision-making tool (CDMT) to assist physiotherapists in titrating oxygen for acutely ill adults in Ontario. Methods: A panel of 14 experienced cardiorespiratory physiotherapists was recruited. Factors relating to oxygen titration were identified using a modified Delphi technique. Four rounds of questionnaires were conducted, during which the goals were to (1) generate factors, (2) reduce factors and debate contentious factors, (3) finalize factors and develop the preliminary CDMT, and (4) evaluate the usability of the tool in a clinical context. Results: The panel reached consensus on a total of 89 factors, which were compiled to create the preliminary CDMT. The global tool reached consensus for sensibility, receiving a mean score of 6/7 on a 7-point Likert-type scale (1=unacceptable; 7=excellent). Five of the nine individual components of evaluation of the tool achieved scores ≥6.0; the remaining four had mean scores between 5.4 and 5.9. Conclusion: This study produced a preliminary CDMT for oxygen titration, which the panel agreed was highly comprehensible and globally sensible. Further research is necessary to evaluate the sensibility and applicability of the tool in a clinical setting. PMID:25125782

  5. Determination of the strong acidity of atmospheric fine-particles (<2. 5 mum) using annular denuder technology. Standard method, enhanced method

    SciTech Connect

    Purdue, L.J.

    1992-11-01

    The report is a standardized methodology description for the determination of strong acidity of fine particles (less than 2.5 micrometers) in ambient air using annular denuder technology. The methodology description includes two parts: Part A - Standard Method and Part B - Enhanced Method. The Standard Method utilizes a denuder for removing ammonia and a filter assembly for determination of atmospheric strong acidity fine particle aerosols in ambient air, but does not account for potential interferences from nitric acid, ammonium nitrate aerosol or other ammonium salts which might bias the acidity measurement. The Enhanced Method adds an additional denuder upstream of the filter assembly to selectively remove acid gases (nitric acid vapors, nitrous acid and sulfur dioxide) from the gas stream prior to filtration. In addition, backup nylon and citric acid impregnated filters are used to correct for biases due to the dissociation of ammonium nitrate aerosol.

  6. Estimation of glycated hemoglobin by 2,6-dimethylphenol: Sulphuric acid conventional method.

    PubMed

    Mallya, H M; Pattabiraman, T N

    2001-01-01

    Glycated hemoglobin levels in hemolysate of normal and diabetic patients were determined by the 2,6-dimethylphenol:57.5% sulphuric acid conventional method and the values were 0.39±025 and 0.69±0.21 moles of hydroxymethylfurfural(HMF)/mole of globin, respectively. The mean increase in glycated hemoglobin values in diabetics (1.8fold) was highly significant (p<0.001). A good correlation (r=0.95) was found between the glycated hemoglobin values obtained by this method and the phenol:sulphuric acid method. The values obtained by former method were about 1.2-1.4 times the values by the phenol:sulphuric acid method. This study indicates that conventional 2,6-dimethylphenol: 57.5% sulphuric acid method is more sensitive for the estimation of glycated hemoglobin than any other method based on the same principle. It is less time consuming, reliable and hence can be employed for the routine laboratory estimation of glycated hemoglobin for the assessment of glycemic control. PMID:23105290

  7. HPLC method for comparative study on tissue distribution in rat after oral administration of salvianolic acid B and phenolic acids from Salvia miltiorrhiza.

    PubMed

    Xu, Man; Fu, Gang; Qiao, Xue; Wu, Wan-Ying; Guo, Hui; Liu, Ai-Hua; Sun, Jiang-Hao; Guo, De-An

    2007-10-01

    A sensitive and selective high-performance liquid chromatography method was developed and validated to determine the prototype of salvianolic acid B and the metabolites of phenolic acids (protocatechuic acid, vanillic acid and ferulic acid) in rat tissues after oral administration of total phenolic acids and salvianolic acid B extracted from the roots of Salvia miltiorrhiza, respectively. The tissue samples were treated with a simple liquid-liquid extraction prior to HPLC. Analysis of the extract was performed on a reverse-phase C(18) column with a mobile phase consisting of acetonitrile and 0.05% trifluoracetic acid. The calibration curves for the four phenolic acids were linear in the given concentration ranges. The intra-day and inter-day relative standard deviations in the measurement of quality control samples were less than 10% and the accuracies were in the range of 88-115%. The average recoveries of all the tissues ranged from 78.0 to 111.8%. This method was successfully applied to evaluate the distribution of the four phenolic acids in rat tissues after oral administration of total phenolic acids of Salvia miltiorrhiza or salvianolic acid B and the possible metabolic pathway was illustrated. PMID:17549679

  8. Spectrophotometric method for the determination of sorbic acid in various food samples with iron(III) and 2-thiobarbituric acid as reagents.

    PubMed

    Lau, O W; Luk, S F; Lam, R K

    1989-02-01

    A simple, rapid and accurate spectrophotometric method has been developed for the determination of sorbic acid in various food samples based on the oxidation of sorbic acid by iron(III) at 100 degrees C to malonaldehyde, which then reacts with 2-thiobarbituric acid to form a reddish brown product. The optimum experimental conditions for colour development have been assessed. Absorbance measurements were made at 529 nm in the presence of 0.4% m/V citric acid. The calibration graph was linear for 0-6 micrograms ml-1 of sorbic acid with a slope of 0.131 A micrograms-1 ml. The recoveries of sorbic acid at concentrations of 164-557 micrograms ml-1 ranged from 96 to 103%. The relative standard deviations of ten replicate determinations of sorbic acid in a synthetic cream soda sample spiked with 573 micrograms ml-1 of sorbic acid and in an onion juice sample containing 82 micrograms ml-1 of sorbic acid were 1.6 and 1.9%, respectively. Interferences from several common food additives can be minimised by extracting sorbic acid with diethyl ether and then back-extracting the acid with sodium hydrogen carbonate. The method has been applied successfully to the determination of sorbic acid in a wide range of food samples including beverages, cake, cake mate, garlic bread sprinkle, onion juice, oyster flavoured sauce and grenadine syrup. PMID:2712320

  9. Mercury analysis of various types of coal using acid extraction and pyrolysis methods

    SciTech Connect

    Jae Young Park; Jong Hyun Won; Tai Gyu Lee

    2006-12-15

    The mercury contents of various types of coal currently consumed in Korea were analyzed using acid extraction and pyrolysis methods. The results of analysis by acid extraction and pyrolysis methods were compared and discussed. Generally, high mercury concentrations of 105.6 to 434.5 ng/g (by acid extraction) and 125.7 to 475.4 ng/g (by pyrolysis) were obtained for tested anthracite coals in this study. For bituminous coals, the mercury contents were 11.5-48 ng/g (by acid extraction) and 12.5-52.4 ng/g (by pyrolysis). For coal samples, much simpler and far less time-consuming pyrolysis method tends to give higher values for the Hg concentration than the acid extraction method (by less than 10%) because of the interference from a UV absorption by SOx generated during thermal destruction of coal matrix. Also, further analysis shows that coals with higher densities have higher mercury contents and that the sulfur and mercury contents of coals are positively correlated with each other. 10 refs., 4 figs., 2 tabs.

  10. Energy Minimization of Discrete Protein Titration State Models Using Graph Theory.

    PubMed

    Purvine, Emilie; Monson, Kyle; Jurrus, Elizabeth; Star, Keith; Baker, Nathan A

    2016-08-25

    There are several applications in computational biophysics that require the optimization of discrete interacting states, for example, amino acid titration states, ligand oxidation states, or discrete rotamer angles. Such optimization can be very time-consuming as it scales exponentially in the number of sites to be optimized. In this paper, we describe a new polynomial time algorithm for optimization of discrete states in macromolecular systems. This algorithm was adapted from image processing and uses techniques from discrete mathematics and graph theory to restate the optimization problem in terms of "maximum flow-minimum cut" graph analysis. The interaction energy graph, a graph in which vertices (amino acids) and edges (interactions) are weighted with their respective energies, is transformed into a flow network in which the value of the minimum cut in the network equals the minimum free energy of the protein and the cut itself encodes the state that achieves the minimum free energy. Because of its deterministic nature and polynomial time performance, this algorithm has the potential to allow for the ionization state of larger proteins to be discovered. PMID:27089174

  11. Effects of Acute and Chronic Cocaine Administration on Titrating-Delay Matching-to-Sample Performance

    ERIC Educational Resources Information Center

    Kangas, Brian D.; Branch, Marc N.

    2012-01-01

    The effects of cocaine were examined under a titrating-delay matching-to-sample procedure. In this procedure, the delay between sample stimulus offset and comparison stimuli onset adjusts as a function of the subject's performance. Specifically, matches increase the delay and mismatches decrease the delay. Titrated delay values served as the…

  12. Methods of refining and producing dibasic esters and acids from natural oil feedstocks

    DOEpatents

    Snead, Thomas E.; Cohen, Steven A.; Gildon, Demond L.

    2016-03-15

    Methods are provided for refining natural oil feedstocks and producing dibasic esters and/or dibasic acids. The methods comprise reacting a terminal olefin with an internal olefin in the presence of a metathesis catalyst to form a dibasic ester and/or dibasic acid. In certain embodiments, the olefin esters are formed by reacting the feedstock in the presence of a metathesis catalyst under conditions sufficient to form a metathesized product comprising olefins and esters, separating the olefins from the esters in the metathesized product, and transesterifying the esters in the presence of an alcohol to form a transesterified product having olefin esters.

  13. Methods of refining and producing dibasic esters and acids from natural oil feedstocks

    SciTech Connect

    Snead, Thomas E; Cohen, Steven A; Gildon, Demond L

    2015-04-07

    Methods are provided for refining natural oil feedstocks and producing dibasic esters and/or dibasic acids. The methods comprise reacting a terminal olefin with an internal olefin in the presence of a metathesis catalyst to form a dibasic ester and/or dibasic acid. In certain embodiments, the olefin esters are formed by reacting the feedstock in the presence of a metathesis catalyst under conditions sufficient to form a metathesized product comprising olefins and esters, separating the olefins from the esters in the metathesized product, and transesterifying the esters in the presence of an alcohol to form a transesterified product having olefin esters.

  14. Methods of refining and producing dibasic esters and acids from natural oil feedstocks

    DOEpatents

    Snead, Thomas E.; Cohen, Steven A.; Gildon, Demond L.

    2016-06-14

    Methods and systems for making dibasic esters and/or dibasic acids using metathesis are generally disclosed. In some embodiments, the methods comprise reacting a terminal olefin ester with an internal olefin ester in the presence of a metathesis catalyst to form a dibasic ester and/or dibasic acid. In some embodiments, the terminal olefin ester or the internal olefin ester are derived from a renewable feedstock, such as a natural oil feedstock. In some such embodiments, the natural oil feedstock, or a transesterified derivative thereof, is metathesized to make the terminal olefin ester or the internal olefin ester.

  15. Applicability Comparison of Methods for Acid Generation Assessment of Rock Samples

    NASA Astrophysics Data System (ADS)

    Oh, Chamteut; Ji, Sangwoo; Yim, Giljae; Cheong, Youngwook

    2014-05-01

    Minerals including various forms of sulfur could generate AMD (Acid Mine Drainage) or ARD (Acid Rock Drainage), which can have serious effects on the ecosystem and even on human when exposed to air and/or water. To minimize the hazards by acid drainage, it is necessary to assess in advance the acid generation possibility of rocks and estimate the amount of acid generation. Because of its relatively simple and effective experiment procedure, the method of combining the results of ABA (Acid Base Accounting) and NAG (Net Acid Generation) tests have been commonly used in determining acid drainage conditions. The simplicity and effectiveness of the above method however, are derived from massive assumptions of simplified chemical reactions and this often leads to results of classifying the samples as UC (Uncertain) which would then require additional experimental or field data to reclassify them properly. This paper therefore, attempts to find the reasons that cause samples to be classified as UC and suggest new series of experiments where samples can be reclassified appropriately. Study precedents on evaluating potential acid generation and neutralization capacity were reviewed and as a result three individual experiments were selected in the light of applicability and compatibility of minimizing unnecessary influence among other experiments. The proposed experiments include sulfur speciation, ABCC (Acid Buffering Characteristic Curve), and Modified NAG which are all improved versions of existing experiments of Total S, ANC (Acid Neutralizing Capacity), and NAG respectively. To assure the applicability of the experiments, 36 samples from 19 sites with diverse geologies, field properties, and weathering conditions were collected. The samples were then subject to existing experiments and as a result, 14 samples which either were classified as UC or could be used as a comparison group had been selected. Afterwards, the selected samples were used to conduct the suggested

  16. Effects of the traditional method and an alternative parboiling process on the fatty acids, vitamin E, γ-oryzanol and phenolic acids of glutinous rice.

    PubMed

    Thammapat, Pornpisanu; Meeso, Naret; Siriamornpun, Sirithon

    2016-03-01

    The impacts of traditional and alternative parboiling processes on the concentrations of fatty acids, tocopherol, tocotrienol, γ-oryzanol and phenolic acids in glutinous rice were investigated. Differences between the two methods were the soaking temperatures and the steaming methods. Results showed that parboiling processes significantly increased the concentrations of saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), γ-oryzanol, γ-tocotrienol and total phenolic acids (TPA) in glutinous rice, while α-tocopherol, γ-tocopherol and polyunsaturated fatty acids (PUFA) decreased (p<0.05). Both the traditional and alternative parboiling methods increased the levels of γ-oryzanol by three or fourfold compared with the level of γ-oryzanol in raw rice. Parboiling caused both adverse and favorable effects on phenolic acids content (p<0.05). We found that glutinous rice, parboiled using our newly developed method, had higher levels of PUFA, total vitamin E, γ-oryzanol, hydrobenzoic acid, hydroxycinnamic acid and TPA compared to the traditional method. PMID:26471549

  17. The thermo-hand method: evaluation of a new indicator pad for acid permeation of chemical protective gloves.

    PubMed

    Vo, Evanly; Nicholson, Jonathan; Gao, Pengfei; Zhuang, Zhenzhen; Berardinelli, Stephen P

    2003-01-01

    The thermo-hand method was developed to evaluate a new indicator pad for acid permeation through chemical protective gloves under in-use conditions (controlled conditions for the hand's skin temperature, hand movements, and relative humidity inside gloves). An indicator pad was used to detect both organic and inorganic acid permeation through glove materials. Breakthrough times for five types of gloves were determined and found to range from 5 to 308 min for propionic acid, from 4 to 293 min for acrylic acid, and from 15 min to >6 hours for HCl. Quantification was performed for propionic and acrylic acids following solvent desorption and gas chromatography. Both acids exhibited >99% adsorption (including the volume of acid, which reacted with an indicator to contribute the color change) on the pads at a spiking level of 1.8 micro L for each acid. Acid recovery for the system was calculated for each acid, with results ranging from 52-72% (RSD < or =4.0%) for both acids over the spiking range 0.2-1.8 micro L. The quantitative mass of the acids on the pads at the time of breakthrough detection ranged from 253-276 and 270-296 micro g/cm(2) for propionic acid and acrylic acid, respectively. The thermo-hand method and a new acid indicator pad together should be useful in detecting, collecting, and quantitatively analyzing acid permeation samples in the workplace. PMID:14674803

  18. Tested Demonstrations: Buffer Capacity of Various Acetic Acid-Sodium Acetate Systems: A Lecture Experiment.

    ERIC Educational Resources Information Center

    Donahue, Craig J.; Panek, Mary G.

    1985-01-01

    Background information and procedures are provided for a lecture experiment which uses indicators to illustrate the concept of differing buffer capacities by titrating acetic acid/sodium acetate buffers with 1.0 molar hydrochloric acid and 1.0 molar sodium hydroxide. A table with data used to plot the titration curve is included. (JN)

  19. Potentiometric titration of sulfate with lead and barium ions with various indicating electrodes

    SciTech Connect

    Selig, W.S.

    1984-01-01

    Several types of graphite were used as sensors in the potentiometric titration of 25 to 75 ..mu..mol of sulfate vs. lead(II) and barium(II) and compared with titrations obtained with a lead ion-selective electrode (ISE). Pyrolytic graphite and high-density graphite, conditioned in neutral potassium permanganate, were found to be good alternatives to the lead ISE. A qualitative study was made of a variety of commercially available ISE's and other materials as sensors in the titration of 5 ..mu..mol of sulfate vs lead(II). Every ISE and conducting material tested yielded a usable response. While that of the commonly used lead ISE was largest, some other ISE's and metal rods also function satisfactorily as sensors in this titration. All titrations were carried out in a partially nonaqueous medium, which is required even for the lead ISE at the low sulfate levels investigated. 18 references, 4 figures, 5 tables.

  20. Nonaqueous potentiometric titration and elemental analysis of high-boiling distillates of Saudi Arabian crude oils

    SciTech Connect

    Ali, M.F.; Ali, M.A. )

    1988-12-01

    Nonaqueous potentiometric titration and elemental analysis were used to study basic and nonbasic functionalities present in high-boiling distillates of four Saudi Arabian crude oils. Model nitrogen compounds were titrated under similar titration conditions to differentiate them into strong, weak and nonbasic species. The strong bses titrated were due to the presence of of pyridine and its benzologs like acridines, phenanthridines and quionolines. The weak bases titrated were due to phenazxines and amides whereas the pyrroles, indoles and carbazoles were found to be nonbasic in nature. The total nitrogen and the total basic nitrogen compounds were generally found to be in very low concentration in the four crude oil distillates. A gradual decrease in the basicity of the distillates was found from Arab Heavy to Arab Extra Light through Arab Medium and Arab Light crude oils.

  1. Comparison of official methods for 'readily oxidizable substances' in propionic acid as a food additive.

    PubMed

    Ishiwata, H; Takeda, Y; Kawasaki, Y; Kubota, H; Yamada, T

    1996-01-01

    The official methods for 'readily oxidizable substances (ROS)' in propionic acid as a food additive were compared. The methods examined were those adopted in the Compendium of Food Additive Specifications (CFAS) by the Joint FAO-WHO Expert Committee on Food Additives, FAO, The Japanese Standards for Food Additives (JSFA) by the Ministry of Health and Welfare, Japan, and the Food Chemicals Codex (FCC) by the National Research Council, USA. The methods given in CFAS and JSFA are the same (potassium permanganate consumption). However, by this method, manganese (VII) in potassium permanganate was readily reduced to colourless manganese(II) with some substances contained in the propionic acid before reacting with aldehydes, which are generally considered as 'readily oxidizable substances', to form brown manganese (IV) oxide. The FCC method (bromine consumption) for 'ROS' could be recommended because it was able to obtain quantitative results of 'ROS', including aldehydes. PMID:8647299

  2. Preparation of κ-carra-oligosaccharides with microwave assisted acid hydrolysis method

    NASA Astrophysics Data System (ADS)

    Li, Guangsheng; Zhao, Xia; Lv, Youjing; Li, Miaomiao; Yu, Guangli

    2015-04-01

    A rapid method of microwave assisted acid hydrolysis was established to prepare κ-carra-oligosaccharides. The optimal hydrolysis condition was determined by an orthogonal test. The degree of polymerization (DP) of oligosaccharides was detected by high performance thin layer chromatography (HPTLC) and polyacrylamide gel electrophoresis (PAGE). Considering the results of HPTLC and PAGE, the optimum condition of microwave assisted acid hydrolysis was determined. The concentration of κ-carrageenan was 5 mg mL-1; the reaction solution was adjusted to pH 3 with diluted hydrochloric acid; the solution was hydrolyzed under microwave irradiation at 100 for 15 °C min. Oligosaccharides were separated by a Superdex 30 column (2.6 cm × 90 cm) using AKTA Purifier UPC100 and detected with an online refractive index detector. Each fraction was characterized by electrospray ionization mass spectrometry (ESI-MS). The data showed that odd-numbered κ-carra-oligosaccharides with DP ranging from 3 to 21 could be obtained with this method, and the structures of the oligosaccharides were consistent with those obtained by traditional mild acid hydrolysis. The new method was more convenient, efficient and environment-friendly than traditional mild acid hydrolysis. Our results provided a useful reference for the preparation of oligosaccharides from other polysaccharides.

  3. Capillary electrophoresis method with UV-detection for analysis of free amino acids concentrations in food.

    PubMed

    Omar, Mei Musa Ali; Elbashir, Abdalla Ahmed; Schmitz, Oliver J

    2017-01-01

    Simple and inexpensive capillary electrophoresis with UV-detection method (CE-UV) was optimized and validated for determination of six amino acids namely (alanine, asparagine, glutamine, proline, serine and valine) for Sudanese food. Amino acids in the samples were derivatized with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) prior to CE-UV analysis. Labeling reaction conditions (100mM borate buffer at pH 8.5, labeling reaction time 60min, temperature 70°C and NBD-Cl concentration 40mM) were systematically investigated. The optimal conditions for the separation were 100mM borate buffer at pH 9.7 and detected at 475nm. The method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), precision (repeatability) (RSD%) and accuracy (recovery). Good linearity was achieved for all amino acids (r(2)>0.9981) in the concentration range of 2.5-40mg/L. The LODs in the range of 0.32-0.56mg/L were obtained. Recoveries of amino acids ranging from 85% to 108%, (n=3) were obtained. The validated method was successfully applied for the determination of amino acids for Sudanese food samples. PMID:27507479

  4. pH Replica-Exchange Method based on discrete protonation states

    PubMed Central

    Itoh, Satoru G.; Damjanović, Ana; Brooks, Bernard R.

    2012-01-01

    We propose a new algorithm for obtaining proton titration curves of ionizable residues. The algorithm is a pH replica-exchange method (PHREM) which is based on the constant pH algorithm of Mongan et al. [1]. In the original replica-exchange method, simulations of different replicas are performed at different temperature, and the temperatures are exchanged between the replicas. In our pH replica-exchange method, simulations of different replicas are performed at different pH values, and the pHs are exchanged between the replicas. The PHREM was applied to a blocked amino acid and to two protein systems (Snake Cardiotoxin and Turkey Ovomucoid Third Domain), in conjunction with a generalized Born implicit solvent. The performance and accuracy of this algorithm and the original constant pH method (PHMD) were compared. For a single set of simulations at different pHs, the use of PHREM yields more accurate Hill coefficients of titratable residues. By performing multiple sets of constant pH simulations started with different initial states the accuracy of predicted pKa values and Hill coefficients obtained with PHREM and PHMD methods becomes comparable. However, the PHREM algorithm exhibits better samplings of the protonation states of titratable residues and less scatter of the titration points and thus better precision of measured pKa values and Hill coefficients. In addition, PHREM exhibits faster convergence of individual simulations than the original constant pH algorithm. PMID:22002801

  5. Net alkalinity and net acidity 2: Practical considerations

    USGS Publications Warehouse

    Kirby, C.S.; Cravotta, C.A., III

    2005-01-01

    The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples. Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5-4) or near neutral (pH 6-7); ??? 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6. The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze. The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= -net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH < 6.3 after oxidation had positive Hot Acidity. Samples with similar pH values before oxidation had dissimilar Hot Acidities due to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. Hot Acidity was approximately equal to net acidity calculated based on initial pH and dissolved concentrations of Fe, Mn, and Al minus the

  6. Net alkalinity and net acidity 1: Theoretical considerations

    USGS Publications Warehouse

    Kirby, C.S.; Cravotta, C.A., III

    2005-01-01

    Net acidity and net alkalinity are widely used, poorly defined, and commonly misunderstood parameters for the characterization of mine drainage. The authors explain theoretical expressions of 3 types of alkalinity (caustic, phenolphthalein, and total) and acidity (mineral, CO2, and total). Except for rarely-invoked negative alkalinity, theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined "CO 2-acidity" is closely related to most standard titration methods with an endpoint pH of 8.3 used for determining acidity in mine drainage, but it is unfortunately named because CO2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/mass- action approach and employing graphs to illustrate speciation with changes in pH, the authors explore the concept of principal components and how to assign acidity contributions to aqueous species commonly present in mine drainage. Acidity is defined in mine drainage based on aqueous speciation at the sample pH and on the capacity of these species to undergo hydrolysis to pH 8.3. Application of this definition shows that the computed acidity in mg L -1 as CaCO3 (based on pH and analytical concentrations of dissolved FeII, FeIII, Mn, and Al in mg L -1):aciditycalculated=50{1000(10-pH)+[2(FeII)+3(FeIII)]/56+2(Mn)/ 55+3(Al)/27}underestimates contributions from HSO4- and H+, but overestimates the acidity due to Fe3+ and Al3+. However, these errors tend to approximately cancel each other. It is demonstrated that "net alkalinity" is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. Further, it is shown that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: (1) alkalinity and acidity values based on aqueous speciation, (2) measured alkalinity minus calculated acidity, or (3) taking the negative of the value obtained in a

  7. Experience of using heat citric acid disinfection method in central dialysis fluid delivery system.

    PubMed

    Sakuma, Koji; Uchiumi, Nobuko; Sato, Sumihiko; Aida, Nobuhiko; Ishimatsu, Taketo; Igoshi, Tadaaki; Kodama, Yoshihiro; Hotta, Hiroyuki

    2010-09-01

    We applied the heat citric acid disinfection method in the main part of the central dialysis fluid delivery system (MPCDDS), which consists of a multiple-patient dialysis fluid supply unit, dialysis console units, and dialysis fluid piping. This disinfection method has been used for single-patient dialysis machines, but this is the first trial in the MPCDDS. We examined, by points of safety and disinfection effect, whether this disinfection method is comparable to conventional disinfection methods in Japan. The conventional disinfection method is a combination of two disinfectants, sodium hypochlorite and acetic acid, used separately for protein removal and decalcification. Consequently, total microbial counts and endotoxin concentrations fully satisfied the microbiological requirements for standard dialysis fluid of ISO 11663. From our results and discussion, this heat citric acid disinfection method is proved to be safe and reliable for MPCDDS. However, to satisfy the microbiological requirements for ultrapure dialysis fluid, further consideration for this method in MPCDDS including the reverse osmosis device composition and piping is necessary. PMID:20514548

  8. EEG-assisted titration of propofol infusion during neuroanesthesia: effect of nitrous oxide.

    PubMed

    van Hemelrijck, J; Tempelhoff, R; White, P F; Jellish, W S

    1992-01-01

    Total intravenous anesthesia (TIVA) with propofol is an alternative to standard techniques for neuroanesthesia. The present study compared the hemodynamic and recovery profiles of 46 neurosurgical patients randomly assigned to one of three different anesthetic treatment groups. Group 1 was anesthetized with a TIVA technique in which propofol was titrated using an EEG-assisted quantification method. Group 2 received a similar propofol-based infusion technique in combination with nitrous oxide. Group 3 (control) received a standard anesthetic technique consisting of thiopental, nitrous oxide, fentanyl, and isoflurane. Significantly less propofol was required in group 2 than in group 1 (7.4 +/- 1.9 vs. 9.0 +/- 1.0 mg/kg/h, respectively). The propofol blood concentration at the first appearance of EEG burst suppression was also higher in group 1 compared to group 2 (5.8 +/- 1.1 vs. 4.8 +/- 0.8 microg/ml). However, 25% of the patients in group 2 were treated for hypotension after induction, compared to none in groups 1 and 3. Hypertensive episodes, on the other hand, were more frequent in groups 1 (43%) and 3 (31%) than in group 2 (12%). Time to awakening was significantly shorter in the control group (6 +/- 6 min) than in groups 1 (14 +/- 10 min) or 2 (12 +/- 16 min). In conclusion, titration of propofol to achieve a burst suppressive EEG pattern resulted in a slower emergence from anesthesia than a standard "balanced" technique. Use of nitrous oxide with propofol produced more hypotension during induction; however, its use improved hemodynamic stability during the maintenance period. PMID:15815432

  9. Comparison of methods of extracting messenger Ribonucleic Acid from ejaculated Porcine (Sus Scrofa) Spermatozoa

    Technology Transfer Automated Retrieval System (TEKTRAN)

    H. D. Guthrie, G.R. Welch, and L. A. Blomberg. Comparison of Methods of Extracting Messenger Ribonucleic Acid from Ejaculated Porcine (Sus Scrofa) Spermatozoa. Biotechnology and Germplasm Laboratory, Agricultural Research Service U. S. Department of Agriculture, Beltsville, MD 20705 The purpos...

  10. Method of dissolving metal oxides with di- or polyphosphonic acid and a redundant

    DOEpatents

    Horwitz, Earl P.; Chiarizia, Renato

    1996-01-01

    A method of dissolving metal oxides using a mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

  11. Nuclemeter: a reaction-diffusion based method for quantifying nucleic acids undergoing enzymatic amplification.

    PubMed

    Liu, Changchun; Sadik, Mohamed M; Mauk, Michael G; Edelstein, Paul H; Bushman, Frederic D; Gross, Robert; Bau, Haim H

    2014-01-01

    Real-time amplification and quantification of specific nucleic acid sequences plays a major role in medical and biotechnological applications. In the case of infectious diseases, such as HIV, quantification of the pathogen-load in patient specimens is critical to assess disease progression and effectiveness of drug therapy. Typically, nucleic acid quantification requires expensive instruments, such as real-time PCR machines, which are not appropriate for on-site use and for low-resource settings. This paper describes a simple, low-cost, reaction-diffusion based method for end-point quantification of target nucleic acids undergoing enzymatic amplification. The number of target molecules is inferred from the position of the reaction-diffusion front, analogous to reading temperature in a mercury thermometer. The method was tested for HIV viral load monitoring and performed on par with conventional benchtop methods. The proposed method is suitable for nucleic acid quantification at point of care, compatible with multiplexing and high-throughput processing, and can function instrument-free. PMID:25477046

  12. Pregabalin and Tranexamic Acid Evaluation by Two Simple and Sensitive Spectrophotometric Methods

    PubMed Central

    Sher, Nawab; Fatima, Nasreen; Perveen, Shahnaz; Siddiqui, Farhan Ahmed; Wafa Sial, Alisha

    2015-01-01

    This paper demonstrates colorimetric visible spectrophotometric quantification methods for amino acid, namely, tranexamic acid and pregabalin. Both drugs contain the amino group, and when they are reacted with 2,4-dinitrophenol and 2,4,6-trinitrophenol, they give rise to yellow colored complexes showing absorption maximum at 418 nm and 425 nm, respectively, based on the Lewis acid base reaction. Detailed optimization process and stoichiometric studies were conducted along with investigation of thermodynamic features, that is, association constant and standard free energy changes. The method was linear over the concentration range of 0.02–200 µgmL−1 with correlation coefficient of more than 0.9990 in all of the cases. Limit of detection was in range from 0.0041 to 0.0094 µgmL−1 and limit of quantification was in the range from 0.0137 to 0.0302 µgmL−1. Excellent recovery in Placebo spiked samples indicated that there is no interference from common excipients. The analytical methods under proposal were successfully applied to determine tranexamic acid and pregabalin in commercial products. t-test and F ratio were evaluated without noticeable difference between the proposed and reference methods. PMID:25873964

  13. FIELD COMPARISON OF METHODS FOR THE MEASUREMENT OF CONTRIBUTORS TO ACIDIC DRY DEPOSITION

    EPA Science Inventory

    A field study was conducted to compare methods for sampling and analysis of atmospheric constituents that are important contributors to acidic dry deposition. hree multicomponent samplers were used: the Canadian filter pack (FP), the annular denuder system (ADS), and the transiti...

  14. Chromatographic method for determination of the free amino acid content of chamomile flowers

    PubMed Central

    Ma, Xiaoli; Zhao, Dongsheng; Li, Xinxia; Meng, Lei

    2015-01-01

    Objective: To determine the free amino acid contents of chamomile flowers using reverse-phase high-performance column chromatography preceded by pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC), and to determine the reliability of this method. Materials and Methods: Derivatization with reconstituted AQC was used to prepare the samples and standards for injection into the chromatography column. The peaks were analyzed by fluorescence detection (λ excitation, 250 nm; λ emission, 395 nm. Results: Alanine, proline, and leucine were the most abundant amino acids, whereas tyrosine and methionine were the least abundant. The linearity of the method was found to be good with amino acid concentrations of 0.012-0.36 μM. The precision was 0.05-1.36%; average recovery, 91.12-129.41%; and limit of detection, 0.006-0.058 μM. Conclusion: The method is reliable for determining the free amino acid content of different types of chamomile flowers. PMID:25709230

  15. A validated method for gas chromatographic analysis of gamma-aminobutyric acid in tall fescue herbage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gamma-Aminobutyric acid (GABA) is an inhibitory neurotransmitter in animals that is also found in plants and has been associated with plant responses to stress. A simple and relatively rapid method of GABA separation and quantification was developed from a commercially available kit for serum amino...

  16. Study on synthetic methods of trialkyl phosphate oxide and its extraction behavior of some acids

    SciTech Connect

    Yu, M.J.; Su, Y.F.

    1987-01-01

    Trioctyl phosphine oxide (TOPO) is useful for the extraction of many inorganic and organic compounds. A mixed trialkyl phosphine oxide (TRPO) is similar in property to TOPO. The total number of carbon atoms per molecule of TRPO ranges from 15 to 27. Three methods for synthesizing TRPO are described in this paper. When TRPO is synthesized from an alcohol mixture it is significantly cheaper than a single pure alcohol as required for the production of TOPO; tedious purification steps are eliminated. TRPO is a brown liquid which is very slightly soluble in water. Toxicological measurements of LD50, AMES test, hereditary and accumulative toxicity show that TRPO is safe for use in the extraction of some pharmaceutical and biochemical compounds. Examinations of IR and NMR show that the complex interaction of P=O bond of TRPO with extracted substances is the same as that of TOPO. The distribution coefficients of phosphoric acid, citric acid, malic acid, oxalic acid, and tartaric acid with TRPO are reported. The extraction of these acids is believed to proceed by neutral-complex mechanism.

  17. Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro.

    PubMed

    Hannig, Christian; Hamkens, Arne; Becker, Klaus; Attin, Rengin; Attin, Thomas

    2005-06-01

    The present study intended to investigate minimal erosive effects of different acids on enamel during short time incubation via determination of calcium and phosphate dissolution. Bovine enamel specimens were eroded for 1-5 min with eight different acids of pH 2, 2.3 and 3 (citric (CA), maleic (MA), lactic (LA), tartaric (TA), phosphoric (PA), oxalic (OA), acetic (AA) and hydrochloric acid (HCl)). Calcium (Ca) and phosphate (P) release were determined photometrically using arsenazo III (calcium) and malachite green (phosphate) as substrates. Each subgroup contained eight enamel specimens. Amount of titratable acid was determined for all acidic solutions. MA, LA, TA, AA and HCl caused linear release of Ca and P, PA of Ca, CA of P. For CA, MA, LA, TA, AA, PA and HCl mineral loss was shown to be pH-dependent. Ca dissolution varied between 28.6+/-4.4 (LA, pH 2) and 2.4+/-0.7 nmol mm(-2)min(-1) (HCl, pH 3), P dissolution ranged between 17.2+/-2.6 (LA, pH 2) and 1.4+/-0.4 nmol mm(-2)min(-1) (HCl, pH 3). LA was one of the most erosive acids. AA was very erosive at pH 3. HCl and MA were shown to have the lowest erosive effects. There was only a weak correlation (r=0.28) between P and Ca release and the amount of titratable acid. The method of the present study allows investigation of minimal erosive effects via direct determination of P and Ca dissolution. During short time exposition at constant pH level, erosive effects mainly depend on pH and type of acid but not on amount of titratable acid. PMID:15848147

  18. Acid-base buffering of soils in transitional and transitional-accumulative positions of undisturbed southern-taiga landscapes

    NASA Astrophysics Data System (ADS)

    Rusakova, E. S.; Ishkova, I. V.; Tolpeshta, I. I.; Sokolova, T. A.

    2012-05-01

    The method of continuous potentiometric titration (CPT) of soil water suspensions was used to evaluate the acid-base buffering of samples from the major genetic horizons of podzolic soils on a slope and soddy gley soils on the adjacent floodplain of a rivulet. In the soils of the slope, the buffering to acid upon titration from the pH of the initial titration point (ITP) to pH 3 in all the horizons was 1.5-2.0 times lower than that in the podzolic soils of the leveled interfluve, which could be due to the active leaching of exchangeable bases and oxalate-soluble aluminum and iron compounds with the later soil flows. In the soddy gley soils, the buffering to acid in the mineral horizons was 2-10 times higher than that in the podzolic soils. A direct dependence of the soil buffering to acid on the total content of exchangeable bases and on the content of oxalate-soluble aluminum compounds was found. A direct dependence of the buffering to basic upon titration from the ITP to pH 10 on the contents of the oxalate-soluble aluminum and organic matter was observed in the mineral horizons of all the studied soils. The soil treatment with Tamm's reagent resulted in the decrease of the buffering to acid in the soddy gley soils of the floodplain, as well as in the decrease of the buffering to basic in the soils on the slopes and in the soddy gley soils. It was also found that the redistribution of the mobile aluminum compounds between the eluvial, transitional, and transitional-accumulative positions in the undisturbed southern taiga landscapes leads to significant spatial differentiation of the acid-base buffering of the mineral soil horizons with a considerable increase in the buffer capacity of the soils within the transitional-accumulative terrain positions.

  19. Online process control of acidic texturisation baths with ion chromatography.

    PubMed

    Zimmer, Martin; Oltersdorf, Antje; Rentsch, Jochen

    2009-12-15

    Etching of silicon with mixtures of hydrofluoric acid and nitric acid is a widely used process in silicon solar cell fabrication. One precondition for an optimized usage of the acidic etching baths is the exact knowledge of the chemical bath composition. In this paper, we investigated a fast and online-capable method for the total analysis of all bath constituents by ion chromatography. The chromatographical system consists of a low-volume injection valve, which injects the concentrated samples directly into the KOH-based eluent. After separation and detection of nitrate and fluoride, a post-column derivatization with sodium molybdate is applied to detect the hexafluorosilicic acid, which enriches in the texturisation bath during the etching process. The results of the presented approach are discussed and compared with already published chromatographical and titration methods found in literature. PMID:19836511

  20. Effect of Different Cooking Methods on the Composition of Intramuscular Fatty Acids of Hyla Rabbit.

    PubMed

    Xue, Shan; Xiao, Xia; He, Zhifei; Li, Hongjun

    2016-01-01

    The influence of three cooking methods (stewing, microwaving and Aluminium (Al) foil-baking) was evaluated on the content of intramuscular lipid and the composition of intramuscular fatty acids of Hyla rabbit. The percentage of intramuscular lipid in cooked-longissimus dorsi (LD) (dry weight %) were in the order mentioned below: microwaving > foil-baking > stewing. All treated samples showed decrease in the proportion of polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA), whilst increase in the proportion of saturated (SFA) and n-6/n-3 value during processing. All of the cooked samples had the n-6/n-3 ratio within the recommended range (5-10). By the analysis of partial least squares regression (PLSR), the microwaving treatment was better to keep the stability of unsaturated fatty acids (UFA), whilst the long-time Al foil-baking did the most serious damage to UFA, especially the PUFA. In addition, the heating method showed greater influence on the samples than the processing time. The shorter processing time was better to retain the intramuscular PUFA of Hyla rabbit, especially the LC-PUFAs (C20-22). Considering all the factors, microwaving showed the superiority in reserving the composition of intramuscular fatty acids of Hyla rabbit. PMID:27194925

  1. Effect of Different Cooking Methods on the Composition of Intramuscular Fatty Acids of Hyla Rabbit

    PubMed Central

    Xue, Shan; Xiao, Xia; He, Zhifei; Li, Hongjun

    2016-01-01

    The influence of three cooking methods (stewing, microwaving and Aluminium (Al) foil-baking) was evaluated on the content of intramuscular lipid and the composition of intramuscular fatty acids of Hyla rabbit. The percentage of intramuscular lipid in cooked-longissimus dorsi (LD) (dry weight %) were in the order mentioned below: microwaving > foil-baking > stewing. All treated samples showed decrease in the proportion of polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA), whilst increase in the proportion of saturated (SFA) and n-6/n-3 value during processing. All of the cooked samples had the n-6/n-3 ratio within the recommended range (5-10). By the analysis of partial least squares regression (PLSR), the microwaving treatment was better to keep the stability of unsaturated fatty acids (UFA), whilst the long-time Al foil-baking did the most serious damage to UFA, especially the PUFA. In addition, the heating method showed greater influence on the samples than the processing time. The shorter processing time was better to retain the intramuscular PUFA of Hyla rabbit, especially the LC-PUFAs (C20-22). Considering all the factors, microwaving showed the superiority in reserving the composition of intramuscular fatty acids of Hyla rabbit. PMID:27194925

  2. Preparation method and stability of ellagic acid-rich pomegranate fruit peel extract.

    PubMed

    Panichayupakaranant, Pharkphoom; Itsuriya, Atcharaporn; Sirikatitham, Anusak

    2010-02-01

    A simple one-step purification using liquid-liquid extraction for preparing pomegranate peel extract rich in ellagic acid has been demonstrated. The method involved partitioning of the 10% v/v water in methanol extract of pomegranate peel between ethyl acetate and 2% aqueous acetic acid. This method was capable of increasing the ellagic acid content of the extract from 7.06% to 13.63% w/w. Moreover, the antioxidant activity of the extract evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay was also increased (ED(50) from 38.21 to 14.91 micro/mL). Stability evaluations of the ellagic acid-rich pomegranate peel extract in several conditions through a period of four months found that the extracts were stable either kept under light or protected from light. The extracts were also stable under 4 degrees +/- 2 degrees C, 30 degrees +/- 2 degrees C and accelerated conditions at 45 degrees C with 75% relative humidity. However, study on the effect of pH on stability of the extract in the form of solution revealed that the extract was not stable in all tested pH (5.5, 7 and 8). These results indicated that the ellagic acid-rich pomegranate peel extract was stable when it was kept as dried powder, but it was not stable in any aqueous solution. PMID:20645841

  3. Liposome/Graphene Oxide Interaction Studied by Isothermal Titration Calorimetry.

    PubMed

    Huang, Po-Jung Jimmy; Wang, Feng; Liu, Juewen

    2016-03-15

    The interaction between graphene oxide (GO) and lipid bilayers is important for fundamental surface science and many applications. In this work, isothermal titration calorimetry (ITC), cryo-TEM, and fluorescence spectroscopy were used to study the adsorption of three types of liposomes. Heat release was observed when GO was mixed with zwitterionic DOPC liposomes, while heat absorption occurred with cationic DOTAP liposomes. For comparison, anionic DOPG liposomes released heat when mixed with DOTAP. DOPC was adsorbed as intact liposomes, but DOTAP ruptured and induced stacking and folding of GO sheets. This study suggests the release of more water molecules from the GO surface when mixed with DOTAP liposomes. This can be rationalized by the full rupture of the DOTAP liposomes interacting with the whole GO surface, including hydrophobic regions, while DOPC liposomes only interact with a small area on GO near the edge, which is likely to be more hydrophilic. This interesting biointerfacial observation has enhanced our fundamental understanding of lipid/GO interactions. PMID:26908113

  4. Development of a gas phase source for perfluoroalkyl acids to examine atmospheric sampling methods.

    PubMed

    MacInnis, John J; VandenBoer, Trevor C; Young, Cora J

    2016-06-21

    An inability to produce environmentally relevant gaseous mixing ratios of perfluoroalkyl acids (PFAAs), ubiquitous global contaminants, limits the analytical reliability of atmospheric chemists to make accurate gas and particulate measurements that are demonstrably free of interferences due to sampling artefacts. A gas phase source for PFAAs based on the acid displacement mechanism using perfluoropropionate (PFPrA), perfluorobutanoate (PFBA), perfluorohexanoate (PFHxA), and perfluorooctanoate (PFOA) has been constructed. The displacement efficiency of gas phase perfluorocarboxylic acids (PFCAs) is inversely related to chain length. Decreasing displacement efficiencies for PFPrA, PFBA, PFHxA, and PFOA were 90% ± 20%, 40% ± 10%, 40% ± 10%, 9% ± 4%, respectively. Generating detectable amounts of gas phase perfluorosulfonic acids (PFSAs) was not possible. It is likely that lower vapour pressure and much higher acidity play a role in this lack of emission. PFCA emission rates were not elevated by increasing relative humidity (25%-75%), nor flow rate of carrier gas from 33-111 sccm. Overall, reproducible gaseous production of PFCAs was within the error of the production of hydrochloric acid (HCl) as a displacing acid (±20%) and was accomplished using a dry nitrogen flow of 33 ± 2 sccm. A reproducible mass emission rate of 0.97 ± 0.10 ng min(-1) (n = 8) was observed for PFBA. This is equivalent to an atmospheric mixing ratio of 12 ppmv, which is easily diluted to environmentally relevant mixing ratios of PFBA. Conversely, generating gas phase perfluorononanoic acid (PFNA) by sublimating the solid acid under the same conditions produced a mass emission rate of 2800 ng min(-1), which is equivalent to a mixing ratio of 18 ppthv and over a million times higher than suspected atmospheric levels. Thus, for analytical certification of atmospheric sampling methods, generating gas phase standards for PFCAs is best accomplished using acid displacement under dry conditions

  5. Spectrophotometric methods for simultaneous determination of betamethasone valerate and fusidic acid in their binary mixture

    NASA Astrophysics Data System (ADS)

    Lotfy, Hayam Mahmoud; Salem, Hesham; Abdelkawy, Mohammad; Samir, Ahmed

    2015-04-01

    Five spectrophotometric methods were successfully developed and validated for the determination of betamethasone valerate and fusidic acid in their binary mixture. Those methods are isoabsorptive point method combined with the first derivative (ISO Point - D1) and the recently developed and well established methods namely ratio difference (RD) and constant center coupled with spectrum subtraction (CC) methods, in addition to derivative ratio (1DD) and mean centering of ratio spectra (MCR). New enrichment technique called spectrum addition technique was used instead of traditional spiking technique. The proposed spectrophotometric procedures do not require any separation steps. Accuracy, precision and linearity ranges of the proposed methods were determined and the specificity was assessed by analyzing synthetic mixtures of both drugs. They were applied to their pharmaceutical formulation and the results obtained were statistically compared to that of official methods. The statistical comparison showed that there is no significant difference between the proposed methods and the official ones regarding both accuracy and precision.

  6. New methods for the compound specific analysis of underivatized amino acids

    NASA Astrophysics Data System (ADS)

    McCullagh, J.

    2012-04-01

    The isotopic analysis of amino acids has become an important area of application in a range of geoscientific, palaeo-ecological and biochemical disciplines including in particular palaeodietary reconstruction and environmental forensics (Dunn et al., 2011; Raghaven et al., 2010; Lynch et al., 2011; Godin and McCullagh, 2011). Commercialisation of an interface between liquid chromatography and isotope ratio mass spectrometry in 2004 has enabled the analysis of non-volatile, soluble compounds without the need for derivatization (via GC-C-IRMS), providing exciting new analytical possibilities (Krummen et al., 2004). One of the major problems facing LC-IRMS for δ13C analysis is the development of efficient and robust methods. Chromatographic restrictions on mobile phase composition and flow rates, combined with the need for baseline resolution, are analytically challenging but imperative for accurate isotopic analysis. Since the introduction of LC-IRMS a number of research groups have been working on separation methods in particular but, although suitable for resolving the majority of amino acids, current protocols are extremely time consuming, with recently published methods taking over 4 hours per sample (Smith et al., 2009). The low sample throughput of these methods is directly affecting research efficiency. For example, we are currently trying to better understand what palaeodietary information is represented by individual amino acid δ13C values from bone collagen and hair keratin, and this work has been significantly hampered by a lack of sample throughput. Recognizing the need for larger sample sets to better understanding biogenic information represented by amino acid δ13C for palaeodietary reconstruction, high throughput approaches to amino acid LC-IRMS have been investigated and developed. This poster will present unpublished research, developing an analytical protocol which cuts analysis time for amino acids dramatically. This approach is based on mixed

  7. Surface and catalytic properties of acid metal carbons prepared by the sol gel method

    NASA Astrophysics Data System (ADS)

    Aguado-Serrano, J.; Rojas-Cervantes, M. L.; Martín-Aranda, R. M.; López-Peinado, A. J.; Gómez-Serrano, V.

    2006-06-01

    The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones.

  8. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

    SciTech Connect

    Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

    2004-01-03

    The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

  9. Barium hydroxyapatite nanoparticles synthesized by citric acid sol-gel combustion method

    SciTech Connect

    Xiu Zhiliang; Lue Mengkai . E-mail: mklu@icm.sdu.edu.cn; Liu Suwen; Zhou Guangjun; Su Benyu; Zhang Haiping

    2005-09-01

    Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant at a relatively low temperature of 600 deg. C. The thermal decomposition of nitrate-citrate xerogel was investigated by thermogravimetric/differential thermal analysis (TG/DTA) technique. The yielding powders calcined at 600 deg. C have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The possible combustion process was presented.

  10. Effect of Hyaluronic Acid Incorporation Method on the Stability and Biological Properties of Polyurethane-Hyaluronic Acid Biomaterials

    PubMed Central

    Ruiz, Amaliris; Rathnam, Kashmila R.; Masters, Kristyn S.

    2014-01-01

    The high failure rate of small diameter vascular grafts continues to drive the development of new materials and modification strategies that address this clinical problem, with biomolecule incorporation typically achieved via surface-based modification of various biomaterials. In this work, we examined whether the method of biomolecule incorporation (i.e., bulk vs. surface modification) into a polyurethane (PU) polymer impacted biomaterial performance in the context of vascular applications. Specifically, hyaluronic acid (HA) was incorporated into a poly(ether urethane) via bulk copolymerization or covalent surface tethering, and the resulting PU-HA materials characterized with respect to both physical and biological properties. Modification of PU with HA by either surface or bulk methods yielded materials that, when tested under static conditions, possessed no significant differences in their ability to resist protein adsorption, platelet adhesion, and bacterial adhesion, while supporting endothelial cell culture. However, only bulk-modified PU-HA materials were able to fully retain these characteristics following material exposure to flow, demonstrating a superior ability to retain the incorporated HA and minimize enzymatic degradation, protein adsorption, platelet adhesion, and bacterial adhesion. Thus, despite bulk methods rarely being implemented in the context of biomolecule attachment, these results demonstrate improved performance of PU-HA upon bulk, rather than surface, incorporation of HA. Although explored only in the context of PU-HA, the findings revealed by these experiments have broader implications for the design and evaluation of vascular graft modification strategies. PMID:24276670

  11. A 24-Week, Randomized, Controlled Study to Evaluate the Tolerability, Safety and Efficacy of 2 Different Titration Schemes of the Rivastigmine Patch in Japanese Patients with Mild to Moderate Alzheimer's Disease

    PubMed Central

    Nakamura, Yu; Strohmaier, Christine; Tamura, Kaoru; Kataoka, Naoko; Nakano, Masayuki; Oda, Shoichiro; Nishimura, Kazuma; Homma, Akira

    2015-01-01

    Aim To investigate whether 1-step titration of the rivastigmine patch (initiated at 5 cm2 and titrated to 10 cm2 after 4 weeks) is well tolerated in Japanese patients with Alzheimer's disease (AD) as compared to 3-step titration (initiated at 2.5 cm2 and titrated by 2.5 cm2 every 4 weeks to 10 cm2). Methods A 24-week, multicenter, randomized, double-blind study was conducted in Japan between July 2012 and May 2014. Patients with mild to moderate AD aged 50-85 years were randomized 1:1 to 1-step or 3-step titration of the rivastigmine once-daily patch. The primary endpoint was the proportion of patients with adverse events leading to discontinuation. Results Of 216 patients randomized, 215 (1-step, n = 107; 3-step, n = 108) were included in the safety analysis. The primary endpoint outcome was 15.0% in the 1-step group and 18.5% in the 3-step group. The observed treatment difference was −3.6% (95% confidence interval: −17.0, 9.6), falling within the prespecified acceptance range. Conclusion The tolerability of two different titration schemes was similar in Japanese patients with AD. PMID:26557135

  12. Method of testing the penetration of acid solutions through safety gloves.

    PubMed

    Liwkowicz, J; Kowalska, J

    2000-01-01

    Because they cause burns that are difficult to heal, acids are dangerous, and steps should be taken to ensure that the human skin does not come into contact with them. For this purpose safety gloves are generally used by workers who have to handle acids. Such gloves need to be tested to ensure that they are acid resistant. Standard EN 374 (European Committee for Standardization [CEN], 1993c) specifies a method of testing the permeation of liquid chemicals, on a molecular level, through glove material, but it may be difficult to ensure the fitness of the joints of a two-compartment cell, when gloves are lined with jersey. To deal with this a simple pH-meter method to test the permeation of acid and alkali solutions through safety gloves has been developed. The permeation of H&inf2;SO&inf4;, HCl, HNO&inf3;, and CH&inf3;COOH through gloves made from neoprene, nitrile, and PVC was tested. This method seems to be simple and economical. PMID:10773891

  13. Ensemble Methods for Monitoring Enzyme Translocation along Single Stranded Nucleic Acids

    PubMed Central

    Tomko, Eric J.; Fischer, Christopher J.; Lohman, Timothy M.

    2010-01-01

    We review transient kinetic methods developed to study the mechanism of translocation of nucleic acid motor proteins. One useful stopped-flow fluorescence method monitors arrival of the translocase at the end of a fluorescently labeled nucleic acid. When conducted under single-round conditions the time courses can be analyzed quantitatively using n-step sequential models to determine the kinetic parameters for translocation (rate, kinetic step size and processivity). The assay and analysis discussed here can be used to study enzyme translocation along a linear lattice such as ssDNA or ssRNA. We outline the methods for experimental design and two approaches, along with their limitations, that can be used to analyze the time courses. Analysis of the full time courses using n-step sequential models always yields an accurate estimate of the translocation rate. An alternative semi-quantitative “time to peak” analysis yields accurate estimates of translocation rates only if the enzyme initiates translocation from a unique site on the nucleic acid. However, if initiation occurs at random sites along the nucleic acid, then the “time to peak” analysis can yield inaccurate estimates of even the rates of translocation depending on the values of other kinetic parameters, especially the rate of dissociation of the translocase. Thus, in those cases analysis of the full time course is needed to obtain accurate estimates of translocation rates. PMID:20371288

  14. The Mobile Insulin Titration Intervention (MITI) for Insulin Adjustment in an Urban, Low-Income Population: Randomized Controlled Trial

    PubMed Central

    Levy, Natalie; Nilo, Annielyn; Singer, Karyn; Bernik, Lidia S; Etiebet, Mary-Ann; Fang, Yixin; Cho, James; Natarajan, Sundar

    2015-01-01

    Background Diabetes patients are usually started on a low dose of insulin and their dose is adjusted or “titrated” according to their blood glucose levels. Insulin titration administered through face-to-face visits with a clinician can be time consuming and logistically burdensome for patients, especially those of low socioeconomic status (SES). Given the wide use of mobile phones among this population, there is the potential to use short message service (SMS) text messaging and phone calls to perform insulin titration remotely. Objective The goals of this pilot study were to (1) evaluate if our Mobile Insulin Titration Intervention (MITI) intervention using text messaging and phone calls was effective in helping patients reach their optimal insulin glargine dose within 12 weeks, (2) assess the feasibility of the intervention within our clinic setting and patient population, (3) collect data on the cost savings associated with the intervention, and (4) measure patient satisfaction with the intervention. Methods This was a pilot study evaluating an intervention for patients requiring insulin glargine titration in the outpatient medical clinic of Bellevue Hospital Center in New York City. Patients in the intervention arm received weekday SMS text messages from a health management platform requesting their fasting blood glucose values. The clinic’s diabetes nurse educator monitored the texted responses on the platform website each weekday for alarm values. Once a week, the nurse reviewed the glucose values, consulted the MITI titration algorithm, and called patients to adjust their insulin dose. Patients in the usual care arm continued to receive their standard clinic care for insulin titration. The primary outcome was whether a patient reached his/her optimal insulin glargine dose within 12 weeks. Results A total of 61 patients consented and were randomized into the study. A significantly greater proportion of patients in the intervention arm reached their

  15. Synthesis of a ruthenium(II) bipyridyl complex coordinated by a functionalized Schiff base ligand: characterization, spectroscopic and isothermal titration calorimetry measurements of M2+ binding and sensing (M2+=Ca2+, Mg2+).

    PubMed

    Dixit, Namrata; Mishra, Lallan; Mustafi, Sourajit M; Chary, Kandala V R; Houjou, Hirohiko

    2009-07-01

    Bis-[methylsalicylidine-4'benzoic acid]-ethylene (LH2) complexed with cis-Ru(bpy)2Cl(2).2H2O provides a complex of composition [Ru(bpy)2L].2NH4PF6 (1), which has been characterized spectroscopically. Its binding behaviour towards Mg2+ and Ca2+ ions is monitored using 1H NMR titration, isothermal titration calorimetry (ITC) and luminescence microscopy. The luminescent ruthenium complex binds Ca2+ in a more selective manner as compared to Mg2+. PMID:19230747

  16. Amino acid profiling as a method of discovering biomarkers for early diagnosis of cancer.

    PubMed

    Simińska, Edyta; Koba, Marcin

    2016-06-01

    Cancer is one of the main causes of mortality in the world and its early detection significantly increases chances of patients' survival. High cancer mortality rate is caused mainly by late-stage diagnosis and lack of non-invasive and reliable methods for early diagnosis, such as plasma biomarkers. The incidence of cancers in the world still grows so it is crucial to develop a new, faster, high specificity and more sensitive diagnostic technologies. Several recent researchers indicate amino acids as a potential marker for cancer detection. An ideal cancer biomarker should be characterized by high specificity and sensitivity, reliability, ease of measurement and, what is important, ability to detect disease in its early stage. This study is focused on indicating metabolic amino acid profiling as a method of identifying biomarkers for cancer early detection and screening. Presented results are derived from the most recent studies where patients in early, often asymptomatic stages of disease constituted a large percentage of all the patients and, what is important, where researchers have observed alterations in these patients' amino acid profiles. This review is concentrated on analyzing studies on the most common cancers with high mortality rate. Inventing effective methods of early diagnosis is particularly important in case of such diseases. Research presented in this publication is focused on patients with lung, breast and colon cancer. In all analyzed cases, significant changes in the amino acid profile in cancer patients comparing to healthy controls were observed. This study indicates potential of amino acid profiling as method for early cancer detection. PMID:27033065

  17. SPECTRAL REFLECTANCE METHOD TO MEASURE ACID DEPOSITION EFFECTS ON BUILDING STONE.

    USGS Publications Warehouse

    Kingston, Marguerite J.; Ager, Cathy M.

    1985-01-01

    As part of the National Acid Precipitation Assessment Program (NAPAP), the U. S. Geological Survey is cooperating with other agencies to test the effects of acid deposition on building stone. A 10-year test-site study has been organized for the purpose of correlating possible stone deterioration with environmental factors. In Summer 1984, slabs of building stone, 3 by 2 by 2 inches, were exposed to the atmosphere at four test sites where the pH of precipitation and other meteorological variables are continuously monitored. This paper examines the development of one experimental technique used in this study - the application of diffuse spectral reflectance methods for laboratory and in situ measurement of those properties of stone which may be affected by acid deposition.

  18. A direct RP-HPLC method for the determination of furanic aldehydes and acids in honey.

    PubMed

    Spano, Nadia; Ciulu, Marco; Floris, Ignazio; Panzanelli, Angelo; Pilo, Maria I; Piu, Paola C; Salis, Severyn; Sanna, Gavino

    2009-04-15

    In this study 5-hydroxymethyl-2-furaldehyde (HMF), 2-furaldehyde, 3-furaldehyde, 2-furoic acid and 3-furoic acid are contemporarily determined in honey using a swift and direct RP-HPLC approach. The validation protocol was performed in terms of detection and quantification limits, precision (by repeatability and reproducibility), linearity and accuracy (by recovery tests); the acceptability of the precision and accuracy results was positively verified using Horwitz's model and AOAC guidelines, respectively. The method was tested on 18 honey samples of different ages, and botanical and geographical origin. HMF and 2-furaldehyde correlated highly with the age of the samples, whereas no correlation was observed with regards to 2-furaldehyde and 2-furoic acid. Hypotheses relating to the formation of minority furanic compounds are also proposed. PMID:19174244

  19. Quantitative and discriminative analysis of nucleic acid samples using luminometric nonspecific nanoparticle methods

    NASA Astrophysics Data System (ADS)

    Pihlasalo, S.; Mariani, L.; Härmä, H.

    2016-03-01

    Homogeneous simple assays utilizing luminescence quenching and time-resolved luminescence resonance energy transfer (TR-LRET) were developed for the quantification of nucleic acids without sequence information. Nucleic acids prevent the adsorption of a protein to europium nanoparticles which is detected as a luminescence quenching of europium nanoparticles with a soluble quencher or as a decrease of TR-LRET from europium nanoparticles to the acceptor dye. Contrary to the existing methods based on fluorescent dye binding to nucleic acids, equal sensitivities for both single- (ssDNA) and double-stranded DNA (dsDNA) were measured and a detection limit of 60 pg was calculated for the quenching assay. The average coefficient of variation was 5% for the quenching assay and 8% for the TR-LRET assay. The TR-LRET assay was also combined with a nucleic acid dye selective to dsDNA in a single tube assay to measure the total concentration of DNA and the ratio of ssDNA and dsDNA in the mixture. To our knowledge, such a multiplexed assay is not accomplished with commercially available assays.Homogeneous simple assays utilizing luminescence quenching and time-resolved luminescence resonance energy transfer (TR-LRET) were developed for the quantification of nucleic acids without sequence information. Nucleic acids prevent the adsorption of a protein to europium nanoparticles which is detected as a luminescence quenching of europium nanoparticles with a soluble quencher or as a decrease of TR-LRET from europium nanoparticles to the acceptor dye. Contrary to the existing methods based on fluorescent dye binding to nucleic acids, equal sensitivities for both single- (ssDNA) and double-stranded DNA (dsDNA) were measured and a detection limit of 60 pg was calculated for the quenching assay. The average coefficient of variation was 5% for the quenching assay and 8% for the TR-LRET assay. The TR-LRET assay was also combined with a nucleic acid dye selective to dsDNA in a single tube

  20. Application of isothermal titration calorimetry as a tool to study natural product interactions.

    PubMed

    Callies, O; Hernández Daranas, A

    2016-07-28

    Covering: up to February 2015Over the past twenty-five years, isothermal titration calorimetry (ITC) has become a potent tool for the study a great variety of molecular interactions. This technique is able to provide a complete thermodynamic profile of an interaction process in a single experiment, with a series of advantages in comparison to other comparable techniques, such as less amount of sample or no need of chemical modification or labelling. It is thus not surprising that ITC has been applied to study the manifold types of interactions of natural products to get new insights into the molecular key factors implied in the complexation process of this type of compounds. This review provides an overview over the applications of ITC as a potent tool to investigate interactions of natural products with proteins, nucleic acids, oligosaccharides, and other types of receptors. The examples have been selected depending on the impact that this technique had during the investigation and revision of the interactions involved in the bioactivity of a compound, lead optimization or technical applications. PMID:27186603