Isolement et caractérisation de deux subunites constitutives des glycoproteines de structure du tissu sous cutané de lapin.

PubMed

Randoux, A; CornilletStoupy, J; Desanti, M; Borel, J P

1976-09-28

Structural glycoproteins have been extracted by 8 M ureau from the insoluble residue remaining after collagenase digestion of rabbit dermis and purified by Sepharose 4 B chromatography. After reduction and alkylation, Dowex 1 x 2 chromatography allowed separation of two structural glycoproteins (D1 and D2) in an homogenous state as shown by chromatographic and electrophoretic behaviour as well as N terminal amino acid determination. These two glycoproteins have a molecular weight of about 16 000. Their amino acid compositions (very similar), are characterized by a high level of dicarboxylic amino acids and the absence of hydroxyproline and hydroxylysine. The less acidic glycoprotein (D1) has glycine for N terminal amino acid and contains 10.4 percent of bound carbohydrates. The glycoprotein D2 contains 5.1 percent of bound carbohydrates and its N terminal amino acid is glutamic acid.

Asparate Transcarbamylase Activity in Etiolated Cowpea Hypocotyls Treated with 2,4-Dichlorophenoxyacetic Acid 1

PubMed Central

Johnson, Lowell B.; Niblett, C. L.; Shively, O. D.

1973-01-01

Treating etiolated cowpea (Vigna unguiculata) seedlings with 2,4-dichlorophenoxyacetic acid resulted in 2.5-, 3.9-, and 6.5-fold increases in DNA, soluble protein, and RNA, respectively, over untreated controls 84 hours after treatment. Aspartate transcarbamylase activity increased within 12 hours after treatment, and by 84 hours it was almost 12-fold greater than that in the untreated controls. During that time, activity in untreated controls dropped 60%. The assay used 14C-aspartate, which was then separated from the 14C-ureidosuccinate product by Dowex 50 (H+ form) column chromatography. Thin layer chromatography of the reaction product indicated that most of the carbamyl-phosphate-dependent radioactivity co-chromatographed with ureidosuccinate. The reaction has a pH optimum near 10.0 and is inhibited by uridine 5′-phosphate and succinate. The data suggest that aspartate transcarbamylase is important in pyrimidine biosynthesis in 2,4-dichlorophenoxyacetic acid-treated seedlings. PMID:16658322

Separation of arsenic(III) and arsenic(V) in ground waters by ion-exchange

USGS Publications Warehouse

Ficklin, W.H.

1983-01-01

The predominant species of arsenic in ground water are probably arsenite and arsenate. These can be separated with a strong anion-exchange resin (Dowex 1 ?? 8; 100-200 mesh, acetate form) in a 10 cm ?? 7 mm column. Samples are filtered and acidified with concentrated hydrochloric acid (1 ml per 100 ml of sample) at the sample site. Five ml of the acidified sample are used for the separation. At this acidity, As(III) passes through the acetate-form resin, and As(V) is retained. As(V) is eluted by passage of 0.12M hydrochloric acid through the column (resulting in conversion of the resin back into the chloride form). Samples are collected in 5-ml portions up to a total of 20 ml. The arsenic concentration in each portion is determined by graphite-furnace atomic-absorption spectrophotometry. The first two fractions give the As(III) concentration and the last two the As(V) concentration. The detection limit for the concentration of each species is 1 ??g l. ?? 1983.

Determination of monosaccharides and sugar alcohols in tissues from diabetic rats by high-performance liquid chromatography with pulsed amperometric detection.

PubMed

Tomiya, N; Suzuki, T; Awaya, J; Mizuno, K; Matsubara, A; Nakano, K; Kurono, M

1992-10-01

A sensitive and simple high-performance liquid chromatographic method has been developed to determine the concentration of monosaccharides and sugar alcohols in animal tissues. Five neutral monosaccharides (D-glucose, D-galactose, D-mannose, D-fructose, and D-ribose) and three neutral sugar alcohols (myo-inositol, glycerol, and D-sorbitol) predominate in the renal cortices and sciatic nerves of rats. These monosaccharides and sugar alcohols were extracted with distilled water, purified by deproteinization with ethanol, a Sep-Pak C18 cartridge, and columns of Dowex 50W-X8 and Amberlite CG-400, then separated on Ca2+ and Pb2+ cation-exchange columns, eluted with deionized distilled water at 80 degrees C, and detected using integrated pulsed amperometry. About 10 pmol of each sugar was detectable with a signal-to-noise ratio of 10:1. D-Glucose, D-fructose, D-sorbitol, and D-mannose were higher in both the renal and sciatic tissues of diabetic rats than in those of normal animals. D-Ribose and glycerol were higher in the renal cortex of diabetic animals.

Utility of solid phase spectrophotometry for the modified determination of trace amounts of cadmium in food samples.

PubMed

Amin, Alaa S; Gouda, Ayman A

2012-05-01

A modified selective, highly sensitive and accurate procedure for the determination of trace amounts of cadmium which reacts with 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (BTAHNA) to give a deep violet complex with high molar absorptivity (7.05×10(6)Lmol(-1) cm(-1), 3.92×10(7)Lmol(-1)cm(-1), 1.78×10(8)Lmol(-1)cm(-1), and 4.10×10(8)Lmol(-1)cm(-1)), fixed on a Dowex 1-X8 type anion-exchange resin for 10mL, 100mL, 500mL, and 1000mL, respectively. Calibration is linear over the range 0.2-3.5μgL(-1) with RSD of ⩽1.14% (n=10). The detection and quantification limits were calculated. Increasing the sample volume can enhance the sensitivity. The method has been successfully applied for the determination of Cd(II) in food samples, water samples and some salts samples without interfering effect of various cations and anions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Mercury(II) and methyl mercury determinations in water and fish samples by using solid phase extraction and cold vapour atomic absorption spectrometry combination.

PubMed

Tuzen, Mustafa; Karaman, Isa; Citak, Demirhan; Soylak, Mustafa

2009-07-01

A method has been developed for mercury(II) and methyl mercury speciation on Staphylococcus aureus loaded Dowex Optipore V-493 micro-column in the presented work, by using cold vapour atomic absorption spectrometry. Selective and sequential elution with 0.1 molL(-1) HCl for methyl mercury and 2 molL(-1) HCl for mercury(II) were performed at the pH range of 2-6. Optimal analytical conditions including pH, amounts of biosorbent, sample volumes were investigated. The detection limits of the analytes were 2.5 ngL(-1) for Hg(II) and 1.7 ngL(-1) for methyl mercury. The capacity of biosorbent for mercury(II) and methyl mercury was 6.5 and 5.4 mgg(-1), respectively. The validation of the presented procedure is performed by the analysis of standard reference material. The speciation procedure established was successfully applied to the speciation of mercury(II) and methyl mercury in natural water and microwave digested fish samples.

An integrated scheme for the simultaneous determination of biogenic amines, precursor amino acids, and related metabolites by liquid chromatography with electrochemical detection.

PubMed

Oka, K; Kojima, K; Togari, A; Nagatsu, T; Kiss, B

1984-06-08

A new method using high-performance liquid chromatography with electrochemical detection (HPLC-ED) for the simultaneous determination of monoamines, their precursor amino acids, and related major metabolites in small samples of brain tissue weighing from 0.5 to 50 mg is described. The method is based on the preliminary isolation of monoamines (dopamine, norepinephrine, epinephrine, and serotonin), their precursor amino acids (tyrosine, 3,4-dihydroxyphenylalanine, tryptophan and 5-hydroxytryptophan), and their major metabolites (3-methoxytyramine, normetanephrine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, vanillylmandelic acid, 3-methoxy-4-hydroxyphenylethyleneglycol, and 5-hydroxyindoleacetic acid) by chromatography on small columns of Amberlite CG-50 and Dowex 50W, and by ethyl acetate extraction. All the compounds in the four isolated fractions were measured by HPLC-ED on a reversed-phase column under four different conditions. The sensitivity was from 0.1 to 40 pmol, depending on the substances analysed. This newly established method was applied to the study of the effects of an aromatic L-amino acid decarboxylase inhibitor (NSD-1015) and a monoamine oxidase inhibitor (pargyline) on the levels of monoamines, their precursor amino acids and their major metabolites in brain regions of mice.

[Determination of 235U/238U isotope ratios in camphor tree bark samples by MC-ICP-MS after separation of uranium from matrix elements].

PubMed

Wang, Xiao-Ping; Zhang, Ji-Long

2007-07-01

Twelve camphor (cinnamomum camphora) tree bark samples were collected from Hiroshima and Kyoto, and the matrix element composition and morphology of the outer surface of these camphor tree bark samples were studied by EDXS and SEM respectively. After a dry decomposition, DOWEX 1-X8 anion exchange resin was used to separate uranium from matrix elements in these camphor tree bark samples. Finally, 235U/238 U isotope ratios in purified uranium solutions were determined by MC-ICP-MS. It was demonstrated that the outer surface of these camphor tree bark samples is porous and rough, with Al, Ca, Fe, K, Mg, Si, C, O and S as its matrix element composition. Uranium in these camphor tree bark samples can be efficiently separated and quantitatively recovered from the matrix element composition. Compared with those collected from Kyoto, the camphor tree bark samples collected from Hiroshima have significantly higher uranium contents, which may be due to the increased aerosol mass concentration during the city reconstruction. Moreover, the 235 U/23.U isotope ratios in a few camphor tree bark samples collected from Hiroshima are slightly higher than 0.007 25.

A preconcentration system for determination of copper and nickel in water and food samples employing flame atomic absorption spectrometry.

PubMed

Tuzen, Mustafa; Soylak, Mustafa; Citak, Demirhan; Ferreira, Hadla S; Korn, Maria G A; Bezerra, Marcos A

2009-03-15

A separation/preconcentration procedure using solid phase extraction has been proposed for the flame atomic absorption spectrometric determination of copper and nickel at trace level in food samples. The solid phase is Dowex Optipore SD-2 resin contained on a minicolumn, where analyte ions are sorbed as 5-methyl-4-(2-thiazolylazo) resorcinol chelates. After elution using 1 mol L(-1) nitric acid solution, the analytes are determinate employing flame atomic absorption spectrometry. The optimization step was performed using a full two-level factorial design and the variables studied were: pH, reagent concentration (RC) and amount of resin on the column (AR). Under the experimental conditions established in the optimization step, the procedure allows the determination of copper and nickel with limit of detection of 1.03 and 1.90 microg L(-1), respectively and precision of 7 and 8%, for concentrations of copper and nickel of 200 microg L(-1). The effect of matrix ions was also evaluated. The accuracy was confirmed by analyzing of the followings certified reference materials: NIST SRM 1515 Apple leaves and GBW 07603 Aquatic and Terrestrial Biological Products. The developed method was successfully applied for the determination of copper and nickel in real samples including human hair, chicken meat, black tea and canned fish.

Ion Exchange Technology Development in Support of the Urine Processor Assembly Precipitation Prevention Project for the International Space Station

NASA Technical Reports Server (NTRS)

Mitchell, Julie L.; Broyan, James L.; Pickering, Karen D.; Adam, Niklas; Casteel, Michael; Callahan, Michael; Carrier, Chris

2012-01-01

In support of the Urine Processor Assembly Precipitation Prevention Project (UPA PPP), multiple technologies were explored to prevent CaSO4 2H2O (gypsum) precipitation during the on-orbit distillation process. Gypsum precipitation currently limits the water recovery rate onboard the International Space Station (ISS) to 70% versus the planned 85% target water recovery rate. Due to its ability to remove calcium cations in pretreated augmented urine (PTAU), ion exchange was selected as one of the technologies for further development by the PPP team. A total of 13 ion exchange resins were evaluated in various equilibrium and dynamic column tests with solutions of dissolved gypsum, urine ersatz, PTAU, and PTAU brine at 85% water recovery. While initial evaluations indicated that the Purolite SST60 resin had the highest calcium capacity in PTAU (0.30 meq/mL average), later tests showed that the Dowex G26 and Amberlite FPC12H resins had the highest capacity (0.5 meq/mL average). Testing at the Marshall Spaceflight Center (MSFC) integrates the ion exchange technology with a UPA ground article under flight-like pulsed flow conditions with PTAU. To date, no gypsum precipitation has taken place in any of the initial evaluations.

Synthesis and Release of Cyclic Adenosine 3′:5′-Monophosphate by Ochromonas malhamensis1

PubMed Central

Bressan, Ray A.; Handa, Avtar K.; Quader, Hartmut; Filner, Philip

1980-01-01

The chrysophycean alga, Ochromonas malhamensis Pringsheim, was shown to synthesize cyclic adenosine 3′:5′-monophosphate (cAMP) and to release it into the culture medium. Cells contained 3 to 3,000 picomoles per gram fresh weight; medium contained up to 20 times the amount in the cells. Putative [32P]cAMP was purified from cultures supplied [32P]phosphate. The compound was identified as [32P]cAMP by co-chromatography with authentic cAMP through 10 serial steps; by chemical deamination at the same rate as authentic cAMP, to a 32P compound with the chromatographic behavior of cIMP; and by its conversion through the action of cyclic nucleotide phosphodiesterase to a 32P compound with the chromatographic behavior of 5′-AMP. A two-step procedure involving chromatography on alumina and on Dowex 50 purified the unlabeled compound from cells or medium sufficiently for it to be assayable by competitive inhibition of binding of [3H]cAMP to cAMP-binding protein (Gilman assay) or by stimulation of cAMP-dependent protein kinase. The activity was destroyed by cyclic nucleotide phosphodiesterase with the same kinetics as authentic cAMP, provided that an endogenous inhibitor of the phosphodiesterase was first removed by an additional purification step. Images PMID:16661154

Analysis of urinary metanephrines by reversed-phase high-performance liquid chromatography and electrochemical detection.

PubMed

Bertani-Dziedzic, L M; Krstulovic, A M; Dziedzic, S W; Gitlow, S E; Cerqueira, S

1981-02-19

A sensitive and specific direct analysis of urinary normetanephrine (NMN) and metanephrine (MN) was achieved utilizing reversed-phase high performance liquid chromatography and electrochemical detection. Individual specimens from "control" subjects and those with pheochromocytoma were hydrolyzed and the metanephrines separated from other urinary constituents by elution with ammonia from a Dowex CG-50 resin. Chromatographic peaks were identified by retention behavior, co-chromatography with reference compounds, ratio of responses at various oxidation potentials and stopped-flow UV spectra of the collected fractions. The NMN and MN content for the control subjects was between 0.086 and 0.21 (mean - 0.14) microgram/mg creatinine and 0.012 and 0.092 (mean = 0.039) microgram/mg creatinine, respectively. The values for subjects with pheochromocytoma varied from 1.5 to 27.5 (mean = 9.9) microgram/mg creatinine for NMN and 0.10 to 1.60 (mean = 0.86) microgram/mg creatine for MN. The patient with ganglioneuroma had an NMN of 4.1 and an MN of 0.80 microgram/mg creatinine. While this method permits discrimination between those patients with pheochromocytoma and the overwhelming majority of hypertensive patients, it may ultimately be further extended to separate normal subjects from those with more subtle derangements in catecholamine metabolism.

Bromine isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry with a conventional sample introduction system.

PubMed

de Gois, Jefferson S; Vallelonga, Paul; Spolaor, Andrea; Devulder, Veerle; Borges, Daniel L G; Vanhaecke, Frank

2016-01-01

A simple and accurate methodology for Br isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with pneumatic nebulization for sample introduction was developed. The Br(+) signals could be measured interference-free at high mass resolution. Memory effects for Br were counteracted using 5 mmol L(-1) of NH4OH in sample, standard, and wash solutions. The major cation load of seawater was removed via cation exchange chromatography using Dowex 50WX8 resin. Subsequent Br preconcentration was accomplished via evaporation of the sample solution at 90 °C, which did not induce Br losses or isotope fractionation. Mass discrimination was corrected for by external correction using a Cl-matched standard measured in a sample-standard bracketing approach, although Sr, Ge, and Se were also tested as potential internal standards for internal correction for mass discrimination. The δ(81)Br (versus standard mean ocean bromide (SMOB)) values thus obtained for the NaBr isotopic reference material NIST SRM 977 and for IRMM BCR-403 seawater certified reference material are in agreement with literature values. For NIST SRM 977, the (81)Br/(79)Br ratio (0.97291) was determined with a precision ≤0.08‰ relative standard deviation (RSD).

Determination of the mass transfer limiting step of dye adsorption onto commercial adsorbent by using mathematical models.

PubMed

Marin, Pricila; Borba, Carlos Eduardo; Módenes, Aparecido Nivaldo; Espinoza-Quiñones, Fernando R; de Oliveira, Silvia Priscila Dias; Kroumov, Alexander Dimitrov

2014-01-01

Reactive blue 5G dye removal in a fixed-bed column packed with Dowex Optipore SD-2 adsorbent was modelled. Three mathematical models were tested in order to determine the limiting step of the mass transfer of the dye adsorption process onto the adsorbent. The mass transfer resistance was considered to be a criterion for the determination of the difference between models. The models contained information about the external, internal, or surface adsorption limiting step. In the model development procedure, two hypotheses were applied to describe the internal mass transfer resistance. First, the mass transfer coefficient constant was considered. Second, the mass transfer coefficient was considered as a function of the dye concentration in the adsorbent. The experimental breakthrough curves were obtained for different particle diameters of the adsorbent, flow rates, and feed dye concentrations in order to evaluate the predictive power of the models. The values of the mass transfer parameters of the mathematical models were estimated by using the downhill simplex optimization method. The results showed that the model that considered internal resistance with a variable mass transfer coefficient was more flexible than the other ones and this model described the dynamics of the adsorption process of the dye in the fixed-bed column better. Hence, this model can be used for optimization and column design purposes for the investigated systems and similar ones.

Adsorption of four perfluorinated acids on non ion exchange polymer sorbents.

PubMed

Senevirathna, S T M L D; Tanaka, S; Fujii, S; Kunacheva, C; Harada, H; Shivakoti, B R; Dinh, H; Ariyadasa, T

2011-01-01

Perfluorinated compounds (PFCs) have attracted global concern due to their ubiquitous distribution and properties of persistence, bio accumulation and toxicity. The process of adsorption has been identified as an effective technique to remove PFCs in water. Different non ion-exchange polymeric adsorbents were tested with regard to their sorption kinetics and isotherms at low PFCs concentrations. Selected PFCs were perfluorobutanoic acid (PFBA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) and the tested polymers were three types of Dowex optopores (V-493, V503, and L493), Amberlite XAD-4, and Filtrasorb 400 (Granular Activated Carbon-GAC). We observed the selective adsorption of PFCs on synthetic polymers. For PFDA, Amberlite XAD-4 gave the Freundlich adsorption constant of 2,965 (microg PFCs/g sorbent)(microg PFCs/L)(-n), which was higher than that of GAC (121.89 (microg PFCs/g sorbent) (microg PFCS/L)(-n)). In the case of PFBA, GAC showed better performance (13.36) (microg PFCs/g sorbent) microg PFCS/L)(-n) than synthetic polymers (0.62-5.23) (microg PFCs/g sorbent) (microg PFCS/L)(-n). Adsorption kinetics of all adsorbents were well described (R2 = 0.85-1) by pseudo-second order kinetic model. Sorption capacity was influenced by initial PFCs concentration for all adsorbents. GAC reached the equilibrium concentration within 4 hours, Amberlite XAD 4 reached it within 10 hours and other polymers took more than 70 hours.

Hydrometallurgical Separation of Niobium and Tantalum: A Fundamental Approach

NASA Astrophysics Data System (ADS)

Nete, Motlalepula; Purcell, Walter; Nel, Johann T.

2016-02-01

A mixture of pure Ta2O5 and Nb2O5 was dissolved using two different fluxes, namely NH4F·HF and Na2HPO4/NaH2PO4·H2O. Selective precipitation and ion exchange were used as separation techniques. Selective precipitation using p-phenylediamine in a fluoride matrix resulted in the isolation of 73(3)% tantalum accompanied by 23(5)% niobium. A separation factor of 11(4) was obtained. A single solvent extraction step using methyl-isobutyl ketone at a 4 M H2SO4 yielded excellent Ta and Nb separation in the fluoride solution with 80% of the Ta and only 2% Nb recovered in the organic layer. A two-step extraction recovered 100% Ta at 0.5-4 M H2SO4 with a separation factor of ~2000. A study of the extraction mechanism indicated that the stability of the protonated compounds such as H2TaF7/H2NbOF5 is in the extraction and separation determining steps in this process. A K' (double de-protonated constant) of approximately 0.2 was calculated for H2TaF7. Only 91.7% Nb and 73.4% Ta were recovered from anion separation using strong Amberlite resin and 96.1% Nb and 52.3% using the weak Dowex Marathon resin from fluoride dissolution.

Cement waste-form development for ion-exchange resins at the Rocky Flats Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veazey, G.W.; Ames, R.L.

1997-03-01

This report describes the development of a cement waste form to stabilize ion-exchange resins at Rocky Flats Environmental Technology Site (RFETS). These resins have an elevated potential for ignition due to inadequate wetness and contact with nitrates. The work focused on the preparation and performance evaluation of several Portland cement/resin formulations. The performance standards were chosen to address Waste Isolation Pilot Plant and Environmental Protection Agency Resource Conservation and Recovery Act requirements, compatibility with Rocky Flats equipment, and throughput efficiency. The work was performed with surrogate gel-type Dowex cation- and anion-exchange resins chosen to be representative of the resin inventorymore » at RFETS. Work was initiated with nonactinide resins to establish formulation ranges that would meet performance standards. Results were then verified and refined with actinide-containing resins. The final recommended formulation that passed all performance standards was determined to be a cement/water/resin (C/W/R) wt % ratio of 63/27/10 at a pH of 9 to 12. The recommendations include the acceptable compositional ranges for each component of the C/W/R ratio. Also included in this report are a recommended procedure, an equipment list, and observations/suggestions for implementation at RFETS. In addition, information is included that explains why denitration of the resin is unnecessary for stabilizing its ignitability potential.« less

Ion Exchange Technology Development in Support of the Urine Processor Assembly Precipitation Prevention Project for the International Space Station

NASA Technical Reports Server (NTRS)

Mitchell, Julie L.; Broyan, James L.; Pickering, Karen D.; Adam, Niklas; Casteel, Michael; Callaham, Michael; Carrier, Chris

2011-01-01

In support of the Urine Processor Assembly Precipitation Prevention Project (UPA PPP), multiple technologies were explored to prevent CaSO4 dot 2H2O (gypsum) precipitation during the on-orbit distillation process. Gypsum precipitation currently limits the water recovery rate onboard the International Space Station (ISS) to 70% versus the planned 85% target water recovery rate. Due to its advanced performance in removing calcium cations in pretreated augmented urine (PTAU), ion exchange was selected as one of the technologies for further development by the PPP team. A total of 12 ion exchange resins were evaluated in various equilibrium and dynamic column tests with solutions of dissolved gypsum, urine ersatz, PTAU, and PTAU brine at 85% water recovery. While initial evaluations indicated that the Purolite SST60 resin had the highest calcium capacity in PTAU (0.30 meq/mL average), later tests showed that the Dowex G26 and Amberlite FPC12H resins had the highest capacity (0.5 meq/mL average). Further dynamic column testing proved that G26 performance is +/- 10% of that value at flow rates of 0.45 and 0.79 Lph under continuous flow, and 10.45 Lph under pulsed flow. Testing at the Marshall Spaceflight Center (MSFC) integrates the ion exchange technology with a UPA ground article under flight-like pulsed flow conditions with PTAU. To date, no gypsum precipitation has taken place in any of the initial evaluations.

Depth profile of 236U/238U in soil samples in La Palma, Canary Islands

PubMed Central

Srncik, M.; Steier, P.; Wallner, G.

2011-01-01

The vertical distribution of the 236U/238U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the 240Pu/239Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA® Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1x2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios 236U/238U, 240Pu/239Pu and 236U/239Pu, respectively. The 236U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio 240Pu/239Pu indicated a global fallout signature we assume the same origin as the probable source for 236U. Our measured 236U/239Pu value of around 0.2 is within the expected range for this contamination source. PMID:21481502

Improvement of drug loading onto ion exchange resin by cyclodextrin inclusion complex.

PubMed

Samprasit, Wipada; Rojanarata, Theerasak; Akkaramongkolporn, Prasert; Ngawhirunpat, Tanasait; Sila-on, Warisada; Opanasopit, Praneet

2013-11-01

Ion exchange resins have ability to exchange their counter ions for ionized drug in the surrounding medium, yielding "drug resin complex." Cyclodextrin can be applied for enhancement of drug solubility and stability. Cyclodextrin inclusion complex of poorly water-soluble NSAIDs, i.e. meloxicam and piroxicam, was characterized and its novel application for improving drug loading onto an anionic exchange resin, i.e. Dowex® 1×2, was investigated. β-Cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) were used for the preparation of inclusion complex with drugs in solution state at various pH. The inclusion complex was characterized by phase solubility, continuous variation, spectroscopic and electrochemistry methods. Then, the drug with and without cyclodextrin were equilibrated with resin at 1:1 and 1:2 weight ratio of drug and resin. Solubility of the drugs was found to increase with increasing cyclodextrin concentration and pH. The increased solubility was explained predominantly due to the formation of inclusion complex at low pH and the increased ionization of drug at high pH. According to characterization studies, the inclusion complex was successfully formed with a 1:1 stoichiometry. The presence of cyclodextrin in the loading solution resulted in the improvement of drug loading onto resin. Enhancing drug loading onto ion-exchange resin via the formation of cyclodextrin inclusion complex is usable in the development of ion-exchange based drug delivery systems, which will beneficially reduce the use of harmful acidic or basic and organic chemicals.

On-line ion-exchange preconcentration and determination of traces of platinum by electrothermal atomic absorption spectrometry.

PubMed

González García, M M; Sánchez Rojas, F; Bosch Ojeda, C; García de Torres, A; Cano Pavón, J M

2003-04-01

A method to determine trace amounts of platinum in different samples based on electrothermal atomic absorption spectrometry is described. The preconcentration step is performed on a chelating resin microcolumn [1,5-bis(2-pyridyl)-3-sulfophenyl methylene thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex 1x8-200)] placed in the autosampler arm. The combination of a peristaltic pump for sample loading and the atomic absorption spectrometer pumps for elution through a selection valve simplifies the hardware. The peristaltic pump and the selection valve are easily controlled electronically with two switches placed in the autosampler, which are activated when the autosampler arm is down. Thus, the process is fully automated without any modification of the software of the atomic absorption spectrometer. Under the optimum conditions with a 60-s preconcentration time, a sample flow rate of 2.4 mL min(-1), and an injection volume of eluent of 40 microL, a linear calibration graph was obtained in the range 0-100 ng mL(-1). The enrichment factor was 14. The detection limit under these conditions is 1 ng mL(-1), and the relative standard deviation (RSD) is 1.6% for 10 ng mL(-1) of Pt. The method has been applied to the determination of platinum in catalyst, vegetation, soil, and natural water samples. The results showed good agreement with the certified value and the recoveries of Pt added to samples were 98-105%.

An apparatus for the preparation of [15O]-H2O for rapid repetitive PET studies

NASA Astrophysics Data System (ADS)

Dahl, J. R.; Chaly, T. C.; Matacchieri, R. A.; Yee, A.; Dhawan, V.; Horowitz, S.; Jespersen, K.; Margouleff, D.; Eidelberg, D.

1999-06-01

The use of [15O]-H2O to follow changes in cerebral blood flow using PET has become frequent and widespread, requiring an apparatus easily operated by personnel unfamiliar with the physics and chemistry involved. Oxygen-15 is prepared by the 14N(d,n)15O nuclear reaction using a target of UHP nitrogen with 1% UHP hydrogen added, contained in a target chamber similar to that reported for the preparation of [18F]-F2. Nucleogenic 15O reacts with hydrogen in the target gas to produce [15O]-H2O. Some of the N target reacts with hydrogen to produce NH3, which must be removed. At the end of bombardment (minimum 6 min.) the target gas is released through a small amount of parenteral water which then flows through approximately 50 mg Dowex 50W-X8 resin (100-200 mesh) to remove the NH3. Sufficient 23.4% NaCl solution is added to produce an isotonic solution. The isotonic solution is sterilized by filtration through a 0.22 micron filter into an injection syringe which is sent via pneumatic transport to the PET imaging room. The apparatus, which uses a programmable logic controller and four switches to allow the operator to select standby, refill, collect activity, or deliver dose operations of the production process, provides doses of [15O]-H2O up to 35 mCi/dose at intervals as frequent as seven minutes with minimal radiation exposure to the operators.

A new ion selective electrode for cesium (I) based on calix[4]arene-crown-6 compounds.

PubMed

Ramanjaneyulu, P S; Kumar, Abha Naveen; Sayi, Y S; Ramakumar, K L; Nayak, S K; Chattopadhyay, S

2012-02-29

A polyvinylchloride (PVC) based liquid membrane ion selective electrode (ISE) for cesium has been developed. 25,27-Dihydroxycalix[4]arene-crown-6 (L1), 5,11,17,23-tetra-tert-butyl-25,27-dimethoxycalix[4]arene-crown-6 (L2) and 25,27-bis(1-octyloxy)calix[4]arene-crown-6 (L3) were investigated for their use as ionophores. The cation exchange resin DOWEX-50W was used to maintain low activity Cs+ in inner filling solution to improve the performance. The best response for cesium was observed with L3 along with optimized membrane constituents and composition. Excellent Nernstian response (56.6 mV/decade of Cs(I)) over the concentration range 10(-7) to 10(-2)M of Cs(I) was obtained with a fast response time of less than 10s. Detection limit for Cs(I) using the present ISE is 8.48×10(-8) M Cs(I). Separate solution method (SSM) was applied to ascertain the selectivity for Cs(I) over alkali, alkaline earth and transition metal ions. The response of ISE for Cs(I) was fairly constant over the pH range of 4-11. The lifetime of the electrode is 10 months which is the highest life for any membrane based Cs-ISE so far developed. The concentration of cesium ion in two simulated high level active waste streams was determined and results agreed well with those obtained independently employing AAS. Copyright © 2011 Elsevier B.V. All rights reserved.

Interference-free determination of trace copper in freshly ripened honeys by flame atomic absorption spectrometry following a preconcentration by solid-phase extraction and a two-step elution process.

PubMed

Pohl, Pawel; Stecka, Helena; Jamroz, Piotr

2014-02-01

A fast and straightforward procedure aimed at separating copper (Cu) ions from monosacharides and preconcentrating their traces before flame atomic absorption spectrometry (FAAS) measurements was developed, and its suitability was evaluated by the analysis of freshly ripened honeys on the content of this environmentally and physiologically relevant element. This procedure included the passage (at 20 mL/min) of 10 % (m/v) solutions of honeys (100 mL) through resin beds of Dowex 50 W × 8-400 to retain Cu by solid-phase extraction (SPE) and separate it from the glucose and fructose matrix. In turn, SPE columns were rinsed at 20 mL/min with 20 mL of water and subsequently washed with 20 mL of a 0.5 mol/L HNO3 solution (at 2.0 mL/min) to elute potassium and sodium. Preconcentrated Cu was stripped (at 2.0 mL/min) with 5.0 mL of a 2.0 mol/L HCl solution and determined by FAAS. The proposed procedure was used for the analysis of six ripened monoflower and multiflower honeys, enabling the measurement of Cu within the range of 0.17-0.42 μg/g and with a precision of 3-10%. Recoveries of Cu added to respective honey solutions were within 94-102%, proving the good accuracy of this procedure. The detection limit of Cu achieved with this SPE preconcentration/separation procedure and FAAS detection was 3.6 ng/g.

Platinum group elements in stream sediments of mining zones: The Hex River (Bushveld Igneous Complex, South Africa)

NASA Astrophysics Data System (ADS)

Almécija, Clara; Cobelo-García, Antonio; Wepener, Victor; Prego, Ricardo

2017-05-01

Assessment of the environmental impact of platinum group elements (PGE) and other trace elements from mining activities is essential to prevent potential environmental risks. This study evaluates the concentrations of PGE in stream sediments of the Hex River, which drains the mining area of the Bushveld Igneous Complex (South Africa), at four sampling points. Major, minor and trace elements (Fe, Ca, Al, Mg, Mn, V, Cr, Zn, Cu, As, Co, Ni, Cd, and Pb) were analyzed by FAAS and ETAAS in suspended particulate matter and different sediment fractions (<63, 63-500 and 500-2000 μm), and Pt, Pd, Rh, and Ir were measured by ICP-MS after removal of interfering elements (cation exchange resin 50W-DOWEX-X8). Procedures were blank-corrected and accuracy checked using reference materials. Nickel, Cr, Pt, Pd, Rh and Ir show concentrations 3-, 13- 18-, 28-, 48- and 44- fold the typical upper continental crust levels, respectively, although lower than concentrations reported for the parent rocks. The highest concentrations were observed closer to the mining area, decreasing with distance and in the <63 μm fraction, probably derived from atmospheric deposition and surface runoff of PGE-rich particles released from mining activities. Thus, mining activities are causing some disturbance of the surface PGE geochemical cycle, increasing the presence of PGE in the fine fraction of river sediments. We propose that indicators such as airborne particulate matter, and soil and river sediment quality, should be added to the protocols for evaluating the sustainability of mining activities.

European roe deer antlers as an environmental archive for fallout (236)U and (239)Pu.

PubMed

Froehlich, M B; Steier, P; Wallner, G; Fifield, L K

2016-01-01

Anthropogenic (236)U and (239)Pu were measured in European roe deer antlers hunted between 1955 and 1977 which covers and extends beyond the period of intensive nuclear weapons testing (1954-1962). The antlers were hunting trophies, and hence the hunting area, the year of shooting and the approximate age of each animal is given. Uranium and plutonium are known to deposit in skeletal tissue. Since antler histology is similar to bone, both elements were expected in antlers. Furthermore, roe deer shed their antlers annually, and hence antlers may provide a time-resolved environmental archive for fallout radionuclides. The radiochemical procedure is based on a Pu separation step by anion exchange (Dowex 1 × 8) and a subsequent U purification by extraction chromatography using UTEVA(®). The samples were measured by Accelerator Mass Spectrometry at the VERA facility (University of Vienna). In addition to the (236)U and (239)Pu concentrations, the (240)Pu/(239)Pu isotopic ratios were determined with a mean value of 0.172 ± 0.023 which is in agreement with the ratio of global fallout (∼0.18). Rather high (236)U/(238)U ratios of the order of 10(-6) were observed. These measured ratios, where the (236)U arises only from global fallout, have implications for the use of the (236)U/(238)U ratio as a fingerprint for nuclear accidents or releases from nuclear facilities. Our investigations have shown the potential to use antlers as a temporally resolved archive for the uptake of actinides from the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Exploring the Mechanism of Biocatalyst Inhibition in Microbial Desulfurization

PubMed Central

Abin-Fuentes, Andres; Mohamed, Magdy El-Said; Wang, Daniel I. C.

2013-01-01

Microbial desulfurization, or biodesulfurization (BDS), of fuels is a promising technology because it can desulfurize compounds that are recalcitrant to the current standard technology in the oil industry. One of the obstacles to the commercialization of BDS is the reduction in biocatalyst activity concomitant with the accumulation of the end product, 2-hydroxybiphenyl (HBP), during the process. BDS experiments were performed by incubating Rhodococcus erythropolis IGTS8 resting-cell suspensions with hexadecane at 0.50 (vol/vol) containing 10 mM dibenzothiophene. The resin Dowex Optipore SD-2 was added to the BDS experiments at resin concentrations of 0, 10, or 50 g resin/liter total volume. The HBP concentration within the cytoplasm was estimated to decrease from 1,100 to 260 μM with increasing resin concentration. Despite this finding, productivity did not increase with the resin concentration. This led us to focus on the susceptibility of the desulfurization enzymes toward HBP. Dose-response experiments were performed to identify major inhibitory interactions in the most common BDS pathway, the 4S pathway. HBP was responsible for three of the four major inhibitory interactions identified. The concentrations of HBP that led to a 50% reduction in the enzymes' activities (IC50s) for DszA, DszB, and DszC were measured to be 60 ± 5 μM, 110 ± 10 μM, and 50 ± 5 μM, respectively. The fact that the IC50s for HBP are all significantly lower than the cytoplasmic HBP concentration suggests that the inhibition of the desulfurization enzymes by HBP is responsible for the observed reduction in biocatalyst activity concomitant with HBP generation. PMID:24096431

[Pollution characteristics of platinum group elements in road rust in Xiamen].

PubMed

Hong, Zhen-yu; Hong, You-wei; Yin, Li-qian; Chen, Jin-sheng; Chen, Yan-ting; Xu, Ling-ling

2015-01-01

With the potential risks for the environment and human health, the concentration and distribution characteristics of platinum group element(PGEs) in road dust in Xiamen city were investigated. Road dust samples were collected from the traffic trunk road, tunnel, tourism area, and industrial area of Xiamen on October 2012. The samples were digested with aqua regia in a microwave assisted digestion system under high pressure condition, separated and purified with cation exchange resin( Dowex AG50W-X8), and the resulting solutions were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the average concentrations(range) of Pd, Pt and Rh in road dust were 246.82 (58.68-765.52) ng x g(-1), 95.45 (42.14-371.36) ng x g(-1) and 51.76 (21.04-119.72) ng x g(-1), respectively, which were two orders of magnitude higher than the background values. Compared with other cities worldwide, the concentrations of Pd, Pt and Rh in road dust in Xiamen were at higher levels. Theconcentrations of PGEs for different functional areas were listed in the following order: tunnel > urban district > industrial area > tourism area, which indicated that their spatial distributions were mainly affected by the traffic intensity. Correlation analysis results showed that concentration of Pd in the urban traffic artery was significantly correlated with Rh, while Pt was not so correlated with Pd and Rh, suggesting that other sources contributed to PGEs in road dust in addition to the vehicle emission. Although motor vehicle traveling was banned in tourist area, the concentration of PGEs was still at a high level. Some of them might originate from the road dust in surrounding area by atmosphere diffusion.

Bear Creek Valley characterization area mixed wastes passive in situ treatment technology demonstration project - status report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, D.; Leavitt, M.; Moss, D.

1997-03-01

Historical waste disposal activities within the Bear Creek Valley (BCV) Characterization Area (CA), at the U.S. Department of Energy (DOE) Oak Ridge Y-12 plant, have contaminated groundwater and surface water above human health risk levels and impacted the ecology of Bear Creek. Contaminates include nitrate, radioisotopes, metals, volatile organic chemicals (VOCS), and common ions. This paper provides a status report on a technology demonstration project that is investigating the feasibility of using passive in situ treatment systems to remove these contaminants. Although this technology may be applicable to many locations at the Oak Ridge Y-12 Plant, the project focuses onmore » collecting the information needed to take CERCLA removal actions in 1998 at the S-3 Disposal Ponds site. Phase 1 has been completed and included site characterization, laboratory screening of treatment media (sorbents; and iron), and limited field testing of biological treatment systems. Batch tests using different Y-12 Plant waters were conducted to evaluate the removal efficiencies of most of the media. Phase 1 results suggest that the most promising treatment media are Dowex 21 k resin, peat moss, zero-valent iron, and iron oxides. Phase 2 will include in-field column testing of these media to assess loading rates, and concerns with clogging, by-products, and long-term treatment efficiency and media stability. Continued testing of wetlands and algal mats (MATs) will be conducted to determine if they can be used for in-stream polishing of surface water. Hydraulic testing of a shallow trench and horizontal well will also be completed during Phase 2. 4 refs., 3 tabs.« less

Isolation, purification, and characterization of thermophilic T80 isoenzyme of xylose isomerase from the xerophyte Cereus pterogonus.

PubMed

Ravikumar, Sambandam; Shyamala, Sivalingam; Muthuraman, Pandurangan; Srikumar, Kotteazeth

2011-01-01

A thermostable isoenzyme (T(80)) of xylose isomerase from the eukaryote xerophyte Cereus pterogonus was purified to homogeneity by precipitation with ammonium sulfate and column chromatography on Dowex-1 ion exchange, with Sephadex G-100 gel filtration, resulting in an approximately 25.55-fold increase in specific activity and a final yield of approximately 17.9%. Certain physiochemical and kinetic properties (K(m) and V(max)) of the T(80) xylose isomerase isoenzyme were investigated. The molecular mass of the purified T(80) isoenzyme was 68 kD determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Polyclonal antibodies against the purified T(80) isoenzyme recognized a single polypeptide band on Western blots. The activation energy required for the thermal denaturation of the isoenzyme was determined to be 61.84 KJ mol(-1). The use of differential scanning calorimetry established the melting temperature of the CPXI isoenzyme to be 80°C, but when studied with added metal ions, melting temperature increases to more than the normal. Fluorescence spectroscopy of T(80) isoenzymes yielded an emission peak with λ(em) at 320 nm and 340 nm, respectively, confirming the presence of Trp residue in these proteins. Electron paramagnetic resonance (EPR) analysis at liquid nitrogen temperature established the presence of Mn(2+) and Co(2+) associated with each isoenzyme. These enzyme species exhibited different thermal and pH stabilities compared to their mesophilic counterparts and offered greater efficiency in functioning as a potential alternate catalytic converter of glucose in the production of high-fructose corn syrup (HFCS) for the sweetener industry and for ethanol production.

A new measurement of the half-life of (166m)Ho.

PubMed

Nedjadi, Y; Bailat, C; Caffari, Y; Froidevaux, P; Wastiel, C; Kivel, N; Guenther-Leopold, I; Triscone, G; Jaquenod, F; Bochud, F

2012-09-01

The work presented here is a new and precise measurement of the half-life of (166m)Ho by determining the activity concentration, using an ionisation chamber calibrated for this nuclide, and measuring the number of (166m)Ho atoms using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Since the isotope (166)Er interferes with the mass spectrometric measurement, Er has to be eliminated from the (166m)Ho radioactive solution. The elimination was achieved using ion-exchange chromatography with the cation exchange resin Dowex AG 50W-X8 and 2-Hydroxybutanoic acid as the mobile phase. After a first transit through the chromatographic column, the purified (166m)Ho eluate was spiked with natural Er to get a resulting Er isotopic composition close to that of natural Er at better than 99.5%, and then it underwent two further separations to eliminate the Er. The activity concentration of this Er-free radioactive (166m)Ho solution was measured in our reference ionisation chamber calibrated for this nuclide by means of the 4πβ(PC)-γ and 4πβ(PS)-4πγ coincidence techniques and integral counting with a well-type NaI(Tl) detector and Monte Carlo efficiencies. An aliquot of this standardized solution was sent to the Paul Scherrer Institute (PSI) for mass concentration determination using an isotope dilution MC-ICP-MS approach. The mass concentration of (166m)Ho in this solution was determined with 0.25% relative standard uncertainty. This value was corroborated by two other independent measurements. The new half-life of (166m)Ho, 1132.6(39) years (k=1), is compatible with the value determined in 1965, but is 5.6% shorter and about 43 times more precise. Copyright © 2012 Elsevier Ltd. All rights reserved.

Determining stressor presence in streams receiving urban and agricultural runoff: development of a benthic in situ toxicity identification evaluation method.

PubMed

Custer, Kevin W; Burton, G Allen; Coelho, Ricardo S; Smith, Preston R

2006-09-01

Determining toxicity in streams during storm-water runoff can be highly problematic because of the fluctuating exposures of a multitude of stressors and the difficulty of linking these dynamic exposures with biological effects. An underlying problem with assessing storm-water quality is determining if toxicity exists and then which contaminant is causing the toxicity. The goal of this research is to provide an alternative to standard toxicity testing methods by incorporating an in situ toxicity identification evaluation (TIE) approach. A benthic in situ TIE bioassay (BiTIE) was developed for separating key chemical classes of stressors in streams during both low- and high-flow events to help discern between point and nonpoint sources of pollution. This BiTIE method allows for chemical class fractionation through the use of resins, and these resins are relatively specific for removing nonpolar organics (Dowex Optipore), ammonia (zeolite), and polywool (control). Three indigenous aquatic insects, a mayfly (Isonychia spp.), a caddisfly (Hydropsyche spp.), and a water beetle (Psephenus herricki), were placed in BiTIE chambers that were filled with natural substrates. Acute 96-h exposures were conducted at Honey Creek, New Carlisle, Ohio, USA (reference site), and Little Beavercreek, Beavercreek, Ohio, USA (impaired site). At both sites, significant (p < 0.025) stressor responses were observed using multiple species with polywool or no resin (control) treatments exhibiting < 80% survival and resin treatments with >80% survival. The BiTIE method showed stressor-response relationships in both runoff and base flow events during 96-h exposures. The method appears useful for discerning stressors with indigenous species in situ.

Red Mexican grapefruit: a novel source for bioactive limonoids and their antioxidant activity.

PubMed

Mandadi, Kranthi K; Jayaprakasha, Guddadarangavvanahally K; Bhat, Narayan G; Patil, Bhimanagouda S

2007-01-01

Citrus limonoids have shown to inhibit the growth of cancer in colon, lung, mouth, stomach and breast in animal and cell culture studies. For the first time in the present study, an attempt has been made to isolate antioxidant fractions and five limonoids from red Mexican grapefruit seeds. Defatted seed powder was successively extracted with hexane, ethyl acetate (EtOAc), acetone, methanol (MeOH) and MeOH/water and the extracts were concentrated under vacuum. Radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and total phenolic content were also measured for comparison with the antioxidant capacity in the phosphomolybdenum method for the above extracts. Acetone and MeOH extracts, respectively, showed the highest (85.7%) and lowest (53.3%) radical scavenging activity, at 500 ppm. The total phenolic contents were found to be highest in the acetone extract (15.94%) followed by the MeOH extract (5.92%), ethyl acetate extract (5.54%) and water extract (5.26%). Antioxidant capacity of the extracts as equivalents to ascorbic acid (micromol/g of the extract) was in the order, EtOAc extract > acetone extract > water extract > methanol extract. Furthermore, the EtOAC and acetone extracts were loaded onto silica gel columns to obtain four limonoid aglycons. MeOH fraction was loaded onto a dowex-50 and sepabeads resin column to obtain a limonoid glucoside. The purity of the isolated five compounds was analyzed by HPLC using a C18 column and UV detection at 210 nm. Finally, the structures of the compounds were identified as obacunone, nomilin, limonin, deacetylnomilin (DAN) and limonin-17-beta-D-glucopyranoside (LG) using 1H and 13C NMR studies.

Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

DOE PAGES

Balboni, Enrica; Spano, T; Cook, N; ...

2017-10-20

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO 2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondarymore » uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca 2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K + and Pb 2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Optimal production of L-threo-2,3-dihydroxyphenylserine (L-threo-DOPS) on a large scale by diastereoselectivity-enhanced variant of L-threonine aldolase expressed in Escherichia coli.

PubMed

Gwon, Hui-Jeong; Yoshioka, Hideki; Song, Nho-Eul; Kim, Jong-Hui; Song, Young-Ran; Jeong, Do-Youn; Baik, Sang-Ho

2012-01-01

This study examined the efficient production and optimal separation procedures for pure L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) from a mixture of diastereomers synthesized by whole-cell aldol condensation reaction, harboring diastereoselectivity-enhanced L-threonine aldolase in Escherichia coli JM109. The addition of the reducing agent sodium sulfite was found to stimulate the production of L-threo-DOPS without affecting the diastereoselectivity ratio, especially at the 50 mM concentration. The optimal pH for diastereoselective synthesis was 6.5. The addition of Triton X-100 also strongly affected the synthesis yield, showing the highest conversion yield at a 0.75% concentration; however, the diastereoselectivity of the L-threonine aldolase was not affected. Lowering the temperature to 10°C did not significantly affect the diastereoselectiviy without affecting the synthesis rate. At the optimized conditions, a mixture of L-threo-DOPS and L-erythro-DOPS was synthesized by diastereoselectivity-enhanced L-threonine aldolase from E. coli in a continuous process for 100 hr, yielding an average of 4.0 mg/mL of L-threo-DOPS and 60% diastereoselectivity (de), and was subjected to two steps of ion exchange chromatography. The optimum separation conditions for the resin and solvent were evaluated in which it was found that a two-step process with the ion-exchange resin Dowex 50 W × 8 and activated carbon by washing with 0.5 N acetic acid was sufficient to separate the L-threo-DOPS. By using two-step ion-exchange chromatography, synthesized high-purity L-threo-DOPS of up to 100% was purified with a yield of 71%. The remaining substrates, glycine and 3,4-dihydroxybenzaldehyde, were recovered successfully with a yield of 71.2%. Our results indicate this potential procedure as an economical purification process for the synthesis and purification of important L-threo-DOPS at the pharmaceutical level.

Precise ruthenium fission product isotopic analysis using dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Christopher F.; Dresel, P. Evan; Geiszler, Keith N.

2006-05-09

99Tc is a subsurface contaminant of interest at numerous federal, industrial, and international facilities. However, as a mono-isotopic fission product, 99Tc lacks the ability to be used as a signature to differentiate between the different waste disposal pathways that could have contributed to subsurface contamination at these facilities. Ruthenium fission-product isotopes are attractive analogues for the characterization of 99Tc sources because of their direct similarity to technetium with regard to subsurface mobility, and their large fission yields and low natural background concentrations. We developed an inductively coupled plasma mass spectrometry (ICP-MS) method capable of measuring ruthenium isotopes in groundwater samplesmore » and extracts of vadose zone sediments. Samples were analyzed directly on a Perkin Elmer ELAN DRC II ICP-MS after a single pass through a 1-ml bed volume of Dowex AG 50W-X8 100-200 mesh cation exchange resin. Precise ruthenium isotopic ratio measurements were achieved using a low-flow Meinhard-type nebulizer and long sample acquisition times (150,000 ms). Relative standard deviations of triplicate replicates were maintained at less than 0.5% when the total ruthenium solution concentration was 0.1 ng/ml or higher. Further work was performed to minimize the impact caused by mass interferences using the dynamic reaction cell (DRC) with O2 as the reaction gas. The aqueous concentrations of 96Mo and 96Zr were reduced by more than 99.7% in the reaction cell prior to injection of the sample into the mass analyzer quadrupole. The DRC was used in combination with stable-mass correction to quantitatively analyze samples containing up to 2-orders of magnitude more zirconium and molybdenum than ruthenium. The analytical approach documented herein provides an efficient and cost-effective way to precisely measure ruthenium isotopes and quantitate total ruthenium (natural vs. fission-product) in aqueous matrixes.« less

Calibrating compound-specific stable nitrogen isotope analysis in avian eggs as bioarchives for paleoreconstruction

NASA Astrophysics Data System (ADS)

Preciado, C., Jr.

2016-12-01

Compound-specific stable isotope analysis (CSIA) has become a powerful tool for reconstructing consumer-resource relationships in modern and ancient systems. Stable nitrogen isotope analysis (δ15N) of "trophic" and "source" amino acids provides independent proxies of trophic position and the δ15N value at the base of the food web, respectively. When applied to avian egg tissues (e.g., shell protein, membrane), which can be preserved in the archaeological record, this approach can be used to address complex questions in food web architecture and biogeochemical cycling. In this study, we examined how sample-processing protocols affected the chromatography and reliability of δ15N values of individual amino acids in avian (chicken and penguin) egg components (shell protein, membrane, yolk, and albumen) via gas chromatography-combustion-isotope ratio mass spectrometry. "Unprocessed" egg tissues underwent standard acid hydrolysis protocols prior to derivatization, and resulted in poor chromatography with highly variable δ15N values across replicates. "Processed" samples were eluted through cation exchange columns (Dowex 50WX*400) prior to derivatization, followed by a P-buffer (KH2PO4 + Na2HPO4)-chloroform centrifugation extraction to remove confounding peaks and matrix impurities. These additional procedures greatly improved the chromatography of the "processed" samples, revealing better peak separation and baseline integration as well as lower δ15N variability. Additionally, a standard lipid extraction was necessary for yolk but not membrane, albumen, and shell. While the additional procedures applied to the "columned" samples did result in a significant reduction in sample yield ( 20%), it was non-fractionating and thus only affected the total sample sizes necessary for δ15N CSIA (shell protein 50mg and membrane, yolk, and albumen 0.5mg). The protocols developed here will streamline CSIA of egg tissues for future work in avian ecology.

Elution of Re-188 from W-188/Re-188 generators with salts of weak acids permits efficient concentration to low volumes using a new tandem cation/anion exchange system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guhlke, S.; Beets, A.L.; Knapp, F.F. Jr.

1997-05-01

Re-188, available from a W-188/Re-188 generator, is an important therapeutic radioisotope for bone pain palliation, cancer therapy and intravascular brachytherapy, etc. Because of the relatively low specific activity of reactor-produced W-188 (ORNL HFIR, 296-370 MBq mCi/mg W-186 for 2 cycles), methods of concentrating the Re-188 bolus (10-12 mL) from clinical scale (18.5-37 BGq W-188) generators (5-6 gm alumina) are thus very important. We demonstrate for the first time a new strategy of generator elution with salts of weak acids and specific perrhenate anion {open_quotes}trapping{close_quotes} with QMA anion columns. Re-188 perrhenate is efficiently eluted (65-75%) from the alumina-based generator with 0.15-0.3more » M ammonium acetate. An acetic acid solution of Re-188 perrhenic acid is obtained by subsequent on-line passage of the generator eluant through a DOWEX AG 50Wx8 (200-400 mesh, H{sup +} form) column. Since acetic acid is not ionized (< 0.001%) at this pH (< pK{sub a} = 4.76) the perrhenate anion is then specifically trapped on a QMA {open_quotes}Light{close_quotes} anion extraction column. QMA elution with 0.9% NaCl, provides Re-188 perrhenate solution in <1 mL. Concentration of 10-20 mL of Re-188 solution (> 15 BGq) in <1 mL has been demonstrated using this simple new approach, which is also effective for concentration of Tc-99m from low specific activity Mo-99 (n,y) generators. The cation/anion tandem system is inexpensive and disposable and use can be easily automated. The availability of this very simple, efficient system is important for broad use of rhenium-188.« less

Chromatographic separation of fructose from date syrup.

PubMed

Al Eid, Salah M

2006-01-01

The objective of this study is to provide a process for separating fructose from a mixture of sugars containing essentially fructose and glucose, obtained from date palm fruits. The extraction procedure of date syrup from fresh dates gave a yield of 86.5% solids after vacuum drying. A process for separating fructose from an aqueous solution of date syrup involved adding the date syrup solutions (20, 30 and 40% by weight) to a chromatographic column filled with Dowex polystyrene strong cation exchange gel matrix resin Ca2 + and divinylbenzene, a functional group, sulfonic acid, particle size 320 microm, with a flow rate of 0.025 and 0.05 bed volume/min, under 30 and 70 degrees C column temperature. After the date sugar solution batch, a calculated quantity of water was added to the column. Glucose was retained by the resin more weakly than fructose and proceeded faster into the water batch flowing ahead. Three fractions were collected: a glucose-rich fraction, a return fraction, and a fructose-rich fraction. The return fraction is based on when the peaks of fructose and glucose were reached, which could be determined by means of an analyzer (polarimeter) based on the property of glucose and fructose solutions to turn the polarization level of polarized light. A high yield of fructose is obtained at 70 degrees C column temperature with a flow rate of 0.025 bed volume/min and date syrup solution containing 40% sugar concentration. The low recovery by weight obtained using date syrup solutions having a sugar concentration of 20 and 30%, encourages the use of a concentration of 40%. However, with the 40% date syrup supply the average concentrations of glucose and fructose in the return fractions were more than 40%, which can be used for diluting the thick date syrup solution extracted from dates.

Renewable chemiluminescence optosensors based on implementation of bead injection principle with multicommutation.

PubMed

Domínguez-Romero, Juan C; Gilbert-López, Bienvenida; Beneito-Cambra, Miriam; Molina-Díaz, Antonio

2018-05-15

In this work, the implementation of Bead Injection with multicommutation-based flow systems is reported. A surface renewable chemiluminescence (CL) flow sensor is presented based on the use of CL reaction of luminol with H 2 O 2 . Dowex 1 × 8 beads with immobilized luminol onto them were injected in the flow system by means of a six-port rotary valve and were accommodated into a 1 mm optical glass flow cell placed just in front of the rectangular photosensor window with the same size than the cell wall. Automatic computer-controlled manipulation of both reagents and sample solutions was undertaken using a multicommutated flow system which comprises five three-way solenoid valves, a home-made electronic interface and a Java-written software. Once the chemiluminescence signal was registered, sensing beads were automatically discarded out with a six-port rotary valve without needing to reverse or stop the flow. As a proof of concept and example, the enhancement of the chemiluminescence signal produced by Co(II) on the luminol-H 2 O 2 reaction in alkaline medium was used for illustrating this implementation determining vitamin B 12 in pharmaceutical preparations (after mineralization for releasing Co(II)). The analytical performance of the approach was satisfactory, showing a linear dynamic range from 1.7 to 50 µg L -1 , a detection limit of 0.5 µg L -1 , RSD (%) of 5.3%, with a sampling frequency of 11 h -1 . The proposed approach was applied to different samples and the results were consistent with those obtained with a reference method based on ICP-MS. Based on the same reaction (or re-configuring the system to accommodate it to reaction requirements) the approach can also be applied to the determination of other metal ions such as Cr(III) and Fe(II) and appropriately extended to molecules of bioanalytical interest based e.g. in CL immunoassays, given its versatility. Copyright © 2018 Elsevier B.V. All rights reserved.

Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balboni, Enrica; Spano, T; Cook, N

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO 2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondarymore » uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca 2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K + and Pb 2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Identification of fermentation inhibitors in wood hydrolyzates and removal of inhibitors by ion exchange and liquid-liquid extraction

NASA Astrophysics Data System (ADS)

Luo, Caidian

1998-12-01

Common methods employed in the ethanol production from biomass consist of chemical or enzymatic degradation of biomass into sugars and then fermentation of sugars into ethanol or other chemicals. However, some degradation products severely inhibit the fermentation processes and substantially reduce the efficiency of ethanol production. How to remove inhibitors from the reaction product mixture and increase the production efficiency are critical in the commercialization of any processes of energy from biomass. The present study has investigated anion exchange and liquid-liquid extraction as potential methods for inhibitor removal. An analytical method has been developed to identify the fermentation inhibitors in a hydrolyzate. The majority of inhibitors present in hybrid poplar hydrolyzate have positively been identified. Ion exchange with weak basic Dowex-MWA-1 resin has been proved to be an effective mean to remove fermentation inhibitors from hybrid poplar hydrolyzate and significantly increase the fermentation productivity. Extraction with n-butanol might be a preferred way to remove inhibitors from wood hydrolyzates and improve the fermentability of sugars in the hydrolyzates. n-Butanol also removes some glucose, mannose and xylose from the hydrolyzate. Inhibitor identification reveals that lignin and sugar degradation compounds including both aromatic and aliphatic aldehydes and carboxylic acids formed in hydrolysis, plus fatty acids and other components from wood extractives are major fermentation inhibitors in Sacchromyces cerevisiae fermentation. There are 35 components identified as fermentation inhibitors. Among them, 4-hydroxy benzoic acid, 3,4-dihydroxy benzoic acid, syringic acid, syringaldehyde, and ferulic acid are among the most abundant aromatic inhibitors in hybrid poplar hydrolyzate. The conversion of aldehyde groups into carboxylic acid groups in the nitric acid catalyzed hydrolysis reduces the toxicity of the hydrolyzate. A wide spectrum of aliphatic acids has been identified in the wood hydrolyzate studied. They are potential fermentation inhibitors probably similar to acetic acid. Ethyl acetate extraction has also been demonstrated to be a possible method to remove fermentation inhibitors from hydrolyzates. (Abstract shortened by UMI.)

An evaluation of the migration of antimony from polyethylene terephthalate (PET) plastic used for bottled drinking water.

PubMed

Chapa-Martínez, C A; Hinojosa-Reyes, L; Hernández-Ramírez, A; Ruiz-Ruiz, E; Maya-Treviño, L; Guzmán-Mar, J L

2016-09-15

The leaching of antimony (Sb) from polyethylene terephthalate (PET) bottling material was assessed in twelve brands of bottled water purchased in Mexican supermarkets by atomic fluorescence spectrometry with a hydride generation system (HG-AFS). Dowex® 1X8-100 ion-exchange resin was used to preconcentrate trace amounts of Sb in water samples. Migration experiments from the PET bottle material were performed in water according to the following storage conditions: 1) temperature (25 and 75°C), 2) pH (3 and 7) and 3) exposure time (5 and 15days), using ultrapure water as a simulant for liquid foods. The test conditions were studied by a 2(3) factorial experimental design. The Sb concentration measured in the PET packaging materials varied between 73.0 and 111.3mg/kg. The Sb concentration (0.28-2.30μg/L) in all of the PET bottled drinking water samples examined at the initial stage of the study was below the maximum contaminant level of 5μg/L prescribed by European Union (EU) regulations. The parameters studied (pH, temperature, and storage time) significantly affected the release of Sb, with temperature having the highest positive significant effect within the studied experimental domain. The highest Sb concentration leached from PET containers was in water samples at pH7 stored at 75°C for a period of 5days. The extent of Sb leaching from the PET ingredients for different brands of drinking water can differ by as much as one order of magnitude in experiments conducted under the worst-case conditions. The chronic daily intake (CDI) caused by the release of Sb in one brand exceeded the Environmental Protection Agency (USEPA) regulated CDI value of 400ng/kg/day, with values of 514.3 and 566.2ng/kg/day for adults and children. Thus, the appropriate selection of the polymer used for the production of PET bottles seems to ensure low Sb levels in water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

A solid phase extraction procedure for the determination of Cd(II) and Pb(II) ions in food and water samples by flame atomic absorption spectrometry.

PubMed

Daşbaşı, Teslima; Saçmacı, Şerife; Ülgen, Ahmet; Kartal, Şenol

2015-05-01

A relatively rapid, accurate and precise solid phase extraction method is presented for the determination of cadmium(II) and lead(II) in various food and water samples. Quantitation is carried out by flame atomic absorption spectrometry (FAAS). The method is based on the retention of the trace metal ions on Dowex Marathon C, a strong acid cation exchange resin. Some important parameters affecting the analytical performance of the method such as pH, flow rate and volume of the sample solution; type, concentration, volume, flow rate of the eluent; and matrix effects on the retention of the metal ions were investigated. Common coexisting ions did not interfere on the separation and determination of the analytes. The detection limits (3 σb) for Cd(II) and Pb(II) were found as 0.13 and 0.18 μg L(-1), respectively, while the limit of quantification values (10 σb) were computed as 0.43 and 0.60 μg L(-1) for the same sequence of the analytes. The precision (as relative standard deviation was lower than 4% at 5 μg L(-1) Cd(II) and 10 μg L(-1) Pb(II) levels, and the preconcentration factor was found to be 250. The accuracy of the proposed procedure was verified by analysing the certified reference materials, SPS-WW2 Batch 108 wastewater level 2 and INCT-TL-1 tea leaves, with the satisfactory results. In addition, for the accuracy of the method the recovery studies (⩾ 95%) were carried out. The method was applied to the determination of the analytes in the various natural waters (lake water, tap water, waste water with boric acid, waste water with H2SO4) and food samples (pomegranate flower, organic pear, radish leaf, lamb meat, etc.), and good results were obtained. While the food samples almost do not contain cadmium, they have included lead at low levels of 0.13-1.12 μg g(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

Simple flow injection colorimetric system for determination of paraquat in natural water.

PubMed

Chuntib, Prakit; Jakmunee, Jaroon

2015-11-01

A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30 cm, flow rate 2.0 mL min(-1), sample volume 100 μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06 mol L(-1), a linear calibration graph in the range of 0.2-10.0 mg L(-1) with a correlation coefficient of 0.9996, and a limit of detection of 0.15 mg L(-1) were achieved. Relative standard deviation for 9 replicate injections of 1 mg L(-1) paraquat is 3.7%. A sample throughput of 40 injections h(-1) was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0 mg L(-1) paraquat standard into water samples were in the range of 104-110% and 101-105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water. Copyright © 2015 Elsevier B.V. All rights reserved.

Incorporation of zero valent iron nanoparticles in the matrix of cationic resin beads for the remediation of Cr(VI) contaminated waters.

PubMed

Toli, Aikaterini; Chalastara, Konstantina; Mystrioti, Christiana; Xenidis, Anthimos; Papassiopi, Nymphodora

2016-07-01

The objective of present study was to obtain the fixation of nano zero valent iron (nZVI) particles on a permeable matrix and evaluate the performance of this composite material for the removal of Cr(VI) from contaminated waters. The experiments were carried out using the cationic resin Dowex 50WX2 as porous support of the iron nanoparticles. The work was carried out in two phases. The first phase involved the fixation of nZVI on the resin matrix. The resin granules were initially mixed with a FeCl3 solution to obtain the adsorption of Fe(III). Then the Fe(III) loaded resin (RFe) was treated with polyphenol solutions to obtain the reduction of Fe(III) to the elemental state. Two polyphenol solutions were tested as reductants, i.e. green tea extract and gallic acid. Green tea was found to be inefficient, probably due to the relatively big size of the contained polyphenol molecules, but gallic acid molecules were able to reach adsorbed Fe(III) and reduce the cations to the elemental state. The second phase was focused on the investigation of Cr(VI) reduction kinetics using the nanoiron loaded resins (R-nFe). It was found that the reduction follows a kinetic law of first order with respect to Cr(VI) and to the embedded nanoiron. Compared to other similar products, this composite material was found to have comparable performance regarding reaction rates and higher degree of iron utilization. Namely the rate constant for the reduction of Cr(VI), in the presence of 1 mM nZVI, was equivalent to 1.4 h of half-life time at pH 3.2 and increased to 24 h at pH 8.5. The degree of iron utilization was as high as 0.8 mol of reduced Cr(VI) per mole of iron. It was also found that this composite material can be easily regenerated and reused for Cr(VI) reduction without significant loss of efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

On line automated system for the determination of Sb(V), Sb(III), thrimethyl antimony(v) and total antimony in soil employing multisyringe flow injection analysis coupled to HG-AFS.

PubMed

Silva Junior, Mario M; Portugal, Lindomar A; Serra, Antonio M; Ferrer, Laura; Cerdà, Victor; Ferreira, Sergio L C

2017-04-01

This paper proposes the use of a multisyringe flow injection analysis (MSFIA) system for inorganic antimony speciation analysis, trimethyl antimony(V) and determination of total antimony in soil samples using hydride generation atomic fluorescence spectrometry (HG-AFS). Total antimony has been determined after reduction of antimony(V) to antimony(III) using potassium iodide and ascorbic acid. For determination of total inorganic antimony the sample is percolated in a mini-column containing the Dowex 50W-X8 resin for retention of the organic species of antimony. Antimony(III) is quantified in presence of 8-hydroxyquinoline as masking agent for antimony(V) after an extraction step of the organic antimony species using the also same mini-column. The trimethyl antimony(V) content is found by difference between total antimony and total inorganic antimony. By other hand, antimony(V) is quantified by difference between total inorganic antimony and antimony(III). The analytical determinations were performed using sodium tetrahydroborate as reducing agent. The optimization step was performed using two-level full factorial design and Doehlert matrix involving the factors: hydrochloric acid and sodium tetrahydroborate concentrations and sample flow rate. The optimized experimental conditions allow the antimony determination utilizing the external calibration technique with limits of detection and quantification of 0.9 and 3.1ngg -1 , respectively, and a precision expressed as relative standard deviation of 3.2% for an antimony solution of 5.0µgL -1 . The method accuracy was confirmed by analysis of the soil certified reference material furnished from Sigma-Aldrich RTC. Additionally, addition/recovery tests were performed employing synthetic solutions prepared using trimethyl antimony(V), antimony(III), antimony(V) and five soil samples. The antimony extraction step was performed in a closed system using hydrochloric acid, ultrasonic radiation and controlled temperature. The method proposed was applied for analysis of thirteen soil samples collected in different sites of the Balearic Islands, Spain, and the results obtained varied from 19 to 46ngg -1 for trimethyl antimony(V) and from 113 to 215ngg -1 for total inorganic antimony. The concentrations obtained to antimony(V) were always higher than for antimony(III) in all the analyzed samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigations regarding the wet decontamination of fluorescent lamp waste using iodine in potassium iodide solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tunsu, Cristian, E-mail: tunsu@chalmers.se; Ekberg, Christian; Foreman, Mark

Highlights: • A wet-based decontamination process for fluorescent lamp waste is proposed. • Mercury can be leached using iodine in potassium iodide solution. • The efficiency of the process increases with an increase in leachant concentration. • Selective leaching of mercury from rare earth elements is achieved. • Mercury is furthered recovered using ion exchange, reduction or solvent extraction. - Abstract: With the rising popularity of fluorescent lighting, simple and efficient methods for the decontamination of discarded lamps are needed. Due to their mercury content end-of-life fluorescent lamps are classified as hazardous waste, requiring special treatment for disposal. A simplemore » wet-based decontamination process is required, especially for streams where thermal desorption, a commonly used but energy demanding method, cannot be applied. In this study the potential of a wet-based process using iodine in potassium iodide solution was studied for the recovery of mercury from fluorescent lamp waste. The influence of the leaching agent’s concentration and solid/liquid ratio on the decontamination efficiency was investigated. The leaching behaviour of mercury was studied over time, as well as its recovery from the obtained leachates by means of anion exchange, reduction, and solvent extraction. Dissolution of more than 90% of the contained mercury was achieved using 0.025/0.05 M I{sub 2}/KI solution at 21 °C for two hours. The efficiency of the process increased with an increase in leachant concentration. 97.3 ± 0.6% of the mercury contained was dissolved at 21 °C, in two hours, using a 0.25/0.5 M I{sub 2}/KI solution and a solid to liquid ratio of 10% w/v. Iodine and mercury can be efficiently removed from the leachates using Dowex 1X8 anion exchange resin or reducing agents such as sodium hydrosulphite, allowing the disposal of the obtained solution as non-hazardous industrial wastewater. The extractant CyMe{sub 4}BTBP showed good removal of mercury, with an extraction efficiency of 97.5 ± 0.7% being achieved in a single stage. Better removal of mercury was achieved in a single stage using the extractants Cyanex 302 and Cyanex 923 in kerosene, respectively.« less

Simple new method for effective concentration of 188Re solutions from alumina-based 188W-188Re generator.

PubMed

Guhlke, S; Beets, A L; Oetjen, K; Mirzadeh, S; Biersack, H J; Knapp, F F

2000-07-01

(188)Re is a useful generator-produced radioisotope currently under evaluation for a variety of therapeutic applications, including bone pain palliation and intravascular radiation therapy. Because the (188)W parent is available only in a relatively low specific activity (<0.15-0.19 GBq/mg) from reactor irradiation of enriched (186)W, relatively large volumes of 0.9% saline (>15 mL) are required for elution of the (188)Re daughter from traditional alumina-based (188)W-(188)Re generators. Because these large bolus volumes result in solutions with a relatively low specific volume activity of (188)Re (<1 GBq/mL for the 18.5-GBq generator), the availability of effective methods for eluent concentration is important. Our new approach is based on the use of 0.3 mol/L ammonium acetate as a representative salt of a weak acid instead of saline for generator elution. After generator elution, the ammonium acetate generator eluent (15-20 mL) is passed through a tandem IC-H Plus cation (Dowex-H)-anion (QMA Light) column system. Exchange of ammonium cations with hydrogen ions on the cation column forms an acetic acid solution containing perrhenate anions from which the macroscopic levels of the acetate anion of the eluent have been effectively removed. Because perrhenic acid is fully dissociated at this pH, the QMA Light column specifically traps the (188)Re-perrhenate, which is subsequently eluted with a low volume (<1 mL) of saline. Concentration ratios greater than 20:1 are readily achieved with this method. A typical clinical-scale generator loaded with 19.2 GBq (188)W was used to validate the approach. Saline elution provided (188)Re in a 75%-80% yield. Although elution with 0.15 mol/L NH4OAc gave lower yields (55%-60%), use of 0.3 mol/L NH4OAc provided yields comparable with those of saline (70%-75%). (188)W parent breakthrough was not detected after passage of the bolus through the tandem concentration system. Bolus volumes of 15-20 mL, which initially contained as much as 11.1-14.8 GBq (188)Re, were readily concentrated to less than 1 mL saline using QMA Light cartridges. The generator was evaluated for more than 3 mo with no decrease in performance. This approach represents a simple, rapid, and effective method using inexpensive disposable components of concentrating solutions of (188)Re for preparation of therapeutic agents.

SEMIANNUAL PROGRESS REPORT ON CHEMISTRY FOR THE PERIOD, JANUARY 1961-JULY 1961

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1962-03-01

A procedure is presented for the determination of both Mo and Sn in a wide variety of samples with 8-quinolinol (oxine). The Mo complex is extracted with chloroform from a sulfate solution of the sample at pH 0.85 and determined spectrophotometrically at 385 m mu . The Sn complex is then similarly extracted and determined after the addition of chloride to the sample solution. A procedure is also given in which B is separated quantitatively from various B minerals by pyrohydrolysis. The distillate is passed through a cation-exchange resin column to remove interfering Sr, Ru, and other cations, after whichmore » the effluent is neutralized to pH 9.3 tc 9.4 and evaporated to dryness. The residue is suitable for the mass spectrometric determination of the B/sup 11//B/sup 10/ ratio. In other work, a single-focusing mass spectrometer of 6-in. radius, 60 deg sector magnetic analyzer was designed to analyze a wide range of sample materials that require high precision and accuracy in the low-mass range but which offers considerable flexibility to evaluate highmass materials for comparison purposes. A gas, solid, or liquid type of analysis may be performed. A change-over can be raade from one type of analysis to another with minimum loss of instrument tirae and requiring minimum technical knowledge. Single peak measurement, or ratio measurement may be made from M/e 6/7 to M/e 238/235, with the use of vibrating reed electrometers or an electron multiplier for measuring the ion beams. The stability of plutonium sulfate tetrshydrate and anhydrous plutonium sulfate was evaluated. Recent tests disclose no signlficant change in the Pu content of the tetrahydrate or the anhydrous salt for periods of at least 18 and 6 months, respectively. Both thermogravimetry and chemical analysis showed the formula of anhydrous plutonium sulfate to be Pu(SO/sub 4/)/sub 2.000/ / sub plus or minus / /sub 0.002/. Preparation of dicesium plutoniu m hexachloride is reported along with evaluation of its suitability as a primary standard for Pu. The composition of the material was determined by analysis and fits the formula susceptible to changes in relative humidities greater than 17%, and showed a small but significant weight loss during a six-month testing period. A procedure is described for Si separation from Pu using a cation-exchange procedure prior to spectrographic determination. Plutonium(III) in 0.2N nitric acid is adsorbed on Dowex-50 cation resin while Si, as silicate anion or colloid, passes unadsorbed into the effluent. The effluent is evaporated to dryness and the residue is dissolved in dilute nitric acid containing hydrofluoric acid. Aliquots of the solution are dried on graphite electrodes and excited in a d-c arc. Typical results on synthetic solutions give an estimated over-all average deviation of plus or minus 25% and sensitivities from 1 to 5 ppm Si. This method offers an alternate procedure to the carrier distillation technique which employs large amounts of PuO/sub 2/ as matrix for the determination of Si in Pu. The development of a sensitive method for the spectrographic determination of trace impurities in Pu is continuing. The method was modified for use with plutonium sulfate samples, and enlarged to include the determination of B, Cd, and some alkali elements, and also for the estimation of Am. Pu breakthrough during the ion-exchange separation of Pu from its impurities was found to be < 0.001%. Methods were investigated for preparing high-purity reagents and reducing reference blank values in order to obtain greater sensitivity. At present seventeen elements may be determined in the 1st and 2nd optical orders using only 200 mg. of sample. (auth)« less

Fast Pyrolysis Oil Stabilization: An Integrated Catalytic and Membrane Approach for Improved Bio-oils. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

George W. Huber; Upadhye, Aniruddha A.; Ford, David M.

This University of Massachusetts, Amherst project, "Fast Pyrolysis Oil Stabilization: An Integrated Catalytic and Membrane Approach for Improved Bio-oils" started on 1st February 2009 and finished on August 31st 2011. The project consisted following tasks: Task 1.0: Char Removal by Membrane Separation Technology The presence of char particles in the bio-oil causes problems in storage and end-use. Currently there is no well-established technology to remove char particles less than 10 micron in size. This study focused on the application of a liquid-phase microfiltration process to remove char particles from bio-oil down to slightly sub-micron levels. Tubular ceramic membranes of nominalmore » pore sizes 0.5 and 0.8m were employed to carry out the microfiltration, which was conducted in the cross-flow mode at temperatures ranging from 38 to 45 C and at three different trans-membrane pressures varying from 1 to 3 bars. The results demonstrated the removal of the major quantity of char particles with a significant reduction in overall ash content of the bio-oil. The results clearly showed that the cake formation mechanism of fouling is predominant in this process. Task 2.0 Acid Removal by Membrane Separation Technology The feasibility of removing small organic acids from the aqueous fraction of fast pyrolysis bio-oils using nanofiltration (NF) and reverse osmosis (RO) membranes was studied. Experiments were carried out with a single solute solutions of acetic acid and glucose, binary solute solutions containing both acetic acid and glucose, and a model aqueous fraction of bio-oil (AFBO). Retention factors above 90% for glucose and below 0% for acetic acid were observed at feed pressures near 40 bar for single and binary solutions, so that their separation in the model AFBO was expected to be feasible. However, all of the membranes were irreversibly damaged when experiments were conducted with the model AFBO due to the presence of guaiacol in the feed solution. Experiments with model AFBO excluding guaiacol were also conducted. NF membranes showed retention factors of glucose greater than 80% and of acetic acid less than 15% when operated at transmembrane pressures near 60 bar. Task 3.0 Acid Removal by Catalytic Processing It was found that the TAN reduction in bio-oil was very difficult using low temperature hydrogenation in flow and batch reactors. Acetic acid is very resilient to hydrogenation and we could only achieve about 16% conversion for acetic acid. Although it was observed that acetic acid was not responsible for instability of aqueous fraction of bio-oil during ageing studies (described in task 5). The bimetallic catalyst PtRe/ceria-zirconia was found to be best catalyst because its ability to convert the acid functionality with low conversion to gas phase carbon. Hydrogenation of the whole bio-oil was carried out at 125°C, 1450 psi over Ru/C catalyst in a flow reactor. Again, negligible acetic acid conversion was obtained in low temperature hydrogenation. Hydrogenation experiments with whole bio-oil were difficult to perform because of difficulty to pumping the high viscosity oil and reactor clogging. Task 4.0 Acid Removal using Ion Exchange Resins DOWEX M43 resin was used to carry out the neutralization of bio-oil using a packed bed column. The pH of the bio-oil increased from 2.43 to 3.7. The GC analysis of the samples showed that acetic acid was removed from the bio-oil during the neutralization and recovered in the methanol washing. But it was concluded that process would not be economical at large scale as it is extremely difficult to regenerate the resin once the bio-oil is passed over it. Task 5.0 Characterization of Upgraded Bio-oils We investigated the viscosity, microstructure, and chemical composition of bio-oils prepared by a fast pyrolysis approach, upon aging these fuels at 90ºC for periods of several days. Our results suggest that the viscosity increase is not correlated with the acids or char present in the bio-oils. The viscosity increase is due to formation of high molecular weight polymeric species over time. Our work also suggests that hydrogenation of the samples is beneficial in eliminating the viscosity increase. Task 6.0 Commercialization Assessment Renewable Oil International LLC (ROI) was responsible for Task 6.0, Commercialization Assessment. As part of this effort ROI focused on methods to reduce char carryover in the vapor stream from the fast pyrolysis reactor and residence time of the vapor in the reactor. Changes were made in the bio-oil recovery methodology and a reactor sweep gas used to reduce vapor residence time. Cyclones were placed in the vapor stream to reduce char particulate carryover. Microfiltration of the bio-oil was also researched to remove char particulate from the bio-oil. The capital cost for these improvements would be less than 2% of the total plant capital cost.« less