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1

STABILITY INDICATING RP-HPLC METHOD FOR SIMULTANEOUS DETERMINATION OF VALSARTAN AND AMLODIPINE FROM THEIR COMBINATION DRUG PRODUCT  

Microsoft Academic Search

A simple, precise and accurate stability indicating RP-HPLC method has been developed and subsequently validated for simultaneous estimation of Valsartan (VAL) and Amlodipine (AML) from their combination dosage form. A Shimadzu's HPLC (LC-2010-HT, Shimadzu, Singapore) equipped with UV-Visible and Diode Array detectors, with Class-VP software was used. Column used was XTerra ® RP18, 5 µm, 150 mm × 4.6 mm

SNEHAL B. PATEL; BHARAT G. CHAUDHARI; MUNISH K. BUCH; ASHOK B. PATEL; Shree S. K. Patel; Shree B. M. Shah

2

A Stability-Indicating RP-HPLC Assay Method for 5-Fluorouracil  

PubMed Central

The present study describes the development of a validated RP-HPLC method for the determination of 5-fluorouracil in presence of its degradation products or other pharmaceutical excipients. Stress studies were performed on 5-fluorouracil and it was found that it degrades sufficiently in alkaline conditions, while negligible degradation was observed in acidic, neutral, oxidative and photolytic conditions. The peaks of the degradation products were not observed in the chromatogram due to the nonchromophoric nature of the degradation moiety formed. The separations were carried out on a C-18 reversed phase column (Phenomenex; Prodigy ODS3V, 250×4.6 mm, 5 ?) using 50mM KH2PO4 (pH, 5.0) as mobile phase at a flow rate of 1.2 ml/min and temperature of 30°. The wavelength of detection was 254 nm. A retention time of nearly 6 minutes was obtained. Analytical validation parameters such as specificity and selectivity, linearity, accuracy and precision were evaluated. The calibration curve for 5-fluorouracil was linear (r2=0.999±0.0005) from range of 10 ?g/ml to 100 ?g/ml. Relative standard deviation values for all the key parameters, was less than 2.0 %. The recovery of the drug after standard addition to the degraded sample was found to be 104.69%. Thus, the developed RP-HPLC method was found to be suitable for the determination of 5-fluorouracil in bulk as well as stability samples of the pharmaceutical dosage forms containing various excipients.

Sinha, V. R.; Kumar, R. V.; Bhinge, J. R.

2009-01-01

3

A Stability-Indicating RP-HPLC Assay Method for 5-Fluorouracil.  

PubMed

The present study describes the development of a validated RP-HPLC method for the determination of 5-fluorouracil in presence of its degradation products or other pharmaceutical excipients. Stress studies were performed on 5-fluorouracil and it was found that it degrades sufficiently in alkaline conditions, while negligible degradation was observed in acidic, neutral, oxidative and photolytic conditions. The peaks of the degradation products were not observed in the chromatogram due to the nonchromophoric nature of the degradation moiety formed. The separations were carried out on a C-18 reversed phase column (Phenomenex; Prodigy ODS3V, 250x4.6 mm, 5 mu) using 50mM KH(2)PO(4) (pH, 5.0) as mobile phase at a flow rate of 1.2 ml/min and temperature of 30 degrees . The wavelength of detection was 254 nm. A retention time of nearly 6 minutes was obtained. Analytical validation parameters such as specificity and selectivity, linearity, accuracy and precision were evaluated. The calibration curve for 5-fluorouracil was linear (r(2)=0.999+/-0.0005) from range of 10 mug/ml to 100 mug/ml. Relative standard deviation values for all the key parameters, was less than 2.0 %. The recovery of the drug after standard addition to the degraded sample was found to be 104.69%. Thus, the developed RP-HPLC method was found to be suitable for the determination of 5-fluorouracil in bulk as well as stability samples of the pharmaceutical dosage forms containing various excipients. PMID:20376215

Sinha, V R; Kumar, R V; Bhinge, J R

2009-11-01

4

Stability-indicating RP-HPLC method for the simultaneous determination of escitalopram oxalate and clonazepam.  

PubMed

The objective of the current study was to develop a validated, specific stability-indicating reversed-phase liquid chromatographic (LC) method for the quantitative determination of escitalopram oxalate and clonazepam and their related substances in bulk drugs and pharmaceutical dosage forms in the presence of degradation products. Forced degradation studies were performed on the pure drugs of escitalopram oxalate and clonazepam, as per the stress conditions prescribed by the International Conference on Harmonization (ICH) using acid, base, oxidation, thermal stress and photolytic degradation to show the stability-indicating power of the method. Significant degradation was observed during acid and alkaline hydrolysis and no degradation was observed in other stress conditions. The chromatographic method was optimized using the samples generated from forced degradation studies. Good resolution between the peaks corresponded to the active pharmaceutical ingredients, escitalopram oxalate and clonazepam, and degradation products from the analyte were achieved on an ODS Hypersil C18 column (250 × 4.6 mm) using a mobile phase consisting of a mixture of acetonitrile-50 mM phosphate buffer + 10 mM triethylamine (70:30, v/v). The detection was conducted at 268 nm. The limit of detection and the limit of quantitation for escitalopram oxalate and clonazepam were established. The stress test solutions were assayed against the qualified working standards of escitalopram oxalate and clonazepam, which indicated that the developed LC method was stability-indicating. Validation of the developed LC method was conducted as per ICH requirements. The developed LC method was found to be suitable to check the quality of bulk samples of escitalopram oxalate and clonazepam. PMID:23135233

Kakde, Rajendra B; Satone, Dinesh D; Gadapayale, Kamalesh K; Kakde, Megha G

2012-11-07

5

New Stability Indicating RP-HPLC Method for the Estimation of Cefpirome Sulphate in Bulk and Pharmaceutical Dosage Forms  

PubMed Central

A simple stability indicating reversed-phase HPLC method was developed and subsequently validated for estimation of Cefpirome sulphate (CPS) present in pharmaceutical dosage forms. The proposed RP-HPLC method utilizes a LiChroCART-Lichrosphere100, C18 RP column (250 mm × 4mm × 5 ?m) in an isocratic separation mode with mobile phase consisting of methanol and water in the proportion of 50:50 % (v/v), at a flow rate 1ml/min, and the effluent was monitored at 270 nm. The retention time of CPS was 2.733 min and its formulation was exposed to acidic, alkaline, photolytic, thermal and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. The described method was linear over a range of 0.5–200?g/ml. The percentage recovery was 99.46. F-test and t-test at 95% confidence level were used to check the intermediate precision data obtained under different experimental setups; the calculated value was found to be less than the critical value.

Rao, Kareti Srinivasa; Kumar, Keshar Nargesh; Joydeep, Datta

2011-01-01

6

New Stability-Indicating RP-HPLC Method for Determination of Diclofenac Potassium and Metaxalone from their Combined Dosage Form  

PubMed Central

A simple, precise and accurate isocratic RP-HPLC stability-indicating assay method has been developed to determine diclofenac potassium and metaxalone in their combined dosage forms. Isocratic separation was achieved on a Hibar-C18, Lichrosphere-100® (250 mm × 4.6 mm i.d., particle size 5 ?m) column at room temperature in isocratic mode, the mobile phase consists of methanol: water (80:20, v/v) at a flow rate of 1.0 ml/min, the injection volume was 20 ?l and UV detection was carried out at 280nm. The drug was subjected to acid and alkali hydrolysis, oxidation, photolysis and heat as stress conditions. The method was validated for specificity, linearity, precision, accuracy, robustness and system suitability. The method was linear in the drug concentration range of 2.5–30 ?g/ml and 20–240 ?g/ml for diclofenac potassium and metaxalone, respectively. The precision (RSD) of six samples was 0.83 and 0.93% for repeatability, and the intermediate precision (RSD) among six-sample preparation was 1.63 and 0.49% for diclofenac potassium and metaxalone, respectively. The mean recoveries were between 100.99–102.58% and 99.97–100.01% for diclofenac potassium and metaxalone, respectively. The proposed method can be used successfully for routine analysis of the drug in bulk and combined pharmaceutical dosage forms.

Panda, Sagar Suman; Patanaik, Debasis; Ravi Kumar, Bera V. V.

2012-01-01

7

Development and Validation of a Novel Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Halometasone, Fusidic Acid, Methylparaben, and Propylparaben in Topical Pharmaceutical Formulation  

PubMed Central

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of halometasone, fusidic acid, methylparaben, and propylparaben in topical pharmaceutical formulation. The desired chromatographic separation was achieved on an Agilent Zorbax CN (Cyano), 5 ?m (250 × 4.6 mm) column using gradient elution at 240 nm detector wavelength. The optimized mobile phase consisted of a mixture of 0.01 M phosphate buffer and 0.1% orthophosphoric acid, pH-adjusted to 2.5 with an ammonia solution as solvent-A and acetonitrile as solvent-B. The developed method separated halometasone, fusidic acid, methylparaben, and propylparaben in the presence of known impurities/degradation products. The stability-indicating capability was established by forced degradation experiments and separation of known and unknown degradation products. The developed RP-HPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated method was applied for the simultaneous estimation of HM, FA, MP, and PP in commercially available cream samples. Further, the method can be extended for the estimation of HM, FA, MP, and PP in various commercially available dosage forms.

Goswami, Nishant; Gupta, V. Rama Mohan; Jogia, Hitesh A.

2013-01-01

8

A Rapid, Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Formoterol Fumarate, Tiotropium Bromide, and Ciclesonide in a Pulmonary Drug Product  

PubMed Central

A stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of Formoterol fumarate (FOR), Tiotropium bromide (TRI), and Ciclesonide (CLS) in a pulmonary drug product. The desired chromatographic separation was achieved on the Zorbax SB C8, 5 ?m (150 × 4.6 mm) column, using gradient elution at 230 nm detector wavelength. The optimized mobile phase consisted of a 0.2 % v/v perchloric acid as solvent-A and acetonitrile as solvent-B. The developed method separated FOR, TRI, and CLS in the presence of its five unknown degradation products within 10 minutes. The stability-indicating capability was established by forced degradation experiments and the separation of unknown degradation products. The developed RP-HPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated method was applied for the simultaneous estimation of FOR, TRI, and CLS in commercially available Triohale® pMDI (Pressurized Metered-Dose Inhaler) samples. Furthermore, this method can be extended for individual estimation of FOR, TRI, and CLS in various commercially available pulmonary dosage forms.

Trivedi, Rakshit Kanubhai; Chendake, Dhairyshil S.; Patel, Mukesh C.

2012-01-01

9

A Rapid, Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Formoterol Fumarate, Tiotropium Bromide, and Ciclesonide in a Pulmonary Drug Product.  

PubMed

A stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of Formoterol fumarate (FOR), Tiotropium bromide (TRI), and Ciclesonide (CLS) in a pulmonary drug product. The desired chromatographic separation was achieved on the Zorbax SB C8, 5 ?m (150 × 4.6 mm) column, using gradient elution at 230 nm detector wavelength. The optimized mobile phase consisted of a 0.2 % v/v perchloric acid as solvent-A and acetonitrile as solvent-B. The developed method separated FOR, TRI, and CLS in the presence of its five unknown degradation products within 10 minutes. The stability-indicating capability was established by forced degradation experiments and the separation of unknown degradation products. The developed RP-HPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated method was applied for the simultaneous estimation of FOR, TRI, and CLS in commercially available Triohale(®) pMDI (Pressurized Metered-Dose Inhaler) samples. Furthermore, this method can be extended for individual estimation of FOR, TRI, and CLS in various commercially available pulmonary dosage forms. PMID:23008808

Trivedi, Rakshit Kanubhai; Chendake, Dhairyshil S; Patel, Mukesh C

2012-05-22

10

Development of a Stability-Indicating RP-HPLC Method for the Determination of Rupatadine and its Degradation Products in Solid Oral Dosage Form  

PubMed Central

A simple, sensitive, and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method, coupled with a photodiode array detector, was developed for the determination of rupatadine (RUPA) and its related substances in pharmaceutical dosage forms. Chromatographic separation was achieved on the Hypersil BDS (150 x 4.6 mm, 5 ?m) column with a mobile phase containing a gradient mixture of a buffer (acetate buffer pH-6.0) and solvent (methanol). The eluted compounds were monitored at 264 nm for the related substances and assay, the flow rate was 1.0 mL/min, and the column oven temperature was maintained at 50°C. The developed method separated RUPA from its four known and three unknown impurities within 15.0 min. Rupatadine was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Rupatadine was found to degrade significantly under oxidative stress conditions, and degrade slightly under acid, base, hydrolytic, thermal, and photolytic stress conditions. All impurities were well-resolved from each other and from the main peak, showing the stability-indicating power of the method. The developed method was validated as per the International Conference on Harmonization (ICH) guidelines. The developed and validated RP-HPLC method is LC-MS compatible and can be explored for the identification of eluted unknown impurities of RUPA.

Trivedi, Harshal Kanubhai; Patel, Mukesh C.

2012-01-01

11

Development of a Stability-Indicating RP-HPLC Method for the Determination of Rupatadine and its Degradation Products in Solid Oral Dosage Form.  

PubMed

A simple, sensitive, and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method, coupled with a photodiode array detector, was developed for the determination of rupatadine (RUPA) and its related substances in pharmaceutical dosage forms. Chromatographic separation was achieved on the Hypersil BDS (150 x 4.6 mm, 5 ?m) column with a mobile phase containing a gradient mixture of a buffer (acetate buffer pH-6.0) and solvent (methanol). The eluted compounds were monitored at 264 nm for the related substances and assay, the flow rate was 1.0 mL/min, and the column oven temperature was maintained at 50°C. The developed method separated RUPA from its four known and three unknown impurities within 15.0 min. Rupatadine was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Rupatadine was found to degrade significantly under oxidative stress conditions, and degrade slightly under acid, base, hydrolytic, thermal, and photolytic stress conditions. All impurities were well-resolved from each other and from the main peak, showing the stability-indicating power of the method. The developed method was validated as per the International Conference on Harmonization (ICH) guidelines. The developed and validated RP-HPLC method is LC-MS compatible and can be explored for the identification of eluted unknown impurities of RUPA. PMID:23264938

Trivedi, Harshal Kanubhai; Patel, Mukesh C

2012-10-01

12

Validation of a Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Trimethoprim and Sulfadimethoxine Sodium in Oral Liquid Dosage Form.  

PubMed

A simple, specific, accurate, and stability-indicating RP-HPLC method was developed and validated for the simultaneous determination of Trimethoprim (TMP) and Sulfadimethoxine sodium (SDMS) in Vetricine(®) oral solution product. The desired separation was achieved on an ODS column (250×4.6 mm i.d., 5 ?m) at room temperature. The optimized mobile phase consisted of an isocratic solvent mixture of water:acetonitrile:triethylamine (700:299:1, v/v/v), adjusted to a pH of 5.7 ± 0.05 with 0.2N acetic acid. The mobile phase was fixed at 0.8 ml/min and the analytes were monitored at 254 nm using a photodiode array detector. The effects of the chromatographic conditions on the peaks USP tailing factor, column efficiency, and resolution were systematically optimized. Forced degradation experiments were carried out by exposing TMP, SDMS standards, and the oral solution formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The degradation products were well-resolved from the main peaks and the excipients, thus proving the reliable stability-indicating method. The method was validated as per ICH and USP guidelines (USP34/NF29) and found to be adequate for the routine quantitative estimation of TMP and SDMS in commercially available Vetricine® oral liquid dosage form. PMID:23833713

Ghanem, Mashhour M; Abu-Lafi, Saleh A

2013-02-18

13

Optimization and validation of a stability-indicating RP-HPLC method for determination of azithromycin and its related compounds.  

PubMed

A validated stability-indicating HPLC method was developed for the analysis of azithromycin (AZ) and its related compounds in raw materials, capsule, and suspension using an Xterra RP C18 column at 50 degrees C with UV detection at 215 nm. Isocratic elution was employed using the mobile phase 14 mM disodium hydrogen phosphate (pH 10.5, adjusted by 1 M NaOH)-methanol-acetonitrile-tetrahydrofuran (40.0 + 30.0 + 30.0 + 0.1, v/v/v/v). AZ and 14 of its related compounds were separated and quantified. The described method was linear over the range of 2-1800 microg/mL AZ with (r = 0.9999). The stability of AZ was studied under accelerated acidic, alkaline, and oxidative conditions. The proposed method was used to investigate the kinetics of acidic and alkaline hydrolysis process of AZ at different temperatures, and the apparent pseudo first-order rate constant, half-life, and activation energy were calculated. The major peak detected from the degradation of AZ in alkaline and acidic conditions was decladinosylazithromycine, while azithromycin N-oxide was detected from the oxidative degradation. Long-term stability studies for capsule and oral suspension were carried out. The proposed stability-indicating method was completely validated according to the U.S. Food and Drug Administration requirements. PMID:21563685

El-Gindy, Alaa; Attia, Khalid A; Nassar, Mohammad Wafaa; Al Abasawi, Nasr M; Al-Shabrawi, Maisra

14

Development and validation of a stability-indicating RP-HPLC method for the determination of paracetamol with dantrolene or\\/and cetirizine and pseudoephedrine in two pharmaceutical dosage forms  

Microsoft Academic Search

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all

Ghada M. Hadad; Samy Emara; Waleed M. M. Mahmoud

2009-01-01

15

Development and Validation of a Stability-Indicating RP-HPLC Method for the Quantitative Analysis of Anagrelide Hydrochloride  

PubMed Central

A simple, rapid, and stability-indicating reverse-phase liquid chromatographic assay method was developed for Anagrelide Hydrochloride (ANG) in the presence of its degradation products generated from forced decomposition studies. The HPLC separation was achieved on a C18 Inertsil column (250 mm × 4.6 mm i.d. particle size is 5 ?m), using solution A, a mixture of 0.03 M potassium di-hydrogen phosphate pH-adjusted to 3.0 using ortho-phosphoric acid (buffer): methanol: acetonitrile (90:5:5, v/v/v), and solution B, which contains a mixture of buffer: acetonitrile (10:90, v/v). The UV detector was operated at 251 nm while column temperature was maintained at 40°C, and the gradient program had the flow rate of 1.0 mL min?1. The developed method was validated as per ICH guidelines with respect to specificity, linearity, precision, accuracy, robustness, and limit of quantification. The method was found to be simple, specific, precise, accurate, and reproducible. Selectivity was validated by subjecting the stock solution of ANG to acidic, basic, photolysis, oxidative, and thermal degradation. The calibration curve was found to be linear in the concentration range of 0.05–152 ?g mL?1 (R2 = 0.9991). The peaks of degradation products did not interfere with that of pure ANG. The utility of the developed method was examined by analyzing the tablets containing ANG.

Pujeri, Sudhakar S.; Khader, Addagadde M. A.; Seetharamappa, Jaldappagari

2012-01-01

16

Development and Validation of a Stability-Indicating RP-HPLC Assay Method and Stress Degradation Studies on Dapiprazole.  

PubMed

Dapiprazole (DPZ) was subjected to different stress conditions prescribed by the International Conference on Harmonization. A stability-indicating high-performance liquid chromatography method was developed for the analysis of the drug in the presence of its degradation products. The degradation was found to occur in hydrolytic, and to some extent, photolytic conditions, however, the drug was stable to oxidative and thermal stress. The drug was particularly labile under neutral and alkaline hydrolytic conditions. The assay was involved an isocratic elution of DPZ in a Kromasil 100C18 column using a mobile phase composition of water (pH 6.5, 0.05%, w/v, 1-heptane sulfonic acid) and acetonitrile (40:60, v/v). The flow rate was 0.8 mL/min and the detection was conducted at 246 nm. The assay method was found to be linear from 5 to 30 µg/mL. The method was validated for linearity, range, precision, accuracy, specificity, selectivity, limit of detection and limit of quantitation. PMID:23169931

Ramesh, Thippani; Rao, Pothuraju Nageswara

2012-11-20

17

Development and validation of a stability-indicating RP-HPLC method for the determination of paracetamol with dantrolene or/and cetirizine and pseudoephedrine in two pharmaceutical dosage forms.  

PubMed

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all the degradant peaks. A gradient mobile phase system consisting of (A) 50 mmol L(-1) sodium dihydrogen phosphate, 5 mmol L(-1) heptane sulfonic acid sodium salt, pH 4.2 and (B) acetonitrile was used with Discovery reversed-phase HS C(18) analytical column (250 mm x 4.6 mm i.d., 5 microm particle size). Quantitation was achieved with UV detection at 214 nm, based on peak area. The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the two multicomponent combinations. PMID:19635371

Hadad, Ghada M; Emara, Samy; Mahmoud, Waleed M M

2009-06-09

18

A validated stability-indicating RP-HPLC method for levofloxacin in the presence of degradation products, its process related impurities and identification of oxidative degradant.  

PubMed

The objective of current study was to develop a validated specific stability indicating reversed-phase liquid chromatographic method for the quantitative determination of levofloxacin as well as its related substances determination in bulk samples, pharmaceutical dosage forms in the presence of degradation products and its process related impurities. Forced degradation studies were performed on bulk sample of levofloxacin as per ICH prescribed stress conditions using acid, base, oxidative, water hydrolysis, thermal stress and photolytic degradation to show the stability indicating power of the method. Significant degradation was observed during oxidative stress and the degradation product formed was identified by LCMS/MS, slight degradation in acidic stress and no degradation was observed in other stress conditions. The chromatographic method was optimized using the samples generated from forced degradation studies and the impurity spiked solution. Good resolution between the peaks corresponds to process related impurities and degradation products from the analyte were achieved on ACE C18 column using the mobile phase consists a mixture of 0.5% (v/v) triethyl amine in sodium dihydrogen orthophosphate dihydrate (25 mM; pH 6.0) and methanol using a simple linear gradient. The detection was carried out at 294 nm. The limit of detection and the limit of quantitation for the levofloxacin and its process related impurities were established. The stressed test solutions were assayed against the qualified working standard of levofloxacin and the mass balance in each case was in between 99.4 and 99.8% indicating that the developed LC method was stability indicating. Validation of the developed LC method was carried out as per ICH requirements. The developed LC method was found to be suitable to check the quality of bulk samples of levofloxacin at the time of batch release and also during its stability studies (long term and accelerated stability). PMID:19632800

Lalitha Devi, M; Chandrasekhar, K B

2009-06-06

19

Stability-indicating method for simultaneous estimation of olmesartan medoxomile, amlodipine besylate and hydrochlorothiazide by RP-HPLC in tablet dosage form.  

PubMed

A simple, specific, accurate and precise stability-indicating reversed-phase high-performance liquid chromatographic method was developed for simultaneous estimation of olmesartan medoxomile (OLME), amlodipine besylate (AMLO) and hydrochlorothiazide (HCTZ) in tablet dosage form. The method was developed using an RP C18 base deactivated silica column (250 × 4.6 mm, 5 µm) with a mobile phase consisting of triethylamine (pH 3.0) adjusted with orthophosphoric acid (A) and acetonitrile (B), with a timed gradient program of T/%B: 0/30, 7/70, 8/30, 10/30 with a flow rate of 1.4 mL/min. Ultraviolet detection was used at 236 nm. The retention times for OLME, AMLO and HCTZ were found to be 6.72, 4.28 and 2.30, respectively. The proposed method was validated for precision, accuracy, linearity, range, robustness, ruggedness and force degradation study. The calibration curves of OLME, AMLO and HCTZ were linear over the range of 50-150, 12.5-37.5 and 31-93 µg/mL, respectively. The method was found to be sensitive. The limits of detection of OLME, AMLO and HCTZ were determined 0.19, 0.16 and 0.22 µg/mL and limits of quantification of OLME, AMLO and HCTZ were determined 0.57, 0.49 and 0.66, respectively. Forced degradation study was performed according to International Conference on Harmonization guidelines. PMID:22593253

Jain, P S; Patel, M K; Gorle, A P; Chaudhari, A J; Surana, S J

2012-05-16

20

Development and Validation of a Stability-Indicating RP-HPLC Method for the Determination of Process-Related Impurities and Degradation Products of Rabeprazole Sodium in Pharmaceutical Formulation  

PubMed Central

The objective of the current study was to develop and validate a reversed-phase high-performance liquid chromatographic method for the quantitative determination of process-related impurities and degradation products of rabeprazole sodium in pharmaceutical formulation. Chromatographic separation was achieved on the Waters Symmetry Shield RP18 (250 mm × 4.6 mm) 5 ?m column with a mobile phase containing a gradient mixture of solvent A (mixture of 0.025 M KH2PO4 buffer and 0.1% triethylamine in water, pH 6.4 and acetonitrile in the ratio of 90:10 v/v, respectively) and solvent B (mixture of acetonitrile and water in the ratio of 90:10 v/v, respectively). The mobile phase was delivered at a flow rate of 1.0 mL/min and with UV detection at 280 nm. Rabeprazole sodium was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Rabeprazole sodium was found to degrade significantly under acid hydrolysis, base hydrolysis, oxidative, and thermal degradation conditions. The degradation products were well-resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. The mass balance was found to be in the range of 97.3–101.3% in all of the stressed conditions, thus proving the stability-indicating power of the method. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, and robustness.

Kumar, Navneet; Sangeetha, Dhanaraj

2013-01-01

21

Development and Validation of a Stability-Indicating RP-HPLC Method for the Determination of Process-Related Impurities and Degradation Products of Rabeprazole Sodium in Pharmaceutical Formulation.  

PubMed

The objective of the current study was to develop and validate a reversed-phase high-performance liquid chromatographic method for the quantitative determination of process-related impurities and degradation products of rabeprazole sodium in pharmaceutical formulation. Chromatographic separation was achieved on the Waters Symmetry Shield RP18 (250 mm × 4.6 mm) 5 ?m column with a mobile phase containing a gradient mixture of solvent A (mixture of 0.025 M KH2PO4 buffer and 0.1% triethylamine in water, pH 6.4 and acetonitrile in the ratio of 90:10 v/v, respectively) and solvent B (mixture of acetonitrile and water in the ratio of 90:10 v/v, respectively). The mobile phase was delivered at a flow rate of 1.0 mL/min and with UV detection at 280 nm. Rabeprazole sodium was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Rabeprazole sodium was found to degrade significantly under acid hydrolysis, base hydrolysis, oxidative, and thermal degradation conditions. The degradation products were well-resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. The mass balance was found to be in the range of 97.3-101.3% in all of the stressed conditions, thus proving the stability-indicating power of the method. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, and robustness. PMID:24106668

Kumar, Navneet; Sangeetha, Dhanaraj

2013-03-17

22

UV derivative spectrophotometric and RP-HPLC methods for determination of imidapril hydrochloride in tablets and for its stability assessment in solid state.  

PubMed

Two methods for determination of imidapril hydrochloride (IMD) in the form of tablets were developed and the stability-indicative determination of IMD in solid state formulations by means of the proposed methods was investigated. IMD is not a pharmacopeial raw material, therefore there is no official method for its determination and purity assessment. The following analytical techniques were adopted for IMD determination: reverse-phase high performance liquid chromatography (RP-HPLC) and first derivative (1D) ultraviolet spectrophotometry. RP-HPLC analysis was performed with the use of LiChrosfer RP-18 column as a stationary phase and acetonitrile-methanol-phosphate buffer pH 2.0 (60:10:30 v/v/v) as a mobile phase. The proposed method showed good linearity (in a range 40.0 - 400.0 microg/mL), accuracy, precision and selectivity for: IMD, its degradation product, and for oxymetazoline as an internal standard (IS). Additionally, different spectrophotometric methods were tested, and the first derivative spectrophotometry was accepted for further research. This method showed good linearity (in a range 4.0 - 40.0 microg/mL), precision and accuracy. The proposed methods were successfully applied to the pharmaceutical dosage form containing the investigated compound without any interference from the excipients. Finally, the results of the suggested methods were statistically compared using t-Student and F-Snedecor tests in the assessment for their equivalence. PMID:21928708

Stanisz, Beata; Regulska, Katarzyna; Kolasa, Kinga

23

An RP-HPLC determination of 5-hydroxymethylfurfural in honey  

Microsoft Academic Search

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of

Nadia Spano; Lucia Casula; Angelo Panzanelli; Maria I. Pilo; Paola C. Piu; Roberta Scanu; Andrea Tapparo; Gavino Sanna

2006-01-01

24

Concurrent Estimation of Clopidogrel Bisulfate and Aspirin in Tablets by Validated RP-HPLC Method  

PubMed Central

A simple, rapid, precise RP-HPLC method was developed for simultaneous estimation of aspirin and clopidogrel bisulphate in tablet dosage form used in the treatment of cardiovascular diseases. To achieve the maximum resolution, acetonitrile:50 mM potassium dihydrogen phosphate buffer:methanol, solution pH adjusted to 3, in the ratio 50:30:20; v/v was selected as mobile phase. This mixture was found to be appropriate allowing good separation of both the components at a flow rate of 1.5 ml/min and detection wavelength 240 nm. In these conditions clopidogrel bisulfate and aspirin were eluated at the 7.47 and 2.2 min. The linearity was found in the concentration range 1.5-7.5 and 3.5-15.0 ?g/ml, respectively. All the analytical validation parameters were determined and found with in the limit as per ICH guideline, which indicates the validity of method.

Shrivastava, P. K.; Basniwal, P. K.; Jain, Deepti; Shrivastava, S. K.

2008-01-01

25

In vitro interaction studies of diltiazem with NSAID's using UV spectrophotometry and RP-HPLC techniques.  

PubMed

Diltiazem (DTZ) is a well-known cardiovascular drug used clinically in the treatment of angina pectoris and hypertension. Present paper deals with the in vitro availability studies of DTZ in presence of commonly used nonsteroidal anti-inflammatory drugs (NSAID's) like diclofenac sodium, flurbiprofen, mefenamic acid and meloxicam. Simultaneous administration of both types of drugs may alter the antihypertensive effect of DTZ. These studies were carried out using BP 2005 dissolution test apparatus in simulated human body environments at body temperature and at elevated temperature in order to study the kinetics and energitics of these interactions. Both the drug in each case were analyzed either by measuring the absorbance of aliquots on a UV/VIS spectrophotometer, or by RP-HPLC method. Present study clearly indicated that most of the NSAID's studied bind to DTZ forming charge transfer complexes, evident from the high availability of DTZ. Hence, concurrent administration of NSAID's with DTZ is not recommended. PMID:17545105

Sultana, Najma; Arayne, M Saeed; Shafi, Nighat

2007-07-01

26

Intra-specific genetic relationship analyses of Elaeagnus angustifolia based on RP-HPLC biochemical markers.  

PubMed

Elaeagnus angustifolia Linn. has various ecological, medicinal and economical uses. An approach was established using RP-HPLC (reversed-phase high-performance liquid chromatography) to classify and analyse the intra-specific genetic relationships of seventeen populations of E. angustifolia, collected from the Xinjiang areas of China. Chromatograms of alcohol-soluble proteins produced by seventeen populations of E. angustifolia, were compared. Each chromatogram of alcohol-soluble proteins came from a single seed of one wild plant only. The results showed that when using a Waters Delta Pak. C18, 5 microm particle size reversed phase column (150 mm x 3.9 mm), a linear gradient of 25%-60% solvent B with flow rate of 1 ml/min and run time of 67 min, the chromatography yielded optimum separation of E. angustifolia alcohol-soluble proteins. Representative peaks in each population were chosen according to peak area and occurrence in every seed. The converted data on the elution peaks of each population were different and could be used to represent those populations. GSC (genetic similarity coefficients) of 41% to 62% showed a medium degree of genetic diversity among the populations in these eco-areas. Cluster analysis showed that the seventeen populations of E. angustifolia could be divided into six clusters at the GSC=0.535 level and indicated the general and unique biochemical markers of these clusters. We suggest that E. angustifolia distribution in these eco-areas could be classified into six variable species. RP-HPLC was shown to be a rapid, repeatable and reliable method for E. angustifolia classification and identification and for analysis of genetic diversity. PMID:16532528

Wang, Qiang; Ruan, Xiao; Huang, Jun-hua; Xu, Ning-yi; Yan, Qi-chuan

2006-04-01

27

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey.  

PubMed

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0mgkg(-1), respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140mgkg(-1). PMID:18970477

Spano, Nadia; Casula, Lucia; Panzanelli, Angelo; Pilo, Maria I; Piu, Paola C; Scanu, Roberta; Tapparo, Andrea; Sanna, Gavino

2005-09-08

28

Concurrent Estimation of Clopidogrel Bisulfate and Aspirin in Tablets by Validated RP-HPLC Method.  

PubMed

A simple, rapid, precise RP-HPLC method was developed for simultaneous estimation of aspirin and clopidogrel bisulphate in tablet dosage form used in the treatment of cardiovascular diseases. To achieve the maximum resolution, acetonitrile:50 mM potassium dihydrogen phosphate buffer:methanol, solution pH adjusted to 3, in the ratio 50:30:20; v/v was selected as mobile phase. This mixture was found to be appropriate allowing good separation of both the components at a flow rate of 1.5 ml/min and detection wavelength 240 nm. In these conditions clopidogrel bisulfate and aspirin were eluated at the 7.47 and 2.2 min. The linearity was found in the concentration range 1.5-7.5 and 3.5-15.0 ?g/ml, respectively. All the analytical validation parameters were determined and found with in the limit as per ICH guideline, which indicates the validity of method. PMID:21394272

Shrivastava, P K; Basniwal, P K; Jain, Deepti; Shrivastava, S K

2008-09-01

29

[Isolation of plant insulin from Momordica charantia seeds by gel filtration and RP-HPLC].  

PubMed

Hypoglycemic polypeptide (PA) was extracted from Momordica charantia seeds with organic acid and ethanol and purified with Sephadex G-50 gel filtration and RP-HPLC. PA was judged as plant insulin on the base of the analysis of its SDS-PAGE electrophoresis and amino acid composition. PMID:15524293

Sheng, Qingkai; Yao, Huiyuan; Xu, Huajun; Ling, Xiaoyun; He, Ting

2004-06-01

30

RP-HPLC analysis for camptothecin content in Nothapodytes nimmoniana, an endangered medicinal plant  

Microsoft Academic Search

Studies were carried out on analysis of secondary metabolites by RP-HPLC from different parts (both in vitro and in vivo) of Nothpodytes nimmoniana, an endangered medicinal plant. HPLC analysis showed the presence of camptothecin, a medicinally important alkaloid from N. nimmoniana. The plant parts used for the analysis include leaves, seeds, seed coat and leaf derived callus. Among all the

Indramohan Singh; N. Kumaravadivel; R. Gnanam; S. Vellaikumar

31

New Determination Method for Sulfonation Degree of Phthalic Anhydride by RP-HPLC.  

PubMed

A novel method was developed to monitor the reaction process and evaluate the sulfonation level in the sulfonation of phthalic anhydride by reversed-phase high-performance liquid chromatography (RP-HPLC). The product peak was identified in chromatograms through product analysis and by comparing its retention time with that of standard compounds. By comparing the hydrolysis and alcoholysis methods, optimized pretreatment of the sample was found for RP-HPLC. Based on the determined percentages of phthalic anhydride and sulfonated phthalic anhydride in the mixture, the degree of sulfonation was calculated. When the sulfonation degree of phthalic anhydride was in the range of 2.8-71%, the recovery of 97-104% was achieved, and the procedure was rapid and accurate. PMID:23680900

Zhu, Lijun; Song, Lechun; Liu, Bin; Zhou, Yulu; Xiang, Yuzhi; Xia, Daohong

2013-05-16

32

SIMULTANEOUS ANALYSIS OF FLAVONOID AGLYCONES IN NATURAL PRODUCTS USING AN RP-HPLC METHOD  

Microsoft Academic Search

An RP-HPLC method for the simultaneous separation of the 16 main flavonoid aglycones and 3 important glycosides present in natural samples was developed. The separation was performed on a Supelcosil LC-318 column with eluants containing water, acetonitrile, and trifluoroacetic acid. The method was successfully applied to the analysis of propolis extract, a complex natural product containing flavonoid aglycones.Hydrolysis conditions able

P. Menghinello; L. Cucchiarini; F. Palma; D. Agostini; M. Dachà; V. Stocchi

1999-01-01

33

RP–HPLC and Capillary Electrophoresis of Subunits from Glutenin Isolated by SDS and Osborne Fractionation  

Microsoft Academic Search

The polypeptide subunits present in SDS-unextractable glutenin, the glutenin macropolymer (GMP) and the 70% (v\\/v) ethanol unextractable protein, the Osborne glutenin fraction, of various cultivars were separated by RP–HPLC and capillary electrophoresis (CE) under denaturing (urea and SDS, respectively) and reducing conditions. In addition, the SDS-extractable protein was separated by CE. HighMrglutenin subunits were well separated by CE, while the

P. L. Weegels; R. J. Hamer; J. D. Schofield

1995-01-01

34

New retention mechanism of mononucleotides with buffer concentrations in ion-suppressing RP-HPLC  

Microsoft Academic Search

HPLC separation of ionic samples tends to be more complicated and difficult to understand than that of non-ionic compounds.\\u000a On the other hand, band spacing is much more easily manipulated for ionic than for neutral samples. Ion-suppressing RP-HPLC\\u000a method was used with organic modifier and aqueous buffer solution. In this work, five mononucleotides of cytidine-5-monophosphate\\u000a (5?-CMP) disodium salt, uridine-5-monophosphate disodium

Ju Weon Lee; Kyung Ho Row

2001-01-01

35

RP-HPLC determination of water-soluble vitamins in honey  

Microsoft Academic Search

The assessment and validation of reliable analytical methods for the determination of vitamins in sugar-based matrices (e.g. honey) are still scarcely explored fields of research. This study proposes and fully validates a simple and fast RP-HPLC method for the simultaneous determination of five water-soluble vitamins (vitamin B2, riboflavin; vitamin B3, nicotinic acid; vitamin B5, pantothenic acid; vitamin B9, folic acid;

Marco Ciulu; Silvia Solinas; Ignazio Floris; Angelo Panzanelli; Maria I. Pilo; Paola C. Piu; Nadia Spano; Gavino Sanna

2011-01-01

36

Simultaneous estimation of phenolic acids in sea buckthorn ( Hippophaë rhamnoides) using RP-HPLC with DAD  

Microsoft Academic Search

A RP-HPLC-DAD method was developed and validated for the simultaneous analysis of nine phenolic acids including gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, salicylic acid, p-coumaric acid, cinnamic acid, caffiec acid and ferulic acid in sea buckthorn (SB) (Hippophaë rhamnoides) berries and leaves. The method was validated in terms of linearity, LOD, precision, accuracy and recovery and found to

Ranjith Arimboor; K. Sarin Kumar; C. Arumughan

2008-01-01

37

RP-HPLC analysis of phenolic antioxidant compound 6-gingerol from different ginger cultivars  

Microsoft Academic Search

The aim of this work was to assess the antioxidant capacity and phenolic content from the rhizomes of 12 ginger cultivars from different agro climatic zones of India. The quantities of phenolic compound 6-gingerol was determined with reverse phase high performance liquid chromatography (RP-HPLC) which was ranging from 0.1% to 0.2%. The antioxidant capacity was determined using DPPH (1,1-diphenyl-2-picrylhydrazyl) and

Nilesh Pawar; Sandeep Pai; Mansingraj Nimbalkar; Ghansham Dixit

2011-01-01

38

Heterogeneity of Caprine Beta-Casein Elucidated by RP-HPLC\\/MS: Genetic Variants and Phosphorylations  

Microsoft Academic Search

Casein variants occurring in milks from goats homozygous at the as1-Cn locus were separated and identified by an RP-HPLC\\/ESI-MS method. Preferential haplotypes arose as well as some particularities in posttranslational modifications. A new variant of caprine ß-Cn, named C, as well as the phosphorylations pattern of the protein were characterized by the combined use of peptide mass fingerprinting and sequencing

Carole Neveu; Daniel Mollé; Javier Moreno; Patrice Martin; Joëlle Léonil

2002-01-01

39

HILIC for separation of co-eluted flavonoids under RP-HPLC mode.  

PubMed

Hydrophilic interaction chromatography (HILIC) was employed to separate the co-eluted flavonoids from licorice extract under RP-HPLC mode. HILIC separations were carried out with the Atalantis HILIC Silica column and the CD-based column. The co-eluted flavonoids were well retained and separated on the two HILIC columns under HILIC mode. Similar results were obtained in the separation of another isoflavones sample, from kudzu extract under HILIC mode. PMID:18428179

Zhang, Hui; Guo, Zhimou; Zhang, Feifang; Xu, Qing; Liang, Xinmiao

2008-05-01

40

Salt-induced phase separation can effectively remove the acetonitrile from the protein sample after the preparative RP-HPLC  

Microsoft Academic Search

Acetonitrile (ACN)–water system is one of the most commonly used mobile phases in practical reverse-phase high-performance liquid chromatography (RP-HPLC). However, a higher concentration of ACN (normally greater than 60% (v\\/v)) is required to elute the target protein from the RP-HPLC column in which, further steps to remove the ACN from the protein samples are demanded. It has been demonstrated that

Yesong Gu; Po-Hung Shih

2004-01-01

41

Rapid Isolation of Nanogram Amounts of Crustacean Erythrophore Concentrating Hormone from Invertebrate Nerve Tissue by RP-HPLC  

Microsoft Academic Search

A reverse phase-high performance liquid chromatography (rp-hplc) method was developed for the rapid isolation of nanogram amounts of crustacean erythrophore concentrating hormone (CECH) from invertebrate nerve tissue. Tissue homogenates from the shrimp, Paleomenetes pugio, were subjected to a multistep work-up to remove proteins and lipids prior to analysis by rp-hplc. Samples were eluted with a concave gradient of 0.1% trifluoroacetic

Howard Jaffe; Marcia Loeb; Dora K. Hayes; Nancy Holston

1982-01-01

42

Development and Validation of a Specific Stability Indicating High Performance Liquid Chromatographic Method for Valsartan  

PubMed Central

A stability-indicating HPLC assay method has been developed and validated for valsartan in bulk drug and pharmaceutical dosage forms. An isocratic RP-HPLC was achieved on Waters 2695 using Symmetry C18 (250mm × 4.6mm × 5?) column with the mobile phase consisting of 0.02 mM sodium dihydrogen ortho-phosphate, pH adjusted to 2.5 using ortho-phosphoric acid (solvent A), and acetonitrile (solvent B) in the ratio of 58:42 %v/v. The stress testing of valsartan was carried out under acidic, alkaline, oxidative, thermal, and photolytic conditions. Valsartan was well resolved from its degradation products. The proposed method was validated as per ICH guidelines. The method was found to be suitable for the quality control of valsartan in bulk and pharmaceutical dosage forms as well as the stability-indicating studies.

Rao, KS; Jena, N; Rao, MEB

2010-01-01

43

Determination of Lead, Cadmium, and Mercury by On-Line Enrichment Followed by RP-HPLC  

Microsoft Academic Search

A new method for the simultaneous determination of lead, cadmium, and mercury ions as metal tetra-(4-chlorophenyl)-porphyrin (T4CPP) chelates was developed using reversed-phase-high performance liquid chromatography (RP-HPLC) and combined with on-line enrichment technique. When the Hg-T4CPP, Pb-T4CPP, and Cd-T4CPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol\\/L of pH = 10 pyrrolidine-acetic acid buffer

Liang Wang; Qiufen Hu; Yang Guangyu; Jiayuan Yin; Zhuobin Yuan

2003-01-01

44

Chemometrically assisted simultaneous separation of 21 aromatic sulfonates in ion-interaction RP-HPLC  

Microsoft Academic Search

A method of ion-interaction chromatography (IIR-RP-HPLC) for the simultaneous separation of 21 polar aromatic sulfonates is developed and optimised by a chemometric treatment. The analytes are: 1-naphthalene sulfonic acid (1-NS), 2-naphthalene sulfonic acid, 2-amino-1-naphthalene sulfonic acid (2-A-1-NS), 5-amino-2-naphthalene sulfonic acid (5-A-2-NS), 8-amino-2-naphthalene sulfonic acid (8-A-1-NS), 1-amino-5-naphthalene sulfonic acid (1-A-5-NS), 4-amino-1-naphthalene sulfonic acid (4-A-1-NS), 6-hydroxy-2-naphthalene sulfonic acid (6-H-2-NS), 4-hydroxy-1-naphthalene sulfonic acid

E Marengo; M. C Gennaro; V Gianotti

2000-01-01

45

RP-HPLC prefractionation and its application in expressional proteomics analysis of an in vitro viral infection model.  

PubMed

Prefractionation of complex protein mixtures is an efficient method for increasing the separation power of 2-DE. RP-HPLC has been successfully utilized as a prefractionation method prior to 2-DE. Here we describe the optimization of an efficient RP-HPLC method for prefractionation of baby hamster kidney cell solubilized proteins. A step gradient elution of acetonitrile was optimized and collected fractions were further examined by SDS-PAGE and 2-DE. By utilizing this method an effective increase in separation power of 2-DE is accomplished. Moreover, we describe the application of this method to expressional proteome analysis of a virally infected cell model. PMID:17120811

Vaziri, Behrouz; Rahimpour, Mehdi; Eslami, Naser; Fayaz, Ahmad; Rahimian, Heshmat

2006-10-01

46

Development and validation of RP HPLC method for determination of betamethasone dipropionate in gingival crevicular fluid.  

PubMed

Abstract A simple RP HPLC method for quantification of betamethasone dipropionate (BDP) in gingival crevicular fluid (GCF) has been developed and validated. GCF represents a valuable matrix for therapeutic monitoring of drugs used in the treatment of periodontal disease. The proposed method involves single step extraction for sample preparation. The calibration curve for BDP was linear over the concentration range of 0.10-2.00 ?g mL-1 (R2 = 0.9971). RSD values of intra- and inter-day precision ranged 2.2-4.5 and 1.6-5.7 %, while accuracy values were higher than 96.6 and 97.0 %, respectively. The described method can be successfully applied for determination of betamethasone concentrations in GCF obtained from patients with chronic periodontitis after local treatment with BDP cream 0.5 mg g-1. PMID:24152901

Bogdanovska, Liljana; Popovska, Mirjana; Dimitrovska, Aneta; Petkovska, Rumenka

2013-09-01

47

Elimination of the Interference from Nitrate Ions on Oxalic Acid in RP-HPLC by SolidPhase Extraction with Nanosized Hydroxyapatite  

Microsoft Academic Search

A new method using solid phase extraction with nanosized hydroxyapatite for solving interference from nitrate ions on oxalic acid in reversed phase high performance liquid chromatography (RP-HPLC) was developed. The optimum experimental conditions for the separation and determination of oxalic acid were studied. After the interference was eliminated, oxalic acid was determined by RP-HPLC at the optimum chromatographic conditions with

Wei Wei; Rong Sun; Zhenggui Wei; Haiyan Zhao; Huixin Li; Feng Hu

2008-01-01

48

Comparative study of hydrocarbon, fluorocarbon, and aromatic bonded RP-HPLC stationary phases by linear solvation energy relationships.  

PubMed

The retention properties of eight alkyl, aromatic, and fluorinated reversed-phase high-performance liquid chromatography bonded phases were characterized through the use of linear solvation energy relationships (LSERs). The stationary phases were investigated in a series of methanol/water mobile phases. LSER results show that solute molecular size and hydrogen bond acceptor basicity under all conditions are the two dominant retention controlling factors and that these two factors are linearly correlated when either different stationary phases at a fixed mobile-phase composition or different mobile-phase compositions at a fixed stationary phase are considered. The large variation in the dependence of retention on solute molecular volume as only the stationary phase is changed indicates that the dispersive interactions between nonpolar solutes and the stationary phase are quite significant relative to the energy of the mobile-phase cavity formation process. PCA results indicate that one PCA factor is required to explain the data when stationary phases of the same chemical nature (alkyl, aromatic, and fluoroalkyl phases) are individually considered. However, three PCA factors are not quite sufficient to explain the whole data set for the three classes of stationary phases. Despite this, the average standard deviation obtained by the use of these principal component factors are significantly smaller than the average standard deviation obtained by the LSER approach. In addition, selectivities predicted through the LSER equation are not in complete agreement with experimental results. These results show that the LSER model does not properly account for all molecular interactions involved in RP-HPLC. The failure could reside in the V2 solute parameter used to account for both dispersive and cohesive interactions since "shape selectivity" predictions for a pair of structural isomers are very bad. PMID:10464478

Reta, M; Carr, P W; Sadek, P C; Rutan, S C

1999-08-15

49

Novel Identification of Arsenolipids Using Chemical Derivatizations in Conjunction with RP-HPLC-ICPMS/ESMS.  

PubMed

The identification of molecular structures of an arsenolipid is pivotal for its toxicological assessment and in understanding the arsenic cycling in the environment. However, the analysis of these compounds in a lipid matrix is an ongoing challenge. So far, only a few arsenolipids have been reported, including arsenic fatty acids (AsFAs) and arsenic hydrocarbons (AsHCs). By means of RP-HPLC-ICPMS/ESMS, we investigated Capelin oil ( Mallotus villosus ) for possible new species of arsenolipids. Twelve arsenolipids were identified in the fish oil including three AsFAs and seven AsHCs. Among the AsHCs, four that were identified had protonotated molecular masses of 305, 331, 347, and 359 and have not been reported before. In addition, the compounds with molecular formulas C20H44AsO(+) and C24H44AsO(+) were found in low concentrations and showed chromatographic properties and MS data consistent with cationic trimethylarsenio fatty alcohols. Derivatization by acetylation and thiolation coupled with accurate mass spectrometry was successfully used to establish the occurrence of this new class of arsenolipids as cationic trimethylarsenio fatty alcohols (TMAsFOH). PMID:23984920

Amayo, Kenneth O; Raab, Andrea; Krupp, Eva M; Gunnlaugsdottir, Helga; Feldmann, Jörg

2013-09-16

50

Investigation on the origin of 5-HMF in Shengmaiyin decoction by RP-HPLC method.  

PubMed

The origin of 5-HMF (5-hydroxymethyl-2-furaldehyde) in a Shengmaiyin decoction was investigated by the RP-HPLC method below. A C(18) column (250 mm x 4.6 mm, i.d. 5 microm) with a column temperature of 25 degrees C was used. The mobile phase was a mixture of ultra-pure water-acetonitrile (95:5, V/V) and the flow rate was 1.0 ml/min. The detection wavelength was 280 nm. The injection volume was 1 microl and the running time was about 20 min. The addition of Schisandra was regulated to assess the contribution of an acid environment to the production of 5-HMF. In order to confirm the role of saccharides in the production of 5-HMF, different amount of fructose was used. The 5-HMF level in decoctions of processed and unprocessed Schisandra was investigated in order to determine the origin of 5-HMF. The results showed that 5-HMF was derived mainly from the decoction of Schisandra only and not the mixed decoction of Ophionpogon and Schisandra. The appearance of 5-HMF is not simply the result of the decomposition of saccharides under the acid environment created by Schisandra, but the processing procedure plays an important role in the production of 5-HMF. PMID:16187416

Li, Ying-Hua; Lu, Xiu-Yang

2005-10-01

51

The RP-HPLC method for simultaneous estimation of esomeprazole and naproxen in binary combination  

PubMed Central

Objective: A simple, precise, reliable, rapid, sensitive and validated RP-HPLC method has been developed to determine esomeprazole magnesium trihydrate (ESO) and naproxen (NAP) in synthetic mixture form. Materials and Methods: Chromatographic separation achieved isocratically on Phenomenex, Luna C18 column (5 ?m, 150mm × 4.60mm) and acetonitrile: phosphate buffer (pH 7.0) in the ratio of 50:50 (v/v) as the mobile phase, at a flow rate of 0.5 ml/min. Detection was carried out at 300 nm. The retention times for NAP and ESO was found to be 2.67 ±0.014 and 5.65 ±0.09 min respectively. Parameters such as linearity, precision, accuracy, recovery, specificity and ruggedness are studied as reported in the ICH guidelines. Results: The method was linear in the concentration range of 50-250 ?g/ml for NAP and 2-10 ?g/ml for ESO with correlation coefficient of 0.999 and 0.998 respectively. The mean recoveries obtained for NAP and ESO were 100.01% and 97.76 % respectively and RSD was less than 2. The correlation coefficients for all components are close to 1. Conclusions: Developed method was found to be accurate, precise, selective and rapid for simultaneous estimation of NAP and ESO.

Jain, Deepak Kumar; Jain, Nitesh; Charde, Rita; Jain, Nilesh

2011-01-01

52

[Analysis of phenylethanoid glycosides of Herba cistanchis by RP-HPLC].  

PubMed

The Chinese drug "Rou Cong-rong" (Herba Cistanchis) is one of the commonly used drugs in Chinese traditional medicine. It is used to reinforce the vital function of kidney, especially that of the sexual organs and induce laxation, for the treatment of impotence, premature ejaculation in men, infertility, morbid leukorrhea, profuse metrorrhagia in women, and chronic constipation in the aged. This paper deals with the qualitative and quantitative analysis of phenylethanoid glycosides of four species and one variety of Genus Cistanche and 23 lots of commercial crude drugs of Herba Cistanchis by RP-HPLC. The results were as follows: the chemical constituents of Cistanche deserticola Ma, C. salsa (C. A. Mey) G. Beck, C. salsa var. albiflora P. F. Tu et Z. C. Lou and C. tubulosa were similar while those of C. sinensis were different from the others; the contents of echinacoside and acteoside of C. salsa, which were 2.13% and 1.51%, were the highest of the genus Cistanche. An ODS column (Alltima C18, 5 microns, 250 x 4.6 mm) was employed. Linear gradient elution of acetonitrile--1.5% acetic acid was used as mobile phase, and concentration of acetontrile was from 8% to 20% (0-60 min) in the qualitative analysis, and from 11.5 to 20% (0-35 min) in the quantitative analysis. The flow rate was 1.2 ml.min-1. The detection wavelength was set at 335 nm. PMID:11499033

Tu, P F; Wang, B; Deyama, T; Zhang, Z G; Lou, Z C

1997-04-01

53

Development and validation of RP-HPLC method for the determination of riluzole hydrochloride in bulk and tablet dosage forms  

Microsoft Academic Search

A reverse-phase high performance liquid chromatography (RP-HPLC) method was developed and validated for the estimation of riluzole hydrochloride in bulk and tablet dosage forms. The separation was achieved on BDS hypersil ODS analytical column (100 mm × 4.6 mm i.d., 3.0 µm) using 5M ammonium acetate and acetonitrile in the ratio 50:50 v\\/v as mobile phase and at a flow

Sreekanth Nama; Bahlul Z. Awen; Babu rao Chandu; Mukkanti Kagga

2011-01-01

54

RP-HPLC Determination of vitamins B1 ,B 3 ,B 6, folic acid and B12 in multivitamin tablets  

Microsoft Academic Search

A simple and sensitive reversed-phase, ion-pair HPLC method was developed and validated for the simultaneous determination of B-group vitamins, thiamine chloride hydro- chloride (B1), nicotinamide (B3), pyridoxine hydrochloride (B6) and folic acid in Pentovit ® coated tablets. The cyanocobalamine (B12) was determined separately, because of its low concentration in the investigated multivitamin preparation. RP-HPLC analysis was per- formed with a

JASMINA BRBORIC; SOTE VLADIMIROV

2005-01-01

55

DETERMINATION OF CLENBUTEROL HCl IN HUMAN SERUM, PHARMACEUTICALS, AND IN DRUG DISSOLUTION STUDIES BY RP-HPLC  

Microsoft Academic Search

A simple, reliable, and rapid RP-HPLC method has been developed for the determination of clenbuterol HCl in human serum and pharmaceuticals, in order to carry out drug dissolution studies for clenbuterol tablets. This compound is well separated on a C18 column by using the mobile phase consisting of a mixture of acetonitrile and ion-pair buffer (32:68; v\\/v) at a flow

Yalçin Özkan; Sibel A. Özkan; Hassan Y. Aboul-Enein

2001-01-01

56

Development of an RP-HPLC method for the simultaneous determination of benzoic acid, sorbic acid, natamycin and lysozyme in hard and pasta filata cheeses  

Microsoft Academic Search

A single method, based on RP-HPLC with UV detection, was developed with the aim of simultaneously quantifying four preservatives in cheeses: benzoic acid, sorbic acid, natamycin and lysozyme.The preservatives were extracted from different cheeses by using the same procedure, and separated by a single RP-HPLC gradient elution showing good resolution, in a short time.Recoveries were always higher than 91%; MDLs

Chiara Guarino; Fabio Fuselli; Alessandro La Mantia; Lucia Longo

2011-01-01

57

Application of validated RP-HPLC method for simultaneous determination of docetaxel and ketoconazole in solid lipid nanoparticles.  

PubMed

Docetaxel has significant single agent activity in prostate cancer and ketoconazole also has activity as a second line hormonal agent. In vitro, ketoconazole is synergistic with some chemotherapy agents by enhancing the intracellular retention of the cytotoxic agent. A potential drug-drug interaction exists though between docetaxel and ketoconazole because both agents are metabolized hepatically by the cytochrome P-450 system. Hence, a nanoparticulate system was formulated by loading both drugs for tumor targeting. Assay and in vitro release of the formulation were conducted by developing simple, precise, accurate, and validated analytical method for simultaneous determination docetaxel and ketoconazole using reversed-phase high-performance liquid chromatography (RP-HPLC). The RP-HPLC method was developed using Waters Symmetry C(18) column (25 cm × 4.5 mm, 5 ?m) with a mobile phase consisting of acetonitrile and 0.2% triethylamine pH adjusted to 6.4 (48:52, v/v) at flow rate of 1 mL/min. Intra-day and inter-day variations were less than 2% over the linearity range, 0.5-20 ?g/mL. The proposed two methods were successfully applied for the determination of docetaxel and ketoconazole in solid lipid nanoparticles. PMID:21223639

Venishetty, Vinay Kumar; Parikh, Nirali; Sistla, Ramakrishna; Ahmed, Farhan J; Diwan, Prakash Vamanrao

2011-02-01

58

Improved RP-HPLC method to determine biapenem in human plasma/urine and its application to a pharmacokinetic study.  

PubMed

Existing methods to determine biapenem (CAS 120410-24-4), a carbapenem, either lacked sensitivity/reproducibility or had no internal standard as a control. Here an improved reversed-phase high-performance liquid chromatographic (RP-HPLC) method was established in human plasma and urine. After adding p-aminobenzoic acid as the internal standard to plasma or urine, plasma samples were ultra-filtrated and urine samples were diluted directly. Chromatographic separations were carried out on a 4.6 mm x 150 mm column with acetonitrile-0.1 mol/l sodium acetate (2:98, v:v; pH 4.38 or 4.00) as mobile phase and UV detection at 300 nm. The extraction recovery was 91.51% for biapenem at the concentration level of 5 microg /ml in human plasma. The linear quantification range of the method was 0.1 to approximately 50 microg /ml for plasma and urine, with linear correlation coefficients greater than 0.998. The intra-day and inter-day relative standard deviations (R.S.D.) for biapenem at low, middle and high levels in human samples were less than 12.51% for plasma and less than 7.05% for urine. The RP-HPLC method was successfully applied to pharmacokinetic studies, in which healthy subjects received multiple doses of biapenem (300 mg, i.v., b.i.d., for 5 continuous days). The pharmacokinetic results are presented. PMID:21528646

Zhao, Libo; Liu, Yi; Kou, Zhibin; Bayasi, Aidijie; Cai, Huan; Zhang, Chunyan; Wang, Qian; Li, Yuzhen; Fang, Yi

2011-01-01

59

Quantization of Dextromethorphan and Levocetirizine in Combined Dosage form Using a Novel Validated RP-HPLC Method.  

PubMed

The present study reveals a simple isocratic RP-HPLC method for the simultaneous determination of dextromethorphan hydrobromide and levocetirizine dihydrochloride in a cough syrup. The separation of these compounds was achieved within 10 min on a Phenomenex (USA) C(18) analytical column, 250×4.0 mm i.d., using an isocratic mobile phase consisting of potassium dihydrogen phosphate buffer (pH 2.5) - acetonitrile- tetrahydrofuran (70:25:5, v/v/v). The analysis was performed at a flow rate of 1.2 ml/min and at a detection wavelength of 232 nm. Percentage recovery and RSD were 100.36% and 0.05% for levocetirizine dihydrochloride, 100.35% and 0.27% for dextromethorphan hydrobromide respectively. Quantification of the components in syrup formulation was calculated against the peak areas of freshly prepared standard solutions. The method was validated as per ICH guidelines. PMID:23204629

Joshi, Shalini; Bhatia, C; Bal, C S; Rawat, M S M

2012-01-01

60

Quantization of Dextromethorphan and Levocetirizine in Combined Dosage form Using a Novel Validated RP-HPLC Method  

PubMed Central

The present study reveals a simple isocratic RP-HPLC method for the simultaneous determination of dextromethorphan hydrobromide and levocetirizine dihydrochloride in a cough syrup. The separation of these compounds was achieved within 10 min on a Phenomenex (USA) C18 analytical column, 250×4.0 mm i.d., using an isocratic mobile phase consisting of potassium dihydrogen phosphate buffer (pH 2.5) - acetonitrile- tetrahydrofuran (70:25:5, v/v/v). The analysis was performed at a flow rate of 1.2 ml/min and at a detection wavelength of 232 nm. Percentage recovery and RSD were 100.36% and 0.05% for levocetirizine dihydrochloride, 100.35% and 0.27% for dextromethorphan hydrobromide respectively. Quantification of the components in syrup formulation was calculated against the peak areas of freshly prepared standard solutions. The method was validated as per ICH guidelines.

Joshi, Shalini; Bhatia, C.; Bal, C. S.; Rawat, M. S. M.

2012-01-01

61

Bioactive compounds, RP-HPLC analysis of phenolics, and antioxidant activity of some Portuguese shrub species extracts.  

PubMed

In the ecosystem of Serra Da Estrela, some plant species have the potential to be used as raw material for extraction of bioactive products. The goal of this work was to determine the phenolic, flavonoid, tannin and alkaloid contents of the methanolic extracts of some shrubs (Echinospartum ibericum, Pterospartum tridentatum, Juniperus communis, Ruscus aculeatus, Rubus ulmifolius, Hakea sericea, Cytisus multiflorus, Crataegus monogyna, Erica arborea and Ipomoea acuminata), and then to correlate the phenolic compounds and flavonoids with the antioxidant activity of each extract. The Folin-Ciocalteu's method was used for the determination of total phenols, and tannins were then precipitated with polyvinylpolypyrrolidone (PVPP); a colorimetric method with aluminum chloride was used for the determination of flavonoids, and a Dragendorff's reagent method was used for total alkaloid estimation. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) and beta-carotene bleaching tests were used to assess the antioxidant activity of extracts. The identification of phenolic compounds present in extracts was performed using RP-HPLC. A positive linear correlation between antioxidant activity index and total phenolic content of methanolic extracts was observed. The RP-HPLC procedure showed that the most common compounds were ferulic and ellagic acids and quercetin. Most of the studied shrubs have significant antioxidant properties that are probably due to the existence of phenolic compounds in the extracts. It is noteworthy to emphasize that for Echinospartum ibericum, Hakea sericea and Ipomoea acuminata, to the best of our knowledge, no phytochemical studies have been undertaken nor their use in traditional medicine been described. PMID:22312726

Luís, Angelo; Domingues, Fernanda; Duarte, Ana Paula

2011-12-01

62

Extraction and RP-HPLC determination of taxol in rat plasma, cell culture and quality control samples  

PubMed Central

A rapid, sensitive, selective and validated reverse phase high-performance liquid chromatography (RP-HPLC) method for the estimation of paclitaxel in micro-sample of rat plasma and in culture of cancer cells was performed in this study. The mobile phase consisted of an optimized mixture of methanol:water: trifluroacetic acid (80: 20: 0.1, v/v/v). Column elution at a flow rate of 1 mL/minute with UV detection at 225 nm at room temperature was used. The RP-HPLC method was successfully applied for the determination of paclitaxel in plasma samples and in culture of cancer cells with nano-quantity of estimation. The validation studies were performed in accordance with the International Conference on Harmonization (ICH) guidelines. The intra- and inter-day precision showed that the coefficients of variation ranged from 1.07% to 4.27% at different levels of concentrations. To the best of our knowledge, this study also reported for the first time the optimization of different solvents for effective extraction of paclitaxel wherein tert.-butyl methyl ether (TBME): diethyl ether (DEE) in 50: 50 v/v composition was found most efficient with extraction efficiency ranging between 77.99% and 91.74% and between 76.14 and 93.66% in the plasma and cell culture, respectively. This proposed method was successfully applied to study the pharmacokinetics of paclitaxel and the influence of verapamil and all-trans retinoic acid (atRA) on paclitaxel pharmacokinetics in rat models. This proposed method might emerge as a valuable aid in the laboratory monitoring of paclitaxel in a variety of in vitro as well as in vivo scenarios.

Tekade, Rakesh Kumar; D'Emanuele, Antony; Elhissi, Abdelbary; Agrawal, Ashish; Jain, Anurekha; Arafat, Basel Tawfiq; Jain, Narendra Kumar

2013-01-01

63

Extraction and RP-HPLC determination of taxol in rat plasma, cell culture and quality control samples.  

PubMed

A rapid, sensitive, selective and validated reverse phase high-performance liquid chromatography (RP-HPLC) method for the estimation of paclitaxel in micro-sample of rat plasma and in culture of cancer cells was performed in this study. The mobile phase consisted of an optimized mixture of methanol:water: trifluroacetic acid (80: 20: 0.1, v/v/v). Column elution at a flow rate of 1 mL/minute with UV detection at 225 nm at room temperature was used. The RP-HPLC method was successfully applied for the determination of paclitaxel in plasma samples and in culture of cancer cells with nano-quantity of estimation. The validation studies were performed in accordance with the International Conference on Harmonization (ICH) guidelines. The intra- and inter-day precision showed that the coefficients of variation ranged from 1.07% to 4.27% at different levels of concentrations. To the best of our knowledge, this study also reported for the first time the optimization of different solvents for effective extraction of paclitaxel wherein tert.-butyl methyl ether (TBME): diethyl ether (DEE) in 50: 50 v/v composition was found most efficient with extraction efficiency ranging between 77.99% and 91.74% and between 76.14 and 93.66% in the plasma and cell culture, respectively. This proposed method was successfully applied to study the pharmacokinetics of paclitaxel and the influence of verapamil and all-trans retinoic acid (atRA) on paclitaxel pharmacokinetics in rat models. This proposed method might emerge as a valuable aid in the laboratory monitoring of paclitaxel in a variety of in vitro as well as in vivo scenarios. PMID:24086173

Tekade, Rakesh Kumar; D'Emanuele, Antony; Elhissi, Abdelbary; Agrawal, Ashish; Jain, Anurekha; Arafat, Basel Tawfiq; Jain, Narendra Kumar

2013-08-13

64

A validated RP-HPLC method for quantitation of trigonelline from herbal formulations containing Trigonella foenum-graecum (L.) seeds  

PubMed Central

Background: Trigonella foenum-graecum (L.) (Fabaceae, Fenugreek) is an important ingredient of Ayurvedic and other marketed herbal formulations. Fenugreek seeds are employed in many traditional systems as an antibacterial and antidiabetic agent, gastric stimulant and galactogogue. Trigonelline, a major phytoconstituent found in fenugreek seeds, shows estrogenic, anti-diabetic and anti-invasive activity. Therefore, it is a suitable bioactive marker to establish the quality of crude drug and its formulations. Objective: To develop an efficient and effective RP-HPLC method for estimation of trigonelline from Trigonella foenum-graecum seeds and its marketed herbal formulations. Materials and Methods: Separation and detection of trigonelline was carried out on a Cosmosil CN-MS column eluted with methanol:distilled water [95:5, v/v; pH 3.5 using hydrochloric acid]. Detection was carried out at 267 nm using a Photo Diode Array detector. Fenugreek seeds and two marketed herbal formulations were subjected for HPLC analysis of Trigonelline. Results: The RP-HPLC method was validated as per ICH guidelines and the content of trigonelline in marketed polyherbal formulations such as Dibet powder and Amyron syrup was determined. The LOD and LOQ were found to be 5.00 ng/mL and 50.00 ng/mL, respectively. Detector response was linear from 100.00 to 8000.00 ng/mL. The method was found to be simple, sensitive, accurate, reproducible and rugged. Conclusion: This work can be recommended for quality assurance and marker-based standardization of formulations containing fenugreek seeds.

Shailajan, Sunita; Menon, Sasikumar; Singh, Ashish; Mhatre, Mandar; Sayed, Neelam

2011-01-01

65

Analysis of azithromycin and its related compounds by RP-HPLC with UV detection.  

PubMed

A simple, validated stability-indicating liquid chromatographic method is developed for the analysis of azithromycin in raw material and in pharmaceutical forms. Liquid chromatography with a UV detector at a wavelength of 210 nm using a reversed-phase C(18) stationary phase has been employed in this study. Isocratic elution is employed using a mixture of phosphate buffer-methanol (20:80). This new method is validated in accordance with USP requirements for new methods for assay determination, which include accuracy, precision, specificity, linearity, and range. This method shows enough selectivity, sensitivity, accuracy, precision, and linearity range to satisfy Federal Drug Administration and International Conference of Harmonization regulatory requirements. The current method demonstrates good linearity over the range of 0.3-2.0 mg/mL of azithromycin. The accuracy of the method is 100.5% with a relative standard deviation of 0.2%. The precision of this method reflected by relative standard deviation of replicates is 0.2%. The method is sensitive with a detection limit of 0.0005 mg/mL for azithromycin. Impurities and degradation products of azithromycin can be selectively determined with a good resolution in both raw material and pharmaceutical forms. PMID:20109282

Al-Rimawi, Fuad; Kharoaf, Maher

2010-02-01

66

Determination of seven phenolic compounds in Rhizoma Sparganii by RP-HPLC.  

PubMed

A reversed-phase high-performance liquid chromatographic method was developed for the simultaneous quantification of seven phenolic compounds from Rhizoma Sparganii. The samples were separated on a Waters SunFire C18 column with a temperature of 30°C. Gradient elution was applied, using 0.8% acetic acid (solvent A) and methanol (solvent B) with a flow rate of 1.0 mL/min, and detection wavelength was 280 nm. The validation of the method included linearity, precision, repeatability, stability and recovery. The calibration curves showed good linear regression (R(2) > 0.9996) within the test range. The developed method indicated good precision and accuracy, with the overall intra-day and inter-day variation at less than 3%. The range of recoveries for the seven analytes was 95.34-100.06% with relative standard deviation < 3.08 %. The established method was successfully applied for the determination of seven phenolic compounds in 12 batches of Rhizoma Sparganii. The study may be useful in the quality evaluation of Rhizoma Sparganii, and can provide technical support for pharmacological and clinical research of related drugs. PMID:23013896

Wang, Xinsheng; Wu, Qi-nan; Wu, Yanfang; Wu, Chengying; Yue, Wei; Liang, Qiaoli

2012-09-26

67

Hydrolytic Degradation Profile and RP-HPLC Estimation of Cilostazol in Tablet Dosage Form  

PubMed Central

A simple, selective, precise and stability-indicating high-performance liquid-chromatographic method of analysis of cilostazol in pharmaceutical dosage form was developed and validated. The solvent system consisted of 10 mM phosphate buffer (pH 6.0):acetonitrile:methanol (20:40:40). Retention time of cilostazol in C18 column was 5.7 ± 0.1 min at the flow rate 1.3 ml/min. Cilostazol was detected at 248 nm at room temperature. The linear regression analysis data for the calibration plots showed good linear relationship with correlation coefficient value, r 2 =0.9998 in the concentration range 100–3200 ng/ml with slope 43.45 intercept 156.75. The method was validated for linearity, range, accuracy, precision and specificity. Cilostazol was determined in tablet dosage form in range of 99.58-100.67% with 0.4600 standard deviation. Stress studies were conducted in acid and alkali hydrolysis with gradual increasing concentration. Cilostazol was found to be stable in various concentrations of acidic and alkaline.

Basniwal, P. K.; Shrivastava, P. K.; Jain, Deepti

2008-01-01

68

Concurrent Estimation of Amlodipine Besylate, Hydrochlorothiazide and Valsartan by RP-HPLC, HPTLC and UV-Spectrophotometry.  

PubMed

Accurate, sensitive and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC), high-performance thin-layer chromatography (HPTLC) and ultraviolet (UV) spectrophopometric methods were developed for the concurrent estimation of amlodipine besylate (AMLO), hydrochlorothiazide (HCTZ) and valsartan (VALS) in bulk and combined tablet dosage forms. For the RP-HPLC method, separation was achieved on a C18 column using potassium dihydrogen orthophosphate buffer (50 mM, pH 3.7) with 0.2% triethylamine as the modifier and acetonitrile in the ratio of 56:44 (v/v) as the mobile phase. Quantification was achieved using a photodiode array detector at 232 nm over a concentration range of 2-25 µg/mL for AMLO, 5-45 µg/mL for HCTZ and 20-150 µg/mL for VALS. For the HPTLC method, the drugs were separated by using ethyl acetate-methanol-toluene-ammonia (7.5:3:2:0.8, v/v/v/v) as the mobile phase. Quantification was achieved using UV detection at 242 nm over a concentration range of 100-600 ng/spot for AMLO, 150-900 ng/spot for HCTZ and 1,200-3,200 ng/spot for VALS. The UV-spectrophotometric simultaneous equation method was based on the measurement of absorbance at three wavelengths; i.e., at 237.6 nm (?(max) of AMLO), 270.2 nm (?(max) of HCTZ) and 249.2 nm (?(max) of VALS) in methanol. Quantification was achieved over the concentration range of 2-20 µg/mL for AMLO, 5-25 µg/mL HCTZ and 10-50 µg/mL for VALS. All methods were validated according to International Conference on Harmonization guidelines and successfully applied to marketed pharmaceutical formulations. Additionally, the three methods were compared statistically by an analysis of variance test, which revealed no significant difference between the proposed methods with respect to accuracy and precision. PMID:23293040

Sharma, Manish; Kothari, Charmy; Sherikar, Omkar; Mehta, Priti

2013-01-01

69

Simultaneous determination of piracetam and its four impurities by RP-HPLC with UV detection.  

PubMed

A simple and rapid high-performance liquid chromatographic method for the separation and determination of piracetam and its four impurities, 2-oxopyrrolidin-1-yl)acetic acid, pyrrolidin-2-one, methyl (2-oxopyrrolidin-1-yl)acetate, and ethyl (2-oxopyrrolidin-1-yl)acetate, was developed. The separation was achieved on a reversed-phase C(18) Nucleosil column (25 cm x 0.46 cm, 10 microm). The mobile phase is composed of an aqueous solution containing 0.2 g/L of triethyl amine-acetonitrile (85:15, v/v). The pH of the mobile phase was adjusted to 6.5 with phosphoric acid at a flow rate of 1 mL/min at ambient temperature and UV detection at 205 nm. The developed method was found to give good separation between the pure drug and its four related substance. The polynomial regression data for the calibration plots showed good linear relationship in the concentration range of 50-10,000 ng/mL, 25-10,000 ng/mL, 45-10,000 ng/mL, 34-10,000 ng/mL, and 55-10,000 ng/mL, respectively, with r(2) = 0.9999. The method was validated for precision, accuracy, ruggedness, and recovery. The minimum quantifiable amounts were found to be 50 ng/mL of piracetam, 25 ng/mL of 2-oxopyrrolidin-1-yl)acetic acid, 45 ng/mL of pyrrolidin-2-one, 34 ng/mL of methyl (2-oxopyrrolidin-1-yl)acetate, and 55 ng/mL of ethyl (2-oxopyrrolidin-1-yl)acetate. Statistical analysis proves that the method is reproducible and selective for the estimation of piracetam as well as its related substance. As the method could effectively separate the drug from the related substances, it can be employed as a stability-indicating one. The proposed method shows high efficiency, allowing the separation of the main component piracetam from other impurities. PMID:20819285

Arayne, M Saeed; Sultana, Najma; Siddiqui, Farhan Ahmed; Mirza, Agha Zeeshan; Qureshi, Faiza; Zuberi, M Hashim

2010-08-01

70

Simultaneous quantitative determination of nine active chemical compositions in traditional Chinese medicine Glycyrrhiza by RP-HPLC with full-time five-wavelength fusion method.  

PubMed

A new, simple, accurate and reliable full-time five-wavelength fusion method for the simultaneous separation and determination of nine active chemical compositions (liquiritin apioside, liquiritin, isoliquiritin apioside, ononin, isoliquiritin, liquiritigenin, calycosin, isoliquiritigenin, Glycyrrhizic acid monoammonium salt) in traditional Chinese medicine Glycyrrhiza was developed using reverse phase high-performance liquid chromatography (RP-HPLC) coupled with a diode-array detector (DAD). The chromatographic separation was performed on an Agilent TC-C18 column with gradient elution using 0.04% methanoic acid (A) and acetonitrile (B) at a flow rate of 1.0 mL min(-1) and UV detection at 248 nm, 250 nm, 276 nm, 362 nm, 370 nm. The standard curves were linear over the range of 2.1379-12.8272 ?g for liquiritin apioside, 3.9299-23.5794 ?g for liquiritin, 1.0432-6.2592 ?g for isoliquiritin apioside, 0.8764-5.8584 ?g for ononin, 1.0701-6.4205 ?g for isoliquiritin, 1.3685-8.2111 ?g for liquiritigenin, 0.3927-2.3563 ?g for calycosin, 0.2498- 1.4986 ?g for isoliquiritigenin, 2.0094-12.0564 ?g for Glycyrrhizic acid monoammonium salt, respectively (r(2) > 0.9997). The recoveries and relative standard deviation (RSD) varied from 95.09% to 103.54% and 1.09% to 2.36%, respectively. The precision for all the analytes was less than 2.52%. The method indicated good performance in terms of precision, accuracy and linearity. The method enabled the simultaneous determination of nine active chemical compositions for quality control of Glycyrrhiza. PMID:23336517

Wu, Yin-Ping; Meng, Xian-Sheng; Bao, Yong-Rui; Wang, Shuai; Kang, Ting-Guo

2013-01-01

71

Application of RP-HPLC-diode array detector after SPE to the determination of pesticides in pepper samples.  

PubMed

The application of HPLC-diode array detector (DAD) after SPE for identification and quantitative analysis of pesticides in red and green pepper samples is demonstrated. An HPLC procedure on an RP column (C18) was developed for analysis of selected pesticides from different chemical groups: metamitron, metalaxyl, linuron, and prometryn. Average recoveries for C18 Polar Plus cartridges and solvents by the proposed RP-HPLC-DAD method after SPE are presented. Average recoveries from the spiked samples and the SDs were 22.5 +/- 2.2, 138.0 +/- 4.1, 78.6 +/- 2.8, and 109.2 +/- 2.3% for metamitron, metalaxyl, linuron, and prometryn, respectively, at concentrations of 7 microg/g in the plant material. The efficiency of the SPE procedure was evaluated using real food samples. The quantities of prometryn, linuron, metalaxyl, and metamitron determined were in the ranges of 0.02-2.24 microg/g (n = 24), 0.08-1.01 microg/g (n = 9), 1.61-2.28 microg/g (n=4), and 0.05-1.07 microg/g (n = 3), respectively, in plant material sampled in 2011. The method was validated for precision, repeatability, and accuracy. PMID:23175966

Tuzimski, Tomasz

72

Development and validation of RP-HPLC method for sildenafil citrate in rat plasma-application to pharmacokinetic studies  

PubMed Central

Sildenafil citrate (SIL) is used in the treatment of erectile dysfunction and other chronic disorders. For the pharmacokinetic investigation of SIL we developed a simple and sensitive method for the estimation of SIL in rat plasma by reverse phase high-performance liquid chromatography (RP-HPLC). The drug samples were extracted by liquid–liquid extraction with 300 ?l of acetonitrile and 5 ml of diethyl ether. Chromatographic separation was achieved on C18 column using methanol:water (85:15 v/v) as mobile phase at a flow rate of 1 ml/min and UV detection at 230 nm. The retention time of SIL was found to be 4.0 min having a separation time less than 5 min. The developed method was validated for accuracy, precision, linearity and recovery. Linearity studies were found to be acceptable over the range of 0.1–6 ?g/ml. The method was successfully applied for the analysis of rat plasma sample for the application in pharmacokinetic study, drug interaction, bioavailability and bioequivalence.

Tripathi, A.S.; Sheikh, I.; Dewani, A.P.; Shelke, P.G.; Bakal, R.L.; Chandewar, A.V.; Mazumder, P.M.

2012-01-01

73

RP-HPLC analysis of the phenolic compounds of plant extracts. investigation of their antioxidant capacity and antimicrobial activity.  

PubMed

Extracts of aromatic plants of Greek origin were examined as potential sources of phenolic compounds. RP-HPLC with UV detection was employed for the identification and quantification of the phenolic antioxidants, present in methanolic extracts. The most abundant phenolic acids were ferulic acid (1.1-280 mg/100 g of dry sample) and caffeic acid (1.2-60 mg/100 g of dry sample). (+)-Catechin and quercetin were the most abundant flavonoids. Apigenin and luteolin were detected in high amounts in Menta pulegium and Thymus vulgaris, respectively. The antioxidant capacity was determined, in dried ground plants and in their methanol extracts, with the Rancimat test using sunflower oil as substrate. Both pulverized plants and extracts showed antioxidant capacity. Total phenolic content in the extracts was determined spectrometrically according to the Folin-Ciocalteu assay and ranged from 1 to 21 mg of gallic acid/100 g of dry sample. Antimicrobial activity of the extracts against selected microbes was also conducted in this study. PMID:15713039

Proestos, C; Chorianopoulos, N; Nychas, G-J E; Komaitis, M

2005-02-23

74

Quantification of lactose using ion-pair RP-HPLC during enzymatic lactose hydrolysis of skim milk.  

PubMed

The correct labelling of dairy foods as "lactose-free" requires a suitably sensitive and valid analytical method for the quantification of lactose in complex food matrices. Thus, an ion-pair RP-HPLC method for the simultaneous determination of lactose, glucose and galactose in original skim milk was investigated. The samples derived from an enzymatic lactose hydrolysis approach (0.5L) using the commercial ?-galactosidase Godo-YNL2. After derivatisation with p-aminobenzoic acid and sodium cyanoborohydride, the samples were injected on a RP-C(18) column. Tetrabutylammonium hydrogen sulphate was used as the ion-pair reagent in the eluent system. The sugars were quantified using photometric- (UV; 303 nm) and fluorescence-detection (?(ex) 313 nm, ?(em) 358 nm). The overall run time was 27 min. The limits of detection (LOD) were estimated at 2 mgL(-1) (UV detection) and at 0.13 mgL(-1) (fluorescence detection). The limits of quantification were 6 mgL(-1) (UV detection) and 0.45 mgL(-1) (fluorescence detection). Thus, this analytical method is suitable for sensitive lactose quantification in milk systems of less than 10 mgL(-1). PMID:22980818

Erich, Sarah; Anzmann, Theresa; Fischer, Lutz

2012-07-20

75

A Validated RP HPLC-PAD Method for the Determination of Hederacoside C in Ivy-Thyme Cough Syrup  

PubMed Central

A simple reversed phase high-performance liquid chromatographic (RP-HPLC) method coupled with a photodiode array detector (PAD) has been developed and validated for the analysis of hederacoside C, the marker of ivy plant, in Ivy-Thyme cough syrup. Separation of hederacoside C was achieved using a Phenomenex-Gemini C18 column isothermally at 40°C. A mobile phase system constituted of solvent A (water: acetonitrile: orthophosphoric acid (85%), 860?:?140?:?2?v/v) and solvent B (acetonitrile: orthophosphoric acid (85%), 998?:?2?v/v) was used, at gradient conditions, at a flow rate of 1.5?mL/min. Analysis was performed using UV-detection (205?nm). The method was linear over the range (0.03–0.15)?mg/mL of hederacoside C (r = 0.9992). Repeatability and intermediate precision were acceptable (RSD <2%). Limits of detection (LOD) and quantitation (LOQ) were 0.011 and 0.032?mg/mL, respectively. Percentage recovery was found to lie between 99.69% and 100.90% (RSD <2%). The method was also proved to be specific (peak-purity coefficient = 0.996).

Khdair, Ayman; Mohammad, Mohammad K.; Tawaha, Khaled; Al-Hamarsheh, Eman; AlKhatib, Hatim S.; Al-khalidi, Bashar; Bustanji, Yasser; Najjar, Samer; Hudaib, Mohammad

2010-01-01

76

A validated RP-HPLC method for quantitative determination of related impurities of ursodeoxycholic acid (API) by refractive index detection.  

PubMed

An isocratic RP-HPLC method was developed and validated for quantitative determination of ursodeoxycholic acid (UDCA) and its related impurities. Considering the lower molecular absorptivity of UDCA, refractive index detector was used to detect the impurities on a Phenomenex Luna C(18), 150 mm × 4.6 mm, 5 ?m column. The mobile phase was 0.1% acetic acid/methanol (30:70, v/v) and flow rate was 0.8 ml/min. The detector and column temperature was maintained at 40°C. The method is linear over a range of 0.25-3.5 ?g/ml for all impurities and coefficient of correlation (r(2)) was ?0.9945. The accuracy of method demonstrated at three levels in the range of 50-150% of the specification limit and recoveries were found to be in the range of 97.11-100.75%. The precision for all related impurities was below 3.5% R.S.D. The method was applied to commercial bulk drug sample for assay purpose. PMID:21095088

Peepliwal, Ashok; Bonde, C G; Bothara, K G

2010-10-14

77

RP-HPLC method for simultaneous estimation of tenofovir disoproxil fumarate, lamivudine, and efavirenz in combined tablet dosage form  

PubMed Central

Background: A simple, precise, accurate, and rapid reverse phase-high performance liquid chromatography (RP-HPLC) method with UV-Visible detector has been developed and subsequently validated for the simultaneous determination of tenofovir disoproxil fumarate (TDF), lamivudine (LAMI), and efavirenz (EFV) in their combined tablet dosage form. Materials and Methods: The separation was based on the use of a Kromasil C18 analytical column (150 × 4.6 mm, i.d., 5 ?m). The mobile phase consisted of a mixture of 70 volumes of methanol and 30 volumes of 10 mM phosphate buffer (pH 5.0). The separation was carried out at 40°C temperature with a flow rate of 1 ml/min. Results: Quantitation was achieved with UV detection at 254 nm, with linear calibration curves at concentration ranges of 1–6 ?g/ml for TDF and LAMI and 2–12 ?g/ml for EFV. The recoveries obtained were 99.46–101.36% for LAMI, 99.57–101.42% for TDF, and 99.96–100.87 for EFV. Conclusion: The method was validated according to International conference of harmonisation guidelines in terms of accuracy, precision, specificity, robustness, limits of detection and quantitation, and other aspects of analytical validation.

Bhavsar, Dhara S.; Patel, Bhavini N.; Patel, Chhaganbhai N.

2012-01-01

78

Simple RP-HPLC method for determination of triple drug combination of valsartan, amlodipine and hydrochlorothiazide in human plasma.  

PubMed

A simple RP-HPLC method for the quantification of valsartan (VAL), amlodipine (AML) and hydrochlorothiazide (HCT) in human plasma was developed and validated. VAL, AML and HCT were resolved using a Gemini C18 column and mobile phase gradient starting from 20 % acetonitrile and 80 % 10 mmol L(-1) ammonium formate (V/V, pH 3.5 ± 0.2, by formic acid) to 70 % acetonitrile and 30 % 10 mmol L(-1) ammonium formate, over 20 minutes, with a flow rate of 1 mL min(-1). The samples were purified by protein precipitation and extraction. Telmisartan was used as internal standard. The method was validated according to USFDA and EMEA guidelines with good reproducibility and linear responses R = 0.9985 (VAL), 0.9964 (AML), and 0.9971 (HCT). RSDs of intra- and inter-day precision ranged 2.2-8.1 and 4.6-11.7 %, respectively, for all three drugs. Mean extraction recoveries of three QCs for the triple drug combination were 76.5 (VAL), 72.0 (AML) and 73.0 (HCT) % for human plasma. Although the LC-MS/MS method is more sensitive than HPLC, HPLC is still suitable for preliminary pharmacokinetic study. The experiments performed demostrated that simultaneous determination of all components of the triple drug combination in human plasma can be done by this method. Proposed method can be also used for guidance to the LC-MS/MS method. PMID:22472448

Sharma, Ritesh N; Pancholi, Shyam Sunder

2012-03-01

79

Development and Validation of an RP-HPLC Method for CB13 Evaluation in Several PLGA Nanoparticle Systems  

PubMed Central

A simple, fast, and reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for determining of a cannabinoid derivate, which displays potent antihyperalgesic activity, 1-naphthalenyl[4-(pentyloxy)-1-naphthalenyl]methanone (CB13) into PLGA nanoparticles. Separation was achieved in a C18 column using a mobile phase consisting of two solvents: solvent A, consisting of acetonitrile?:?water?:?acetic acid (75?:?23.7?:?1.3?v/v), and solvent B, consisting of acetonitrile. An isocratic method (70?:?30?v/v), with a flow rate of 1.000?mL/min, and a diode array detector were used. The developed method was precise, accurate, and linear over the concentration range of analysis with a limit of detection and a limit of quantification of 0.5 and 1.25??g/mL, respectively. The developed method was applied to the analysis of CB13 in nanoparticles samples obtained by three different procedures (SEV, FF, and NPP) in terms of encapsulation efficiency and drug release. Nanoparticles size and size distribution were also evaluated founding that NPP method presented the most lowest particle sizes with narrow-size distribution (?320?nm) and slightly negative zeta potential (??25?mV) which presumes a suitable procedure for the synthesis of PLGA-CB13 nanoparticles for oral administration.

Alvarez-Fuentes, J.; Martin-Banderas, L.; Munoz-Rubio, I.; Holgado, M. A.; Fernandez-Arevalo, M.

2012-01-01

80

Rat neuropeptidomics by LC-MS/MS and MALDI-FTMS: Enhanced dissection and extraction techniques coupled with 2D RP-RP HPLC.  

PubMed

Recently developed sample preparation techniques employing microwave irradiation have enabled the comprehensive study of endogenous mammalian neuropeptides. These methods reduce interference from post-mortem protein degradation by deactivating proteases via heat denaturation. Alternatively, we have developed a protocol using cryostat dissection and a boiling extraction buffer to achieve a similar effect. This novel methodology greatly reduces post-mortem protein contamination and increases neuropeptide identification without the use of specialized equipment. In addition, a 2D HPLC scheme employing differential pH selectivity in the first and second dimensions has been used to enhance neuropeptidome coverage. By using our novel dissection protocol in tandem with 2D RP-RP HPLC, we were able to identify a total of 56 peptides from known neuropeptide precursors, including 17 previously unidentified peptides. The use of cryostat dissection and two-dimensional RP-RP HPLC enhances the detection of novel neuropeptides by deactivating proteases and reducing sample complexity. PMID:17137338

Dowell, James A; Heyden, William Vander; Li, Lingjun

2006-12-01

81

Identification of the first fumonisin mycotoxins with three acyl groups by ESI-ITMS and ESI-TOFMS following RP-HPLC separation: palmitoyl, linoleoyl and oleoyl EFB? fumonisin isomers from a solid culture of Fusarium verticillioides.  

PubMed

The aim of this study was to apply RP-HPLC/ESI-ITMS and RP-HPLC/ESI-TOFMS to investigate and characterise six new higher molecular weight fumonisins (three pairs of isomers) extracted from a Fusarium verticillioides-infected solid rice culture. The ITMS and ITMS² spectra clearly indicated the m/z values (960, 984 and 986) of the protonated molecules and the FB? toxin-like structures of these compounds, respectively. Moreover, the data evaluation software of the TOFMS equipment unambiguously demonstrated the exact masses of the protonated molecules and the suggested empirical formulae (C??H??NO??, C??H??NO?? and C??H??NO??) of the new fumonisins, with mass accuracy in the range between 0.1 and -1.1 ppm. Subtraction of the empirical formula of FB? toxin (C??H??NO??) from these formulae and correction for the mass of water split-off from the fumonisin molecule during ester formation resulted in the empirical formulae of the fumonisin backbone esterifying agents (fatty acids): C??H??O? (palmitic acid, PA), C??H??O? (linoleic acid, LA) and C??H??O? (oleic acid, OA). We denoted the new compounds as esterified FB? (EFB?) toxins, with the suggested names EFB? PA, iso-EFB? PA, EFB? LA, iso-EFB? LA, EFB? OA and iso-EFB? OA. The total amount of these new compounds comprised 0.1% of the FB? concentration, which may be rated as significant when it is considered that these new components are significantly more apolar than earlier-described fumonisins, and their uptake into and toxicity elicited in the various tissues of living organisms may therefore also be significantly different from those of other fumonisins. PMID:21108092

Bartók, T; Tölgyesi, L; Mesterházy, Á; Bartók, M; Szécsi, Á

2010-12-01

82

A Validated RP-HPLC Method for Simultaneous Estimation of Nebivolol and Hydrochlorothiazide in Tablets  

PubMed Central

A simple, selective, rapid, precise and economical reverse phase high pressure liquid chromatographic method has been developed for the simultaneous estimation of nebivolol and hydrochlorthiazide from pharmaceutical formulation. Phenomenex Gemini C18 (25 cm×4.6 mm i.d., 5 ?) column with a mobile phase consisting of acetonitrile: 50mM ammonium acetate (adjusted to pH 3.5 using orthophosphoric acid) (70:30 v/v) at a flow rate of 1.0 ml/min was used. Detection was carried out at 254 nm. Probenecid was used as an internal standard. The retention times of probenecid, nebivolol and hydrochlorthiazide were 13.05, 3.32 and 4.25 min, respectively. The developed method was validated in terms of accuracy, precision, linearity, limit of detection, limit of quantitation and solution stability. The proposed method can be used for the estimation of these drugs in combined dosage forms.

Meyyanathan, S. N.; Rajan, S.; Muralidharan, S.; Birajdar, Arunadevi S.; Suresh, B.

2008-01-01

83

A Validated RP-HPLC Method for Simultaneous Estimation of Nebivolol and Hydrochlorothiazide in Tablets.  

PubMed

A simple, selective, rapid, precise and economical reverse phase high pressure liquid chromatographic method has been developed for the simultaneous estimation of nebivolol and hydrochlorthiazide from pharmaceutical formulation. Phenomenex Gemini C(18) (25 cm×4.6 mm i.d., 5 ?) column with a mobile phase consisting of acetonitrile: 50mM ammonium acetate (adjusted to pH 3.5 using orthophosphoric acid) (70:30 v/v) at a flow rate of 1.0 ml/min was used. Detection was carried out at 254 nm. Probenecid was used as an internal standard. The retention times of probenecid, nebivolol and hydrochlorthiazide were 13.05, 3.32 and 4.25 min, respectively. The developed method was validated in terms of accuracy, precision, linearity, limit of detection, limit of quantitation and solution stability. The proposed method can be used for the estimation of these drugs in combined dosage forms. PMID:21394278

Meyyanathan, S N; Rajan, S; Muralidharan, S; Birajdar, Arunadevi S; Suresh, B

2008-09-01

84

Comparative Study of Ion Interaction Reagents for the Separation of Lanthanides by Reversed-Phase High Performance Liquid Chromatography (RP-HPLC)  

Microsoft Academic Search

A study of two ion interaction reagents (IIRs) viz. n-octadecane sulphonate (C18-sulphonate) and eicosyl sulphate (C20-sulphate) was carried out for the separation of lanthanides by reversed-phase high performance liquid chromatography (RP–HPLC). The objective of the study was to identify a suitable IIR offering long term adsorption onto the RP column, thereby obviating the need to introduce the IIR in the

P. G. Jaison; Pranaw Kumar; Vijay M. Telmore; Suresh K. Aggarwal

2009-01-01

85

ROCK PHOSPHATE AS A NOVEL SOLIDPHASE EXTRACTION ADSORBENT FOR ANALYSIS OF OXALIC ACID IN PLANT XYLEM SAPS BY RP-HPLC  

Microsoft Academic Search

A simple and effective method for elimination the interference from nitrate ions on oxalic acid in RP-HPLC by solid-phase extraction with rock phosphate was developed. Rock phosphate is a cost-effective and environmental friendly mineral material; it exhibited good adsorption ability for oxalic acid, other than nitrate ions, malic, or citric acid, therefore, rock phosphate could be used as an excellent

Lingfei Ni; Wei Wei; Yu Wang; Jing Cui; Zhenggui Wei

2012-01-01

86

Determination of Heavy Metal Ions in Chinese Herbal Medicine by Microwave Digestion and RP-HPLC with UV-Vis Detection  

Microsoft Academic Search

A new method for the simultaneous determination of heavy metal ions in Chinese herbal medicine by microwave digestion and reversed-phase high-performance liquid chromatography (RP-HPLC) has been developed. The Chinese herbal medicine samples were digested by microwave digestion. Lead, cadmium, mercury, nickel, copper, zinc, and tin ions in the digested samples were pre-column derivatized with tetra-(4-chlorophenyl)-porphyrin (T 4-CPP) to form the

Yaling Yang; Yan Guangyu; Qiang Lin

2004-01-01

87

Determination of folic acid by ion-pair RP-HPLC in vitamin-fortified fruit juices after solid-phase extraction  

Microsoft Academic Search

A sensitive and reliable method was developed for the determination of folic acid (FA) in vitamin-fortified fruit juices and fruit drinks. After solid-phase extraction clean-up with strong-anion-exchange material, FA was determined by ion-pair reversed phase high-performance liquid chromatography (RP-HPLC). Limits of detection (LOD) and quantitation (LOQ) were 0.04 and 0.06 mg\\/l, respectively. Average recoveries at two fortified levels (0.5 and

Dietmar E Breithaupt

2001-01-01

88

Using UV-absorbance of intrinsic dithiothreitol (DTT) during RP-HPLC as a measure of experimental redox potential in vitro.  

PubMed

Many in-vitro experiments performed to study the response of thiol-containing proteins to changes in environmental redox potentials use dithiothreitol (DTT) to maintain a preset redox environment throughout the experiments. However, the gradual oxidation of DTT during the course of the experiments, and the interaction between DTT and other components in the system, can significantly alter the initial redox potential and complicate data interpretation. Having an internal reporter of the actual redox potential of the assayed sample facilitates direct correlation of biochemical findings with experimental redox status. Reversed-phase high-performance liquid chromatography (RP-HPLC) is a widely used, well-established tool for analysis and purification of biomolecules, including proteins and peptides. Here, we describe a simple, robust, and quantitative RP-HPLC method we developed and tested for determination of the experimental redox potential of an in-vitro sample at the time of the experiment. It exploits the specific UV-absorbance of the oxidized intrinsic DTT in the samples and retains the high resolving power and high sensitivity of RP-HPLC with UV detection. PMID:23743664

Seo, Angie; Jackson, Janelle L; Schuster, Jolene V; Vardar-Ulu, Didem

2013-06-07

89

RP-HPLC Method for Simultaneous Estimation of Nitazoxanide and Ofloxacin in Tablets  

PubMed Central

A reverse phase high performance liquid chromatography method was developed for simultaneous estimation of nitazoxanide and ofloxacin in tablet formulation. The separation and quantification was achieved by Hiq Sil C18V Size 4.6 mm Ø *250 mm column in isocratic mode, with mobile phase consisting of acetonitrile-methanol-0.4 M citric acid, (60:30:10, v/v/v). Citric acid used to stabilize nitazoxanide and ofloxacin in mobile phase. The mobile phase was pumped at a rate of 0.6 ml/min and the detection was carried out at 304 nm. The retention time of ofloxacin and nitazoxanide was found to be 3.122 and 5.902 min, respectively. The method was validated for linearity, accuracy, and precision. Linearity for ofloxacin and nitazoxanide were in the range 2-36 ?g/ml and 5-90 ?g/ml, respectively. The developed method was found to be accurate, precise and selective for simultaneous estimation of ofloxacin and nitazoxanide in tablets.

Sharma, S.; Bhandari, A.; Choudhary, V. R.; Rajpurohit, H.; Khandelwal, P.

2011-01-01

90

Validation and Uncertainty Estimation of an Ecofriendly and Stability-Indicating HPLC Method for Determination of Diltiazem in Pharmaceutical Preparations  

PubMed Central

A green, simple, and stability-indicating RP-HPLC method was developed for the determination of diltiazem in topical preparations. The separation was based on a C18 analytical column using a mobile phase consisted of ethanol: phosphoric acid solution (pH = 2.5) (35?:?65, v/v). Column temperature was set at 50°C and quantitation was achieved with UV detection at 240?nm. In forced degradation studies, the drug was subjected to oxidation, hydrolysis, photolysis, and heat. The method was validated for specificity, selectivity, linearity, precision, accuracy, and robustness. The applied procedure was found to be linear in diltiazem concentration range of 0.5–50??g/mL (r2 = 0.9996). Precision was evaluated by replicate analysis in which % relative standard deviation (RSD) values for areas were found below 2.0. The recoveries obtained (99.25%–101.66%) ensured the accuracy of the developed method. The degradation products as well as the pharmaceutical excipients were well resolved from the pure drug. The expanded uncertainty (5.63%) of the method was also estimated from method validation data. Accordingly, the proposed validated and sustainable procedure was proved to be suitable for routine analyzing and stability studies of diltiazem in pharmaceutical preparations.

Sadeghi, Fahimeh; Navidpour, Latifeh; Bayat, Sima; Afshar, Minoo

2013-01-01

91

Simultaneous determination of imipramine hydrochloride and chlordiazepoxide in pharmaceutical preparations by spectrophotometric, RP-HPLC, and HPTLC methods.  

PubMed

A binary mixture of imipramine HCl and chlordiazepoxide was determined by three different methods. The first involved determination of imipramine HCl and chlordiazepoxide using the first derivative spectrophotometric technique at 219 and 231.5 nm over the concentration ranges of 1-20 and 2-24 microg/mL with mean accuracies of 99.47 +/- 0.78 and 101.43 +/- 1.20%, respectively. The second method utilized RP-HPLC with methanol-acetonitrile-0.065 M ammonium acetate buffer (45 + 25 + 30, v/v/v, pH adjusted to 5.6 +/- 0.02 with phosphoric acid) as the mobile phase pumped at a flow rate of 1.0 mL/min. Quantification was achieved using UV detection at 240 nm over concentration ranges of 0.25-4.0 and 0.1-1.6 microg/mL, with mean accuracies of 101.17 +/- 0.56 and 100.67 +/- 0.40% for imipramine HCl and chlordiazepoxide, respectively. The third method was HPTLC with carbon tetrachloride-acetone-triethylamine (pH 8.3; 6 + 3 + 0.3, v/v/v) as the mobile phase. Quantification was achieved with UV detection at 240 nm over concentration ranges of 50-600 and 20-240 ng/spot with mean accuracies of 99.51 +/- 0.59 and 100.59 +/- 0.84% for imipramine HCl and chlordiazepoxide, respectively. The suggested procedures were checked using prepared mixtures, and were successfully applied for the analysis of pharmaceutical preparations. The accuracy and precision of the methods were confirmed when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed. PMID:20629393

Patel, Sejal K; Patel, Natvarlal J

92

Retention of Aromatic Sulfur-Containing Compounds on RP-HPLC: Correlation with Partition Coefficients and Molecular Connectivity Indices  

Microsoft Academic Search

The partition coefficients (log Kow) in n-octanol\\/water, together with the HPLC capacity factors (k?) measured on a C18 column, using methanol-water mobile phase of different compositions, were determined for 27 aromatic sulfur-containing compounds. The linear relationship between the log k? values and the percentage of the methanol in the eluent was tested for each compound. The best percentage of methanol

Hui Hong; Dai Zhou; Shuokui Han; Liansheng Wang; Zheng Zhang; Gongwei Zou

1996-01-01

93

Determination of trace lead, cadmium and mercury by on-line column enrichment followed by RP-HPLC as metal-tetra-(4-bromophenyl)-porphyrin chelates  

Microsoft Academic Search

This paper reports the utilization of tetra-(4-bromophenyl)-porphyrin (T4BPP) as a chelating reagent using Waters Xterra™ RP18 column for the on-line column enrichment and the separation of trace lead, cadmium and mercury ions by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detector. When the Hg–T4BPP, Pb–T4BPP and Cd–T4BPP chelates were injected into the injector and sent to the enrichment column

Qiufen Hu; Guangyu Yang; Jiayuan Yin; Yun Yao

2002-01-01

94

Determination of copper, nickel, cobalt, silver, lead, cadmium, and mercury ions in water by solid-phase extraction and the RP-HPLC with UV-Vis detection  

Microsoft Academic Search

A new method for the simultaneous determination of seven heavy metal ions in water by solid-phase extraction and reversed-phase high-performance liquid chromatography (RP-HPLC) was developed. The copper, nickel, cobalt, silver, lead, cadmium, and mercury ions were pre-column derivatized with tetra(m-aminophenyl)porphyrin (Tm-APP) to form colored chelates. The metal-Tm-APP chelates in 100 mL of sample were preconcentrated to 1 mL by solid-phase

Qiufen Hu; Guangyu Yang; Yiyun Zhao; Jiayuan Yin

2003-01-01

95

Effect-directed investigation and interactive effect of organic toxicants in landfill leachates combining Microtox test with RP-HPLC fractionation and GC\\/MS analysis  

Microsoft Academic Search

Landfill leachates contain a large amount of unknown harmful compounds derived from domestic and industrial sources. A toxicity\\u000a effect-directed approach was used to identify biologically active compounds in three landfill leachate samples (S1–S3) by\\u000a combining the Microtox test with reverse-phase high performance liquid chromatography (RP-HPLC) fractionation and gas chromatography\\/mass\\u000a spectrometry (GC\\/MS) analysis. Organic toxicants were recovered from coarse fractions only

Lei Lei; Isao Aoyama

2010-01-01

96

A Rapid, Validated RP-HPLC Method for the Simultaneous Determination of Cleaning Validation and Cross-Contamination of 12 Beta-Lactam Compounds.  

PubMed

The present work reports a rapid reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of 12 beta-lactam components for cleaning validation and cross-contamination. A strategic experimental approach was implemented for the method development. The desired chromatographic separation was achieved on a Symmetry C18 (4.6 X 75 mm, 3.5 ?m) column using gradient elution. The optimized mobile phase consisted of the buffer tetrabutylammonium hydroxide pH-6.8 and acetonitrile. The eluted compounds were monitored at 215 nm and 254 nm wavelength using a photodiode array detector. The developed method separated 12-beta-lactam compounds from each other within a run time of 50 min. The method is effective for the determination of cross-contamination of penicillin and cephalosporin production blocks. The present method is specific and a lower limit of quantification was determined on the basis of the signal-to-noise ratio method; it is 1 ?g/mL for all components. The developed RP-HPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. PMID:23641335

Trivedi, Harshal Kanubhai; Kshtri, Nayan; Patel, Mukesh C

2012-11-17

97

Microwave-assisted extraction followed by RP-HPLC for the simultaneous extraction and determination of forsythiaside A, rutin, and phillyrin in the fruits of Forsythia suspensa.  

PubMed

An optimized microwave-assisted extraction (MAE) method and RP-HPLC method were developed for the simultaneous extraction and determination of rutin, forsythiaside A, and phillyrin in the fruits of Forsythia suspensa. The key parameters of the open-vessel MAE process were optimized. A mixed solvent of methanol and water (70:30, v/v) was most suitable for the simultaneous extraction of the three components. The sample was soaked for 10 min before extraction. The optimized conditions were: microwave power 400 W, temperature 70°C, solvent-to-material ratio 30 mL/g, and extraction time 1 min. Compared to conventional extraction methods, the proposed method can simultaneously extract the three components in high yields and was proved to be a more rapid method with a lower solvent consumption. The optimized HPLC-photodiode array detection analysis was validated to have good linearity, precision, accuracy, and sensitivity. The developed MAE followed by RP-HPLC is a fast and appropriate method for the simultaneous extraction and determination of rutin, forsythiaside A, and phillyrin in the fruits of F. suspensa. PMID:23913652

Fang, Xinsheng; Wang, Yingzi; Wang, Jianhua; Zhang, Jin; Wang, Xin

2013-08-01

98

A Rapid, Validated RP-HPLC Method for the Simultaneous Determination of Cleaning Validation and Cross-Contamination of 12 Beta-Lactam Compounds  

PubMed Central

The present work reports a rapid reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of 12 beta-lactam components for cleaning validation and cross-contamination. A strategic experimental approach was implemented for the method development. The desired chromatographic separation was achieved on a Symmetry C18 (4.6 X 75 mm, 3.5 ?m) column using gradient elution. The optimized mobile phase consisted of the buffer tetrabutylammonium hydroxide pH-6.8 and acetonitrile. The eluted compounds were monitored at 215 nm and 254 nm wavelength using a photodiode array detector. The developed method separated 12-beta-lactam compounds from each other within a run time of 50 min. The method is effective for the determination of cross-contamination of penicillin and cephalosporin production blocks. The present method is specific and a lower limit of quantification was determined on the basis of the signal-to-noise ratio method; it is 1 ?g/mL for all components. The developed RP-HPLC method was validated according to the International Conference on Harmonization (ICH) guidelines.

Trivedi, Harshal Kanubhai; Kshtri, Nayan; Patel, Mukesh C.

2013-01-01

99

Development and validation of RP-HPLC-UV method for simultaneous determination of buparvaquone, atenolol, propranolol, quinidine and verapamil: a tool for the standardization of rat in situ intestinal permeability studies.  

PubMed

A simple, sensitive and specific reversed phase high performance liquid chromatographic (RP-HPLC) method with UV detection at 251 nm was developed for simultaneous quantitation of buparvaquone (BPQ), atenolol, propranolol, quinidine and verapamil. The method was applicable in rat in situ intestinal permeability study to assess intestinal permeability of BPQ, a promising lead compound for Leishmania donovani infections. The method was validated on a C-4 column with mobile phase comprising ammonium acetate buffer (0.02 M, pH 3.5) and acetonitrile in the ratio of 30:70 (v/v) at a flow rate of 1.0 ml/min. The retention times for atenolol, quinidine, propranolol, verapamil and BPQ were 4.30, 5.96, 6.55, 7.98 and 8.54 min, respectively. The calibration curves were linear (correlation coefficient > or =0.996) in the selected range of each analyte. The method is specific and sensitive with limit of quantitation of 15 microg/ml for atenolol, 0.8 microg/ml for quinidine, 5 microg/ml for propranolol, 10 microg/ml for verapamil and 200 ng/ml for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and all the analytes were found to be stable. This method is simple, reliable and can be routinely used for accurate permeability characterization. PMID:17157469

Venkatesh, Gantala; Ramanathan, S; Mansor, S M; Nair, N K; Sattar, Munavvar Abdul; Croft, Simon L; Navaratnam, V

2006-12-08

100

Development and Validation of a Stability-Indicating HPLC Method for the Simultaneous Determination of Sulfadiazine Sodium and Trimethoprim in Injectable Solution Formulation  

PubMed Central

A direct, precise, and stability-indicating HPLC method that is based on reversed-phase liquid chromatography (RP-HPLC) coupled with a photodiode array detector (PDA) was developed, optimized, and validated for the simultaneous determination of sulfadiazine sodium (SDZS) and Trimethoprim (TMP) in Bactizine® forte injectable solution. The separation was achieved using a C18 column (250 mm×4.6 mm i.d., 5 ?m particle size) at room temperature, and an isocratic mobile phase that consisted of a trinary solvent mixture of water–acetonitrile–triethylamine (838:160:2, v/v) at pH 5.5 ± 0.05. The mobile phase was delivered at 1.4 ml/min and the analytes were monitored at 254 nm. The effects of the operational chromatographic conditions on the peak’s USP tailing factor, column efficiency, and resolution were systematically optimized. Forced degradation experiments were carried out by exposing SDZS, TMP standards, and their formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The method was successfully validated in accordance to International Conference on Harmonization (ICH) and United States Pharmacopoeia (USP34/NF29) guidelines and found to be suitable for the quantitative determination and stability of SDZS and TMP in Bactizine® forte injectable solution.

Ghanem, Mashhour M.; Abu-Lafi, Saleh A.

2013-01-01

101

Development and validation of a stability-indicating HPLC method for the simultaneous determination of sulfadiazine sodium and trimethoprim in injectable solution formulation.  

PubMed

A direct, precise, and stability-indicating HPLC method that is based on reversed-phase liquid chromatography (RP-HPLC) coupled with a photodiode array detector (PDA) was developed, optimized, and validated for the simultaneous determination of sulfadiazine sodium (SDZS) and Trimethoprim (TMP) in Bactizine® forte injectable solution. The separation was achieved using a C18 column (250 mm×4.6 mm i.d., 5 ?m particle size) at room temperature, and an isocratic mobile phase that consisted of a trinary solvent mixture of water-acetonitrile-triethylamine (838:160:2, v/v) at pH 5.5 ± 0.05. The mobile phase was delivered at 1.4 ml/min and the analytes were monitored at 254 nm. The effects of the operational chromatographic conditions on the peak's USP tailing factor, column efficiency, and resolution were systematically optimized. Forced degradation experiments were carried out by exposing SDZS, TMP standards, and their formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The method was successfully validated in accordance to International Conference on Harmonization (ICH) and United States Pharmacopoeia (USP34/NF29) guidelines and found to be suitable for the quantitative determination and stability of SDZS and TMP in Bactizine® forte injectable solution. PMID:23641336

Ghanem, Mashhour M; Abu-Lafi, Saleh A

2012-11-22

102

Line stability indices for voltage collapse prediction  

Microsoft Academic Search

Voltage collapse is a problem that occurs in heavily stressed systems. This paper compares the effectiveness of line stability indices in providing information about the proximity of voltage instability of a electrical power system. Line voltage stability indices can provide an accurate information of the stability condition of the lines of the system and can also determine the weakest bus

C. Reis; A. Andrade; F. P. Maciel

2009-01-01

103

Development and Validation of RP-HPLC Method for Simultaneous Estimation of Glimepiride and Sildenafil Citrate in Rat Plasma-Application to Pharmacokinetic Studies.  

PubMed

A simple and sensitive method was developed for simultaneous estimation of Glimepiride (GLIM) and Sildenafil citrate (SIL) in rat Plasma by reverse phase high performance liquid chromatography (RP-HPLC). The drug samples were extracted by liquid-liquid extraction with 300 µl of acetonitrile and 5 ml of diethyl ether. Chromatographic separation was achieved on C18 column using methanol: water (85:15 v/v) as mobile phase at a flow rate of 1 ml/min and UV detection at 230 nm. The retention time of GLIM and SIL was found to be 2.5 and 4.0 min respectively with total run time of 7 min. The developed method was validated for accuracy, precision, linearity and recovery. The method was linear and found to be acceptable over the range of 100-12 000 ng/ml. The method was successfully applied for the analysis of rat plasma sample for application to pharmacokinetic. PMID:23884662

Tripathi, A S; Dewani, A P; Shelke, P G; Bakal, R L; Chandewar, A V; Mazumder, P M

2013-07-24

104

A simple method for simultaneous RP-HPLC determination of indolic compounds related to bacterial biosynthesis of indole-3-acetic acid.  

PubMed

In this short technical report, we present a fast and simple procedure for sample preparation and a single-run Reversed Phase High Performance Liquid Chromatography (RP-HPLC) determination of seven indoles (indole-3-acetic acid, indole-3-acetamide, indole-3-acetonitrile, indole-3-ethanol, indole-3-lactic acid, tryptamine and tryptophan) in bacterial culture supernatants. The separation of the analytes, after a single centrifugal filtration clean-up step, was performed using a gradient elution on a symmetry C8 column followed by fluorimetric detection (?(ex) = 280/?(em) = 350 nm). The calibration curves were linear for all of the studied compounds over the concentration range of 0.0625-125 ?g mL(-1) (r ( 2 ) ? 0.998) and the limits of detection were below 0.015 ?g mL(-1). The applicability of the method was confirmed by analysis of Pseudomonas putida culture supernatants. PMID:23111785

Szkop, Micha?; Bielawski, Wies?aw

2012-10-31

105

Development and validation of RP-HPLC-UV method for simultaneous determination of buparvaquone, atenolol, propranolol, quinidine and verapamil: A tool for the standardization of rat in situ intestinal permeability studies  

Microsoft Academic Search

A simple, sensitive and specific reversed phase high performance liquid chromatographic (RP-HPLC) method with UV detection at 251nm was developed for simultaneous quantitation of buparvaquone (BPQ), atenolol, propranolol, quinidine and verapamil. The method was applicable in rat in situ intestinal permeability study to assess intestinal permeability of BPQ, a promising lead compound for Leishmania donovani infections. The method was validated

Gantala Venkatesh; S. Ramanathan; S. M. Mansor; N. K. Nair; Munavvar Abdul Sattar; Simon L. Croft; V. Navaratnam

2007-01-01

106

Development and Validation of a Stability-Indicating LC-Method for the Simultaneous Estimation of Levodropropizine, Chloropheniramine, Methylparaben, Propylparaben, and Levodropropizine Impurities  

PubMed Central

A simple, fast, and efficient RP-HPLC method has been developed and validated for the simultaneous estimation of Levodropropizine, Chloropheniramine, Methylparaben, Propylparaben, and the quantification of Levodropropizine impurities in the Reswas syrup dosage form. A gradient elution method was used for the separation of all the actives and Levodropropizine impurities by using the X-Bridge C18, 150 mm × 4.6 mm, 3.5 ?m column with a flow rate of 1.0 mL/min and detector wavelength at 223 nm. The mobile phase consisted of a potassium dihydrogen orthophosphate buffer and acetonitrile. All the peaks were symmetrical and well-resolved (resolution was greater than 2.5 for any pair of components) with a shorter run time. The limit of detection for Levodropropizine and its Impurity B was 0.07 ?g/ml & 0.05 ?g/ml, whereas the limit of quantification was 0.19 ?g/ml & 0.15 ?g/ml respectively. The method was validated in terms of precision, accuracy, linearity, robustness, and specificity. Degradation products resulting from the stress studies were well-resolved and did not interfere with the detection of Levodropropizine, Chloropheniramine, Methylparaben, Propylparaben, and Levodropropizine Impurity B, thus the test method is stability-indicating. Validation of the method was carried out as per International Conference on Harmonization (ICH) guidelines.

Kumar, Palakurthi Ashok; Raju, Thummala Veera Raghava; Thirupathi, Dongala; Kumar, Ravindra; Shree, Jaya

2013-01-01

107

A comparison of voltage stability indices  

Microsoft Academic Search

Voltage stability has become a very important issue of power systems analysis. This paper discusses some important aspects related to voltage stability indices in electric power systems. Some techniques previously studied in the literature are analyzed and a comparison of the performance of several indices is presented. The effectiveness of the analyzed methods are demonstrated through numerical studies in IEEE

Claudia Reis; F. P. Maciel Barbosa

2006-01-01

108

Line indices for voltage stability assessment  

Microsoft Academic Search

Voltage stability has become one of the most important issues in electrical power systems. The power system ability to maintain acceptable bus voltage is a very important characteristic of a network. This paper analyzes the performance of line stability indices. These indices were tested in IEEE 14 and IEEE 57 busbar test systems, with satisfactory results. Simulation results show that

F. P. M. Barbosa

2009-01-01

109

A validated RP-HPLC method for simultaneous determination of propranolol and valsartan in bulk drug and gel formulation  

PubMed Central

Objective: A simple, precise, and stability indicating high performance liquid chromatography (HPLC) method was developed and validated for the simultaneous determination of propranolol hydrochloride and valsartan in pharmaceutical dosage form. Materials and Methods: The method involves the use of easily available inexpensive laboratory reagents. The separation was achieved on Hypersil ODS C-18 column (250*4.6 mm, i.d., 5 ?m particle size) with isocratic flow with UV detector. The mobile phase at a flow rate of 1.0 mL/min consisted of acetonitrile, methanol, and 0.01 M disodium hydrogen phosphate (pH 3.5) in the ratio of 50:35:15 v/v. Results: A linear response was observed over the concentration range 5-50 ?g/mL of propranolol and the concentration range 4-32 ?g/mL of valsartan. Limit of detection and limit of quantitation for propranolol were 0.27 ?g/mL and 0.85 ?g/mL, and for valsartan were 0.45 ?g/mL and 1.39 ?g/mL, respectively. The method was successfully validated in accordance to ICH guidelines acceptance criteria for linearity, accuracy, precision, specificity, robustness. Conclusion: The analysis concluded that the method was selective for simultaneous estimation of propranolol and valsartan can be potentially used for the estimation of these drugs in combined dosage form.

Imam, Syed Sarim; Ahad, Abdul; Aqil, Mohammed; Sultana, Yasmin; Ali, Asgar

2013-01-01

110

A stability-indicating reversed-phase high performance liquid chromatography method for simultaneous assay of two corticosteroids and estimation of their related compounds in a pharmaceutical injectable formulation.  

PubMed

Betamethasone Sodium Phosphate and Betamethasone Acetate are the two corticosteroids active pharmaceutical ingredients (APIs) that are present in the injectable formulation, Celestone Chronodose(®) Injection. It is extremely challenging to develop a Quality Control friendly HPLC method to separate all the potential impurities and degradation products of the two APIs from each other using a single HPLC method. A novel stability-indicating reversed-phase HPLC (RP-HPLC) method using two oxo-cyclic organic modifiers in the mobile phase was developed and validated. This method can separate a total of 32 potential impurities and degradation products from the two APIs and also from each other. Peak symmetry and separation efficiency were enhanced by using two chaotropic agents (trifluoroacetic acid and potassium hexafluorophosphate) in the mobile phases of this method. The stability-indicating capability of this method has been demonstrated by analyzing aged and stressed degraded stability samples of the drug product. This method uses an ACE 3 C18 (15 cm × 4.6 mm) HPLC column. The method was validated per ICH guidelines and proved to be suitable for routine QC use. PMID:20855075

Lu, Jun; Wei, Yuchien; Rustum, Abu M

2010-09-18

111

Effects of ionic liquid as additive and the pH of the mobile phase on the retention factors of amino benzoic acids in RP-HPLC.  

PubMed

As an organic salt, ionic liquids are widely used as new solvent media. In this paper, three positional isomers, such as o-amino benzoic acid, m-amino benzoic acid, and p-amino benzoic acid are separated with four different ionic liquids as additives to the mobile phase using reversed-phase (RP) high-performance liquid chromatography (HPLC). Amino benzoic acids are biologically active substances; the p-isomer is present in a group of water-soluble vitamins and is widely known as a sunscreen agent. The ionic liquids used are 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium methylsulfate, and 1-octyl-3-methylimidazolium methylsulfate. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of the ionic liquid, and the effect of the pH of the mobile phase on the retention factor of the amino benzoic acid isomers are studied. Separation with the ionic liquid in the eluent was better than the separation without the ionic liquid. The pH mainly affected the retention and elution order of the solutes in RP-HPLC. PMID:17555633

Zheng, J; Polyakova, Y; Row, K H

112

Determination of free and bound phenolic compounds in buckwheat spaghetti by RP-HPLC-ESI-TOF-MS: effect of thermal processing from farm to fork.  

PubMed

Nowadays there is considerable interest in the consumption of alternative crops as potential recipes for gluten-free products production. Therefore, the use of buckwheat for the production of gluten-free pasta has been investigated in the present study. RP-HPLC-ESI-TOF-MS has been applied for the separation and characterization of free and bound phenolic compounds in buckwheat flour and buckwheat spaghetti. Thus, 32 free and 24 bound phenolic compounds in buckwheat flour and spaghetti have been characterized and quantified. To the authors' knowledge, protochatechuic-4-O-glucoside acid and procyanidin A have been detected in buckwheat for the first time. The results have demonstrated a decrease of total free phenolic compounds from farm to fork (from flour to cooked spaghetti) of about 74.5%, with a range between 55.3 and 100%, for individual compounds. The decrease in bound phenols was 80.9%, with a range between 46.2 and 100%. The spaghetti-making process and the cooking caused losses of 46.1 and 49.4% of total phenolic compounds, respectively. Of the total phenolic compounds present in dried spaghetti, 11.6% were dissolved in water after cooking. PMID:21678994

Verardo, Vito; Arraez-Roman, David; Segura-Carretero, Antonio; Marconi, Emanuele; Fernandez-Gutierrez, Alberto; Caboni, Maria Fiorenza

2011-06-28

113

Simultaneous determination of multi drug components Theophylline, Etofylline, Guaiphenesine and Ambroxol Hydrochloride by validated RP-HPLC method in liquid dosage form.  

PubMed

The RP-HPLC (reverse phase high performance liquid chromatography) method was developed and validated for simultaneous determination of Multi drug components i.e., Theophylline, Etofylline, Guaiphenesine and Ambroxol Hydrochloride in a liquid dosage form. Chromatographic separation of the four drugs was performed on a Hypersil Phenyl BDS (25cmX4.6mm, 5mm). The mobile phase constituted of triethylamine pH 3.0 buffer: methanol (85:15) v/v was delivered at the flow rate 1.5 mL/min. Detection was performed at 235 nm. The peak purity of Theophylline, Etofylline, Guaiphenesine and Ambroxol Hydrochloride were 0.99970, 0.99979, 0.99986 and 0.99949 respectively. Calibration curves were linear with correlation coefficient between 0.99995 to 0.99997 over a concentration range of 5 to 37 microg/mL for Theophylline, 19 to 140 microg/mL for Etofylline, 20 to 149 microg/mL for Guaiphenesine and 6 to 45 microg/mL for Ambroxol hydrochloride. The relative standard deviation (RSD) was found < 2.0%. The percentage recovery was found between the range of 98.6% and 100.5% at three different levels. Robustness and ruggedness were performed and result found within the RSD of 2%. All the parameters of validation were found in the acceptance range of ICH guideline. PMID:18390446

Jain, Jainendra Kumar; Prakash, M S; Mishra, Rajnish K; Khandhar, Amit P

2008-04-01

114

Simultaneous and rapid determination of the anticarcinogenic proteins Bowman-Birk inhibitor and lectin in soybean crops by perfusion RP-HPLC.  

PubMed

There are numerous studies demonstrating a direct association between the ingestion of soybean and low cancer incidence. This fact has been related to the presence of Bowman-Birk inhibitor (BBI) and lectin in soybean. The simultaneous and fast determination of BBI and lectin in soybean is proposed, for the first time, in this work. Two different strategies were designed for the extraction of BBI and lectin: extraction of soybean proteins using a Tris-HCl buffer followed by isolation of BBI and lectin by the isoelectric precipitation of other soybean proteins (method I) or by the direct extraction of BBI and lectin using an acetate buffer (method II). The effect of the previous soybean defating on the extraction of BBI and lectin was also studied. Moreover, the possibility of using a high-intensity focalized ultrasonic probe for accelerating the extraction was explored and an optimization of the extraction time and ultrasound amplitude was performed. The extracts obtained were analysed by RP-HPLC-ESI-MS for the correct identification of BBI and lectin in soybean. Moreover, a fast chromatographic methodology using a perfusion column and UV detection was optimized for the rapid determination of BBI and lectin in soybean. After evaluating its analytical characteristics (linearity, precision, and recovery), the method was applied to the quantitation of BBI and lectin in different soybean varieties. PMID:20889157

Anta, Lucía; Luisa Marina, M; García, M Concepción

2010-09-17

115

Voltage stability indices for stressed power systems  

Microsoft Academic Search

The use of static voltage stability indices based on a singular value decomposition of the power flow Jacobian matrix and matrices derived from the Jacobian matrix is discussed. It is shown that such indices, together with the singular vectors, contain substantial and important information about the proximity to voltage instability and also about critical buses and disturbances from a voltage

P. A. Loef; G. Andersson; D. J. Hill

1993-01-01

116

Development and validation of a RP-HPLC method for the determination of gentamicin sulfate and its related substances in a pharmaceutical cream using a short pentafluorophenyl column and a Charged Aerosol Detector  

Microsoft Academic Search

Gentamicin sulfate is a potent broad spectrum aminoglycoside antibiotic which is used as an active pharmaceutical ingredient (API) against both Gram-positive and Gram-negative bacteria. A reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed and validated to determine the composition of gentamicin sulfate and to estimate its related substances (without any pre- or post-column derivatization) in a pharmaceutical cream.

Arul Joseph; Abu Rustum

2010-01-01

117

The effect of eluent pH and compound acid–base character on the design of generic-gradient reversed-phase high-performance liquid chromatography (RP-HPLC) methods for use in drug discovery  

Microsoft Academic Search

The design of generic reversed-phase high-performance liquid chromatography (RP-HPLC) gradient methods for the analysis of compound mixtures or ‘cocktails’ has been investigated with particular reference to the eluent pH and the type of compound (acid, base or neutral) analysed. The use of eluents with an acidic eluent pH, an approach which is widely employed, can lead to non-retention of polar

Brian Law

2004-01-01

118

A validated RP-HPLC method for the determination of mosapride citrate in bulk drug samples and pharmaceutical formulations.  

PubMed

Mosapride citrate, a selective serotonin 5-HT4 agonist, is a novel and potent gastroprokinetic drug. So far no assay procedure has been reported for the estimation of this drug either in bulk drug samples, pharmaceutical formulations or in biological samples. A rapid and sensitive high-performance liquid chromatographic method was developed for the estimation of mosapride citrate in bulk drug samples and pharmaceutical dosage forms. Risperidone was used as an internal standard (ISD). A HPLC system consisting of gradient pump, reverse phase C-18 analytical column, a variable UV-visible detector set at 274 nm and an integrator was used. The mobile phase consisted of acetonitrile: 0.02 M potassium dihydrogen phosphate buffer (pH adjusted to 4.0 with o-phosphoric acid) in the ratio of 50:50 (v/v), and was pumped at 1 ml/min at 40 degrees C. The drug and ISD were eluted at 8.10 and 2.27 min, respectively. The peak drug/ISD area ratio versus drug concentration relationship was linear (r = 0.9998). The method was validated for its linearity, precision and accuracy. The calibration curve was linear in the range of 0.5 to 30 micrograms/ml. The lower detection limit was found to be 0.23 microgram/ml. The intra- and inter-day variation was found to be less than 1% showing high precision of the assay method. The mean recovery of the drug from the solutions containing 2, 4 or 10 micrograms/ml was 101.55 +/- 0.97% indicating high accuracy of the proposed HPLC method. PMID:12561242

Krishnaiah, Y S R; Murthy, T K; Sankar, D G; Satyanarayana, V

2002-12-01

119

On the stability of value added indicators  

Microsoft Academic Search

This paper shows how relevant concepts in educational effectiveness can support public policy in order to improve the performance\\u000a of educational systems. Specifically, value-added indicators and the property of their stability over time is addressed with\\u000a reference to application to school\\/teacher improvement. Findings of a longitudinal study developed in Portugal concerning\\u000a primary education in mathematics are presented. Variance component models

Maria Eugénia Ferrão

2012-01-01

120

Validated stability-indicating methods for the simultaneous determination of amiloride hydrochloride, atenolol, and chlorthalidone using HPTLC and HPLC with photodiode array detector.  

PubMed

Two stability-indicating chromatographic methods are described for simultaneous determination of amiloride hydrochloride (AMI), atenolol (ATE), and chlorthalidone (CHL) in combined dosage forms. The first method was based on HPTLC separation of the three drugs followed by densitometric measurements of their bands at 274 nm. The separation was carried out on Merck HPTLC silica gel 60F254 aluminum sheets using chloroform-methanol-ammonia 27%, w/w (9 + 2 + 0.3, v/v/v) mobile phase. Analysis data was used for the linear regression graph in the range of 0.1-0.5, 0.8-5.0, and 0.3-1.5 microg/band for AMI, ATE, and CHL, respectively. The second method was based on an RP-HPLC separation of the cited drugs performed on an RP stainless steel C18 analytical column (250 x 4.6 mm id) with a gradient elution system of methanol and 0.05 M aqueous phosphate buffer adjusted to pH 4 as the mobile phase, at the flow rate of 1.0 mL/min. Quantitation was achieved with photodiode array detection at 275 nm for AMI and 225 nm for ATE and CHL. The calibration graphs for each drug were rectilinear in the range of 2-50, 25-150, and 2-100 microg/mL for AMI, ATE, and CHL, respectively. The proposed chromatographic methods were successfully applied for determination of the investigated drugs in pharmaceutical preparations. Both methods were validated in compliance with International Conference on Harmonization guidelines in terms of linearity, accuracy, precision, robustness, LOD, and LOQ. PMID:23767356

Youssef, Rasha M; Maher, Hadir M; El-Kimary, Eman I; Hassan, Ekram M; Barary, Magda H

121

Stability Indicating HPTLC Determination of Meloxicam.  

PubMed

A simple, selective, precise and stability-indicating high-performance thin layer chromatographic method of analysis of meloxicam both as a bulk drug and in formulation has been developed. The mobile phase selected was ethyl acetate:cyclohexane:glacial acetic acid (6.5:3.5:0.02% v/v/v). The calibration curve of the drug was linear in the range of 100-500 ng. The spectrodensitometric analysis was carried out in the absorbance mode at 353 nm. The mean (±RSD) values of slope, correlation coefficient and intercept were 3183.8±0.358, 0.9996±0.0321 and 13012±7.1 respectively. The system precision and the method precision studies were carried out with RSD of 0.83 and 1.89 respectively. The limit of detection and quantitation were 30 ng and 99 ng respectively. The mean percent recovery was found to be 100.3%. The method was used to analyze meloxicam from marketed tablet formulation in the presence of commonly used excipients. PMID:21394264

Desai, Namita; Amin, Purnima

2008-09-01

122

Climatology of Stability Indices for Cincinnati Ohio  

NASA Astrophysics Data System (ADS)

Three of the top five worst tornado outbreaks in U.S. history occurred between January and May 2011. Some may make the hypothesis that this is due to climate change. To explore methods for testing this theory, the changes in decadal averages of numbers of severe thunderstorm days in the metropolitan area of Cincinnati were examined. This area was chosen due to its high population and its location near the jet stream and Tornado Alley. Three stability indices were chosen from all 0Z soundings during the last 30 years: the Lifted Index, the K-Index and Convective Available Potential Energy. The decadal and 30-year averages of monthly, seasonal, and annual percentages of possible severe thunderstorm days were first derived. Afterword, an examination of the decadal averages revealed some trends. The results showed the month of July having the highest number of possible severe weather days. The frequency of possible severe thunderstorm days increased during the summer, while the winter had hardly any severe weather. The spring, summer, and fall averages for the decade of 2001-2010 were always higher than their 30-year climate normals. These findings are consistent with an increase in the frequency of severe thunderstorms over the past few decades, but more study is needed.

Burger, M. A.; Durre, I.

2011-12-01

123

Stability Indicating HPTLC Determination of Meloxicam  

PubMed Central

A simple, selective, precise and stability-indicating high-performance thin layer chromatographic method of analysis of meloxicam both as a bulk drug and in formulation has been developed. The mobile phase selected was ethyl acetate:cyclohexane:glacial acetic acid (6.5:3.5:0.02% v/v/v). The calibration curve of the drug was linear in the range of 100-500 ng. The spectrodensitometric analysis was carried out in the absorbance mode at 353 nm. The mean (±RSD) values of slope, correlation coefficient and intercept were 3183.8±0.358, 0.9996±0.0321 and 13012±7.1 respectively. The system precision and the method precision studies were carried out with RSD of 0.83 and 1.89 respectively. The limit of detection and quantitation were 30 ng and 99 ng respectively. The mean percent recovery was found to be 100.3%. The method was used to analyze meloxicam from marketed tablet formulation in the presence of commonly used excipients.

Desai, Namita; Amin, Purnima

2008-01-01

124

An optimized fast voltage stability indicator  

Microsoft Academic Search

This paper proposes a simulated annealing optimization technique for optimal voltage stability profile throughout the whole power network. The technique is applied to control the power elements of major influence on the voltage stability profile. Elements such as generator reactive generation, adjustable shunt compensation devices and transformer tap settings are optimally adjusted to reach the objective of minimizing the voltage

C. A. Belhadj; M. A. Abido

1999-01-01

125

Stability Indicators for Nutrient Cycles in Ecosystems.  

National Technical Information Service (NTIS)

A variety of models for nutrient cycling in ecosystems are examined, both numerically and analytically, to determine ecosystem responses to perturbations. The structure of the decomposer-detritus dynamics is found to play a governing role in the stability...

M. Dudzik J. Harte D. Levy J. Sandusky

1975-01-01

126

Sensitivity of stability indices to force uncertainties  

SciTech Connect

Additional or hidden weapons in the possession of the side with the largest fraction of vulnerable weapons can improve stability. Vulnerable weapons contribute primarily at the end of force reduction; survivable weapons contribute throughout the transition.

Canavan, G.H.

1997-07-01

127

Sensitivity of stability indices to force uncertainties  

Microsoft Academic Search

Additional or hidden weapons in the possession of the side with the largest fraction of vulnerable weapons can improve stability. Vulnerable weapons contribute primarily at the end of force reduction; survivable weapons contribute throughout the transition.

Canavan

1997-01-01

128

Comprehensive Assessment of Degradation Behavior of Aspirin and Atorvastatin Singly and in Combination by Using a Validated RP-HPLC Method.  

PubMed

A fixed-dose combination of atorvastatin and aspirin is widely used for the treatment of myocardial infarction. The present work describes a comprehensive study of the stress degradation behavior of atorvastatin and aspirin alone as well as in combination of 1:1 and 1:7.5 ratios, respectively, as per ICH guidelines. The degradation products of aspirin as well as atorvastatin were successfully separated by a developed simple, selective, and precise stability-indicating reversed-phase HPLC method. Chromatographic separation was achieved on the Phenomenex Luna analytical column, 150 mm × 4.6 mm, 5?m. The mobile phase consisted of 0.1% glacial acetic acid in water and acetonitrile in the ratio of 50:50 v/v at a flow rate of 1.0 ml/min. UV detection was performed at 246 nm. The extent of degradation was significantly influenced when both of the drugs were present in combination. Stress degradation behavior of atorvastatin was highly influenced by aspirin under acid hydrolysis, thermal degradation, and oxidative stress conditions. Similarly, the stress degradation behavior of aspirin was affected by atorvastatin especially under neutral hydrolysis, thermal degradation, and oxidative stress conditions. Additionally, the combination ratio of aspirin and atorvastatin also influenced the percentage degradation of each other. A mixture of aspirin and atorvastatin was also analyzed after a one-month stability study at 40 °C and 75% RH. All the results indicate chemical incompatibility of both aspirin and atorvastatin if present in combination. PMID:23641338

Sherikar, Omkar; Mehta, Priti

2012-12-11

129

Comprehensive Assessment of Degradation Behavior of Aspirin and Atorvastatin Singly and in Combination by Using a Validated RP-HPLC Method  

PubMed Central

A fixed-dose combination of atorvastatin and aspirin is widely used for the treatment of myocardial infarction. The present work describes a comprehensive study of the stress degradation behavior of atorvastatin and aspirin alone as well as in combination of 1:1 and 1:7.5 ratios, respectively, as per ICH guidelines. The degradation products of aspirin as well as atorvastatin were successfully separated by a developed simple, selective, and precise stability-indicating reversed-phase HPLC method. Chromatographic separation was achieved on the Phenomenex Luna analytical column, 150 mm × 4.6 mm, 5?m. The mobile phase consisted of 0.1% glacial acetic acid in water and acetonitrile in the ratio of 50:50 v/v at a flow rate of 1.0 ml/min. UV detection was performed at 246 nm. The extent of degradation was significantly influenced when both of the drugs were present in combination. Stress degradation behavior of atorvastatin was highly influenced by aspirin under acid hydrolysis, thermal degradation, and oxidative stress conditions. Similarly, the stress degradation behavior of aspirin was affected by atorvastatin especially under neutral hydrolysis, thermal degradation, and oxidative stress conditions. Additionally, the combination ratio of aspirin and atorvastatin also influenced the percentage degradation of each other. A mixture of aspirin and atorvastatin was also analyzed after a one-month stability study at 40 °C and 75% RH. All the results indicate chemical incompatibility of both aspirin and atorvastatin if present in combination.

Sherikar, Omkar; Mehta, Priti

2013-01-01

130

Validation of a RP-HPLC method for the assay of formoterol and its related substances in formoterol fumarate dihydrate drug substance.  

PubMed

A stability-indicating reversed-phase high performance liquid chromatographic (HPLC) method has been developed and validated for the assay of formoterol fumarate and the related substances, namely, formoterol fumarate desformyl and formoterol fumarate acetamide analogs, in the active pharmaceutical ingredient. The separation was achieved by isocratic elution using an Alltech Alltima C18 (150 x 4.6 mm) column, a mobile phase consisting of ammonium acetate (50 mM; pH 5.0)-ethanol (65:35, v/v), a flow rate of 1.0 ml/min and UV detection at 242 nm. The detection and quantitation limits were 0.03 and 08 microg/ml, respectively, while the linear range of detection was between 0.03 and 255 microg/ml. Comparative determinations of formoterol fumarate in three lots of bulk drugs using the proposed HPLC method and the standard potentiometric titration method of pharmacopoeia show that both methods are equivalent for pure drug substance assay. However, the HPLC method allowed the separation and quantitation of the impurities not achievable with the official methods in the bulk drugs. This study shows that the proposed method is accurate, linear, and sensitive as stability indicating assay method for formoterol fumarate in the bulk drug. PMID:14656584

Akapo, Samuel O; Asif, Muhammad

2003-12-01

131

Voltage stability calculations in power transmission lines: Indications and allocations  

Microsoft Academic Search

In recent years, voltage stability problems have been increasing since power systems operate close to stability limits and large amounts of power are being transferred from long distance. Accurate determination of voltage collapse points with rapid line voltage stability analysis, indications and allocations, allows operators to take necessary action to prevent such collapse incidents. Although several methods have been used

F. A. Althowibi; M. W. Mustafa

2010-01-01

132

Evaluation of voltage stability indices (VSI) using genetic algorithm  

Microsoft Academic Search

In this paper, three voltage stability indices (VSIs) have been assessed. The voltage stability problem has been formulated as an optimization problem. Genetic algorithm (GA) has been employed to solve this optimization problem. Wale & Hale 6 bus system was used in this paper study.

Muhammad Tami Al-Hajri; M. A. Abido

2010-01-01

133

Accuracy analysis of fixed voltage setpoint indices for voltage stability  

Microsoft Academic Search

There are many voltage stability indices for voltage security assessment and calculating stable margins from operating points to voltage instability at each load bus. Among them, one type of indices based on fixed voltage setpoint is applied in practice. Previous research has proved inaccuracy of these indices with the P-V curve method. This paper aims to verify the accuracy of

Sun Huadong; Tang Yong; Bu Guangquan

2010-01-01

134

Evaluation of some indices for voltage stability assessment  

Microsoft Academic Search

The liberalization of the electricity markets causes power systems to work closer and closer to their limits. The online assessment of system security becomes a topic of paramount importance in control centers. In this context fast indices to quickly assess system security are fundamental in an on-line DSA session. This paper considers three voltage stability indices recently proposed in literature

S. Massucco; S. Grillo; A. Pitto; F. Silvestro

2009-01-01

135

Optimization and validation of RP-HPLC-UV method with solid-phase extraction for determination of buparvaquone in human and rabbit plasma: application to pharmacokinetic study.  

PubMed

A simple, sensitive and specific reversed-phase high-performance liquid chromatographic method with UV detection at 251 nm was developed for quantitation of buparvaquone (BPQ) in human and rabbit plasma. The method utilizes 250 microL of plasma and sample preparation involves protein precipitation followed by solid-phase extraction. The method was validated on a C18 column with mobile phase consisting of ammonium acetate buffer (0.02 m, pH 3.0) and acetonitrile in the ratio of 18:82 (v/v) at a flow rate of 1.1 mL/min. The calibration curves were linear (correlation coefficient>or=0.998) in the selected range. The method is specific and sensitive with limit of quantitation of 50 ng/mL for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and BPQ was found to be stable. Partial validation studies were carried out using rabbit plasma and intra- and inter-day precision and accuracy were within 7%. This method is simple, reliable and can be routinely used for preclinical pharmacokinetic studies for BPQ. PMID:18205140

Venkatesh, Gantala; Majid, M I A; Ramanathan, S; Mansor, S M; Nair, N K; Croft, Simon L; Navaratnam, V

2008-05-01

136

Simultaneous determination of phenolic acids and flavonoids in rice using solid-phase extraction and RP-HPLC with photodiode array detection.  

PubMed

An analytical method based on an optimized solid-phase extraction procedure and followed by high-performance liquid chromatography (HPLC) separation with diode array detection was developed and validated for the simultaneous determination of phenolic acids (gallic, protocatechuic, 4-hydroxy-benzoic, vanillic, caffeic, syringic, p-coumaric, ferulic, sinapic, and cinnamic acids), flavanols (catechin and epicatechin), flavonols (myricetin, quercetin, kaempferol, quercetin-3-O-glucoside, hyperoside, and rutin), flavones (luteolin and apigenin) and flavanones (naringenin and hesperidin) in rice flour (Oryza sativa L.). Chromatographic separation was carried out on a PerfectSil Target ODS-3 (250 mm × 4.6 mm, 3 ?m) column at temperature 25°C using a mobile phase, consisting of 0.5% (v/v) acetic acid in water, methanol, and acetonitrile at a flow rate 1 mL min(-1) , under gradient elution conditions. Application of optimum extraction conditions, elaborated on both Lichrolut C(18) and Oasis HLB cartridges, have led to extraction of phenolic acids and flavonoids from rice flour with mean recoveries 84.3-113.0%. The developed method was validated in terms of linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 5) and inter-day precision (n = 4) revealed relative standard deviation (RSD) <13%. The optimized method was successfully applied to the analysis of phenolic acids and flavonoids in pigmented (red and black rice) and non-pigmented rice (brown rice) samples. PMID:22761138

Irakli, Maria N; Samanidou, Victoria F; Biliaderis, Costas G; Papadoyannis, Ioannis N

2012-07-01

137

Quantitative and Chemical Fingerprint Analysis for the Quality Evaluation of Receptaculum Nelumbinis by RP-HPLC Coupled with Hierarchical Clustering Analysis  

PubMed Central

A simple and reliable method of high-performance liquid chromatography with photodiode array detection (HPLC-DAD) was developed to evaluate the quality of Receptaculum Nelumbinis (dried receptacle of Nelumbo nucifera) through establishing chromatographic fingerprint and simultaneous determination of five flavonol glycosides, including hyperoside, isoquercitrin, quercetin-3-O-?-d-glucuronide, isorhamnetin-3-O-?-d-galactoside and syringetin-3-O-?-d-glucoside. In quantitative analysis, the five components showed good regression (R > 0.9998) within linear ranges, and their recoveries were in the range of 98.31%–100.32%. In the chromatographic fingerprint, twelve peaks were selected as the characteristic peaks to assess the similarities of different samples collected from different origins in China according to the State Food and Drug Administration (SFDA) requirements. Furthermore, hierarchical cluster analysis (HCA) was also applied to evaluate the variation of chemical components among different sources of Receptaculum Nelumbinis in China. This study indicated that the combination of quantitative and chromatographic fingerprint analysis can be readily utilized as a quality control method for Receptaculum Nelumbinis and its related traditional Chinese medicinal preparations.

Wu, Yan-Bin; Zheng, Li-Jun; Yi, Jun; Wu, Jian-Guo; Chen, Ti-Qiang; Wu, Jin-Zhong

2013-01-01

138

Rapid determination of total solanesol in tobacco leaf by ultrasound-assisted extraction with RP-HPLC and ESI-TOF/MS.  

PubMed

A reliable and rapid method based on high-performance liquid chromatography (HPLC-UV) and positive ion electrospray-time of flight mass spectrometry (ESI-TOF/MS) has been developed for the characterization and quantification of solanesol in extracts of tobacco leaves from different sources. The solanesol was extracted from tobacco leaf via saponification and ultrasonic-assist extraction, and the extraction conditions were optimized. The HPLC conditions are as following: Hypersil C(4) (4.6 mm x 150 mm, 5 microm) column, acetonitrile and water as mobile phase, flow-rate is 0.8 ml/min, detection length of UV is 202 nm, injection volume is 10 microl. The results indicated that the developed HPLC method is simple, sensitive and reliable for the determination of solanesol in tobacco leaves with a linear dynamic range of 3.65-4672 ng, a detection limit of 1.83 ng, and an average recovery of 98.7%. The method has been applied to analyze and compare different tobacco samples. The results show that the solanesol content in samples of different geographic locations varies widely from 0.20 to 1.50%. When different parts of the tobacco plant are compared, the top parts of the leaves are more abundant in solanesol content than those of lower parts. PMID:17029669

Chen, Junhui; Liu, Xianping; Xu, Xiaoqin; Lee, Frank Sen-Chun; Wang, Xiaoru

2006-10-06

139

CIELAB color variables as indicators of compost stability.  

PubMed

The composting process of different organic wastes both in laboratory and on a large-scale was characterized using CIELAB color variables to evaluate compost stability for the better application in agriculture. The time courses of the CIELAB variables of composting materials were determined directly from the bottom of a glass petri dish filled with dried and ground samples using a Minolta Color Reader (CR-13) calibrated with clean empty petri dishes placed on a white tile. To compare the proposed method with conventional methods, the same materials were also evaluated using commonly used compost stability evaluation indices. Most of the CIELAB variables of a compost made from a mixture of green tea waste and rice bran reached a plateau after 84 days of composting and showed strong relationships with the commonly used compost stability evaluation indices. The time needed for CIELAB variables, especially the L*and b* values, to stabilize at large-scale composting plants of cattle litter, farmyard manure, kitchen garbage and bark compost, were more or less similar to the times of maturation evaluated by the respective compost producers. The CIELAB color variable offers a new, simple, rapid and inexpensive means of evaluating compost stability and its quality prior to agricultural use. PMID:19781930

Khan, Mohammad Ashik Iqbal; Ueno, Kihachi; Horimoto, Sakae; Komai, Fuminori; Someya, Takashi; Inoue, Koichi; Tanaka, Kinji; Ono, Yoshitaka

2009-09-24

140

Stability of vitamin C derivatives in solution and topical formulations  

Microsoft Academic Search

The stability of ascorbic acid, ascorbyl palmitate and magnesium ascorbyl phosphate (VC-PMG®) in both standard solutions and topical formulations was investigated by direct RP-HPLC analysis after sample dilution with a suitable aqueous-organic solvent mixture. The results showed that, whereas the two vitamin C derivatives were more stable than ascorbic acid, the ascorbyl esters showed significant differences. Esterification with palmitic acid

R. Austria; A. Semenzato; A. Bettero

1997-01-01

141

Test of the Hill Stability Criterion against Chaos Indicators  

NASA Astrophysics Data System (ADS)

The efficacy of Hill Stability (HS) criterion is tested against other known chaos indicators such as Maximum Lyapunov Exponents (MLE) and Mean Exponential Growth of Nearby Orbits (MEGNO) maps. First, orbits of four observationally verified binary star systems: ? Cephei, Gliese-86, HD41004, and HD196885 are integrated using standard integration packages (MERCURY, SWIFTER, NBI, C/C++). The HS which measures orbital perturbation of a planet around the primary star due to the secondary star is calculated for each system. The LEs spectra are generated to measure the divergence/convergence rate of stable manifolds and the MEGNO maps are generated by using the variational equations of the system during the integration process. These maps allow to accurately differentiate between stable and unstable dynamical systems. Then the results obtained from the analysis of HS, MLE, and MEGNO maps are checked for their dynamical variations and resemblance. The HS of most of the planets seems to be stable, quasi-periodic for at least ten million years. The MLE and the MEGNO maps also indicate the local quasi-periodicity and global stability in relatively short integration period. The HS criterion is found to be a comparably efficient tool to measure the stability of planetary orbits.

Satyal, Suman; Quarles, Billy; Hinse, Tobias

2012-10-01

142

Stability Indices derived from Atmospheric Measurements on a Cable Car  

NASA Astrophysics Data System (ADS)

Stability indices are meteorological parameters to describe vertical atmospheric layering and therefore it is possible to predict convective events such as thunderstorms. Commonly, weather balloons with radiosondes are used for the analysis of vertical atmospheric layering. These weather balloons reach high altitudes and atmospheric layering can be determined for the entire troposphere. On the other hand, these balloon ascents are expensive, require the appropriate equipment and permissions and cannot be conducted several times a day on an operational basis. Due to the limitations of the application of weather balloons the unconventional idea came up to equip a cable car with meteorological instruments for vertical profile measurements. To some extent the meteorological instruments had to be customized to the particular requirements and data are transmitted via GSM. The investigated area is a small alpine catchment which is prone to flash floods and thus a reliable forecast for such floods mostly caused by convective rainfall events is important. Therefore the purpose of this contribution is to proof if a cable car can be used for measuring continuous data during the operating hours and whether it is possible to derive reliable conclusions about the stability in the lower troposphere. Several stability indices (e.g. Lifted-, Showalter-, Boyden- and Convective-Index) were investigated. Indices which are calculated on the basis of the "Lifted Parcel Theory" were tested with different approaches to determine the most unstable parcel and therefore the initial values of the required parameters. The derived indices were flagged in active (thunderstorms) and non-active (no thunderstorms) cases. The classification results from available lightning maps in this region. Threshold values were established to distinguish stable, potential indifferent and unstable atmospheric conditions. On the basis of this division pre-warnings for the occurrence of thunderstorms are declared. The verification of the quality of these predictions is done by a skill score statistic.

Herma, F.; Seidel, J.; Bárdossy, A.

2012-04-01

143

Determination of zafirlukast by stability indicating LC and derivative spectrophotometry.  

PubMed

Two analytical methods have been developed for the determination of zafirlukast, a novel anti-asthmatic drug: high performance liquid chromatography (HPLC) and derivative spectrophotometry (DS). HPLC with ultraviolet detection at 225 nm is carried out with a Symmetry Shield RP18 column and a mobile phase constituted of acetonitrile and 0.01 M potassium dihydrogen phosphate buffer, adjusted the pH to 3.5 with 0.1 M KOH. The LC method is simple, rapid, selective and stability indicating. Indole was used as internal standard for the purpose of quantification of zafirlukast in HPLC. Spectrophotometry uses the third order derivative of the UV spectrum at 251.1 nm (deltalambda value 2.1 nm) for determination. Both methods were fully validated and a comparison was made. The results confirm that the methods are highly suitable for its intended purpose. PMID:12367695

Radhakrishna, T; Satyanarayana, J; Satyanarayana, A

2002-10-15

144

Respiration indices and stability measurements of compost through electrolytic respirometry.  

PubMed

An experimental technique for compost stability measurements based on Sapromat electrolytic respirometry was optimised and subsequently applied to a sludge composting process. Anaerobically digested sewage sludge mixed with reed was composted during 90 days in a pilot-scale rotary drum with forced aeration. Periodic solid samples were taken, and a previously optimised respirometric procedure was applied in order to measure the oxygen consumption. The respirometric experiments were made directly with a few grams of solid samples, optimum moisture and 37 °C over a period of 96 h. The results obtained showed how the respiration activity of the sludge decreased during the composting experiment under the specific operating conditions. The specific oxygen uptake rate (SOUR) instant values from the oxygen consumption curves were obtained, and two commonly used respirometric indexes (RI(24) and AT(4)) were calculated for all samples. Both RI(24) (a mean of the SOUR values during the 24 h maximum activity period) and AT(4) (total oxygen consumption after 4 days) were the recommended parameters for the estimation of compost stability by the European Union in the second draft of the Working Document on the Biological Treatment of Biowaste in 2001. Both indexes exponentially decreased with the composting time, and a good linear correlation between them was observed. Final values of RI(24) and AT(4) after 90 days were 600 mg O(2) kg VS(-1) h(-1) and 26 mg O(2) gTS(-1), respectively. We also considered if this technique could be classified as a Dynamic or Static method, the two primary respirometric techniques for measuring compost stability. Supposing that the proposed procedure is considered a dynamic method (no limitations on the amount of oxygen supply), the final RI(24) obtained was compared with the dynamic respiration index (DRI) proposed by the EU (1000 mg O(2) kg VS(-1) h(-1)). Our result indicated that stable compost was obtained after 90 d. However, if a static limit was considered (AT(4) lower than 10 mg O(2) gTS(-1) as proposed by the EU), our result would indicate that more residence composting time would be needed. Taking into account these results, the advantages and disadvantages and the validity of the proposed method are discussed. PMID:21074929

Sánchez Arias, V; Fernández, F J; Rodríguez, L; Villaseñor, J

2010-11-12

145

Stability-Indicating HPLC Method for Posaconazole Bulk Assay  

PubMed Central

A stability-indicating liquid chromatographic (LC) method was developed for the determination of posaconazole in bulk. Chromatographic separation was achieved using an isocratic elution in a reversed-phase system, with a mobile phase composed of methanol-water (75:25, v/v), at 1.0 mL min?1 flow. Samples were exposed to degradation under thermal, oxidative and acid/basic conditions, and no interference in the analysis was observed. System suitability was evaluated and results were satisfactory (N = 4,900.00 tailing factor 1.04; RSD between injections = 0.65). The retention time of posaconazole was about 8.5 min and the method was validated within the concentration range 5–60 ?g mL?1 (r = 0.9996). Adequate results were obtained for repeatability (RSD % = 0.86–1.22), inter-day precision (RSD % = 1.21) and accuracy (98.13% mean recovery). Robustness was also determined to be satisfactory after evaluation. The proposed method was successfully applied to posaconazole bulk quantification, showing the method is useful for determination of the drug in routine analysis.

Garcia, Cassia V.; Costa, Gislaine R.; Mendez, Andreas S. L.

2012-01-01

146

Performance Evaluation of Voltage Stability Indices for Dynamic Voltage Collapse Prediction  

Microsoft Academic Search

The research presents a study in evaluating the performance of several voltage stability indices used for dynamic voltage collapse prediction in power systems. A new voltage stability index has been proposed and it is named as the power transfer stability index. The proposed index is then compared with other known voltage stability indices such as the voltage collapse prediction index,

Muhammad Nizam; Azah Mohamed; Aini Hussain

2006-01-01

147

Indicators of dynamic stability in transtibial prosthesis users.  

PubMed

An improved understanding of factors related to dynamic stability in lower-limb prosthesis users is important, given the high occurrence of falls in this population. Current methods of assessing stability are unable to adequately characterize dynamic stability over a variety of walking conditions. F-Scan Mobile has been used to collect plantar pressure data and six extracted parameters were useful measures of dynamic stability. The aim of this study was to investigate dynamic stability in individuals with unilateral transtibial amputation based on these six parameters. Twenty community ambulators with a unilateral transtibial amputation walked over level ground, uneven ground, stairs, and a ramp while plantar pressure data were collected. For each limb (intact and prosthetic) and condition, six stability parameters related to plantar center-of-pressure perturbations and gait temporal parameters, were computed from the plantar pressure data. Parameter values were compared between limbs, walking condition, and groups (unilateral transtibial prosthesis users and able-bodied subjects). Differences in parameters were found between limbs and conditions, and between prosthesis users and able-bodied individuals. Further research could investigate optimizing parameter calculations for unilateral transtibial prosthesis users and define relationships between potential for falls and the dynamic stability measures. PMID:20138523

Kendell, C; Lemaire, E D; Dudek, N L; Kofman, J

2010-03-01

148

Estimating of loadability margin of a power system by comparing Voltage Stability Indices  

Microsoft Academic Search

Estimating the margin in the loadability of the power system is essential in the real time voltage stability assessment. Voltage stability is currently one of the most important research areas in the field of electrical power system. The condition of voltage stability in a power system can be known using voltage stability indices (VSI). The loading margin is one of

M. V. Suganyadevia; C. K. Babulal

2009-01-01

149

Voltage stability and controllability indices for multimachine power systems  

Microsoft Academic Search

This paper presents a voltage stability index (VSI) and a voltage controllability index (VCI), related to the eigenvalues of m x m matrices in a multimachine power system made up of m synchronous generators and a number of infinite buses. System loads can have an arbitrary voltage sensitivity described by generalized voltage exponents. These nonlinear loads are linearized around an

C. D. Vournas

1995-01-01

150

Accuracy Analysis of Static Voltage Stability Indices Based On Power Flow Model  

Microsoft Academic Search

There are some voltage stability indices for voltage security assessment and calculating stable margin from operating point to voltage instability at each load bus. Most of those indices are based on static analyses using power flow model. This paper aims to verifying the accuracy of representative power flow model based indices by small signal stability analysis and dynamic time domain

Huadong Sun; Xiaoxin Zhou; Ruomei Li

2005-01-01

151

A comparative study of voltage stability indices in a power system  

Microsoft Academic Search

The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor

A. K. Sinha; D. Hazarika

2000-01-01

152

STABILITY-INDICATING HPLC METHOD FOR THE DETERMINATION OF THE STABILITY OF EXTEMPORANEOUSLY PREPARED NOREPINEPHRINE PARENTERAL SOLUTIONS  

Microsoft Academic Search

A stability-indicating HPLC method was developed for analysis of norepinephrine in the presence of the degradation products. The stability ofextemporaneously compoundednorepinephrinesyringes was investigated using this method. The sterile preparations of norepinephrinewere compounded to the strength of 8 µg\\/mL in accordance with USP (United States Pharmacopeia) <797> standards. To carry out the stability testing of these products, these syringes were stored under

Gagan Kaushal; Brian E. Sayre; Terrence Prettyman

2012-01-01

153

Environmental stability of PAH source indices in pyrogenic tars  

SciTech Connect

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants found in soil, sediments, and airborne particulates. The majority of PAHs found in modern soils and sediments arise from myriad anthropogenic petrogenic and pyrogenic sources. Tars and tar products such as creosote produced from the industrial pyrolysis of coal or oil at former manufactured gas plants (MGPs) or in coking retorts are viscous, oily substances that contain significant concentrations of PAH, usually in excess of 30% w/w. Pyrogenic tars and tar products have unique PAH patterns (source signatures) that are a function of their industrial production. Among pyrogenic materials, certain diagnostic ratios of environmentally recalcitrant 4-, 5- and 6-ring PAHs have been identified as useful environmental markers for tracking the signature of tars and petroleum in the environment. The use of selected PAH source ratios is based on the concept that PAHs with similar properties (i.e., molecular weight, partial pressure, solubility, partition coefficients, and biotic/abiotic degradation) will weather at similar rates in the environment thereby yielding stable ratios. The stability of more than 30 high molecular weight PAH ratios is evaluated during controlled studies of tar evaporation and aerobic biodegradation. The starting materials in these experiments consisted of relatively unweathered tars derived from coal and petroleum, respectively. The PAH ratios from these laboratory studies are compared to those measured in PAH residues found in tar-contaminated soils at a former MGP that operated with a carburetted water gas process.

Uhler, A.D.; Emsbo-Mattingly, S.D. [New Fields Environmental Forensics Practice, Rockland, MA (United States)

2006-04-15

154

Evaluation of oxygen utilization as an indicator of municipal solid-waste compost stability  

SciTech Connect

This research evaluated oxygen utilization parameters as indicators of MSW compost stability. Parameters evaluated were the oxygen utilization rate (OUR), specific oxygen uptake rate (SOUR), five-day biochemical oxygen demand, and chemical oxygen demand. In addition, other suggested indicators of stability were investigated including percent volatile solids, volatile solids reduction, nitrogen content, carbon: nitrogen ratio, and reheating potential (RP). OUR is a measure of the rate of oxygen utilization by the microorganisms in the decomposition of organic matter in compost. OUR was observed to be sensitive to the degree of stabilization and decreased with increasing compost age and stability. OUR values near zero indicate that the compost microorganisms are in a state of endogenous respiration, which is characteristic of a stable compost. Therefore, OUR is an excellent indicator of stability. A number of disadvantages are associated with OUR for practical application. Therefore, other parameters were evaluated as indicators of stability based on their statistical correlation to OUR. RP exhibited the strongest correlation to OUR. In combination, RP and SOUR were the two parameters which exhibited the strongest correlation to OUR. OUR, RP, and SOUR are all measures of microbial activity which reflect the degree of organic decomposition, and therefore, stability. Based on the results of this research; OUR, RP, and SOUR are useful parameters in assessing compost stability.

Zimmerman, R.A.

1991-01-01

155

A Comparison of Voltage Stability Indices for Placing Shunt FACTS Controllers  

Microsoft Academic Search

Location of shunt compensation devices is important for the enhancement of the voltage stability for practical power systems. This paper presents a comparison of several voltage stability indices in electric power system to identify the weakest bus\\/ area of the system. Shunt FACTS controller is introduced at the weakest bus in IEEE 14-bus test system and its effectiveness is assessed

A. R. Phadke; S. K. Bansal; K. R. Niazi

2008-01-01

156

Improved branch-based voltage stability proximity indices. II. Application in security analysis  

Microsoft Academic Search

In this paper, a method for contingency ranking for voltage stability is proposed. Contingencies are ranked according to a performance index defined in terms of branch-based voltage stability proximity indices. Simulation results show that the most critical contingencies can be correctly identified.

Adriana S. Quintela; Carlos A. Castro

2002-01-01

157

Static respiration indices to investigate compost stability: effect of sample weight and temperature and comparison with dynamic respiration indices.  

PubMed

Goal of this work was to study the effect of sample weight and temperature on the microbial respiration indices of a static microbial respiration test used to quantify compost stability. The static respiration tests (SRT) were performed at two different temperatures (20°C and 35°C) using five different sample weights (19, 38, 56, 75 and 94 dry g). Results showed that at 35°C, as sample weight increased, the magnitude of the respiration indices reduced. In addition, the 35°C temperature resulted in higher static respiration activity indices compared to that at the 20°C for two sample weights. The static respiration tests led to 2-2.5 times lower oxygen-related indices compared to those calculated in dynamic respiration tests (DRT); the 7-day CO(2) cumulative generations were, however, almost similar for both types of tests. Respiratory quotients (RQs) were constantly between 0.8 to 1.2 during the SRT. PMID:22850170

Komilis, Dimitrios; Kletsas, Constantinos

2012-07-05

158

Improved branch-based voltage stability proximity indices. Part I: Theoretical background  

Microsoft Academic Search

In this paper improved branch-based voltage stability proximity indices are proposed. Their computation does not require the use of equivalents nor matrix handling, being straightforward and fast. They can be a very useful tool for power systems operators and planners both to evaluate systems operating conditions, and to determine system reinforcement actions. Also, the indices can be used to compare

Adriana S. Quintela; Carlos A. Castro

2002-01-01

159

Decision fusion of voltage stability indicators for small sized power systems  

Microsoft Academic Search

In this paper, the authors consider a probabilistic approach to at the issue of voltage stability of a small power system. They do this via a data fusion technique using the Bayesian rule, which is well suited for such applications. They use three proximity indicators in this study. On their own, each of these indicators have some amount of probability

Derek Sam; Chika Nwankpa; Dagmar Niebur

2001-01-01

160

Two Approaches to Examining the Stability of Myers-Briggs Type Indicator Scores  

ERIC Educational Resources Information Center

|In this study, two approaches are used to assess the stability of Myers-Briggs Type Indicator scores across 3 administrations (N = 231): longitudinal configural frequency analysis with categorical scores and generalizability theory with the Preference Clarity Indices and continuous scores. The results are generally positive. Evaluation of…

Salter, Daniel W.; Forney, Deanna S.; Evans, Nancy J.

2005-01-01

161

Measuring geomorphic stability and mobility; Interferomteric coherence data as an indicator for aeolian (wind-blown) dune stability  

NASA Astrophysics Data System (ADS)

Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuring geomorphological dynamics can involve field work, i.e., ground truth. Dunes, wind streaks and other aeolian morphologies have been identified on Earth, Mars, Venus and Titan. These morphologies can be subjected to rapid and continuous changes when the surface is not stabilized by vegetation or crust and the wind is sufficiently strong. Thus, these sand bodies can change rapidly responding to the wind regime, rainfall, and sand particle availability. Identifying these changes by remote sensing (or even on the ground) is not straightforward because the entire surface may change concurrently. In this paper we demonstrate how synthetic aperture radar interferometry (InSAR) can be used to identify changes in dunes using the coherence which is normally a measure of phase noise prohibiting interferometric studies. We demonstrate this for dunes along the Negev and Sinai border region. This paper will show how ERS data were used to map the stability, and loss of it, over time ranges spanning from 1 day intervals to 2 years when eventually the entire surface changed including the, so called, stable areas. This methodology has advantages as it does not show potential mobility but rather the true mobility or stability. This methodology is applicable to planetary landscapes where there is no other indication of stability. Moreover, the methodology can be used also to measure the stability of surfaces susceptible to other mechanisms of landscape changes.

Blumberg, D. G.; August, Y.; Rotman, S. R.

2012-04-01

162

The effects of gait strategy on metabolic rate and indicators of stability during downhill walking.  

PubMed

When walking at a given speed, humans often appear to prefer gait patterns that minimize metabolic rate, thereby maximizing metabolic economy. However, recent experiments have demonstrated that humans do not maximize economy when walking downhill. The purpose of this study was to investigate whether this non-metabolically optimal behavior is the result of a trade-off between metabolic economy and gait stability. We hypothesized that humans have the ability to modulate their gait strategy to increase either metabolic economy or stability, but that increase in one measure will be accompanied by decrease in the other. Subjects walked downhill using gait strategies ranging from risky to conservative, which were either prescribed by verbal instructions or induced by the threat of perturbations. We quantified spatiotemporal gait characteristics, metabolic rate and several indicators of stability previously associated with fall risk: stride period variability; step width variability; Lyapunov exponents; Floquet multipliers; and stride period fractal index. When subjects walked using conservative gait strategies, stride periods and lengths decreased, metabolic rate increased, and anteroposterior maximum Lyapunov exponents increased, which has previously been interpreted as an indicator of decreased stability. These results do not provide clear support for the proposed trade-off between economy and stability, particularly when stability is approximated using complex metrics. However, several gait pattern changes previously linked to increased fall risk were observed when our healthy subjects walked with a conservative strategy, suggesting that these changes may be a response to, rather than a cause of, increased fall risk. PMID:22677338

Monsch, E D; Franz, C O; Dean, J C

2012-06-05

163

RP-HPLC determination of midecamycin and related impurities  

Microsoft Academic Search

Summary  A method has been developed for separation and quantitation of midecamycin A1 and related impurities by high-performance liquid chromatography with evaporative light-scattering detection (ELSD). Chromatographic\\u000a conditions included use of a Diamonsil C18 column; the mobile phase was 52:48 acetonitrile ?0.2 mol L?1 ammonium formate solution (adjusted to pH 7.3 with triethylamine) at a flow rate of 1 mL min?1. The

Liu Ying; Hu Chang-qin

2003-01-01

164

Separation of kafirins on surface porous RP-HPLC columns  

Technology Transfer Automated Retrieval System (TEKTRAN)

Surface porous HPLC columns were investigated for the separation of kafarins, storage proteins of grain sorghum. Kafirins were successfully separated using C3, C8 and C18 surface porous stationary phases in less than 17 min. Separations using a monolithic C18 stationary phase were also developed ...

165

[Determination of bendazac lysine by RP-HPLC].  

PubMed

Bendazac (BD) was separated on a CLC-ODS column, 150 x 6 mm id (Shimadzu), using methanol acetic acid 0.1 mol/L (67:33) as the mobile phase. The flow rate was 1.0 ml/min and the detection wavelength, 254 nm. The detection limit of BD was 0.1 ng (R/N, 3:1), which was determined by the peak area measurement using an external standard method. The calibration curve was linear in the range of 5-10 micrograms (r = 0. 9998). The average recovery of BDL was 99.46 +/- 0.59% (n = 9). This method has been applied satisfactorily to the determination of BDL samples. PMID:1452158

Wu, C; Chao, R; Ma, P; Gao, X

1992-06-01

166

[Determination of quercetin in changyanning tablets by RP-HPLC].  

PubMed

The quercetin in Changyannning Tablets was determined by reverse phase HPLC on Shim-Pack CLC-ODS column(150 mm x 4.6 mm) with UV detector and methanol-water-phosphoric acid(55:44.6:0.4) as mobile phase (1.0 ml/min). The average recovery relative standard deviation were 99.7% and 1.01% respectively. PMID:11601313

Hu, Y; Wang, C; Qian, J

1998-05-01

167

RP-HPLC ANALYSES OF GLIADINS IN MACEDONIAN WHEAT VARIETIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

HPLC is an analytical method that is widely used for identification of wheat and other cereal varieties. It is also used for determination and prediction of quality, for studies of interactions and processing of cereal proteins, and as a preparative method for cereal proteins and for their characte...

168

Stability indicating HPTLC method for the simultaneous determination of pseudoephedrine and cetirizine in pharmaceutical formulations  

Microsoft Academic Search

The combination of pseudoephedrine and cetirizine is widely used in the treatment of allergic rhinitis. A rapid, selective and stability indicating high performance thin layer chromatographic method was developed and validated for their simultaneous estimation in pharmaceutical dosage forms. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of ethyl

Sapna N Makhija; Pradeep R Vavia

2001-01-01

169

Microscopic indicator for thermodynamic stability of hydrogen storage materials provided by positive muon-spin rotation  

NASA Astrophysics Data System (ADS)

In search of a high-capacity hydrogen storage system, we have investigated the thermodynamic properties of borohydrides [M(BH4)2] . Using positive muon-spin rotation and relaxation (?+SR) , we have acquired data for five different powder samples below ambient temperature. Zero-field ?+SR measurements indicate the formation of the H-?+-H system in LiBH4 , NaBH4 , KBH4 , and Ca(BH4)2 but not in Mg(BH4)2 . It is also found that the amplitude of the H?H signal (AH?H) varies with the electronegativity (?P) of Mn+ . Since the thermodynamic stability of M(BH4)n also depends on ?P , AH?H is thought to be a microscopic indicator for the stability of M(BH4)n .

Sugiyama, Jun; Ikedo, Yutaka; Noritake, Tatsuo; Ofer, Oren; Goko, Tatsuo; Månsson, Martin; Miwa, Kazutoshi; Ansaldo, Eduardo J.; Brewer, Jess H.; Chow, Kim H.; Towata, Shin-Ichi

2010-03-01

170

A MARKER-BASED STABILITY INDICATING HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHIC METHOD FOR VITEX TRIFOLIA  

Microsoft Academic Search

Casticin, chrysoplenol-D, p-hydroxy benzoic acid, and p-methoxy benzoic acid are representative flavonoids and benzoic acid derivatives in Vitex trifolia, a well-known traditional Chinese, as well as ayurvedic medicine, with a wide range of biological activities. In the present paper, the aforementioned four markers were isolated and simultaneously quantified by TLC densitometric method. In the present study, a novel stability-indicating high-performance

N. Tiwari; D. Yadav; S. C. Singh; M. M. Gupta

2011-01-01

171

Stability indicating HPTLC determination of Trimetazidine as bulk drug and in pharmaceutical formulations  

Microsoft Academic Search

A simple, selective, precise and stability-indicating high-performance thin-layer chromatographic method of analysis of trimetazidine hydrochloride both as a bulk drug and in formulations is reported. The mobile phase composition was n-butanol-water-methanol-ammonia (20%) (14:0.2:0.2:2, v\\/v\\/v\\/v). Densitometric analysis of trimetazidine hydrochloride was carried out in the absorbance mode at 254 nm. the calibration curve of trimetazidine hydrochloride in methanol was linear in

Simmy O Thoppil; Rita M Cardoza; P. D Amin

2001-01-01

172

Stability indicating HPTLC determination of clopidogrel bisulphate as bulk drug and in pharmaceutical dosage form  

Microsoft Academic Search

A sensitive, selective, precise and stability indicating high-performance thin layer chromatographic method of analysis of clopidogrel bisulphate both as a bulk drug and in formulations was developed and validated in pharmaceutical dosage form. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of carbon tetrachloride–chloroform–acetone (6:4:0.15, v\\/v\\/v). This system was

Himani Agrawal; Neeraj Kaul; A. R Paradkar; K. R Mahadik

2003-01-01

173

Stability-indicating HPTLC determination of curcumin in bulk drug and pharmaceutical formulations  

Microsoft Academic Search

A simple, selective, precise and stability-indicating high-performance thin-layer chromatographic method of analysis of curcumin both as a bulk drug and in formulations was developed and validated. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of chloroform:methanol (9.25:0.75v\\/v). This system was found to give compact spots for curcumin (Rf value

M. J. Ansari; S. Ahmad; K. Kohli; J. Ali; R. K. Khar

2005-01-01

174

A Stability-Indicating Simultaneous Analysis of Acetaminophen and Hydrocodone Bitartrate in Tablets Formulation by HPLC  

Microsoft Academic Search

A rapid, simple, stability indicating, reversed phase high-performance liquid chromotographic (HPLC) method is presented here for direct and simultaneous quantitation of Acetaminophen and Hydrocodone Bitartrate in tablets dosage form at a ratio of 100:1. This procedure not only separated the two active components but also separated known impurity and degradation product of acetaminophen, p-aminophenol and p-chloroacetanilide. The method described here

Shabbir U. Alvi; Frank Castro

1987-01-01

175

Stability-indicating methods for the determination of doxazosin mezylate and celecoxib  

Microsoft Academic Search

Two stability-indicating methods were developed for the determination of doxazosin mesylate (I) and celecoxib (II) in the presence of their degradation products. The first method depends on the use of first derivative spectrophotometry (D1) at 256, 269 nm for (I) and (II), respectively. This method determines (I) and (II) in concentration ranges of 0.8–12 and 1–20 ?g ml?1 with mean

L. I Bebawy; A. A Moustafa; N. F Abo-Talib

2002-01-01

176

Structure and stability changes of human IgG1 Fc as a consequence of methionine oxidation.  

PubMed

The Fc region has two highly conserved methionine residues, Met 33 (C(H)3 domain) and Met 209 (C(H)3 domain), which are important for the Fc's structure and biological function. To understand the effect of methionine oxidation on the structure and stability of the human IgG1 Fc expressed in Escherichia coli, we have characterized the fully oxidized Fc using biophysical (DSC, CD, and NMR) and bioanalytical (SEC and RP-HPLC-MS) methods. Methionine oxidation resulted in a detectable secondary and tertiary structural alteration measured by circular dichroism. This is further supported by the NMR data. The HSQC spectral changes indicate the structures of both C(H)2 and C(H)3 domains are affected by methionine oxidation. The melting temperature (Tm) of the C(H)2 domain of the human IgG1 Fc was significantly reduced upon methionine oxidation, while the melting temperature of the C(H)3 domain was only affected slightly. The change in the C(H)2 domain T m depended on the extent of oxidation of both Met 33 and Met 209. This was confirmed by DSC analysis of methionine-oxidized samples of two site specific methionine mutants. When incubated at 45 degrees C, the oxidized Fc exhibited an increased aggregation rate. In addition, the oxidized Fc displayed an increased deamidation (at pH 7.4) rate at the Asn 67 and Asn 96 sites, both located on the C(H)2 domain, while the deamidation rates of the other residues were not affected. The methionine oxidation resulted in changes in the structure and stability of the Fc, which are primarily localized to the C(H)2 domain. These changes can impact the Fc's physical and covalent stability and potentially its biological functions; therefore, it is critical to monitor and control methionine oxidation during manufacturing and storage of protein therapeutics. PMID:18407665

Liu, Dingjiang; Ren, Da; Huang, Holly; Dankberg, Jane; Rosenfeld, Robert; Cocco, Melanie J; Li, Luke; Brems, David N; Remmele, Richard L

2008-04-12

177

Simultaneous, stability indicating, HPLC-DAD determination of guaifenesin and methyl and propyl-parabens in cough syrup  

Microsoft Academic Search

A stability indicating high performance liquid chromatography procedure has been developed for the simultaneous determination of guaifenesin (GUA), methyl p-hydroxybenzoate (MHB) and propyl p-hydroxybenzoate (PHB) in a commercial cough syrup dosage form. The method was specific and stability indicating as chromatographic conditions were selected to provide adequate separation of GUA, MHB and PHB from the putative degradation products guaiacol (GUAI)

Giorgio Grosa; Erika Del Grosso; Roberta Russo; Gianna Allegrone

2006-01-01

178

Identification of weak buses in a power network using novel voltage stability indicator in radial distribution system  

Microsoft Academic Search

A unique and novel voltage stability indicator derived from voltage equation of radial distribution system has been proposed in this paper. The voltage stability indicator (VSI) can identify the condition of load buses in the voltage collapse point of view. The developed VSI has been tested on a standard 32-bus radial distribution system for reliability test. A comparative study between

Sayonsom Chanda; Bappa Das

2011-01-01

179

Simultaneous Determination of Losartan Potassium, Atenolol and Hydrochlorothiazide in Pharmaceutical Preparations by Stability-Indicating UPLC  

Microsoft Academic Search

A stability-indicating UPLC method was developed for the simultaneous quantitative determination of losartan potassium, atenolol,\\u000a and hydrochlorothiazide in pharmaceutical dosage forms in the presence of degradation products. The separation was achieved\\u000a on a simple isocratic method (water: acetonitrile: triethyl amine: ortho phosphoric acid (60:40:0.1:0.1, v\\/v) at 0.7 mL min?1, a detection wavelength of 225 nm). The retention times of losartan potassium, atenolol, and

D. Durga Rao; N. V. Satyanarayana; S. S. Sait; Y. Ramakoti Reddy; K. Mukkanti

2009-01-01

180

Gas Generation Rates as an Indicator for the Long Term Stability of Radioactive Waste Products  

SciTech Connect

Pursuant to the 'Act on the Peaceful Utilization of Atomic Energy and the Protection against its Hazards' (Atomic Energy Act) the Federal Office for Radiation Protection (Bundesamt fuer Strahlenschutz, BfS) is legally responsible for the construction and operation of federal facilities for the disposal of radioactive waste. Within the scope of this responsibility, particular due to par. 74(1) Ordinance on Radiation Protection, BfS defines all safety-related requirements on waste packages envisaged for disposal, establishes guidelines for the conditioning of radioactive waste and approves the fulfillment of the waste acceptance requirements within the radioactive waste quality control system. BfS also provides criteria to enable the assessment of methods for the treatment and packaging of radioactive waste to produce waste packages suitable for disposal according to par. 74(2) Ordinance on Radiation Protection. Due to the present non-availability of a repository in Germany, quality control measures for all types of radioactive waste products are carried out prior to interim storage with respect to the future disposal. As a result BfS approves the demonstrated properties of the radioactive waste packages and confirms the fulfillment of the respective requirements. After several years of storage the properties of waste packages might have changed. By proving, that such changes have no significant impact on the quality of the waste product, the effort of requalification could be minimized. Therefore, data on the long-term behavior of radioactive waste products need to be acquired and indicators to prove the long-term stability have to be quantified. Preferably, such indicators can be determined easily with non-destructive methods, even for legacy waste packages. A promising parameter is the gas generation rate. The relationship between gas generation rate and long term stability is presented as first result of an ongoing study on behalf of BfS. Permissible gas generation rates that ensure adequate product stability with respect to future disposal are to be identified. (authors)

Steyer, S.; Brennecke, P. [Bundesamt fur Strahlenschutz, Federal Office for Radiation Protection, Salzgitter (Germany); Bandt, G.; Kroger, H. [TUV NORD EnSys Hannover GmbH and Co. KG, Hannover (Germany)

2007-07-01

181

Microscopic indicator for thermodynamic stability of hydrogen storage materials provided by muon-spin spectroscopy  

NASA Astrophysics Data System (ADS)

In search of a high-capacity hydrogen storage system, we have investigated the thermodynamic properties of borohydrides [M(BH4)n]. Using positive muon-spin rotation and relaxation (?+SR), we have acquired experimental data for a wide range of different powder samples below ambient temperature. Zero-field ?+SR measurements indicate the formation of the H-?+-H system in LiBH4, NaBH4, KBH4 and Ca(BH4)2, but not in Mg(BH4)2. It is also found that the amplitude of the H?H signal (AH?H) varies with the electronegativity (?P) of Mn+. This is because, when ?P of Mn+ is small, [BH4]- should be more negative, resulting in an increase in the electron-density of H- ions. Therefore, AH?H increases with decreasing ?P. Since the thermodynamic stability of M(BH4)n also depends on ?P, AH?H is thought to be a microscopic indicator for the stability of borohydrides.

Sugiyama, Jun; Ikedo, Yutaka; Noritake, Tatsuo; Miwa, Kazutoshi; Towata, Shinichi; Goko, Tatsuo; Ofer, Oren; Månsson, Martin; Ansaldo, Eduardo J.; Brewer, Jess H.; Chow, Kim H.

2010-04-01

182

Stress degradation studies and stability-indicating TLC-densitometric method of glycyrrhetic acid  

PubMed Central

Background Glycyrrhetic acid, a pentacyclic triterpenoid, possesses a broad range of pharmacological activities and serves as template to synthesize many bioactive drugs. This paper describes a simple, accurate, and sensitive stability-indicating TLC densitometric method for the determination of glycyrrhetic acid and its degradation product as per the ICH guidelines. Results Separation was carried out on TLC aluminium sheet pre-coated with silica gel 60F254 using chloroform, methanol and formic acid (9:0.9:0.1, v/v). Compact spot for glycyrrhetic acid was found at Rf value of 0.42 ± 0.03. Densitometric analysis was carried out in the absorbance mode at ?max 254 nm. Glycyrrhetic acid was found to be stable to the exposure of base, neutral, oxidation, dry heating treatment and wet heating treatment, but showed degradation under acidic and photochemical conditions. Moreover, fragmentation pattern of glycyrrhetic acid was developed by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. A photo-degraded product was characterized through comparison of mass spectrometric studies with glycyrrhetic acid. Conclusion The developed stability-indicating TLC-densitometric method can be applied for routine analysis of glycyrrhetic acid in the presence of its degradation products.

2013-01-01

183

Stability Indicating HPLC Determination of Risperidone in Bulk Drug and Pharmaceutical Formulations  

PubMed Central

The objective of the current study was to develop a validated stability-indicating assay method (SIAM) for risperidone after subjecting it to forced decomposition under hydrolysis, oxidation, photolysis, and thermal stress conditions. The liquid chromatographic separation was achieved isocratically on a symmetry C18 column (5??m size, 250?mm × 4.6?mm i.d.) using a mobile phase containing methanol: acetonitrile (80?:?20, v/v) at a flow rate of 1?mL/min and UV detection at 280?nm. Retention time of risperidone was found to be 3.35 ± 0.01. The method was linear over the concentration range of 10–60??g/mL(r2 = 0.998) with a limit of detection and quantitation of 1.79 and 5.44??g/mL, respectively. The method has the requisite accuracy, specificity, sensitivity, and precision to assay risperidone in bulk form and pharmaceutical dosage forms. Degradation products resulting from the stress studies did not interfere with the detection of Risperidone, and the assay is thus stability indicating.

Dedania, Zarna R.; Dedania, Ronak R.; Sheth, Navin R.; Patel, Jigar B.; Patel, Bhavna

2011-01-01

184

Stability-Indicating HPLC-DAD Determination of Ribavirin in Capsules and Plasma.  

PubMed

A simple, selective and stability-indicating high-pressure liquid chromatographic method was developed for the analysis of ribavirin. Chromatographic separation was achieved by using a CPS Hypersil cyano column (4.6 × 250 mm, 5 µm particle size) with isocratic elution of the mobile phase, which was composed of 50 mM phosphate buffer, adjusted at pH 4 with phosphoric acid. The mobile phase was pumped at a flow rate of 0.8 mL/min. The detector was set at 240 nm and quantification of the analyte was based on peak area measurement. The method was validated with respect to linearity, range, precision, accuracy, selectivity, robustness, limit of detection and limit of quantitation. The calibration curve was linear in the range of 5-200 µg/mL with correlation coefficient > 0.999. Ribavirin was subjected to forced degradation studies under two conditions: mild and extensive stress testing. These studies included the effects of hydrolysis (neutral, acidic and alkaline) and oxidation, photolysis and dry heat). The proposed method was proved to be stability-indicating by the resolution of the drug from its forced degradation products, making use of the diode array detector as a tool for confirmation of peak identity and purity. Moreover, the kinetics of alkaline degradation of ribavirin were investigated, an Arrhenius plot was constructed and the activation energy was calculated. The developed method was also extended to analyze ribavirin in capsules and in human plasma with good recovery values. PMID:23749878

Haggag, Rim Said; Belal, Said Fathalla; Hewala, Ismail Ibrahim; El Rouby, Ola Ahmed

2013-06-01

185

Postural stability of biped robots and the foot-rotation indicator (FRI) point  

SciTech Connect

The focus of this paper is the problem of foot rotation in biped robots during the single-support phase. Foot rotation is an indication of postural instability, which should be carefully treated in a dynamically stable walk and avoided altogether in a statically stable walk. The author introduces the foot-rotation indicator (FRI) point, which is a point on the foot/ground-contact surface where the net ground-reaction force would have to act to keep the foot stationary. To ensure no foot rotation, the FRI point must remain within the convex hull of the foot-support area. In contrast with the ground projection of the center of mass (GCoM), which is a static criterion, the FRI point incorporates robot dynamics. As opposed to the center of pressure (CoP) -- better known as the zero-moment point (ZMP) in the robotics literature -- which may not leave the support area, the FRI point may leave the area. In fact, the position of the FRI point outside the footprint indicates the direction of the impending rotation and the magnitude of rotational moment acting on the foot. Owing to these important properties, the FRI point helps not only to monitor the state of postural stability of a biped robot during the entire gait cycle, but indicates the severity of instability of the gait as well. In response to a recent need, the paper also resolves the misconceptions surrounding the CoP/ZMP equivalence.

Goswami, A. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Computer and Information Science

1999-06-01

186

Stability of the Photon Indices in Z-source GX 340+0 for Spectral States  

NASA Astrophysics Data System (ADS)

We show an analysis of the spectral and timing properties of X-ray radiation from Z-source GX 340+0 during its evolution when the electron temperature of the transition layer (TL) kTe monotonically decreases from 21 to 3 keV. We analyze episodes observed with BeppoSAX and RXTE. We reveal that the X-ray broadband energy spectra during all spectral states can be reproduced by a physical model composed of a soft Blackbody component and two Comptonized components (both due to the presence of the TL that upscatters both seed photons of T s1 <~ 1 keV coming from the disk (first component Comptb1), and seed photons of temperature T s2 <~ 1.5 keV coming from the neutron star (second component Comptb2) and the iron-line (Gaussian) component. Spectral analysis using this model indicates that the photon power-law indices ?com1 and ?com2 of the Comptonized components are almost constant, ?com1 and ?com2 ~ 2 when kTe changes from 3 to 21 keV along the Z-track. We interpret the detected quasi-stability of the indices of Comptonized components to be near a value of 2. Furthermore, this index stability now found for the Comptonized spectral components of Z-source GX 340+0 is similar to that previously established in the atoll sources 4U 1728-34 and GX 3+1, and earlier proposed for a number of X-ray neutron stars (NSs). This behavior of NSs both for atoll and Z-sources is essentially different from that observed in black hole binaries where ?com increases during a spectral evolution from the low state to the high state and ultimately saturates at a high mass accretion rate.

Seifina, Elena; Titarchuk, Lev; Frontera, Filippo

2013-03-01

187

Spectrophotometric and stability-indicating high-performance liquid chromatographic determinations of terbutaline sulfate.  

PubMed

Spectrophotometric and stability-indicating HPLC procedures are described for determination of terbutaline sulfate in bulk powder and dosage form. The first procedure is based on diazo coupling of the phenolic groups of terbutaline sulfate with fast red B salt in the presence of sodium hydroxide. The colored compound developed in alkaline medium was measured at 475 nm. Different variables affecting the reaction were studied. Beer's Law is obeyed in the concentration range of 1-6 microg/mL. In the HPLC procedure, the separation was carried out on a Caltrex AIII column, a relatively new packing material consisting of silica-bonded calix[8]arene, using an isocratic binary mobile phase, acetonitrile-ammonium acetate (50 + 50, v/v), at pH 6.2. A diode array detector was used at 280 nm. The method was validated for system suitability, linearity, precision, LOD, LOQ, specificity, stability, and robustness. The LOD and LOQ were 0.196 and 0.781 microg/mL, respectively. The recovery values of this method were between 98 and 102%, and the reproducibility was within 0.92%. Statistical comparison of the results obtained from the analysis of the studied drug to those of the official British Pharmacopoeia (2007) method using t- and F-tests showed no significant difference between them. PMID:23175974

Hashem, Hisham A; Elmasry, Manal S; Hassan, Wafaa E; Tründelberg, Clemens; Jira, Thomas

188

A validated HPLC stability-indicating method for the determination of diacerhein in bulk drug substance.  

PubMed

A novel stability-indicating high-performance liquid chromatographic (HPLC) method was developed and validated for the assay of diacerhein in bulk forms. Diacerhein was found to degrade in alkaline and acidic conditions and also under oxidative stress. The drug was stable to dry heat and in presence of light. Resolution of drug, its potential impurities and degradation products were achieved on a RP18 (endcapped) column utilizing 0.1 M phosphoric acid and methanol (40:60, v/v) as eluent at the detection wavelength of 254 nm. The validation studies were carried out fulfilling International Conference on Harmonisation (ICH) requirements. The procedure was found to be specific, linear, precise (including intermediate precision), accurate and robust. PMID:15955656

Giannellini, Valerio; Salvatore, Francesco; Bartolucci, Gianluca; Coran, Silvia A; Bambagiotti-Alberti, Massimo

2005-09-15

189

Stability indicating HPLC method for the simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations  

PubMed Central

Background A simple, specific, and fast stability indicating reverse phase liquid chromatographic method was established for instantaneous determination of moxifloxacin and prednisolone in bulk drugs and pharmaceutical formulations. Results Optimum chromatographic separations among the moxifloxacin, prednisolone and stress-induced degradation products were achieved within 10 minutes by use of BDS Hypersil C8 column (250 X 4.6 mm, 5 ?m) as stationary phase with mobile phase consisted of a mixture of phosphate buffer (18 mM) containing 0.1% (v/v) triethylamine, at pH 2.8 (adjusted with dilute phosphoric acid) and methanol (38:62 v/v) at a flow rate of 1.5 mL min-1. Detection was performed at 254 nm using diode array detector. The method was validated in accordance with ICH guidelines. Response was a linear function of concentrations over the range of 20–80 ?g mL-1 for moxifloxacin (r2 ? 0.998) and 40–160 ?g mL-1 for prednisolone (r2 ? 0.998). The method was resulted in good separation of both the analytes and degradation products with acceptable tailing and resolution. The peak purity index for both the analytes after all types of stress conditions was ? 0.9999 indicated a complete separation of both the analyte peaks from degradation products. The method can therefore, be regarded as stabilityindicating. Conclusions The developed method can be applied successfully for simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations and their stability studies.

2012-01-01

190

Bioremediation of Contaminated Lake Sediments and Evaluation of Maturity Indicies as Indicators of Compost Stability  

PubMed Central

Land contamination is one of the widely addressed problems, which is gaining importance in many developed and developing countries. International efforts are actively envisaged to remediate contaminated sites as a response to adverse health effects. Popular conventional methodologies only transfer the phase of the contaminant involving cost intensive liabilities besides handling risk of the hazardous waste. Physico-chemical methods are effective for specific wastes, but are technically complex and lack public acceptance for land remediation. “Bioremediation”, is one of the emerging low-cost technologies that offer the possibility to destroy various contaminants using natural biological activities. Resultant non -toxic end products due to the microbial activity and insitu applicability of this technology is gaining huge public acceptance. In the present study, composting is demonstrated as a bioremediation methodology for the stabilization of contaminated lake sediments of Hyderabad, A.P, India. Lake sediment contaminated with organics is collected from two stratums – upper (0.25 m) and lower (0.5m) to set up as Pile I (Upper) and Pile II (Lower) in the laboratory. Lime as a pretreatment to the lake sediments is carried out to ensure metal precipitation. The pretreated sediment is then mixed with organic and inorganic fertilizers like cow dung, poultry manure, urea and super phosphate as initial seeding amendments. Bulking agents like sawdust and other micronutrients are provided. Continuous monitoring of process control parameters like pH, moisture content, electrical conductivity, total volatile solids and various forms of nitrogen were carried out during the entire course of the study. The stability of the compost was evaluated by assessing maturity indices like C/N, Cw (water soluble carbon), CNw (Cw/Nw), nitrification index (NH4/NO?3), Cation Exchange Capacity (CEC), germination index, humification ratio, compost mineralization index (ash content/oxidizable carbon), sorption capacity index (CEC/oxidizable carbon). Enzyme activities of agricultural interest like urease, phosphatase, ?-glucosidase, dehydrogenase and BAA-hydrolyzing protease, which are involved in the nitrogen, phosphorus and carbon cycles, were also assessed. Total content of macro and micronutrients in the final compost was also determined to assess the fertilizer value. The studies revealed that composting could be applied as a remediation technology after removing the top sediment. The maturity indices that are evaluated from the present study can be used to validate the success of the remediation technology.

Rekha, P.; Suman Raj, D. S.; Aparna, C.; Bindu, V. Hima; Anjaneyulu, Y.

2005-01-01

191

Bioremediation of contaminated lake sediments and evaluation of maturity indicies as indicators of compost stability.  

PubMed

Land contamination is one of the widely addressed problems, which is gaining importance in many developed and developing countries. International efforts are actively envisaged to remediate contaminated sites as a response to adverse health effects. Popular conventional methodologies only transfer the phase of the contaminant involving cost intensive liabilities besides handling risk of the hazardous waste. Physico-chemical methods are effective for specific wastes, but are technically complex and lack public acceptance for land remediation. iBioremediatio nî, is one of the emerging low-cost technologies that offer the possibility to destroy various contaminants using natural biological activities. Resultant non-toxic end products due to the microbial activity and insitu applicability of this technology is gaining huge public acceptance. In the present study, composting is demonstrated as a bioremediation methodology for the stabilization of contaminated lake sediments of Hyderabad, A.P, India. Lake sediment contaminated with organics is collected from two stratums--upper (0.25 m) and lower (0.5m) to set up as Pile I (Upper) and Pile II (Lower) in the laboratory. Lime as a pretreatment to the lake sediments is carried out to ensure metal precipitation. The pretreated sediment is then mixed with organic and inorganic fertilizers like cow dung, poultry manure, urea and super phosphate as initial seeding amendments. Bulking agents like sawdust and other micronutrients are provided. Continuous monitoring of process control parameters like pH, moisture content, electrical conductivity, total volatile solids and various forms of nitrogen were carried out during the entire course of the study. The stability of the compost was evaluated by assessing maturity indices like C/N, Cw (water soluble carbon), CNw (Cw/Nw), nitrification index (NH4/NO-3), Cation Exchange Capacity (CEC), germination index, humification ratio, compost mineralization index (ash content/oxidizable carbon), sorption capacity index (CEC/oxidizable carbon). Enzyme activities of agricultural interest like urease, phosphatase, P-glucosidase, dehydrogenase and BAA-hydrolyzing protease, which are involved in the nitrogen, phosphorus and carbon cycles, were also assessed. Total content of macro and micronutrients in the final compost was also determined to assess the fertilizer value. The studies revealed that composting could be applied as a remediation technology after removing the top sediment. The maturity indices that are evaluated from the present study can be used to validate the success of the remediation technology. PMID:16705825

Rekha, P; Suman Raj, D S; Aparna, C; Hima Bindu, V; Anjaneyulu, Y

2005-08-01

192

Spectrofluorimetric methods of stability-indicating assay of certain drugs affecting the cardiovascular system  

NASA Astrophysics Data System (ADS)

Two stability-indicating spectrofluorimetric methods have been developed for the determination of ezetimibe and olmesartan medoxomil, drugs affecting the cardiovascular system, and validated in the presence of their degradation products. The first method, for ezetimibe, is based on an oxidative coupling reaction of ezetimibe with 3-methylbenzothiazolin-2-one hydrazone hydrochloride in the presence of cerium (IV) ammonium sulfate in an acidic medium. The quenching effect of ezetimibe on the fluorescence of excess cerous ions is measured at the emission wavelength, ?em, of 345 nm with the excitation wavelength, ?ex, of 296 nm. Factors affecting the reaction were carefully studied and optimized. The second method, for olmesartan medoxomil, is based on measuring the native fluorescence intensity of olmesartan medoxomil in methanol at ?em = 360 nm with ?ex = 286 nm. Regression plots revealed good linear relationships in the assay limits of 10-120 and 8-112 g/ml for ezetimibe and olmesartan medoxomil, respectively. The validity of the methods was assessed according to the United States Pharmacopeya guidelines. Statistical analysis of the results exposed good Student's t-test and F-ratio values. The introduced methods were successfully applied to the analysis of ezetimibe and olmesartan medoxomil in drug substances and drug products as well as in the presence of their degradation products.

Moussa, B. A.; Mohamed, M. F.; Youssef, N. F.

2011-01-01

193

Stability-indicating Method for the Estimation of Riluzole in Tablets  

PubMed Central

A stability-indicating reverse-phase high-pressure liquid chromatography method with photodiode array detector was developed and validated for estimation of riluzole in the bulk and tablet dosage forms. Riluzole was subjected to stress conditions (light, heat, humidity, acid/base hydrolysis and oxidation) and the stressed samples were analyzed by developed method. Degradation was observed in acidic, basic, oxidative and thermal conditions. The degradation products were well resolved from riluzole peak. An inertsil-ods column (250×4.6 mm, 5 ?) with a mobile phase comprising 0.02% v/v formic acid:acetonitrile(35:65 v/v) at a flow rate of 1.0 ml/min was used and eluents were monitored at 260 nm. The retention time of riluzole was 5.7 min. Complete validation for the method was carried out according to Internation Conference on Harmonization guidelines. Linearity was achieved in the range 10-50 ?g/ml with a correlation coefficient (r) 0.9998. The percent assay was 100.92 and mean percentage recovery was found to be 101.10.

Neeha, T.; Bhargavi, P.; Jyothi, A. Aruna; Devalarao, G.; Nalluri, B. N.

2013-01-01

194

Stability-indicating HPLC Method for Simultaneous Determination of Montelukast and Fexofenadine Hydrochloride  

PubMed Central

A simple, specific, accurate, and stability-indicating reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of montelukast and fexofenadine hydrochloride, using a Lichrospher® 100, RP-18e column and a mobile phase composed of methanol:0.1% o-phosphoric acid (90:10 v/v), pH 6.8. The retention times of montelukast and fexofenadine hydrochloride were found to be 10.16 and 12.03 min, respectively. Linearity was established for montelukast and fexofenadine hydrochloride in the range of 2-10 ?g/ml and 24-120 ?g/ml, respectively. The percentage recoveries of montelukast and fexofenadine hydrochloride were found to be in the range of 99.09 and 99.81%, respectively. Both the drugs were subjected to acid and base hydrolysis, oxidation, photolytic, and thermal degradation conditions. The degradation products of montelukast and fexofenadine hydrochloride were well resolved from the pure drug with significant differences in their retention time values. This method can be successfully employed for simultaneous quantitative analysis of montelukast and fexofenadine hydrochloride in bulk drugs and formulations.

Pankhaniya, Mona; Patel, Parula; Shah, J. S.

2013-01-01

195

Degradation Pathway for Eplerenone by Validated Stability Indicating UP-LC Method  

PubMed Central

Degradation pathway for eplerenone is established as per ICH recommendations by validated and stability-indicating reverse phase liquid chromatographic method. Eplerenone is subjected to stress conditions of acid, base, oxidation, and thermal and photolysis. Significant degradation is observed in acid and base stress conditions. Four impurities are studied and the major degradant (RRT about 0.31) was identified by LC-MS and spectral analysis. The stress samples are assayed against a qualified reference standard and the mass balance is found close to 99.5%. Efficient chromatographic separation is achieved on a Waters symmetry C18 stationary phase with simple mobile phase combination delivered in gradient mode and quantification is carried at 240?nm at a flow rate of 1.0?mL?min?1. In the developed LC method the resolution between eplerenone and four potential impurities (imp-1, imp-2, imp-3, and imp-4) is found to be greater than 4.0. Regression analysis shows an r value (correlation coefficient) of greater than 0.999 for eplerenone and four potential impurities. This method is capable to detect the impurities of eplerenone at a level of 0.020% with respect to test concentration of 1.0?mg?mL?1 for a 20??L injection volume. The developed UPLC method is validated with respect to specificity, linearity and range, accuracy, precision, and robustness for impurities and assay determination.

Sudhakar Babu, Kondru; Madireddy, Venkataramanna; Indukuri, Venkata Somaraju

2012-01-01

196

Stability-Indicating HPTLC Determination of Imatinib Mesylate in Bulk Drug and Pharmaceutical Dosage  

NASA Astrophysics Data System (ADS)

A simple, selective, precise and stability-indicating high-performance thin-layer chromatographic method of analysis of imatinib mesylate both as a bulk drug and in formulations was developed and validated. The method employed HPTLC aluminum plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of chloroform:methanol (6:4, v/v). The system was found to give compact spot for imatinib mesylate (R f value of 0.53 ± 0.02). Densitometric analysis of imatinib mesylate was carried out in the absorbance mode at 276 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r 2 = 0.9966 ± 0.0013 with respect to peak area in the concentration range 100-1,000 ng per spot. The mean value ± SD of slope and intercept were 164.85 ± 0.72 and 1168.3 ± 8.26, respectively, with respect to peak area. The method was validated for precision, recovery, and robustness. The limits of detection and quantitation were 10 and 30 ng per spot, respectively. Imatinib mesylate was subjected to acid and alkali hydrolysis, and oxidation and thermal degradation. The drug undergoes degradation under acidic, basic, oxidation, and heat conditions. This indicates that the drug is susceptible to acid, base hydrolysis, oxidation, and heat. Statistical analysis proves that the method is repeatable, selective, and accurate for the estimation of the said drug. The proposed developed HPTLC method can be applied for identification and quantitative determination of imatinib mesylate in bulk drug and dosage forms.

Musmade, P.; Vadera, N.; Subramanian, G.

197

The use of voltage stability indices and proposed instability prediction to coordinate with protection systems  

Microsoft Academic Search

This paper proposes a methodology for mitigating the occurrence of cascading failure in stressed power systems. The methodology is essentially based on predicting voltage instability in the power system using a voltage stability index and then devising a corrective action in order to increase the voltage stability margin. The paper starts with a brief description of the cascading failure mechanism

R. Leelaruji; V. Knazkins

2009-01-01

198

Stability-indicating HPLC Method for Simultaneous Determination of Terbutaline Sulphate, Bromhexine Hydrochloride and Guaifenesin  

PubMed Central

The aim of the present study was the development and subsequent validation of a simple, precise and stability-indicating reversed phase HPLC method for the simultaneous determination of guaifenesin, terbutaline sulphate and bromhexine hydrochloride in the presence of their potential impurities in a single run. The photolytic as well as hydrolytic impurities were detected as 3,5-dihydroxybenzoic acid, 3,5-dihydroxybenzaldehyde, 1-(3,5-dihydroxyphenyl)-2-[(1,1-dimethylethyl) amino]-ethanone from terbutaline, 2-methoxyphenol and an unknown impurity identified as (2RS)-3-(2-hydroxyphenoxy)-propane-1,2-diol from guaifenesin. The chromatographic separation of all the three active components and their impurities was achieved on Wakosil II column, using phosphate buffer (pH 3.0) and acetonitrile as mobile phase which was delivered initially in the ratio of 80:20 (v/v) for 18 min, then changed to 60:40 (v/v) for next 12 min, and finally equilibrated back to 80:20 (v/v) for 10 min. Other HPLC parameters were: Flow rate at 1.0 ml/min, detection wavelengths 248 and 280 nm, injection volume 10 ?l. The calibration graphs plotted with five concentrations of each component were linear with a regression coefficient R2 >0.9999. The limit of detection and limit of quantitation were estimated for all the five impurities. The established method was then validated for linearity, precision, accuracy, and specificity and demonstrated to be applicable to the determination of the active ingredients in commercial and model cough syrup. No interference from the formulation excipients was observed. These results suggest that this LC method can be used for the determination of multiple active ingredients and their impurities in a cough and cold syrup.

Porel, A.; Haty, Sanjukta; Kundu, A.

2011-01-01

199

A validated stability-indicating gas chromatography method for determination of divalproex sodium impurities in pharmaceutical preparation.  

PubMed

A stability-indicating gas chromatography (GC) method has been developed and validated for the quantitative determination of divalproex sodium impurities in pharmaceutical preparation. A technique has been developed whereby the peak purity of a compound with poor UV detection can be determined using a gas chromatograph coupled with a mass spectrometer. The drug products were subjected to hydrolysis, oxidation, photolysis, and heat to apply stress conditions. The stability-indicating nature of the method has been proven by establishing peak purity of all stressed samples. The chromatographic separation was performed on a fused silica capillary (Quadrex-FFAP, 30 meter, 0.32 mm and 1 microm film thickness) column. The method validation results indicate that the method is specific, accurate, linear, reproducible, rugged, and robust. The effectiveness of the technique was demonstrated with stability sample analysis of divalproex sodium in its pharmaceutical preparation. PMID:20376833

Subasranjan, Acharya; Suresh, Pulluru; Srinivasulu, C; Hemant, Raoutray

2010-04-01

200

Stability indicating methods for the determination of some fluoroquinolones in the presence of their decarboxylated degrades.  

PubMed

Two stability-indicating methods, namely densitometric TLC and derivative spectrophotometry for the determination of the fluoroquinolone antibacterials lomefloxacin (Lfx), moxifloxacin (Mfx), and sparfloxacin (Sfx) in the presence of their acid degrades are described. Acid degradation was adopted and the main decarboxylated product separated by TLC. Degradation products were identified confirming a previously mentioned degradation scheme. The densitometric method is based on the separation of the intact drug from its acid degradation product on silica gel G plates using different mobile phases and the spots of the intact drugs were scanned at 288, 290, and 292 nm for Lfx, Mfx, and Sfx, respectively. The derivative spectrophotometric method utilizes first derivative D(1) UV spectrophotometry with zero crossing points at 295.2 nm for Lfx, 280.4 and 303.4 nm for Mfx, and 280.8 nm for Sfx. Regression analysis of Beer's plots showed good correlation in the concentration ranges 0.2-1.2, 0.1-1.4, and 0.5-2.0 microg/spot for Lfx, Mfx, and Sfx, respectively, in the densitometric method and 2-16 microg/ml for all drugs in the derivative spectrophotometric method. The proposed methods were successfully applied for the determination of the investigated drugs in bulk powder with mean percentage accuracy ranges from 98.93 to 101.25% for the TLC method and from 98.18 to 100.35% for the D(1) method. The proposed methods were also applied for the determination of the investigated drugs in their pharmaceutical dosage forms and their validity was assessed using the standard addition technique with mean percentage recovery ranging from 100.25 to 101.70% in the TLC method and from 99.27 to 102.12% in the D(1) method. The selectivity of the proposed methods was tested by the analysis of laboratory-prepared mixtures containing different percentages of the studied drugs and their acid degrades. The proposed methods were found selective for the determination of the intact drugs in the presence of up to 90% of their degrades in the TLC method and 70% for Lfx and 90% for Mfx and Sfx in the D(1) method. PMID:17139094

Salem, Maissa Yacoub; El-Guindi, Nabawia Mahmoud; Mikael, Hanaa Karam; Abd-El-Fattah, Laila El-Sayed

2006-12-01

201

Monitoring Cheddar cheese ripening by chemical indices of proteolysis  

Microsoft Academic Search

Zusammenfassung Die Proteolyse des Caseins während der Käsereifung wurde durch Peptidtrennung mit RPHPLC studiert. Zwei verschiedene Cheddarkäse unterschiedlicher Herstellung wurden während einer sechsmonatigen Reifungszeit bei 4 °C und 10 °C analysiert. Das RP-HPLC-Elutionsprofil von pH 4,6-löslichen Käseextrakten wies mehr als 120 Komponenten auf. Diese wurden durch RP-HPLC von Käseextrakten, die mit verschiedenen Ausschlußgrenzen ultrafiltriert wurden, in vier Molekülmassen-Bereiche eingeteilt: I30

Klaus-Peter Kaiser; Hans-Dieter Belitz; Rudolf Johann Fritsch

1992-01-01

202

Optimal placement of distributed generation with sensitivity factors considering voltage stability and losses indices  

Microsoft Academic Search

Loss minimization in distribution networks has considered as great significance recently since the trend to the distribution generation will require the most efficient operating scenario for economic viability variations. Furthermore, voltage instability phenomena can occur in distribution systems and caused a major blackout in the network. The decline of voltage stability level will restrict the increase of load served by

A. Parizad; A. Khazali; M. Kalantar

2010-01-01

203

Neural-network representation of Voltage Stability Indices at the voltage collapse  

Microsoft Academic Search

Representing system security in power flow based system models by the scalar magnitude of a Voltage Stability Index (VSI) may be a very difficult task, which may even render the applicability of such models impractical. VSIs at voltage collapse points are difficult to predict when reactive power generation limits are taken into account in system modeling. Therefore, this paper proposes

Guilherme G. Lage; Ricardo A. S. Fernandes; Geraldo R. M. da Costa

2011-01-01

204

Lichens as indicators of a perturbation\\/stability gradient in the Asperillo dunes, SW spain  

Microsoft Academic Search

In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is\\u000a an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo\\u000a dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is\\u000a eliminated, and (3) pine forest

J. B. Gallego Fernández; M. C. Díaz Barradas

1997-01-01

205

Errata to crisis stability indices for adaptive two-layer defenses  

SciTech Connect

An earlier treatment overestimated the survivability of an attacker`s non-alert aircraft and hence their contribution to his first strike. This report corrects the error and discusses its impact, which is primarily important for ground-based defenses. It reduces the attacker`s aircraft survival rates to about those of the defender`s, improving the stability properties of space-based defenses.

Canavan, G.H.

1992-05-01

206

Changes in gene expression in response to polyamine depletion indicates selective stabilization of mRNAs.  

PubMed Central

We used differential display analysis to identify mRNAs responsive to changes in polyamine synthesis. As an overproducing model we used the kidneys of transgenic hybrid mice overexpressing ornithine decarboxylase and S-adenosylmethionine decarboxylase, two key enzymes in polyamine biosynthesis. To identify mRNAs that respond to polyamine starvation, we treated Rat-2 cells with alpha-difluoromethylornithine, a specific inhibitor of polyamine biosynthesis. We isolated 41 partial cDNA clones, representing 37 differentially expressed mRNAs. Of these, 15 have similarity with known genes, five appear to be similar to reported expressed sequence tags and seventeen clones were novel sequences. Of the 35 mRNAs expressed differentially after alpha-difluoromethylornithine treatment, 26 were up-regulated. The expression of only three mRNAs was altered in the transgenic animals and all three were down-regulated. Determination of mRNA half-life of three of the mRNAs up-regulated in response to polyamine depletion revealed that the accumulation results from stabilization of the messages. Because most of the transcripts identified from Rat-2 cells suffering polyamine starvation were accumulated, we conclude that polyamine depletion, while blocking cell growth, is stabilizing mRNAs. This may be due to the lack of spermidine for post-translational modification of the eukaryotic initiation factor 5A, which plays a major role in mRNA turnover. The coupling of mRNA stabilization with cell-growth arrest in response to polyamine starvation provides cells with an economical way to resume growth after recovery from polyamine deficiency.

Veress, I; Haghighi, S; Pulkka, A; Pajunen, A

2000-01-01

207

Estimation of aggregate stability indices in Mediterranean soils by diffuse reflectance spectroscopy  

Microsoft Academic Search

The proportion of water stable aggregates larger than 0.25mm (WSA), mean weighted aggregate diameter (MWD) and water dispersible clay (WDC) are three good indicators of the risk of surface sealing, runoff generation and soil erosion by water. These aggregation indices are influenced by the contents in clay, iron oxides, calcium carbonate and organic matter, among other soil properties. Because these

J. C. Cañasveras; V. Barrón; M. C. del Campillo; J. Torrent; J. A. Gómez

2010-01-01

208

[Indications and limitations of minimally invasive stabilization of metastatic spinal disease].  

PubMed

The number of patients with symptomatic metastases increases from year to year. Especially spinal metastases often lead to severe pain which often cannot be treated adequately by conservative treatment. Surgeons are confronted with the risk of instability, pathological fractures and neurological failure and the surgical treatment necessary in most cases is nowadays becoming an even greater challenge. The surgical procedure has changed considerably in recent years. The therapy is patient-individualized, the selection of implants and technology is adapted to the physical condition of the patient and the progression of the underlying disease. The main targets of the surgical treatment of spinal metastases have to be sufficient pain reduction with restoration of mobility as well as with the prevention of neurological deficits caused by progressive osteolysis. There are two minimally invasive stabilization procedures which can basically be applied. Under certain circumstances a single kyphoplasty/vertebroplasty procedure can be sufficient, in contrast to the possibility of short or long percutaneous posterior stabilization in combination with selective decompression of neural structures. These percutaneous surgical procedures currently have an important place in the surgical treatment of spinal metastases. The advantages are a less traumatic intervention for patients with advanced malignant diseases and poor general condition. Low intraoperative loss of blood means less intraoperative stress for the patient and minor surgical approaches lead to rapid mobilization and effective pain relief. As a result the hospital stay is shorter, adjuvant therapy can be started earlier and patients can be discharged sooner. PMID:23989593

Josten, C; Glasmacher, S; Franck, A

2013-09-01

209

Circular dichroism and ultraviolet resonance Raman indicate little Arg-Glu side chain ?-helix peptide stabilization.  

PubMed

Electrostatic interactions between side chains can control the conformation and folding of peptides and proteins. We used circular dichroism (CD) and ultraviolet (UV) resonance Raman spectroscopy (UVRR) to examine the impact of side chain charge on the conformations of two 21 residue mainly polyala peptides with a few Arg and Glu residues. We expected that attractions between Arg-10 and Glu-14 side chains would stabilize the ?-helix conformation compared to a peptide with an Arg-14. Surprisingly, CD suggests that the peptide with the Glu-14 is less helical. In contrast, the UVRR show that these two peptides have similar ?-helix content. We conclude that the peptide with Glu-14 has the same net ?-helix content as the peptide with the Arg but has two ?-helices of shorter length. Thus, side chain interactions between Arg-10 and Glu-14 have a minor impact on ?-helix stability. The thermal melting of these two peptides is similar. However the Glu-14 peptide pH induced melting forms type III turn structures that form ?-helix-turn-?-helix conformations. PMID:21425805

Hong, Zhenmin; Ahmed, Zeeshan; Asher, Sanford A

2011-03-22

210

Evaluation of biodegradable rifampicin-bearing microsphere formulations using a stability-indicating high-performance liquid chromatographic assay.  

PubMed

The validation of a rapid and selective stability-indicating high-performance liquid chromatographic procedure for the determination of rifampicin (RIF) and its decomposition products in aqueous solution is described. Direct injection and column switching HPLC procedures have been compared and, owing to the increased sensitivity and precision, the latter has been applied to the study of RIF stability in the presence of isoascorbic acid at pH 7.4. The time-dependent hydrolytic decomposition of RIF to 3-formyl rifamycin SV (RSV) was found to be biexponential. Log concentration versus time plots of RIF and RSV decomposition were found to be parallel, indicating a pseudo equilibrium decomposition process. This feature allowed corrections for the amounts lost to secondary reactions to be calculated when the assay was applied to the determination of release characteristics of RIF from biodegradable poly-d, l-lactide-co-glycolide microspheres. PMID:9845778

Bain, D F; Munday, D L; Cox, P J

1998-12-01

211

Investigation of the microbial community structure and activity as indicators of compost stability and composting process evolution.  

PubMed

In a bid to identify suitable microbial indicators of compost stability, the process evolution during windrow composting of poultry manure (PM), green waste (GW) and biowaste was studied. Treatments were monitored with regard to abiotic factors, respiration activity (determined using the SOUR test) and functional microflora. The composting process went through typical changes in temperature, moisture content and microbial properties, despite the inherent feedstock differences. Nitrobacter and pathogen indicators varied as a monotonous function of processing time. Some microbial groups have shown a potential to serve as fingerprints of the different process stages, but still they should be examined in context with respirometric tests and abiotic parameters. Respiration activity reflected well the process stage, verifying the value of respirometric tests to access compost stability. SOUR values below 1 mg O(2)/g VS/h were achieved for the PM and the GW compost. PMID:19136252

Chroni, Christina; Kyriacou, Adamadini; Manios, Thrassyvoulos; Lasaridi, Konstantia-Ekaterini

2009-01-10

212

Stability-Indicating Micellar Liquid Chromatographic Method for the Determination of Clopidogrel. Application to Tablets and Content Uniformity Testing  

Microsoft Academic Search

A simple, stability-indicating, reversed-phase micellar liquid chromatographic method was developed for the analysis of the antiplatelet drug clopidogrel. Clopidogrel was determined in presence of its carboxylic acid degradation product, namely; SR26334. The analysis was carried out using a 150 mm × 4.6 mm i.d., 5 µm particle size Nucleodur MN-C18 column. The Mobile phase used was a solution containing 0.15 M sodium dodecyl sulphate and 10%

Fathalla Belal; Amina El-Brashy; Manal Eid; Jenny Jeehan Nasr

2009-01-01

213

A SINGLE COMMON STABILITY INDICATING ULTRA PERFORMANCE LIQUID CHROMATOGRAPHIC METHOD FOR ESTIMATION OF IMPURITIES IN FOUR ANGIOTENSIN II RECEPTOR BLOCKERS  

Microsoft Academic Search

A novel single common stability-indicating gradient reverse phase ultra performance liquid chromatographic (RP-UPLC) method was developed for the determination of purity of four angiotensin II receptor blockers namely valsartan, losartan potassium, irbesartan and telmisartan from respective finished dosage forms in presence of their impurities and forced degradation products. The method was developed using Waters Aquity BEH C18 column with mobile

Dantu Durga Rao; Galla Vamsi Krishna; A. Malleswara Reddy; L. kalyanaraman; K. Kyas

2012-01-01

214

Stability-Indicating LC-PDA Method for Determination of Idebenone in Nanoparticles Based on Chitosan and N -Carboxymethylchitosan  

Microsoft Academic Search

A forced degradation study of idebenone was conducted under conditions of UV irradiation, acid, basic and oxidative hydrolysis\\u000a and in order to develop an isocratic stability-indicating LC-UV method for drug quantification in chitosan and N-carboxymethylchitosan nanoparticles obtained by spray drying. The drug was more labile to alkaline treatment than under the\\u000a other forced degradation conditions. Idebenone and its degradation products

Clarissa M. de Amorim; Daisy J. A. Netz; Angelica G. Couto; Rilton A. de Freitas; Tania M. B. Bresolin

2009-01-01

215

Postural Stability of Biped Robots and the Foot-Rotation Indicator (FRI) Point  

Microsoft Academic Search

The focus of this paper is the problem of foot rotation in biped robots during the single-support phase. Foot rotation is an indication of postural instability, which should be carefully treated in a dynami- cally stable walk and avoided altogether in a statically stable walk. We introduce the foot-rotation indicator (FRI) point, which is a point on the foot\\/ground-contact surface

Ambarish Goswami

1999-01-01

216

Predictability of streamflow and particulate organic matter concentration as indicators of stability in prairie streams  

Microsoft Academic Search

Predictability of stream discharge and particulate organic matter (POM) in the water column was estimated, using Colwell's indices of constancy and contingency, for 6 Texas prairie streams (1 each of 2nd, 3rd, and 4th order with intermittent or perennial discharge). Stream discharge in these 6 prairie streams varied between 0 and 36000 1 s-1, depending on the stream and season.

B. H. Hill; T. J. Gardner; O. F. Ekisola

1992-01-01

217

Stability-indicating spectrofluorimetric method for determination of itopride hydrochloride in raw material and pharmaceutical formulations.  

PubMed

A simple, sensitive and rapid spectrofluorimetric method for determination of itopride hydrochloride in raw material and tablets has been developed. The proposed method is based on the measurement of the native fluorescence of the drug in water at 363 nm after excitation at 255 nm. The relative fluorescence intensity-concentration plot was rectilinear over the range of 0.1-2 ?g/mL (2.5?×?10(-7)-5.06?×?10(-6) mole/L), with good correlation (r?=?0.9999), limit of detection of 0.015 ?g/mL and a lower limit of quantification of 0.045 ?g/mL. The described method was successfully applied for the determination of itopride hydrochloride in its commercial tablets with average percentage recovery of 100.11?±?0.32 without interference from common excipients. Additionally, the proposed method can be applied for determination of itopride in combined tablets with rabeprazole or pantoprazole without prior separation. The method was extended to stability study of itopride. The drug was exposed to acidic, alkaline, oxidative and photolytic degradation according to ICH guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and oxidative degradation of the drug. A proposal for the degradation pathways was postulated. PMID:23852162

Walash, Mohamed I; Ibrahim, Fawzia; Eid, Manal I; El Abass, Samah Abo

2013-07-14

218

Development and validation of a stability indicating UPLC method for determination of ticlopidine hydrochloride in its tablet formulation  

PubMed Central

The objective of the current study was the development of a simple, precise and accurate isocratic reversed-phase stability indicating Ultra Performance Liquid Chromatography [UPLC] assay method and validated for determination of ticlopidine hydrochloride in solid pharmaceutical dosage forms. Isocratic separation was achieved on a Zorbax SB-C18 (50 mm × 4.6 mm, 1.8 ?m) column using mobile phase of methanol–0.01 M ammonium acetate buffer, pH 5.0 (80:20, v/v) at a flow rate of 0.8 ml min?1, the injection volume was 4.0 ?l and the detection was carried out at 235 nm by using photo-diode array detector. The drug was subjected to oxidation, hydrolysis, photolysis and heat to apply stress condition. The method was validated for specificity, linearity, precision, accuracy, robustness and solution stability. The method was linear in the drug concentration range of 62.5–375 ?g ml?1 with a correlation coefficient of 0.9999. The precision (relative standard deviation – RSD) of six samples was 1.31% for repeatability and the intermediate precision [RSD] among six-sample preparation was 0.77%. The accuracy (recovery) was between 98.80% and 101.50%. Degradation products produced as a result of stress studies did not interfere with detection of ticlopidine hydrochloride and the assay can thus be considered stability indicating.

Ram, Vijay; Kher, Govind; Dubal, Kapil; Dodiya, Bhavesh; Joshi, Hitendra

2011-01-01

219

Study of doxofylline and its degradation products in bulk drug by a newly developed stability-indicating HPLC method.  

PubMed

The purpose of this work was to study the stability behavior of doxofylline under different stress conditions and to develop a sensitive stability-indicating HPLC assay method. The stress conditions applied included heat, moisture, acid-base hydrolysis, oxidation, and UV light. The drug was particularly labile under oxidative and thermal stress conditions, with 58.40 and 53.90% degradation, respectively. Good resolution of drug from degradation products formed under stress conditions was achieved on a C18 column using 10 mM KH2PO4 buffer solution (pH 6) methanol (40 + 60, v/v) as the mobile phase (pH 7.2). The flow rate was 1 mLlmin, and the detection wavelength was 273 nm. The method was validated for linearity, range, precision, accuracy, LOD, and LOQ. The RSD was found to be <2%. Since the method effectively separates the drug from its degradation products, it can be used as a stability-indicating method. PMID:24000749

Patil, Priti S; Hamrapurkar, Purnima D; Phale, Mitesh D; Desai, Masti I; Pawar, Sandeep B

220

Development and validation of a stability indicating UPLC method for determination of ticlopidine hydrochloride in its tablet formulation.  

PubMed

The objective of the current study was the development of a simple, precise and accurate isocratic reversed-phase stability indicating Ultra Performance Liquid Chromatography [UPLC] assay method and validated for determination of ticlopidine hydrochloride in solid pharmaceutical dosage forms. Isocratic separation was achieved on a Zorbax SB-C18 (50 mm × 4.6 mm, 1.8 ?m) column using mobile phase of methanol-0.01 M ammonium acetate buffer, pH 5.0 (80:20, v/v) at a flow rate of 0.8 ml min(-1), the injection volume was 4.0 ?l and the detection was carried out at 235 nm by using photo-diode array detector. The drug was subjected to oxidation, hydrolysis, photolysis and heat to apply stress condition. The method was validated for specificity, linearity, precision, accuracy, robustness and solution stability. The method was linear in the drug concentration range of 62.5-375 ?g ml(-1) with a correlation coefficient of 0.9999. The precision (relative standard deviation - RSD) of six samples was 1.31% for repeatability and the intermediate precision [RSD] among six-sample preparation was 0.77%. The accuracy (recovery) was between 98.80% and 101.50%. Degradation products produced as a result of stress studies did not interfere with detection of ticlopidine hydrochloride and the assay can thus be considered stability indicating. PMID:23960754

Ram, Vijay; Kher, Govind; Dubal, Kapil; Dodiya, Bhavesh; Joshi, Hitendra

2011-03-21

221

[Screening of alloantibodies: stability of false positive results as a quality indicator].  

PubMed

Screening of alloantibodies is required before each transfusion. As part of our blood bank quality assurance, we have developed a quality indicator to monitor these false positive antibody results. We have studied 25.162 samples: sera were first screened by automated column agglutination technology (CAT). Positive results were found in 1.365 of the 25.162 samples. False positive results, ie positive screening test followed by a negative identification, were found in 271 (20%) cases. In the 116 patients remaining (43%) no factor could be evidenced. Interestingly, the percentage of patients with false positive antibody screening was stable month after month. In our experience, this percentage is very stable, it may be used as an indicator of quality laboratory and its unusual variation allows to suspect alterations of the reagents (hemolysis, loss of specificity, sensitivity). PMID:21896414

Flourié, Françoise; Duboeuf, Sébastien; Fay, Murielle; Garraud, Olivier

222

A validated stability-indicating LC method for estimation of etoposide in bulk and optimized self-nano emulsifying formulation: Kinetics and stability effects  

PubMed Central

The present investigation was aimed to establish a validated stability-indicating liquid chromatographic method for the estimation of etoposide (ETP) in bulk drug and self-nano emulsifying formulation. ETP was successfully separated from the degradation products formed under stress conditions on LiChrospher 100 C18 reverse-phase column (a 250 mm × 4.6 mm i.d., 5-?m particle size) using 55:45 (v/v) acetonitrile–phosphate buffer saline (pH 4.5) as the mobile phase, at a flow rate of 1.0 mL min?1 and detection at 283 nm. The response was a linear function of analyte concentration (R2 > 0.9997) over the concentration range of 0.05–50 ?g mL?1. The method was validated for precision, accuracy, robustness, sensitivity and specificity. The % recovery of ETP at three different levels (50%, 100% and 150%) ranged between 93.84% and 100.06% in optimized self-nano emulsifying formulation, Etosid® soft-gelatin capsule and Fytosid® injection. First-order degradation kinetics of ETP were observed under acidic and alkaline conditions. The method was also applied for the stability assessment of self-nano emulsifying formulation under accelerated conditions, the formulation was found to be stable at all storage conditions with the shelf-life of 2.37 years at 25 °C. The method holds promise for routine quality control of ETP in bulk, pharmaceutical formulations as well as in stability-indicating studies.

Akhtar, Naseem; Talegaonkar, Sushama; Khar, Roop Kishan; Jaggi, Manu

2012-01-01

223

Synthesis, characterization and stability of a luteinizing hormone-releasing hormone (LHRH)-functionalized poly(amidoamine) dendrimer conjugate.  

PubMed

Cancer targeting is crucial for cancer detection, therapy and targeted drug delivery. A dendrimer-peptide conjugate has been synthesized based on poly(amidoamine) dendrimer generation 5 (PAMAM G5) as a platform and a luteinizing hormone-releasing hormone (LHRH) peptide as a targeting moiety. The synthesized conjugate was fully characterized using nuclear magnetic resonance (NMR), UV-Vis spectrometry, reverse-phase high-performance liquid chromatography (RP-HPLC) and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Further stability experiments showed that the synthesized conjugate was stable after 72-h incubation in phosphate-buffered saline (PBS) buffer (pH 7.4) at 37 degrees C. The synthesized conjugate may find applications in biomedical targeting, gene delivery and imaging. PMID:18177559

Bi, Xiangdong; Shi, Xiangyang; Baker, James R

2008-01-01

224

A Validated Stability-Indicating HPLC Method for Routine Analysis of an Injectable Lincomycin and Spectinomycin Formulation  

PubMed Central

Lincomycin and spectinomycin combination therapy is widely used in veterinary medicine for the treatment of gastrointestinal and respiratory infections caused by lincomycin- and spectinomycin-sensitive microorganisms. A simple, reverse phase HPLC method for the analysis of samples of an injectable lincomycin and spectinomycin preparation containing a mixture of inactive excipients has been developed. The HPLC was carried out using the RP-C18 (250 mm × 4.0 mm, 5 ?m) column, with the gradient mobile phase consisting of an acetonitrile and phosphate buffer at pH 6; the flow rate of 1 mL/min and ultraviolet detection at 220 nm. This method was validated in accordance with both FDA and ICH guidelines and showed good linearity, accuracy, precision, selectivity, and system suitability results within the acceptance criteria. A stability-indicating study was also carried out and indicated that this method can also be used for purity and degradation evaluation of these formulations.

Abualhasan, Murad N.; Batrawi, Nidal; Sutcliffe, Oliver B.; Zaid, Abdel Naser

2012-01-01

225

Stability-indicating HPTLC method for simultaneous determination of nateglinide and metformin hydrochloride in pharmaceutical dosage form.  

PubMed

A stability indicating high performance thin layer chromatography (HPTLC) method was developed and validated for determination of two anti-diabetic drugs, nateglinide and metformin hydrochloride in co-formulations. Study was performed on pre-coated silica gel HPTLC plates using chloroform:ethyl acetate:acetic acid (4:6:0.1 v/v/v) as the mobile phase. A TLC scanner set at 216 nm was used for direct evaluation of the chromatograms in the reflectance/absorbance mode. Method was validated according to ICH guidelines. The correlation coefficients of calibration curves were found to be 0.996 and 0.995 in the concentration range of 200-2400 and 500-3000 ng band(-1) for nateglinide and metformin, respectively. The method had an accuracy of 99.72% for nateglinide and 100.08% for metformin hydrochloride. The method had the potential to determine these drugs simultaneously from dosage forms without any interference of the tablets excipients. Nateglinide and metformin hydrochloride were also subjected to acid, base, oxidation, wet, heat and photo-degradation studies. The degradation products obtained were well resolved from the pure drugs with significantly different Rf values. As the method could effectively separate the drugs from its degradation products, it can be used for stability-indicating analysis. PMID:23960763

Thomas, Asha Byju; Patil, Shrikrushna Digambar; Nanda, Rabindra Kumar; Kothapalli, Lata Prasad; Bhosle, Shital Shridhar; Deshpande, Avinash Devidas

2011-07-05

226

Stability-indicating HPTLC method for simultaneous determination of nateglinide and metformin hydrochloride in pharmaceutical dosage form  

PubMed Central

A stability indicating high performance thin layer chromatography (HPTLC) method was developed and validated for determination of two anti-diabetic drugs, nateglinide and metformin hydrochloride in co-formulations. Study was performed on pre-coated silica gel HPTLC plates using chloroform:ethyl acetate:acetic acid (4:6:0.1 v/v/v) as the mobile phase. A TLC scanner set at 216 nm was used for direct evaluation of the chromatograms in the reflectance/absorbance mode. Method was validated according to ICH guidelines. The correlation coefficients of calibration curves were found to be 0.996 and 0.995 in the concentration range of 200–2400 and 500–3000 ng band?1 for nateglinide and metformin, respectively. The method had an accuracy of 99.72% for nateglinide and 100.08% for metformin hydrochloride. The method had the potential to determine these drugs simultaneously from dosage forms without any interference of the tablets excipients. Nateglinide and metformin hydrochloride were also subjected to acid, base, oxidation, wet, heat and photo-degradation studies. The degradation products obtained were well resolved from the pure drugs with significantly different Rf values. As the method could effectively separate the drugs from its degradation products, it can be used for stability-indicating analysis.

Thomas, Asha Byju; Patil, Shrikrushna Digambar; Nanda, Rabindra Kumar; Kothapalli, Lata Prasad; Bhosle, Shital Shridhar; Deshpande, Avinash Devidas

2011-01-01

227

A Stability-indicating High Performance Liquid Chromatographic Assay for the Simultaneous Determination of Atenolol and Lercanidipine Hydrochloride in Tablets  

PubMed Central

A simple, rapid, precise and accurate isocratic reversed phase stability indicating HPLC method was developed and validated for the simultaneous determination of atenolol and lercanidipine hydrochloride in commercial tablets. The chromatographic separation was achieved on phenomenex Gemini C18 (250×4.6 mm, 5 ?m) column using a mobile phase consisting of acetonitrile and buffer (20 mM potassium dihydrogen phosphate pH 3.5) in the ratio of (55:45, v/v) at a flow rate of 1.0 ml/min and UV detection at 235 nm. The linearity of the proposed method was investigated in the range of 40-160 ?g/ml (r2=0.9995) for atenolol and 8-32 ?g/ml (r2=0.9993) for lercanidipine. Degradation products produced as a result of stress studies did not interfere with the detection of atenolol and lercanidipine and the assay can thus be considered stability-indicating.

Kaila, H. O.; Ambasana, M. A.; Thakkar, R. S.; Saravaia, H. T.; Shah, A. K.

2011-01-01

228

3D fluorescence-based characterization of dissolved organic matter components and their impact on soil-structure stability indices  

NASA Astrophysics Data System (ADS)

Stable soil aggregates and structure are usually associated with increased levels of soil organic matter. A significant fraction of the latter is comprised of humic substances (HS). Opposing findings on the contribution of HS to both stabilization and increased dispersivity of soil aggregates have been reported; these findings could be related to the heterogeneity in the chemical composition of the HS. The objectives of this research were: (i) to characterize the compositional heterogeneity of HS and dissolved organic matter (DOM) in soil solutions, (ii) to evaluate the relations between general soil properties (e.g., organic matter, clay and calcium carbonate content, cation exchange capacity) and concentration and composition of DOM and HS in soil solution, and (iii) to examine the relationships between properties associated with soil structure such as aggregate stability and hydraulic conductivity and the composition of DOM and HS. The composition of HS and DOM in aqueous extracts, obtained from samples collected from cultivated fields of four Israeli soils (loamy sand, loam, sandy clay and clay), was characterized and quantified using 3D fluorescence (and UV-absorption) spectroscopy together with parallel factor analysis (PARAFAC) supported by dissolved organic carbon (DOC) measurements. Variability in the HS/DOM composition was obtained by including soils with a different history of irrigation, i.e. irrigated by fresh water and by treated wastewater. PARAFAC analysis provided scores proportional to concentrations of three major fluorescent DOM components, two were considered to represent HS and the third to represent proteinous matter (containing tryptophan). Soil structure had been characterized by saturated hydraulic conductivity and an index for aggregate stability. PARAFAC analysis demonstrated that concentrations of fluorescent DOM components in aqueous extracts were influenced by the type of water used for irrigation. This influence was distinctly affected by soil type. In clayey soils, samples irrigated with treated wastewater yielded smaller concentrations of extractable HS components compared with samples irrigated with fresh water. In the loamy sand and loam, concentrations of HS and proteinous matter in samples irrigated with treated wastewater were greater than those from samples irrigated with freshwater. These differences suggest that some interactions between soil clay and the effluent-borne OM may occur leading to reduced extractability of organic components in the clayey soils. The structural stability determinants of soils studied correlated significantly (at the p<0.05 level) with the concentrations of the three fluorescent DOM components but not with DOC concentration. In the clayey soils, the decrease in soil stability indices correlated with the decrease in concentrations of the extractable HS components, both induced by irrigation with treated wastewater. Our results suggest that changes in soil indices representing soil structure and stability, induced by changes in irrigation water quality, could be associated with changes in the concentration of HS components.

Levy, Guy; Lordian, Anna; Borisover, Mikhail

2010-05-01

229

Stability-indicating HPLC-DAD/UV-ESI/MS impurity profiling of the anti-malarial drug lumefantrine  

PubMed Central

Background Lumefantrine (benflumetol) is a fluorene derivative belonging to the aryl amino alcohol class of anti-malarial drugs and is commercially available in fixed combination products with ?-artemether. Impurity characterization of such drugs, which are widely consumed in tropical countries for malaria control programmes, is of paramount importance. However, until now, no exhaustive impurity profile of lumefantrine has been established, encompassing process-related and degradation impurities in active pharmaceutical ingredients (APIs) and finished pharmaceutical products (FPPs). Methods Using HPLC-DAD/UV-ESI/ion trap/MS, a comprehensive impurity profile was established based upon analysis of market samples as well as stress, accelerated and long-term stability results. In-silico toxicological predictions for these lumefantrine related impurities were made using Toxtree® and Derek®. Results Several new impurities are identified, of which the desbenzylketo derivative (DBK) is proposed as a new specified degradant. DBK and the remaining unspecified lumefantrine related impurities are predicted, using Toxtree® and Derek®, to have a toxicity risk comparable to the toxicity risk of the API lumefantrine itself. Conclusions From unstressed, stressed and accelerated stability samples of lumefantrine API and FPPs, nine compounds were detected and characterized to be lumefantrine related impurities. One new lumefantrine related compound, DBK, was identified and characterized as a specified degradation impurity of lumefantrine in real market samples (FPPs). The in-silico toxicological investigation (Toxtree® and Derek®) indicated overall a toxicity risk for lumefantrine related impurities comparable to that of the API lumefantrine itself.

2011-01-01

230

A Stability-indicating HPLC Method for Assay of Lercanidipine Hydrochloride in Tablets and for Determining Content Uniformity  

PubMed Central

A simple, precise and accurate HPLC method has been developed and validated for assay of lercanidipine hydrochloride in tablets and for determination of content uniformity. An isocratic separation was achieved using a Chromasil YMC Pack C8, 150 × 4.6 mm i.d., 5µm particle size columns with a flow rate of 1 ml/min and using a UV detector to monitor the elute at 240 nm. The mobile phase consisted of 0.02 M ammonium dihydrogen phosphate buffer:methanol (35:65, v/v) with pH 3.5 adjusted with phosphoric acid. The method was validated for specificity, linearity, pre-cision, accuracy, robustness and solution stability. The specificity of the method was deter-mined by assessing interference from the placebo and by stress testing of the drug (forced degradation). The method was linear over the concentration range of 20-80 µg/ml (r2= 0.9992) with a limit of detection and quantitation of 0.1 and 0.3 µg/ml respectively. Intraday and interday system and method precision were determined and accuracy was between 99.3-101.9 %. The method was found to be robust and suitable for assay of lercanidipine hydrochloride in a tablet formulation and for determination of content uniformity. Degradation products resulting from the stress studies did not interfere with the detection of lercanidipine hydrochloride and the assay is thus stability-indicating.

Kaila, H. O.; Ambasana, M. A.; Thakkar, R. S.; Saravaia, H. T.; Shah, A. K.

2010-01-01

231

Development and validation of a stability-indicating analytical method for the quantitation of oxytocin in pharmaceutical dosage forms.  

PubMed

A single stability-indicating assay for oxytocin (OT) in pharmaceutical dosage forms using gradient elution over 21 min has been reported in the literature. Furthermore, published and compendial methods for the analysis of OT containing dosage forms also involve using HPLC with gradient elution and complicated mobile phases that include hydrophobic ion pairing agents. A simple isocratic and stability-indicating assay was developed and validated. The conditions are as follows, column: Phenomenex C18 Hypersil, 5 microm packing, 4.6 mm x 150 mm with acetonitrile-phosphate buffer (pH 5; 0.08 M) (20:80) as the mobile phase with UV detection at 220 nm The method was found to be specific for OT in the presence of degradation products and chlorbutol (preservative) with an overall analytical run time of 16 min. Accuracy was determined to be 0.77-1.18% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22-1.04%R.S.D. while the inter-day precision (intermediate precision) was found to be 1.27-1.68%R.S.D. for the samples studied. The calibration curve was found to be linear with the equation y = 1.81x + 0.02 and a linear regression coefficient of 0.9991 over the range 0.4-12.0 IU/ml. The LOD and the LOQ were determined to be 0.1 and 0.4 IU/ml, respectively. Syntocinon, a commercially available dosage form of OT was assayed resulting in 100.5-106.6% recovery of the label claim and an average of 10.04 IU/ml. PMID:16920323

Chaibva, F A; Walker, R B

2006-08-22

232

Stability-indicating assay of repaglinide in bulk and optimized nanoemulsion by validated high performance thin layer chromatography technique  

PubMed Central

A sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic (HPTLC) method for analysis of repaglinide both as a bulk drug and in nanoemulsion formulation was developed and validated. The method employed TLC aluminum plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of chloroform/methanol/ammonia/glacial acetic acid (7.5:1.5:0.9:0.1, v/v/v/v). This system was found to give compact spots for repaglinide (Rf value of 0.38 ± 0.02). Repaglinide was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. Also, the degraded products were well separated from the pure drug. Densitometric analysis of repaglinide was carried out in the absorbance mode at 240 nm. The linear regression data for the calibration plots showed good linear relationship with r2= 0.998 ± 0.032 in the concentration range of 50-800 ng. The method was validated for precision, accuracy as recovery, robustness and specificity. The limits of detection and quantitation were 0.023 and 0.069 ng per spot, respectively. The drug undergoes degradation under acidic and basic conditions, oxidation and dry heat treatment. All the peaks of the degraded product were resolved from the standard drug with significantly different Rf values. Statistical analysis proves that the method is reproducible and selective for the estimation of the said drug. As the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating one. Moreover, the proposed HPTLC method was utilized to investigate the degradation kinetics in 1M NaOH.

Akhtar, Juber; Fareed, Sheeba; Aqil, Mohd

2013-01-01

233

Diurnal variability of stability indices observed using radiosonde observations over a tropical station: Comparison with microwave radiometer measurements  

NASA Astrophysics Data System (ADS)

Convection plays an important role in maintaining the thermodynamic structure of the atmosphere particularly in the tropical regions and it is often associated with clouds and precipitation. In the present study we report the diurnal variation of various stability indices observed using intensive radiosonde observations made during October 2010 to October 2011 over Indian tropical region, Gadanki (13.5°N, 79.2°E). Simultaneous co-located microwave radiometer (MWR) observations collected during April-October 2011 are used for comparison. Detailed comparison between these two independent techniques has been made which will be very much useful in assessing the data from MWR for Nowcasting. In general, MWR observations show warm (cold) bias in the temperature, except at 0.5 km, when compared to radiosonde observations below (above) 3-4 km, assuming latter as a standard technique. In case of water vapor, MWR observations show wet (dry) bias below (above) 2-3 km depending on the time. Nevertheless, very good comparison in several convection indices is noticed between the two different techniques, particularly in the trends though some differences are noticed in the amplitudes. For about 25% of time MWR is unable to estimate the Convective Available Potential Energy (CAPE) as equilibrium level is above the altitude that MWR can detect. Strong diurnal variation in CAPE and other thermodynamic parameters is noticed with maximum in the afternoon and minimum in the early morning hours in all the seasons except in winter over this tropical station.

Ratnam, M. Venkat; Santhi, Y. Durga; Rajeevan, M.; Rao, S. Vijaya Bhaskara

2013-04-01

234

Stability-indicating Reversed-phase Liquid Chromatographic Method for Simultaneous Determination of Losartan Potassium and Ramipril in Tablets  

PubMed Central

A stability-indicating reversed-phase liquid chromatographic method has been developed and validated for simultaneous determination of losartan potassium and ramipril. Separations were achieved using a C18 column with mobile phase consisting of acetonitrile and (0.2% v/v, pH 2.5) aqueous trifluoroacetic acid (45:55, v/v) in isocratic mode at 1 ml/min flow rate. Column effluent was monitored at 210 nm using a UV detector. The method was validated for selectivity, linearity, accuracy, precision, sensitivity and robustness. Novel microwave-assisted forced degradation technique was employed for evaluation of selectivity. The method demonstrated excellent linearity for losartan potassium and ramipril with regression coefficients of 0.9999 and 0.9998, respectively. The linearity range was found to be 62.5-5000 ng/ml and 125-10,000 ng/ml with the mean percentage recoveries of 100.36% (±2.27) and 100.16% (±3.33) for losartan potassium and ramipril, respectively. In a robustness study, a full factorial design revealed that the analytical response remains unaffected by small variations in the critical chromatographic factors. The method was found to be sensitive with quantification limits of 44.30 and 79.93 ng/ml for losartan potassium and ramipril. The method was successfully employed for the determination of losartan potassium and ramipril in commercially available and in-house prepared tablets.

Kollipara, S.; Bende, G.; Bansal, Y.; Saha, R.

2012-01-01

235

New Stability-Indicating RP-UFLC Method for Determination of Trospium Chloride in Tablet Dosage Form  

PubMed Central

A simple, precise, and accurate isocratic RP-UFLC stability-indicating assay method has been developed to determine trospium chloride in tablet dosage form. Isocratic separation was achieved on an Enable-C18G (250 mm × 4.6 mm i.d., particle size 5 ?m) column at room temperature, the mobile phase consisted of acetonitrile:0.01M TBAHS (50:50, v/v) at a flow rate of 1.0 ml/min, the injection volume was 20 ?l, and PDA detection was carried out at 215 nm. The drug was subjected to acid and alkali hydrolysis, oxidation, photolysis, and heat as stress conditions. The method was validated for specificity, linearity, precision, accuracy, robustness, and system suitability. The method was linear in the drug concentration range of 10–300 ?g/ml with the correlation coefficient being 0.999. The RSD for repeatability and intermediate precision was well below 2%. The mean recoveries were between 100.52–101.68% for trospium chloride.

Panda, Sagar Suman; Ravi Kumar, Bera V. V.; Mohanta, Ganeswar; Dash, Rabisankar; Patel, Pinkal Kumar

2012-01-01

236

Measuring sperm whales from their clicks: Stability of interpulse intervals and validation that they indicate whale length  

NASA Astrophysics Data System (ADS)

Multiple pulses can often be distinguished in the clicks of sperm whales (Physeter macrocephalus). Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397-417] proposed that this results from reflections within the head, and thus that interpulse interval (IPI) is an indicator of head length, and by extrapolation, total length. For this idea to hold, IPIs must be stable within individuals, but differ systematically among individuals of different size. IPI stability was examined in photographically identified individuals recorded repeatedly over different dives, days, and years. IPI variation among dives in a single day and days in a single year was statistically significant, although small in magnitude (it would change total length estimates by <3%). As expected, IPIs varied significantly among individuals. Most individuals showed significant increases in IPIs over several years, suggesting growth. Mean total lengths calculated from published IPI regressions were 13.1 to 16.1 m, longer than photogrammetric estimates of the same whales (12.3 to 15.3 m). These discrepancies probably arise from the paucity of large (12-16 m) whales in data used in published regressions. A new regression is offered for this size range.

Rhinelander, Marcus Q.; Dawson, Stephen M.

2004-04-01

237

Stability-indicating high-performance liquid chromatographic assay for alpha-methyldopa in sustained-release capsules.  

PubMed

A stability-indicating high-performance liquid chromatographic assay has been developed for the analysis of alpha-methyldopa (MD) in sustained-release capsules and in the presence of MD decomposition products and an MD industrial impurity, 3-O-methyl-methyldopa (MMD). The method utilizes reversed-phase chromatography (cyano-bonded column), an acidic mobile phase containing sodium heptanesulphonate as ion-pairing reagent and UV detection. Detector responses were linear in the ranges 0.5-200 microgram/ml for MD and 0.2-100 microgram/ml for MMD. The mean recoveries of MD from authentic sample and sustained-release capsules were 100.09 +/- 0.38 and 100.38 +/- 0.46%, respectively. The recovery of MD added to degraded MD, were 99.69% by the proposed method and 153.13% by the US Pharmacopeial (USP) spectrophotometric method. The method is sensitive, accurate and rapid and can be used in routine analysis for MD. PMID:1770082

Metwally M el-S

1991-07-19

238

Stability-indicating HPLC method for simultaneous determination of clidinium bromide and chlordiazepoxide in combined dosage forms.  

PubMed

The study describes development and subsequent validation of a stability indicating reverse-phase high-performance liquid chromatography method for the simultaneous estimation of clidinium bromide (CLI) and chlordiazepoxide (CHLOR) from their combination drug product. Chromatographic separations are performed at ambient temperature on a Phenomenex Luna C(18) (250 mm x 4.6 mm, i.d., 5 microm) column using a mobile phase consisting of potassium dihydrogen phosphate buffer (0.05 M, pH 4.0 adjusted with 0.5% orthophosphoric acid)-methanol- acetonitrile (40:40:20, v/v/v). The flow rate is 1.0 mL/min, and the detection wavelength is 220 nm. The method is validated with respect to linearity, precision, accuracy, system suitability, and robustness. The utility of the procedure is verified by its application to marketed formulations that were subjected to accelerated degradation studies. The method distinctly separated the drug and degradation products even in actual samples. The products formed in marketed tablet dosage forms are similar to those formed during stress studies. PMID:20223092

Pathak, Ashutosh; Rai, Pallavi; Rajput, Sadhana J

2010-03-01

239

Stability-indicating simultaneous determination of paracetamol and three of its related substances using a direct GC/MS method.  

PubMed

A simple, direct, and selective stability-indicating GC/MS procedure was developed for the simultaneous determination of paracetamol (PR) and three of its related substances: 4-aminophenol (4-AP), acetanilide (AD), and 4'-chloroacetanilide (4-CA). The method involved resolution of the underivatized compounds using a 100% dimethylpolysiloxane (Rtx-1) column, and MS detection was carried out in the electron-impact mode. The four compounds were completely resolved in less than 11 min. The fragmentation pathways for the four compounds were described, and the structures of the major fragment ions peaks were proposed. Quantification of the analytes was based on measuring their peak areas. The reliability and analytical performance of the proposed method including linearity, range, precision, accuracy, and detection and quantification limits were statistically validated. Calibration curves were linear over the ranges 75-500, 25-350, 25-350, and 25-350 microg/mL for PR, 4-AP, AD, and 4-CA, respectively. The proposed method was successfully applied for the determination of PR and its related substances in laboratory-prepared mixtures of different proportions. Also, it was applied for the assay of PR in several commercially available pharmaceutical formulations with recoveries of 98.95-100.76%. PMID:20166578

Belal, Tarek; Awad, Tamer; Clark, C Randall

240

A Validated Stability-Indicating Liquid Chromatographic Method for Determination of Degradation Impurities and Diastereomers in Voriconazole Tablets  

PubMed Central

A reversed-phase gradient liquid chromatographic method has been developed for the quantitative determination of Voriconazole, along with its degradation and diastereomeric impurities in tablet dosage form. Chromatographic separation has been achieved on an Inertsil ODS 3V, 150 × 4.6 mm, 5 ?m column. The mobile phase consisting of solvent A 0.05 molar (M) potassium dihydrogen phosphate (pH 2.5 buffer) and solvent B (mixture of acetonitrile and methanol in the ratio 90:10 (v/v)), was delivered at a flow rate of 1.2 mL min?1 with the detection wavelength at 256 nm. Resolution of Voriconazole and all five potential impurities was achieved at greater than 2.0 for all pairs of compounds. The drug was subjected to stress conditions such as oxidative, acid and base hydrolysis, and thermal and photolytic degradation. Voriconazole was found to degrade significantly under base hydrolysis stress conditions compared to acid hydrolysis stress conditions. The degradation products were well-resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. The stressed samples were assayed against a reference standard and the mass balance was found to be close to 99.0%. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, and robustness.

Shaikh, Kabeer A.; Patil, Ashish T.

2012-01-01

241

Stability-indicating methods for the determination of a mixture of almitrine and raubasine by derivative spectrophotometry.  

PubMed

A second-derivative spectrophotometric method ((2)D) and a derivative ratio spectrum zero crossing ((1)DD) method were used to determine raubasine and almitrine dismesylate in the presence of raubasine degradation product, using methanol as a solvent. Linear relationships were obtained in the range from 6-20 microg ml(-1) raubasine for the ((2)D) method and 12-24 microg ml(-1) almitrine dismesylate for the ((1)DD) method. By applying these methods it was possible to determine raubasine in its pure powdered form with an accuracy of 99.93 +/- 1.116 (n = 8) for the ((2)D) method and almitrine dismesylate with an accuracy of 99.98 +/- 0.602 (n = 7) for the ((1)DD) method.Laboratory-prepared mixtures containing different ratios of raubasine, almitrine dismesylate and raubasine degradation product were analysed and the proposed methods were valid up to 50% of raubasine degradation product. They were found to be suitable stability-indicating assay methods for raubasine and almitrine dismesylate in pharmaceutical formulations. PMID:20355207

El-Sayed, Mohammad A

2009-06-01

242

Comparing prediction power and stability of broadband and hyperspectral vegetation indices for estimation of green leaf area index and canopy chlorophyll density  

Microsoft Academic Search

Hyperspectral reflectance data representing a wide range of canopies were simulated using the combined PROSPECT+SAIL model. The simulations were used to study the stability of recently proposed vegetation indices (VIs) derived from adjacent narrowband spectral reflectance data across the visible (VIS) and near infrared (NIR) region of the electromagnetic spectrum. The prediction power of these indices with respect to green

N. h. Broge; E. Leblanc

2001-01-01

243

Validated stability-indicating methods for the determination of nizatidine in the presence of its sulfoxide derivative.  

PubMed

Four new selective, precise, and accurate methods are described for the determination of nizatidine (NIZ) in the presence of its sulfoxide derivative in both the raw material and pharmaceutical preparations. Method A is based on zero-order (0D), first-derivative (1D), and second-derivative (2D) spectrophotometric measurement of NIZ in aqueous solution at the zero-crossing point of its sulfoxide derivative (at 314, 295-334, and 318-348 nm, respectively). Method B is a 1DD spectrophotometric method based on the simultaneous use of the first derivative of the ratio spectra and the measurement of peak amplitude at 297 nm. Method C uses a solvent-induced derivative-difference spectrophotometry with deltaD1 measurement from peak to peak at 315-345 nm. Method D involves quantitative densitometric evaluation of a mixture of the drug and its sulfoxide derivative after separation by high-performance thin-layer chromatography on silica gel plates with chloroform-methanol (9 + 1, v/v) as the mobile phase; Rf values for NIZ and its sulfoxide derivative were 0.4 and 0.2, respectively. The spot was scanned at 254 nm. The first-derivative spectrophotometric method was used to investigate the kinetics of the hydrogen peroxide degradation process at different temperatures. The apparent pseudo-first-order rate constant, half-life, and activation energy were calculated. The results obtained by the proposed methods were analyzed statistically and compared with those obtained by the official method. These methods are suitable as stability-indicating for the determination of NIZ in the presence of its oxidation-induced degradation product (sulfoxide derivative) either in the bulk powder or in pharmaceutical preparations. PMID:18376588

Youssef, Rasha M

244

Effect of Mobile Phase Additives on the Resolution of Four Bioactive Compounds by RP-HPLC  

PubMed Central

The use of mobile phase additives enhances the separation and resolution of the bioactive compounds on the C18 column. Chlorogenic acid, caffeic acid, rutin, and scoparone from Herba Artemisiae Scopariae were investigated as the target compounds. Acetic acid, triethylamine, inorganic salts, and several ionic liquids were added as mobile phase additives into methanol/water (40:60, v/v). The result revealed that a mobile phase with 0.01 mol/L of ionic liquid [BMIM][BF4] enabled the optimum separation of the four target compounds.

Li, Shengnan; Tian, Minglei; Row, Kyung Ho

2010-01-01

245

Determination of Montelukast Sodium and Bambuterol Hydrochloride in Tablets using RP HPLC  

PubMed Central

An accurate, specific and precise assay level gradient reverse-phase high-performance liquid chromatographic method was developed for simultaneous determination of montelukast sodium and bambuterol hydrochloride in tablet dosage form. An inertsil ODS C-18, 5 ?m column having 250×4.6 mm I.D. in gradient mode, with mobile phase A, containing 0.025 M sodium phosphate buffer: methanol (85:15) and mobile phase B, containing acetonitrile:methanol (85:15) was used at different time intervals. The flow rate was 1.5 ml/min and effluent was monitored at 218 nm. The retention times of montelukast sodium and bambuterol hydrochloride were 21.2 min and 5.8 min respectively. The linearity for both the drugs was in the range of 0.25-0.75 mg/ml with correlation coefficients of 0.9999 and 0.9996 for montelukast sodium and bambuterol hydrochloride, respectively.

Patil, Smita; Pore, Y. V.; Kuchekar, B. S.; Mane, Aruna; Khire, V. G.

2009-01-01

246

RP-HPLC Method Development and Its Validation for Quantitative Determination of Rimonabant in Human Plasma  

PubMed Central

A simple, accurate, and precise HPLC method was developed and validated for determination of rimonabant in human plasma. Following liquid-liquid extraction, chromatographic separation was accomplished using C18 column with mobile phase consisting of acetonitrile?:?water (90?:?10, v/v), drug was detected at 260?nm using UVdetector. The LOD and LOQ were 3.0 and 10.0??g/L, respectively. The method is linear in the interval 50.0–1000.0??g/L. The average extraction recovery of drug from plasma was found to be 92.2%. The percent CV of the method was found to be less than 10.8%, and accuracy was found between 94.5 and 106.7%. The assay may be applied to a pharmacokinetic and bioequivalence study of rimonabant.

Bankey, Shravan; Tapadiya, Ganesh; Lamale, Jasvant; Jain, Deepti; Saboo, Shweta; Khadabadi, S. S.

2012-01-01

247

A Sensitive RP-HPLC Method for Simultaneous Estimation of Diethylcarbamazine and Levocetirizine in Tablet Formulation  

PubMed Central

A simple, sensitive and reproducible method was developed and validated for the simultaneous estimation of diethylcarbamazine and levocetirizine in its tablet formulation by reverse phase high performance liquid chromatography using Waters1515 HPLC with UV detector at the ?max of 224 nm, using Princeton Sphere-100 C18 (250×4.6 mm. 5 ?) column. The mobile phase used was 20mM potassium dihydrogen orthophosphate buffer (pH: 3.2):acetonitrile (50:50 v/v) with isocratic flow (flow rate 1 ml/min) and the pH was adjusted with orthophosphoric acid. Losartan potassium was used as an internal standard. The compounds diethylcarbamazine, levocetirizine and losartan potassium were eluted at 2.12, 4.27 and 5.96 min, respectively. The peaks were eluted with better resolution. The method was accurate with assay values of 96.32 and 93.04% w/w, precise (%RSD) with intra-day 1.72 and 1.89 and inter-day 1.85 and 1.92, recoveries 102.86 and 101.1% w/w, which are very sensitive with limit of detections (LOD)'s 75, 50 ng/ml and limit of quantification (LOQ)'s 100, 75 ng/ml and linear with R2 values 0.994 in the range of 5 to 30 ?g/ml 0.1 to 1 ?g/ml for diethylcarbamazine and levocetirizine, respectively. Hence this method can be applied for quantification of different formulations containing diethylcarbamazine and levocetirizine simultaneously.

Reddy, J. Mahesh; Jeyaprakash, M. R.; Madhuri, K.; Meyyanathan, S. N.; Elango, K.

2011-01-01

248

Taxonomy of Australian Funnel-web spiders using rp-HPLC\\/ESI-MS profiling techniques  

Microsoft Academic Search

The complex nature of venom from spider species offers a unique natural source of potential pharmacological tools and therapeutic leads. The increased interest in spider venom molecules requires reproducible and precise identification methods. The current taxonomy of the Australian Funnel-web spiders is incomplete, and therefore, accurate identification of these spiders is difficult. Here, we present a study of venom from

David Wilson; Paul F. Alewood

2006-01-01

249

STRATEGIES FOR THE OPTIMUM SEPARATION OF GAMMA RADIOLYTIC DEGRADATION PRODUCTS OF METHOXYCHLOR USING RP-HPLC  

Microsoft Academic Search

Different types of reversed phase (RP) columns have been incorporated for the separation of gamma radiolytic degradation products (DPs) of methoxychlor. The effect of carbon chain length, carbon content, surface area, pore size, pore volume, and column dimensions of RP columns on DPs separation has also been investigated. The separation of DPs has been optimized employing methanol-water mobile phase and

S. Bilal Butt; M. Riaz

2012-01-01

250

RP-HPLC and Spectrophotometric Estimation of Ambroxol Hydrochloride and Cetirizine Hydrochloride in Combined Dosage Form  

PubMed Central

Rapid, precise, accurate, specific and sensitive reverse phase liquid chromatographic and absorbance ratio spectrophotometric methods have been developed for the simultaneous analysis of ambroxol hydrochloride and cetirizine hydrochloride in their tablet formulation. The chromatographic methods were standardized using a HIQ SIL-C18 column (250×4.6 mm i.d., 10 ?m particle size) with UV detection at 229 nm and mobile phase consisting of methanol-acetonitrile-water (40:40:20, v/v/v). Ambroxol hydrochloride and cetirizine hydrochloride have absorbance maxima at 243 nm and 229 nm, respectively. The isoabsorptive wavelength for both the drugs was 236 nm. For absorbance ratio method developed, wavelengths selected were 243 nm and 236 nm. The proposed methods were successfully applied to the determination of ambroxol hydrochloride and cetirizine hydrochloride in tablets, with high percentage of recovery, good accuracy and acceptable precision. Different analytical performance parameters such as linearity, precision, accuracy, limit of detection, limit of quantitation and robustness were determined according to International Conference on Harmonization ICH Q2B guidelines. Results of analysis of the developed method were compared by performing ANOVA.

Bhatia, Neela M.; Ganbavale, S. K.; Bhatia, M. S.; More, H. N.; Kokil, S. U.

2008-01-01

251

Quantitative Determination of Ciprofibrate in Tablets by Derivative UV Spectroscopy and RP-HPLC Method  

PubMed Central

A derivative UV spectrophotometric and a reversed phase high-performance liquid chromatographic method for the determination of ciprofibrate in tablets was developed. The first-order derivative UV spectrophotometric method was found to be accurate with 100.57±0.97 recovery and precise with a coefficient of variation of 1.44. These results were compared to those obtained by reference methods, zero-order UV spectrophotometric method and a reversed-phase high-performance liquid chromatography method. A reversed-phase C8 column with methanol:water (90:10, v/v, pH 3.7) mobile phase was used and the detector wavelength was set at 232 nm. Calibration solutions used in HPLC were ranging from 2 to 12 ?g/ml. An ANOVA test (P = 0.0226, F = 4.935) showed that the results obtained with the derivative UV spectrophotometric method were comparable to those obtained using reference methods.

Jain, P. S.; Jivani, H. N.; Khatal, R. N.; Surana, S. J.

2012-01-01

252

Determination of phenolic compounds in aromatic plants by RP-HPLC and GC-MS  

Microsoft Academic Search

It is well known that phenolic compounds are constituents of many plants and herbs, and they have attracted a great deal of public and scientific interest because of their health-promoting effects as antioxidants. Five plants, Vitex agnus-castus (Verbenaceae), Origanum dictamnus (Lamiaceae), Teucrium polium (Lamiaceae), Lavandula vera (Lamiaceae) and Lippia triphylla (Verbenaceae), were examined in order to determine their phenolic composition.

C. Proestos; D. Sereli; M. Komaitis

2006-01-01

253

[RP-HPLC method for determination of isorhynchophylline in plasma and its pharmacokinetics in rabbits].  

PubMed

A reversed phase HPLC method for determination of isorhnchophylline (IRHY) in rabbit plasma was developed. A Shimadzu LC-10A liquid chromatograph equipped with a Shimadzu SPD-10A multiwavelength detector and a Chromatopac LC-10A data processor were used. The analytical column was a 4.6 mm x 150 mm CLC-ODS. The mobile phase was a mixture of methanol-water (95:5), the flow rate was 1 ml.min-1. Detection was performed at UV 254 nm. The calibration curve was linear in the range from 0.016 to 16 micrograms.ml-1 with gamma = 0.9990. The lowest detection limit was 0.016 microgram.ml-1. The precision and accuracy of within-day and day-to-day ranged from 3.8% to 6.9%. The recoveries were 80.5% to 85.1%. The drug concentrtion-time curves of IRHY in rabbits after i.v. of 2 mg.kg-1 and 5 mg.kg-1 were shown to fit a two-compartment open model with half-times of 1.32 +/- 0.6 h and 1.25 +/- 0.09 h respectively. The absorption was fast after intraduodenal administration of IRHY (2 mg.kg-1 and 5 mg.kg-1) to rabbits with half-times of 1.75 +/- 0.18 h and 1.26 +/- 0.20 h, respectively. The bioavailability of IRHY was about 42.4% to 69.4%. The results showed that the method was simple and fast. The absorption and elimination were fast atfer intraduodenal administration or i.v. of IRHY to rabbits. PMID:11938934

Huang, B; Wu, Q; Lu, Y; Wen, G; Shi, J

1998-01-01

254

[Determination of steroidal saponins in Rhizoma paridis by RP-HPLC].  

PubMed

A reversed phase HPLC method for the separation and determination of nine steroidal saponins in Rhizoma paridis is described. The column was Symmetry C8, mobile phase was acetonitrile-water (42:58), UV detection was performed at 203 nm. The calibration curves showed good linearity over the range of 0.8-12.0 micrograms, gamma = 0.9996-0.9999, the recoveries were 97.1%-100.2% for the nine steroidal saponins. The method is simple, fast, sensitive and accurate and has been applied to the analysis of Rhizoma paridis. The results showed that the contents of the nine steroidal saponins in Rhizoma paridis were different with different sources. PMID:12016919

Wei, J

1998-06-01

255

RP-HPLC/pre-column derivatization for analysis of omeprazole, tinidazole, doxycycline and clarithromycin.  

PubMed

A validated, reliable and accurate reversed-phase high performance liquid chromatographic method using pre-column derivatization was adopted for the simultaneous determination of two ternary mixtures containing omeprazole, tinidazole and doxycycline hyclate or clarithromycin. Separation was achieved on a C18 column, through a gradient elution system using acetonitrile-methanol-water adjusted to pH = 6.60. Drugs were detected at 277 nm over concentration ranges of 1-112, 5-125, 2.5-550 and 2.5-100 µg/mL for omeprazole, tinidazole, doxycycline hyclate and clarithromycin, respectively. This is the first method that has isolated and identified clarithromycin derivative by infrared and mass spectroscopy. This method is the first study for the simultaneous determination of omeprazole, tinidazole, doxycycline hyclate and clarithromycin in combined mixtures and pharmaceutical formulations. PMID:23081968

Darwish, Khaled M; Salama, Ismail; Mostafa, Samia; El-Sadek, Mohamed

2012-10-18

256

Simultaneous determination of pyrimethamine, sulfadoxine, mefloquine, and ibuprofen in pharmaceutical formulations by RP-HPLC  

Microsoft Academic Search

A simple and rapid high-performance liquid chromatographic (HPLC) method for simultaneous determination and quantification\\u000a of pyramethamine, sulfadoxine, mefloquine HCl and ibuprofen was developed. The chromatographic system consisted of a Shimadzu\\u000a LC-10 AT VP pump, SPD-10 AV VP UV visible detector, and CBM-102 Bus Module integrator. Separation was achieved on a ?Bondapak\\u000a 125 A, C-18, 10-?m column at room temperature. The

M. Saeed Arayne; Najma Sultana; Farhan Ahmed Siddiqui; Sajida Naseem; Faiza Qureshi

2010-01-01

257

Increasing Proteome Coverage with Offline RP HPLC Coupled to Online RP NanoLC-MS  

PubMed Central

Fractionation prior to mass spectrometry is an indispensable step in proteomics. In this paper we report the success of performing offline reversed phase high pressure liquid chromatography (HPLC) fractionation on a C18 2.0 mm × 150 mm column at the peptide level with microliter per minute flow rates prior to online nano-flow reversed phase liquid chromatography mass spectrometry (nanoLC-MS) using the well-studied fungus Saccharomyces cerevisiae. A C18 75 µm × 150 mm column was used online and the online elution gradients for each fraction were adjusted in order to obtain well resolved separation. Comparing this method directly to only performing nanoLC-MS we observed a 61.6% increase in the number of identified proteins. At a 1% false discovery rate 1028 proteins were identified using two dimensions of RPLC versus 636 proteins identified in a single nano-flow separation. The majority of proteins identified by one dimension of nano-LC were present in the proteins identified in our two dimensional strategy. Although increasing analysis time, this non-orthogonal and facile pre-fractionation method affords a more comprehensive examination of the proteome.

Gokce, Emine; Andrews, Genna L.; Dean, Ralph A.; Muddiman, David C.

2013-01-01

258

RP-HPLC Method for the Determination of Losartan Potassium and Ramipril in Combined Dosage Form  

PubMed Central

A simple, specific and accurate reverse phase liquid chromatographic method was developed for the simultaneous determination of losartan potassium and ramipril in table dosage forms. A hypersil ODS C18, 4.6×250 mm, 5 ?m column in isocratic mode, with mobile phase acetonitrile:methanol:10 mM tetra butyl ammonium hydrogen sulphate in water in the ratio of 30:30:40% v/v/v was used. The flow rate was 1.0 ml/min and effluent was monitored at 210 nm. The retention times of losartan potassium and ramipril were 4.7 and 3.3 min, respectively. The linearity range for losartan potassium and ramipril were in the range of 0.04-100 ?g/ml and 0.2-300 ?g/ml, respectively. The proposed method was also validated and successfully applied to the estimation of losartan potassium and ramipril in combined tablet formulations.

Rao, K. Srinivasa; Srinivas, K.

2010-01-01

259

[Simultaneous determination of six alkaloids in Coptis chinensis of different regions by RP-HPLC].  

PubMed

A reversed-phase HPLC method for simultaneous determination of gatrorrhizine, columbamine, epiberberine, coptisine, palmatine and berberine in Coptis chinensis was developed. Analysis was carried out on an Xtimate C18 column (4.6 mm x 250 mm, 5 microm) eluted with acetonitrile-30 mmol x L(-1) ammonium bicarbonate solution (including 0.7% ammonia and 0.1% triethylamine) by gradient elution. The detective wavelength was 270 nm, the column temperature was 30 degrees C, and the flow rate was 1.0 mL x min(-1). By the above method, the linear ranges of gatrorrhizine, columbamine, epiberberine, coptisine, palmatine and berberine were 0.85-16.96 (r = 0.9997), 1.25-24.96 (r = 0.999 5), 2.05-40.96 (r = 0.999 9), 3.65-72.96 (r = 0.999 9), 2.88-57.60 (r = 0. 999 8),13.25-264.96 mg x L(-1) (r = 0.999 6), respectively. The average recoveries (n = 6) of the six alkaloids were 101.6% (RSD 1.3%),102.5% (RSD 1.5%), 100.8% (RSD 1.9%),102. 6% (RSD 1.2%), 97.80% (RSD 1.3%), 99.01% (RSD 1.5%), respectively. The determined results demonstrate that there is a significant difference in the contents of six alkaloids and total alkaloids among the tested samples. The method is accurate, reliable and repeatable for simultaneous determination of gatrorrhizine, columbamine, epiberberine, coptisine, palmatine and berberine in C. chinensis. PMID:21174768

Geng, Zhipeng; Zheng, Haijie; Zhang, Yi; Luo, Weizao; Qu, Xianyou

2010-10-01

260

Improved RP-HPLC Method for Analysis of Isoquinoline Alkaloids in Extracts of Chelidonium majus  

Microsoft Academic Search

A new high-performance liquid chromatographic method has been developed for analysis of isoquinoline alkaloids in extracts\\u000a of Chelidonium majus L. Samples were extracted with acidic methanol and the extracts were purified by solid-phase extraction on Supelclean LC-18\\u000a cartridges. Optimized conditions resulted in high recovery and reproducibility. Simultaneous determination of protopine, chelidonine,\\u000a coptisine, sanguinarine, and berberine was performed by HPLC on

L. Kursinszki; Á. Sárközi; Á. Kéry; É. Szöke

2006-01-01

261

Quantitative Determination of Ciprofibrate in Tablets by Derivative UV Spectroscopy and RP-HPLC Method.  

PubMed

A derivative UV spectrophotometric and a reversed phase high-performance liquid chromatographic method for the determination of ciprofibrate in tablets was developed. The first-order derivative UV spectrophotometric method was found to be accurate with 100.57±0.97 recovery and precise with a coefficient of variation of 1.44. These results were compared to those obtained by reference methods, zero-order UV spectrophotometric method and a reversed-phase high-performance liquid chromatography method. A reversed-phase C(8) column with methanol:water (90:10, v/v, pH 3.7) mobile phase was used and the detector wavelength was set at 232 nm. Calibration solutions used in HPLC were ranging from 2 to 12 ?g/ml. An ANOVA test (P = 0.0226, F = 4.935) showed that the results obtained with the derivative UV spectrophotometric method were comparable to those obtained using reference methods. PMID:23326000

Jain, P S; Jivani, H N; Khatal, R N; Surana, S J

2012-03-01

262

Simultaneous estimation of etoricoxib and thiocolchicoside by RP-HPLC method in combined dosage forms.  

PubMed

A simple, reproducible and efficient reverse phase high performance liquid chromatographic method was developed for simultaneous estimation of etoricoxib and thiocolchicoside in combined tablet dosage form. Formulation containing etoricoxib and thiocolchicoside is used as analgesic. Chromatography was performed on a 250 mm x 4.6 mm, 5-microm particle size, BDS Hypersil C-18 column with trifluoroacetic acid buffer (pH 2.6) and acetonitrile (75:25, v/v) as a mobile phase. The detection of the combined dosage form was carried out at 220 nm and a flow rate employed was 1.5 mL/min. The retention times were 6.6 and 3.1 min for etoricoxib and thiocolchicoside, respectively. Linearity was obtained in the concentration range 20 to 160 ppm for etoricoxib and in the range 2 to 16 ppm for thiocolchicoside with a correlation coefficient of 0.9918 and 0.9994, respectively. The results of the analysis were validated statistically and recovery studies confirmed the accuracy and precision of the proposed method. PMID:22125947

Kumar, Sanjiv; Joshi, Amit; Thakur, Rahul Singh; Pathak, Anupam K; Shah, Kamal

263

A new RP-HPLC method for analysis of meloxicam in tablets.  

PubMed

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination and quantification of meloxicam has been developed. The chromatographic system consisted of a Shimadzu LC-10 AT VP pump, SPD-10 AV VP UV/ visible detector, and a CBM-102 Bus Module integrator. Separation was achieved on the micro Bondapak 125 A C18 10 microm column at room temperature. The sample was introduced through an injector valve with a 10 microl sample loop. Methanol:water (70:30 v/v) was used as mobile phase, with flow rate 2 ml/minutes. pH was adjusted to 2.6 with phosphoric acid. U.V detection was performed at 230 nm. The results obtained showed a good agreement with the declared content. Recovery values of meloxicam in tablets (in Melfax 15 mg tablets) were from 99.27 % to 100.06 %. Piroxicam was used as an internal standard. The proposed method is rapid, accurate and selective; it may be used for the quantitative analysis of meloxicam from raw materials, in bulk drugs and other dosage formulations. PMID:16431386

Arayne, M Saeed; Sultana, Najma; Siddiqui, Farhan Ahmed

2005-01-01

264

A Sensitive RP-HPLC Method for Simultaneous Estimation of Diethylcarbamazine and Levocetirizine in Tablet Formulation.  

PubMed

A simple, sensitive and reproducible method was developed and validated for the simultaneous estimation of diethylcarbamazine and levocetirizine in its tablet formulation by reverse phase high performance liquid chromatography using Waters1515 HPLC with UV detector at the ?(max) of 224 nm, using Princeton Sphere-100 C(18) (250×4.6 mm. 5 ?) column. The mobile phase used was 20mM potassium dihydrogen orthophosphate buffer (pH: 3.2):acetonitrile (50:50 v/v) with isocratic flow (flow rate 1 ml/min) and the pH was adjusted with orthophosphoric acid. Losartan potassium was used as an internal standard. The compounds diethylcarbamazine, levocetirizine and losartan potassium were eluted at 2.12, 4.27 and 5.96 min, respectively. The peaks were eluted with better resolution. The method was accurate with assay values of 96.32 and 93.04% w/w, precise (%RSD) with intra-day 1.72 and 1.89 and inter-day 1.85 and 1.92, recoveries 102.86 and 101.1% w/w, which are very sensitive with limit of detections (LOD)'s 75, 50 ng/ml and limit of quantification (LOQ)'s 100, 75 ng/ml and linear with R(2) values 0.994 in the range of 5 to 30 ?g/ml 0.1 to 1 ?g/ml for diethylcarbamazine and levocetirizine, respectively. Hence this method can be applied for quantification of different formulations containing diethylcarbamazine and levocetirizine simultaneously. PMID:22457560

Reddy, J Mahesh; Jeyaprakash, M R; Madhuri, K; Meyyanathan, S N; Elango, K

2011-05-01

265

Reduction of indicator and pathogenic microorganisms in pig manure through fly ash and lime addition during alkaline stabilization  

Microsoft Academic Search

A pilot scale study was conducted to evaluate the effect of lime and alkaline coal fly ash (CFA) on the reduction of pathogens in pig manure during alkaline stabilization and suppression of re-growth during post-stabilization incubation. Pig manure was mixed with CFA at 25%, 33% and 50%, and a control without fly ash was maintained. To these manure–ash mixtures, lime

Jonathan W. C. Wong; Ammaiyappan Selvam

2009-01-01

266

Determination of the weakest branch in a radial distribution network using local voltage stability indicator at the proximity of the voltage collapse point  

Microsoft Academic Search

This paper presents a unique method to determine the weakest branch or the overstressed branch in a distribution network. This radial feature of the network has been fully exploited to establish the concept of local voltage stability indicator in terms of reactive power. The effectiveness of the proposed method has been successfully tested in 12 bus radial distribution system and

Sumit Banerjee; C. K. Chanda; S. C. Konar

2009-01-01

267

Sunlight Inactivation of Fecal Indicator Bacteria and Bacteriophages from Waste Stabilization Pond Effluent in Fresh and Saline Waters  

Microsoft Academic Search

Sunlight inactivation in fresh (river) water of fecal coliforms, enterococci, Escherichia coli, somatic coli- phages, and F-RNA phages from waste stabilization pond (WSP) effluent was compared. Ten experiments were conducted outdoors in 300-liter chambers, held at 14°C (mean river water temperature). Sunlight inactivation (kS) rates, as a function of cumulative global solar radiation (insolation), were all more than 10 times

Lester W. Sinton; Carollyn H. Hall; Philippa A. Lynch; Robert J. Davies-Colley

2002-01-01

268

Anthropometric parameters as indicators of metabolic derangements in schizophrenia patients stabilized on olanzapine in an Indian rural population  

PubMed Central

Context: For any given body mass, Asian Indians have higher central obesity than Europeans. A periodic measurement of body mass index (BMI) and waist hip ratio (WHR) is practically more feasible than other parameters of metabolic syndrome by repeated blood collection. However, few studies are available on the relative importance of BMI and WHR as markers of dyslipidemia and insulin resistance in schizophrenia patients stabilized on second generation antipsychotics in Indian population. Aim: We conducted the present study on such patients to examine whether BMI or WHR can better predict dyslipidemia and insulin resistance in these patients in a rural area. Settings and Design: The study was a hospital based case control study under rural settings on 38 schizophrenia patients stabilized on olanzapine and 30 matched controls. Materials and Methods: Fasting concentrations of blood glucose, lipid parameters and serum insulin were assessed. Data for Homeostatic model for assessment of insulin resistance (HOMA-IR), BMI, and WHR were obtained to assess the insulin resistance, overall body fat distribution and abdominal fat dispensation respectively. Statistical analysis used: ‘t’ test was performed to assay any difference in corresponding mean values between cases and controls. Dependence of HOMA-IR on key parameters was assessed by analysis of co-variance (ANCOVA) study. Results: Cases exhibited significantly higher values for HOMA-IR, serum triglyceride and low density lipoprotein cholesterol (LDLc) with a significantly lower high density lipoprotein cholesterol (HDLc) level. ANCOVA study reflected that irrespective of age and sex, HOMA-IR was dependent on serum triglyceride level and WHR (F=8.3 and 5.7 respectively, P<0.05), but not on BMI (F<0.001, P=0.997). Conclusions: Central obesity could be more closely associated with the pathogenesis of prediabetic state in our case group. So, WHR is a better anthropometric parameter than BMI for an early assessment of insulin resistance and dyslipidemia in schizophrenia patients stabilized on olanzapine in our region.

Rout, Jayanta Kumar; Dasgupta, Anindya; Singh, Om Prakash; Banerjee, Ushasi; Das, Brahmarshi

2012-01-01

269

Development and validation of a stability indicating HPLC method for simultaneous determination of four novel fluoroquinolone dimers as potential antibacterial agents.  

PubMed

A series of novel 6-fluoro1,4-dihydro-4-oxo-3-quinoline carboxylic acid dimers were synthesized as potential antibacterial agents from commercially available substituted fluorobenzoic acids. A stability indicating HPLC method was developed to determine these novel fluoroquinolone dimers using a systematic method development approach. Samples were subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation; and analyzed to demonstrate the specificity and stability indicating ability of the developed method. The precision for all four fluoroquinolone dimers was within 2.0% RSD. Calibration curves were linear (LOQ, 150%), with regression coefficients >0.99 for all dimers. The method was conveniently applied for determining purity and assay of these four novel fluoroquinolone dimers. PMID:22030076

Khan, Muzaffar; Reddy, C Naveen Kumar; Ravindra, G; Reddy, K V S R Krishna; Dubey, P K

2011-10-04

270

Validation of HPLC stability-indicating method for Vitamin C in semisolid pharmaceutical\\/cosmetic preparations with glutathione and sodium metabisulfite, as antioxidants  

Microsoft Academic Search

HPLC stability-indicating method was validated for Vitamin C (ascorbic acid) in semisolid pharmaceutical\\/cosmetic formulations containing glutathione and sodium metabisulfite, as antioxidants. The described procedure included a reliable, precise, accurate and specific method determination employing a 250mm×4.6mm C18 column, 0.2% metaphosphoric acid\\/methanol\\/acetonitrile (90:8:2, v\\/v\\/v) as the mobile phase and detection at 254nm. Nicotinic and ascorbic acids were employed as standards, both

Adriana M. Maia; André Rolim Baby; Wilson J. Yasaka; Eunice Suenaga; Telma M. Kaneko; Maria Valéria R. Velasco

2007-01-01

271

DEVELOPMENT OF STABILITY-INDICATING UPLC METHOD FOR DETERMINING ZOLPIDEM TARTRATE AND ITS PRODUCT RELATED VARIANTS IN DRUG SUBSTANCE AND DRUG PRODUCTS  

Microsoft Academic Search

A stability indicating UPLC method was developed for the quantitative determination of Zolpidem Tartrate (ZT) and its product related variants present in drug substance and drug products. The liquid chromatographic separation was achieved on Acquity UPLC HSS T3-C18 column. All the eight potential variants and the drug were eluted within 8 minutes. A narrow range pH gradient, in combination with

M. Vishnu Murthy; Ch. Krishnaiah; Ramesh Kumar; K. Mukkanti

2012-01-01

272

A SINGLE COMMON STABILITY INDICATING ULTRA-PERFORMANCE LIQUID CHROMATOGRAPHIC METHOD FOR ESTIMATION OF IMPURITIES IN FOUR ANGIOTENSIN II RECEPTOR BLOCKERS  

Microsoft Academic Search

A novel single common stability-indicating gradient reverse phase ultra-performance liquid chromatographic (RP-UPLC) method was developed for the determination of purity of four angiotensin II receptor blockers namely valsartan, losartan potassium, irbesartan, and telmisartan from respective finished dosage forms in the presence of their impurities and forced degradation products. The method was developed using Waters Aquity BEH C18 column with mobile

Dantu Durga Rao; Galla Vamsi Krishna; A. Malleswara Reddy; L. Kalyanaraman; K. Kyas

2012-01-01

273

The ICH guidance in practice: stress degradation studies on indinavir sulphate and development of a validated specific stability-indicating HPTLC assay method  

Microsoft Academic Search

A sensitive, selective, precise and stability-indicating high-performance thin layer chromatography (HPTLC) method for analysis of indinavir sulphate both as a bulk drug and in formulations was developed and validated. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of carbon tetrachloride\\/chloroform\\/methanol\\/10% v\\/v ammonia (4:4.5:1.5:0.05, v\\/v\\/v\\/v). Densitometric analysis of indinavir sulphate

Neeraj Kaul; Himani Agrawal; A. R. Paradkar; K. R. Mahadik

2004-01-01

274

Foot Rotation Indicator (FRI) Point: A New Gait Planning Tool to Evaluate Postural Stability of Biped Robots  

Microsoft Academic Search

The focus of this paper is the problem of foot rotationin biped robots during the single support phase. Footrotation is an indication of postural instability andshould be carefully treated in a dynamically stablewalk and avoided altogether in a statically stable walk.We introduce the foot rotation indicator (FRI)point which is a point on the foot\\/ground contact surfacewhere the net ground reaction

Ambarish Goswami

1999-01-01

275

The Stability of Rankings Derived from Composite Indicators: Analysis of the "IL Sole 24 Ore" Quality of Life Report  

ERIC Educational Resources Information Center

|The calculation of composite indicators and the derivation of respective rankings is a common method used to benchmark countries or regions. However, although the statistical robustness of these rankings is often criticised, they often still spark off heated political debate. Here, we assess the sensitivity of the province ranking published by…

Lun, G.; Holzer, D.; Tappeiner, G.; Tappeiner, U.

2006-01-01

276

Microwave heating of different commercial categories of olive oil: Part I. Effect on chemical oxidative stability indices and phenolic compounds  

Microsoft Academic Search

The effect of microwave heating of extra virgin olive oil (EVOo), olive oil (Oo) and pomace olive oil (Po) in domestic appliances, was investigated in terms of chemical oxidative indices (peroxide, p-anisidine and Totox values), free acidity, water content, total phenol content and different classes of phenolic compounds.Water content of unheated EVOo was higher as compared to the other two

Lorenzo Cerretani; Alessandra Bendini; Maria Teresa Rodriguez-Estrada; Elena Vittadini; Emma Chiavaro

2009-01-01

277

Stability-indicating TLC-densitometric method for simultaneous determination of paracetamol and chlorzoxazone and their toxic impurities.  

PubMed

A highly sensitive, selective and accurate thin-layer chromatographic (TLC)-densitometric method has been developed and validated for the simultaneous determination of paracetamol (PAR) and chlorzoxazone (CZ) and their toxic impurities, 4-amino phenol (4AP) and 2-amino-4-chlorophenol (2ACP), respectively, which are also considered to be the hydrolytic degradation products and related substances of the studied drugs. A developing system consisting of chloroform-methanol-glacial acetic acid (9.5:0.5:0.25, by volume) was found to be sufficient for chromatographic separation among the four studied components using pre-activated silica gel 60 F254 TLC plates with ultraviolet detection at 225 nm. Calibration curves were constructed in the ranges of 0.3-3, 1-10, 0.06-3 and 0.04-3 µg/band for PAR, CZ, 4AP and 2ACP, respectively, using polynomial equations. The developed method was validated according to International Conference on Harmonization guidelines and demonstrated good accuracy and precision. Moreover, the method was successfully applied for the determination of PAR and CZ in different marketed samples and the results were statistically compared to those obtained by the reported reversed-phase high-performance liquid chromatography method using F-test and Student's-t test. The low detection and quantitation limits of the developed method make it suitable for quality control and stability studies of PAR and CZ in different pharmaceutical formulations. PMID:22843763

Abdelaleem, Eglal A; Abdelwahab, Nada S

2012-07-26

278

Stability-indicating micelle-enhanced spectrofluorimetric method for determination of loratadine and desloratadine in dosage forms.  

PubMed

A highly sensitive and simple spectrofluorimetric method was developed for the determination of loratadine (LRT) and desloratadine (DSL) in their pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behaviour of LRT and DSL in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer of pH 4.5, the fluorescence intensities of both LRT and DSL were greatly enhanced (240%) in the presence of SDS. The fluorescence intensity was measured at 438 nm after excitation at 290 nm for both drugs. The fluorescence-concentration plots were rectilinear over the range 0.05-2.0 µg/mL for both LRT and DSL, with lower detection limits of 5.13 × 10(-3) and 6.35 × 10(-3) µg/mL for LRT and DSL, respectively. The method was successfully applied to the analysis of the two drugs in their commercial tablets, capsules and syrups, and the results were in good agreement with those obtained with the official or comparison methods. The proposed method is specific for the determination of LRT in the presence of other co-formulated drugs, such as pseudoephedrine. The application of the proposed method was extended to stability studies of LRT and DSL after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines. PMID:21491578

Walash, M I; Belal, F; El-Enany, N; Eid, M; El-Shaheny, R N

2011-04-13

279

Stability-indicating spectrophotometric methods for determination of tazarotene in the presence of its alkaline degradation product by derivative spectrophotometric techniques.  

PubMed

The stability of tazarotene (TZ) was investigated and two stability-indicating methods-namely, first derivative and a derivative ratio spectrophotometric method-were used to determine tazarotene in the presence of its alkaline degradation product (HD) using methanol as a solvent. A linear relationship was obtained in the range 1-10 µg ml?¹ for both methods. By applying the proposed methods, it was possible to determine tazarotene in its pure powdered from with accuracy 99.35 ± 1.410 (n = 10) for the first derivative method and 99.45 ± 1.053 (n = 10) for the derivative ratio method. First derivative and derivative ratio methods were used for the analysis of laboratory-prepared mixtures containing different ratios of tazarotene and its degradation product and they were valid in the presence of up to 70% and 80% degradation product, respectively. The proposed methods were validated and found to be suitable as stability-indicating assay methods for tazarotene in pharmaceutical formulations. PMID:20878894

Badawy, Amr M; El-Alim, Abd El-Aziz B Abd; Saad, Ahmed S

2010-03-01

280

Effects of (-)-OSU6162 and ACR16 on motor activity in rats, indicating a unique mechanism of dopaminergic stabilization.  

PubMed

Dopaminergic stabilizers can be defined as drugs that stimulate or inhibit dopaminergic signalling depending on the dopaminergic tone. (-)-OSU6162 and ACR16 appear to possess such a profile. They have been proposed to act as partial dopamine receptor agonists or as antagonists with preferential action on dopaminergic autoreceptors. Previous studies have shown either stimulation or inhibition of behaviour in response to (-)-OSU6162 and ACR16, which has been suggested to reflect their dual effects on dopaminergic signalling. The aims of the present work are to (1) examine the relation between behavioural response to these drugs and activity baseline, and (2) test the suggested mechanisms of action by means of close comparisons with the known partial D2-receptor agonists (-)-3-PPP and aripiprazole, and the D2 autoreceptor preferring antagonist amisulpride with respect to effects on behaviour. From the results of these experiments it can be concluded that: (1) The direction of the response to (-)-OSU6162 and ACR16 is dependent on activity baseline, which in turn, under physiological conditions, is determined primarily by test arena size of and degree of habituation to the environment. (2) The effects of (-)-OSU6162 and ACR16 cannot be explained on the basis of either partial dopamine receptor agonism or preferential dopamine autoreceptor antagonism. Nevertheless, the current data suggest at least two different D2-receptor-associated targets which mediate opposite effects on activity. This result fits in with a mechanism proposed from a recent in vitro study, according to which (-)-OSU6162 has a dual action on dopamine D2 receptors, (a) an allosteric effect causing an enhanced response to dopamine, and (b) the previously proposed orthosteric effect antagonizing the action of dopamine. PMID:18351286

Rung, Johan P; Rung, Emilia; Helgeson, Lisa; Johansson, Anette M; Svensson, Kjell; Carlsson, Arvid; Carlsson, Maria L

2008-03-20

281

Validated stability-indicating methods for determination of cilostazol in the presence of its degradation products according to the ICH guidelines.  

PubMed

Sensitive and selective stability-indicating assay methods (SIAMs) are suggested for the determination of cilostazol (CIL) in the presence of its acid, alkaline and oxidative degradation products. Developing SIAMs is necessary to carry out any stability study. Stress testing of CIL was performed according to the International Conference on Harmonization (ICH) guidelines in order to validate the stability-indicating power of the analytical procedures. Stress testing showed that CIL underwent acid, alkaline and oxidative degradation; on the other hand, it showed stability towards photo- and thermal degradation. Two chromatographic SIAMs were developed, namely HPLC and HPTLC methods. The concentration range and the mean percentage recovery were 1.0-31.0 microg/ml and 99.96+/-0.46 and 0.6-14.0 microg/spot and 99.88+/-1.10 for HPLC and HPTLC methods, respectively. In addition, derivative spectrophotometric methods were developed in order to determine CIL in the presence of its acid degradation product; these were performed by using the third derivative spectra (3D) and the first derivative of the ratio spectra (1DD) methods. The linearity range and the mean percentage recovery were 2.0-34.0 microg/ml and 100.27+/-1.20 for the (3D) method, while they were 2.0-30.0 microg/ml and 99.94+/-1.18 for the (1DD) method. Also, two chemometric-assisted spectrophotometric methods, based on using partial least squares (PLS) and concentration residual augmented classical least squares method (CRACLS), for the determination of CIL were developed. Both methods were applied on zero order spectra of the mixtures of CIL and its acid degradation product, the mean percentage recovery was 100.03+/-1.09 and 99.91+/-1.27 for PLS and CRACLS, respectively. All methods were validated according to the International Conference on Harmonization (ICH) guidelines and applied on bulk powder and pharmaceutical formulations. PMID:17719736

Fayed, Ahmad S; Shehata, Mostafa A; Ashour, Ahmed; Hassan, Nagiba Y; Weshahy, Soheir A

2007-07-10

282

Chromosome stability in tonsillar squamous cell carcinoma is associated with HPV16 integration and indicates a favorable prognosis.  

PubMed

Tonsillar squamous cell carcinoma (TSCC) is frequently associated with human papillomavirus (HPV) and chromosome instability. Data from cellular model systems are, however, controversial concerning a relation between HPV and chromosome instability development. Here we studied this association in 77 primary TSCC with known clinical outcome and cell cycle protein expression profiles. Thirty-two tumors (42%) showed HPV16-integration. All 77 cases were analyzed by fluorescence in situ hybridization using chromosome 1- and 7-specific centromere DNA probes to detect chromosome instability, indicated by the presence of chromosome imbalances and/or polyploidization for these chromosomes. In addition, eight HPV-positive dysplasias, seven of which were adjacent to a carcinoma, were analyzed. Disomy for chromosome 1 and 7 was present in 29 out of 77 TSCC (38%), of which 19 were HPV16-positive (p = 0.002). Aneusomy was observed in the remaining 48 TSCC, of which 13 were HPV-positive. Aneusomies correlated significantly with tobacco- and alcohol consumption (p = 0.001 and p = 0.016, respectively) and a higher T-stage (p = 0.018). Both HPV-positivity and chromosome disomy were significantly associated with a favorable disease-free survival (p = 0.001 and p = 0.025, respectively). Particularly in the HPV16-positive group chromosome instability is a very strong indicator for an unfavorable prognosis (p = 0.032). In the dysplasias an identical HPV and chromosome copy number status was identified as in the adjacent tumors. We conclude that HPV-positive TSCC and their precursor lesions are more often genetically stable than HPV-negative lesions and that these tumors are associated with a favorable prognosis. Chromosome instability is an indicator for unfavorable prognosis, particularly in the HPV-positive patient group. PMID:22987500

Mooren, Jeroen J; Kremer, Bernd; Claessen, Sandra M H; Voogd, Adri C; Bot, Fredrik J; Peter Klussmann, J; Huebbers, Christian U; Hopman, Anton H N; Ramaekers, Frans C S; Speel, Ernst-Jan M

2012-10-11

283

Stability-indicating high-performance liquid chromatographic assay and analysis of decomposition products of 2-[4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid.  

PubMed

A stability-indicating HPLC assay has been developed for 2-[4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid (XK469). XK-469 is the 7-chloro analog of herbicide Quizalofop and is currently under development as an antineoplastic agent. HPLC separation of XK469 is achieved with an ODS column using isocratic elution of an aqueous MeOH mobile phase. The assay is reproducible (RSD=0.9%), linear (r2=0.999), accurate (error=1.2%) and sensitive (LDL=1.2 ng). The HPLC separates XK469 from its forced decomposition products. Identities of the decomposition products have been elucidated. PMID:10722075

Cheung, A P; Struble, E; Nguyen, N; Liu, P

2000-02-18

284

Stress Degradation Behavior of Abacavir Sulfate and Development of a Suitable Stability-Indicating UHPLC Method for the Determination of Abacavir, its Related Substances, and Degradation Products  

PubMed Central

A novel, stability-indicating UHPLC method was developed for the quantitative determination of Abacavir sulfate, its related substances, and forced degradation impurities in bulk drugs. The chromatographic separation was achieved on a Waters Acquity BEH C8, 50 mm × 2.1 mm, 1.7 ?m particle size column with a mobile containing a gradient mixture of solution A (0.10 % v/v o-phosphoric acid in water) and solution B (0.10% v/v o-phosphoric acid in methanol). The flow rate was set at 0.40 mL/min and the run time was 6.0 min. The drug substance was subjected to the stress studies of hydrolysis, oxidation, photolysis, and thermal degradation. Abacavir sulfate was found to degrade significantly under acidic hydrolysis and oxidative stress conditions. The formed degradation products were reported and were well-resolved from Abacavir and its related substances. The mass balance was found to be satisfactory in all of the stress conditions, thus proving the stability-indicating capability of the method. The developed UHPLC method was validated to be in agreement with ICH requirements and found to be rapid, accurate, precise, linear, specific, and suitable for the quantitative determination of related substances and degradants in the bulk drug samples of Abacavir sulfate.

Vukkum, Pallavi; Deshpande, Girish R.; Babu, J. Moses; Muralikrishna, R.; Jagu, Pavani

2012-01-01

285

Nifedipine-loaded polymeric nanocapsules: validation of a stability-indicating HPLC method to evaluate the drug entrapment efficiency and in vitro release profiles.  

PubMed

A simple stability-indicating analytical method was developed and validated to quantify nifedipine in polymeric nanocapsule suspensions; an in vitro drug release study was then carried out. The analysis was performed using an RP C18 column, UV-Vis detection at 262 nm, and methanol-water (70 + 30, v/v) mobile phase at a flow rate of 1.2 mL/min. The method was validated in terms of specificity, linearity and range, LOQ, accuracy, precision, and robustness. The results obtained were within the acceptable ranges. The nanocapsules, made of poly(epsilon-caprolactone), were prepared by the solvent displacement technique and showed high entrapment efficiency. The entrapment efficiency was 97.6 and 98.2% for the nifedipine-loaded polymeric nanocapsules prepared from polyvinyl alcohol (PVA) and Pluronic F68 (PF68), respectively. The particle size and zeta potential of nanocapsules were found to be influenced by the nature of the stabilizer used. The mean diameter and zeta potential for nanocapsules with PVA and PF68 were 290.9 and 179.9 nm, and -17.7 mV and -32.7 mV, respectively. The two formulations prepared showed a drug release of up to 70% over 4 days. This behavior indicates the viability of this drug delivery system for use as a controlled-release system. PMID:23767350

Granada, Andréa; Tagliari, Monika Piazzon; Soldi, Valdir; Silva, Marcos António Segatto; Zanetti-Ramos, Betina Ghiel; Fernandes, Daniel; Stulzer, Hellen Karine

286

A Rapid, Stability Indicating RP-UPLC Method for Simultaneous Determination of Ambroxol Hydrochloride, Cetirizine Hydrochloride and Antimicrobial Preservatives in Liquid Pharmaceutical Formulation  

PubMed Central

A stability indicating reversed phase ultra performance liquid chromatography (RP-UPLC) method was developed for simultaneous determination of ambroxol hydrochloride (AMB), cetirizine hydrochloride (CTZ), methylparaben (MP) and propylparaben (PP) in liquid pharmaceutical formulation. The desired chromatographic separation was achieved on an Agilent Eclipse plus C18, 1.8 ?m (50 × 2.1 mm) column using gradient elution at 237 nm detector wavelength. The optimized mobile phase consists of a mixture of 0.01 M phosphate buffer and 0.1 % triethylamine as a solvent-A and acetonitrile as a solvent-B. The developed method separates AMB, CTZ, MP and PP in presence of twelve known impurities/degradation products and one unknown degradation product within 3.5 min. Stability indicating capability was established by forced degradation experiments and seperation of known and unknown degradation products. The lower limit of quantification was established for AMB, CTZ, MP and PP. The developed RP-UPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated method is applied for simultaneous estimation of AMB, CTZ, MP and PP in commercially available syrup samples. Further, the method can be extended for estimation of AMB, CTZ, MP, PP and levo-cetirizine (LCTZ) in various commercially available dosage forms.

Trivedi, Rakshit Kanubhai; Patel, Mukesh C.; Jadhav, Sushant B.

2011-01-01

287

Development and Validation of a Stability-Indicating RP-UPLC Method for Determination of Rosuvastatin and Related Substances in Pharmaceutical Dosage Form  

PubMed Central

A stability-indicating reversed phase ultra performance liquid chromatographic (RP-UPLC) method was developed for the determination of related substances in rosuvastatin calcium (ROSV) tablet dosage form. The chromatographic separation was achieved on an Acquity BEH C18 (100 mm × 2.1 mm, 1.7 ?m) column with mobile phase containing a gradient mixture of solvent-A (0.1% trifluoroacetic acid) and solvent-B (methanol). The eluted compounds were monitored at 240 nm and the run time was 10.0 min. Degradation behavior of the ROSV was studied under various degradation stress conditions. Four major unknown degradation products (late eluting impurities) were found in acid stress condition and two unknown degradation products were found in oxidative stress condition. The developed method separates (six) unknown impurities, (three) known impurities and ROSV substance from each other, providing the stability-indicating power of the method. The developed RP-UPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. The developed and validated RP-UPLC method is LC-MS compatible and can be applied for identification of eluted unknown impurities of ROSV.

Trivedi, Harshal Kanubhai; Patel, Mukesh C.

2012-01-01

288

A validated stability-indicating normal phase LC method for clopidogrel bisulfate and its impurities in bulk drug and pharmaceutical dosage form.  

PubMed

A novel stability-indicating normal phase liquid chromatographic (NP-LC) method was developed for the determination of purity of clopidogrel drug substance and drug products in bulk samples and pharmaceutical dosage forms in the presence of its impurities and degradation products. This method is capable of separating all the related substances of clopidogrel along with the chiral impurities. This method can be also be used for the estimation of assay of clopidogrel in drug substance as well as in drug product. The method was developed using Chiralcel OJ-H (250mmx4.6mm, 5microm) column. n-Hexane, ethanol and diethyl amine in 95:5:0.05 (v/v/v) ratio was used as a mobile phase. The eluted compounds were monitored at 240nm. Clopidogrel bisulfate was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. The degradation products were well resolved from main peak and its impurities, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, limit of detection, limit of quantification, precision, linearity, accuracy, robustness and system suitability. PMID:20074888

Durga Rao, Dantu; Kalyanaraman, L; Sait, Shakil S; Venkata Rao, P

2009-12-28

289

A New Rapid and Sensitive Stability-Indicating UPLC Assay Method for Tolterodine Tartrate: Application in Pharmaceuticals, Human Plasma and Urine Samples  

PubMed Central

A new rapid, simple, sensitive, selective and accurate reversed-phase stability-indicating Ultra Performance Liquid Chromatography (RP-UPLC) technique was developed for the assay of Tolterodine Tartrate in pharmaceutical dosage form, human plasma and urine samples. The developed UPLC method is superior in technology to conventional HPLC with respect to speed, solvent consumption, resolution and cost of analysis. Chromatographic run time was 6 min in reversed-phase mode and ultraviolet detection was carried out at 220 nm for quantification. Efficient separation was achieved for all the degradants of Tolterodine Tartrate on BEH C18 sub-2-?m Acquity UPLC column using Trifluoroacetic acid and acetonitrile as organic solvent in a linear gradient program. The active pharmaceutical ingredient was extracted from tablet dosage form using a mixture of acetonitrile and water as diluent. The calibration graphs were linear and the method showed excellent recoveries for bulk and tablet dosage form. The test solution was found to be stable for 40 days when stored in the refrigerator between 2 and 8 °C. The developed UPLC method was validated and meets the requirements delineated by the International Conference on Harmonization (ICH) guidelines with respect to linearity, accuracy, precision, specificity and robustness. The intra-day and inter-day variation was found be less than 1%. The method was reproducible and selective for the estimation of Tolterodine Tartrate. Because the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating one.

Yanamandra, Ramesh; Vadla, Chandra Sekhar; Puppala, Umamaheshwar; Patro, Balaram; Murthy, Yellajyosula. L. N.; Ramaiah, Parimi Atchuta

2012-01-01

290

Validation of a Stability-Indicating Hydrophilic Interaction Liquid Chromatographic Method for the Quantitative Determination of Vitamin K3 (Menadione Sodium Bisulfite) in Injectable Solution Formulation  

PubMed Central

A simple, specific, accurate, and stability-indicating method was developed and validated for the quantitative determination of menadione sodium bisulfite in the injectable solution formulation. The method is based on zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) coupled with a photodiode array detector. The desired separation was achieved on the ZIC-HILIC column (250 mm × 4.6 mm, 5 ?m) at 25°C temperature. The optimized mobile phase consisted of an isocratic solvent mixture of 200mM ammonium acetate (NH4AC) solution and acetonitrile (ACN) (20:80; v/v) pH-adjusted to 5.7 by glacial acetic acid. The mobile phase was fixed at 0.5 ml/min and the analytes were monitored at 261 nm using a photodiode array detector. The effects of the chromatographic conditions on the peak retention, peak USP tailing factor, and column efficiency were systematically optimized. Forced degradation experiments were carried out by exposing menadione sodium bisulfite standard and the injectable solution formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The degradation products were well-resolved from the main peak and the excipients, thus proving that the method is a reliable, stability-indicating tool. The method was validated as per ICH and USP guidelines (USP34/NF29) and found to be adequate for the routine quantitative estimation of menadione sodium bisulfite in commercially available menadione sodium bisulfite injectable solution dosage forms.

Ghanem, Mashhour M.; Abu-Lafi, Saleh A.; Hallak, Hussein O.

2013-01-01

291

Is there any association between imidapril hydrochloride stability profile under dry air conditions and cancer initiation?  

PubMed

Stability study for imidapril hydrochloride (IMD) was performed under stress conditions of increased temperature (T=373K) and decreased relative air humidity (RH=0%) in order to obtain and identify its degradation product. The degradation sample stored for 15 days under the above environmental conditions was analyzed by LC-MS technique and it was found that the only degradation impurity formed in the course of the investigated drug degradation was IMD diketopiperazine derivative (DKP) which was produced by dehydration and intramolecular cyclization. The kinetics of its formation was analyzed by a revalidated RP-HPLC method and the kinetic model of this reaction was established. It was concluded that the DKP formation follows Prout-Tompkins kinetics with the rate constant k±?k=2.034±0.157×10(-6) [s(-1)]. The obtained degradation impurity was further assessed with respect to its mutagenic potential using commercial Ames MPF 98/100 microplate format mutagenicity assay kit equipped with Salmonella typhimurium strains TA 98 and TA 100. Both strains were exposed to six concentrations (in a range of 0.16-5.0mg/mL) of DKP in the presence and absence of metabolic activation system. No mutagenic effect was observed confirming that the presence of DKP in IMD final dosage form has no impact on cancer initiation. PMID:24021249

Regulska, Katarzyna; Murias, Marek; Stanisz, Beata; Regulski, Mi?osz

2013-09-08

292

Plasma-based sterilization: effect on surface and bulk properties and hydrolytic stability of reprocessed polyurethane electrophysiology catheters.  

PubMed

Plasma-based sterilization is a promising alternative to ethylene oxide (EO) for reprocessing of electrophysiology catheters. To assess its safety in terms of material damage, modifications of surface and bulk properties as well as hydrolytic stability of sterilized catheters were evaluated. Polyurethane (PU) single-use electrophysiology catheters were subjected to one, five, and ten sterilization cycles by Sterrad-100S and Plazlyte, as well as by pure EO for comparison. Surface analysis techniques (ATR-FTIR, XPS, DCA) showed oxidation limited to the near-surface layer induced by both plasma-based sterilizers, whereas EO induced slight but deeper alkylation. Using bulk analysis techniques (RP-HPLC, SEC), oligomer alteration was observed after all three sterilization techniques, without modification of molecular weights. Hydrolytic stability of catheters was slightly changed by plasma-based sterilization, with a small increase in released oligomers. Finally, although Plazlyte and Sterrad are both plasma-based techniques, they induced different impacts on catheters, such as the degradation of an additive with Sterrad, and a clear difference in coloration with Plazlyte. PMID:11033561

Lerouge, S; Guignot, C; Tabrizian, M; Ferrier, D; Yagoubi, N; Yahia, L

2000-12-15

293

Box-Behnken supported validation of stability-indicating high performance thin-layer chromatography (HPTLC) method: An application in degradation kinetic profiling of ropinirole  

PubMed Central

Stability-indicating high-performance thin-layer chromatographic (HPTLC) method for the analysis of ropinirole HCl was developed and validated as per the ICH guidelines. The method employed the mobile phase and toluene-ethyl acetate-6 M ammonia solution (5:6:0.5, v/v/v) was optimized with the help of a design expert. Densitometric analysis of ropinirole HCl was carried out in the absorbance mode at 250 and 254 nm. Compact spots for ropinirole HCl were found at Rf value of 0.58 ± 0.02. The linear regression analysis data for the calibration plots showed R2 = 0.9989 ± 0.0053 with a concentration range of 100–3000 ng spot?1. The method was validated for precision, accuracy, ruggedness, robustness, specificity, recovery, limit of detection (LOD) and limit of quantitation (LOQ). The LOD and LOQ were 12.95 and 39.25 ng spot?1 respectively. Drug was subjected to acidic, alkaline, oxidative, dry heat, wet heat and photo degradation stress. All the peaks of degradation products were well resolved from the standard drug peak with significant difference of Rf. The acidic and alkaline stress degradation kinetics of ropinirole, were found to be in first order, showing high stability (t1/2, 146.37 h?1; t0.9, 39.11 h?1) in the acidic medium and low stability (t1/2, 97.67 h?1; t0.9, 14.87 h?1) in the alkaline environment.

Mustafa, Gulam; Ahuja, Alka; Baboota, Sanjula; Ali, Javed

2011-01-01

294

Box-Behnken supported validation of stability-indicating high performance thin-layer chromatography (HPTLC) method: An application in degradation kinetic profiling of ropinirole.  

PubMed

Stability-indicating high-performance thin-layer chromatographic (HPTLC) method for the analysis of ropinirole HCl was developed and validated as per the ICH guidelines. The method employed the mobile phase and toluene-ethyl acetate-6 M ammonia solution (5:6:0.5, v/v/v) was optimized with the help of a design expert. Densitometric analysis of ropinirole HCl was carried out in the absorbance mode at 250 and 254 nm. Compact spots for ropinirole HCl were found at R f value of 0.58 ± 0.02. The linear regression analysis data for the calibration plots showed R (2) = 0.9989 ± 0.0053 with a concentration range of 100-3000 ng spot(-1). The method was validated for precision, accuracy, ruggedness, robustness, specificity, recovery, limit of detection (LOD) and limit of quantitation (LOQ). The LOD and LOQ were 12.95 and 39.25 ng spot(-1) respectively. Drug was subjected to acidic, alkaline, oxidative, dry heat, wet heat and photo degradation stress. All the peaks of degradation products were well resolved from the standard drug peak with significant difference of R f. The acidic and alkaline stress degradation kinetics of ropinirole, were found to be in first order, showing high stability (t 1/2, 146.37 h(-1); t 0.9, 39.11 h(-1)) in the acidic medium and low stability (t 1/2, 97.67 h(-1); t 0.9, 14.87 h(-1)) in the alkaline environment. PMID:23960823

Mustafa, Gulam; Ahuja, Alka; Baboota, Sanjula; Ali, Javed

2011-12-04

295

Development and validation of stability indicating method for the quantitative determination of venlafaxine hydrochloride in extended release formulation using high performance liquid chromatography  

PubMed Central

Objective: Venlafaxine,hydrochloride is a structurally novel phenethyl bicyclic antidepressant, and is usually categorized as a serotonin–norepinephrine reuptake inhibitor (SNRI) but it has been referred to as a serotonin–norepinephrine–dopamine reuptake inhibitor. It inhibits the reuptake of dopamine. Venlafaxine HCL is widely prescribed in the form of sustained release formulations. In the current article we are reporting the development and validation of a fast and simple stability indicating, isocratic high performance liquid chromatographic (HPLC) method for the determination of venlafaxine hydrochloride in sustained release formulations. Materials and Methods: The quantitative determination of venlafaxine hydrochloride was performed on a Kromasil C18 analytical column (250 × 4.6 mm i.d., 5 ?m particle size) with 0.01 M phosphate buffer (pH 4.5): methanol (40: 60) as a mobile phase, at a flow rate of 1.0 ml/min. For HPLC methods, UV detection was made at 225 nm. Results: During method validation, parameters such as precision, linearity, accuracy, stability, limit of quantification and detection and specificity were evaluated, which remained within acceptable limits. Conclusions: The method has been successfully applied for the quantification and dissolution profiling of Venlafaxine HCL in sustained release formulation. The method presents a simple and reliable solution for the routine quantitative analysis of Venlafaxine HCL.

Kaur, Jaspreet; Srinivasan, K. K.; Joseph, Alex; Gupta, Abhishek; Singh, Yogendra; Srinivas, Kona S.; Jain, Garima

2010-01-01

296

Stress degradation studies on azithromycin and development of a validated stability-indicating TLC-densitometric method with HPLC/electrospray ionization-MS analysis of degradation products.  

PubMed

The purpose of this work was to develop a sensitive stability-indicating TLC-densitometric method for determination of azithromycin (AZ) in the presence of its impurities E, I, and L, and to study the stability of AZ under different stress conditions. The method was developed on TLC aluminum plates precoated with silica gel F254 using the mobile phase methanol-acetone-ammonia 25% (2+13+0.1, v/v/v), which gives compact zones for AZ (Rf= 0.39) and impurities E, I, and L (Rf = 0.54, 0.20, and 0.05, respectively). Densitometric analysis of AZ and its impurities was carried out at 483 nm after spraying with sulfuric acid-ethanol (1 + 4, v/v) and heating at 100 degrees C for 5 min. The linear regression analysis data for the calibration plots showed good linear relationships with r = 0.9941 for AZ, 0.9987 for impurity E, 0.9989 for impurity I, and 0.9984 for impurity L. AZ was subjected to acidic and alkaline hydrolysis, oxidation, and reduction stress. The drug underwent degradation under these conditions. The degradation products were well-resolved from the pure drug, with significantly different Rf values. A plausible degradation pathway of AZ was established by HPLC/electrospray ionization-MS analysis of the products. PMID:23175975

Kwiecie?, Anna; Krzek, Jan; Walczak, Maria

297

Simple and sensitive stability-indicating ion chromatography method for the determination of cyclopropylamine in nevirapine and moxifloxacin hydrochloride drug substances.  

PubMed

A simple and sensitive ion chromatography method has been developed for the determination of cyclopropylamine (CPA) in nevirapine (NEV) and moxifloxacin HCl (MOX) pharmaceutical drug substances. Efficient chromatographic separation was achieved on a Metrosep C4, 5 ?m (250 mm × 4.0 mm) column. The mobile phase consists of 5 mM hydrochloric acid containing 10% (v/v) acetonitrile and was delivered in an isocratic mode at a flow rate of 0.9 mL min(-1) at 27°C. A conductometric detector was used for the detection of the analyte. The drug substances were subjected to stress conditions including oxidation, thermal, photolytic and humidity for the evaluation of the stability-indicating nature of the method. The method was validated for specificity, precision, linearity, accuracy and solution stability. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.10 ?g mL(-1) and 0.37 ?g mL(-1) respectively. The linearity range of the method is between 0.37 ?g mL(-1) and 1.5 ?g mL(-1) and the correlation coefficient is found to be 0.9971. The average recoveries of CPA in NEV and MOX are 97.0% and 98.0%, respectively. PMID:22396905

Kothapalli, Pavan Kumar S R; Khagga, Mukkanti; Mekala, Nageswara Rao; Sigamani, John Prasanna; Vundavilli, Jagadeesh Kumar; Masani, Narendra Kumar; Sharma, Hemant Kumar

2011-10-20

298

Simple and Sensitive Stability-Indicating Ion Chromatography Method for the Determination of Cyclopropylamine in Nevirapine and Moxifloxacin Hydrochloride Drug Substances  

PubMed Central

A simple and sensitive ion chromatography method has been developed for the determination of cyclopropylamine (CPA) in nevirapine (NEV) and moxifloxacin HCl (MOX) pharmaceutical drug substances. Efficient chromatographic separation was achieved on a Metrosep C4, 5 ?m (250 mm × 4.0 mm) column. The mobile phase consists of 5 mM hydrochloric acid containing 10% (v/v) acetonitrile and was delivered in an isocratic mode at a flow rate of 0.9 mL min?1 at 27°C. A conductometric detector was used for the detection of the analyte. The drug substances were subjected to stress conditions including oxidation, thermal, photolytic and humidity for the evaluation of the stability-indicating nature of the method. The method was validated for specificity, precision, linearity, accuracy and solution stability. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.10 ?g mL?1 and 0.37 ?g mL?1 respectively. The linearity range of the method is between 0.37 ?g mL?1 and 1.5 ?g mL?1 and the correlation coefficient is found to be 0.9971. The average recoveries of CPA in NEV and MOX are 97.0% and 98.0%, respectively.

Kothapalli, Pavan Kumar S. R.; Khagga, Mukkanti; Mekala, Nageswara Rao; Sigamani, John Prasanna; Vundavilli, Jagadeesh Kumar; Masani, Narendra Kumar; Sharma, Hemant Kumar

2012-01-01

299

Validated Stability-indicating Reverse-phase Ultra-performance Liquid Chromatography Method for Simultaneous Determination of Sodium Methylparaben, Sodium Propylparaben and Ketorolac Tromethamine in Topical Dosage Forms  

PubMed Central

A sensitive, fast, and stability-indicating isocratic reverse-phase ultra-performance liquid chromatography method was developed and validated for quantitative simultaneous determination of sodium methylparaben, sodium propylparaben and ketorolac tromethamine in topical dosage forms. Separation of all peaks was achieved by using acquity ethylene bridged hybrid C18 (50×2.1 mm, 1.7 ?) as stationary phase, mobile phase used was triethylamine buffer (pH 2.5):tetrahydrofuran:methanol (665:35:300, v/v/v) with isocratic mode at a flow rate of 0.40 ml/min. All component were detected at 252 nm with 10 min run time. The described method was found to be linear in the concentration range of 248-744 ?g/ml for ketorolac tromethamine, 20.8-62.4 ?g/ml for sodium methylparaben and 2.38-7.13 ?g/ml for sodium propylparaben with correlation coefficients more than 0.999. Method was validated in terms of specificity, linearity, accuracy, precision, solution stability, filter equivalency, and robustness as per International Conference on Harmonization guideline. Formulation was exposed to the stress conditions of peroxide, acid, base, thermal, and photolytic degradation and proven all components were well separated in the presence of degradants.

Roy, C.; Chakrabarty, J.; Modi, P. B.

2013-01-01

300

Rapid and simple stability indicating HPLC method for the determination of cilazapril in pure substance and pharmaceutical formulation in comparison with classic and derivative spectrophotometric methods.  

PubMed

The present study describes development and subsequent validation of high performance liquid chromatographic method (HPLC) in comparison with spectrophotometric methods (classic, first, second and third order derivative) for determination of pure cilazapril in substance and pharmaceutical preparation. The main aim of this study was to find the method suitable not only for determination of cilazapril, but additionally useful in degradation kinetic study. Only the HPLC method is stability indicating. The HPLC method utilizes LiChroCART 250-4 HPLC-Cartridge, LiChrospher 100 RP-18 (5 ?m) column, at ambient temperature, eluted at the flow rate 1.0 mL/min. The mobile phase consists of acetonitrile, methanol and phosphate buffer (pH 2.0) (60:10:30, v/v/v). Wavelength of detection is set at 212 nm. Benzocaine is used as an internal standard. The second and third order derivative spectrophotometric methods can be applied for the cilazapril analysis in substance and tablet, but not for stability evaluation (the lack of selectivity towards degradation product). PMID:22568033

Paszun, Sylwia K; Stanisz, Beata; Paw?owski, Wojciech

301

Validated Stability-indicating Reverse-phase Ultra-performance Liquid Chromatography Method for Simultaneous Determination of Sodium Methylparaben, Sodium Propylparaben and Ketorolac Tromethamine in Topical Dosage Forms.  

PubMed

A sensitive, fast, and stability-indicating isocratic reverse-phase ultra-performance liquid chromatography method was developed and validated for quantitative simultaneous determination of sodium methylparaben, sodium propylparaben and ketorolac tromethamine in topical dosage forms. Separation of all peaks was achieved by using acquity ethylene bridged hybrid C18 (50×2.1 mm, 1.7 ?) as stationary phase, mobile phase used was triethylamine buffer (pH 2.5):tetrahydrofuran:methanol (665:35:300, v/v/v) with isocratic mode at a flow rate of 0.40 ml/min. All component were detected at 252 nm with 10 min run time. The described method was found to be linear in the concentration range of 248-744 ?g/ml for ketorolac tromethamine, 20.8-62.4 ?g/ml for sodium methylparaben and 2.38-7.13 ?g/ml for sodium propylparaben with correlation coefficients more than 0.999. Method was validated in terms of specificity, linearity, accuracy, precision, solution stability, filter equivalency, and robustness as per International Conference on Harmonization guideline. Formulation was exposed to the stress conditions of peroxide, acid, base, thermal, and photolytic degradation and proven all components were well separated in the presence of degradants. PMID:24019569

Roy, C; Chakrabarty, J; Modi, P B

2013-03-01

302

Development and validation of a stability indicative HPLC-PDA method for kaurenoic acid in spray dried extracts of Sphagneticola trilobata (L.) Pruski, Asteraceae.  

PubMed

A gradient stability indicative HPLC-UV method was developed and validated for assay of the marker kaurenoic acid (KA) in spray dried extract of Sphagneticola trilobata (L.) Pruski. The marker, and another unidentified polar component, were separated on a Luna Phenomenex C(18) column (250×4.6 mm, 5 ?m) with mobile phase composed of acetonitrile:acidified water pH 3.0 with phosphoric acid, in a gradient run of 40 min; at a flow rate of 1.0 mL min(-1), 35 °C, using wavelengths of 210 and 338 nm. The method was linear over a KA concentration range of 4.5-30.0 ?g mL(-1), without interference of the herbal matrix on the linearity of the method. The RSD% values for the intra- and inter-day precision studies were <2.0 and <8.0% for inter-laboratorial study. The method showed excellent KA recovery (99.0%). The LOQ value was found to be 1.13 ?g mL(-1) and the method proved to be robust for small, deliberate changes in temperature and pH of the mobile phase with RSD%<2.5% for the KA assay. A forced degradation study of S. trilobata dried extract was conducted under conditions of visible light (1.200.000 l×h(-1)) and UV (200 Whm(-2)) irradiation, acid (0.5 mol L(-1) HCl, 30 min), basic (1 mol L(-1) NaOH, 2 h) and oxidative (30% H(2)O(2), 4h) hydrolysis, in order to develop a gradient stability-indicating LC-UV method for KA quantification, the selected marker, and also to detect the major polar components of the extract, under investigation. The KA contents remaining after these stress conditions were 72.3, 70.0, 97.6, 65.8 and 87.0%, respectively. The alkaline conditions resulted in higher degradation for the unknown polar components of the extract, without interference of supplementary peaks at the retention time of the KA. This method can be used for the KA assay and qualitative analysis of polar components in stability study of spray dried extracts of S. trilobata, for subsequent use in the quality control of dosage forms. PMID:23158359

Fucina, Giovana; Block, Luciana Catia; Baccarin, Thaisa; Ribeiro, Thiago Ruiz Gutierrez; Quintão, Nara Lins Meira; Filho, Valdir Cechinel; Silva, Ruth Meri Lucinda; Bresolin, Tania Mari Bellé

2012-09-25

303

Monitoring Cheddar cheese ripening by chemical indices of proteolysis  

Microsoft Academic Search

Zusammenfassung Zwei Cheddarkäse aus zwei verschiedenen Fabriken wurden 24 Wochen bei 10° C gereift und dann durch RP-HPLC auf in Citratpuffer bei pH 4,6 lösliche Peptide analysiert. Dreizehn Peptide mit Kettenlängen zwischen 35 und 65 Aminosäureresten und Molmassen zwischen 3800 und 7400 wurden isoliert und den korrespondierenden Sequenzen der Caseinfraktionen über Edman-Abbau und Aminosäurezusammensetzung zugeordnet. Alle Peptide erwiesen sich als

Hans-Dieter Belitz; Klaus-Peter Kaiser

1993-01-01

304

Development and validation of a stability-indicating method for determination of free sterols in the Asian medicinal leech Hirudo manillensis.  

PubMed

A rapid, simple, sensitive, selective, precise and robust thin-layer chromatography densitometric method for the determination of free sterols in leech was developed and validated on silica gel layer using carbon tetrachloride-methanol-formic acid (9.5:1.5:0.55, v/v/v). Spectrodensitometric scanning was carried using a Camag TLC scanner III at 366 nm after spraying 2% methanolic sulphuric acid, which gave compact spots for cholesterol (R(F) = 0.35 ± 0.02). The regression analysis data for calibration plot implied a good linear relationship (r(2) = 0.99958) between response and concentration over the range 100-600 ng per spot with respect to peak area. The limits of detection and quantification were found to be 13.8 ± 0.51 and 45.01 ± 1.29 ng per spot, respectively. Validation was in accordance to the International Conference on Harmonization guidelines. Cholesterol was subjected to forced stress conditions of oxidation, hydrolysis and heat. Degradation products resulting from the forced stress did not interfere with detection because the degradant peaks were well separated from the cholesterol peak. The densitometric method can be regarded as stability-indicating and can be used for quality control assay of cholesterol in leech extract. PMID:22595259

Hasan, Fatima; Khar, Roop K; Ahmad, Farhan J; Ahmad, Sayeed; Ali, Mushir; Iqbal, Zeenat; Reza, Mohammed H

2012-05-17

305

Stress Degradation Behavior of Atorvastatin Calcium and Development of a Suitable Stability-Indicating LC Method for the Determination of Atorvastatin, its Related Impurities, and its Degradation Products  

PubMed Central

A rapid, reversed-phase liquid chromatographic method was developed for the quantitative determination of Atorvastatin calcium, its related substances (12 impurities), and degradation impurities in bulk drugs. The chromatographic separation was achieved on a Zorbax Bonus-RP column by employing a gradient elution with water–acetonitrile–trifluoroacetic acid as the mobile phase in a shorter run time of 25 min. The flow rate was 1.0 mL/min and the detection wavelength was 245 nm. The drug substance was subjected to stress studies such as hydrolysis, oxidation, photolysis, and thermal degradation, and considerable degradation was observed in acidic hydrolysis, oxidative, thermal, and photolytic stress conditions. The formed degradation products were reported and were well-resolved from the Atorvastatin and its related substances. The stressed samples were quantified against a qualified reference standard and the mass balance was found to be close to 99.5% (w/w) when the response of the degradant was considered to be equal to the analyte (i.e. Atorvastatin), which demonstrates the stability-indicating capability of the method. The method was validated in agreement with ICH requirements. The method developed here was single and shorter (25 min method for the determination of all 12 related impurities of Atorvastatin and its degradation products), with clearly better resolution and higher sensitivity than the European (85 min method for the determination of six impurities) and United States pharmacopeia (115 min and 55 min, two different methods for the determination of six related substances).

Vukkum, Pallavi; Moses Babu, J.; Muralikrishna, R.

2013-01-01

306

Novel Validated Stability-Indicating UPLC Method for the Estimation of Naproxen and its Impurities in Bulk Drugs and Pharmaceutical Dosage Form  

PubMed Central

A novel, reversed-phase ultra-performance liquid chromatographic method was developed and validated for the determination of related substances in Naproxen (NAP) bulk drugs and dosage forms. The related substances included degradation and process-related impurities. The method was developed using the Waters Acquity BEH C18 column using the gradient program with mobile phase A of a pH 7.0 phosphate buffer and methanol in the ratio of 90: 10 (v/v) and mobile phase B as methanol and acetonitrile in the ratio of 50:50 (v/v). Naproxen and its impurities were monitored at 260 nm. Naproxen was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, humidity, and photolytic degradations. The degradation products were well-resolved from the main peak and its impurities, proving the stability-indicating power of the method. The performance of the method was validated according to the present ICH guidelines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness, and robustness.

Venkatarao, Papanaboina; Nagendra Kumar, Morrisetty; Ravi Kumar, Maram

2012-01-01

307

A Novel, Validated Stability-Indicating UPLC Method for the Estimation of Lansoprazole and its Impurities in Bulk Drug and Pharmaceutical Dosage Forms  

PubMed Central

A novel, reversed-phase ultra-performance liquid chromatographic method was developed and validated for the determination of the assay and related substances of Lansoprazole (LAN) in bulk drug and capsule dosage forms. The related substances include degradation and process-related impurities. The method was developed using the Waters Acquity BEH C18 column and gradient program with mobile phase A as a pH 7.0 phosphate buffer and methanol in the ratio of 90: 10 (v/v), and mobile phase B as methanol and acetonitrile in the ratio of 50:50 (v/v). Lansoprazole and its impurities were monitored at 285 nm. Lansoprazole was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, humidity, and photolytic degradation and found to degrade significantly under acid and oxidative stress conditions. The degradation products were well-resolved from the main peak and its impurities, proving the stability-indicating power of the method. The performance of the method was validated according to the present ICH guidelines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness, and robustness.

Rao, Papanaboina Venkata; Kumar, Morrisetty Nagendra; Kumar, Maram Ravi

2013-01-01

308

Forced degradation study to develop and validate stability-indicating RP-LC method for the determination of ciclesonide in bulk drug and metered dose inhalers.  

PubMed

A simple, selective and precise stability-indicating reversed-phase liquid chromatographic method was developed and validated for the determination of ciclesonide. Ciclesonide was subjected to acid and alkali hydrolysis, oxidation, thermal and photo-degradation. The degradation products were well separated from the pure drug. The method was based on isocratic elution of ciclesonide and its degradation products on reversed phase C18 column (250 mm × 4.6 mm, 10 ?m) - Phenomenex using a mobile phase consisting of ethanol-water (70:30, v/v) at a flow rate of 1 mL min(-1). Quantitation was achieved with UV detection at 242 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 5-200 ?g mL(-1). Desisobutyryl-ciclesonide was prepared by selective alkaline hydrolysis of the ester and proved to be the main degradation product. The proposed method was successfully applied to the determination of ciclesonide in bulk and in its pharmaceutical preparation. PMID:22099671

Elkady, Ehab F; Fouad, Marwa A

2011-10-10

309

A stability-indicating ultra-performance liquid chromatographic method for estimation of related substances and degradants in paliperidone active pharmaceutical ingredient and its pharmaceutical dosage forms.  

PubMed

A simple, linear gradient, rapid, precise and stability-indicating analytical method was developed for the estimation of related substances and degradants of paliperidone API and tablets. The chromatographic separations were achieved using an Acquity ultra-performance liquid chromatograph (BEH 100 mm, 2.1 mm, 1.7 µm C-18 column) employing 0.01 M potassium dihydrogen phosphate buffer (pH 2.0) as mobile phase A and acetonitrile-water (9:1) as mobile phase B. A linear gradient (mobile phase A, mobile phase B in the ratio of 84:16) with a 0.45 mL/min flow rate was chosen. All six impurities were eluted within five minutes of run time. The column temperature was maintained at 25 °C and a detector wavelength of 238 nm was employed. Paliperidone was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions. The stressed samples were analyzed by the proposed method. Considerable degradation of the analyte was observed when it was subjected to oxidative conditions and impurity F was found to be the major degradant. Peak homogeneity data of paliperidone obtained by photodiode array (PDA) detection demonstrated the specificity of the method in the presence of degradants. The method was validated with respect to linearity, precision, accuracy, ruggedness, robustness, limit of detection and limit of quantification. PMID:22407348

Bindu, K Hima; Reddy, I Ugandar; Anjaneyulu, Y; Suryanarayana, M V

2012-04-01

310

Stability-indicating methods for determination of pyritinol dihydrochloride in the presence of its precursor and degradation product by derivative spectrophotometry.  

PubMed

A first-derivative spectrophotometric (1D) method and a derivative-ratio zero-crossing spectrophotometric (1DD) method were used to determine pyritinol dihydrochloride (I) in the presence of its precursor (II) and its degradation product (III) with 0.1N hydrochloric acid as a solvent. Linear relationships were obtained in the ranges of 6-22 microg/mL for the (1D) method and 6-20 microg/mL for the (1DD) method. By applying the proposed methods, it was possible to determine pyritinol dihydrochloride in its pure powdered form with an accuracy of 100.36 +/- 1.497% (n = 9) for the (1D) method and an accuracy of 99.92 +/- 1.172% (n = 8) for the (1DD) method. Laboratory-prepared mixtures containing different ratios of (I), (II), and (III) were analyzed, and the proposed methods were valid for concentrations of < or = 10% (II) and < or = 50% (III). The proposed methods were validated and found to be suitable as stability-indicating assay methods for pyritinol in pharmaceutical formulations. PMID:15759729

Shehata, Mostafa A; el-Sayed, Mohammad A; el-Bardicy, Mohammad G; el-Tarras, Mohammad F

311

CHARACTERIZATION OF PHENOLIC COMPOUNDS IN STRAWBERRY FRUITS BY RP-HPLC-DAD AND INVESTIGATION OF THEIR ANTIOXIDANT CAPACITY  

Microsoft Academic Search

This research was undertaken to evaluate the phenolic compositions and antioxidant capacities of strawberry cultivars (Camarosa, Seyhun, and Osmanli) grown in Turkey. High performance liquid chromatography coupled with diode array and coulometric array detectors were used to characterize and quantify organic acids and phenolic compounds. Four organic acids (citric, malic, shikimic, and ascorbic acids) were determined. The major organic acid

Hasim Kelebek; Serkan Selli

2011-01-01

312

Development and Validation of RP-HPLC Method for the Determination of Methamphetamine and Propranolol in Tablet Dosage Form  

PubMed Central

A new isocratic reversed-phase HPLC method with diode-array UV detection was developed and validated for the determination of methamphetamine and propranolol in tablet dosage forms. Chromatography was carried out on an XTerra RP18 (150×4.6 mm, 5 ?m) column using 50 mM pyrrolidine (pH 11.5) – acetonitrile (50:50, v/v) as mobile phase at a flow rate of 1 ml/min. Spectrophotometric detection was performed at a wavelength of 214 nm. The linearity was established over the concentration range of 0.075-0.60 mg/ml for both drugs. The correlation coefficients (r2) were ?0.9998 in each case. The relative standard deviation values for intermediate precision studies were <1%. Statistical analysis of the data showed that the method was precise, accurate, reproducible and selective for the analysis of methamphetamine and propranolol drugs. The method was successfully employed for the determination of propranolol and methamphetamine in commercially available tablet dosage form.

Shabir, G. A.

2011-01-01

313

Effects of ionic liquid on the separation of 2-chlorophenol and 2,4,6-trichlorophenol in RP-HPLC.  

PubMed

In this study, the use of ionic liquids as additives in the separation of 2-chlorophenol and 2,4,6-trichlorophenol in reversed-phase high-performance liquid chromatography is reported. The ionic liquids used were 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium methylsulfate ([EMIm][MS]), and 1-octyl-3-methylimidazolium methylsulfate ([OMIm][MS]), because of their high hydrophobicity and good solvating properties. The effects of the ionic liquid on retention factor and resolution, and the change of detector response using the different ionic liquids were studied. Separation with the [MS] anion ionic liquid in the eluent resulted in better resolution than with the [BF4] anion ionic liquid. The best result was achieved using 3.0 mM/L of [OMIm][MS] and 1.0 mM/L [EMIm][MS] as mobile phase additives. PMID:19476708

Zheng, J; Row, K H

314

RP-HPLC analytical method development and optimization for quantification of donepezil hydrochloride in orally disintegrating tablet.  

PubMed

An easy, fast and validated RV-HPLC method was invented to quantify donepezil hydrochloride in drug solution and orally disintegrating tablet. The separation was carried out using reversed phase C-18 column (Agilent Eclipse Plus C-18) with UV detection at 268 nm. Method optimization was tested using various composition of organic solvent. The mobile phase comprised of phosphate buffer (0.01M), methanol and acetonitrile (50:30:20, v/v) adjusted to pH 2.7 with phosphoric acid (80%) was found as the optimum mobile phase. The method showed intraday precision and accuracy in the range of 0.24% to -1.83% and -1.83% to 1.99% respectively, while interday precision and accuracy ranged between 1.41% to 1.81% and 0.11% to 1.90% respectively. The standard calibration curve was linear from 0.125 ?g/mL to 16 ?g/mL, with correlation coefficient of 0.9997±0.00016. The drug solution was stable under room temperature at least for 6 hours. System suitability studies were done. The average plate count was > 2000, tailing factor <1, and capacity factor of 3.30. The retention time was 5.6 min. The HPLC method was used to assay donepezil hydrochloride in tablet and dissolution study of in-house manufactured donepezil orally disintegrating tablet and original Aricept. PMID:24035953

Liew, Kai Bin; Peh, Kok Khiang; Fung-Tan, Yvonne Tze

2013-09-01

315

RP-HPLC analysis of phenolic compounds and flavonoids in beverages and plant extracts using a CoulArray detector.  

PubMed

Methods were developed for the analysis of natural antioxidants including phenolic compounds and flavonoids in beverages and plant extracts using gradient HPLC with multi-channel electrochemical coulometric detection. Suitability of various reversed-phase columns for this purpose was compared; pH and mobile phase gradients were optimized with respect to the separation selectivity and sensitivity of detection. Because of different target compounds in various sample types, the overlapping resolution maps and the normalized resolution product approaches described earlier were used to select optimum columns and gradients to suit the analysis of the individual sample types. The methods were applied to the analysis of phenolic compounds and flavonoids in beer, wine, tea, and yacon extracts. 32 phenolic compounds were identified and determined, including derivatives of benzoic and cinnamic acids, flavones, and a few related glycosides. Eight-channel CoulArray detection offers high selectivity and sensitivity with limits of detection in the low microg L(-1) range, at least an order of magnitude lower than single-channel coulometric detection using the Coulochem detector. No special sample pretreatment is necessary and, because of the compatibility of the CoulArray detector with gradient elution, phenolic antioxidants of different polarities can be determined in a single run. In addition to the retention times, the ratios of the areas of the pre-dominant and post-dominant peaks to the area of the dominant peak can be used for improved identification of natural antioxidants. PMID:16013828

Jandera, Pavel; Skeifíková, Veronika; Rehová, Lucie; Hájek, Tomás; Baldriánová, Lucie; Skopová, Gabriela; Kellner, Vladimír; Horna, Ales

2005-06-01

316

Development of an RP?HPLC Method for the Analysis of Phenolic Compounds in Achillea millefolium L  

Microsoft Academic Search

Several major phenolic constituents present in yarrow (Achillea millefolium L. s.l.) were determined for a homogenized plant sample. In order to optimize the conditions for sample preparation of the botanical matrix two different solvent extraction methods (maceration and ultrasonic agitation) were assayed. The preliminary maceration studies were performed to determine the influence of extracting solvents on the recovery of phenolics

Raimondas Benetis; Jolita Radušien?; Valdas Jakštas; Valdimaras Janulis; Faustas Malinauskas

2008-01-01

317

Screening for pyrrolizidine alkaloids in plant materials by electron ionization RP-HPLC-MS with thermabeam interface.  

PubMed

Plant samples from leaves of Cerinthe minor, Cynoglossum clandestinum, Echium tuberculatum (as well roots), Eritrichium rupestre, Lithospermum purpureo-coerulem, Nonnea lutea, Nonnea setosa, Onosma stellulatum and Cynoglossum amabile were screened for toxic pyrrolizidine alkaloids (PAs) with a newly elaborated procedure comprising gradient HPLC with diode array (DAD) and thermabeam electron impact mass spectrometry (EI-MS). Dried plant material was extracted with boiling 1% tartaric acid in methanol for 2 h on an electric basket and crude extracts purified with cation-exchange solid phase extraction (CE-SPE). Purified extracts containing alkaloids were separated on Zorbax SB RP18 stationary phase in gradient of 0.1% formic acid in methanol. The flow rate was 0.25 mL/min and was suitable both for DAD and EI MS detections. Applied gradient procedure permitted quite sufficient separation of PAs in various plant extracts. On the basis of EI MS spectra, toxic PAs with unsaturated 1,2-double bond in the necine moiety were found in all plant materials and in nine of them (excluding only Cynoglossum amabile) for the fi rst time. They included the following types of structures: 9- and 7-viridifloryl-retronecine monoesters, 9-angeloyl-7-viridifloryl-retronecine, 9-angeloyl-retronecine diester, 9-viridifloryl-retronecine saturated ester, 7-angeloyl-9-viridifloryl-retronecine, 7-angeloyl-9-echimidinyl-retronecine, trachelanthamine and others. Selected ion monitoring (SIM) chromatograms at m/z 119, 120 and 136 together with analysis of UV spectra from DAD detector can be applied in rapid screening for toxic PAs in new plant extracts but to obtain detailed structural information (molecular weight and stereochemistry) more expensive hyphenation is required. Consumption of all analysed plants should be avoided as carcinogenic and hepatotoxic properties of the alkaloids detected are expected. PMID:15386579

Mroczek, Tomasz; Baj, Stefan; Chrobok, Anna; Glowniak, Kazimierz

2004-11-01

318

RP-HPLC SEPARATION METHOD FOR INDIVIDUAL COMPONENTS OF POLYCAP IN PRESENCE OF THEIR DEGRADATION\\/INTERACTION PRODUCTS  

Microsoft Academic Search

Polypill is a fixed dose combination, used as a single daily pill to achieve a large effect in preventing cardiovascular disease with minimal adverse effects. In the present study, gradient LC method was developed for simultaneous determination of the Polycap, that is, Atenolol, Hydrochlorothiazide, Aspirin, Ramipril, and Simvastatin, in presence of their major interaction\\/degradation products. The individual drug components and

Satheesh Kumar Shetty; Roshan M. Borkar; Prashant S. Devrukhakar; K. V. Surendranath; P. Radhakrishnanand; J. Satish; Nalini Shastri; Johnson Jogul; Upendra Mani Tripathi

2012-01-01

319

RP–HPLC tryptic mapping of IgG1 proteins with post-column fluorescence derivatization  

Microsoft Academic Search

Peptide mapping is an important analytical technique widely used to study the primary structure of proteins. In quality control settings, it is employed as an identity test to probe for small changes in protein primary structure. A great challenge in peptide mapping is to minimize the detection limit for peptides due to the low detectability of smaller peptides based on

Dipti Gulati; Jacob Bongers; Sudhir Burman

1999-01-01

320

Development and validation of a fast RP-HPLC method for determination of methotrexate entrapment efficiency in polymeric nanocapsules.  

PubMed

A rapid and effective isocratic chromatographic procedure is successfully developed to determinate methotrexate (MTX) entrapment efficiency (EE) in polymeric nanocapsules using reversed-phase high-performance liquid chromatography. The method employed a RP-C(18) Shimadzu Shim-pack CLC-ODS (150 mm x 4.6 mm, 5 microm) column with mobile phase constituted by a mixture of water-acetonitrile-tetrahydrofuran (65:30:5 v/v/v; pH 3.0) at a flow rate of 0.8 mL/min. The eluate is monitored with a UV detector set at 313 nm. The parameters used in the validation process are: linearity, specificity, precision, accuracy, and limit of quantitation (LOQ). The linearity is evaluated by a calibration curve in the concentration range of 10-50 microg/mL and presented a correlation coefficient of 0.9998. The polymers (PLA or PLA-PEG), oil, and surfactants used in the nanocapsule formulation did not interfere with analysis and the recovery was quantitative. The intra and inter-day assay relative standard deviation were less than 0.72%. Results are satisfactory, and the method proved to be adequate for the determination of methotrexate in nanocapsules formulations. PMID:18647471

Sartori, Tatiane; Seigi Murakami, Fabio; Pinheiro Cruz, Ariane; Machado de Campos, Angela

2008-07-01

321

RP-HPLC analysis of phenolic acids of selected Central European Carex L. (Cyperaceae) species and its implication for taxonomy.  

PubMed

Eighteen species belonging to the Carex genus were checked for the presence and the amount of eight phenolic acids (p-hydroxybenzoic, vanillic, caffeic, syringic, protocatechuic, p-coumaric, sinapic, and ferulic) by means of HPLC. Both the free and bonded phenolic acids were analyzed. The majority of the analyzed acids occurred in the studied species in relatively high amounts. The highest concentrations found were caffeic acid and p-coumaric acid, for which the detected levels were negatively correlated. A very interesting feature was the occurrence of sinapic acid, a compound very rarely detected in plant tissues. Its distribution across the analyzed set of species can be hypothetically connected with the humidity of plants' habitats. Several attempted tests of aggregative cluster analysis showed no similarity to the real taxonomical structure of the genus Carex. Thus, the phenolic acids' composition cannot be considered as the major taxonomical feature for the genus Carex. PMID:21391476

Bogucka-Kocka, Anna; Szewczyk, Katarzyna; Janyszek, Magdalena; Janyszek, S?awomir; Cie?la, ?ukasz

322

Application of the iodine-azide postcolumn reaction in RP-HPLC for the determination of thioguanine in urine.  

PubMed

The study focuses on the analysis of a sensitive, selective, and simple postcolumn detection method for thioguanine determination, based on the sensitizing induction of thioguanine on iodine-azide reaction and the combination technique of HPLC. The analysis was accomplished in the optimum conditions for iodine-azide detection system and HPLC separation. The values for the linear range, the LOD, and DOQ amounted to 0.8-1.7, 0.4, and 0.5 nmol/mL urine, respectively. PMID:18615825

Zakrzewski, Robert

2008-07-01

323

Simultaneous Determination of Ofloxacin and Ornidazole in Solid Dosage Form by RP-HPLC and HPTLC Techniques.  

PubMed

The objective of this work was to develop and validate simple, rapid and accurate chromatographic methods for simultaneous determination of ofloxacin and ornidazole in solid dosage form. The first method was based on reversed phase high performance liquid chromatography, on Intersil C(18) column (250 mm, 4.6 i.d.), using acetonitrile:methanol: 0.025M phosphate buffer, pH 3.0 (30:10:60 % v/v/v) as the mobile phase, at a flow rate of 1 ml/min at ambient temperature. Quantification was achieved with UV detection at 318 nm over a concentration range of 2-40 µg/ml for ofloxacin and 5-100 µg/ml for ornidazole. The mean retention time of ofloxacin and ornidazole was found to be 4.04 min and 5.83 min, 6.77 min (isomers), respectively. The amount of ofloxacin and ornidazole estimated as percentage of label claimed was found to be 100.23 and 99.61%, with mean percent recoveries 100.20 and 100.93%, respectively. The second method was based on TLC separation of these drugs using silica gel 60F(254) aluminium sheets and dichloromethane:methanol:25% ammonia solution (9.5:1:3 drops v/v) as mobile phase. Detection was carried out at 318 nm over the concentration range of 20-100 ng/spot for ofloxacin and 50-250 ng/spot for ornidazole. The mean R(f) value of ofloxacin and ornidazole was found to be 0.16 and 0.56, 0.78 (isomers), respectively. The amount of ofloxacin and ornidazole estimated as percentage of label claimed was found to be 100.23 and 99.61% with mean percent recoveries 100.47 and 99.32%, respectively. Both these methods were found to be simple, precise, accurate, selective and rapid and could be successfully applied for the determination of pure laboratory prepared mixtures and tablets. PMID:21218068

Puranik, Manisha; Bhawsar, D V; Rathi, Prachi; Yeole, P G

2010-07-01

324

[A new method for predicting retention time of solutes under linear gradient elution conditions in RP-HPLC].  

PubMed

A new method for predicting the retention time of solutes under linear gradient elution has been established. In this method, the migration distance of solutes in column and the mobile phase gradient were modified simultaneously according to the distribution of mobile phase in column. The prediction results of retention time of both weakly and strongly retentive solutes were accurate in different instrumental systems using this method. In order to test and verify this method, the retention time of fifteen amino acids and eight homologous compounds of benzene were predicted. The predicted results were compared with those predicted by the method in common use. The relative average errors between predicted and experimental values were 3.70% and 4.90% for the weakly retentive solutes, far smaller than those obtained by the reference method (23.61% and 31.16%). For the strongly retentive solutes, the relative average errors were 0.21% and 6.01% respectively, slightly smaller than those obtained by the reference method (0.81% and 6.69%). It is seen that this new method has many advantages. PMID:12541812

Shan, Y C; Zhao, R H; Zhang, W B; Zhang, Y K

2001-05-01

325

Development and validation of a fast RP-HPLC method for the determination of clobetasol propionate in topical nanocapsule suspensions.  

PubMed

A simple and rapid high-performance liquid chromatographic method is validated for the determination of clobetasol propionate in topical nanocapsule suspensions. The method is carried out on an RP-18 column with a mobile phase composed of methanol-water (80:20 v/v) and UV detection at 241 nm. The method validation yields good results with respect to linearity, specificity, precision, accuracy, and robustness. The calibration curve in the range of 5.0-40.0 microg/mL shows a correlation coefficient of 0.9999. Precision (intra-day and inter-day) is demonstrated by a relative standard deviation lower than 1.5%. Accuracy is assessed by the recovery test of clobetasol propionate from sample matrixes (98.33 +/- 0.88%). In conclusion, the method is suitable to be applied to assay clobetasol propionate in topical formulations of polymeric nanocapsules, avoiding the use of a buffer solution in the mobile phase. PMID:20819292

Fontana, M C; Bastos, M O; Beck, R C R

2010-09-01

326

Validated RP-HPLC Method for Simultaneous Quantitation of Losartan Potassium and Metolazone in Bulk Drug and Formulation  

PubMed Central

A HPLC method has been described for simultaneous determination of Losartan potassium and Metolazone in formulation. This method is based on a HPLC separation of the two drugs on the Thermo Hypersil BDS–C18 (250 mm × 4.6 mm, 5.0 ?m) with isocratic conditions and a simple mobile phase containing acetonitrile:water (60:40) at a flow rate of 0.8 mL/min using UV detection at 237 nm. This method has been applied to a marketed formulation without interference of excipients. The linear regression analysis data for the calibration plots showed a good linear relationship over the concentration range of 2–12 ?g/mL for Losartan potassium and 0.2–1.2 ?g/mL for Metolazone, respectively. The method was validated for precision, robustness and recovery. Statistical analysis showed that the method is repeatable and selective for the estimation of Losartan potassium and Metolazone.

Dubey, Ramkumar; Bhusari, Vidhya K.; Dhaneshwar, Sunil R.

2011-01-01

327

Validated RP-HPLC Method for Simultaneous Quantitation of Losartan Potassium and Metolazone in Bulk Drug and Formulation.  

PubMed

A HPLC method has been described for simultaneous determination of Losartan potassium and Metolazone in formulation. This method is based on a HPLC separation of the two drugs on the Thermo Hypersil BDS-C(18) (250 mm × 4.6 mm, 5.0 ?m) with isocratic conditions and a simple mobile phase containing acetonitrile:water (60:40) at a flow rate of 0.8 mL/min using UV detection at 237 nm. This method has been applied to a marketed formulation without interference of excipients. The linear regression analysis data for the calibration plots showed a good linear relationship over the concentration range of 2-12 ?g/mL for Losartan potassium and 0.2-1.2 ?g/mL for Metolazone, respectively. The method was validated for precision, robustness and recovery. Statistical analysis showed that the method is repeatable and selective for the estimation of Losartan potassium and Metolazone. PMID:21886902

Dubey, Ramkumar; Bhusari, Vidhya K; Dhaneshwar, Sunil R

2011-06-26

328

Validated RP-HPLC method for determination of permethrin in bulk and topical preparations using UV-vis detector.  

PubMed

An isocratic reversed-phase high-performance liquid chromatographic method for the estimation of permethrin in raw materials and pharmaceutical topical preparations has been devised and validated. The chromatographic analysis was performed on a 5 ?m particle C-18 Nucleosil (Macherey-Nagel, Germany) column (250 × 4.6 mm). Mobile phase consisted of methanol and 0.025 mM Phosphoric acid (85:15 v/v) at a flow rate of 1.5 mL/min. UV detection was performed at 272 nm and peaks were identified with retention times as compared with standards. The limit of detection was 1.782 ?g/mL, while limit of quantitation was 48.0 ?g/mL. The calibration was linear in a concentration range of 48.0-5000 ?g/mL with correlation coefficient of 0.999978. Regression equation was absorbance =2833.23 × concentration(?g/mL) + 19.1045 with variance of the response variable, S(yx)(2), calculated to be 1.75328 (six degrees of freedom). The method was validated as per ICH guidelines and USP requirements and found advantageous for the routine analysis of the drug in pharmaceutical formulations and in pharmaceutical investigations involving permethrin. PMID:21439119

Arayne, M Saeed; Sultana, Najma; Hussain, Fida

2011-04-01

329

Activity assay of His-tagged E. coli DNA photolyase by RP-HPLC and SE-HPLC  

Microsoft Academic Search

Escherichia coli DNA photolyase was expressed as C-terminal 6× histidine-fused protein. Purification of His-tagged E. coli DNA photolyase was developed using immobilized metal affinity chromatography with Chelating Sepharose Fast Flow. By one-step affinity chromatography, approximate 4.6 mg DNA photolyase was obtained from 400 ml E. coli culture. The purified His-tagged enzyme was combined with two chromophors, FADH and MTHF. Using

Wanmeng Mu; Dongfang Zhang; Lei Xu; Zhaofeng Luo; Yuzhen Wang

2005-01-01

330

Analytical method development and validation of prasugrel in bulk and its pharmaceutical formulation using the RP-HPLC method  

PubMed Central

Purpose: This study was designed to develop and validate a simple, sensitive, precise, and specific reverse phase high-performance liquid chromatographic (HPLC) method for the determination of prasugrel in bulk and its tablet dosage forms. Materials and Methods: The HPLC separation was carried out by reverse phase chromatography on an inertsil ODS-3V column (5 ?m; 250 × 4.6mm2) with a mobile phase composed of 0.02 M potassium dihydrogen orthophosphate, 0.02 M dipotassium hydrogen orthophosphate in water:acetonitrile (30:70 v/v) in isocratic mode at a flow rate of 1 ml/min. The detection was monitored at 210 nm. Results: The calibration curve for prasugrel was linear from 100 to 600 ?g/ml. The inter-day and intra-day precision was found to be within limits. The proposed method has adequate sensitivity, reproducibility, and specificity for the determination of prasugrel in bulk and its tablet dosage forms. The limit of detection and limit of quantification for prasugrel were found to be 0.25 ?g/ml and 0.75 ?g /ml, respectively. Accuracy (recoveries: 99.8–101.2%) and reproducibility were found to be satisfactory. Conclusion: The proposed method is simple, fast, accurate, and precise for the simultaneous quantification of prasugrel in the dosage form, bulk drugs as well as for routine analysis in quality control.

Ishaq, B. Mohammed; Prakash, K. Vanitha; Mohan, G. Krishna

2011-01-01

331

RP-HPLC method with electrochemical detection for the determination of metoclopramide in serum and its use in pharmacokinetic studies.  

PubMed

A rapid and sensitive reversed-phase high performance liquid chromatographic method has been developed for the determination of metoclopramide in serum. The assay was performed after single extraction with ethyl ether using methyl parahydroxybenzoate as internal standard. Chromatographic separations were performed on C(18) stationary phase with a mobile phase composed of methanol-phosphate buffer pH 3 (30:70 v/v). Analytes were detected electrochemically. The quantification limit for metoclopramide in serum was 2 ng mL(-1). Linearity of the method was confirmed in the range of 5-120 ng mL(-1) (correlation coefficient 0.9998). Within-day relative standard deviations (RSDs) ranged from 0.3 to 5.5% and between-day RSDs from 0.8 to 6.0%. The analytical method was successfully applied for the determination of pharmacokinetic parameters after ingestion of 10 mg dose of metoclopramide. Studies were performed on 18 healthy volunteers of both sexes. PMID:11748686

Lamparczyk, H; Chmielewska, A; Konieczna, L; Plenis, A; Zarzycki, P K

2001-12-01

332

New RP?HPLC Method with UV?Detection for the Determination of Carvedilol in Human Serum  

Microsoft Academic Search

Carvedilol has been used as an antihypertensive drug and also possesses antioxidant and antiproliferative effects. A simple and sensitive analytical method for carvedilol in human serum by using high performance liquid chromatography (HPLC) was developed. The method employs a liquid?liquid extraction for isolation and sample concentration followed by reversed phase liquid chromatography (RPLC) analysis using ultraviolet (UV) detection at 238 nm.

Ramesh Gannu; Vamshi Vishnu Yamsani; Yamsani Madhusudan Rao

2007-01-01

333

Separation and Measurement of Plant Alkaloid Enantiomers by RP-HPLC Analysis of their Fmoc-Alanine Analogs  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plants often synthesize secondary metabolites that are enantiomers. Enantiomers can cause very different physiological responses. Ammodendrine (1) and anabasine (2) are teratogens that can cause congenital malformations in livestock and enantiomeric forms of each have been found in Lupinus spp. an...

334

Simultaneous determination of clopidogrel and aspirin by RP-HPLC from bulk material and dosage formulations using multivariate calibration technique.  

PubMed

A rapid, simple, and easy method for the simultaneous determination of clopidogrel and aspirin from bulk material and dosage formulations in the presence of meloxicam as internal standard has been developed. Separation was carried out on a Purospher star C(18) (5 ?m, 250 × 4.6 mm) column at ambient temperature. The mobile phase consisted of methanol-water (80:20, v/v), the pH of the mobile phase was adjusted to 3.4 with ortho-phosphoric acid and pumped at a flow rate of 1 mL/min using isocratic pump system. Multivariate chromatographic calibration technique was subjected to high-performance liquid chromatography (HPLC) data for simultaneous quantitative analysis of binary mixtures of clopidogrel and aspirin. HPLC data based on the analyte peak areas were obtained at five wavelengths (225, 230, 235, 240, and 245 nm). The mathematical algorithm of multivariate chromatographic calibration technique is based on the use of the linear regression equations. Calibration plots for clopidogrel and aspirin were constructed at each wavelength by using the peak areas corresponding to the concentrations of each active compound. This multivariate chromatographic method was also applied to a commercial pharmaceutical dosage form containing clopidogrel and aspirin. PMID:21223644

Sultana, Najma; Arayne, Muhammad S; Ali, Kiran A; Nawaz, Muhammad

2011-02-01

335

Validated Stability-Indicating HPLC-DAD Method for the Simultaneous Determination of Diclofenac Sodium and Diflunisal in Their Combined Dosage Form  

PubMed Central

A simple, rapid, and highly selective HPLC-DAD method was developed for the simultaneous determination of diclofenac sodium (DIC) and diflunisal (DIF) in pure form and in their combined formulation. Effective chromatographic separation was achieved using a Zorbax SB-C8 (4.6×250 mm, 5 ?m particle size) column with a mobile phase composed of 0.05 M phosphoric acid, acetonitrile, and methanol in the ratio of 40:48:12 (by volume). The mobile phase was pumped isocratically at a flow rate of 1 mL/min, and quantification of the analytes was based on measuring their peak areas at 228 nm. The retention times for diflunisal and diclofenac were about 7.9 and 9.5 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. Calibration curves were linear in the ranges of 5–100 ?g/mL for both drugs with correlation coefficients >0.9998. The proposed method proved to be selective and stability-indicating by the resolution of the two analytes from four of their related substances and potential impurities as well as from forced-degradation (hydrolysis, oxidation, photolysis, and dry heat) products. The validated HPLC method was successfully applied to the analysis of DIC and DIF in their combined dosage form (suppositories). The proposed method made use of the diode array detector (DAD) as a tool for peak identity and purity confirmation.

Shaalan, Rasha A.; Belal, Tarek S.

2013-01-01

336

Development of validated stability-indicating chromatographic method for the determination of fexofenadine hydrochloride and its related impurities in pharmaceutical tablets  

PubMed Central

A simple reversed phase high performance liquid chromatographic method with diode array detector (HPLC-DAD) has been developed and subsequently validated for the determination of fexofenadine hydrochloride (FEX) and its related compounds; keto fexofenadine (Impurity A), meta isomer of fexofenadine (Impurity B), methyl ester of fexofenadine (Impurity C) in addition to the methyl ester of ketofexofenadine (Impurity D). The separation was based on the use of a Hypersil BDS C-18 analytical column (250 × 4.6 mm, i.d., 5 ?m). The mobile phase consisted of a mixture of phosphate buffer containing 0.1 gm% of 1-octane sulphonic acid sodium salt monohydrate and 1% (v/v) of triethylamine, pH 2.7 and methanol (60:40, v/v). The separation was carried out at ambient temperature with a flow rate of 1.5 ml/min. Quantitation was achieved with UV detection at 215 nm using lisinopril as internal standard, with linear calibration curves at concentration ranges 0.1-50 ?g/ml for FEX and its related compounds. The optimized conditions were used to develop a stability-indicating HPLC-DAD method for the quantitative determination of FEX and its related compounds in tablet dosage forms. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. Complete separation was achieved for the parent compounds and all degradation products. The method was validated according to ICH guidelines in terms of accuracy, precision, robustness, limits of detection and quantitation and other aspects of analytical validation.

2011-01-01

337

Rapid Simultaneous Determination of Telmisartan, Amlodipine Besylate and Hydrochlorothiazide in a Combined Poly Pill Dosage Form by Stability-Indicating Ultra Performance Liquid Chromatography  

PubMed Central

A simple, precise and rapid stability-indicating ultra-performance liquid chromatography (UPLC) method is developed for the simultaneous quantitative determination of Telmisartan, Amlodipine besylate and Hydrochlorothiazide from their innovative poly pill combination drug product in the presence of degradation products. It involves a 100 mm x 2.1 mm, 1.7 ?m C-18 column. The separation is achieved on a simple gradient method. The mobile phase A contains a mixture of sodium perchlorate buffer pH 3.2 (0.053M): acetonitrile in the ratio 90:10, v/v, and mobile B contains a mixture of sodium perchlorate buffer pH 3.2 (0.053M): acetonitrile in the ratio 20:80, v/v. The flow rate is 0.6 mL min?1 and the column temperature is maintained at 55°C.The gradient program (T/%B) is set as 0/5, 1.2/5, 1.6/40, 4/40, 4.1/5 and 4.5/5. The detector wavelength is 271 nm for Hydrochlorothiazide and Telmisartan and 237 nm for Amlodipine. The retention times of Telmisartan, Amlodipine, and Hydrochlorothiazide are 3.6 minutes, 3.2 minutes and 0.9 minutes; respectively. The total runtime for the separation of the three active compounds and their degradation products is 4.5 minutes. The described method is validated with respect to system suitability, specificity, linearity, precision and accuracy. The precision of the assay method is evaluated by carrying out six independent assays of T, A and H (0.032 mg mL?1 of T, 0.004 mg mL?1 of A, 0.01 mg mL?1 of H). The accuracy of the method is evaluated in triplicate at three concentration levels, i.e. 50%, 100% and 150% of target test concentration (0.64 mg mL?1 of T, 0.08 mg mL?1 of A, 0.2 mg mL?1 of H). The described method is linear over the range, 16 to 48 ?g mL?1 for T, 2 to 6 ?g mL?1A and 5 to 15 ?g mL?1 for H. The method is fast and suitable for high-throughput analysis allowing the analysis of about 250 samples per working day.

Nalwade, Santaji; Ranga Reddy, Vangala; Durga Rao, Dantu; Koteswara Rao, Inabathina

2011-01-01

338

Posture control development in children aged 2–7 years old, based on the changes of repeatability of the stability indices  

Microsoft Academic Search

One of the most common problems encountered in posture control studies is relatively poor repeatability of postural stability measures based on the COP (center of pressure) time-series which results from the inherent variability of postural control. The repeatability of the data reflecting the postural control mechanisms in young children is still not well enough explained. The differences between of the

Ma?gorzata Sobera; Bo?ena Siedlecka; Ma?gorzata Syczewska

2011-01-01

339

Internet Addiction: Stability and Change  

ERIC Educational Resources Information Center

|This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability

Huang, Chiungjung

2010-01-01

340

Internet Addiction: Stability and Change  

ERIC Educational Resources Information Center

This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability

Huang, Chiungjung

2010-01-01

341

Investigation of folic acid stability in fortified instant noodles by use of capillary electrophoresis and reversed-phase high performance liquid chromatography.  

PubMed

A single enzyme treatment with alpha-amylase, prior to the quantification of added folic acid (FA) in fortified instant fried Asian noodles with analysis performed by capillary zone electrophoresis (CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection, is described. The method was validated and optimized for capillary electrophoresis (CE) with separation achieved using a 8 mM phosphate-12 mM borate run buffer with 5% MeOH at pH 9.5. FA was well separated from matrix components with nicotinic acid (NA) employed as an internal standard. In a comparative study, separation of FA was performed using HPLC with a mobile phase consisting of 27% MeOH (v/v) in aqueous potassium phosphate buffer (3.5 mM KH(2)PO(4) and 3.2 mM K(2)HPO(4)), pH 8.5, and containing 5 mM tetrabutylammonium dihydrogen phosphate as an ion-pairing agent. For both methods, excellent results were obtained for various analytical parameters including linearity, accuracy and precision. The limit of detection was calculated to be 2.2 mg/L for CE without sample stacking and 0.10 mg/L with high performance liquid chromatography (HPLC). Sample extraction involved homogenization and enzymatic extraction with alpha-amylase. Results indicated that FA was stable during four main stages of instant fried noodle manufacturing (dough crumbs, cut sheets, steaming and frying). PMID:18930464

Hau Fung Cheung, Rodney; Morrison, Paul D; Small, Darryl M; Marriott, Philip J

2008-10-04

342

A Novel Approach to the Surgical Treatment of Lumbar Disc Herniations: Indications of Simple Discectomy and Posterior Transpedicular Dynamic Stabilization Based on Carragee Classification  

PubMed Central

Surgery of lumbar disc herniation is still a problem since Mixter and Barr. Main trouble is dissatisfaction after the operation. Today there is a debate on surgical or conservative treatment despite spending great effort to provide patients with satisfaction. The main problem is segmental instability, and the minimally invasive approach via microscope or endoscope is not necessarily appropriate solution for all cases. Microsurgery or endoscopy would be appropriate for the treatment of Carragee type I and type III herniations. On the other hand in Carragee type II and type IV herniations that are prone to develop recurrent disc herniation and segmental instability, the minimal invasive techniques might be insufficient to achieve satisfactory results. The posterior transpedicular dynamic stabilization method might be a good solution to prevent or diminish the recurrent disc herniation and development of segmental instability. In this study we present our experience in the surgical treatment of disc herniations.

Ozer, A. F.; Keskin, F.; Oktenoglu, T.; Suzer, T.; Ataker, Y.; Gomleksiz, C.; Sasani, M.

2013-01-01

343

Development of rapid and robust stability-indicating method for analysis of ziprasidone (hydrochloride and freebase) as drug substance and in medicines by UPLC.  

PubMed

Ultra Performance Liquid Chromatography (UPLC) was employed to develop a rapid and robust method for the analysis of ziprasidone, both as a drug substance and in the final dosage forms. The application of this method in stability analyses was verified. Tests were carried out according to ICH/FDA guidelines, European Pharmacopeia, and United States Pharmacopeia rules, which take into account factors such as specificity, linearity, accuracy, and precision. Separation was performed on an Acquity UPLC BEH phenyl 1.7-microm column with a simple mobile phase, consisting of acetonitrile and water adjusted to pH 2.0 with ortho-phosphoric acid. Using this mobile phase and gradient elution, the separation was completed within 5 min. This method is very sensitive, and allows performing simultaneous identification, assay, and determination of impurities and related substances in one injection. PMID:23061276

Zakowiecki, Daniel; Cal, Krzysztof

344

The Use of the Sustainable Development Multi-Indicators for Evaluating the Stabilization in some new Rural Communities in Desert Areas of Egypt  

Microsoft Academic Search

1. Abstract One of the most important indicators to illustrate the success of the emigration policy in Egypt, is the increase of new rural communities in the Egyptian desert. Accordingly, the population inclination to move from the overpopulated Nile valley to the Egyptian desert increases, developing it, creating more job opportunities and generating income for the individual. The ability of

W. F. ERIAN

345

Determination of Cefixime by a Validated Stability-Indicating HPLC Method and Identification of its Related Substances by LC-MS/MS Studies  

PubMed Central

Cefixime is an important cephalosporin antibiotic that easily decomposes and releases different related substances in preparation and storage steps. The objective of the current study was to develop a simple, precise, and accurate isocratic liquid chromatography (LC) method for the determination of cefixime in the presence of its related substances generated from thermal stress in the bulk drug. The chromatographic conditions were comprised of a reversed-phase C18 column (4.6 × 250 mm, 5 ?m) with a mobile phase composed of water: acetonitrile (85:15 v/v, with 0.5% formic acid) and ultraviolet detection (UV). Some thermal degradation products were identified using a proposed liquid chromatography-mass spectrometry method. Five peaks (A, B, C, D, and E impurities based on British Pharmacopoeia) were known and a few unknown peaks appeared in the thermal stress solution of cefixime. The linear regression analysis data for the calibration plot of the LC-UV method showed a good linear relationship in the concentration range 0.9–1000.0 ?g mL?1. The recovery of the optimized method was between 94.6 and 98.4% and the inter- and intra-day relative standard deviations were less than 3.3%. The obtained results shown in the LC-UV proposed method can be conveniently used in a quality control laboratory for routine analysis of cefixime for the assay and related substances, as well as for the evaluation of stability samples of bulk drugs.

Talebpour, Zahra; Pourabdollahi, Hakimeh; Rafati, Hasan; Abdollahpour, Asem; Bashour, Yusef; Aboul-Enein, Hassan Y.

2013-01-01

346

Bioconversion of rice straw and certain agro-industrial wastes to amendments for organic farming systems: 1. Composting, quality, stability and maturity indices.  

PubMed

The microbiological and physicochemical parameters were monitored for 12 weeks during composting of five piles (1.5 x 1.0 x 0.80 m(3)) containing mainly rice straw, soybean residue and enriched with rock phosphate. Two treatments were inoculated with buffalo's manure or composite inoculum, two were supplemented with vinasse and inoculated with either the composite inoculum or with both, the last one was served as a control. Four typical phases of composting were observed during the bioprocess: short initial mesophilic phase followed by, thermophilic, cooling and maturation phases. Physicochemical changes confirmed the succession of microbial populations depending on the temperature of each phase in all treatments. Intense microbial activities led to organic matter mineralization and simultaneously narrow C/N ratios. Inoculation of composting mixtures enhanced the biodegradation of recalcitrant substances. The duration of exposure to a temperature above 55 degrees C for at least 16 consecutive days was quite enough to sanitize the produced composts. After 84 days, all composts reached maturity as indicated by various parameters. PMID:20335032

Rashad, Ferial M; Saleh, Walid D; Moselhy, Mohamed A

2010-03-23

347

Internet addiction: stability and change  

Microsoft Academic Search

This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level\\u000a stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate\\u000a students from end of freshman year to end of junior year. Convergent findings revealed stability rather than change in Internet\\u000a addiction. Prior academic self-concept was not associated with individual-level stability,

Chiungjung Huang

2010-01-01

348

A validated stability-indicating RP-LC method for the simultaneous determination of amlodipine and perindopril in tablet dosage form and their stress degradation behavior under ICH-recommended stress conditions.  

PubMed

A stability-indicating RP-LC assay method was developed for the simultaneous determination of the cardiovascular drugs amlodipine and perindopril in the presence of degradation products generated from forced decomposition studies. The developed method is applicable for the determination of related substances in bulk drugs and simultaneous assay in a tablet pharmaceutical dosage form. Separation of the drugs and their degradation products was obtained using an RP Waters Spherisorb ODS1 column (250 x 4.6 mm id, 5 pm particle size) with the mobile phase acetonitrile-water (30 + 70, v/v) containing 15 mM phosphoric acid. The pH of the mobile phase was adjusted to 5.0. A flow rate of 1.2 mL/min was used for the separations, with detection at 215 nm. The chromatographic separation was performed at a column temperature of 45 degrees C. Atenolol was chosen as the internal standard. Amlodipine and perindopril were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Degradation studies showed that both compounds were degraded under these stress conditions. The method was found to be stability-indicating and can be used for the routine analysis of amlodipine and perindopril in the studied combined tablet dosage form. PMID:24000747

Gumustas, Mehmet; Ozkan, Sibel A

349

Plasma Stabilization by Feedback  

NASA Astrophysics Data System (ADS)

A simple model is discussed which illustrates the general features of plasma stabilization by an external feedback system. This indicates that different phase relations in the feedback loop are needed to stabilize differing classes of electrostatic instability.

Taylor, J. B.; Lashmore-Davies, C. N.

1970-06-01

350

Environmental Indicators  

NSDL National Science Digital Library

Environment Canada has developed a set of environmental indicators that are easily measurable and provide useful clues on the state of the environment. This Web site provides a listing of those indicators that Environment Canada monitors. For each indicator, there is a detailed description of the environmental indicator, how it relates to larger environmental problems, and what is being done to reduce the threat. A number of Web links are provided for further information on each indicator.

2007-12-12

351

Development of a stability-indicating LC method for determination of a synthetic chalcone derivative in a nanoemulsion dosage form and identification of the main photodegradation product by LC-MS.  

PubMed

This study aimed to develop and validate a stability indicating LC for the determination of 5-(2-benzoylethenyl)-N-benzyl-2 methoxybenzenesulfonamide (SCD - a synthetic chalcone derivative), and evaluate the degradation profile of the compound under different stress conditions recommended by International Conference on Harmonization (ICH). Chromatographic separation was performed on a silica C18 column, methanol-water mobile phase 70:30 (v:v), pH 5.0 adjusted with the addition of trifluoroacetic acid (TFA) at a flow rate of 1.0 mL min(-1); detection by UV absorption at 330 nm. The method was validated for linearity, precision, accuracy, robustness and specificity. The SCD was subjected to forced degradation and peak photodegradation product was well separated from the pure substance, with retention times significantly different, indicating the specificity of the method. Second-order degradation kinetics of SCD was observed under photodegradation and base-induced degradation. In order to identify the product formed under photodegradation, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed. These results indicate that the method can be successfully used in order to assay SCD in a nanoemulsion dosage form, and that this formulation has a protective effect over SCD degradation. PMID:22884784

Mattos, Cristiane B; Deponti, Vânia B; Barreto, Fabiano; Simões, Cláudia M O; Andrighetti-Frohner, Carla R; Nunes, Ricardo J; Steindel, Mário; Teixeira, Helder F; Koester, Letícia S

2012-07-27

352

ECOLOGICAL INDICATORS  

EPA Science Inventory

An international symposium on ecological indicators was developed to explore both the potential of ecological indicators and the issues surrounding their development and implementation. his symposium presented state-of-the-science information on the identification, application re...

353

Complexity in Estimation of Esomeprazole and its Related Impurities' Stability in Various Stress Conditions in Low-Dose Aspirin and Esomeprazole Magnesium Capsules  

PubMed Central

A complex, sensitive, and precise high-performance liquid chromatographic method for the profiling of impurities of esomeprazole in low-dose aspirin and esomeprazole capsules has been developed, validated, and used for the determination of impurities in pharmaceutical products. Esomeprazole and its related impurities’ development in the presence of aspirin was traditionally difficult due to aspirin’s sensitivity to basic conditions and esomeprazole’s sensitivity to acidic conditions. When aspirin is under basic, humid, and extreme temperature conditions, it produces salicylic acid and acetic acid moieties. These two byproducts create an acidic environment for the esomeprazole. Due to the volatility and migration phenomenon of the produced acetic acid and salicylic acid from aspirin in the capsule dosage form, esomeprazole’s purity, stability, and quantification are affected. The objective of the present research work was to develop a gradient reversed-phase liquid chromatographic method to separate all the degradation products and process-related impurities from the main peak. The impurities were well-separated on a RP8 column (150 mm × 4.6mm, X-terra, RP8, 3.5?m) by the gradient program using a glycine buffer (0.08 M, pH adjusted to 9.0 with 50% NaOH), acetonitrile, and methanol at a flow rate of 1.0 mL min?1 with detection wavelength at 305 nm and column temperature at 30°C. The developed method was found to be specific, precise, linear, accurate, rugged, and robust. LOQ values for all of the known impurities were below reporting thresholds. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation in the presence of aspirin. The developed RP-HPLC method was validated according to the present ICH guidelines for specificity, linearity, accuracy, precision, limit of detection, limit of quantification, ruggedness, and robustness.

Reddy, Palavai Sripal; Hotha, Kishore Kumar; Sait, Shakil

2013-01-01

354

Chemical Indicators.  

ERIC Educational Resources Information Center

|This science sourcebook was written for intermediate grade teachers to provide guidance in teaching a specially developed unit on chemical indicators. Directions and suggestions for guiding student science activities are given. Some of the activities concern soil testing, crystals, and household powders such as sugar and salt. A list of necessary…

Prombain, Dorothy R.; And Others

355

Development and Validation of a RP-HPLC Method for Estimation of Montelukast Sodium in Bulk and in Tablet Dosage Form  

PubMed Central

The present work describes a simple, precise and accurate HPLC method for estimation of montelukast sodium in bulk and in tablet dosage form. The separation was achieved by using octadecylsilane column (C18) and acetonitrile:1 mM sodium acetate adjusted to pH 6.3 with acetic acid in proportion of 90:10 v/v as mobile phase, at a flow rate of 1.5 ml/min. Detection was carried out at 285 nm. The retention time of montelukast sodium was found to be 3.4 min. The limit of detection was found 1.31 µg/ml and limit of quantification 3.97 µg/ml. The accuracy and reliability of the proposed method was ascertained by evaluating various validation parameters like linearity (1-100 µg/ml), precision, accuracy and specificity according to ICH guidelines. The proposed method provides an accurate and precise quality control tool for routine analysis of montelukast sodium in bulk and in tablet dosage form.

Singh, R. M.; Saini, P. K.; Mathur, S. C.; Singh, G. N.; Lal, B.

2010-01-01

356

ESI-MS and MS/MS identification of the first ceramide analogues of fumonisin B1 mycotoxin from a Fusarium verticillioides culture following RP-HPLC separation.  

PubMed

Following the earlier detection of six new esterified fumonisin B1 (EFB1) isomers containing three acyl groups in a Fusarium verticillioides-inoculated rice culture, it was assumed that linoleic, palmitic or oleic acid esterifies one of the free OH groups on the fumonisin backbone. On the basis of the results of our recent investigations we now propose that these EFB1 isomers are actually 3-O- and 5-O-acyl derivatives of FB1 (3-O-linoleoyl-FB1, 5-O-linoleoyl-FB1, 3-O-palmitoyl-FB1, 5-O-palmitoyl-FB1, 3-O-oleoyl-FB1 and 5-O-oleoyl-FB1). A F. verticillioides strain was identified that produced not only O-acyl-FB1 isomers, but also low amounts of three N-acyl derivatives (N-linoleoyl-FB1, N-palmitoyl-FB1 and N-oleoyl-FB1), which eluted from the HPLC column after the six O-acyl compounds and in the same sequence as for the O-acyl compounds. The characteristic positive and negative ESI-MS/MS spectra obtained after solid-phase extraction of the culture extract facilitated identification of these N-acyl-FB1 derivatives. The biosynthesis of N-palmitoyl-FB1 by F. verticillioides was verified by spiking the culture extract with synthetic N-palmitoyl-FB1. This is the first report of the separation and mass spectrometric identification of the six O-acyl- and three N-acyl-FB1 derivatives extracted from a F. verticillioides culture. PMID:23837460

Bartók, T; Szécsi, A; Juhász, K; Bartók, M; Mesterházy, A

2013-07-10

357

Preparation and Characterization of SiO 2 \\/SiO 2 Core–Shell Microspheres as RP-HPLC Stationary Phase  

Microsoft Academic Search

Novel SiO2\\/SiO2 core–shell monodisperse silica spheres for high-performance liquid chromatography packing materials are prepared by the layer-by-layer\\u000a self-assembly technique. The core–shell silica spheres consist of micrometer-sized porous silica spheres as the core and a\\u000a thin mesoporous silica shell formed from multilayer nanometer-sized silica particles. In addition, a reversed-phase packing\\u000a by bonding octadecyltrichlorosilane on SiO2\\/SiO2 particles through alkyl-modified method is prepared

Q. Liu; L.-T. Wang; S.-Q. Dong; Zh.-X. Zhang; L. Zhao

358

Development and validation of RP-HPLC method for simultaneous estimation of nimesulide, phenylephrine hydrochloride, chlorpheniramine maleate and caffeine anhydrous in pharmaceutical dosage form.  

PubMed

In this study, a simple, specific and accurate reverse phase high performance liquid chromatographic method was developed for the simultaneous determination of nimesulide (NS), phenylephrine hydrochloride (PE), chlorpheniramine maleate (CPM) and caffeine anhydrous (CF) in pharmaceutical dosage forms. A reversed phase Hypersil phenyl column (4.6 mm x 25 cm) with mobile phase having pH 5.5 consisting of methanol and buffer (55:45, v/v) was used. The flow rate was 1.0 mL per minute and the effluents were monitored at 214 nm. The retention times of all the drugs were found to be 7.47 min (NS), 3.944 min (PE), 4.55 min (CF) and 17.15 min (CPM), respectively. The linearity for all the drugs was obtained in the range of 300-800 microg/mL (NS), 15-32 microg/mL (PE), 16-32 microg/mL (CPM) and 30-180 microg/mL (CF), respectively. The results of analysis have been well validated according to guidelines of International Conference of Harmonisation of technical requirements for registration of pharmaceuticals for human use. The method was found to be simple, precise, economical, less time consuming and reproducible. Hence, the suggested procedure could be used for the determination of all the four drugs in commercial preparations. PMID:23285660

Kumar, Ashok; Sharma, Rishbha; Nair, Anroop; Saini, Gautam

359

Analysis of amino acids as DABS-derivatives with a sensitivity to the femtomole level using RP-HPLC narrow-bore columns  

Microsoft Academic Search

In this paper we report the complete separation of amino acids as DABS-derivatives using a 3µm Supelcosil LC-18 (25 cm × 2.1 mm I.D.) narrowbore column. The system described makes it possible to perform the analysis of DABS-amino acids with a sensitivity to the femtomole level. We have also studied the conditions necessary for using the narrow-bore columns for routine

V. Stocchi; F. Palma; G. Piccoli; B. Biagiarelli; M. Magnani; L. Masat; L. Cucchiarini

1992-01-01

360

Influence of Coverage Density of Chemically Bonded C18 Phases on the Retention Data of Substances Eluted in Dead Volume During RP HPLC Analysis  

Microsoft Academic Search

In this paper there are discussed the results of studies relating to the effect of controlled coverage density (?RP) of silica gel surface with c18 chemically bonded phase (CBP) on the retention of some test substances (H2o, D2o, CH3OH, CH3OD) most often used to the determination of dead volume (Vo). In the consideration it has regarded the influence of many

Boguslaw Buszewski; Miroslaw Kulpa

1993-01-01

361

Effect of High Density Poly (Vinyl Octadecanoate) Grafted Silica Stationary Phase on Physiochemical Properties and Shape Selectivity Enhancement of Polycyclic Aromatic Hydrocarbons (PAHs) in RP-HPLC  

Microsoft Academic Search

High dense Poly (vinyl octadecanoate) grafted silica stationary phase (Sil-from-VOD) have been prepared by radical chain-transfer “grafting from” approach. Another Poly (vinyl octadecanoate) grafted silica stationary phase (Sil-to-VOD) was prepared by conventional one-step telomerization (“grafting to”) method. Both phases were characterized qualitatively and quantitatively. Thermogravimetric analysis and elemental analysis data showed that Sil-from-VOD have higher grafting density as compared with

Ashequl A. Rana; Makoto Takafuji; Hirotaka Ihara

2012-01-01

362

A Validated RP-HPLC Method for the Estimation of Lapatinib in Tablet Dosage form using Gemcitabine Hydrochloride as an Internal Standard.  

PubMed

A simple, selective, rapid, precise and economical reverse-phase high-performance liquid chromatography method has been developed for the determination of lapatinib in tablet using gemcitabine hydrochloride as an internal standard. Chromatography was carried out on an ODS C-18 RP column (4.6 mm i.d. ×250 mm) using a mixture of acetonitrile and water (50:50 v/v) as the mobile phase at a flow rate of 1.0 ml/min. The drug was monitored at 232 nm. The retention times for lapatinib and gemcitabine hydrochloride were found to be 4.25±0.05 and 6.10±0.05 min, respectively. The method produced linear responses in the concentration range of 2-60 ?g/ml of lapatinib. The limit of detection and limit of quantitation were 0.265 and 0.884 ?g/ml, respectively. PMID:23798787

Kumar, K K; Nagoji, K E V; Nadh, R V

2012-11-01

363

Simultaneous Estimation of Amlodipine Besylate and Indapamide in a Pharmaceutical Formulation by a High Performance Liquid Chromatographic (RP-HPLC) Method  

PubMed Central

An isocratic reversed-phase liquid chromatograpic assay method was developed for the quantitative determination of amlodipine besylate (AML) and indapamide (IND) in combined dosage form. A Brownlee C-18, 5 ?m column with a mobile phase containing 0.02 M potassium dihydrogen phosphate–methanol (30+70, v/v) total pH-adjusted to 3 using o-phosphoric acid was used. The flow rate was 1.0 mL min?1 and effluents were monitored at 242 nm. The retention times of amlodipine besylate and indapamide were 5.9 min and 3.6 min, respectively. The proposed method was validated with respect to linearity, accuracy, precision, and robustness. The method was successfully applied to the estimation of amlodipine besylate and indapamide in combined tablet dosage forms.

Patel, Deval B.; Mehta, Falgun A.; Bhatt, Kashyap K.

2012-01-01

364

A Validated RP-HPLC Method for the Estimation of Lapatinib in Tablet Dosage form using Gemcitabine Hydrochloride as an Internal Standard  

PubMed Central

A simple, selective, rapid, precise and economical reverse-phase high-performance liquid chromatography method has been developed for the determination of lapatinib in tablet using gemcitabine hydrochloride as an internal standard. Chromatography was carried out on an ODS C-18 RP column (4.6 mm i.d. ×250 mm) using a mixture of acetonitrile and water (50:50 v/v) as the mobile phase at a flow rate of 1.0 ml/min. The drug was monitored at 232 nm. The retention times for lapatinib and gemcitabine hydrochloride were found to be 4.25±0.05 and 6.10±0.05 min, respectively. The method produced linear responses in the concentration range of 2-60 ?g/ml of lapatinib. The limit of detection and limit of quantitation were 0.265 and 0.884 ?g/ml, respectively.

Kumar, K. K.; Nagoji, K. E. V.; Nadh, R. V.

2012-01-01

365

Rapid determination of total solanesol in tobacco leaf by ultrasound-assisted extraction with RP-HPLC and ESI-TOF\\/MS  

Microsoft Academic Search

A reliable and rapid method based on high-performance liquid chromatography (HPLC-UV) and positive ion electrospray-time of flight mass spectrometry (ESI-TOF\\/MS) has been developed for the characterization and quantification of solanesol in extracts of tobacco leaves from different sources. The solanesol was extracted from tobacco leaf via saponification and ultrasonic-assist extraction, and the extraction conditions were optimized. The HPLC conditions are

Junhui Chen; Xianping Liu; Xiaoqin Xu; Frank Sen-Chun Lee; Xiaoru Wang

2007-01-01

366

Development and validation of a RP-HPLC method for the estimation of netilmicin sulfate and its related substances using charged aerosol detection.  

PubMed

Netilmicin is a semi-synthetic aminoglycoside antibiotic used against a broad spectrum of Gram-negative bacteria. A reversed-phase high-performance liquid chromatographic method has been developed to determine the composition of netilmicin sulfate and to estimate its related substances without pre- or post-column derivatization. A UV detector cannot be used to detect low levels of known and unknown related substances of netilmicin, as it has only a weak UV chromophore. A charged aerosol detector was used instead to obtain the high sensitivity that was necessary for the intended purpose of the method. This method can separate all related substances of netilmicin. A (10 cm x 4.6 mm) pentafluorophenyl high-performance liquid chromatographic column from Restek was used with a mobile phase consisting of (A) pentafluoropropionic acid-water-acetonitrile (0.1:96:4, v/v/v) and (B) trifluoroacetic acid-water-acetonitrile (1:96:4, v/v/v). PMID:20819288

Joseph, Arul; Patel, Shrina; Rustum, Abu

2010-08-01

367

RP-HPLC measurement and quantitative structure-property relationship analysis of the n-octanol-water partitioning coefficients of selected metabolites of polybrominated diphenyl ethers  

Microsoft Academic Search

Environmental context. Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants and numerous studies have demonstrated a marked increase in the levels of PBDEs in human biological tissues and fluids, especially breast milk. How PBDEs are transported through the environment, taken up by biota, transported across membranes, and metabolised depends strongly on such fundamental properties as lipophilicity (log KOW). However, very

368

Method development and validation for the simultaneous determination of meloxicam and pridinol mesylate using RP-HPLC and its application in drug formulations  

Microsoft Academic Search

A simple and reliable reversed-phase high-perfomance liquid chromatographic method has been developed and validated for the simultaneous determination of meloxicam and pridinol mesylate in their synthetic mixtures and combined tablet formulations. Both drugs were separated on a 250mm×4.6mm C18 column packed with 5?m particles. The mobile phase, optimized through an experimental design, was a 51:9:40 (v\\/v\\/v) mixture of methanol, isopropanol

Silvana E. Vignaduzzo; Patricia M. Castellano; Teodoro S. Kaufman

2008-01-01

369

Method development and validation for the simultaneous determination of meloxicam and pridinol mesylate using RP-HPLC and its application in drug formulations.  

PubMed

A simple and reliable reversed-phase high-perfomance liquid chromatographic method has been developed and validated for the simultaneous determination of meloxicam and pridinol mesylate in their synthetic mixtures and combined tablet formulations. Both drugs were separated on a 250 mm x 4.6mm C18 column packed with 5 microm particles. The mobile phase, optimized through an experimental design, was a 51:9:40 (v/v/v) mixture of methanol, isopropanol and 50mM potassium phosphate buffer (pH 5.9), pumped at a flow rate of 1.0 ml min(-1). UV detection was performed at 225 nm. The method was validated in the sample concentration ranges of 33.7-61.8 mg l(-1) for meloxicam and 8.8-16.8 mg l(-1) for pridinol mesylate, where it demonstrated good linearity with r=0.9989 and 0.9987 (n=15), respectively. The assay was shown to be repeatable at concentration levels of 70%, 100% and 130%, with relative standard deviation values of 1.09% and 0.82% for meloxicam and pridinol, respectively. For independent 100% level samples, the intra-day precision was 0.4% and 1.0% while the intermediate precision was 0.7% and 1.0% for the drugs. The method demonstrated to be robust, resisting to small deliberate changes in pH, flow rate and composition (organic:aqueous ratio) of the mobile phase. The LOD values were 0.22 and 0.20 mg l(-1), while the LOQ were 1.7 and 1.1 mg l(-1), for meloxicam and pridinol, respectively. The applicability of the method was demonstrated by determining the drug content of two commercial pharmaceutical formulations, where it exhibited good performance. PMID:17961953

Vignaduzzo, Silvana E; Castellano, Patricia M; Kaufman, Teodoro S

2007-09-15

370

Economic Indicators  

NSDL National Science Digital Library

Both scholars and those with a penchant for statistics will want to bookmark this fine website created and maintained by the federal government. The site provides monthly compilations of economic indicators covering prices, wages, production, business activity, purchasing power, credit, money, and Federal finance. Visitors can use the search engine to type in their desired terms, or they can browse every month from January 1998 forward via a series of drop down tabs. For those who might be looking for more specific data, the "Search Tips" feature is quite useful. The site also contains links to the Federal Reserve Archival System for Economic Research (FRASER), which contains economic indicators back to 1948. Overall, the site will be a real boon to those looking for high quality, accurate information regarding current and past economic trends and patterns in the United States.

371

Comparison of Procedures for Resveratrol Analysis in Beer: Assessment of Stilbenoids Stability through Wort Fermentation and Beer Aging  

Microsoft Academic Search

J. Inst. Brew. 114(2), 143-149, 2008 Three resveratrol extraction procedures were compared in beer. Two-step pre-cleaning with toluene and cyclohexane allows 76% trans-resveratrol recovery by solid-phase extraction (SPE) be- fore RP-HPLC-MS\\/MS analysis. This procedure proved much more efficient than liquid\\/liquid extraction, which requires sol- vents that are too hydrophobic for stilbenoids. SPME-GC-MS, where the main limiting factor is non-reproducibility from

Vesna Jerkovic; Fanny Nguyen; Aurore Timmermans; Sonia Collin

372

Social indicators.  

PubMed

The notions of social indicators and social accounting, expressed by analogy with the national economic accounts, generated excitement in the 1960's, and the interest continues to grow if we may judge from governmental activity and the publication of programmatic and research papers. But the concepts which focused much of the early enthusiasm gave exaggerated promise of policy applications and provided an unproductive basis for research. The essential theoretical prerequisites for developing a system of social accounts-defining the variables and the interrelationships among them-are missing. It is now realized that evaluation research, particularly experimentation, must be relied on for evaluation of government programs. Through the development and analysis of descriptive time series and the modeling of social processes, we will be able to describe the state of the society and its dynamics and thus improve immensely our ability to state problems in a productive fashion, obtain clues as to promising lines of endeavor, and ask good questions. But these activities cannot measure program effectiveness. Finally, we must be skeptical about definitions of the social indicators enterprise which confine it to social engineering efforts. The issue is not whether social indicators are useful for policy but, rather, how this usefulness comes about. The interest in social indicators has stimulated a revival of interest in quantitative, comparative, social analysis (60), in the analysis of social change, in conceptual and measurement work on such topics as prejudice, crime, and learning, and in the development of models of social processes. The fruit of these efforts will be more directly a contribution to the policy-maker's cognition than to his decisions. Decision emerges from a mosaic of inputs, including valuational and political, as well as technical components. The work we have described deals with only one type of input; it is a contribution to the intellectual mapping process which is essential if decisionmakers are to know what it is that has changed, and how the change has come about. The character of the scientific contribution will, of course, vary with the subject. Models of a few social processes, such as those pertaining to social mobility and population dynamics, are in varying degrees of development and application. But for many other areas, the appropriate question is not "How does it work?" but "How has it changed?" And for still others, the question is "What is it?" The work of the Berkeley sociologists on the measurement of prejudice illustrates very well the interaction between measurement and conceptual development that is required to answer the question "What is it?" In the present state of work on this topic, the appropriate hypotheses are not so much concerned with the relationships of the phenomenon to others in a causal system, as they are with the nature of the phenomenon itself. What is being tested is a set of propositions that certain ways of thinking about social reality are productive, that a phenomenon as conceptualized is "there" in the reality being measured, and that the investigators have found a set of measures which tell us something we need to know about changes in the society. It is apparent that many different types of work go on under the rubric of social indicators. What is important is that the field be seen as an arena for long-term development, as an effort of social scientists to push forward developments in concepts and in methodology that promise payoffs to both science and public policy.Such a view is reflected in the funding commitments of the National Science Foundation, which supports many of the research projects reported above. What we may expect of this work was aptly stated by Duncan (61): The value of improved measures of social change ... is not that they necessarily resolve theoretical issues concerning social dynamics or settle pragmatic issues,of social policy, but that they may permit those issues to be argued more produ

Sheldon, E B; Parke, R

1975-05-16

373

Probabilistic evaluation of voltage stability  

Microsoft Academic Search

This paper presents a contingency enumeration based approach to evaluate the voltage stability of a power system. The proposed approach, includes the selection and evaluation of contingencies, the classification of contingencies according to selected failure criteria and the accumulation of voltage stability indices. Voltage stability is quantified in the form of indices such as the probability and frequency of voltage

S. Aboreshaid; R. Billinton

1999-01-01

374

Crisis stability of a submarine deterrent.  

National Technical Information Service (NTIS)

Without defenses, stability indices fall monotonically as the number of submarine-launched ballistic missiles (SLBMs) is reduced. For few SLBMs, the favorable stability properties of the survivable SLBMs are masked by the unfavorable stability properties ...

G. H. Canavan

1992-01-01

375

New chromatographic and biochemical strategies for quick preparative isolation of tRNA  

PubMed Central

A combination of hydrophobic chromatography on phenyl-Sepharose and reversed phase HPLC was used to purify individual tRNAs with high specific activity. The efficiency of chromatographic separation was enhanced by biochemical manipulations of the tRNA molecule, such as aminoacylation, formylation of the aminoacyl moiety and enzymatic deacylation. Optimal combinations are presented for three different cases. (i) tRNAPhe from Escherichia coli. This species was isolated by a combination of low pressure phenyl-Sepharose hydrophobic chromatography with RP-HPLC. (ii) tRNAIle from E.coli. Aminoacylation increases the retention time for this tRNA in RP-HPLC. The recovered acylated intermediate is deacylated by reversion of the aminoacylation reaction and submitted to a second RP-HPLC run, in which deacylated tRNAIle is recovered with high specific activity. (iii) tRNAiMet from Saccharomyces cerevisiae. The aminoacylated form of this tRNA is unstable. To increase stability, the aminoacylated form was formylated using E.coli enzymes and, after one RP-HPLC step, the formylated derivative was deacylated using peptidyl-tRNA hydrolase from E.coli. The tRNAiMet recovered after a second RP-HPLC run exhibited electrophoretic homogeneity and high specific activity upon aminoacylation. These combinations of chromatographic separation and biochemical modification can be readily adapted to the large-scale isolation of any particular tRNA.

Cayama, Edmundo; Yepez, Antonio; Rotondo, Fernando; Bandeira, Eduardo; Ferreras, Ana C.; Triana-Alonso, Francisco J.

2000-01-01

376

Stability of arsenic peptides in plant extracts: off-line versus on-line parallel elemental and molecular mass spectrometric detection for liquid chromatographic separation  

Microsoft Academic Search

The instability of metal and metalloid complexes during analytical processes has always been an issue of an uncertainty regarding\\u000a their speciation in plant extracts. Two different speciation protocols were compared regarding the analysis of arsenic phytochelatin\\u000a (AsIIIPC) complexes in fresh plant material. As the final step for separation\\/detection both methods used RP-HPLC simultaneously\\u000a coupled to ICP-MS and ES-MS. However, one

Katharina Bluemlein; Andrea Raab; Jörg Feldmann

2009-01-01

377

Geology and slope stability in selected parts of The Geysers geothermal resources area: a guide to geologic features indicative of stable and unstable terrain in areas underlain by Franciscan and related rocks  

SciTech Connect

The results of a 4-month study of various geologic and topographic features related to the stability of Franciscan terrain in The Geysers GRA are presented. The study consisted of investigations of geologic and topographic features, throughout The Geysers GRA, and geologic mapping at a scale of 1:12,000 of approximately 1500 acres (600 hectares) of landslide terrain within the canyon of Big Sulphur Creek in the vicinity of the Buckeye mine (see plate 1). The area mapped during this study was selected because: (1) it is an area of potential future geothermal development, and (2) it illustrates that large areas mapped as landslides on regional scales (McLaughlin, 1974, 1975b; McNitt, 1968a) may contain zones of varying slope stability and, therefore, should be mapped in more detail prior to development of the land.

Bedrossian, T.L.

1980-01-01

378

Stabilized Vegas  

Microsoft Academic Search

We show that the current TCP Vegas algorithm can become unstable in the presence of network delay and propose a modification that stabilizes it. The stabilized Vegas remains completely source-based and can be implemented without any network support. We suggest an incremental deployment strategy for stabilized Vegas when the network contains a mix of links, some with active queue management

Hyojeong Choe; Steven H. Low

2003-01-01

379

Facet Problems: A Surgical Indication?  

Microsoft Academic Search

\\u000a The apophyseal facet joints of the spine are typical diarthrodial joints located in the posterior aspect of the functional\\u000a spinal unit or “three-joint complex”. They provide motion and stability and protect the neural structures. Indeed, facet problems\\u000a are a surgical indication, mainly after acute trauma with facet dislocation. However, in the absence of “red flags”, surgical\\u000a indications are less clear.

F. Pellisé

380

Slope stability and stabilization methods  

SciTech Connect

Slope stability can be a major problem during the construction of surface facilities. Cutting into existing ground disturbs the mechanics of the surrounding area, which can result in landslides and rock falls. This practical reference gives you the comprehensive information you need for slope stability analysis, suitable methods of analysis with and without the use of computers, and examples of common stability problems and stabilization methods for cuts and fills. It includes detailed discussions of methods used in slope stability analysis, including the Ordinary Method of Slices, Simplified Janbu Method, Simplified Bishop Method, Spencer`s Method, other limit equilibrium methods, numerical methods, total stress analysis, effective stress analysis, and the use of computer programs to solve problems. Chapters include: General Slope Stability Concepts; Engineering Geology Principles; Groundwater Conditions; Geologic Site Exploration; Laboratory Testing Interpretation; Slope Stability Concepts; Slope Stabilization Methods; and Design, Construction and Maintenance.

Abramson, L.W.; Lee, T.S.; Boyce, G.M.; Sharma, S.S.

1995-12-01

381

Teriparatide - Indications beyond osteoporosis  

PubMed Central

Osteoporosis is a condition of impaired bone strength that results in an increased risk of fracture. The current and most popular pharmacological options for the treatment of osteoporosis include antiresorptive therapy, in particular, oral bisphosphonates (alendronate, risedronate, ibandronate). Anabolic agents like teriparatide have widened our therapeutic options. They act by directly stimulating bone formation and improving bone mass quantity and quality. Two forms of recombinant human parathyroid hormone (PTH) are available : full-length PTH (PTH 1–84; approved in the EU only) and the 1–34 N-terminal active fragment of PTH (teriparatide, US FDA approved). This review aims to discuss the benefits of teriparatide beyond the currently licensed indications like fracture healing, dental stability, osteonecrosis of jaw, hypoparathyroidism, and hypocalcemia.

Cheng, Marilyn Lee; Gupta, Vishal

2012-01-01

382

Network Stability  

NASA Astrophysics Data System (ADS)

Stability resembles intelligence: easy to imagine and hard to define. Here I will assess network stability at three different levels. First I will describe network perturbations and the concept of local dissipation and global connections. Later a number of different scenarios will be shown, where the perturbation is big or persistent enough to change the stability of the underlying bottom networks, and therefore, the structure of the current network is not preserved. Then stability relationships between the bottom and top networks will be discussed using the example of synchrony. Finally, I will describe the two basic design alternatives: evolution and engineering.

Csermely, Peter

383

Protein linear indices of the ‘macromolecular pseudograph ?-carbon atom adjacency matrix’ in bioinformatics. Part 1: Prediction of protein stability effects of a complete set of alanine substitutions in Arc repressor  

Microsoft Academic Search

A novel approach to bio-macromolecular design from a linear algebra point of view is introduced. A protein’s total (whole protein) and local (one or more amino acid) linear indices are a new set of bio-macromolecular descriptors of relevance to protein QSAR\\/QSPR studies. These amino-acid level biochemical descriptors are based on the calculation of linear maps on Rn[fk(xmi):Rn?Rn] in canonical basis.

Yovani Marrero-Ponce; Ricardo Medina-Marrero; Juan A. Castillo-Garit; Vicente Romero-Zaldivar; Francisco Torrens; Eduardo A. Castro

2005-01-01

384

Stabilization of supersaturated zincate solutions  

SciTech Connect

This paper investigates the stabilization of supersaturated zincate electrolytes in a silver-zinc battery by the addition of potassium hydroxide, lithium hydroxide, and molasses. Molasses, in combination with the hydroxide additives, was found to demonstrate a profound stabilizing influence on the zincate supersaturation and the electrolyte. Preliminary data on discharge of a battery using the combined additive indicates that it has higher discharge capacity than do batteries which contain the individual additives. The chemistry of this stabilizing influence is discussed.

Dmitrenko, V.E.; Zubov, M.S.; Baulov, V.I.; Balyakina, N.N.; Kotov, A.V.

1986-09-10

385

Immigrant Family Stability  

Microsoft Academic Search

The intent of this paper is to examine aspects of the immigration experience that impinge on the issue of family stability. The meager literature on the socioeconomic background of recent immigrants together with data collected on 150 recent immigrant families indicates that the newest wave of immigrants is, in general, well-prepared for life in the United States. However, the process

Geraldine Grant

1983-01-01

386

Membrane stabilizer  

DOEpatents

A device is provided for stabilizing a flexible membrane secured within a frame, wherein a plurality of elongated arms are disposed radially from a central hub which penetrates the membrane, said arms imposing alternately against opposite sides of the membrane, thus warping and tensioning the membrane into a condition of improved stability. The membrane may be an opaque or translucent sheet or other material. 10 figs.

Mingenbach, W.A.

1988-02-09

387

Stability of \\\  

Microsoft Academic Search

Stability of the kinetic drift-tearing mode with a short wave length is investigated employing an energy-dependent electron-ion collision model. The electron temperature gradient can destabilize the mode in the range of the collisionality 1≲nu\\/omega*≲20 (nu: collision frequency, omega*: drift frequency). This instability appears in a parameter range of intermediate beta-values, and the mode is stabilized by the magnetic shear when

Kimitaka Itoh; Sanae-Inoue Itoh

1982-01-01

388

Problem Stabilization  

PubMed Central

Background Public health nurse (PHN) home visiting programs have been widely employed to improve life course trajectories for high risk mothers. Home visiting programs are often lengthy, during which PHNs simultaneously address multiple problems using diverse interventions over several client encounters. To manage PHN caseloads it is critical to understand the trajectory of client improvement and the optimal duration or services. PHN documentation data enable intervention trajectory research for specific client problems. A new metric called problem stabilization is proposed for evaluating interim improvement during PHN home visiting. Problem stabilization is an intervention pattern for a client problem that is characterized by co-occurring actions (i.e. teaching, guidance, and counseling; treatments and procedures; case management; and/or surveillance) during a client encounter; followed by surveillance actions only for that problem during a subsequent client encounter. The purpose of the study was to investigate problem stabilization during home visiting services for high risk mothers. Methods A retrospective cohort was created using family home visiting intervention documentation data from a local Midwest public health agency over a six year period (2000–2005). The data set consisted of Omaha System interventions for 720 high risk mothers. Analysis was conducted using descriptive statistics and Kaplan Meier curves. Results On average 30.1% of the time, client problems stabilized before discharge. Stabilization patterns differed by problem. Time to stabilization was longest for Caretaking/parenting and Antepartum/postpartum problems, and shortest for Residence and Mental health problems. Conclusions Problem stabilization, a proposed intermediate outcome of PHN home visiting care, appears to be meaningful in describing client response to PHN intervention. This metric is an example of meaningful use of structured clinical electronic health record data for program evaluation and clinical decision support.

Monsen, K.A.; Farri, O.; McNaughton, D.B.; Savik, Kay

2011-01-01

389

Secular Stability of Rotating Stars.  

National Technical Information Service (NTIS)

In this work, we calculate the secular stability limits of rotating polytropes to nonaxisymmetric perturbations of low m. We consider polytropic indices ranging from 1 to 3 and several angular momentum distributions. Results are most conveniently presente...

J. N. Imamura J. L. Friedman R. H. Durisen

1984-01-01

390

Laser Stabilization  

SciTech Connect

This book chapter covers the basics of the field of stabilizing lasers to optical frequency references such as optical cavities and molecular transitions via the application of servo control systems. These discussions are given with reference to the real-life frequency metrology experienced in Hall-Labs (now Ye-Labs), JILA, University of Colorado. The subjects covered include: the basics of control system stability, a discussion of both the theoretical and experimental limitations, an outline of optical cavity susceptibility to environmental noise, and a brief introduction to the use and limitations of molecular transitions as frequency references.

Hall, John L.; Taubman, Matthew S.; Ye, Jun

2010-01-01

391

Visual stability.  

PubMed

Our vision remains stable even though the movements of our eyes, head and bodies create a motion pattern on the retina. One of the most important, yet basic, feats of the visual system is to correctly determine whether this retinal motion is owing to real movement in the world or rather our own self-movement. This problem has occupied many great thinkers, such as Descartes and Helmholtz, at least since the time of Alhazen. This theme issue brings together leading researchers from animal neurophysiology, clinical neurology, psychophysics and cognitive neuroscience to summarize the state of the art in the study of visual stability. Recently, there has been significant progress in understanding the limits of visual stability in humans and in identifying many of the brain circuits involved in maintaining a stable percept of the world. Clinical studies and new experimental methods, such as transcranial magnetic stimulation, now make it possible to test the causal role of different brain regions in creating visual stability and also allow us to measure the consequences when the mechanisms of visual stability break down. PMID:21242136

Melcher, David

2011-02-27

392

Visual stability  

PubMed Central

Our vision remains stable even though the movements of our eyes, head and bodies create a motion pattern on the retina. One of the most important, yet basic, feats of the visual system is to correctly determine whether this retinal motion is owing to real movement in the world or rather our own self-movement. This problem has occupied many great thinkers, such as Descartes and Helmholtz, at least since the time of Alhazen. This theme issue brings together leading researchers from animal neurophysiology, clinical neurology, psychophysics and cognitive neuroscience to summarize the state of the art in the study of visual stability. Recently, there has been significant progress in understanding the limits of visual stability in humans and in identifying many of the brain circuits involved in maintaining a stable percept of the world. Clinical studies and new experimental methods, such as transcranial magnetic stimulation, now make it possible to test the causal role of different brain regions in creating visual stability and also allow us to measure the consequences when the mechanisms of visual stability break down.

Melcher, David

2011-01-01

393

Stabilization of compactible waste  

SciTech Connect

This report summarizes the results of series of experiments performed to determine the feasibility of stabilizing compacted or compactible waste with polymers. The need for this work arose from problems encountered at disposal sites attributed to the instability of this waste in disposal. These studies are part of an experimental program conducted at Brookhaven National Laboratory (BNL) investigating methods for the improved solidification/stabilization of DOE low-level wastes. The approach taken in this study was to perform a series of survey type experiments using various polymerization systems to find the most economical and practical method for further in-depth studies. Compactible dry bulk waste was stabilized with two different monomer systems: styrene-trimethylolpropane trimethacrylate (TMPTMA) and polyester-styrene, in laboratory-scale experiments. Stabilization was accomplished by wetting or soaking compactible waste (before or after compaction) with monomers, which were subsequently polymerized. Three stabilization methods are described. One involves the in-situ treatment of compacted waste with monomers in which a vacuum technique is used to introduce the binder into the waste. The second method involves the alternate placement and compaction of waste and binder into a disposal container. In the third method, the waste is treated before compaction by wetting the waste with the binder using a spraying technique. A series of samples stabilized at various binder-to-waste ratios were evaluated through water immersion and compression testing. Full-scale studies were conducted by stabilizing two 55-gallon drums of real compacted waste. The results of this preliminary study indicate that the integrity of compacted waste forms can be readily improved to ensure their long-term durability in disposal environments. 9 refs., 10 figs., 2 tabs.

Franz, E.M.; Heiser, J.H. III; Colombo, P.

1990-09-01

394

A Rapid Stability-Indicating LC Method for Ziprasidone Hydrochloride  

Microsoft Academic Search

A simple and rapid reversed-phase liquid chromatographic method was developed for the related substances determination and\\u000a quantitative evaluation of ziprasidone hydrochloride, which is used as an antipsychotic agent. Forced degradation studies\\u000a were performed on bulk sample of ziprasidone hydrochloride using acid, base, oxidative hydrolysis, thermal stress and photolytic\\u000a degradation. Mild degradation of the drug substance was observed during thermal stress

A. Singh; B. M. Rao; G. R. Deshpande; S. Sangaraju; M. K. Srinivasu; M. Lalitha Devi; P. V. V. Satyanarayana; K. B. Chandrasekhar

2007-01-01

395

A stability-indicating liquid chromatographic method for Lomustine.  

PubMed

A simple, inexpensive and rapid liquid chromatography (LC) method has been developed for the quantitative determination of Lomustine, an chemotherapy drug. Degradation studies were performed on the bulk drug by heating to 60 °C, exposure to UV light at an energy of 200 Wh/m(2)and to visible light at an illumination of not less than 1.2 million lux hours, acid (0.1N hydrochloric acid), base (0.1N sodium hydroxide) aqueous hydrolysis and oxidation with 6.0% (v/v) hydrogen peroxide. Good resolution between the peaks corresponding to impurities produced during synthesis, degradation products and the analyte was achieved on a Symmetry C 8 LC column using a mobile phase consisting of a mixture of aqueous potassium dihydrogen phosphate and acetonitrile. The degradation samples were assayed against the reference standard of Lomustine and the mass balance in each case was close to 99.9%. Validation of the method was carried out as per International Conference on Harmonization (ICH) requirements. PMID:20719460

Seshaiah, K Rama; Samanta, Sudip Kr; Reddy, V Krishna; Prasadaraju, V V N K V; Mukkanti, K; Reddy, V Ranga

2010-07-27

396

Stability-indicating methods for the determination of disopyramide phosphate.  

PubMed

Four methods were developed for the determination of intact disopyramide phosphate in the presence of its degradation product. In the first and second methods, third-derivative spectrophotometry and first derivative of the ratio spectra were used. For the third-derivative spectrophotometric method, the peak amplitude was measured at 272 nm, while for the derivative ratio spectrophotometric method, disopyramide phosphate was determined by measuring the peak amplitude at 248 and 273 nm. Both methods were used for the determination of disopyramide phosphate in the concentration range 12.5-87.5 microg/mL, with corresponding mean recovery 100.8 +/- 0.7% for the first method and 99.9 +/- 0.7% and 99.6 +/- 0.7% for the second method at 248 and 273 nm, respectively. In the third method, an ion selective electrode (ISE) was fabricated using phosphotungstic acid as an anionic exchanger, PVC as the polymer matrix, and dibutylsebacate as a plasticizer. The ISE was used for the determination of disopyramide phosphate in pure powder form in the concentration range 10(-2)-10(-5) M. The slope was found to be 58.5 (mV/decade), and the average recovery was 99.9 +/- 1.6%. The fourth method depended on the quantitative densitometric determination of the drug in concentration range of 0.25-2.5 microg/spot using silica gel 60 F245 plates and ethyl acetate-chloroform-ammonium hydroxide (85 + 10 + 5, v/v/v) as the mobile phase, with corresponding mean accuracy of 100.3 +/- 1.1%. The 4 proposed methods were found to be specific for disopyramide phosphate in presence of up to 80% of its degradation product for the spectrophotometric methods, 90% of its degradation for the densitometric method, and 40% for the ISE method. The 4 proposed procedures were successfully applied for the determination of disopyramide phosphate in Norpace capsules. Statistical comparison between the results obtained by these methods and the official method of the drug was done, and no significant differences were found. PMID:16915833

Salem, Maissa Y; Ramadan, Nesrin K; Moustafa, Azza A; El-Bardicy, Mohamed G

397

Peptide therapeutics for CNS indications.  

PubMed

Neuropeptides play a crucial role in the normal function of the central nervous system and peptide receptors hold great promise as therapeutic targets for the treatment of several CNS disorders. In general, the development of peptide therapeutics has been limited by the lack of drug-like properties of peptides and this has made it very difficult to transform them into marketable therapeutic molecules. Some of these challenges include poor in vivo stability, poor solubility, incompatibility with oral administration, shelf stability, cost of manufacture. Recent technical advances have overcome many of these limitations and have led to rapid growth in the development of peptides for a wide range of therapeutic indications such as diabetes, cancer and pain. This review examines the therapeutic potential of peptide agonists for the treatment of major CNS disorders such as schizophrenia, anxiety, depression and autism. Both clinical and preclinical data has been accumulated supporting the potential utility of agonists at central neurotensin, cholecystokinin, neuropeptide Y and oxytocin receptors. Some of the successful approaches that have been developed to increase the stability and longevity of peptides in vivo and improve their delivery are also described and potential strategies for overcoming the major challenge that is unique to CNS therapeutics, penetration of the blood-brain barrier, are discussed. PMID:22051078

McGonigle, Paul

2011-10-25

398

Real-time voltage stability monitoring and evaluation using synchorophasors  

Microsoft Academic Search

This paper focuses on evaluating online voltage stability indices for an interconnected power system. The voltage stability indices are measured during the operation of the power system when the dynamic changes take places. The evaluation of the stability and security indices were performed by simulation and measurement of real-time data using Phasor Measurement Units (PMUs). The evaluation of the dynamic

Vahid Salehi; O. Mohammed

2011-01-01

399

Thermal indicator for wells  

DOEpatents

Minute durable plate-like thermal indicators are employed for precision measuring static and dynamic temperatures of well drilling fluids. The indicators are small enough and sufficiently durable to be circulated in the well with drilling fluids during the drilling operation. The indicators include a heat resistant indicating layer, a coacting meltable solid component and a retainer body which serves to unitize each indicator and which may carry permanent indicator identifying indicia. The indicators are recovered from the drilling fluid at ground level by known techniques.

Gaven, Jr., Joseph V. (Oakton, VA); Bak, Chan S. (Newbury Park, CA)

1983-01-01

400

Turbulence stabilization  

NASA Astrophysics Data System (ADS)

We recently developed a new approach to get a stabilized image from a sequence of frames acquired through atmospheric turbulence. The goal of this algorihtm is to remove the geometric distortions due by the atmosphere movements. This method is based on a variational formulation and is efficiently solved by the use of Bregman iterations and the operator splitting method. In this paper we propose to study the influence of the choice of the regularizing term in the model. Then we proposed to experiment some of the most used regularization constraints available in the litterature.

Mao, Yu; Gilles, Jérôme

2012-05-01

401

Monitoring cheddar cheese ripening by chemical indices of proteolysis. 3. Identification of several high-molecular mass peptides.  

PubMed

Two Cheddar cheeses from two different production plants were ripened over 24 weeks at 10 degrees C and then analysed for peptides soluble in citrate buffer at pH 4.6 by reversed-phase (RP)-HPLC. Thirteen peptides with a chain length of between 35 and 65 amino acid residues and molecular masses between 3800 and 7400 were isolated and assigned to the corresponding amino acid sequences of the casein fractions via Edman degradation and amino acid composition. All peptides were fragments of the region K29-S96 of beta-casein A1 and A2, and eleven of them had M93 as the C-terminal. The amounts and proportions of these peptides varied differently during ripening of the two cheeses, so they may be suitable markers for characterizing the stage of ripening. PMID:8212903

Belitz, H D; Kaiser, K P

1993-08-01

402

Indicators of Sustainable Development  

NSDL National Science Digital Library

This resource reviews indicators for monitoring progress toward sustainable development. Such indicators are important to decision-makers and policy-makers at all levels. The United Nations Commission on Sustainable Development (CSD) adopted 58 Indicators of Sustainable Development (ISDs) along with methodology sheets that are now available for all countries to use. Indicators for the atmosphere environmental subtheme include emissions of greenhouse gases, consumption of ozone depleting substances, and ambient concentration of air pollutants in urban areas. In addition to indicators for the atmosphere there are indicators for land, ocean, seas, coasts, fresh water, and biodiversity. For each of the indicators the site offers topics for relevance, methodological description, assessment of data, agencies involved, and references. The CSD indicator set and methodological descriptions are currently undergoing revision. An updated set is expected to be released in 2006.

403

ECOLOGICAL INDICATOR OVERVIEW  

EPA Science Inventory

The Ecological Indicator Program in NERL is developing indicators for two key purposes. The first is to characterize the biological condition of shallow streams and large rivers. The second is to develop diagnostic indicators to evaluate the causes of impairment to these commun...

404

Indices of landscape pattern  

Microsoft Academic Search

Landscape ecology deals with the patterning of ecosystems in space. Methods are needed to quantify aspects of spatial pattern that can be correlated with ecological processes. The present paper develops three indices of pattern derived from information theory and fractal geometry. Using digitized maps, the indices are calculated for 94 quadrangles covering most of the eastern United States. The indices

R. V. O'Neillr; J. R. Krummel; R. H. Gardner; G. Sugihara; B. Jackson; D. L. DeAngelist; B. T. Milne; M. G. Turner; B. Zygmunt; S. W. Christensen; V. H. Dale; R. L. Graham

1988-01-01

405

Riser position indication apparatus  

Microsoft Academic Search

This patent describes a Riser Position Indication Apparatus for disposition between an offshore vessel and a riser, the riser being moveable with respect to the offshore vessel. The riser position indication apparatus comprises: vessel connection means operatively engaged with the vessel to secure the riser position indication apparatus to the vessel, riser connection means operatively engaged with the riser to

1986-01-01

406

Stability of ?-Irradiated Carmine  

NASA Astrophysics Data System (ADS)

Carmine is a dye used mainly for coloring food products and galenicals but also in inks. As food irradiation is becoming a regular treatment for food preservation, it is desirable to have a proper knowledge about the radiation sensitivity of additives that can be included in the food formula. The aim of this work was to establish the radiation stability of carmine against Co-60 gamma radiation. Samples of 50% pure carmine powder as well as 50%, 10% and 5% aqueous solutions were irradiated in a Gammacell 220, dose rate of about 5.2 kGy/h, with doses of 0, 1, 2, 4, 8, 16 and 32 kGy. Spectrophotometric readings at 494 nm show a slight decrease of the absorbance as a function of dose: Samples irradiated with 4 and 32 kGy retained 95% and 90% of absorbance of the unirradiated samples respectively. These results indicate a rather good stability of carmine against ?-irradiation.

Cosentino, Hélio M.; Fontenele, Rinaldo S.; DelMastro, Nélida L.

2005-01-01

407

Medial patellofemoral ligament reconstruction: indications and technique.  

PubMed

Lateral instability of the patella is a common problem that often requires reconstruction of the proximal soft tissue restraints. The medial patellofemoral ligament (MPFL) has been demonstrated to be the major soft tissue stabilizer to prevent abnormal lateral displacement of the patella. In this chapter we will discuss the anatomy, biomechanics, indications, and technique for surgical reconstruction of the medial patellofemoral ligament. PMID:22878657

Schepsis, Anthony A; Rogers, Andrew J

2012-09-01

408

Setting accuracy indicator for machines (STUM)  

Microsoft Academic Search

The introduction of STUM indicators helps to stabilize plant performance, notably the amounts of charge taken on by the hoppers and in the final analysis the quality of the coke. The equipment on the car gives more reliable performance, since there are no breakages or inaccurate operations. Less coal dust and fumes are discharged during oven charging operations. The engineer's

V. P. Orekhovskii; V. A. Gerya; V. A. Ivashchenko; V. N. Stepanov

1983-01-01

409

Voltage stability based weak area clustering technique in power system  

Microsoft Academic Search

This paper presents the voltage stability based weak area clustering technique in power system. The technique employed voltage stability and line outage contingency analyses. From the voltage stability analysis, the sensitive lines in a system during stressed condition are identified, while line outage contingency analysis identified the critical line outages. A pre-developed voltage stability index was utilised as an indicator

Ismail Musirin; Titik Khawa Abdul Rahman

2004-01-01

410

Line outage contingency screening and ranking for voltage stability assessment  

Microsoft Academic Search

This paper presents the voltage stability based weak area clustering techniques in power system. The techniques employed voltage stability analysis (VSA) and Line outage contingency analysis (LOCA). From the VSA and LOCA, the most critical lines in a system during stressed condition are identified. A predeveloped voltage stability index was utilized as an indicator to voltage stability condition of the

C. Subramani; S. S. Dash; M. Arun Bhaskar; M. Jagadeeshkumar; K. Sureshkumar; R. Parthipan

2009-01-01

411

Compositional Bayesian indicator estimation  

Microsoft Academic Search

Indicator kriging is widely used for mapping spatial binary variables and for estimating the global and local spatial distributions\\u000a of variables in geosciences. For continuous random variables, indicator kriging gives an estimate of the cumulative distribution\\u000a function, for a given threshold, which is then the estimate of a probability. Like any other kriging procedure, indicator\\u000a kriging provides an estimation variance

Carolina Guardiola-Albert; Eulogio Pardo-Igúzquiza

2011-01-01

412

Crisis stability in the new world order  

SciTech Connect

This report gives a preliminary discussion of the crisis stability characteristics of the new world order through calculations calibrated for the current order. If finds that crisis stability indices have qualitatively similar behavior in the new order, but significantly more comforting values than in the old. The recent summit proposed significant cuts in MIRVed and heavy intercontinental ballistic missiles (ICBMs), and strategic weapons generally, that take the world into an apparently new order. This report gives a preliminary discussion of the crisis stability characteristics of that new order and of the interaction of offenses and defenses with stability indices in it.

Canavan, G.H.

1992-07-01

413

A simple and inexpensive sample-handling method for the semi-preparative RP-HPLC of polypeptides and non-polar peptide derivatives: pre-adsorption of samples  

Microsoft Academic Search

A simple method is described for the application onto HPLC columns of very crude or alternatively poorly soluble polypeptide samples prior to their chromatographic purification. The procedure involves the batch pre-adsorption of the crude polypeptide mixture from a dilute solution onto an appropriate preparative-grade chromatographic adsorbent, removal of the solvent by rotary evaporation or lyophilisation and then dry-packing the pre-adsorbed

Philip E. Thompson; Milton T. W. Hearn

1995-01-01

414

Development of a hyphenated procedure of heat-reflux and ultrasound-assisted extraction followed by RP-HPLC separation for the determination of three flavonoids content in Scutellaria barbata D. Don.  

PubMed

A hyphenated procedure of heat-reflux and ultrasound-assisted extraction (HUAE), and an accurate high-performance liquid chromatographic (HPLC) method were developed for the determination of apigenin, baicalin and luteolin content in Scutellaria barbara D. Don. The suitable HUAE conditions for the extraction of target compounds from the herb were identified as an ultrasonic frequency of 40kHz, power of 185W, duty cycle of 75% (intermittent sonication), mean particle size of 0.355mm, extraction temperature of 50°C, ratio of solvent to raw material of 12:1 (mL/g), ethanol concentration of 60% (v/v), extraction time of 30min and three cycles. Compared with a traditional heat-reflux extraction method, the proposed method reduced the extraction time, extraction temperature and solvent consumption. Also, this HUAE method achieved superior apigenin, baicalin and luteolin yields. Furthermore, the developed HUAE-HPLC method was applied successfully for the simultaneous evaluation of three bioactive compounds in five samples of S. barbara D. Don obtained from different geographical regions. These results clearly demonstrated that the combined HUAE-HPLC process is feasible in the future commercialized manufacture of this highly valuable Chinese herbal medicine. PMID:24145017

Wei, Ming-Chi; Yang, Yu-Chiao; Chiu, Hui-Fen; Hong, Show-Jen

2013-09-25

415

Characterization of CIMMYT bread wheats for high- and low-molecular weight glutenin subunits and other quality-related genes with SDS-PAGE, RP-HPLC and molecular markers  

Microsoft Academic Search

Two hundred and seventy-three CIMMYT bread wheat cultivars and advanced lines grown under irrigated conditions in Mexico during\\u000a the 2005-06 Yaqui crop cycle were characterized for quality-related genetic traits using gene-specific markers for some high-\\u000a and low-molecular-weight glutenin subunit (HMW-GS and LMW-GS) genes, polyphenol oxidase (PPO), phytoene synthase (PSY), and\\u000a waxy genes. Of them, 142 were analyzed for quality parameters

Dan LiangJianwei; Jianwei Tang; Roberto Javier Peña; Ravi Singh; Xinyao He; Xiaoyong Shen; Danian Yao; Xianchun Xia; Zhonghu He

2010-01-01

416

An optimized and validated RP-HPLC\\/UV detection method for simultaneous determination of all-trans-Retinol (Vitamin A) and ?-Tocopherol (Vitamin E) in human serum: Comparison of different particulate reversed-phase HPLC columns  

Microsoft Academic Search

A novel, simple and fast reversed-phase HPLC\\/UV method was developed, optimized for various chromatographic conditions, and validated according to international guidelines for simultaneous determination of all-trans-retinol and ?-tocopherol in human serum using retinyl acetate as internal standard in the concentration of 0.5?g\\/ml. A liquid-phase extraction was applied to the 250?l of serum with n-hexane–dichloromethane mixture (70:30, v\\/v), in two steps,

Abad Khan; Muhammad I. Khan; Zafar Iqbal; Yasar Shah; Lateef Ahmad; David G. Watson

2010-01-01

417

Indicator principal component kriging  

Microsoft Academic Search

An alternative to multiple indicator kriging is proposed which approximates the full coindicator kriging system by kriging the principal components of the original indicator variables. This transformation is studied in detail for the biGaussian model. It is shown that the cross-correlations between principal components are either insignificant or exactly zero. This result allows derivation of the conditional cumulative density function

V. Suro-Pérez; A. G. Journel

1991-01-01

418

Developing SOLEC Forest Indicators  

Microsoft Academic Search

Covering roughly half of the basin landmass, forests are a vital inland component of the Great Lakes basin ecosystem. Adding forest indicators to the SOLEC suite has been a priority in recent years, and SOLEC 2004 will be marked by the submission of data on the first three indicators of forest health. Healthy forests are crucial to maintaining and restoring

Mervyn Han

419

Tamper indicating packaging  

Microsoft Academic Search

Protecting sensitive items from undetected tampering in an unattended environment is crucial to the success of non-proliferation efforts relying on the verification of critical activities. Tamper Indicating Packaging (TIP) technologies are applied to containers, packages, and equipment that require an indication of a tamper attempt. Examples include: the transportation and storage of nuclear material, the operation and shipment of surveillance

M. J. Baumann; J. C. Bartberger; T. D. Welch

1994-01-01

420

Chronic Disease Indicators  

NSDL National Science Digital Library

The Chronic Disease Indicators (CDI) is a cross-cutting set of 97 indicators that were developed by consensus and that allows states and territories and large metropolitan areas to uniformly define, collect, and report chronic disease data that are important to public health practice and available for states, territories and large metropolitan areas. 

Control, Center F.

421

Indicators for energy security  

Microsoft Academic Search

The concept of energy security is widely used, yet there is no consensus on its precise interpretation. In this research, we have provided an overview of available indicators for long-term security of supply (SOS). We distinguished four dimensions of energy security that relate to the availability, accessibility, affordability and acceptability of energy and classified indicators for energy security according to

Bert Kruyt; D. P. van Vuuren; H. J. M. de Vries; H. Groenenberg

2009-01-01

422

Energy-conservation indicators  

Microsoft Academic Search

A series of Energy Conservation Indicators were developed for the Department of Energy to assist in the evaluation of current and proposed conservation strategies. As descriptive statistics that signify current conditions and trends related to efficiency of energy use, indicators provide a way of measuring, monitoring, or inferring actual responses by consumers in markets for energy services. Related sets of

Belzer

1982-01-01

423

Chemical calcium indicators  

Microsoft Academic Search

Our understanding of the underlying mechanisms of Ca2+ signaling as well as our appreciation for its ubiquitous role in cellular processes has been rapidly advanced, in large part, due to the development of fluorescent Ca2+ indicators. In this chapter, we discuss some of the most common chemical Ca2+ indicators that are widely used for the investigation of intracellular Ca2+ signaling.

R. Madelaine Paredes; Julie C. Etzler; Lora Talley Watts; Wei Zheng; James D. Lechleiter

2008-01-01

424

Rehabilitation Indicators: An Overview.  

ERIC Educational Resources Information Center

|The purpose of the Rehabilitation Indicators Project is to develop a method, rehabilitation indicators (RI's), for defining multi-dimensionally the benefits that accrue to rehabilitation clients. RI's are presented as descriptors of observable elements of the rehabilitation client's life space with each descriptor inherently meaningful to client…

Brown, Margaret M.; And Others

425

Uranium mill tailings stabilization  

SciTech Connect

Uranium mill tailings pose a potential radiation health hazard to the public. Therefore, stabilization or disposal of these tailings in a safe and environmentally sound way is needed to minimize radon exhalation and other environmental hazards. One of the most promising concepts for stabilizing U tailings is the use of asphalt emulsion to contain radon and other hazardous materials within uranium tailings. This approach is being investigated at the Pacific Northwest Laboratory. Results of these studies indicate that a radon flux reduction of greater than 99% can be obtained using either a poured-on/sprayed-on seal (3.0 to 7.0 mm thick) or an admixture seal (2.5 to 12.7 cm thick) containing about 18 wt % residual asphalt. A field test was carried out in June 1979 at the Grand Junction tailings pile in order to demonstrate the sealing process. A reduction in radon flux ranging from 4.5 to greater than 99% (76% average) was achieved using a 15.2-cm (6-in.) admix seal with a sprayed-on top coat. A hydrostatic stabilizer was used to apply the admix. Following compaction, a spray coat seal was applied over the admix as the final step in construction of a radon seal. Overburden was applied to provide a protective soil layer over the seal. Included in part of the overburden was a herbicide to prevent root penetration.

Hartley, J.N.; Koehmstedt, P.L.; Esterl, D.J.; Freeman, H.D.

1980-02-01

426

A New Voltage Stability Index Considering Voltage Limits  

Microsoft Academic Search

Recently, concerns over voltage instability phenomena have been increasing, because significant voltage drops are regarded crucial in stable operations. Thus, effective voltage control schemes using voltage stability indices have been brought to attention in a considerable number of studies. The conventional voltage stability indices are mainly based on evaluating voltage stability margins to a critical point. The operator usually determines

Y. Kataoka; M. Watanabe; S. Iwamoto

2006-01-01

427

[Mood stabilizers].  

PubMed

Within recent years the diagnostic concept of bipolar disorders has profoundly changed. The original view of one manic-depressive illness has become more and more a spectrum disorder ranging from personality traits to the full clinical feature of manic-depressive illness. Therefore, prevalence has increased in the general population. However, for differential treatment approaches with mood stabilisers the clinical distinction between bipolar I and bipolar II disorders becomes more and more relevant and, importantly, rapid cycling is a critical criterion for a differential indication of mood stabilisers. In acute treatment the psychopathological features such as euphoric versus dysphoric mania, the severity and the frequency of episodes play an important role for the choice of the mood stabiliser. According to international guidelines Lithium and Valproat are first-line treatment options. In addition, Lamotrigin has become a first-line treatment in special issues such as long-term treatment of bipolar depression. Carbamazepin, however, has lost its first-line place due to the evidence-based data situation and due to the side-effect profile. Within recent years the atypical anti-psychotics were investigated in bipolar disorder. Meanwhile, most of them have an indication for the treatment of acute mania, some of them for bipolar depression. Some studies also point to an efficacy in long-term prophylactic treatment. In summary, the psychopharmacological indications for the differential use of mood stabilisers are becoming more and more complex, therefore clear guidelines are needed. PMID:19496037

Hatzinger, Martin

2009-06-01

428

Composite stabilizer unit  

DOEpatents

This invention is comprised of an improved fin stabilized projectile including multiple stabilizer fins upon a stabilizer unit situated at the aft end of the projectile is provided, the improvement wherein the stabilizer fins are joined into the stabilizer unit by an injection molded engineering grade polymer.

Ebaugh, L.R.; Sadler, C.P.; Carter, G.D.

1990-12-31

429

Composite stabilizer unit  

DOEpatents

An improved fin stabilized projectile including multiple stabilizer fins upon a stabilizer unit situated at the aft end of the projectile is provided, the improvement wherein the stabilizer fins are joined into the stabillizer unit by an injection molded engineering grade polymer.

Ebaugh, Larry R. (Los Alamos, NM); Sadler, Collin P. (Los Alamos, NM); Carter, Gary D. (Espanola, NM)

1992-01-01

430

Composite stabilizer unit  

DOEpatents

This invention is comprised of an improved fin stabilized projectile including multiple stabilizer fins upon a stabilizer unit situated at the aft end of the projectile is provided, the improvement wherein the stabilizer fins are joined into the stabilizer unit by an injection molded engineering grade polymer.

Ebaugh, L.R.; Sadler, C.P.; Carter, G.D.

1990-01-01

431

Voltage stability constrained load curtailment procedure to evaluate power system reliability measures  

Microsoft Academic Search

This paper reports a method to evaluate composite power system reliability indices incorporating the voltage stability margin criteria. To compute the load curtailment evaluation, an optimal power flow (OPF) computation algorithm, considering the steady state voltage stability margin constraint is developed. A steady state voltage stability indicator is first discussed for its applicability as a suitable indicator for representing stability

G. M. Huang; Nirmal-Kumar C Nair

2002-01-01

432

Photomultiplier tube saturation indicator  

DOEpatents

A photomultiplier tube saturation indicator is formed by supplying a supplemental light source, typically a light emitting diode (LED), adjacent to the photomultiplier tube. A switch allows the light source to be activated. The light is forwarded to the photomultiplier tube by an optical fiber. If the probe is properly light tight, then a meter attached to the indicator will register the light from the LED. If the probe is no longer light tight, and the saturation indicator is saturated, no signal will be registered when the LED is activated. This photomultiplier tube is used with alpha contamination probes.

Ruch, J.F.; Urban, D.J.

1995-12-31

433

New England Economic Indicators  

NSDL National Science Digital Library

New England Economic Indicators, a monthly publication from the Federal Reserve Bank of Boston, contains articles on subjects including labor market conditions, consumer prices, consumer confidence, and electricity sales.

434

Tamper indicating packaging.  

National Technical Information Service (NTIS)

Protecting sensitive items from undetected tampering in an unattended environment is crucial to the success of non-proliferation efforts relying on the verification of critical activities. Tamper Indicating Packaging (TIP) technologies are applied to cont...

M. J. Baumann J. C. Bartberger T. D. Welch

1994-01-01

435

HITRAN 2012 refractive indices  

NASA Astrophysics Data System (ADS)

The HITRAN 2012 compilation of the real and imaginary refractive indices of the materials in aerosols and cloud particles is reviewed. Additions to HITRAN 2012 focus upon materials that are absorptive (i.e. minerals, burning vegetation, brown carbon, desert dust, and volcanic ash). The HITRAN-RI program, created to facilitate usage of the indices, is discussed. The HITRAN-RI program inter-compares the indices of different data sets and calculates optical properties (i.e. extinction, scattering, absorption, single scattering albedo, backscattering, and asymmetry parameter) for user specified size distributions and particle types. The instructional component of HITRAN-RI introduces the user to Mie calculations for spheres and coated spheres, and applies various mixing rules by which one calculates the effective indices of a multi-component particle.

Massie, S. T.; Hervig, M.

2013-11-01

436

Energy-Conservation Indicators.  

National Technical Information Service (NTIS)

A series of Energy Conservation Indicators were developed for the Department of Energy to assist in the evaluation of current and proposed conservation strategies. As descriptive statistics that signify current conditions and trends related to efficiency ...