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1

Rapid Analysis of Glibenclamide Using an Environmentally Benign Stability-Indicating RP-HPLC Method  

PubMed Central

An environmentally benign RP-HPLC approach for rapid analysis of glibenclamide in pure form, developed nanoemulsion and commercial tablets was developed and validated in present investigation. The green chromatographic identification was performed on Lichrosphere 250 X 4.0 mm RP C8 column having a 5 ?m packing as a stationary phase using a combination of ethanol: methanol (50:50 % v/v) as a mobile phase, at a flow rate of 1.0 mL/min with UV detection at 245 nm. The proposed method was validated for linearity, selectivity, accuracy, precision, robustness, sensitivity and specificity as per international conference on harmonization (ICH) guidelines. The utility of proposed method was verified by assay of glibenclamide in developed nanoemulsion and commercial tablets. The proposed method was found to be satisfactory in terms of selectivity, precision, accuracy, robustness, sensitivity and specificity. The content of glibenclamide in developed nanoemulsion and commercial tablets was found to be 100.50 % and 99.15 % respectively. The proposed method successfully resoled glibenclamide peak in the presence of its all type of degradation products which indicated stability-indicating property of the proposed method. These results indicated that the green chromatographic method could be successfully employed for routine analysis of glibenclamide in pure drug and various commercial formulations. PMID:25276186

Haq, Nazrul; Alanazi, Fars Kaed; Alsarra, Ibrahim Abdullah; Shakeel, Faiyaz

2014-01-01

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. PMID:20376215

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

2009-01-01

3

Development and Validation of a Stability-Indicating Assay of Etofenamate by RP-HPLC and Characterization of Degradation Products.  

PubMed

A validated stability-indicating RP-HPLC method for etofenamate (ETF) was developed by separating its degradation products on a C18 (250 mm × 4.6 mm 5 ?m) Qualisil BDS column using a phosphate buffer (pH-adjusted to 6.0 with orthophosphoric acid) and methanol in the ratio of 20:80 % v/v as the mobile phase at a flow rate of 1.0 mL/min. The column effluents were monitored by a photodiode array detector set at 286 nm. The method was validated in terms of specificity, linearity, accuracy, precision, detection limit, quantification limit, and robustness. Forced degradation of etofenamate was carried out under acidic, basic, thermal, photo, and peroxide conditions and the major degradation products of acidic and basic degradation were isolated and characterized by (1)H-NMR, (13)C-NMR, and mass spectral studies. The mass balance of the method varied between 92-99%. PMID:24482770

Peraman, Ramalingam; Nayakanti, Devanna; Dugga, Hari Hara Theja; Kodikonda, Sudhakara

2013-12-01

4

A Validated Specific Stability-Indicating RP-HPLC Assay Method for the Determination of Loteprednol Etabonate in Eye Drops.  

PubMed

A new stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of loteprednol etabonate in bulk drugs and in ophthalmic suspensions in the presence of degradation products generated from forced degradation studies. The system consisted of Agilent Technologies Zorbax Eclipse XDB-Phenyl 5 µm 4.6 × 250 mm, and detection was performed at 244 nm. The mobile phase consisted of water-acetonitrile-acetic acid (34.5:65.0:0.5, v/v/v) run at a flow rate of 1 mL/min and maintained at room temperature. The calibration curve was linear from 30 to 70 µg/mL with r > 0.999. Accuracy (mean recovery 100.78%) and precision were found to be satisfactory. Stress conditions including acid and alkali hydrolysis, water stress, oxidation, photolysis and heat were applied. The degradation products did not interfere with the detection of loteprednol etabonate, thus the method can be considered as a stability-indicating method. The proposed method can be used for quality control assay of loteprednol etabonate in bulk drug and in ophthalmic suspensions and for stability studies as a result of the ability of the method to separate loteprednol etabonate from its degradation products and excipients. PMID:25234383

Han, Yong K; Segall, Adriana I

2014-09-18

5

Stability-Indicating RP-HPLC Method for Simultaneous Estimation of Enrofloxacin and Its Degradation Products in Tablet Dosage Forms  

PubMed Central

The present work was the development of a simple, efficient, and reproducible stability-indicating reverse-phase high performance liquid chromatographic (RP-HPLC) method for simultaneous determination enrofloxacin (EFX) and its degradation products including ethylenediamine impurity, desfluoro impurity, ciprofloxacin impurity, chloro impurity, fluoroquinolonic acid impurity, and decarboxylated impurity in tablet dosage forms. The separation of EFX and its degradation products in tablets was carried out on Kromasil C-18 (250 × 4.6?mm, 5??m) column using 0.1% (v/v) TEA in 10?mM KH2PO4 (pH 2.5) buffer and methanol by linear gradient program. Flow rate was 1.0?mL?min?1 with a column temperature of 35°C and detection wavelength was carried out at 278?nm and 254?nm. The forced degradation studies were performed on EFX tablets under acidic, basic, oxidation, thermal, humidity, and photolytic conditions. The degraded products were well resolved from the main active drug and also from known impurities within 65 minutes. The method was validated in terms of specificity, linearity, LOD, LOQ, accuracy, precision, and robustness as per ICH guidelines. The results obtained from the validation experiments prove that the developed method is a stability-indicating method and suitable for routine analysis. PMID:25705547

Chakravarthy, V. Ashok; Sailaja, B. B. V.; Kumar, Avvaru Praveen

2015-01-01

6

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. PMID:23008808

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

2012-01-01

7

FORCED DEGRADATION AND PH STABILITY STUDIES OF LYSERGOL: AN ERGOLIC ALKALOID BY STABILITY INDICATING RP HPLC-UV METHOD  

Microsoft Academic Search

A simple HPLC-UV method was developed and validated for the analysis of lysergol, its stress degradation profile, and pH stability studies. Instrument used was Agilent HPLC 1120 autosampler with a C18 reversed phase column and a mobile phase comprised of methanol and water (1% acetic acid) with isocratic flow. Flow rate was kept constant at 1 mL\\/min throughout the experiment and

Shamama Javed; Kanchan Kohli; Mushir Ali

2012-01-01

8

DEVELOPMENT AND VALIDATION OF STABILITY INDICATING RP-HPLC METHOD FOR ANALYSIS OF LERCANIDIPINE IN BULK DRUG AND MICROEMULSION FORMULATION  

Microsoft Academic Search

A simple, sensitive and stability indicating method is described for the quantitative determination of lercanidipine both in bulk drugs and microemulsions, also in the presence of its degradation products. The method was based on high-performance liquid chromatographic (HPLC) separation of drug from its degradation products. The analysis was carried out on C18 reverse phase, [Agilent TC-C18(2) column (250 mm x 4.6 mm

Nitin Parmar; Neelam Singla; Saima Amin; Kanchan Kohli

2012-01-01

9

Validated Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Azelnidipine and Olmesartan in Their Combined Dosage Form  

PubMed Central

Abstract A simple, rapid, and highly selective RP-HPLC method was developed for the simultaneous determination of Azelnidipine (AZL) and Olmesartan (OLM) drug substances in the fixed dosage strength of 16 mg and 20 mg, respectively. Effective chromatographic separation was achieved using a Hypersil GOLD C18 column (150 mm × 4.6 mm internal diameter, 5 µm particle size) with a mobile phase composed of methanol, acetonitrile, and water in the ratio of 40:40:20 (by volume). The mobile phase was pumped using a gradient HPLC system at a flow rate of 0.5 mL/min, and quantification of the analytes was based on measuring their peak areas at 260 nm. The retention times for Azelnidipine and Olmesartan were about 8.56 and 3.04 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 2–48 ?g/mL for Azelnidipine and 2.5–60 ?g/mL for Olmesartan with correlation coefficients >0.990. The proposed method proved to be selective and stability-indicating by the resolution of the two analytes from the forced degradation (hydrolysis, oxidation, and photolysis) products. The validated HPLC method was successfully applied to the analysis of AZL and OLM in their combined dosage form.

Patel, Jayvadan K; Patel, Nilam K

2014-01-01

10

Stability-indicating RP-HPLC Method for the Simultaneous Determination of Sitagliptin and Simvastatin in Tablets.  

PubMed

A new stability-indicating high-performance liquid chromatographic method for simultaneous analysis of sitagliptin and simvastatin in pharmaceutical dosage form was developed and validated. The mobile phase consisted of methanol and water (70:30, v/v) with 0.2 % of n-heptane sulfonic acid adjusted to pH 3.0 with ortho phosphoric acid was used. Retentions of sitagliptin and simvastatin were 4.3 min and 30.4 min, respectively with a flow rate of 1 ml/min on C8 (Qualisil BDS, 250×4.6 mm, 5 ?). Eluents were detected at 253 nm using photodiode diode array detector. The linear regression analysis data for the linearity plot showed correlation coefficient values of 0.9998 and 0.9993 for sitagliptin and simvastatin, with respective concentration ranges of 20-150 ?g/ml and 8-60 ?g/ml. The relative standard deviation for inter-day precision was lower than 2.0%. The assay of sitagliptin and simvastatin was determined in tablet dosage form was found to be within limits. Both drugs were subjected to a variety of stress conditions such as acidic, basic, oxidation, photolytic, neutral and thermal stress in order to achieve adequate degradation. Results revealed that considerable degradation was found in all stress conditions except oxidative degradations. The method has proven specificity for stability indicating assay method. PMID:25425754

Ramalingam, P; Bhaskar, V Udaya; Reddy, Y Padmanabha; Kumar, K Vinod

2014-09-01

11

Stability-indicating RP-HPLC Method for the Simultaneous Determination of Sitagliptin and Simvastatin in Tablets  

PubMed Central

A new stability-indicating high-performance liquid chromatographic method for simultaneous analysis of sitagliptin and simvastatin in pharmaceutical dosage form was developed and validated. The mobile phase consisted of methanol and water (70:30, v/v) with 0.2 % of n-heptane sulfonic acid adjusted to pH 3.0 with ortho phosphoric acid was used. Retentions of sitagliptin and simvastatin were 4.3 min and 30.4 min, respectively with a flow rate of 1 ml/min on C8 (Qualisil BDS, 250×4.6 mm, 5 ?). Eluents were detected at 253 nm using photodiode diode array detector. The linear regression analysis data for the linearity plot showed correlation coefficient values of 0.9998 and 0.9993 for sitagliptin and simvastatin, with respective concentration ranges of 20-150 ?g/ml and 8-60 ?g/ml. The relative standard deviation for inter-day precision was lower than 2.0%. The assay of sitagliptin and simvastatin was determined in tablet dosage form was found to be within limits. Both drugs were subjected to a variety of stress conditions such as acidic, basic, oxidation, photolytic, neutral and thermal stress in order to achieve adequate degradation. Results revealed that considerable degradation was found in all stress conditions except oxidative degradations. The method has proven specificity for stability indicating assay method. PMID:25425754

Ramalingam, P.; Bhaskar, V. Udaya; Reddy, Y. Padmanabha; Kumar, K. Vinod

2014-01-01

12

A Stability-Indicating RP-HPLC Method for the Quantitative Analysis of Meclizine Hydrochloride in Tablet Dosage Form.  

PubMed

A specific stability-indicating reversed-phase high-performance liquid chromatographic method was developed and validated for the estimation of meclizine hydrochloride (MEC) in tablet dosage form. The HPLC method has shown adequate separation of MEC from their degradation products. The separation was achieved on a C8 (250 mm×4.6 mm×5 µm) column using a mobile phase composition of 0.2% triethylamine in water and methanol in the ratio of 65:35(pH adjusted to 3.0 with orthophosphoric acid) with a flow rate of 1 mL/min. The wavelength of a photo-diode array detector was kept at 229 nm. Stress studies were performed initially under milder conditions followed by stronger conditions so as to get sufficient degradation around 5-20%. There were six degradation products observed with adequate separation from the analyte peak. Among those detected degradation products, structures of four degradation products were verified by comparison with known impurities of meclizine analogs. The method was validated as per the International Conference on Harmonization (Q2) guidelines. The method was specific, selective, accurate and precise to quantify meclizine in the presence of degradation products. PMID:25644814

Peraman, Ramalingam; Manikala, Maheswari; Kondreddy, Vinod Kumar; Yiragamreddy, Padmanabha Reddy

2015-05-01

13

Identification of Degradation Products and a Stability-Indicating RP-HPLC Method for the Determination of Flupirtine Maleate in Pharmaceutical Dosage Forms.  

PubMed

In this stability-indicating, reversed-phase high-performance liquid chromatographic method for flupiritine maleate, forced degradation has been employed and the formed degradants were separated on a C18 column with a 80:20% v/v mixture of methanol-water containing 0.2% (v/v) triethylamine; the pH was adjusted to 3.1. The flow rate was 1 mLmin(-1) and the photodiode array detection wavelength was 254 nm. Forced degradation of the drug was carried out under acidic, basic, thermal, photolytic, peroxide, and neutral conditions. Chromatographic peak purity data indicated no co-eluting peaks with the main peaks. This method resulted in the detection of seven degradation products (D1-D7). Among these, three major degradation products from acidic and basic hydrolysis were identified and characterized by (1)H-NMR, (13)C-NMR, and mass spectral data. The method was validated as per International Conference on Harmonization guidelines (Q2). The linearity of the method was in the concentration range of 20-120 ?gmL(-1). The relative standard deviations for intra- and interday precision were below 1.5%. The specificity of the method is suitable for the stability-indicating assay. PMID:24959399

Peraman, Ramalingam; Lalitha, K V; Raja, Naga Mallikarjuna; Routhu, Hari Babu

2014-06-01

14

Development and validation of a RP-HPLC method for stability-indicating assay of gemifloxacin mesylate including identification of related substances by LC-ESI-MS/MS, 1H and 13C NMR spectroscopy.  

PubMed

A validated stability indicating RP-HPLC assay of gemifloxacin mesylate was developed by separating its related substances on an Inertsil-ODS3V-C18 (4.6 × 250 mm; 5 ?m) column using 0.1% trifluoroaceticacid (pH 2.5) and methanol as a mobile phase in a gradient elution mode at a flow rate of 1.0 mL/min at 27°C. The column effluents were monitored by a photodiode array detector set at 287 nm. The method was validated in terms of accuracy, precision and linearity as per ICH guidelines. Forced degradation of gemifloxacin (GFX) was carried out under acidic, basic, thermal, photolysis and peroxide conditions and the degradation products were separated and characterized by ESI-MS/MS, (1) H and (13) C NMR spectroscopy. The method was successfully applied to the analysis of bulk drugs and the recoveries of gemifloxacin and impurities were in the range of 97.60-102.90 and 96.99-102.10%, respectively. No previous reports were found in the literature on identification of degradation products of gemifloxacin. PMID:21370250

Rao, R Nageswara; Naidu, Ch Gangu; Prasad, K Guru; Narasimha, R

2011-11-01

15

Stability indicating RP-HPLC method development and validation for the simultaneous determination of aminexil and minoxidil in pharmaceutical dosage form.  

PubMed

The objective of the present work is to develop stability indicating high-performance liquid chromatographic method for the simultaneous determination of aminexil and minoxidil in pharmaceutical dosage form. The chromatographic separation was achieved with BDS Hypersil C18 column (250mm×4.6mm×5?) as stationary phase and phosphate buffer and acetonitrile (78:22) as mobile phase. The method was employed by using a flow rate of 1.1mL/min kept at 30°C. The detection wavelength was kept at 238nm by using photo-diode array detector. The retention times of the aminexil and minoxidil were found to be 2.3min and 3.9min, respectively. The method developed was validated in accordance with ICH guidelines with respect to the stability indicating capacity of the method including system suitability, accuracy, precision, linearity, range, limit of detection, limit of quantification and robustness. The linearity responses of aminexil and minoxidil were found to be in the concentration ranges of 18.75-112.5?g/mL and 25-150?g/mL, respectively. The LOD and LOQ values for aminexil were found to be 0.31 and 0.92?g/mL and minoxidil were found to be 0.03 and 0.10?g/mL respectively. The percentage recoveries for both the drugs were found in the range of 98-101%. This method is accurate, precise and sensitive; hence, it can be employed for routine quality control of aminexil and minoxidil in pharmaceutical industries and drug testing laboratories. PMID:25542653

Siddiraju, S; Sahithi, M

2015-03-01

16

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

2012-09-01

17

Quality by Design-Based Development of a Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Methylparaben, Propylparaben, Diethylamino Hydroxybenzoyl Hexyl Benzoate, and Octinoxate in Topical Pharmaceutical Formulation.  

PubMed

A stability-indicating RP-HPLC method has been developed and validated for the simultaneous determination of methylparaben (MP), propylparaben (PP), diethylamino hydroxybenzoyl hexyl benzoate (DAHHB), and octinoxate (OCT) in topical pharmaceutical formulation. The desired chromatographic separation was achieved on the Kinetex(TM) C18 (250 × 4.6 mm, 5 ?m) column using gradient elution at 257 nm detection wavelength. The optimized mobile phase consisted of a buffer : acetonitrile : tetrahydrofuran (60 : 30 : 10, v/v/v) as solvent A and acetonitrile : tetrahydrofuran (70 : 30, v/v) as solvent B. The method showed linearity over the range of 0.19-148.4 ?g/mL, 0.23-15.3 ?g/mL, 1.97-600.5 ?g/mL, and 1.85-451.5 ?g/mL for MP, PP, DAHHB, and OCT, respectively. Recovery for all the components was found to be in the range of 98-102%. The stability-indicating capability of the developed method was established by analysing the forced degradation samples in which the spectral purity of MP, PP, DAHHB, and OCT, along with the separation of the degradation products from the analyte peaks, was achieved. The proposed method was successfully applied for the quantitative determination of MP, PP, DAHHB, and OCT in the lotion sample. The design expert with ANOVA software with the linear model was applied and a 2(4) full factorial design was employed to estimate the model coefficients and also to check the robustness of the method. Results of the two-level full factorial design, 2(4) with 20 runs including four centrepoint analysis based on the variance analysis (ANOVA), demonstrated that all four factors, as well as the interactions of resolution between DAHHB and OCT are statistically significant. PMID:25853065

Roy, Chinmoy; Chakrabarty, Jitamanyu

2014-09-01

18

Quality by Design-Based Development of a Stability-Indicating RP-HPLC Method for the Simultaneous Determination of Methylparaben, Propylparaben, Diethylamino Hydroxybenzoyl Hexyl Benzoate, and Octinoxate in Topical Pharmaceutical Formulation  

PubMed Central

Abstract A stability-indicating RP-HPLC method has been developed and validated for the simultaneous determination of methylparaben (MP), propylparaben (PP), diethylamino hydroxybenzoyl hexyl benzoate (DAHHB), and octinoxate (OCT) in topical pharmaceutical formulation. The desired chromatographic separation was achieved on the KinetexTM C18 (250 × 4.6 mm, 5 ?m) column using gradient elution at 257 nm detection wavelength. The optimized mobile phase consisted of a buffer : acetonitrile : tetrahydrofuran (60 : 30 : 10, v/v/v) as solvent A and acetonitrile : tetrahydrofuran (70 : 30, v/v) as solvent B. The method showed linearity over the range of 0.19–148.4 ?g/mL, 0.23–15.3 ?g/mL, 1.97–600.5 ?g/mL, and 1.85–451.5 ?g/mL for MP, PP, DAHHB, and OCT, respectively. Recovery for all the components was found to be in the range of 98–102%. The stability-indicating capability of the developed method was established by analysing the forced degradation samples in which the spectral purity of MP, PP, DAHHB, and OCT, along with the separation of the degradation products from the analyte peaks, was achieved. The proposed method was successfully applied for the quantitative determination of MP, PP, DAHHB, and OCT in the lotion sample. The design expert with ANOVA software with the linear model was applied and a 24 full factorial design was employed to estimate the model coefficients and also to check the robustness of the method. Results of the two-level full factorial design, 24 with 20 runs including four centrepoint analysis based on the variance analysis (ANOVA), demonstrated that all four factors, as well as the interactions of resolution between DAHHB and OCT are statistically significant.

Roy, Chinmoy; Chakrabarty, Jitamanyu

2014-01-01

19

Highly efficient, selective, sensitive and stability indicating RP-HPLC-UV method for the quantitative determination of potential impurities and characterization of four novel impurities in eslicarbazepine acetate active pharmaceutical ingredient by LC/ESI-IT/MS/MS.  

PubMed

A novel, sensitive, selective and stability indicating LC-UV method was developed for the determination of potential impurities of eslicarbazepine acetate. High performance liquid chromatographic investigation of eslicarbazepine acetate laboratory sample revealed the presence of several impurities. Three impurities were characterized rapidly and four impurities were found to be unknown. The unknown impurities were identified by liquid chromatography coupled with electrospray ionization, ion trap mass spectrometry (LC/ESI-IT/MS/MS). Structural confirmation of these impurities was unambiguously carried out by synthesis followed by characterization using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (FT-IR) and mass spectrometry (MS). Based on the spectroscopic, spectrometric and elemental analysis data unknown impurities were characterized as 5-acetyl-5,11-dihydro-10H-dibenzo [b,f]azepin-10-one, N-acetyl-5H-dibenzo[b,f]azepine-5-carboxamide, 5-acetyl-10,11-dihydro-5H-dibenzo[b,f]azepin-10-yl acetate and 5-acetyl-5H-dibenzo[b,f]azepin-10-yl acetate. The newly developed LC-UV method was validated according to ICH guidelines considering eleven potential impurities and four new impurities to demonstrate specificity, precision, linearity, accuracy and stability indicating nature of the method. The newly developed method was found to be highly efficient, selective, sensitive and stability indicating. A plausible pathway for the formation of four new impurities is proposed. PMID:22178334

Thomas, Saji; Bharti, Amber; Maddhesia, Pawan Kumar; Shandilya, Sanjeev; Agarwal, Ashutosh; Dharamvir; Biswas, Sujay; Bhansal, Vikas; Gupta, Ashish Kumar; Tewari, Praveen Kumar; Mathela, Chandra S

2012-03-01

20

Development and validation of a stability-indicating RP-HPLC method for the simultaneous estimation of process related impurities and degradation products of rasagiline mesylate in pharmaceutical formulation.  

PubMed

A sensitive, stability-indicating gradient reverse phase high-performance liquid chromatography-ultraviolet method has been developed for the quantitative determination of process-related impurities and forced degradation products of rasagiline mesylate in pharmaceutical formulation. Efficient chromatographic separation was achieved on an ACE C8, 150 × 4.6 mm, 3 µm column with mobile phase containing a gradient mixture of solvents A and B. The flow rate of the mobile phase was 0.8 mL/min with column temperature of 30°C and detection wavelength at 210 nm. Rasagiline was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Rasagiline was found to degrade significantly in acid and thermal stress conditions. The degradation products were well resolved from rasagiline and its impurities. The peak purity test results confirmed that the rasagiline peak was homogenous and pure in all stress samples and the mass balance was found to be more than 97%, thus proving the stability-indicating power of the method. The developed method was validated according to the guidelines of the International Conference on Harmonization with respect to specificity, linearity, limits of detection and quantification, accuracy, precision and robustness. PMID:22988002

Reddy, P Sunil; Sudhakar Babu, K; Kumar, Navneet

2013-03-01

21

Development and Validation of a Stability Indicating RP-HPLC Method for Hydrocortisone Acetate Active Ingredient, Propyl Parahydroxybenzoate and Methyl Parahydroxybenzoate Preservatives, Butylhydroxyanisole Antioxidant, and Their Degradation Products in a Rectal Gel Formulation.  

PubMed

A stability indicating method was established through a stress study, wherein different methods of degradation (oxidation, hydrolysis, photolysis, and temperature) were studied simultaneously to determine the active ingredient hydrocortisone acetate, preservatives propyl parahydroxybenzoate, and methyl parahydroxybenzoate, antioxidant butylhydroxyanisole (BHA), and their degradation products in a semisolid dosage gel form. The proposed method was suitably validated using a Zorbax SB-Phenyl column and gradient elution. The mobile phase consisted of a mixture of methanol, acetonitrile, and water in different proportions according to a planned program at a flow rate of 1.5 mL/min. The diode array detector was set at 240 nm for the active substance and two preservatives, and 290 nm for BHA. The validation study was conducted according to International Conference on Harmonization guidelines for specificity, linearity, repeatability, precision, and accuracy. The method was used for QC of hydrocortisone acetate gel and for the stability studies with the aim of quantifying the active substance, preservatives, antioxidant, and degradation products. It has proved to be suitable as a fast and reliable method for QC. PMID:25857875

Ascaso, Magda; Pérez-Lozano, Pilar; García, Mireia; García-Montoya, Encarna; Miñarro, Montse; Ticó, Josep R; Fàbregas, Anna; Carrillo, Carolina; Sarrate, Rocío; Suñé-Negre, Josep M

2015-01-01

22

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

2013-01-01

23

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. PMID:24106668

Kumar, Navneet; Sangeetha, Dhanaraj

2013-01-01

24

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

2011-01-01

25

RP-HPLC ANALYSIS OF HYDROPHOBIC ALENDRONATE AMIDATED DERIVATIVES  

Microsoft Academic Search

The reversed phase high performance liquid chromatography (RP-HPLC) was evaluated for its application in the analysis of the quantiation of the alendronate derivatives. The anti-phase Agilent CLC-ODS C18 column was used at the temperature of 50°C. The RP-HPLC trace was monitored with a differential refractive index detector for the lack of ultraviolet (UV) absorbing groups in the derivative molecule. The

Ting Li Lu; Hui Jing Hu; Wen Zhao; Tao Chen

2010-01-01

26

Monitoring of Impurity Level of Valsartan and Hydrochlorothiazide Employing an RP–HPLC Gradient Mode  

Microsoft Academic Search

The multi?component preparation Co–Diovan is indicated for the hypertension treatment in patients whose blood pressure is not adequately controlled by monotherapy. Its active ingredients are valsartan and hydrochlorothiazide.The reversed–phase high performance liquid chromatographic method (RP–HPLC) for the determination of valsartan and hydrochlorothiazide, as well as their impurities level, was developed and described in this paper. As the investigated substances were

Darko Ivanovi?; An?elija Malenovi?; Biljana Jan?i?; Mirjana Medenica; Marija Maškovi?

2007-01-01

27

Simultaneous determination of mebendazole and pyrantel pamoate from tablets by high performance liquid chromatography-reverse phase (RP-HPLC).  

PubMed

A new, simple, precise, rapid and stability indicating RP-HPLC method has been developed for the simultaneous determination of mebendazole and pyrantel pamoate from tablets. Chromatography was carried out on a Shodex C8 column using a mixture of 0.05 M monobasic sodium phosphate: acetonitrile: triethylamine (60:40:1.5, v/v), adjusted to pH 6.8 with phosphoric acid. Detection was carried out at 290 nm using a UV detector. Retention times for pamoic acid, pyrantel base and mebendazole were 3.61, 6.41 and 12.81 min, respectively. Linearity was obtained in the concentration range of 20-160 mug and 30-240 mug for pyrantel pamoate and mebendazole, respectively. The method after its application for the assay of pyrantel pamoate and mebendazole from tablets, was statistically evaluated for its accuracy and precision. PMID:18966940

Argekar, A P; Raj, S V; Kapadia, S U

1997-11-01

28

A stability-indicating HPLC method for medroxyprogesterone acetate in bulk drug and injection formulation  

Microsoft Academic Search

A stability-indicating HPLC assay method has been developed and validated for medroxyprogesterone acetate (MPA) in bulk drug and injectable suspension. An isocratic RP-HPLC was achieved on a Hichrom C18 column (150mm×4.6mm i.d., 5?m) utilizing a mobile phase of methanol 0.020M acetate buffer pH 5 (65:35, v\\/v) and a photodiode array detector at 245nm. The stress testing of MPA was carried

Jankana Burana-osot; Sooksri Ungboriboonpisal; Lawan Sriphong

2006-01-01

29

Simultaneous RP-HPLC Estimation of Cefpodoxime Proxetil and Clavulanic Acid in Tablets.  

PubMed

A new, simple, precise, rapid and accurate RP-HPLC method has been developed for the simultaneous estimation of cefpodoxime proxetil and clavulanic acid from pharmaceutical dosage forms. The method was carried out on a Zorbax Eclipse XDB 5 mu C 18 (150x4.6 mm) column with a mobile phase consisting of acetonitrile:50 mM potassium dihydrogen phosphate buffer (pH 3.0, 70:30 v/v) at a flow rate of 1.0 ml/min. Detection was carried out at 228 nm. Aspirin was used as an internal standard. The retention time of clavulanic acid, cefpodoxime proxetil and aspirin was 4.43, 6.44 and 5.6 min, respectively. The developed method was validated in terms of accuracy, precision, linearity, limit of detection, limit of quantification and solution stability. The proposed method can be used for the estimation of these drugs in combined dosage forms. PMID:20177474

Malathi, S; Dubey, R N; Venkatnarayanan, R

2009-01-01

30

Simultaneous RP-HPLC Estimation of Cefpodoxime Proxetil and Clavulanic Acid in Tablets  

PubMed Central

A new, simple, precise, rapid and accurate RP-HPLC method has been developed for the simultaneous estimation of cefpodoxime proxetil and clavulanic acid from pharmaceutical dosage forms. The method was carried out on a Zorbax Eclipse XDB 5 ? C 18 (150×4.6 mm) column with a mobile phase consisting of acetonitrile:50 mM potassium dihydrogen phosphate buffer (pH 3.0, 70:30 v/v) at a flow rate of 1.0 ml/min. Detection was carried out at 228 nm. Aspirin was used as an internal standard. The retention time of clavulanic acid, cefpodoxime proxetil and aspirin was 4.43, 6.44 and 5.6 min, respectively. The developed method was validated in terms of accuracy, precision, linearity, limit of detection, limit of quantification and solution stability. The proposed method can be used for the estimation of these drugs in combined dosage forms. PMID:20177474

Malathi, S.; Dubey, R. N.; Venkatnarayanan, R.

2009-01-01

31

Development and validation of RP-HPLC method to determine anti-allergic compound in Thai traditional remedy called Benjalokawichien.  

PubMed

Benjalokawichien (BLW) or Ya-Ha-Rak (HR) is a traditional remedy in the Nationaldrug list of herbal medicinal products AD 2012 of Thailand. For traditional use, BLW is used as antipyretic agent. It also has anti-allergic effect, particularly treating allergic rash. The ethanolic extract of BLW exhibited anti-allergic activity via inhibitory effect against a release ofbeta-hexosaminidase in RBL-2H3 cell line. Pectolinarigenin has been identified as the active compound ofBLW extract. In this study, a reversed-phase high performance liquid chromatography (RP-HPLC) method was developed in order to control quality ofpreparation in three aspects such as chemical fingerprint, quantification and stability of the ethanolic extract. The RP-HPLC was performed with a gradient mobile phase composed of 0.1% ortho phosphoric acid and acetronitrile, and peaks were detected at 331 nm. Based on validation results, this analytical method is precise, accurate and stable for quantitative determination ofpectolinarigenin. The amount ofpectolinarigenin in Benjalokawichien extract determined by this method was 18.50 mg/g ofextract. Therefore, this method could be consideredfor quality control ofBLWextract. PMID:25518297

Sakpakdeejaroen, Intouch; Juckmeta, Thana; Itharat, Arunporn

2014-08-01

32

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

2006-02-15

33

Preparation of (+)-trans-isoalliin and its isomers by chemical synthesis and RP-HPLC resolution.  

PubMed

Naturally occurring (+)-trans-isoalliin, (R(C)R(S))-(+)-trans-S-1-propenyl-L-cysteine sulfoxide, is a major cysteine sulfoxide in onion. The importance of producing it synthetically to support further research is very well recognized. The (+)-trans-isoalliin is prepared by chemical synthesis and reversed-phase (RP)-HPLC. First, S-2-propenyl-L-cysteine (deoxyalliin) is formed from L-cysteine and allyl bromide, which is then isomerized to S-1-propenyl-L-cysteine (deoxyisoalliin) by a base-catalyzed reaction. A mixture of cis and trans forms of deoxyisoalliin is formed and separated by RP-HPLC. Oxidation of the trans form of deoxyisoalliin by H2O2 produces a mixture of (-)- and (+)-trans-isoalliin. Finally, RP-HPLC is used successfully in separating (-)- and (+)-trans-isoalliin, and hence, (+)-trans-isoalliin is synthesized for the first time in this study. In addition, the (±) diastereomers of cis-isoalliin are also separated and purified by RP-HPLC. PMID:25187757

Jayathilaka, Lasanthi; Gupta, Shalini; Huang, Jin-Sheng; Lee, Jenny; Lee, Bao-Shiang

2014-09-01

34

Optimization of separation and determination of moxifloxacin and its related substances by RP-HPLC  

Microsoft Academic Search

A RP-HPLC method for the separation and determination of impurities of moxifloxacin, in its pharmaceutical forms as well as moxifloxacin degradation products, was developed with the aid of DryLab® software and chemometric (response surface) approach. The separation of four synthesis-related impurities was achieved on a Waters C18 XTerra column using a mobile phase of (water+triethylamine (2%, v\\/v)): acetonitrile=90:10 (v\\/v%); the

Predrag Djurdjevic; Andrija Ciric; Aleksandra Djurdjevic; Milena Jelikic Stankov

2009-01-01

35

Quantitative Analysis of Quercetin in Euphorbia helioscopia L by RP-HPLC  

Microsoft Academic Search

Euphorbia helioscopia L is widespread in China and has a large number of flavonoids. Quercetin glycosides, having useful biological activities,\\u000a are abundant in this plant, and no validated analytical method has so far been developed for their determination. We, therefore,\\u000a standardized a reversed-phase high-performance liquid chromatography (RP-HPLC) assay for quercetin detection. For this, the\\u000a plant was locally procured and identification

Hai Peng Liu; Xiao Feng Shi; You Cheng Zhang; Zhong Xin Li; Lin Zhang; Zhe Yuan Wang

36

Precipitation behaviour of caseinomacropeptides and their simultaneous determination with whey proteins by RP-HPLC  

Microsoft Academic Search

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method on polyvinylbenzene\\/divinylbenzene copolymer resin was applied for the quantitative determination of glycosylated and non-glycosylated caseinomacropeptides (CMP), in presence of the major whey proteins (?-lactalbumin and ?-lactoglobulin). The peak profile of the CMP-fractions was calibrated using the response factor determined by amino acid analysis. By omitting any critical precipitation step (e.g. trichloroacetic acid, TCA)

Corinna Thomä; Ingolf Krause; Ulrich Kulozik

2006-01-01

37

Quantitative analysis of quercetin in Euphorbia helioscopia L by RP-HPLC.  

PubMed

Euphorbia helioscopia L is widespread in China and has a large number of flavonoids. Quercetin glycosides, having useful biological activities, are abundant in this plant, and no validated analytical method has so far been developed for their determination. We, therefore, standardized a reversed-phase high-performance liquid chromatography (RP-HPLC) assay for quercetin detection. For this, the plant was locally procured and identification was confirmed based on its morpho-histological characteristics. Ethyl acetate extracts of leaves, stems, and roots were analyzed by RP-HPLC using Agilent 1120 HPLC TC-C(18) column (250 × 4.6 mm; 5 ?m) with UV-detector system. The mobile phase of methanol-0.2% phosphoric acid (65:35) solution was used with the flow rate of 1.0 ml min(-1) at 30°C, and the detection was performed at 360 nm wavelength. Our data show that the linear range of quercetin was 0.025-0.150 mg.ml(-1) (r = 0.9995; n = 6) with the recovery rate of 97.50-103.30% (average 100.40%; RSD = 2.28%). The target component was baseline separated during only the period of 9 min. The repeatability of RP-HPLC analysis was demonstrated with an RSD of 1.77% (n = 6), and the highest quercetin content (average 1.42 mg g(-1)dry-weight) was present in leaves. It was, therefore, concluded that RP-HPLC is a simple, rapid, accurate, and sensitive method for the detection of quercetin from Euphorbia helioscopia L. PMID:21327945

Liu, Hai Peng; Shi, Xiao Feng; Zhang, You Cheng; Li, Zhong Xin; Zhang, Lin; Wang, Zhe Yuan

2011-09-01

38

A Study of Method Development, Validation, and Forced Degradation for Simultaneous Quantification of Paracetamol and Ibuprofen in Pharmaceutical Dosage Form by RP-HPLC Method  

PubMed Central

A rapid and stability-indicating reversed phase high-performance liquid chromatography (RP-HPLC) method was developed for simultaneous quantification of paracetamol and ibuprofen in their combined dosage form especially to get some more advantages over other methods already developed for this combination. The method was validated according to United States Pharmacopeia (USP) guideline with respect to accuracy, precision, specificity, linearity, solution stability, robustness, sensitivity, and system suitability. Forced degradation study was validated according to International Conference on Harmonisation (ICH). For this, an isocratic condition of mobile phase comprising phosphate buffer (pH 6.8) and acetonitrile in a ratio of 65:35, v/v at a flow rate of 0.7 mL/minute over RP C18 (octadecylsilane (ODS), 150 × 4.6 mm, 5 ?m, Phenomenex Inc.) column at ambient temperature was maintained. The method showed excellent linear response with correlation coefficient (R2) values of 0.999 and 1.0 for paracetamol and ibuprofen respectively, which were within the limit of correlation coefficient (R2 > 0.995). The percent recoveries for two drugs were found within the acceptance limit of (97.0–103.0%). Intra-and inter-day precision studies of the new method were less than the maximum allowable limit percentage of relative standard deviation (%RSD) ? 2.0. Forced degradation of the drug product was carried out as per the ICH guidelines with a view to establishing the stability-indicating property of this method and providing useful information about the degradation pathways, degradation products, and how the quality of a drug substance and drug product changes with time under the influence of various stressing conditions. The degradation of ibuprofen was within the limit (5–20%, according to the guideline of ICH), while paracetamol showed <20% degradation in oxidation and basic condition. PMID:25452691

Jahan, Md. Sarowar; Islam, Md. Jahirul; Begum, Rehana; Kayesh, Ruhul; Rahman, Asma

2014-01-01

39

Determination of log P values of new cyclen based antimalarial drug leads using RP-HPLC.  

PubMed

Lipophilicity, expressed by log P, is an important physicochemical property of drugs that affects many biological processes, including drug absorption and distribution. The main purpose of this study to determine the log P values of newly discovered drug leads using reversed-phase high-performance liquid chromatography (RP-HPLC). The reference standards, with varying polarity ranges, were dissolved in methanol and analyzed by RP-HPLC using a C18 column. The mobile phase consisted of a mixture of acetonitrile, methanol and water in a gradient elution mode. A calibration curve was plotted between the experimental log P values and obtained log k values of the reference standard compounds and a best fit line was obtained. The log k values of the new drug leads were determined in the same solvent system and were used to calculate the respective log P values by using the best fit equation. The log P vs. log k data gave a best fit linear curve that had an R2 of 0.9786 with Pvalues of the intercept and slope of 1.19 x 10(-6) and 1.56 x 10(-10), respectively, at 0.05 level of significance. Log P values of 15 new drug leads and related compounds, all of which are derivatives of macrocyclic polyamines and their metal complexes, were determined. The values obtained are closely related to the calculated log P (Clog P) values using ChemDraw Ultra 12.0. This experiment provided efficient, fast and reasonable estimates of log P values of the new drug leads by using RP-HPLC. PMID:25272935

Rudraraju, A V; Amoyaw, P N A; Hubin, T J; Khan, M O F

2014-09-01

40

SIMULTANEOUS DETERMINATION OF LOSARTAN POTASSIUM AND HYDROCHLOROTHIAZIDE FROM TABLETS AND HUMAN SERUM BY RP-HPLC  

Microsoft Academic Search

A new, simple, precise, rapid, and accurate RP-HPLC method has been developed for the simultaneous determination of losartan potassium and hydrochlorothiazide from tablets and human serum. Chromatography was carried out on a C18 reversed-phase column using a mixture of 0.01 M KH2PO4: acetonitrile (65:35; v\\/v) adjusted to pH 3.1 with H3PO4 at a flow rate 1.0 mL\\/min.Detection was realised at

Sibel A. Özkan

2001-01-01

41

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

PubMed

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 numerous morphologically similar specimens of the Hadronyche infensa species group collected from a variety of geographic locations in southeast Queensland. Analysis of the crude venoms using online reversed-phase high performance liquid chromatography/electrospray ionisation mass spectrometry (rp-HPLC/ESI-MS) revealed that the venom profiles provide a useful means of specimen identification, from the species level to species variants. Tables defining the descriptor molecules for each group of specimens were constructed and provided a quick reference of the relationship between one specimen and another. The study revealed that the morphologically similar specimens from the southeast Queensland region are a number of different species/species variants. Furthermore, the study supports aspects of the current taxonomy with respect to the H. infensa species group. Analysis of Australian Funnel-web spider venom by rp-HPLC/ESI-MS provides a rapid and accurate method of species/species variant identification. PMID:16554080

Wilson, David; Alewood, Paul F

2006-05-01

42

RP-HPLC method development and validation for simultaneous estimation of atorvastatin calcium and pioglitazone hydrochloride in pharmaceutical dosage form.  

PubMed

A simple, selective, rapid, precise and economical reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed for simultaneous estimation of atorvastatin calcium (ATV) and pioglitazone hydrochloride (PIO) from pharmaceutical formulation. The method is carried out on a C8 (25 cm × 4.6 mm i.d., 5 ?m) column with a mobile phase consisting of acetonitrile (ACN):water (pH adjusted to 6.2 using o-phosphoric acid) in the ratio of 45:55 (v/v). The retention time of ATV and PIO is 4.1 and 8.1 min, respectively, with the flow rate of 1 mL/min with diode array detector detection at 232 nm. The linear regression analysis data from the linearity plot showed good linear relationship with a correlation coefficient (R(2)) value for ATV and PIO of 0.9998 and 0.9997 in the concentration range of 10-80 µg mL(-1), respectively. The relative standard deviation for intraday precision has been found to be <2.0%. The method is validated according to the ICH guidelines. The developed method is validated in terms of specificity, selectivity, accuracy, precision, linearity, limit of detection, limit of quantitation and solution stability. The proposed method can be used for simultaneous estimation of these drugs in marketed dosage forms. PMID:24152592

Peraman, Ramalingam; Mallikarjuna, Sasikala; Ammineni, Pravalika; Kondreddy, Vinod kumar

2014-10-01

43

Monitoring seasonal variation of epicatechin and gallic acid in the bark of Saraca asoca using reverse phase high performance liquid chromatography (RP-HPLC) method  

PubMed Central

Background: Saraca asoca (Roxb.) Wilde (Fabaceae) is a high valued but vulnerable medicinal plant of Western Ghats region. This plant is mainly known for its use in various gynecological disorders. Objective: The objective of the present study was to investigate seasonal variation of the polyphenolic compounds viz., epicatechin and gallic acid in the bark of S. asoca by using Reverse Phase High Performance Liquid Chromatography-Diode Array Detector (RP-HPLC-DAD) method. Materials and Methods: The bark was collected in six different Ritu (season) viz. Varsha (monsoon), Sharad (autumn), hemant (early winter), Shishir (winter), Vasanta (spring), and Grishma (summer) mentioned in Ayurveda. Results: The RP-HPLC-DAD analysis indicated that levels of epicatechin and gallic acid in the bark of S. asoca vary seasonally. The highest concentration of epicatechin was observed in Shishir Ritu (3315.19 ± 165.76 mg/100g) and gallic acid during Hemant Ritu (211.90 ± 10.60 mg/100 g). Conclusions: In present study, the ability to synthesize and accumulate both the compounds in bark of S. asoca varied greatly throughout the seasons. It was also observed that the compound epicatechin was present abundantly as compared to gallic acid throughout the seasons. PMID:25878461

Ketkar, Pushkar M.; Nayak, Shraddha U.; Pai, Sandeep R.; Joshi, Rajesh K.

2015-01-01

44

DEVELOPMENT AND VALIDATION OF A STABILITY INDICATING HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC (HPLC) METHOD FOR ATENOLOL AND HYDROCHLORTHIAZIDE IN BULK DRUG AND TABLET FORMULATION  

Microsoft Academic Search

A new simple, rapid, precise, accurate, specific and stability indicating assay method was developed for simultaneous estimation of Atenolol (ATN) and Hydrochlorthiazide (HCZ) in pure form and tablet form. The analytes were separated by RP HPLC on a Hypersil-BDS C18 column (250X4.6mm i.d., 5mm).The mobile phase was 25mMphosphate buffer (PH 3±0.05): acetonitrile (85:15, v\\/v) at 0.7 mL\\/min satisfactorily resolved the

S. P. GANDHI; S. J. RAJPUT

45

Determination of some phenolic compounds in red wine by RP-HPLC: method development and validation.  

PubMed

A methodology employing reversed-phase high-performance liquid chromatography (RP-HPLC) was developed and validated for simultaneous determination of five phenolic compounds in red wine. The chromatographic separation was carried out in a C(18) column with water acidify with acetic acid (pH 2.6) (solvent A) and 20% solvent A and 80% acetonitrile (solvent B) as the mobile phase. The validation parameters included: selectivity, linearity, range, limits of detection and quantitation, precision and accuracy, using an internal standard. All calibration curves were linear (R(2) > 0.999) within the range, and good precision (RSD < 2.6%) and recovery (80-120%) was obtained for all compounds. This method was applied to quantify phenolics in red wine samples from Santa Catarina State, Brazil, and good separation peaks for phenolic compounds in these wines were observed. PMID:21859541

Burin, Vívian Maria; Arcari, Stefany Grützmann; Costa, Léa Luzia Freitas; Bordignon-Luiz, Marilde T

2011-09-01

46

Stability indicating studies on NMITLI 118RT+ (standardized extract of withania somnifera dunal)  

PubMed Central

Background: Withania somnifera Dunal (Ashwagandha) is an Indian medicinal plant of great medicinal value; used in many clinically proven conditions. NMITLI-118RT+ is a candidate drug under a Council of Scientific and Industrial Research (CSIR) networking project. It is a chemotype of W. somnifera's root extract, which has been used for the present study. Objectives: The present investigation aims to develop and validate a simple isocratic reverse phase-high performance liquid chromatography (RP-HPLC) system for the detection and estimation of Withanolide A (marker compound) and its analytical application for stability indicating studies on NMITLI-118RT+. Material and Methods: A validated RP-HPLC method for Withanolide A was established on a Waters HPLC system and the same was used on NMITLI-118RT+ for quantification and fingerprinting purposes, and for establishing forced degradation, isothermal stress tests, and drug-excipient testing protocols as per International Conference on Harmonization (ICH) guidelines. Results: A validated method was established, which could detect the marker at a retention time of around 6.3 minutes, with a linearity range of 2-100 ?g/mL, by varying the amounts of the said marker, which were estimated in four different batches of NMITLI-118RT+. Photostability as per ICH guidelines suggested a slight loss of the active constituent and maximum degradation was afforded with alkali followed by acid, and then peroxide, in the forced degradation studies. In the drug-excipient studies, the maximum amount of active constituent could be detected in the samples with ethyl cellulose and the least with hydroxy propyl cellulose. Conclusion: The method developed here was simple and rapid. The various stability indicating studies carried out in the present investigation would be useful for formulation development and were suggestive of deciding the recommended storage conditions for NMITLI-118RT+. PMID:25210308

Ahmad, Hafsa; Khandelwal, Kiran; Pachauri, Shakti Deep; Sanghwan, Rajender Singh; Dwivedi, Anil Kumar

2014-01-01

47

RP-HPLC analysis of flucloxacillin in human plasma: validation and application to a bioequivalence study.  

PubMed

A RP-HPLC method with rapid sample processing was developed for quantitation of flucloxacillin in human plasma using dicloxacillin as the internal standard. The plasma sample (100 microL) was acidified with glacial acetic acid, and deproteinized by precipitation with acetonitrile. The supernatant was directly injected into the HPLC system. Separation was achieved on an Alltima C18 column (250 mmx4.6 mm I.D., 5 microm), with a mixture of 10 mmol x L(-1) KH2PO4-acetonitrile (64.5:35.5, v/v) as mobile phase. The assay was successfully applied to a randomized, two-period cross-over bioequivalence study in 20 healthy Chinese volunteers following a single oral dose of 250 mg flucloxacillin capsules. A non-compartmental method was used for pharmacokinetic analysis. Compared with data in the literature, flucloxacillin was eliminated more slowly in Chinese than in Caucasians. Cmax, AUC(0-t) and AUC(0-infinity) were tested for bioequivalence after log-transformation of data. No significant difference was found. Tmax was analyzed by Wilcoxon's test and no significant difference was obtained (P > 0.05). Based on these statistical inferences, the two formulations were judged to be bioequivalent and, thus, can be prescribed interchangeably. PMID:17341027

Zhou, Q; Ruan, Z; Yuan, H; Jiang, B; Xu, D

2007-02-01

48

An application of RP-HPLC for determination of the activity of cystathionine ?-synthase and ?-cystathionase in tissue homogenates.  

PubMed

The RP-HPLC-based method of determination of the activity of cystathionine ?-synthase and ?-cystathionase was undertaken in mouse liver, kidney and brain. Products of the reactions, such as cystathionine, ?-ketobutyrate, cysteine and glutathione, were measured using the RP-HPLC method. A difference in the cystathionine level between homogenates with totally CTH-inhibiting concentrations of DL-propargylglycine and without the inhibitor was employed to evaluate the activity of cystathionine ?-synthase. Gamma-cystathionase activity was measured using DL-homoserine as a substrate and a sensitive HPLC-based assay to measure ?-ketobutyrate. The results confirmed high cystathionine ?-synthase activity and no ?-cystathionase activity in brain, and high ?-cystathionase activity in mouse liver. The method presented here allows for evaluating the relative contribution of CBS and CTH to generation of H2S in tissues. Additionally, it provides results, which reflect the redox status (GSH/GSSG) of a tissue. PMID:25307719

Bronowicka-Adamska, Patrycja; Zagajewski, Jacek; Wróbel, Maria

2015-04-30

49

RP-HPLC\\/MS-APCI Analysis of Branched Chain TAG Prepared by Precursor-Directed Biosynthesis with Rhodococcus erythropolis  

Microsoft Academic Search

Reversed phase liquid chromatography–atmospheric pressure chemical ionization mass spectrometry (RP-HPLC\\/MS-APCI) was used\\u000a to analyze both synthetic triacylglycerols (TAG) having 1–3 branched fatty acids (FA) in the molecule, and natural TAG prepared\\u000a by precursor directed biosynthesis from valine, leucine and isoleucine and the corresponding branched short-chain acids in\\u000a cultivations of Rhodococcus erythropolis. The technique made it possible to identify and quantify

Olga Schreiberová; Tereza Krulikovská; Karel Sigler; Alena ?ejková; Tomáš ?ezanka

2010-01-01

50

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

PubMed

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 be satisfactory. Phenolic acid derivatives in anatomical parts of SB berries and leaves were separated into free phenolic acids, phenolic acids bound as esters and phenolic acids bound as glycosides and profiled in HPLC. Berry pulp contained a total of 1068 mg/kg phenolic acids, of which 58.8% was derived from phenolic glycosides. Free phenolic acids and phenolic acid esters constituted 20.0% and 21.2%, respectively, of total phenolic acids in SB berry pulp. The total phenolic acid content in seed kernel (5741 mg/kg) was higher than that in berry pulp and seed coat (Table 2). Phenolic acids liberated from soluble esters constituted the major fraction of phenolic acids (57.3% of total phenolic acids) in seed kernel. 8.4% and 34.3% of total phenolic acids in seed kernel were, respectively contributed by free and phenolic acids liberated from glycosidic bonds. The total soluble phenolic acids content in seed coat (448 mg/kg) was lower than that in seed kernel and pulp (Table 2). Proportion of free phenolic acids in total phenolic acids in seed coat was higher than that in seed kernel and pulp. Phenolic acids bound as esters and glycosides, respectively contributed 49.1% and 20.3% of total phenolic acids in seed coat. The major fraction (approximately 70%) of phenolic acids in SB berries was found to be concentrated in the seeds. Gallic acid was the predominant phenolic acid both in free and bound forms in SB berry parts and leaves. PMID:18194847

Arimboor, Ranjith; Kumar, K Sarin; Arumughan, C

2008-05-12

51

An Experimental Design Approach for Impurity Profiling of Valacyclovir-Related Products by RP-HPLC.  

PubMed

Impurity profiling has become an important phase of pharmaceutical research where both spectroscopic and chromatographic methods find applications. The analytical methodology needs to be very sensitive, specific, and precise which will separate and determine the impurity of interest at the 0.1% level. Current research reports a validated RP-HPLC method to detect and separate valacyclovir-related impurities (Imp-E and Imp-G) using the Box-Behnken design approach of response surface methodology. A gradient mobile phase (buffer: acetonitrile as mobile phase A and acetonitrile: methanol as mobile phase B) was used. Linearity was found in the concentration range of 50-150 ?g/mL. The mean recovery of impurities was 99.9% and 103.2%, respectively. The %RSD for the peak areas of Imp-E and Imp-G were 0.9 and 0.1, respectively. No blank interferences at the retention times of the impurities suggest the specificity of the method. The LOD values were 0.0024 ?g/mL for Imp-E and 0.04 ?g/mL for Imp-G and the LOQ values were obtained as 0.0082 ?g/mL and 0.136 ?g/mL, respectively, for the impurities. The S/N ratios in both cases were within the specification limits. Proper peak shapes and satisfactory resolution with good retention times suggested the suitability of the method for impurity profiling of valacyclovir-related drug substances. PMID:25853072

Katakam, Prakash; Dey, Baishakhi; Hwisa, Nagiat T; Assaleh, Fathi H; Chandu, Babu R; Singla, Rajeev K; Mitra, Analava

2014-09-01

52

An Experimental Design Approach for Impurity Profiling of Valacyclovir-Related Products by RP-HPLC  

PubMed Central

Abstract Impurity profiling has become an important phase of pharmaceutical research where both spectroscopic and chromatographic methods find applications. The analytical methodology needs to be very sensitive, specific, and precise which will separate and determine the impurity of interest at the 0.1% level. Current research reports a validated RP-HPLC method to detect and separate valacyclovir-related impurities (Imp-E and Imp-G) using the Box-Behnken design approach of response surface methodology. A gradient mobile phase (buffer: acetonitrile as mobile phase A and acetonitrile: methanol as mobile phase B) was used. Linearity was found in the concentration range of 50–150 ?g/mL. The mean recovery of impurities was 99.9% and 103.2%, respectively. The %RSD for the peak areas of Imp-E and Imp-G were 0.9 and 0.1, respectively. No blank interferences at the retention times of the impurities suggest the specificity of the method. The LOD values were 0.0024 ?g/mL for Imp-E and 0.04 ?g/mL for Imp-G and the LOQ values were obtained as 0.0082 ?g/mL and 0.136 ?g/mL, respectively, for the impurities. The S/N ratios in both cases were within the specification limits. Proper peak shapes and satisfactory resolution with good retention times suggested the suitability of the method for impurity profiling of valacyclovir-related drug substances.

Katakam, Prakash; Dey, Baishakhi; Hwisa, Nagiat T; Assaleh, Fathi H; Chandu, Babu R; Singla, Rajeev K; Mitra, Analava

2014-01-01

53

Development and validation of stability-indicating HPLC method for simultaneous determination of meropenem and potassium clavulanate.  

PubMed

A stability-indicating LC assay method was developed and validated for a simultaneous determination of meropenem and potassium clavulanate in the presence of degradation products formed during acid-base hydrolysis, oxidation and thermolysis. The isocratic RP-HPLC method was developed with a LiChrospher RP-18 (250 mm x 4.6 mm, 5 microm) column and gradient elution of 12 mmol/L ammonium acetate and acetonitrile. The flow rate of the mobile phase was 1.0 mL/min, the detection wavelength 220 nm and the temperature 303 K. The method was validated with regard to linearity, accuracy, precision, selectivity and robustness, and was applied successfully for the determination of meropenem and potassium clavulanate separately as well as jointly in pharmaceutical formulations. PMID:25272645

Zalewski, Przemys?aw; Cielecka-Piontek, Judyta; Paczkowska, Magdalena

2014-01-01

54

Development and Validation of an RP-HPLC Method for Quantitative Estimation of Eslicarbazepine Acetate in Bulk Drug and Tablets  

PubMed Central

A convenient, simple, accurate, precise and reproducible RP-HPLC method was developed and validated for the estimation of eslicarbazepine acetate in bulk drug and tablet dosage form. Objective was achieved under optimised chromatographic conditions on Dionex RP-HPLC system with Dionex C18 column (250×4.6 mm, 5 ?m particle size) using mobile phase composed of methanol and ammonium acetate (0.005 M) in the ratio of 70:30 v/v. The separation was achieved using an isocratic elution method with a flow rate of 1.0 ml/ min at room temperature. The effluent was monitored at 230 nm using diode array detector. The retention time of eslicarbazepine acetate is found to be 4.9 min and the standard calibration plot was linear over a concentration range of 10-90 ?g/ml with r2=0.9995. The limit of detection and quantification were found to be 3.144 and 9.52 ?g/ml, respectively. The amount of eslicarbazepine acetate in bulk and tablet dosage form was found to be 99.19 and 97.88%, respectively. The method was validated statistically using the percent relative standard deviation and the values are found to be within the limits. The recovery studies were performed and the percentage recoveries were found to be 98.33± 0.5%. PMID:24591752

Singh, M.; Kumar, L.; Arora, P.; Mathur, S. C.; Saini, P. K.; Singh, R. M.; Singh, G. N.

2013-01-01

55

Development and validation of RP-HPLC-fluorescence method for quantitative determination of quinidine, a probe substrate for P-glycoprotein inhibition assay using Caco-2 cell monolayer.  

PubMed

A simple, sensitive and specific reverse-phase high-performance liquid chromatographic (RP-HPLC) method with fluorescence detection was developed for quantitation of quinidine from HBSS buffer. The method was applicable in the bi-directional transport assay for evaluation of the inhibitory effect of test compounds on P-glycoprotein-mediated quinidine transport; quinidine was used as a probe P-glycoprotein substrate. The calibration curve was linear (correlation coefficient >/=99) in the range 0.30-100.00 nm. The method was validated and is specific and sensitive with limit of quantitation of 300 pm for quinidine. The method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions where the analyte was found to be stable. The applicability and reliability of the analytical method was evaluated by successful demonstration of efflux ratio (P(app)B --> A/P(app)A --> B) in the Caco-2 cell monolayer efflux assay. The efflux ratio for quinidine (100 nm) alone was 10.8, which reduced to less than 2 in the presence of the classical P-gp inhibitors verapamil and ketoconazole (100 mum each). PMID:19816852

Patil, Anand G; Reddy, Dilip; D'Souza, Russell; Damre, Anagha

2010-06-01

56

Development and Validation of Stability-indicating HPLC Method for Simultaneous Estimation of Cefixime and Linezolid  

PubMed Central

A stability-indicating reverse phase high performance liquid chromatography method was developed and validated for cefixime and linezolid. The wavelength selected for quantitation was 276 nm. The method has been validated for linearity, accuracy, precision, robustness, limit of detection and limit of quantitation. Linearity was observed in the concentration range of 2-12 ?g/ml for cefixime and 6-36 ?g/ml for linezolid. For RP-HPLC, the separation was achieved by Phenomenex Luna C18 (250×4.6 mm) 5 ?m column using phosphate buffer (pH 7):methanol (60:40 v/v) as mobile phase with flow rate 1 ml/min. The retention time of cefixime and linezolid were found to be 3.127 min and 11.986 min, respectively. During force degradation, drug product was exposed to hydrolysis (acid and base hydrolysis), H2O2, thermal degradation and photo degradation. The % degradation was found to be 10 to 20% for both cefixime and linezolid in the given condition. The method specifically estimates both the drugs in presence of all the degradants generated during forced degradation study. The developed methods were simple, specific and economic, which can be used for simultaneous estimation of cefixime and linezolid in tablet dosage form. PMID:25593387

Patel, Nidhi S.; Tandel, Falguni B.; Patel, Yogita D.; Thakkar, Kartavya B.

2014-01-01

57

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

2013-04-01

58

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

2014-01-01

59

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

60

Development and validation of a rapid RP-HPLC method for analysis of (-)-copalic acid in copaíba oleoresin.  

PubMed

The Copaifera species (Leguminoseae) are popularly known as 'copaíba' or 'copaíva' and are grown in the states of Amazonas, Pará and Ceará in northern Brazil. The oleoresins obtained from these species have been extensively used owing to their pharmacological potential and their application in cosmetic and pharmaceutical preparations. In the present study, the development and validation of a novel, rapid and efficient RP-HPLC methodology for the analysis of the diterpene (-)-copalic acid (CA), pointed out as the only chemical marker of the Copaifera genus, are described. The regression equation (Y = 26,707x - 29,498) was obtained with good linearity (r(2) = 0.9993) and the limits of quantification and detection were 9.182 and 3.032 µg/mL, respectively. The precision and the accuracy of the method were adequate (lower than 4%). Finally, the validation parameters evaluated were satisfactorily met, so the developed method represents a suitable tool for application in the quality control of such natural products. Further studies aiming to develop analytical methodologies for each Copaifera species using a more representative number of chemical markers should be performed. PMID:22847230

Souza, Ariana Borges; Moreira, Monique Rodrigues; Borges, Carly Henrique Gambeta; Simão, Marília Rodrigues; Bastos, Jairo Kenupp; de Sousa, João Paulo Barreto; Ambrosio, Sérgio Ricardo; Veneziani, Rodrigo Cassio Sola

2013-03-01

61

Stress degradation studies and development of a validated stability-indicating-assay-method for determination of diacerein in presence of degradation products  

PubMed Central

Background: To understand the degradation behavior of diacerein and to develop a simple, rapid, sensitive, and validated RP-HPLC method for the determination of diacerein, in the presence of its degradation products. Materials and Methods: An accurate, sensitive, precise, rapid, and isocratic reversed-phase high-performance liquid chromatography (RP-HPLC) method, equipped with a photo-diode array (PDA) detector for analysis of diacerein in the bulk drug has been developed and validated. The best separation was achieved on a 250 mm × 4.6 mm i.d., 5-?m particle, RP C18 column with 50 : 50 (v/v) of water (pH adjusted to 2.9 with orthophosphoric acid) : acetonitrile as the mobile phase, at a flow rate of 1.0 ml/minute. The detection wavelength was set at 257 nm. Results: The response was a linear function of concentration over the range of 0.50 – 20 ?g/ml (r = 0.999) and the limits of detection and quantitation were 0.1 ?g/ml and 0.50 ?g/ml, respectively. The method was validated in accordance with the International Conference on Harmonization (ICH) guidelines. The drug was subjected to oxidative, hydrolytic, photolytic, and thermal stress. The drug decomposed under alkaline hydrolytic stress conditions and also on thermal degradation and photolysis. It was stable on acid hydrolysis and oxidation. The degradation products produced as a result of this stress did not interfere with the detection of diacerein, and the assay could thus be regarded as stability-indicating. Conclusion: The method was suitable for application in the analysis of formulations of diacerein in quality-control laboratories, because it was simple and rapid, with good accuracy and precision. PMID:23781427

Hamrapurkar, Purnima; Patil, Priti; Desai, Masti; Phale, Mitesh; Pawar, Sandeep

2011-01-01

62

Studies on log Po/w of quinoxaline di-N-oxides: a comparison of RP-HPLC experimental and predictive approaches.  

PubMed

As reported in our previous papers, a series of quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized and studied as anti-tuberculosis agents. Here, the capability of the shake-flask method was studied and the retention time (expressed as log K) of 20 compounds were determined by RP-HPLC analysis. We found that the prediction of log P by the RP-HPLC analysis can result in a high accuracy and can replace the shake-flask method avoiding the experimental problems presented by quinoxaline di-N-oxides. The studied compounds were subjected to the ALOGPS module with the aim of comparing experimental log P(o/w) values and predicted data. Moreover, a preliminary in silico screening of the QSAR relationship was made confirming the influence of reduction peak potential, lipophilicity, H-bond donor capacity and molecular dimension descriptors on anti-tuberculosis activity. PMID:22143549

Moreno, Elsa; Gabano, Elisabetta; Torres, Enrique; Platts, James A; Ravera, Mauro; Aldana, Ignacio; Monge, Antonio; Pérez-Silanes, Silvia

2011-01-01

63

RAPID METHOD FOR ESTIMATING OCTANOL-WATER PARTITION COEFFICIENT (LOG POCT) FROM ISOCRATIC RP-HPLC AND A HYDROGEN BOND ACIDITY TERM (A)  

Microsoft Academic Search

The linear solvation equation approach has been used to describe the octanol\\/water lipophilicity scale (logPoct) and the isocratic retention factors (log k) obtained using reversed phase HPLC with acetonitrile. Both the octanol\\/water partition coefficients and the RP-HPLC retention data obtained from the literature, showed good correlation with the molecular descriptors such as size, excess molar refractivity, H-bond acidity\\/basicity, and polarity\\/dipolarity.

Chau My Du; Klara Valko; Chris Bevan; Derek Reynolds; Michael H. Abraham

2001-01-01

64

Analysis of major tomato xylem organic acids and PITC-derivatives of amino acids by RP-HPLC and UV detection  

Microsoft Academic Search

Major amino acids and organic acids in xylem exudates of tomato plants were separated by reversed phase high performance liquid\\u000a chromatography (RP-HPLC) and quantified by UV detection. Before separation, amino acids were converted into their phenylisothiocyanate\\u000a (PITC) derivatives. In a single run, Asp, Glu, Ser, Gln, His, Thr, Ala, Tyr, Val, Met, Cys, Ile, Leu, Phe, and Lys could be

M. H. M. N. Senden; A. J. G. M. Van Der Meer; J. Limborgh; H. Th. Wolterbeek

1992-01-01

65

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

PubMed Central

Many in vitro experiments aimed at studying 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, as well as 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 for the actual redox potential of the assayed sample, facilitates the direct correlation between biochemical findings and the experimental redox status. Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) is a widely used, well-established tool for the analysis and purification of biomolecules, including proteins and peptides. Here, we describe a simple, robust, and quantitative RP-HPLC method we developed and tested to determine 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

2013-01-01

66

Simultaneous determination of chloramphenicol, dexamethasone and naphazoline in ternary and quaternary mixtures by RP-HPLC, derivative and wavelet transforms of UV ratio spectra.  

PubMed

The application of chemometrics-assisted UV spectrophotometry and RP-HPLC to the simultaneous determination of chloramphenicol, dexamethasone and naphazoline in ternary and quaternary mixtures is presented. The spectrophotometric procedure is based on the first-order derivative and wavelet transforms of ratio spectra using single, double and successive divisors. The ratio spectra were differentiated and smoothed using Savitzky-Golay filter; whereas wavelet transform realized with wavelet functions (i.e. db6, gaus5 and coif3) to obtain highest spectral recoveries. For the RP-HPLC procedure, the separation was achieved on a ZORBAX SB-C18 (150×4.6mm; 5?m) column at ambient temperature and the total run time was less than 7min. A mixture of acetonitrile - 25mM phosphate buffer pH 3 (27:73, v/v) was used as the mobile phase at a flow rate of 1.0mL/min and the effluent monitored by measuring absorbance at 220nm. Calibration graphs were established in the range 20-70mg/L for chloramphenicol, 6-14mg/L for dexamethasone and 3-8mg/L for naphazoline (R(2)>0.990). The RP-HPLC and ratio spectra transformed by a combination of derivative-wavelet algorithms proved to be able to successfully determine all analytes in commercial eye drop formulations without sample matrix interference (mean percent recoveries, 97.4-104.3%). PMID:25546493

Hoang, Vu Dang; Hue, Nguyen Thu; Tho, Nguyen Huu; Nguyen, Hue Minh Thi

2015-03-15

67

A RP-HPLC method for quantification of diclofenac sodium released from biological macromolecules.  

PubMed

Interpenetrating network (IPN) microbeads of sodium carboxymethyl locust bean gum (SCMLBG) and sodium carboxymethyl cellulose (SCMC) containing diclofenac sodium (DS), a nonsteroidal anti-inflammatory drug, were prepared by single water-in-water (w/w) emulsion gelation process using AlCl3 as cross-linking agent in a complete aqueous environment. Pharmacokinetic study of these IPN microbeads was then carried out by a simple and feasible high-performance liquid chromatographic method with UV detection which was developed and validated for the quantification of diclofenac sodium in rabbit plasma. The chromatographic separation was carried out in a Hypersil BDS, C18 column (250 mm × 4.6 mm; 5 m). The mobile phase was a mixture of acetonitrile and methanol (70:30, v/v) at a flow rate of 1.0 ml/min. The UV detection was set at 276 nm. The extraction recovery of diclofenac sodium in plasma of three quality control (QC) samples was ranged from 81.52% to 95.29%. The calibration curve was linear in the concentration range of 20-1000 ng/ml with the correlation coefficient (r(2)) above 0.9951. The method was specific and sensitive with the limit of quantification of 20 ng/ml. In stability tests, diclofenac sodium in rabbit plasma was stable during storage and assay procedure. PMID:23567284

Bhattacharya, Shiv Sankar; Banerjee, Subham; Ghosh, Ashoke Kumar; Chattopadhyay, Pronobesh; Verma, Anurag; Ghosh, Amitava

2013-07-01

68

Validation of a simple RP-HPLC method developed for the quantification of meta-cresol in parathyroid hormones formulation  

PubMed Central

Aim: To develop and validate a rapid and sensitive reverse phase high performance liquid chromatography (RP-HPLC) method with UV detection for quantification of meta-cresol (m-cresol) in pharmaceutical preparation of parathyroid hormone (1–34) (PTH). Materials and Methods: Chromatography was performed on a Jupiter RP C-18 (4.6 mm ID × 250 mm L, porosity 300 Å, particle size 5 ?m) with a guard column (reversed-phase C18 column of 4.6 mm ID × 12.5 mm L, porosity 300 Å, particle size 5 ?m) using a mobile phase containing 0.1% TFA in 60% methanol with isocratic program at 1.0 mL/min flow rate. Detection was carried out at 217 nm. The method was validated as per ICH guidelines for linearity (correlation coefficient = 0.99), range, accuracy, precision, and robustness (n = 9 during accuracy parameter whereas n =15 during linearity and range parameter and n = 6 during repeatability). Robustness was confirmed by considering two factors; age effect of the mobile phase and test sample and with different columns during method development. Results: The method was linear over the concentration range of 75–120 ?g/mL. The precision of the method in terms of relative standard deviation was evaluated from intra- and inter-day replicate injections of system suitability standards of m-cresol using different equipment and different columns. Components of within- and between-batch variances were found to be below 2% (n = 30) and 3%, respectively, which constituted an acceptable level of variation. Retention time was found to be about 5.2 min and 10.9 min for m-cresol and PTH, respectively. Conclusion: The developed method thus has the potential of being useful for routine quality control of m-cresol. PMID:23781457

Rane, Shaligram S.; Ajameri, Alkesh; Mody, Rustom; Padmaja, P.

2011-01-01

69

Enantioselective assay of S(+)- and R(-)-propafenone in human urine by using RP-HPLC with pre-column chiral derivatization  

Microsoft Academic Search

The enantioselective assay for S(+)-and R(-)-propafenone (PPF) in human urine that developed in this work involves extraction\\u000a of propafenone from human urine and using S(+)-propafenone as internal standard, chiral derivatization with 2,3,4,6-tetra-O-?-D-glucopranosyl isothiocyanate, and quantitation by an RP-HPLC system with UV detection (?-220 nm). A baseline separation\\u000a of propafenone enantiomers was achieved on a 5-?m reverse phase ODS column, with

Wu Yong-jiang; Ma Ming-ming; Zeng Su

2004-01-01

70

Development and validation of a stability-indicating column high-performance liquid chromatographic assay method for determination of nebivolol in tablet formulation.  

PubMed

A simple, precise, and accurate isocratic reversed-phase (RP) stability-indicating column high-performance liquid chromatographic (HPLC) assay method was developed and validated for determination of nebivolol in solid pharmaceutical dosage forms. Isocratic RP-HPLC separation was achieved on a Phenomenex Luna C8 (2) column (250 mm x 4.6 mm id, 5 microm particle size) using mobile phase composed of acetonitrile-pH 3.5 phosphate buffer (35 + 65, v/v) at a flow rate of 1.0 mL/min, and detection was performed at 280 nm using a photodiode array detector. The drug was subjected to oxidation, hydrolysis, photolysis, and heat to apply stress conditions. The method was validated for specificity, linearity, precision, accuracy, robustness, and solution stability. The method was linear in the drug concentration range of 40-160 microg/mL with a correlation coefficient of 0.9999. The repeatability relative standard deviation (RSD) for 6 samples was 0.69%, and the intermediate precision (RSD) for 6 samples was 1.39%. The accuracy (recovery) was between 98.57 and 99.55%. Degradation products produced as a result of stress studies did not interfere with detection of nebivolol, and the assay can thus be considered stability-indicating. PMID:18567301

Kachhadia, Pankaj K; Doshi, Ashish S; Joshi, Hitendra S

2008-01-01

71

Isolation, Characterization, and RP-HPLC Estimation of P-Coumaric Acid from Methanolic Extract of Durva Grass (Cynodon dactylon Linn.) (Pers.)  

PubMed Central

P-coumaric acid is a nonflavonoid phenolic acid and is a major constituent of the species Cynodon dactylon Linn. (Pers.). In this study isolation of P-coumaric acid was achieved by preparative TLC and the compound thus isolated was characterised by UV, mass, and H1 NMR spectral analysis. An isocratic RP-HPLC method was developed for the estimation of P-coumaric acid from methanolic extracts of durva grass. The chromatographic separations were achieved by RP-C18 column (250?mm?×?4.6?mm, 5??), Shimadzu LC-20AT Prominence liquid chromatograph, and a mobile phase composed of water?:?methanol?:?glacial acetic acid (65?:?34?:?1?v/v). The flow rate was 1.0?mL/min and the analyses of column effluents were performed using UV-visible detector at 310?nm. Retention time of P-coumaric acid was found to be 6.617?min. This method has obeyed linearity over the concentration range of 2–10??g/mL and the regression coefficient obtained from linearity plot for P-coumaric acid was found to be 0.999. RP-HPLC method was validated in pursuance of ICH guidelines. PMID:25788944

Karthikeyan, Ramadoss; Devadasu, Chapala; Srinivasa Babu, Puttagunta

2015-01-01

72

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. PMID:23641335

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

2013-01-01

73

Isolation, Characterization, and RP-HPLC Estimation of P-Coumaric Acid from Methanolic Extract of Durva Grass (Cynodon dactylon Linn.) (Pers.).  

PubMed

P-coumaric acid is a nonflavonoid phenolic acid and is a major constituent of the species Cynodon dactylon Linn. (Pers.). In this study isolation of P-coumaric acid was achieved by preparative TLC and the compound thus isolated was characterised by UV, mass, and H(1) NMR spectral analysis. An isocratic RP-HPLC method was developed for the estimation of P-coumaric acid from methanolic extracts of durva grass. The chromatographic separations were achieved by RP-C18 column (250?mm?×?4.6?mm, 5??), Shimadzu LC-20AT Prominence liquid chromatograph, and a mobile phase composed of water?:?methanol?:?glacial acetic acid (65?:?34?:?1?v/v). The flow rate was 1.0?mL/min and the analyses of column effluents were performed using UV-visible detector at 310?nm. Retention time of P-coumaric acid was found to be 6.617?min. This method has obeyed linearity over the concentration range of 2-10??g/mL and the regression coefficient obtained from linearity plot for P-coumaric acid was found to be 0.999. RP-HPLC method was validated in pursuance of ICH guidelines. PMID:25788944

Karthikeyan, Ramadoss; Devadasu, Chapala; Srinivasa Babu, Puttagunta

2015-01-01

74

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

2007-03-12

75

Stability indicating reverse phase high performance liquid chromatography method for the estimation of capsaicin  

PubMed Central

Background: Stability Indicating Method (SIM) is a quantitative analytical procedure used to detect a decrease in the amount of the active pharmaceutical ingredient (API) present due to degradation. According to Food and Drug Administration (FDA) guidelines, an SIM is defined as a validated analytical procedure that accurately and precisely measures active ingredients (drug substance or drug product) free from potential interferences, such as degradation products, process impurities, excipients, or other potential impurities, and the FDA recommends that all assay procedures for stability studies be stability indicating. Here in this study we developed simple precise and accurate stability indicating reverse-phase high-performance liquid chromatographic (RP-HPLC) assay to analyze capsaicin (CAP) at concentrations from 70 to 130 ?g/mL. Materials and Methods: HPLC equipped with Photo diode Array (PDA) detector, Pump model 600E of Waters and Empower software. Column used for the separation is ODS (250 × 4.6 mm) with particle size 5 ?m and all the reagents and water were of HPLC grade. Results: The chromatographic separation was carried out using mobile phase Acetonitrile (ACN):water:buffer::75:10:15 with a flow rate of 1 mL/min on a C18 column. The concentration of the eluting compounds was monitored by a UV detector at 280 nm. No interferences were observed when stress conditions were applied and analyzed. Linearity was established using visual method, residuals plot, Dixon, and lack of fitness test. Limit of detection and limit of quantification was found to be 52.9 and 160 ng/mL, respectively. Recovery studies prove this method as useful in recovering the analytes. Relative Standard Deviation (RSD) of inter- and intraday precision within the acceptable limit of 2% proves that this method is precise. No degradation was found with alkaline conditions, thermal and photodegradation. Conclusions: This study can be used for successful separation of CAP and its potential degradants in bulk and formulations. UV spectra of one of the degradants are also presented here and can be the basis to generate chemistry of potential degradants when CAP is kept under environmental conditions. PMID:23781444

Shrivastava, Alankar; Saxena, Prachi

2011-01-01

76

A Novel Ion-Pair RP-HPLC Method for Simultaneous Quantification of Naproxen and Esomeprazole in Pharmaceutical Formulations.  

PubMed

A rapid, sensitive and stability indicating ion-pair reversed-phase high-performance liquid chromatographic method was developed for simultaneous estimation of naproxen (NPX) and esomeprazole (ESP) in pharmaceutical preparations. In our study, this new method was used to overcome the instability problem of ESP during high-performance liquid chromatographic analysis in the presence of acidic drugs such as NPX. The method was validated according to ICH, FDA and USP guidelines with respect to accuracy, precision, specificity, linearity, solution stability, robustness, sensitivity and system suitability. The method was developed by using an isocratic condition of mobile phase comprising buffer [tetrabutylammonium hydroxide (0.0077 M) and n-heptane sulfonic acid-Na salt (0.002 M), pH 7.6], acetonitrile and methanol in a 60 : 20 : 20 v/v/v ratio at a flow rate of 1.5 mL/min over a C-18 (Octadecyl-silica, 5 µm, 250 × 4.6 mm) column at ambient temperature. The recovery for both drugs was found to be >99% which demonstrated the accuracy of this method. Intra- and inter-day precision studies of the new method were less than the maximum allowable limit [% relative standard deviation (RSD) ?2.0 according to FDA]. The method showed linear response with a correlation coefficient (r(2)) value of 0.999 for both drugs. More importantly, ESP was quite stable in diluting solvent and mobile phase in the presence of NPX for >3 days. Therefore, it was found to be an accurate, reproducible, sensitive and highly stability-indicating method and can be successfully applied for routine analysis of simultaneous assay of NPX and ESP in pharmaceutical dosage forms. PMID:25182005

Kayesh, Ruhul; Sultan, Md Zakir

2015-05-01

77

Dual Wavelength RP-HPLC Method for Simultaneous Determination of Two Antispasmodic Drugs: An Application in Pharmaceutical and Human Serum  

PubMed Central

A reverse phase stability indicating HPLC method for simultaneous determination of two antispasmodic drugs in pharmaceutical parenteral dosage forms (injectable) and in serum has been developed and validated. Mobile phase ingredients consist of Acetonitrile?:?buffer?:?sulfuric acid 0.1?M (50?:?50?:?0.3 v/v/v), at flow rate 1.0?mL/min using a Hibar ?Bondapak ODS C18 column monitored at dual wavelength of 266?nm and 205?nm for phloroglucinol and trimethylphloroglucinol, respectively. The drugs were subjected to stress conditions of hydrolysis (oxidation, base, acid, and thermal degradation). Oxidation degraded the molecule drastically while there was not so much significant effect of other stress conditions. The calibration curve was linear with a correlation coefficient of 0.9999 and 0.9992 for PG and TMP, respectively. The drug recoveries fall in the range of 98.56% and 101.24% with 10?pg/mL and 33?pg/mL limit of detection and limit of quantification for both phloroglucinol and trimethylphloroglucinol. The method was validated in accordance with ICH guidelines and was applied successfully to quantify the amount of trimethylphloroglucinol and phloroglucinol in bulk, injectable form and physiological fluid. Forced degradation studies proved the stability indicating abilities of the method. PMID:24286017

Hasan, Najmul; Chaiharn, Mathurot; Khan, Sauleha; Khalid, Hira; Sher, Nawab; Siddiqui, Farhan Ahmed; Siddiqui, Muhammad Zain

2013-01-01

78

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. PMID:23641336

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

2013-01-01

79

Quantitative Determination of three Angiotensin-II-receptor Antagonists in Presence of Hydrochlorothiazide by RP-HPLC in their Tablet Preparations  

PubMed Central

Losartan potassium, Valsartan , Telmisartan and Irbesartan are angiotensin-II-receptor antagonists (ARA II) group which used in treatment of hypertension alone or in combination with other drugs mainly Hydrochlorothiazide. RP- HPLC method was developed for the assay of three angiotensin-II-receptor antagonists (ARA-IIs) in presence of Hydrochlorothiazide. The method was performed by reversed phase high performance liquid chromatography using a mobile phase which is consisted of 0.025 M potassium dihydrogen phosphate (pH 6.0): acetonitrile = 65:35% with detection at 220 nm on an ACE C18 column (250 mm × 4.6 mm, 5 ?m) at flow rate 1.5 mL/min in an isocratic manner. The proposed method was validated according to ICH guidline in terms of linearity, accuracy, precision , robustness, limit of detection and limit of quantitation. PMID:24523743

Hafez, Hany Mohammed; Elshanawane, Abdullah Ahmed; Abdelaziz, Lobna Mohammed; Kamal, Magda Mohammed

2013-01-01

80

Quantitative Determination of three Angiotensin-II-receptor Antagonists in Presence of Hydrochlorothiazide by RP-HPLC in their Tablet Preparations.  

PubMed

Losartan potassium, Valsartan , Telmisartan and Irbesartan are angiotensin-II-receptor antagonists (ARA II) group which used in treatment of hypertension alone or in combination with other drugs mainly Hydrochlorothiazide. RP- HPLC method was developed for the assay of three angiotensin-II-receptor antagonists (ARA-IIs) in presence of Hydrochlorothiazide. The method was performed by reversed phase high performance liquid chromatography using a mobile phase which is consisted of 0.025 M potassium dihydrogen phosphate (pH 6.0): acetonitrile = 65:35% with detection at 220 nm on an ACE C18 column (250 mm × 4.6 mm, 5 ?m) at flow rate 1.5 mL/min in an isocratic manner. The proposed method was validated according to ICH guidline in terms of linearity, accuracy, precision , robustness, limit of detection and limit of quantitation. PMID:24523743

Hafez, Hany Mohammed; Elshanawane, Abdullah Ahmed; Abdelaziz, Lobna Mohammed; Kamal, Magda Mohammed

2013-01-01

81

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. PMID:23641334

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

2013-01-01

82

Optimization of Forced Degradation Using Experimental Design and Development of a Stability-Indicating Liquid Chromatographic Assay Method for Rebamipide in Bulk and Tablet Dosage Form  

PubMed Central

A novel stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of rebamipide in bulk and tablet dosage form. Rebamipide (drug and drug product) solutions were exposed to acid and alkali hydrolysis, thermal stress, oxidation by hydrogen peroxide and photodegradation. Experimental design has been used during forced degradation to determine significant factors responsible for degradation and to obtain optimal degradation conditions. In addition, acid and alkali hydrolysis was performed using a microwave oven. The chromatographic method employed the HiQ sil C-18HS (250 × 4.6 mm; 5 ?m) column with mobile phase consisting of 0.02 M potassium phosphate (pH adjusted to 6.8) and methanol (40:60, v/v) and the detection was performed at 230 nm. The procedure was validated for specificity, linearity, accuracy, precision and robustness. There was no interference observed of excipients and degradation products in the determination of the active pharmaceutical ingredient. The method showed good accuracy and precision (intra and inter day) and the response was linear in a range from 0.5 to 5 ?g mL?1. The method was found to be simple and fast with less trial and error experimentation by making use of experimental design. Also, it proved that microwave energy can be used to expedite hydrolysis of rebamipide. PMID:21617774

Sonawane, Sandeep; Gide, Paraag

2011-01-01

83

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

2010-10-29

84

Simultaneous determination of 15 phenolic compounds and caffeine in teas and mate using RP-HPLC/UV detection: method development and optimization of extraction process.  

PubMed

A reversed-phase high performance liquid chromatographic coupled to ultraviolet detection (RP-HPLC/UV) method was developed for simultaneous determination of 15 phenolic compounds and caffeine in TEAS (green tea, oolong tea, black tea and mate). Furthermore, the extraction process of total phenolic contents (TPC) from TEAS were optimized using response surface methodology (RSM) based on a central composite design (CCD) and then applied to extraction of TEAS. The best conditions obtained using the model were as follow: green tea--extraction time of 123 min, extraction temperature of 70 °C and ethanol concentration of 75%, oolong tea--extraction time of 98 min, extraction temperature of 70 °C and ethanol concentration of 69%, black tea--extraction time of 105 min, extraction temperature of 71 °C and ethanol concentration of 63%, and mate--extraction time of 103 min, extraction temperature of 71 °C and ethanol concentration of 61%. Among the extraction methods used in this study, heat-reflux extraction was found to result in the highest values of TPC. The chromatographic peaks of the 16 studied compounds were successfully identified by comparing their retention time and UV spectra with the reference standards. Method validation was performed by means of linearity, sensitivity, selectivity, accuracy and precision. The developed method was found to be simple, specific and reliable and is suited for routine analysis of phenolic compounds and caffeine in TEAS. PMID:25442580

Bae, In Kyung; Ham, Hyeon Mi; Jeong, Min Hee; Kim, Dong Ho; Kim, Ho Jin

2015-04-01

85

Method development and validation for simultaneous determination of lumefantrine and its major metabolite, desbutyl lumefantrine in human plasma using RP-HPLC/UV detection.  

PubMed

A simple, specific, precise and rapid RP-HPLC-UV method was developed for simultaneous determination of lumefantrine and its metabolite desbutyl lumefantrine in human plasma. Experimental parameters were optimized and the method was validated according to standard guidelines. The method showed adequate separation for lumefantrine and desbutyl lumefantrine and best resolution was achieved with Supelco Discovery HS C18 RP (150mm×4.6mm, 5?m) column using acetonitrile and 0.05% trifluroacetic acid (70:30, v/v) as a mobile phase pumped at a flow rate of 1.0ml/min and wavelength of 335nm. The method was linear over the concentration range of 10-12,000ng/ml. The lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for lumefantrine were 10.0 and 18.0ng/ml, while for desbutyl lumefantrine were 7.5 and 15.0ng/ml, respectively. The proposed method was efficiently applied for determination of lumefantrine and desbutyl lumefantrine concentrations in plasma samples for pharmacokinetic studies. PMID:24316521

Khuda, Fazli; Iqbal, Zafar; Shah, Yasar; Ahmmad, Lateef; Nasir, Fazli; Khan, Amir Zada; Amanullah; Shahbaz, Naila

2014-01-01

86

Evaluation of a Propolis Water Extract Using a Reliable RP-HPLC Methodology and In Vitro and In Vivo Efficacy and Safety Characterisation  

PubMed Central

Since the beginning of propolis research, several groups have studied its antibacterial, antifungal, and antiviral properties. However, most of these studies have only employed propolis ethanolic extract (PEE) leading to little knowledge about the biological activities of propolis water extract (PWE). Based on this, in a previous study, we demonstrated the anti-inflammatory and immunomodulatory activities of PWE. In order to better understand the equilibrium between effectiveness and toxicity, which is essential for a new medicine, the characteristics of PWE were analyzed. We developed and validated an RP-HPLC method to chemically characterize PWE and PEE and evaluated the in vitro antioxidant/antimicrobial activity for both extracts and the safety of PWE via determining genotoxic potential using in vitro and in vivo mammalian micronucleus assays. We have concluded that the proposed analytical methodology was reliable, and both extracts showed similar chemical composition. The extracts presented antioxidant and antimicrobial effects, while PWE demonstrated higher antioxidant activity and more efficacious for the most of the microorganisms tested than PEE. Finally, PWE was shown to be safe using micronucleus assays. PMID:23710228

Rocha, Bruno Alves; Bueno, Paula Carolina Pires; Vaz, Mirela Mara de Oliveira Lima Leite; Nascimento, Andresa Piacezzi; Ferreira, Nathália Ursoli; Moreno, Gabriela de Padua; Rodrigues, Marina Rezende; Costa-Machado, Ana Rita de Mello; Barizon, Edna Aparecida; Campos, Jacqueline Costa Lima; de Oliveira, Pollyanna Francielli; Acésio, Nathália de Oliveira; Martins, Sabrina de Paula Lima; Tavares, Denise Crispim; Berretta, Andresa Aparecida

2013-01-01

87

Effects of extraction methods on phenolic contents and antioxidant activity in aerial parts of Potentilla atrosanguinea Lodd. and quantification of its phenolic constituents by RP-HPLC.  

PubMed

The effects of different solvent systems (methanol, ethanol, acetone, and their 50% aqueous concentrations) and extraction procedures (microwave, ultrasound, Soxhlet and maceration) on the antioxidant activity of aerial parts of Potentilla atrosanguinea were investigated by three different bioassays: 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays and ferric reducing antioxidant potential (FRAP). The 50% aqueous ethanol extracts exhibited strong antioxidant activity measured in terms of Trolox equivalent antioxidant capacity (TEAC) [(54.34 to 122.96, 29.82 to 101.22 and 13.64 to 41.43) mg of Trolox/g] with ABTS (*+), DPPH (*) and FRAP assays, respectively. In general, TEAC of Soxhlet extracts was found to be 1.8 and 3 times higher than ultrasound and maceration but slightly (1.2 times) higher than microwave. A positive correlation (r(2) = 0.931 to 0.982) was observed between total polyphenol (TPC) and total flavonoid (TFC) contents which ranged between 26.7 to 30.7 mg/g gallic acid equivalent and 16.8 to 20.8 mg/g quercetin equivalent respectively, with antioxidant activity. In addition, some of its bioactive phenolic constituents which contribute largely toward antioxidant potential such as chlorogenic acid, catechin, caffeic acid, p-coumaric acid and quercetin were also quantified in different extracts by RP-HPLC. PMID:18841977

Kalia, Kalpana; Sharma, Kapil; Singh, Harsh Pratap; Singh, Bikram

2008-11-12

88

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

89

RP-HPLC method with fluorescence detection for determination of small quantities of triamcinolone in plasma in presence of endogenous steroids after derivatization with 9-anthroyl nitrile; pharmacokinetic studies  

Microsoft Academic Search

A new indirect RP-HPLC method was developed for determination of small, ng\\/ml, concentrations of triamcinolone (TMC) in human plasma, in presence of endogenous corticosteroids: cortisol (hydrocortisone, F), cortisone (E) and their metabolites, after administration of TMC in a free alcohol form. After solid phase extraction (SPE) in cartridges with octadecyl phase, TMC and prednisolone (I.S.) were derivatized by treatment with

Franciszek K. G?ówka; Marta Kara?niewicz; Ewelina Lipnicka

2006-01-01

90

Simultaneous Quantitative Determination of 12 Active Components in Yuanhu Zhitong Prescription by RP-HPLC Coupled with Photodiode Array Detection  

PubMed Central

Background: Yuanhu Zhitong prescription (YZP) is a famous traditional Chinese medicine formula, which is officially recorded in Chinese Pharmacopoeia for the treatment of stomach pain, hypochondriac pain, headache and dysmenorrhea caused by qi-stagnancy and blood stasis. It is the first report for the simultaneous determination of 12 active components in YZP. Objective: A newly, simple, accurate and reliable method for the separation and determination of 12 active components (protopine, ?-allocryptopine, coptisine, xanthotol, palmatine, dehydrocorydaline, glaucine, tetrahydropalmatine, tetrahydroberberine, imperatorin, corydaline, isoimperatorin) in YZP was developed and validated using HPLC-PAD. Materials and Methods: The analytes were performed on a Phenomenex Luna-C18 (2) column (250×4.6 mm, 5.0 ?m) with a gradient elution program using a mixture of acetonitrile and 0.1% phosphoric acid water solution (adjusted with triethylamine to pH 5.6) as mobile phase. Analytes were performed at 30°C with a flow rate of 1.0 mL/min. Results: The validated method was applied to analyze four major dosage forms of YZP coming from different manufacturers with good linearity (r2, 0.9981~0.9999), precision (RSD, 0.24~2.89%), repeatability (RSD, 0.15~3.34%), stability (RSD, 0.14~3.35%), recovery (91.13~110.81%) of the 12 components. Conclusion: The proposed method enables the separation and determination of 12 active components in a single run for the quality control of YZP. PMID:25709212

Zhang, Xiaokai; Zhang, Song; Yang, Qian; Cao, Wei; Xie, Yanhua; Qiu, Pengcheng; Wang, Siwang

2015-01-01

91

A simple validated RP-HPLC bioanalytical method for the quantitative determination of a novel valproic acid arylamide derivative in rat hepatic microsomes.  

PubMed

A simple and specific bioanalytical method based on reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with ultraviolet detection was developed and validated for the determination of a novel valproic acid arylamide, N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) in rat hepatic microsomes (a subcellular fraction containing phase I enzymes, especially cytochrome P450). The chromatographic separation was achieved using a reversed-phase Zorbax SB-C18 column and a mobile phase of acetic acid in water (0.2% v/v) and acetonitrile (40:60?v/v) with a flow rate of 0.5?mL/min. The calibration curve was linear over the range of 882-7060?ng/mL (r(2) ?=?0.9987), and the lower limit of quantification and the lower limit of determination were found to be 882 and 127.99?ng/mL, respectively. The method was validated with excellent sensitivity, and intra-day accuracy and precision varied from 93.79 to 93.12%, and from 2.12 to 4.36%, respectively. The inter-day accuracy and precision ranged from 93.29 to 97.30% and from 0.68 to 3.60%, respectively. The recovery of HO-AAVPA was measured between 91.36 and 97.98%. The assay was successfully applied to the analysis of kinetic metabolism and pharmacokinetic parameters in vitro by a substrate depletion approach. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25137440

Silva-Trujillo, Arianna; Correa-Basurto, José; Romero-Castro, Aurelio; Albores, Arnulfo; Mendieta-Wejebe, Jessica Elena

2015-04-01

92

A developed and validated stability-indicating reverse-phase high performance liquid chromatographic method for determination of cefdinir in the presence of its degradation products as per International Conference on Harmonization guidelines  

PubMed Central

The present article deals with the development and validation of a stability-indicating, reverse-phase high performance liquid chromatographic (RP-HPLC) method, for the determination of cefdinir on a Waters RP Spherisorb C-18 column (250 mm × 4.6 mm, 5 ?m). A mobile phase consisting of water (pH adjusted to 3.0 with orthophosphoric acid) : acetonitrile : methanol 13:5:2 (v/v/v) was used. The flow rate was 1 mL min-1. The separation was performed at room temperature. Detection was carried out at 286 nm, using a PDA detector. The developed method was statistically validated for the linearity, accuracy, specificity, Limit of Detection (LOD), and Limit of Quantitation (LOQ). The specificity of the method was ascertained by forced degradation studies, by acid and alkali degradation, oxidation, photolysis, and heat degradation. The degraded products were well-separated from the analyte, with significant differences in their retention time values. The Beer Law was obeyed over a concentration range of 0.05 – 15.00 ?g mL-1 and the correlation coefficient was 0.999. PMID:23781424

Hamrapurkar, Purnima; Patil, Priti; Phale, Mitesh; Gandhi, Mital; Pawar, Sandeep

2011-01-01

93

Sensitivity of stability indices to dealerting  

SciTech Connect

It is reported that more than 100 former or current heads of state and civilian leaders from around the world, including ex-presidents Jimmy Carter and Mikhail Gorbachev, have signed a statement that calls for removing nuclear weapons from alert status and other measures aimed at the eventual elimination of atomic arsenals--reflecting mounting support for the cause of nuclear bolition. This note uses stability analysis derived from current US and Russian analyses to study the impact of such dealerting on stability, indicating that it could be negative. Dealerting forces removes them from first and second strikes for as long as they are dealerted. If they are dealerted for periods long compared to those involved in the evaluation of first strike stability, dealerting has the same effect as permanent arms reductions, it subtracts them from first and second strikes. Thus, it is conceptually a way of implementing such reductions on an accelerated scale. Dealerting strategic forces has been posited as a stabilizing step towards their abolition. Previous reports have shown that planned START reductions will reduce stability indices by about a factor of two. Dealerting would hasten those reductions. They would also raise the possibility that one side could realert faster than the other. If so, the remobilized forces could be used to damage limit, which would reduce his first strike cost and stability index. The impact of complete demobilization of SSBNs would be an order of magnitude reduction in the overall stability index, to a level set by alert ICBMs. Generally, it would be preferable to maintain any existing strategic forces at the highest level of alert to minimize this effect and to concentrate instead on decreasing their total number.

Canavan, G.H.

1998-03-01

94

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

95

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

96

Development and validation of a novel stability-indicating HPLC method for the quantitative determination of eleven related substances in ezetimibe drug substance and drug product.  

PubMed

Ezetimibe is a novel lipid-lowering agent that inhibits intestinal absorption of dietary and biliary cholesterol. In the present work, a simple, sensitive and reproducible gradient reverse phase high performance liquid chromatographic (RP-HPLC) method for separation and determination of the related substances of ezetimibe was developed and validated. Eleven potential process-related impurities (starting materials, (3S,4S,3'S)-isomer, degradants and byproducts) were identified in the crude samples. Tentative structures for all the impurities were assigned primarily based on comparison of their retention time and mass spectrometric data with that of available standards and references. This method can be applied to routine analysis in quality control of both bulk drugs and commercial tablets. Separation of all these compounds was performed on a Phenomenex Luna Phenyl-Hexyl (100mm×4.6mm, 5?m) analytical column. The mobile phase-A consists of acetonitrile-water (pH adjusted to 4.0 with phosphoric acid)-methanol at 15:75:10 (v/v/v), and mobile phase-B contains acetonitrile. The eluted compounds were monitored at 210nm. Ezetimibe was subjected to hydrolytic, acid, base, oxidative, photolytic and thermal stress conditions as per ICH serves to generate degradation products that can be used as a worst case to assess the analytical method performance. The drug showed extensive degradation in thermal, acid, oxidative, base and hydrolytic stress conditions, while it was stable to photolytic degradation conditions. The main degradation product formed under thermal, acid, oxidative, base and hydrolytic stress conditions corresponding to (2R,3R,6S)-N, 6-bis(4-fluorophenyl)-2-(4-hydroxyphenyl)-oxane-3-carboxamide (Ezetimibe tetrahydropyran impurity) was characterized by LC-MS/MS analysis. The degradation products were well resolved from the main peak and its impurities, thus proved the stability-indicating power of the method. The developed method was validated as per international conference on harmonization (ICH) guidelines with respect to specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision and robustness. PMID:25882410

Luo, Zhiqiang; Deng, Zhongqing; Liu, Yang; Wang, Guopeng; Yang, Wenning; Hou, Chengbo; Tang, Minming; Yang, Ruirui; Zhou, Huaming

2015-07-01

97

Unique variability of tocopherol composition in various seed oils recovered from by-products of apple industry: rapid and simple determination of all four homologues (?, ?, ? and ?) by RP-HPLC/FLD.  

PubMed

The tocochromanol profile was studied in seed oils recovered from by-products of fruit industry, five dessert and seven crab apple varieties grown in Eastern Europe (Latvia). The seed oils obtained from dessert apples were characterized by higher contents of tocopherols (191.05-379.08 mg/100g oil) when compared to seed oils recovered from crab apples (130.55-202.54 mg/100g oil). The predominant homologues of tocopherol in all the studied samples were ? and ? over ? and ?. However, seed oils recovered from the apple cultivars 'Antej' and 'Beforest' had a unique profile of four tocopherol homologues (?:?:?:?) 91.41:80.55:72.46:79.03 and 114.55:112.84:78.69:73.00 mg/100g oil, respectively. A single dilution of seed oils in 2-propanol facilitated the direct use samples in the DPPH assay as well as injection into the RP-HPLC system containing a PFP (pentafluorophenyl) column, which resulted in a rapid separation of all four tocopherol homologues with excellent repeatability and reproducibility. PMID:25442533

Górna?, Pawe?

2015-04-01

98

Identification and quantification of soluble free, soluble conjugated, and insoluble bound phenolic acids in durum wheat (Triticum turgidum L. var. durum) and derived products by RP-HPLC on a semimicro separation scale.  

PubMed

A straightforward semimicro separation scale RP-HPLC method was developed for the identification and quantification of phenolic acids (PAs) occurring as soluble free, soluble conjugated, and insoluble bound compounds, which were independently extracted from wholemeal of durum wheat and from its derived products coarse bran, semolina, and dried pasta. A narrow bore column and a semimicro photodiode array detector (PDA) cell, in conjunction with a single quadrupole mass spectrometer, equipped with an electrospray ionization source (ESI-MS), were employed. The method was validated in terms of linearity of calibration graphs, limits of detection, limits of quantification, repeatability, and accuracy, which was evaluated by a recovery study. In each sample (wholemeal, coarse bran, semolina, and dried pasta), the total amounts of the three different forms of PAs were in the order bound > conjugated > free, with bound PAs accounting for 61.0-83.6% of the total PAs. Ferulic acid was the most abundant PA in both soluble free and insoluble bound forms, whereas sinapic acid predominated in the conjugated ones. The highest PA content, calculated as the sum of total PAs quantified in the three forms, was found in coarse bran, followed by wholemeal, semolina, and dried pasta. PMID:24175612

Nicoletti, Isabella; Martini, Daniela; De Rossi, Antonella; Taddei, Federica; D'Egidio, Maria Grazia; Corradini, Danilo

2013-12-01

99

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.  

PubMed

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. As gentamicin has a weak UV chromophore, it is not possible to detect low levels of known and unknown related substances of gentamicin using a UV detector. In this method, a Charged Aerosol Detector (CAD) was used to obtain high sensitivity that was necessary for the intended purpose of the method. This method can separate all the analogues of gentamicin including all known and unknown related substances of the API. A short (5cmx4.6mm) pentafluorophenyl HPLC column from Restek (Allure PFP) was used with an ion-pair gradient mobile phase consisting of (A) heptafluorobutyric acid:water:acetonitrile (0.025:95:5, v/v/v) and (B) trifluoroacetic acid:water:acetonitrile (1:95:5, v/v/v). PMID:19815362

Joseph, Arul; Rustum, Abu

2010-02-01

100

Development of New Method for Simultaneous Analysis of Piracetam and Levetiracetam in Pharmaceuticals and Biological Fluids: Application in Stability Studies  

PubMed Central

RP-HPLC ultraviolet detection simultaneous quantification of piracetam and levetiracetam has been developed and validated. The chromatography was obtained on a Nucleosil C18 column of 25?cm × 0.46?cm, 10??m, dimension. The mobile phase was a (70?:?30?v/v) mixture of 0.1?g/L of triethylamine and acetonitrile. Smooth flow of mobile phase at 1?mL/min was set and 205?nm wavelength was selected. Results were evaluated through statistical parameters which qualify the method reproducibility and selectivity for the quantification of piracetam, levetiracetam, and their impurities hence proving stability-indicating properties. The proposed method is significantly important, permitting the separation of the main constituent piracetam from levetiracetam. Linear behavior was observed between 20?ng/mL and 10000?ng/mL for both drugs. The proposed method was checked in bulk drugs, dosage formulations, physiological condition, and clinical investigations and excellent outcome was witnessed. PMID:25114921

Siddiqui, Farhan Ahmed; Sher, Nawab; Shafi, Nighat; Wafa Sial, Alisha; Ahmad, Mansoor; Mehjebeen

2014-01-01

101

[Unilateral triangular lumbopelvic stabilization: indications and techniques].  

PubMed

Operative fixation has become treatment of choice for unstable sacral fractures. Osteosynthesis for these fractures results in loss of reduction in up to 15%. Vertical sacral fractures involving the S1 facet joint (Isler 2 and 3) may lead to multidirectional instability. Multidirectional instability of the posterior pelvic ring and lumbopelvic junction may be stabilized and forces balanced by a so-called lumbopelvic triangular fixation. Lumbopelvic triangular fixation combines vertical fixation between the lumbar vertebral pedicle and the ilium, with horizontal fixation, as an iliosacral screw or a transiliacal plate osteosynthesis. The iliac screw is directed from the posterior superior iliac spine (PSIS) to the anterior inferior iliac spine (AIIS). Thereby, lumbopelvic fixation decreases the load to the sacrum and SI joint and transfers axial loads from the lumbar spine directly onto the ilium. Triangular lumbopelvic fixation allows early full weight bearing and therefore reduces prolonged immobilization. The placement of iliac screws may be a complex surgical procedure. Thus, the technique requires thorough surgical preparation and operative logistics. Wound-related complications may occur. Preexisting Morell-Lavalée lesions increase the risk for infection. Prominent implants cause local irritation and pain. Hardware prominence and pain are markedly reduced with screw head recession into the PSIS. PMID:24233083

Hoffmann, M F; Dudda, M; Schildhauer, T A

2013-11-01

102

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

PubMed

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. PMID:23337200

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

2013-01-01

103

Determination of Rottlerin, a Natural Protein Kinases C Inhibitor, in Pancreatic Cancer Cells and Mouse Xenografts by RP-HPLC Method  

PubMed Central

Rottlerin is a natural polyphenolic ketone isolated from the pericarps of Mallotus phillippinensis. In previous studies we showed that parenteral administration of rottlerin reduced tumor growth in murine xenograft models of pancreatic cancer. The aim of this study was to develop a simple and validated method for the quantitative determination of rottlerin in plasma and tumor tissues of mice fed a rottlerin diet. A xenograft model of pancreatic cancer was prepared by injection of 2×106 HPAF-II cells subcutaneously into nude mice. One week before tumor implantation, mice were randomly allocated to standard diet (AIN76A) and standard diet supplement with 0.012% rottlerin (n=6 per group). Mice were sacrificed after 6 weeks on diets. Rottlerin was extracted from the plasma and tissues using protein precipitation-extraction and analyzed by reverse-phase HPLC-DAD method. The same HPLC method was also applied to determine rottlerin levels in conditioned culture media and in cell lysates from HPAF-II cells exposed to 25 µM concentration of rottlerin. A substantial amount of rottlerin was detected in tumor (2.11 ± 0.25 nmol/g tissue) and plasma (2.88 ± 0.41 µM) in mice fed rottlerin diet. In addition, significant levels of rottlerin (57.4 ± 5.4 nmol/mg protein) were detected in cell lysates from rottlerin-treated HPAF-II cells. These data indicate that rottlerin is efficiently absorbed in cells and tissues both in vivo and in vitro and suggest a strong potential for rottlerin as a preventive or adjuvant supplement for pancreatic cancer. PMID:24482742

Lu, Qing-Yi; Zhang, Lifeng; Lugea, Aurelia; Moro, Aune; Edderkaoui, Mouad; Eibl, Guido; Pandol, Stephen J.; Go, Vay-Liang W

2014-01-01

104

Stability indicating HPTLC method for the estimation of estradiol  

Microsoft Academic Search

Estradiol (ESD) is widely used in post climacteric replacement therapy. Most of the methods used for quantitation are expensive and time consuming. A rapid, selective and precise stability indicating high performance thin layer chromatography method was developed and validated for the estimation of ESD in bulk and pharmaceutical dosage forms. The method employed TLC aluminium plate precoated with silica gel

P. N. Kotiyan; P. R. Vavia

2000-01-01

105

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

2009-12-01

106

Stabilization of a recombinant human epidermal growth factor parenteral formulation through freeze-drying.  

PubMed

Development studies were performed to design a pharmaceutical composition that allows the stabilization of a parenteral rhEGF formulation in a lyophilized dosage form. Unannealed and annealed drying protocols were tested for excipients screening. Freeze-dry microscopy was used as criterion for excipients and formulation selection; as well as to define freeze-drying parameters. Excipients screening were evaluated through their effect on freeze-drying recovery and dried product stability at 50 °C by using a comprehensive set of analytical techniques assessing the chemical stability, protein conformation and bioactivity. The highest stability of rhEGF during freeze-drying was achieved by the addition of sucrose or trehalose. After storing the dried product at 50 °C, the highest stability was achieved by the addition of dextran, sucrose, trehalose or raffinose. The selected formulation mixture of sucrose and dextran could prevent protein degradation during the freeze-drying and delivery processes. The degradation rate assessed by RP-HPLC could decrease 100 times at 37 °C and 70 times at 50 °C in dried with respect to aqueous formulation. These results indicate that the freeze-dried formulation represents an appropriate technical solution for stabilizing rhEGF. PMID:25190208

Santana, Héctor; Sotolongo, Jorge; González, Yaima; Hernández, Gerardo; Chinea, Glay; Gerónimo, Haydée; Amarantes, Odalys; Beldarraín, Alejandro; Páez, Rolando

2014-11-01

107

Degradation Study on Sulfasalazine and a Validated HPLC-UV Method for its Stability Testing  

PubMed Central

Sulfasalazine (SSZ) was subjected to degradation under the conditions of hydrolysis (acid, alkali, and water), oxidation (30% H2O2), dry heat, and photolysis (UV-VIS light) in accordance with the ICH guidelines. An RP-HPLC method was developed to study the degradation behavior. No degradation was noted under any condition except alkaline hydrolysis where SSZ was degraded to a single minor product. SSZ was optimally resolved from this product on an XTerra® RP18 column with a mobile phase composed of methanol and an ammonium acetate buffer (10 mM, pH 7.0) (48:52, v/v) delivered at a rate of 0.8 mL/min in an isocratic mode. The method was validated and found to be linear (r2=0.99945), precise (%RSD <2), robust, and accurate (94–102%) in the concentration range of 0.5–50 ?g/mL of SSZ. The PDA analysis of the degraded sample revealed the SSZ peak purity to be 998.99 and the drug peak eluted with a resolution factor of >2 from the nearest resolving peak, indicating the method to be selectively stability-indicating for the drug analysis. The method was applied successfully for the stability testing of the commercially available SSZ tablets that were under varied ICH-prescribed conditions. An explanation for the unusual stability of the drug when exposed to acidic hydrolysis, despite the presence of the sulfonamide linkage, is also discussed. PMID:24959403

Saini, Balraj; Bansal, Gulshan

2014-01-01

108

Degradation Study on Sulfasalazine and a Validated HPLC-UV Method for its Stability Testing.  

PubMed

Sulfasalazine (SSZ) was subjected to degradation under the conditions of hydrolysis (acid, alkali, and water), oxidation (30% H2O2), dry heat, and photolysis (UV-VIS light) in accordance with the ICH guidelines. An RP-HPLC method was developed to study the degradation behavior. No degradation was noted under any condition except alkaline hydrolysis where SSZ was degraded to a single minor product. SSZ was optimally resolved from this product on an XTerra(®) RP18 column with a mobile phase composed of methanol and an ammonium acetate buffer (10 mM, pH 7.0) (48:52, v/v) delivered at a rate of 0.8 mL/min in an isocratic mode. The method was validated and found to be linear (r(2)=0.99945), precise (%RSD <2), robust, and accurate (94-102%) in the concentration range of 0.5-50 ?g/mL of SSZ. The PDA analysis of the degraded sample revealed the SSZ peak purity to be 998.99 and the drug peak eluted with a resolution factor of >2 from the nearest resolving peak, indicating the method to be selectively stability-indicating for the drug analysis. The method was applied successfully for the stability testing of the commercially available SSZ tablets that were under varied ICH-prescribed conditions. An explanation for the unusual stability of the drug when exposed to acidic hydrolysis, despite the presence of the sulfonamide linkage, is also discussed. PMID:24959403

Saini, Balraj; Bansal, Gulshan

2014-06-01

109

Stability-Indicating HPLC Determination of Gemcitabine in Pharmaceutical Formulations  

PubMed Central

A simple, sensitive, inexpensive, and rapid stability indicating high performance liquid chromatographic method has been developed for determination of gemcitabine in injectable dosage forms using theophylline as internal standard. Chromatographic separation was achieved on a Phenomenex Luna C-18 column (250?mm × 4.6?mm; 5?) with a mobile phase consisting of 90% water and 10% acetonitrile (pH 7.00 ± 0.05). The signals of gemcitabine and theophylline were recorded at 275?nm. Calibration curves were linear in the concentration range of 0.5–50??g/mL. The correlation coefficient was 0.999 or higher. The limit of detection and limit of quantitation were 0.1498 and 0.4541??g/mL, respectively. The inter- and intraday precision were less than 2%. Accuracy of the method ranged from 100.2% to 100.4%. Stability studies indicate that the drug was stable to sunlight and UV light. The drug gives 6 different hydrolytic products under alkaline stress and 3 in acidic condition. Aqueous and oxidative stress conditions also degrade the drug. Degradation was higher in the alkaline condition compared to other stress conditions. The robustness of the methods was evaluated using design of experiments. Validation reveals that the proposed method is specific, accurate, precise, reliable, robust, reproducible, and suitable for the quantitative analysis.

Singh, Rahul; Shakya, Ashok K.; Naik, Rajashri; Shalan, Naeem

2015-01-01

110

Indicators of dynamic stability in transtibial prosthesis users  

Microsoft Academic Search

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

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

2010-01-01

111

Stabilities of neutral and basic esters of bendamustine in plasma compared to the parent compound: kinetic investigations by HPLC.  

PubMed

Esters of the cytostatic bendamustine (1), previously demonstrated to be much more potent than the parent compound as antiproliferative agents in vitro, were investigated for stability in buffer and plasma, as well as against porcine liver esterase in the presence of different amounts of albumin using a validated RP-HPLC method with fluorescence detection. The hydrolysis of the nitrogen mustard moiety was retarded (for 1: approximately 130 vs. 11 min) in the presence of plasma proteins. For the derivatives, both cleavage of ester and nitrogen mustard moieties were analyzed. Enzymatic hydrolysis was very fast in the case of 2-pyrrolidino-, 2-piperidino- and 2-(4-methylpiperazino)-ethyl esters, whereas methyl, ethyl, morpholinoethyl and branched 2-pyrrolidinoethyl esters were considerably more stable (half-lives between 41 and 116 min, compared to <5 min). Inhibition by physostigmine indicated unspecific cholinesterases to be involved in the rapid ester cleavage. Due to lower protein content and higher enzymatic activity in murine compared to human plasma, reduced stability of all investigated esters in mouse plasma (t½<2 min) has to be taken into account with respect to the design of animal studies. PMID:25499654

Huber, S; Antoni, F; Schickaneder, C; Schickaneder, H; Bernhardt, G; Buschauer, A

2015-02-01

112

Herring gull eggs indicate stabilizing Great Lakes PCB concentrations  

SciTech Connect

The author evaluated the fit of 3 alternative models to herring gull (Larus argentatus) egg PCB concentration data from 1978--1992 to examine whether PCB levels were decreasing or had ceased to decline. The best fit models indicate that, following initial declines, no discernible PCB decreases are occurring in 4 of the 5 lakes. Only Lake Erie indicates a continued PCB decline, though the Erie data may be too noisy to differentiate model fits. These results are consistent with previous analyses indicating stable PCB concentrations in Lake Michigan fishes and suggest that further improvements may be too slow to be of practical importance from a management perspective.

Stow, C. [Univ. of Wisconsin, Madison, WI (United States). Center for Limnology

1995-12-31

113

Stability of a biaxial indicator gyrostabilizer with rotation of a three-degree-of-freedom gyroscope  

Microsoft Academic Search

The Liapunov method is used to study the stability of a biaxial indicator gyrostabilizer with rotation of a three-degree-of-freedom gyroscope in the case of inequality of coefficients in the stabilization channels. The stability conditions obtained can be extended to the operation of a gyrostabilizer without rotation of the gyroscopes.

I. M. Okon

1978-01-01

114

The Stability of School Effectiveness Indices across Years.  

ERIC Educational Resources Information Center

School effectiveness indices (SEIs) based on residuals from regressing test performance in reading and mathematics onto prior-year test performance and a socioeconomic status measure (percentage eligible for a subsidized lunch program) were obtained for two consecutive years for 431 South Carolina elementary schools. The analysis involved school…

Mandeville, Garrett K.

115

Geometrical analysis of the LiCN vibrational dynamics: a stability geometrical indicator.  

PubMed

The vibrational dynamics of the LiNC/LiCN molecular system is examined making use of the Riemannian geometry. Stability and chaoticity are analyzed, in this context, by means of the Jacobi-Levi-Civita equations, derived from the Jacobi metric, and its solutions. A dynamical indicator, called stability geometrical indicator, is introduced in order to ascertain the dynamical characteristics of stability and chaos in the molecule under study. PMID:25353539

Vergel, A; Benito, R M; Losada, J C; Borondo, F

2014-02-01

116

Stability-indicating chromatographic methods for the determination of sertindole.  

PubMed

In this work, two chromatographic methods have been developed and validated for the determination of sertindole (an antipsychotic agent) in the presence of its oxidative degradation product. Sertindole was subjected to stress stability studies, including acid, alkali, oxidative, photolytic and thermal degradation. The chromatographic methods included the use of thin-layer chromatography (TLC-densitometry) and high-performance liquid chromatography (HPLC). The TLC method employed aluminum TLC plates precoated with silica gel G.F254 as the stationary phase and methanol-ethyl acetate-33% ammonia (1:9:0.1, by volume) as the mobile phase, and the chromatograms were scanned at 227 nm. The developed HPLC method used a reversed-phase C18 column with isocratic elution. The mobile phase was composed of phosphate buffer pH 3.0-acetonitrile-triethylamine (45:55:0.03, by volume) and run at a flow rate of 1.0 mL/min. Quantitation was achieved with ultraviolet detection at 256 nm. The linearity ranges were found to be 2-14 µg/band and 5-200 µg/mL for TLC and HPLC, respectively. The developed methods were validated according to the International Conference on Harmonization guidelines and were applied for bulk powder and dosage forms. PMID:23733912

El-Ragehy, Nariman A; Hassan, Nagiba Y; Abdelkawy, Mohamed; Tantawy, Mahmoud A

2014-07-01

117

Trifluoroethanol-containing RP-HPLC mobile phases for the separation of transmembrane peptides human glycophorin-A, integrin alpha-1, and p24: analysis and prevention of potential side reactions due to formic acid.  

PubMed

Reversed-phase high-pressure liquid chromatography analysis and purification of three hydrophobic, aggregation-prone peptides, composed mainly of the transmembrane (TM) sequence, were performed using elution systems containing 2,2,2-trifluoroethanol (TFE). The addition of 10-16% TFE to a common mobile phase, such as a water/acetonitrile/propanol (PrOH) or a water/PrOH/formic acid system, markedly improved the chromatographic separation of these peptides. The superior performance of TFE-containing systems in separating peptides over water/PrOH/formic acid systems [Bollhagen R. et al., J. Chromatogr. A, 1995; 711: 181-186.] clearly demonstrated that adding TFE to the mobile phase is one of best methods for TM-peptide purification. Characterization of the potential side reactions using MALDI and ESI-LIT/Orbitrap mass spectrometry indicated that prolonged incubation of peptides in a mixture of TFE-formic acid possibly induces O-formylation of the Ser residue and N-formylation of the N-terminus of peptides. The conditions for selective removal of the formyl groups from TM peptides were also screened. We believe that these results will expand our ability to analyze and prepare hydrophobic, aggregation-prone TM peptides and proteins. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd. PMID:25504594

Hara, Toshiaki; Huang, Yue; Ito, Akihiro; Kawakami, Toru; Hojo, Hironobu; Murata, Michio

2015-02-01

118

Stability and Variability: Indicators for Passive Stability and Active Control in a Rhythmic Task  

E-print Network

University Nijmegen, Nijmegen, The Netherlands; and 3 Departments of Kinesiology and Integrative Biosciences It is widely recognized that stability is a core requirement for many motor tasks. Despite external are inherently stable, others inherently unstable. Upright posture when viewed as an inverted pendulum

Sternad, Dagmar

119

Optimal Placement of Unified Power Flow Controllers to Improve Dynamic Voltage Stability Using Power System Variable Based Voltage Stability Indices  

PubMed Central

This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs) in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs) including the line stability index (LQP), the voltage collapse proximity indicator (VCPI), and the line stability index (Lmn) are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD) software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO) and differential evolution (DE), which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches. PMID:25874560

Albatsh, Fadi M.; Ahmad, Shameem; Mekhilef, Saad; Mokhlis, Hazlie; Hassan, M. A.

2015-01-01

120

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 ...

121

Subtle alternating electrocardiographic morphology as an indicator of decreased cardiac electrical stability  

NASA Technical Reports Server (NTRS)

Observations from finite-element computer models, together with analytic developments based on percolation theory have suggested that subtle fluctuations of ECG morphology might serve as an indicator diminished cardiac electrical stability. With fixed-rate atrial pacing in canines, we have previously observed a pattern of alternation in T wave energy which correlated with cardiac electrical stability. We report here on a series of 20 canine experiments in which cardiac electrical stability (measured via Ventricular Fibrillation Threshold determination) was compared to a non-degenerate, multidimensional measurement of the degree of alternating activity present in the ECG complex morphology. The decrease in cardiac electrical stability brought on by both coronary artery occlusion and systemic hypothermia was consistently accompanied by subtle alternation in ECG morphology, with the absolute degree of alternating activity being significantly (negatively) correlated with cardiac electrical stability.

Smith, J. M.; Blue, B.; Clancy, E.; Valeri, C. R.; Cohen, R. J.

1985-01-01

122

Stress degradation studies on betahistine and development of a validated stability-indicating assay method  

Microsoft Academic Search

The purpose of this work was to study the stability of betahistine (BET) at different stress conditions and to develop a sensitive stability-indicating high-performance liquid chromatographic (HPLC) assay method. The stress conditions applied were including the effect of heat, moisture, acid–base, and ultra-violet (UV) light. Betahistine and its decomposition products were derivatized by reaction with dansyl chloride (Dan-Cl) and analyzed

Alaa Khedr; Mahmoud Sheha

2008-01-01

123

Aggregate stability as an indicator of soil erodibility and soil physical quality: review and perspectives  

NASA Astrophysics Data System (ADS)

Aggregate breakdown due to water and rain action may cause surface crusting, slumping, a reduction of infiltration and interrill erosion. Aggregate stability determines the capacity of aggregates to resist the effects of water and rainfall. In this paper, we evaluated and reviewed the relevance of an aggregate stability measurement to characterize soil physical properties as well as to analyse the processes involved in these properties. Stability measurement assesses the sensitivity of soil aggregates to various basic disaggregation mechanisms such as slaking, differential swelling, dispersion and mechanical breakdown. It has been showed that aggregate size distributions of structural stability tests matched the size distributions of eroded aggregates under rainfall simulations and that erosion amount was well predicted using aggregate stability indexes. It means stability tests could be used to estimate both the erodibility and the size fractions that are available for crust formation and erosion processes. Several studies showed that organic matter was one of the main soil properties affecting soil stability. However, it has also been showed that aggregate stability of a given soil could vary within a year or between years. The factors controlling such changes have still to be specified. Aggregate stability appears therefore as a complex property, depending both on permanent soil characteristics and on dynamic factors such as the crusting stage, the climate and the biological activity. Despite, and may be, because of this complexity, aggregate stability seems an integrative and powerful indicator of soil physical quality. Future research efforts should look at the causes of short-term changes of structural stability, in order to fully understand all its aspects.

Le Bissonnais, Yves; Chenu, Claire; Darboux, Frédéric; Duval, Odile; Legout, Cédric; Leguédois, Sophie; Gumiere, Silvio

2010-05-01

124

Stability evaluation of tramadol enantiomers using a chiral stability-indicating capillary electrophoresis method and its application to pharmaceutical analysis.  

PubMed

In this study, a chiral stability-indicating CE assay was developed for the stability evaluation of tramadol (TR) enantiomers in commercial tablets using maltodextrin as chiral selector. To investigate the stability-indicating power of the analytical method as well as stability evaluation of TR enantiomers, active pharmaceutical ingredient and TR tablets were subjected to photolysis, heat, oxidation and hydrolysis to conduct stress testing. Best separation for the TR enantiomers was achieved on an uncoated fused-silica capillary at 20 °C using borate buffer (50 mM, pH 10.2) containing 10% m/v maltodextrin. All determinations were performed by a UV detector at 214 nm. A constant voltage of 20 kV was applied to obtain the separation. The range of quantitation for both enantiomers was 5-100 ?g/mL (R>0.996). Intra- and inter-day RSD (n=6) were less than 10%. The percent relevant errors were obtained to be less than 4.0 for both enantiomers. The limits of quantitation and detection for both enantiomers were 5 and 1.5 ?g/mL, respectively. Degradation products resulting from the stress studies were the same for both enantiomers and did not interfere with the detection of the enantiomers. PMID:21626694

Mohammadi, Ali; Nojavan, Saeed; Rouini, Mohammadreza; Fakhari, Ali Reza

2011-07-01

125

The Effect of Ankle Taping and Balance Exercises on Postural Stability Indices in Healthy Women  

PubMed Central

[Purpose] The purpose of this study was to compare the effect of ankle taping and balance exercises on postural stability indices in healthy women. [Subjects and Methods] Thirty healthy female students were randomly assigned into two equal groups: ankle taping and balance exercise. The balance exercise group performed balance exercises for 6 weeks, with 3 sessions per week and each session lasting 40 minutes. Ankle joint taping was performed for 6 weeks and was renewed three times a week. Before and after the interventions, overall, anteroposterior, and mediolateral stability indices were measured with a Biodex Balance System in bilateral and unilateral stance positions with the eyes open and closed. [Results] In the taping group during bilateral standing with the eyes closed, the overall stability index changed from 6±1.4 to 4.8±1.3, anteroposterior stability index changed from 4.2±1.27 to 3.4±0.97, and mediolateral stability index changed from 3.2±0.75 to 2.7± 0.7. In the balance exercise group during bilateral standing with the eyes closed, the overall stability index changed from 5.7±1.69 to 4.5±1.94, anteroposterior stability index changed from 4.1±1.61 to 3±1.21, and mediolateral stability index changed from 3.5±1.4 to 2.2± 1.3. No significant difference was seen between the two groups regarding any study variables. [Conclusion] The results showed that compared with the taping technique, balance training increases postural stability in the majority of the studied balance situations. PMID:24926148

Akbari, Asghar; Sarmadi, Alireza; Zafardanesh, Parisa

2014-01-01

126

High-performance liquid chromatographic stability-indicating assay for naphazoline and tetrahydrozoline in ophthalmic preparations.  

PubMed

A high-performance liquid chromatographic (HPLC) analysis for tetrahydrozoline and naphazoline in ophthalmic solutions is presented. The analysis allows a more reproducible, direct stability-indicating assay than the colorimetric methods generally employed. The HPLC system is so designed that a variety of ophthalmic solutions containing either naphazoline or tetrahydrozoline can be analyzed concomitantly. PMID:6644602

Bauer, J; Krogh, S

1983-11-01

127

SPECTROPHOTOMETRIC AND STABILITY INDICATING HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF NORTRIPTYLINE HYDROCHLORIDE AND FLUPHENAZINE HYDROCHLORIDE  

Microsoft Academic Search

Spectrophotometric and high performance liquid chromatographic procedures are described for determination of nortriptyline hydrochloride and fluphenazine hydrochloride. The first procedure is based on application of first derivative of ratio spectra (DD) for quantitative determination of nortriptyline hydrochloride in presence of fluphenazine hydrochloride. Secondly, an accurate, sensitive and stability indicating method has been introduced for determination of nortriptyline hydrochloride and fluphenazine

Nariman A. El-Ragehy; Samah S. Abbas; Sonia Z. El-Khateeb

2002-01-01

128

Comparison of aerobic and anaerobic stability indices through a MSW biological treatment process  

Microsoft Academic Search

A complex mechanical–biological waste treatment plant designed for the processing of mixed municipal solid wastes (MSW) and source-selected organic fraction of municipal solid wastes (OFMSW) has been studied by using stability indices related to aerobic (respiration index, RI) and anaerobic conditions (biochemical methane potential, BMP). Several selected stages of the plant have been characterized: waste inputs, mechanically treated wastes, anaerobically

Sergio Ponsá; Teresa Gea; Llorenç Alerm; Javier Cerezo; Antoni Sánchez

2008-01-01

129

System of indicators for acid-base titration in surfactant-stabilized emulsions  

Microsoft Academic Search

The pT values of some acid-base indicators in surfactant-stabilized emulsions are found. Multiple linear regression equations are proposed to predict the protolytic properties of sulfophthalein reagents in emulsions based on various types of surfactants. The conditions are found for the alkalimetric determination of naproxen and ketoprofen with the end-point detection using thymol blue.

A. M. Shevchenko; S. A. Kulichenko

2005-01-01

130

Respiration and enzymatic activities as indicators of stabilization of sewage sludge composting.  

PubMed

The objective of this work was to study the evolution of physico-chemical and microbial parameters in the composting process of sewage sludge (SS) with pruning wastes (PW) in order to compare these parameters with respect to their applicability in the evaluation of organic matter (OM) stabilization. To evaluate the composting process and organic matter stability, different microbial activities were compared during composting of anaerobically digested SS with two volumetric ratios, 1:1 and 3:1 of PW:SS and two aeration techniques including aerated static piles (ASP) and turned windrows (TW). Dehydrogenase activity, fluorescein diacetate hydrolysis, and specific oxygen uptake rate (SOUR) were used as microbial activity indices. These indices were compared with traditional parameters, including temperature, pH, moisture content, organic matter, and C/N ratio. The results showed that the TW method and 3:1 (PW:SS) proportion was superior to the ASP method and 1:1 proportion, since the former accelerate the composting process by catalyzing the OM stabilization. Enzymatic activities and SOUR, which reflect microbial activity, correlated well with temperature fluctuations. Based on these results it appears that SOUR and the enzymatic activities are useful parameters to monitor the stabilization of SS compost. PMID:25728091

Nikaeen, Mahnaz; Nafez, Amir Hossein; Bina, Bijan; Nabavi, BiBi Fatemeh; Hassanzadeh, Akbar

2015-05-01

131

A Validated, Specific Stability-Indicating RP-LC Method for Moxifloxacin and Its Related Substances  

Microsoft Academic Search

A validated, specific, stability-indicating reversed-phase liquid chromatographic method has been developed for quantitative\\u000a analysis of moxifloxacin and its related substances in bulk samples and pharmaceutical dosage forms in the presence of degradation\\u000a products and process-related impurities. Forced degradation studies were performed on bulk samples of moxifloxacin, in accordance\\u000a with ICH guidelines, using acidic, basic, and oxidizing conditions, and thermal and

M. Lalitha Devi; K. B. Chandrasekhar

2009-01-01

132

A Validated Stability Indicating HPTLC Method for Determination of Cephalexin in Bulk and Pharmaceutical Formulation  

Microsoft Academic Search

A simple, specific, precise and stability-indicating high performance thin layer chromatographic method of analysis of Cephalexin, both as a bulk drug and in formulation was developed and validated. The method employed TLC (Thin Layer Chromatography) aluminum plates pre-coated with silica gel 60 F 254 as the stationary phase. The solvent system consisted of Ethyl Acetate : Methanol : Ammonia (6:4:1,

R. M. Jeswani; P. K. Sinha; M. C. Damle

133

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

134

Stability-indicating methods for determination of vincamine in presence of its degradation product  

Microsoft Academic Search

Three different stability indicating assay methods are developed and validated for determination of vincamine in the presence of its degradation product (vincaminic acid). The first method is based on the derivative ratio zero crossing spectrophotometric technique using 0.1N hydrochloric acid as a solvent. In the second method, measurements are based on spectro-densitometric technique using high performance thin-layer chromatography (HPTLC) plates

Mostafa A. M. Shehata; Mohammad A. El Sayed; Mohammad F. El Tarras; Mohammad G. El Bardicy

2005-01-01

135

Development and Validation of a Stability?Indicating HPTLC?Densitometric Method for Satranidazole  

Microsoft Academic Search

A sensitive, selective, precise, and stability?indicating high performance thin layer chromatography (HPTLC) method for analysis of satranidazole 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 toluene\\/acetonitrile (60:40, v\\/v). Densitometric analysis of satranidazole was carried out in

M. B. Patel; K. M. Patel; G. S. Patel; B. N. Suhagia; A. M. Prajapati

2007-01-01

136

Evaluation of degradation kinetics for abamectin in formulations using a stability indicating method.  

PubMed

The aim of this study was to evaluate stability characteristics and kinetics behavior of abamectin (ABM) as a 1 % (m/V) topical veterinary solution. During the study, samples stressed at 55 and 70 °C were regularly analyzed for several parameters over 8 weeks on a chromatographic (HPLC) system, using a Prodigy C18, 250 x 4.6 mm, 5-?m, column eluting with 15 : 34 : 51 (V/V/V) water/methanol/ acetonitrile as mobile phase. The HPLC method was validated for precision, accuracy, linearity and specificity, and was found to be stability indicating. The results showed that degradation of ABM followed first-order kinetics and data on loss in kobs (s-1) and half life (t1/2, days) demonstrated ABM showing the maximum stability in glycerol formal. The degradation behavior of ABM varies from solvent to solvent. The effect of added alkali on pH change and loss of ABM was studied and found to be unique for all solvents and very distinct from typical hydrolysis degradation. The present study may serve as a platform to design and develop topical non-aqueous solutions of ABM for veterinary use given no such comprehensive efforts have been published to date on the stability profile of ABM in non-aqueous solvents. PMID:23482313

Awasthi, Atul; Razzak, Majid; Al-Kassas, Raida; Harvey, Joanne; Garg, Sanjay

2013-03-01

137

Stability-indicating LC method for the simultaneous determination of lisinopril and hydrochlorothiazide.  

PubMed

A simple and rapid stability-indicating liquid chromatographic method was developed and validated for the simultaneous determination of lisinopril and hydrochlorotiazide (HCTZ) in drug substances and dosage forms in the presence of degradation products. Forced degradation studies were conducted on the pure drugs under hydrolytic, oxidative, thermal and photolytic conditions. A chromatographic separation of the two drugs and its degradation products was achieved with an RP-18 column, using methanol, acetonitrile and phosphate buffer (pH 7.1; 0.05 M) (15:15:70, v/v/v) as mobile phase at a flow rate of 0.8 mL min(-1) and UV detection at 210 nm. Lisinopril and HCTZ were well resolved from its degradation products showing the stability-indicating capability of the method. The described method was linear over a range of 40-200 µg mL(-1) for lisinopril and 25-175 µg mL(-1) for HCTZ. The assay was also selective, accurate and precise for lisinopril and HCTZ determination. This method represents an alternative to the United States Pharmacopeia (USP) method showing shorter retention time. The method was successfully applied for determination of lisinopril and HCTZ in combined commercial tablets. The results showed that the proposed method was found to be suitable for quantitative determination and the stability study of lisinopril and HCTZ in pharmaceutical samples. PMID:24297524

de Diego, Marta; Soto, Jorge; Mennickent, Sigrid

2014-01-01

138

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

139

Stability-Indicating HPTLC Method for the Determination of Tamsulosin in Pharmaceutical Dosage Forms  

Microsoft Academic Search

A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method was developed\\u000a for the determination of tamsulosin (TAM) in bulk and tablet formulation. Validation was carried out in compliance with International\\u000a Conference on Harmonization guidelines. The method employed thin-layer chromatography aluminium plates pre-coated with silica\\u000a gel 60F254 as the stationary phase and the mobile phase consisted of acetonitrile\\/methanol\\/dichloromethane

Vishnu P. Choudhari; Anna Pratima Ganpat Nikalje

2009-01-01

140

Validated stability-indicating densitometric thin-layer chromatography: Application to stress degradation studies of minocycline  

Microsoft Academic Search

A simple, stability-indicating high-performance thin-layer liquid chromatographic (HPTLC) method for analysis of minocycline was developed and validated. The densitometric analysis was carried out at 345nm using methanol–acetonitrile–isopropyl alcohol–water (5:4:0.5:0.5, v\\/v\\/v\\/v) as mobile phase.The method employed TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase. To achieve good result, plates were sprayed with a 10% (w\\/v) solution of

Nilu Jain; Gaurav Kumar Jain; Farhan Jalees Ahmad; Roop Krishen Khar

2007-01-01

141

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

142

Performance Comparison of Voltage Stability Indices for Weak Bus Identification in Power Systems  

NASA Astrophysics Data System (ADS)

Voltage collapse event is identified as complex and localized in nature but its effect is extensive once occurred. The vital effect of voltage collapse would be the total system collapse or blackouts which would cost a large loss to utility companies. Eventually, on- line monitoring of power system stability has become an important factor for electric power utilities. The last utmost option to avert voltage collapse incident from occurring is by the implementation of under voltage load shedding scheme. The identification of location for load shedding is the main motivation of the study. The weakest bus in a power system is identified as the location for load shedding. This location is obtained using voltage stability index Ld. The performance and effectiveness of Ld index is compared with Fast Voltage Stability Index (FVSI) and Le Index. The results obtained indicate that Ld Index can be used to identify the weak bus in a power system and consequently for the placement of UVLS relays in a power system network.

Verayiah, R.; Mohamed, A.; Shareef, H.; Zainal Abidin, I. Hj

2013-06-01

143

Novel indication for posterior dynamic stabilization: Correction of disc tilt after lumbar total disc replacement  

PubMed Central

Background The increase in total disc replacement procedures performed over the last 5 years has increased the occurrence of patients presenting with postoperative iatrogenic deformity requiring revision surgery. Proposed salvage treatments include device retrieval followed by anterior lumbar interbody fusion or posterior fusion. We propose a novel approach for the correction of disc tilt after total disc replacement using a posterior dynamic stabilization system. Methods Pedicle screws can be inserted either in an open manner or percutaneously by standard techniques under fluoroscopy. The collapsed side is expanded, and the convex side is compressed. Universal spacers are placed bilaterally, with the spacer on the collapsed side being taller by 6 mm. Cords are threaded through the spacers and pulled into place with the tensioning instrument. Extra tension is applied to the convex side, and the wound is closed by standard techniques. Results Three patients presenting with tilted total disc replacement devices underwent corrective surgery with posterior dynamic stabilization. Radiographs confirmed correction of deformity in all cases. Conclusions/Level of Evidence This technical note presents a novel indication for posterior dynamic stabilization and describes its surgical application to the correction of disc tilt after total disc replacement. This is level V evidence.

Cheng, Wayne K.; Palmer, Daniel Kyle; Jadhav, Vikram

2011-01-01

144

PrimeSupplier Cross-Program Impact Analysis and Supplier Stability Indicator Simulation Model  

NASA Technical Reports Server (NTRS)

PrimeSupplier, a supplier cross-program and element-impact simulation model, with supplier solvency indicator (SSI), has been developed so that the shuttle program can see early indicators of supplier and product line stability, while identifying the various elements and/or programs that have a particular supplier or product designed into the system. The model calculates two categories of benchmarks to determine the SSI, with one category focusing on agency programmatic data and the other focusing on a supplier's financial liquidity. PrimeSupplier was developed to help NASA smoothly transition design, manufacturing, and repair operations from the Shuttle program to the Constellation program, without disruption in the industrial supply base.

Calluzzi, Michael

2009-01-01

145

Stability indicating HPLC-UV method for determination of dapoxetine HCl in pharmaceutical product.  

PubMed

A stability-indicating HPLC-UV method for the determination of dapoxetine hydrochloride in solution and pharmaceutical product was developed. The mobile phase was composed of acetonitrile and 0.2 M ammonium acetate buffer at 50 : 50 ratio. The chromatographic parameters, theoretical plates (N), tailing factor (T), capacity factor (k') and peak asymmetry factor (As) were calculated. Stress degradation studies, namely, acid, alkali, oxidation, heat and UV light, were performed. The analyte was eluted at 5.8 min using gradient system at a flow rate of 1.5 mL/min. The theoretical plates count was > 2000, tailing factor < 1.54, capacity factor > 5.38 and peak asymmetry factor was < 1.10. The method was linear from 1 to 40 microg/mL with a correlation coefficient of 0.9994. The intraday precision and accuracy values were 0.14-1.54% and 0.63-1.83%, respectively. On the other hand, the interday precision and accuracy results were 0.49-1.83% and 1.15-1.85%, respectively. The drug solution was stable at ambient room temperature (26 degrees C) for 48 h. Dapoxetine HCI was found susceptible to oxidation and degraded slightly under acid and alkali conditions but was stable under UV light and heat. No interference from tablet excipiets and degradation products was found. Hence, the method can be employed as a stability-indicating method for the determination of dapoxetine HCl in pharmaceutical products. PMID:25265818

Liew, Kai Bin; Peh, Kok Khiang

2014-01-01

146

Stability-Indicating HPLC Determination of Trandolapril in Bulk Drug and Pharmaceutical Dosage Forms  

PubMed Central

A rapid, simple, accurate, precise, economical, robust, and stability indicating reverse phase HPLC-PDA procedure has been developed and validated for the determination of trandolapril. The trandolapril was separated isocratically on Hypersil-Gold C18 column (250?mm × 4.6?mm, 5??m) with a mobile phase consisting of 50% acetonitrile and 50% water (containing 0.025% triethylamine, pH 3.0 ± 0.1), at 25 ± 2°C. Retention time of the drug was ~4.6?min. The eluted compounds were monitored and identified at 210?nm. The linearity of the method was excellent (r2 > 0.9999) over the concentration range of 1–24??g/mL; the limit of detection (LOD) and limit of quantitation (LOQ) were 0.0566??g/mL and 0.1715??g/mL, respectively. The overall precision was less than 2%. Mean recovery of trandolapril was more than 99%; no interference was found from the component present in the preparation. Stability studies indicate that the drug was stable to sunlight and UV light. The drug gives 6 different oxidative products on exposure to hydrogen peroxide. Slight degradation was observed in acidic condition. Degradation was higher in the alkaline condition compared to other conditions. The robustness of the method was studied using factorial design experiment. PMID:25802524

Al-Hawash, Leena A.; Shakya, Ashok K.; Saleem, Maher L.

2015-01-01

147

A Stability-Indicating High Performance Liquid Chromatographic Method for the Determination of Diacerein in Capsules  

PubMed Central

A stability-indicating HPLC method was developed and validated for the quantitative determination of diacerein in capsule dosage forms. An isocratic separation was achieved using a perfectsil target ODS-3, 250×4.6 mm i.d., 5 µm particle size columns with a flow rate of 1 ml/min and using a UV detector to monitor the eluate at 254 nm. The mobile phase consisted of phosphate buffer:acetonitrile (40:60, v/v) with pH 4.0 adjusted with phosphoric acid. The drug was subjected to oxidation, hydrolysis, photolysis and thermal degradation. Diacerein was found to degrade in acidic, basic, and oxidative stress and also under neutral condition. Complete separation of degraded products was achieved from the parent compound. All degradation products in an overall analytical run time of approximately 10 min with the parent compound diacerein eluting at approximately 4.9 min. The method was linear over the concentration range of 1-10 µg/ml (r2 = 0.9996) with a limit of detection and quantitation of 0.01 and 0.05 µg/ml respectively. The method has the requisite accuracy, selectivity, sensitivity, precision and robustness to assay diacerein in capsules. Degradation products resulting from the stress studies did not interfere with the detection of diacerein and the assay is thus stability-indicating. PMID:20177451

Rao, Janhavi; Chauhan, Kanchan; Mahadik, K. R.; Kadam, S. S.

2009-01-01

148

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. PMID:22007220

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

2011-01-01

149

A stability-indicating high performance liquid chromatographic method for the determination of diacerein in capsules.  

PubMed

A stability-indicating HPLC method was developed and validated for the quantitative determination of diacerein in capsule dosage forms. An isocratic separation was achieved using a perfectsil target ODS-3, 250x4.6 mm i.d., 5 microm particle size columns with a flow rate of 1 ml/min and using a UV detector to monitor the eluate at 254 nm. The mobile phase consisted of phosphate buffer:acetonitrile (40:60, v/v) with pH 4.0 adjusted with phosphoric acid. The drug was subjected to oxidation, hydrolysis, photolysis and thermal degradation. Diacerein was found to degrade in acidic, basic, and oxidative stress and also under neutral condition. Complete separation of degraded products was achieved from the parent compound. All degradation products in an overall analytical run time of approximately 10 min with the parent compound diacerein eluting at approximately 4.9 min. The method was linear over the concentration range of 1-10 microg/ml (r(2) = 0.9996) with a limit of detection and quantitation of 0.01 and 0.05 microg/ml respectively. The method has the requisite accuracy, selectivity, sensitivity, precision and robustness to assay diacerein in capsules. Degradation products resulting from the stress studies did not interfere with the detection of diacerein and the assay is thus stability-indicating. PMID:20177451

Rao, Janhavi; Chauhan, Kanchan; Mahadik, K R; Kadam, S S

2009-01-01

150

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

1999-06-01

151

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

152

Indication  

PubMed Central

Should the indications for therapies differ from one nation to the next? What are the reasons behind controversial therapeutic variations? What roles do cultural history and authoritarian conflict among clinicians play in the adoption of therapies? When I worked at a rural hospital in Kenya, a woman experiencing obstructed labor made me ponder many questions—but only after our emergency ended in the death of her newborn son. In recounting and learning from this episode, I listened to the disparate Kenyan voices of the patient, the hospital’s director, the consultant obstetrician, and to the even more controversial voices of evidence-based medicine. In reflecting on this process, I have learned at least 3 lessons—about the transmissibility of arrogance, the role of guests in other countries, and the nature of science. PMID:22230834

Pust, Ronald E.

2012-01-01

153

Stability-indicating LC method for the estimation of bendamustine hydrochloride and its related impurities.  

PubMed

A novel, simple, sensitive and stability-indicating high-performance liquid chromatography method was developed and validated for the quantification of impurities (process related and degradants) and the assay determination of Bendamustine hydrochloride. A chromatographic separation of Bendamustine and its impurities was achieved with an Inertsil ODS-2 analytical column, 250 × 4.6 mm, 5 µm, using gradient elution with mobile phase A consisting of a mixture of water and trifluoroacetic acid (1000:1, v/v) and mobile phase B consisting of acetonitrile. The instrumental settings included a flow rate of 1.0 mL/min, column temperature of 27°C and a detector wavelength of 233 nm, using a photodiode array detector. The tailing factor for Bendamustine was 1.10. Bendamustine hydrochloride was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions and the stressed samples were analyzed by the proposed method. Peak homogeneity data of Bendamustine were obtained by using a photodiode array detector in the stressed sample chromatograms, which demonstrated the specificity of the method for estimation in the presence of degradants. The developed method was validated for parameters such as precision, accuracy, linearity, limit of detection, limit of quantification, ruggedness and robustness. The stability tests were also performed on drug substances as per International Conference on Harmonization guidelines. PMID:23825351

Kasa, Srinivasulu; Raja Sekhar Reddy, M; Kadaboina, Raja Sekhar; Murki, Veerender; Mulukutla, Venkata Suryanarayana

2014-08-01

154

Development and validation of stability-indicating HPLC method for determination of cefpirome sulfate.  

PubMed

The stability-indicating LC assay method was developed and validated for quantitative determination of cefpirome sulfate (CPS) in the presence of degradation products formed during the forced degradation studies. An isocratic HPLC method was developed with Lichrospher RP-18 column, 5 ?m particle size, 125 mm x 4 mm column and 12 mM ammonium acetate-acetonitrile (90 : 10 v/v) as a mobile phase. The flow rate of the mobile phase was 1.0 mL/min. Detection wavelength was 270 nm and temperature was 30 degrees C. Cefpirome sulfate as other cephalosporins was subjected to stress conditions of degradation in aqueous solutions including hydrolysis, oxidation, photolysis and thermal degradation. The developed method was validated with regard to linearity, accuracy, precision, selectivity and robustness. The method was applied successfully for identification and determination of cefpirome sulfate in pharmaceuticals and during kinetic studies. PMID:25362801

Zalewski, Przemys?aw; Skibi?ski, Robert; Cielecka-Piontek, Judyta; Bednarek-Rajewska, Katarzyna

2014-01-01

155

Stability-indicating UPLC method for determining related substances and degradants in dronedarone.  

PubMed

A simple, sensitive and reproducible method was developed on ultra-performance liquid chromatography coupled with photodiode array detection for the quantitative determination of dronedarone hydrochloride (DRO) in drug substance and pharmaceutical dosage forms. The method is applicable for the quantification of related substances and assays of drug substances. Chromatographic separation was achieved on Acquity UPLC BEH C8 100 mm, 2.1 mm and 1.7 µm columns, using gradient elution within a short run time of 10.0 min. The eluted compounds were monitored at 288 nm, the flow rate was 0.5 mL/min and the column oven temperature was maintained at 40°C. The resolution of DRO and 11 impurities (potentials and by-products) was greater than 2.0 for all pairs of components. The high correlation coefficient value (>0.9995) indicates the clear correlations between the concentrations of investigated compound and their peak areas within the test ranges. The repeatability and intermediate precision, expressed by the relative standard deviation, were less than 2.5%. The accuracy and validity of the method were further ascertained by performing recovery studies via a spike method. The accuracy of the method, expressed as relative error, was satisfactory. No interference was observed from concomitant substances normally added to the tablets. DRO was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. DRO was found to degrade significantly in acid and base stress conditions and to remain stable in thermal, photolytic degradation, oxidative and hydrolytic conditions. The degradation products were well resolved from primary peak and its impurities, proving that the method is stability indicating. The developed method was validated as per International Conference on Harmonization guidelines with respect to specificity, limit of detection, limit of quantification, linearity, accuracy, precision, solution stability and robustness. This method is also suitable for the determination of DRO drug substance and pharmaceutical dosage forms. PMID:23863770

Pydimarry, Surya Prakash Rao; Cholleti, Vijay Kumar; Vangala, Ranga Reddy

2014-08-01

156

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. PMID:22947049

2012-01-01

157

The stability of adenosine deaminase and adenosine monophosphate (AMP) deaminase as potential spoilage indicators for postmortem ice stored shrimp  

E-print Network

THE STABILITY OF ADENOSINE DEAMINASE AND ADENOSINE MONOPHOSPHATE (AMP) DEAMINASE AS POTENTIAL SPOILAGE INDICATORS FOR POSTMORTEM ICE STORED SHRIMP A Thesis by WAI LUN CHEUK Submitted to the Graduate College of Texas A&M University in partial... fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1978 Major Subject: Food Science and Technology THE STABILITY OF ADENOSINE DEAMINASE AND ADENOSINE MONOPHOSPHATE (AMP) DEAMINASE AS POTENTIAL SPOILAGE INDICATORS FOR POSTMORTEM...

Cheuk, Wai Lun

1978-01-01

158

Validated stability-indicating HPLC-UV method for simultaneous determination of glipizide and four impurities.  

PubMed

A selective stability-indicating HPLC-UV method for simultaneous determination of glipizide and four impurities (DPs I-IV) formed under hydrolytic conditions was developed and validated. The drug and impurities were resolved on an XTerra C18 column (250 x 4.5 mm id) in a single gradient run using buffer (0.005 M KH2PO4; pH 3.0)-methanol (60 + 40, v/v; mobile phase A) and (20 + 80, v/v; mobile phase B) at a flow rate of 0.5 mL/min with 230 nm detection wavelength. The method was linear across concentration ranges of 0.2-100, 0.1-100, 0.5-100, 0.2-100, and 0.1-50 microg/mL for glipizide and DPs I-IV, respectively. The RSD for intraday and interday precision for the drug and impurities was < 1 and < 1.2%, respectively. Satisfactory recoveries (96.58-99.97%) of each of the three concentrations selected across the linearity range of each analyte were obtained, proving the method was sufficiently accurate. The LOD was 0.07, 0.05, 0.16, 0.08, and 0.05 microg/mL and the LOQ was 0.20, 0.14, 0.50, 0.23, and 0.14 microg/mL for the drug and DPs I-IV, respectively. Each peak was resolved with resolution of > 2 from the nearest peak. Insignificant changes in retention time (< 4%) and calculated amount (< 1.65%) of drug and each impurity upon small but deliberate changes in various chromatographic parameters were observed, suggesting the method was robust. The method was applied successfully to stability testing of glipizide tablets. PMID:21563686

Gupta, Sakshi; Bansal, Gulshan

2011-01-01

159

Tunable release of clavam from clavam stabilized gold nanoparticles - Design, characterization and antimicrobial study.  

PubMed

A facile one-step approach is developed to synthesize highly stable (up to 6months) gold nanoparticles (GNPs) using Clavam, pharmaceutical form of amoxicillin which contains a mixture of amoxicillin and potassium salt of clavulanic acid, at room temperature (25-30°C). The clavam stabilized GNPs are characterized using various techniques including UV-Visible, FT-IR spectrophotometry and transmission electron microscopy (TEM). Tunable release of clavam from clavam stabilized GNPs is demonstrated using intracellular concentrations of glutathione (GSH). The process is monitored using an UV-Vis spectroscopy and the amount of clavam released in terms of amoxicillin concentration is quantitatively estimated using reverse phase high performance liquid chromatographic (RP-HPLC) technique. In vitro study reveals that the clavam released from GNPs' surface was found to show a significant enhancement in antibacterial activity against Escherichia coli and the cause of enhancement is addressed. PMID:25686977

Manju, V; Dhandapani, P; Gurusamy Neelavannan, M; Maruthamuthu, S; Berchmans, S; Palaniappan, A

2015-04-01

160

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.

161

Spatial scale of similarity as an indicator of metacommunity stability in exploited marine systems.  

PubMed

The spatial scale of similarity among fish communities is characteristically large in temperate marine systems: connectivity is enhanced by high rates of dispersal during the larval/juvenile stages and the increased mobility of large-bodied fish. A larger spatial scale of similarity (low beta diversity) is advantageous in heavily exploited systems because locally depleted populations are more likely to be "rescued" by neighboring areas. We explored whether the spatial scale of similarity changed from 1970 to 2006 due to overfishing of dominant, large-bodied groundfish across a 300 000-km2 region of the Northwest Atlantic. Annually, similarities among communities decayed slowly with increasing geographic distance in this open system, but through time the decorrelation distance declined by 33%, concomitant with widespread reductions in biomass, body size, and community evenness. The decline in connectivity stemmed from an erosion of community similarity among local subregions separated by distances as small as 100 km. Larger fish, of the same species, contribute proportionally more viable offspring, so observed body size reductions will have affected maternal output. The cumulative effect of nonlinear maternal influences on egg/larval quality may have compromised the spatial scale of effective larval dispersal, which may account for the delayed recovery of certain member species. Our study adds strong support for using the spatial scale of similarity as an indicator of metacommunity stability both to understand the spatial impacts of exploitation and to refine how spatial structure is used in management plans. PMID:22471094

Shackell, Nancy L; Fisher, Jonathan A D; Frank, Kenneth T; Lawton, Peter

2012-01-01

162

Stability-indicating polarographic determination of acyclovir through chelation with nickel(II).  

PubMed

A simple and sensitive, stability-indicating polarographic method was developed for the determination of acyclovir (ACV) in raw materials and dosage forms. The proposed method relies on the chelation of ACV with nickel(II) in Britton Robinson buffer (pH 5) and measuring the resulting polarographic wave either in the direct current (DCt) or differential pulse (DPP) modes. The polarographic wave has been characterized as being catalytic reduction prewave. Different experimental parameters affecting the formation of the Ni-ACV chelate and its polarographic activity were studied and optimized. The current concentration relationship was found to be linear over the range of 0.8-8 and 1-8 microg/mL, with minimum detectabilities of 0.10 and 0.19 microg/mL using DPP and DCt modes, respectively. The method was used to investigate the kinetics of the acid-induced degradation of the drug. The apparent first-order rate constants and half-life times were calculated. PMID:19485200

Sheribah, Zeinab A; El-Brashy, Amina M; El-Gamal, Rania M

2009-01-01

163

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

164

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. PMID:24082344

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

2013-01-01

165

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. PMID:22131621

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

2011-01-01

166

Survey of Wastewater Indicators and Human Pathogen Genomes in Biosolids Produced by Class A and Class B Stabilization Treatments  

Microsoft Academic Search

Accurate modeling of the infectious aerosol risk associated with the land application of biosolids requires an in-depth knowledge of the magnitudes and changes in pathogen concentrations for a variety of class A and class B stabilization methods. The following survey used quantitative PCR (qPCR) and culture assays to detect environmentally resistant bacterial and viral pathogens and biosolid indicator organisms for

Emily Viau; Jordan Peccia

2009-01-01

167

Development and validation of stability indicating HPLC and HPTLC methods for determination of sulpiride and mebeverine hydrochloride in combination  

Microsoft Academic Search

Validated sensitive and highly selective stability indicating methods are adopted for simultaneous quantitative determination of sulpiride and mebeverine hydrochloride in presence of their reported impurities and hydrolytic degradates whether in pure forms or in pharmaceutical formulation.The first method is High Performance Liquid Chromatography, where the mixture of sulpiride and mebeverine hydrochloride together with the reported interferents plus metopimazine as internal

Ibrahim A. Naguib; Mohammed Abdelkawy

2010-01-01

168

Application of a validated stability-indicating densitometric thin-layer chromatographic method to stress degradation studies on moxifloxacin  

Microsoft Academic Search

A simple, sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic (HPTLC) method for densitometric determination of moxifloxacin both as a bulk drug and from pharmaceutical formulation was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of

Sanjay K. Motwani; Roop K. Khar; Farhan J. Ahmad; Shruti Chopra; K. Kohli; S. Talegaonkar

2007-01-01

169

STABILITY-INDICATING HPLC METHOD WITH FLUORESCENCE DETECTION FOR DETERMINATION OF METHOCARBAMOL IN TABLETS. APPLICATION TO THERAPEUTIC DRUG MONITORING  

Microsoft Academic Search

A simple and highly sensitive stability-indicating HPLC method was developed and validated for the determination of the muscle relaxant, methocarbamol (MTC) in presence of its degradation product, guaifenesin (GFS). The analyses were carried out on Nucleosil 100-5 phenyl column (4.6 × 250 mm, 5 µm particle size), using a mobile phase consisting of 0.02 M orthophosphoric acid\\/ acetonitrile mixture (80:20, v\\/v) of pH 5.0 at

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

2012-01-01

170

Survey of wastewater indicators and human pathogen genomes in biosolids produced by class a and class B stabilization treatments.  

PubMed

Accurate modeling of the infectious aerosol risk associated with the land application of biosolids requires an in-depth knowledge of the magnitudes and changes in pathogen concentrations for a variety of class A and class B stabilization methods. The following survey used quantitative PCR (qPCR) and culture assays to detect environmentally resistant bacterial and viral pathogens and biosolid indicator organisms for 36 biosolid grab samples. Biosolids were collected from 14 U.S. states and included 16 class B mesophilic anaerobic digestion (MAD) samples and 20 class A biosolid samples from temperature-phased anaerobic digestion (TPAD), MAD plus composting (COM), and MAD plus heat pelletization processes. The indicator concentrations of fecal coliforms and male-specific coliphages as well as pathogen genome concentrations for human adenovirus species, Legionella pneumophila, Staphylococcus aureus, and Clostridium difficile were significantly lower in the class A samples, and a multivariate analysis of variance ranked the stabilization processes from the lowest pathogen/indicator load to the highest as (i) class A COM, (ii) class A TPAD, and (iii) class B MAD. Human adenovirus genomes were found in 88% of the class B samples and 70 to 100% of the class A samples. L. pneumophila, S. aureus, and C. difficile genomes were detected at the qPCR assay detection limits in 19 to 50% of the class B and class A anaerobic digestion samples, while L. pneumophila was detected in 50% of the class A compost samples. When considering all the stabilization methods, both the fecal coliform and the male-specific coliphage concentrations show a significant linear correlation with the pathogen genome concentrations. This survey provides the necessary pathogen concentrations to add to biosolid aerosol risk and pathogen exposure analyses and clarifies the effectiveness of class A stabilization methods with the pathogen and indicator loads in biosolids. PMID:18997022

Viau, Emily; Peccia, Jordan

2009-01-01

171

QUANTITATIVE ANALYSIS OF ITRACONAZOLE IN BULK, MARKETED AND NANO FORMULATION BY VALIDATED, STABILITY INDICATING HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHY METHOD  

Microsoft Academic Search

A stability-indicating high-performance thin-layer chromatographic (HPTLC) method was developed and validated for quantifying Itraconazole (Itz) in bulk drug, marketed formulation and an in house formulation comprising of lipidic-nano particle incorporated into vaginal gel. Aluminium plates precoated with silica gel 60 F-254 were used for TLC with Toulene: Ethyl acetate: Ammonia (1:5:0.1 v\\/v) as a mobile phase. The densitometric analysis was carried

Mohd. Aamir Mirza; Sushama Talegaonkar; Zeenat Iqbal

2012-01-01

172

DEVELOPMENT AND VALIDATION OF TWO CHROMATOGRAPHIC STABILITY-INDICATING METHODS FOR DETERMINATION OF ROSUVASTATIN IN PURE FORM AND PHARMACEUTICAL PREPARATION  

Microsoft Academic Search

Two new, simple, sensitive and accurate stability-indication methods were developed for quantitative determination of rosuvastain in the presence of its degradation products in raw material. The first is a High-Performance Liquid Chromatography (HPLC) method in which separation was achieved on Phenomenex C18 column (250 mm, i.d. 4.6 mm, 5 µm) using acetonitrile: 0.5 % formic acid (50 + 50, v\\/v

Hasumati A. Raj; Sadhana J. Rajput; Jayant B. Dave; Chaggan N. Patel

173

Stability-indicating high performance thin layer chromatography determination of Paroxetine hydrochloride 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 Paroxetine hydrochloride both as a bulk drug and in formulations was developed and validated. The method employed TLC (Thin Layer Chromatography) aluminum precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of butanol:acetic acid:water (8:2:0.5, v\\/v\\/v). This system was found to

A. Venkatachalam; Vidya S. Chatterjee

2007-01-01

174

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

Microsoft Academic Search

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 216nm was used for direct evaluation of the chromatograms in

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

2011-01-01

175

Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles  

Microsoft Academic Search

A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted

Sanjay K. Motwani; Roop K. Khar; Farhan J. Ahmad; Shruti Chopra; K. Kohli; Sushma Talegaonkar; Zeenat Iqbal

2006-01-01

176

APPLICATION OF STABILITY INDICATING HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHIC METHOD FOR QUANTITATION OF PRAMIPEXOLE IN PHARMACEUTICAL DOSAGE FORM  

Microsoft Academic Search

A sensitive, selective, precise, and stability-indicating high performance thin layer chromatographic method was developed and validated for the determination of pramipexole both as a bulk drug and in formulation. The method uses aluminum plates precoated with silica gel 60F-254 as the stationary phase and solvent system ethyl acetate: toluene: methanol: ammonia 8:1.5:0.5:0.6, (v\\/v\\/v\\/v). This system gave compact spots for pramipexole

Shubhangi M. Pawar; Sunil R. Dhaneshwar

2011-01-01

177

SIMULTANEOUS DETERMINATION OF OMEPRAZOLE AND DOMPERIDONE IN CAPSULES AND IN VITRO DISSOLUTION STUDIES BY USING STABILITY INDICATING UPLC  

Microsoft Academic Search

A novel stability indicating UPLC method was developed and validated for the simultaneous determination of omeprazole and domperidone in capsules formulation. The analysis was performed on a waters Acquity UPLC system with an Acquity UPLC BEH C18 column (5 mm × 2.1 mm I.D., 1.7 µm). Isocratic elution with a mobile phase consisting of a mixture of phosphate buffer (pH 5.0, 0.05 M) and Acetonitrile in

P. Venkata Rao; Ch. K. Sanjeeva Reddy; M. Ravi Kumar; Dantu Durga Rao

2012-01-01

178

Amphiphile-induced vesiculation in aged hereditary spherocytosis erythrocytes indicates normal membrane stability properties under  

E-print Network

Amphiphile-induced vesiculation in aged hereditary spherocytosis erythrocytes indicates normal protein or ankyrin were incubated with amphiphiles (detergents) at sublytic concentrations (378C, 60 min erythrocytes (1%). Control and HS cells responded, however, similarly to amphiphile-treatment (non

Iglic, Ales

179

Comparative stability and growth requirements of S. aureus and faecal indicator bacteria in seawater.  

PubMed

The fate (stability, multiplication) of S. aureus, E. coli and E. faecalis was determined in three classes of recreational waters (seawater, estuarine, stream) supplemented with nutrients in the form of sewage and peptone. In the absence of sunlight (24 +/- 2 degrees C), all bacteria in all water samples did not multiply and were slowly (days) inactivated. When 50% sewage was added to all water samples, E. coli and E. faecalis multiplied but S. aureus did not. When peptone (0.05%, 0.5%) was the added nutrient, the three bacteria multiplied. In the presence of sunlight (15-27 degrees C), S. aureus was inactivated rapidly (hours) in all water samples. These results show that when their nutritional requirements are met, S. aureus, E. coli and E. faecalis can multiply in the high salinity conditions of seawater. However, under environmental conditions, sunlight is an effective natural bactericidal agent. PMID:17037149

Fujioka, R S; Unutoa, T M

2006-01-01

180

Age and thermal stability of particulate organic matter fractions indicate the presence of black carbon in soil  

NASA Astrophysics Data System (ADS)

Black carbon (BC) from incomplete combustion is abundant in many soils. The age of black carbon is often higher than that of typical soil organic carbon (SOC) owing to its higher recalcitrance against microbial decomposition compared to plant residues. Also fossil BC may contribute to the high age of SOC. At the same time, the oxidative thermal stability of BC is known to be higher than that of SOC due to its chemical and physical structure. For a meaningful application of radiocarbon as an indicator for soil carbon age and turnover, the relative contribution of BC needs to be known but BC is difficult to separate physically from soil. Here we analyze particulate organic carbon (POC) fractions from four different field sites in Europe for their thermal stability using oxidative differential scanning calorimetry (DSC) and for their radiocarbon signature. POC may be particularly sensitive to BC 'contamination' because it was gained using a combination of size and density separation. One of these sites is essentially free of measurable amounts of BC. Each of the four sites comprised between five and eight individual POC samples taken from different spots. The radiocarbon signature and the calculated POC mean residence time of samples from three out of four sites indicated the presence of very old carbon, resulting in mean residence times (MRT) of several hundreds and up to 3700 years. In contrast, MRT's of POC from the virtually BC-free site were between 50 and 100 years. Two indicators for thermal stability of the POC fractions, i) the amount of heat released at temperatures > 450 °C and ii) the amount of heat released at 500 °C (where the latter represents the peak temperature of charcoal isolated from one of the samples) correlated both significantly and non-linearly with the samples MRT, indicating that samples with high BC content are older. Hence we can conclude that for an individual site with increasing abundance of BC both the age and the thermal stability of POC fractions increase. However, only in the case of samples from one site thermal stability proved to be a reliable predictor for the generic presence of BC whereas for the other two BC containing sites the thermal signals were not significantly different to the site free of BC.

Leifeld, Jens; Heiling, Maria; Hajdas, Irka

2014-05-01

181

[The stability of biological indicators used for monitoring ethylene oxide gas sterilization].  

PubMed

It was found the correlation between the storage time of biological indicators and their usefulness for monitoring of gas sterilization with ethylene oxide (EO). Bacillus subtilis var niger ATTC 9372 was used as a test organism. Two kinds of investigations were done: observation of bacterial growing or lack of growing after 1 hour exposition of storage tests in EO (EO concentration- 750 mg/l, temperature +/- 50 degrees C, (humidity-40%) and examination of drop in number of spores on strip tests after storage time. The results show that sterilization efficacy may be monitored using such spore strip tests up to six months of storage. PMID:7777783

Jakimiak, B; Bielicka, A

1994-01-01

182

QUANTITATIVE ANALYSIS OF ITRACONAZOLE IN BULK, MARKETED, AND NANO FORMULATION BY VALIDATED, STABILITY INDICATING HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHY  

Microsoft Academic Search

A stability-indicating high-performance thin-layer chromatographic (HPTLC) method was developed and validated for quantifying Itraconazole (Itz) in bulk drug, marketed formulation, and an in-house formulation comprised of lipidic-nano particle incorporated into vaginal gel. Aluminum plates precoated with silica gel 60 F-254 were used for TLC with Toulene:Ethyl acetate:Ammonia (1:5:0.1 v\\/v) as a mobile phase. The densitometric analysis was carried out at 266 nm using

Mohd. Aamir Mirza; Sushama Talegaonkar

2012-01-01

183

Variation in sediment stability and relation to indicators of microbial abundance in the Okura Estuary, New Zealand  

NASA Astrophysics Data System (ADS)

Secretions of mucus by benthic microbes potentially bind estuarine intertidal sediment, thus affecting stability by raising the erosion threshold. Existing models for predicting onset of erosion—such as the Shields diagram—have been built from laboratory studies of abiotic sediments, hence their accuracy when applied to natural sediment may be limited. In this study, variability in critical shear velocity ( u*crit) of natural intertidal sediments is correlated with indicators of microbial abundance, and based on those correlations we develop a predictor for the erosion threshold of natural sediments. Sediment cores, collected over 9 months from four sites of contrasting grain size (77-185 ?m) in the Okura Estuary (Auckland, New Zealand), were eroded in a laboratory flume to determine u*crit. Critical shear velocity for initiation of motion ranged from a minimum of 0.52 cm s -1 at the coarse-grained site to a maximum of 1.45 cm s -1 at the fine-grained site, values of which are up to three times those measured for equivalent abiotic sediment. The increase in u*crit with decreasing grain size was correlated with indicators of microalgal biomass (pigment) and mucilage content (carbohydrate) in the surface 2 mm of sediment. Abiotic measures of ?crit (non-dimensional u*crit) were adjusted via a stability factor, which was expressed as a function of sediment pheopigment content to estimate the erosion threshold in natural sediments in a better way. This method takes into account the temporal variations in sediment stability that occur irrespective of grain size.

Lelieveld, S. D.; Pilditch, C. A.; Green, M. O.

2003-05-01

184

Simultaneous determination of aliskiren and hydrochlorothiazide from their pharmaceutical preparations using a validated stability-indicating MEKC method.  

PubMed

A stability-indicating MEKC method was developed and validated for the simultaneous determination of aliskiren (ALI) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations using ranitidine as an internal standard (IS). Optimal conditions for the separation of ALI, HCTZ and its major impurity chlorothiazide (CTZ), IS and degradation products were investigated. The method employed 47?mM Tris buffer and 47?mM anionic detergent SDS solution at pH 10.2 as the background electrolyte. MEKC method was performed on a fused-silica capillary (40?cm) at 28°C. Applied voltage was 26?kV (positive polarity) and photodiode array (PDA) detector was set at 217?nm. The method was validated in accordance with the ICH requirements. The method was linear over the concentration range of 5-100 and 60-1200??g/mL for HCTZ and ALI, respectively (r(2) >0.9997). The stability-indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using the PDA detection. Precision and accuracy evaluated by RSD were lower than 2%. The method proved to be robust by a fractional factorial design evaluation. The proposed MEKC method was successfully applied for the quantitative analysis of ALI and HCTZ both individually and in a combined dosage tablet formulation to support the quality control. PMID:21710580

Sangoi, Maximiliano S; Wrasse-Sangoi, Micheli; Oliveira, Paulo R; Rolim, Clarice M B; Steppe, Martin

2011-08-01

185

Stability indicating HPLC-UV method for detection of curcumin in Curcuma longa extract and emulsion formulation.  

PubMed

A stability-indicating HPLC-UV method for the determination of curcumin in Curcuma longa extract and emulsion was developed. The system suitability parameters, theoretical plates (N), tailing factor (T), capacity factor (K'), height equivalent of a theoretical plate (H) and resolution (Rs) were calculated. Stress degradation studies (acid, base, oxidation, heat and UV light) of curcumin were performed in emulsion. It was found that N>6500, T<1.1, K' was 2.68-3.75, HETP about 37 and Rs was 1.8. The method was linear from 2 to 200 ?g/mL with a correlation coefficient of 0.9998. The intra-day precision and accuracy for curcumin were ?0.87% and ?2.0%, while the inter-day precision and accuracy values were ?2.1% and ?-1.92. Curcumin degraded in emulsion under acid, alkali and UV light. In conclusion, the stability-indicating method could be employed to determine curcumin in bulk and emulsions. PMID:25306352

Syed, Haroon Khalid; Liew, Kai Bin; Loh, Gabriel Onn Kit; Peh, Kok Khiang

2015-03-01

186

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

PubMed

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 (r(2)=0.9995) for atenolol and 8-32 ?g/ml (r(2)=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. PMID:22707819

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

2011-07-01

187

A size exclusion-reversed phase two dimensional-liquid chromatography methodology for stability and small molecule related species in antibody drug conjugates.  

PubMed

Antibody drug conjugates (ADCs) are complex therapeutic agents combining the specific targeting properties of antibodies and highly potent cytotoxic small molecule drugs to selectively eliminate tumor cells while limiting the toxicity to normal healthy tissues. One unique critical quality attribute of ADCs is the content of unconjugated small molecule drug present from either incomplete conjugation or degradation of the ADC. In this work, size exclusion chromatography (SEC) was coupled with reversed-phase (RP) HPLC in an online 2-dimensional chromatography format for identification and quantitation of unconjugated small molecule drugs and related small molecule impurities in ADC samples directly without sample preparation. The SEC method in the 1st dimension not only separated the small molecule impurities from the intact ADC, but also provided information about the size variants (monomer, dimer, aggregates, etc.) of the ADC. The small molecule peak from the SEC was trapped and sent to a RP-HPLC in the 2nd dimension to further separate and quantify the different small molecule impurities present in the ADC sample. This SEC-RP 2D-LC method demonstrated excellent precision (%RSD<2.0), linearity (r(2)=0.9999), sensitivity (LOQ of 0.05?g/mL of free drug in ADC sample) and accuracy (95-105% recovery of spiked samples). The 2D-LC method was further utilized to study the stability of an ADC drug product at different temperatures and pHs. Both small molecule degradation products and aggregation of the conjugate were observed in the stability samples and the degradation pathways of the ADC were investigated. This 2D-LC method offers a powerful tool for ADC characterization and provides valuable information for conjugation and formulation development. PMID:25818558

Li, Yi; Gu, Christine; Gruenhagen, Jason; Zhang, Kelly; Yehl, Peter; Chetwyn, Nik P; Medley, Colin D

2015-05-01

188

A validated stability-indicating HPLC method for the simultaneous determination of pheniramine maleate and naphazoline hydrochloride in pharmaceutical formulations  

PubMed Central

Background A simple, rapid, and accurate stability-indicating reverse phase liquid chromatographic method was developed and validated for the simultaneous determination of pheniramine maleate and naphazoline hydrochloride in bulk drugs and pharmaceutical formulations. Results Optimum chromatographic separations among pheniramine maleate, naphazoline hydrochloride and stress-induced degradation products have been achieved within 10 minutes by using an Agilent zorbax eclipse XDB C18 column (150 mm?×?4.6 mm, 5 ?m) as the stationary phase with a mobile phase consisted of 10 mM phosphate buffer pH 2.8 containing 0.5% triethlamine and methanol (68:32, v/v) at a flow rate of 1 mL min-1. Detection was performed at 280 nm using a diode array detector. Theoretical plates for pheniramine maleate and naphazoline hydrochloride were calculated to be 6762 and 6475, respectively. The method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, robustness, specificity, limit of detection and quantitation. Regression analysis showed good correlations (R2?>?0.999) for pheniramine maleate in the concentration range of 150–1200 ?g mL-1 and naphazoline hydrochloride in 12.5-100 ?g mL-1. The method results in excellent separation of both the analytes and degradation products. The peak purity factor is ?980 for both analytes after all types of stress, indicating complete separation of both analyte peaks from the stress induced degradation products. Conclusions Overall, the proposed stability-indicating method was suitable for routine quality control and drug analysis of pheniramine maleate and naphazoline hydrochloride in pharmaceutical formulations. PMID:24485011

2014-01-01

189

The unique stability of the photon indices in "dipping" Z-source GX 340+0 throughout spectral states  

NASA Astrophysics Data System (ADS)

We present an analysis of the spectral and timing properties of X-ray radiation from accreting neutron star source GX340+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 Gamma_com1 and Gamma_{com2} of the Comptonized components are almost constant, Gamma_{com1} and Gamma_{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 GX340+0 is similar to that previously established in the atoll sources 4U1728-34, 4U1820-30 and GX3+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 Gamma_{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

190

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

191

Stability indicating HPTLC method for determination of terbutaline sulfate in bulk and from submicronized dry powder inhalers.  

PubMed

A stability-indicating high-performance thin-layer chromatographic (HPTLC) method has been developed for the determination of terbutaline sulfate (TBS) as a bulk drug and in pharmaceutical formulations (submicronized dry powder inhalers). The separation was achieved on TLC aluminum plates precoated with silica gel 60F-254 using chloroform-methanol (9.0:1.0 v/v) as mobile phase. The densitometric analysis was carried out at 366 nm wavelength. Compact spots appeared at R(f) = 0.34 +/- 0.02. For the proposed procedure, linearity (r(2) = 0.9956 +/- 0.0015), limit of quantification (28.35 ng spot(-1)), limit of detection (9.41 ng spot(-1)), recovery (97.06-99.56%), and precision (< or = 1.86) were found to be satisfactory. TBS was subjected to acid and alkali hydrolyses, oxidation and photodegradation treatments. The degraded products were well separated from the pure drug. Statistical analysis reveals that the developed method has potential for routine analysis and stability testing of terbutaline sulfate in pharmaceutical drug delivery systems. PMID:20410570

Faiyazuddin, Md; Ahmad, Sayeed; Iqbal, Zeenat; Talegaonkar, Sushma; Ahmad, Farhan Jalees; Bhatnagar, Aseem; Khar, Roop Krishen

2010-01-01

192

Simultaneous quantification of related substances of perindopril tert-butylamine using a novel stability indicating liquid chromatographic method.  

PubMed

A novel stability indicating gradient reverse-phased high-performance liquid chromatographic method has been developed for the quantification of impurities of perindopril tert-butylamine (PER) in pharmaceutical dosage form. Separation of the active substance and its known (Impurities B, C, D, E, F) and unknown impurities was achieved on a BDS Hypersil C18 column (250 mm × 4.6 mm, 5 µm), thermostated at 70°C, using a mobile phase comprised of aqueous solution of sodium 1-heptanesulfonate adjusted to pH 2 with perchloric acid and acetonitrile. The flow rate was maintained at 1.5 mL min(-1), injection volume of 20 µL was utilized and detection of analytes was performed at 215 nm. The developed method was validated in accordance with current ICH Guidelines for all suggested parameters, including forced degradation studies and proved to be linear, accurate, precise and suitable for the impurity testing of PER, being subsequently applied during on-going stability studies of a newly developed generic formulation. PMID:25616989

Szabó, Zoltán-István; Réti, Zenk?-Zsuzsánna; Gagyi, László; Kis, Erika Lilla; Sipos, Emese

2015-03-01

193

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. PMID:21356068

2011-01-01

194

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

PubMed

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 (R f 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 r (2)= 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 R f 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. PMID:24082694

Akhtar, Juber; Fareed, Sheeba; Aqil, Mohd

2013-07-01

195

Development and Validation of Stability-indicating HPLC Method for Betamethoasone Dipropionate and Related Substances in Topical Formulation.  

PubMed

A gradient reversed phase HPLC method was developed and validated for analysis of betamethasone dipropionate, its related substances and degradation products, using Altima C(18) column (250×4.6 mm, 5 ?m) with a flow rate of 1.0 ml/min and detection wavelength of 240 nm. The mobile phase A is a mixture of water, tetrahydrofuran and acetonitrile in the ratio of 90:4:6 (v/v/v) while mobile phase B is a mixture of acetonitrile, tetrahydrofuran, water and methanol in the ratio of 74:2:4:20 (v/v/v/v). The samples were analyzed using 20 ?l injection volume and the column temperature was maintained at 50°. The limit of detection and limit of quantitation were found to be 0.02 ?g/ml and 0.07 ?g/ml, respectively. The stability-indicating capability of method was established by forced degradation studies and method demonstrated successful separation of drug, its related substances and degradation products. The method was validated as per the International Conference on Harmonization guidelines. The developed method is linear in the range of 0.07 to 200% of specification limits established for all the known related substances; betamethasone17-propionate, betamethasone 21-propionate, betamethasone 17-propionate-21-acetate (RSD <5, 2, 1%, respectively, r(2)=09991-0.9999 for sample concentration of 100 ?g/ml). The method is sensitive, specific, linear, accurate, precise and stability indicating for the quantitation of drug, its related substances and other degradation compounds. PMID:23325990

Vairale, A S; Sivaswaroop, P; Bandana, S

2012-03-01

196

Regularities of Anthocyanins Retention in RP HPLC for “Water–Acetonitrile–Phosphoric Acid” Mobile Phases  

PubMed Central

The influence of exchange of HCOOH (System 2) by phosphoric acid (System 1) for acidification of the “acetonitrile–water” mobile phases for reversed-phase HPLC of anthocyanins was investigated in the framework of relative retention analysis. The differences and similarities of anthocyanins separation were revealed. It has been shown that some common features of the quantitative relationships may be used for preliminary anthocyanins structure differentiation, according to the number of OH-groups in anthocyanidin backbone as well as to a number of saccharide molecules in glycoside radicals in position 3 of the anthocyanin without MS detection. PMID:25692073

Deineka, V. I.; Deineka, L. A.; Saenko, I. I.

2015-01-01

197

Original article RP-HPLC analysis of furosine and acid-soluble  

E-print Network

(Symmetry 300TM, Waters), which enabled the separation of whey proteins within 22 min; furosine was analysed designated as ESL milk showed furosine contents protein as well as acid-soluble -Lg contents g-1 protein), levels comparable to the excessive heat load of UHT milk. Thus, there is an urgent

Boyer, Edmond

198

Erratum of "RP-HPLC analysis of furosine and acid-soluble -lactoglobulin  

E-print Network

of whey protein fractions soluble at pH 4.6 from different categories of heat-treated milk: raw milk (125, EDP Sciences, 2010 DOI: 10.1051/dst/2010014 Available online at: www.dairy-journal.org Article

Paris-Sud XI, Université de

199

Simultaneous estimation of metformin hydrochloride, pioglitazone hydrochloride, and glimepiride by RP-HPLC in tablet formulation.  

PubMed

A simple, precise, rapid, and reproducible reversed-phase high-performance liquid chromatography method is developed for the simultaneous estimation of metformin hydrochloride (MET), pioglitazone hydrochloride (PIO), and glimepiride (GLP) present in multicomponent dosage forms. Chromatography is carried out isocratically at 25 degrees C +/- 0.5 degrees C on an Inertsil-ODS-3 (C-18) Column (250 x 4.60 mm, 5 microm) with a mobile phase composed of methanol-phosphate buffer (pH 4.3) in the ratio of 75:25 v/v at a flow rate of 1 mL/min. Detection is carried out using a UV-PDA detector at 258 nm. Parameters such as linearity, precision, accuracy, recovery, specificity, and ruggedness are studied as reported in the International Conference on Harmonization guidelines. The retention times for MET, PIO, and GLP are 2.66 + 0.5 min, 7.12 + 0.5 min, and 10.17 + 0.5 min, respectively. The linearity range and percentage recoveries for MET, PIO, and GLP are 10-5000, 10-150, and 1-10 microg/mL and 100.4%, 100.06%, and 100.2%, respectively. The correlation coefficients for all components are close to 1. The relative standard deviations for three replicate measurements in three concentrations of samples in tablets are always less than 2%. PMID:18647470

Jain, Deepti; Jain, Surendra; Jain, Deepak; Amin, Maulik

2008-07-01

200

Regularities of Anthocyanins Retention in RP HPLC for "Water-Acetonitrile-Phosphoric Acid" Mobile Phases.  

PubMed

The influence of exchange of HCOOH (System 2) by phosphoric acid (System 1) for acidification of the "acetonitrile-water" mobile phases for reversed-phase HPLC of anthocyanins was investigated in the framework of relative retention analysis. The differences and similarities of anthocyanins separation were revealed. It has been shown that some common features of the quantitative relationships may be used for preliminary anthocyanins structure differentiation, according to the number of OH-groups in anthocyanidin backbone as well as to a number of saccharide molecules in glycoside radicals in position 3 of the anthocyanin without MS detection. PMID:25692073

Deineka, V I; Deineka, L A; Saenko, I I

2015-01-01

201

RP-HPLC and UV Spectrophotometric Methods for Estimation of Pirfenidone in Pharmaceutical Formulations.  

PubMed

High-performance liquid chromatographic and UV spectrophotometric methods were developed and validated for the quantitative determination of pirfenidone, a novel antifibrotic agent used in idiopathic pulmonary fibrosis. Chromatography was carried out by isocratic technique on a reversed-phase C18 Zorbax Eclipse plus column with mobile phase consisting of acetonitrile:water (35:65 %v/v) at flow rate of 0.7 ml/min. The UV spectrophotometric determinations were performed at 317 nm using methanol as a solvent. The proposed methods were validated according to International Conference on Harmonization ICH Q2 (R1) guidelines. The linearity range for pirfenidone was 0.2-5.0 and 3-25 ?g/ml for HPLC and UV method, respectively. Both the methods were accurate and precise with recoveries in the range of 98 and 102 % and relative standard deviation <2 %. The developed methods were successfully applied for determination of pirfenidone in tablets. PMID:25035534

Parmar, V K; Desai, S B; Vaja, T

2014-05-01

202

Development and validation of RP-HPLC method for quantification of glipizide in biological macromolecules.  

PubMed

Glipizide (GPZ) has been widely used in the treatment of type-2 diabetics as insulin secretogague. Multiunit chitosan based GPZ floating microspheres was prepared by ionotropic gelation method for gastroretentive delivery using sodiumtripolyphosphate as cross-linking agent. Pharmacokinetic study of microspheres was done in rabbit and plasma samples were analyzed by a newly developed and validated high-performance liquid chromatographic method. Method was developed on Hypersil ODS-18 column using a mobile phase of 10mM phosphate buffer (pH, 3.5) and methanol (25:75, v/v). Elute was monitored at 230 nm with a flow rate of 1 mL/min. Calibration curve was linear over the concentration range of 25.38-2046.45 ng/mL. Retention times of GPZ and internal standard (gliclazide) were 7.32 and 9.02 min respectively. Maximum plasma drug concentration, area under the plasma drug concentration-time curve and elimination half life for GPZ floating microspheres were 2.88±0.29 ?g mL(-1), 38.46±2.26 ?g h mL(-1) and 13.55±1.36 h respectively. When the fraction of drug dissolved from microspheres in pH 7.4 was plotted against the fraction of drug absorbed, a linear correlation (R(2)=0.991) was obtained in in vitro and in vivo correlation study. PMID:24418334

Pani, Nihar Ranjan; Acharya, Sujata; Patra, Sradhanjali

2014-04-01

203

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. PMID:22457560

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

2011-01-01

204

RP-HPLC and UV Spectrophotometric Methods for Estimation of Pirfenidone in Pharmaceutical Formulations  

PubMed Central

High-performance liquid chromatographic and UV spectrophotometric methods were developed and validated for the quantitative determination of pirfenidone, a novel antifibrotic agent used in idiopathic pulmonary fibrosis. Chromatography was carried out by isocratic technique on a reversed-phase C18 Zorbax Eclipse plus column with mobile phase consisting of acetonitrile:water (35:65 %v/v) at flow rate of 0.7 ml/min. The UV spectrophotometric determinations were performed at 317 nm using methanol as a solvent. The proposed methods were validated according to International Conference on Harmonization ICH Q2 (R1) guidelines. The linearity range for pirfenidone was 0.2-5.0 and 3-25 ?g/ml for HPLC and UV method, respectively. Both the methods were accurate and precise with recoveries in the range of 98 and 102 % and relative standard deviation <2 %. The developed methods were successfully applied for determination of pirfenidone in tablets. PMID:25035534

Parmar, V. K.; Desai, S. B.; Vaja, T.

2014-01-01

205

Development and Validation of RP-HPLC Method for the Estimation of Ivabradine Hydrochloride in Tablets.  

PubMed

A simple, sensitive, precise and robust reverse-phase high-performance liquid chromatographic method for analysis of ivabradine hydrochloride in pharmaceutical formulations was developed and validated as per ICH guidelines. The separation was performed on SS Wakosil C18AR, 250×4.6 mm, 5 ?m column with methanol:25 mM phosphate buffer (60:40 v/v), adjusted to pH 6.5 with orthophosphoric acid, added drop wise, as mobile phase. A well defined chromatographic peak of Ivabradine hydrochloride was exhibited with a retention time of 6.55±0.05 min and tailing factor of 1.14 at the flow rate of 0.8 ml/min and at ambient temperature, when monitored at 285 nm. The linear regression analysis data for calibration plots showed good linear relationship with R=0.9998 in the concentration range of 30-210 ?g/ml. The method was validated for precision, recovery and robustness. Intra and Inter-day precision (% relative standard deviation) were always less than 2%. The method showed the mean % recovery of 99.00 and 98.55 % for Ivabrad and Inapure tablets, respectively. The proposed method has been successfully applied to the commercial tablets without any interference of excipients. PMID:21695008

Seerapu, Sunitha; Srinivasan, B P

2010-09-01

206

[Determination of EDTA residue in canned food products by RP-HPLC].  

PubMed

The homogenized sample is diluted with water. After adding copper(II) chloride solution and 20 mg of ascorbic acid, dilute the sample to the volume with water. After thorough mixing and microfiltration over a 0.45 microns filter, the filtrate is ready for injection into the HPLC system and detected at 254 nm. The 125 mm x 4 mm i.d. chromatographic column is packed with Hypersil ODS 5 microns, eluted with a mobile phase of water-methanol (80:20, V/V) containing 20 mmol/L tetrabutyl ammonium bromide, 0.03 mol/L sodium acetate buffer (pH 4) at a flow rate of 0.8 mL/min. The injection volume is 20 microL. The response value was linear between 10 mg/L-400 mg/L. The recovery was 95.5%-98.9%. The RSD was 0.82%-1.32%. PMID:12541709

Shi, X X; Chen, X M

2000-09-01

207

Validation and method development of Tadalafil in bulk and tablet dosage form by RP-HPLC.  

PubMed

A novel, precise, rapid and sensitive reverse phase high performance liquid chromatographic method has been developed for the validated estimation of Tadalafil in bulk and tablet dosage form. The separation was achieved on Agilent Eclipse XDB C18 column (150 mm×4.6 mm, 5 µ) using a mobile phase that consists of the buffer (potassium dihydrogen orthophosphate) and acetonitrile in the ration of 50:50 V/V, pH 6 was adjusted with orthophosphoric acid. The flow rate was maintained at 1.2 ml/min and the detection wavelength was 285 nm. The method was validated for linearity, specificity, sensitivity as per ICH guidelines. The retention time was found to be 3.181 for Tadalafil. The calibration curve was linear over the concentration range of 10-150 µg/ml. The % RSD was satisfactory which showed the method found to be reliable. The high percentage recovery confirmed the suitability of the method for estimation of Tadalafil in pharmaceutical dosage form. The developed method could be applicable for routine analysis of Tadalafil in bulk and tablet dosage form. PMID:24782284

Bojanapu, A; Subramaniam, A T; Munusamy, J; Dhanapal, K; Chennakesavalu, J; Sellappan, M; Jayaprakash, V

2015-02-01

208

Folding Properties of Cytosine Monophosphate Kinase from E. coli Indicate Stabilization through an Additional Insert in the NMP Binding Domain  

PubMed Central

The globular 25 kDa protein cytosine monophosphate kinase (CMPK, EC ID: 2.7.4.14) from E. coli belongs to the family of nucleoside monophosphate (NMP) kinases (NMPK). Many proteins of this family share medium to high sequence and high structure similarity including the frequently found ?/? topology. A unique feature of CMPK in the family of NMPKs is the positioning of a single cis-proline residue in the CORE-domain (cis-Pro124) in conjunction with a large insert in the NMP binding domain. This insert is not found in other well studied NMPKs such as AMPK or UMP/CMPK. We have analyzed the folding pathway of CMPK using time resolved tryptophan and FRET fluorescence as well as CD. Our results indicate that unfolding at high urea concentrations is governed by a single process, whereas refolding in low urea concentrations follows at least a three step process which we interpret as follows: Pro124 in the CORE-domain is in cis in the native state (Nc) and equilibrates with its trans-isomer in the unfolded state (Uc - Ut). Under refolding conditions, at least the Ut species and possibly also the Uc species undergo a fast initial collapse to form intermediates with significant amount of secondary structure, from which the trans-Pro124 fraction folds to the native state with a 100-fold lower rate constant than the cis-Pro124 species. CMPK thus differs from homologous NMP kinases like UMP/CMP kinase or AMP kinase, where folding intermediates show much lower content of secondary structure. Importantly also unfolding is up to 100-fold faster compared to CMPK. We therefore propose that the stabilizing effect of the long NMP-domain insert in conjunction with a subtle twist in the positioning of a single cis-Pro residue allows for substantial stabilization compared to other NMP kinases with ?/? topology. PMID:24205218

Beitlich, Thorsten; Lorenz, Thorsten; Reinstein, Jochen

2013-01-01

209

Impact of fluorination on proteolytic stability of peptides: a case study with ?-chymotrypsin and pepsin.  

PubMed

Protease stability is a key consideration in the development of peptide-based drugs. A major approach to increase the bioavailability of pharmacologically active peptides is the incorporation of non-natural amino acids. Due to the unique properties of fluorine, fluorinated organic molecules have proven useful in the development of therapeutically active small molecules as well as in materials and crop science. This study presents data on the ability of fluorinated amino acids to influence proteolytic stability when present in peptide sequences that are based on ideal protease substrates. Different model peptides containing fluorinated amino acids or ethylglycine in the P2, P1'or P2' positions were designed according to the specificities of the serine protease, ?-chymotrypsin (EC 3.4.21.1) or the aspartic protease, pepsin (EC 3.4.23.1). The proteolytic stability of the peptides toward these enzymes was determined by an analytical RP-HPLC assay with fluorescence detection and compared to a control sequence. Molecular modeling was used to support the interpretation of the structure-activity relationship based on the analysis of potential ligand-enzyme interactions. Surprisingly, an increase in proteolytic stability was observed only in a few cases. Thus, this systematic study shows that the proteolytic stability of fluorinated peptides is not predictable, but rather is a very complex phenomenon that depends on the particular enzyme, the position of the substitution relative to the cleavage site and the fluorine content of the side chain. PMID:25193166

Asante, Vivian; Mortier, Jérémie; Wolber, Gerhard; Koksch, Beate

2014-12-01

210

Stability-indicating HPLC assay for lysine-proline-valine (KPV) in aqueous solutions and skin homogenates.  

PubMed

A simple, sensitive and stability-indicating high-performance liquid chromatographic (HPLC) assay method was developed and validated for a bioactive peptide, lysine-proline-valine (KPV) in aqueous solutions and skin homogenates. Chromatographic separation was achieved on a reversed phase Phenomenex C18 column (4.6 × 250 mm, packed with 5 µm silica particles) with a gradient mobile phase consisting of 0.1% trifluoroacetic acid (TFA) in water (A) and 0.1% TFA in acetonitrile (B). The proposed HPLC method was validated with respect to accuracy, precision, linearity, repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The calibration curve was linear with a correlation coefficient (r) of 0.9999. Relative standard deviation values of accuracy and precision experiments were <2. The LOD and LOQ of KPV were 0.01 and 0.25 µg/mL, respectively. Under stress conditions (acid, alkali and hydrogen peroxide) KPV yielded lys-pro-diketopiperazine as major degradation product, which was identified by flow injection MS analysis. The developed HPLC method was found to be efficient in separating the active peptide from its degradation products generated under various stress conditions. Also, the validated method was able to separate KPV from other peaks arising from endogenous components of the skin homogenate. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25298219

Pawar, Kasturi R; Mulabagal, Vanisree; Smith, Forrest; Kolli, Chandra S; Rangari, Vijaya K; Babu, R Jayachandra

2015-05-01

211

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

2009-01-01

212

Kinetic Study of the Alkaline Degradation of Oseltamivir Phosphate and Valacyclovir Hydrochloride using Validated Stability Indicating HPLC.  

PubMed

Aqueous alkaline degradation was performed for oseltamivir phosphate (OP) and valacyclovir hydrochloride (VA). Isocratic stability indicating the use of high-performance liquid chromatography (HPLC) was presented for each drug in the presence of its degradation product. The separations were performed using the Nucleosil ODS column and a mobile phase consisting of phosphate buffer (pH = 7), acetonitrile, and methanol 50:25:25 (v/v/v) for OP. For VA separation, a Nucleosil CN column using phosphate buffer (pH = 7) and methanol 85:15 (v/v) was used as a mobile phase. Ultraviolet detection at 210 nm and 254 nm was used for OP and VA, respectively. The method showed high sensitivity concerning linearity, accuracy, and precision over the range 1-250 ?g mL(-1) for both drugs. The proposed method was used to determine the drug in its pharmaceutical formulation and to investigate the degradation kinetics of each drug's alkaline-stressed samples. The reactions were found to follow a first-order reaction. The activation energy could also be estimated. International Conference on Harmonisation guidelines were adopted for method validation. PMID:24932100

Al-Bagary, Ramzia I; El-Zaher, Asmaa A; Morsy, Fahima A; Fouad, Mai M

2014-01-01

213

Quantification of halobetasol propionate and its impurities present in topical dosage forms by stability-indicating LC method.  

PubMed

A novel, sensitive, stability-indicating, gradient, reverse-phase high-performance liquid chromatographic method has been developed for quantitative determination of halobetasol propionate and its impurities in topical dosage forms. The chromatographic separation was achieved on a Phenomenex Synergi polar reverse phase, 250 × 4.6 mm, 4 µm column. Mobile phase A comprises a mixture of 0.01 M KH2PO4 buffer containing 0.2% 1-octane sulfonic acid sodium salt (pH 3.0), acetonitrile and methanol in the ratio 80:15:05 (v/v/v), respectively, and mobile phase B contains a mixture of 0.01 M KH2PO4 buffer containing 0.2% 1-octane sulfonic acid sodium salt (pH 3.0), acetonitrile and methanol in the ratio 20:70:10 (v/v/v), respectively. The flow rate is 0.8 mL min(-1). The column compartment temperature is set at 40°C and the detection wavelength is set at 240 nm. The resolutions between Halobetasol propionate and all the impurities are >2.0 for all pairs of compounds. The drug product was subjected to International Conference on Harmonization (ICH)-prescribed hydrolytic, oxidative, photolytic and thermal stress conditions. The method is validated as per the ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, robustness and ruggedness. PMID:24784115

Nalwade, Santaji; Reddy, Vangala Ranga; Kulkarni, Dipak; Todamal, Sandip

2015-01-01

214

Stability-indicating HPLC method for determination of naftazone in tablets. Application to degradation kinetics and content uniformity testing.  

PubMed

A simple, sensitive, stability-indicating HPLC method was developed and validated for the quantitative determination of the vasoprotective drug, naftazone in presence of its degradation products. The analysis was carried out on a Nucleosil 100-5 phenyl column (250 mm × 4.6 mm, 5 ?m) using a mobile phase consisting of methanol-0.02 M sodium dihydrogen phosphate mixture (60:40, v/v) of pH 6.0. The analyses were performed at ambient temperature with a flow rate of 1.0 mL/min and UV detection at 270 nm. The method showed good linearity over the concentration range of 0.1-10.0 ?g/mL with a lower detection limit of 0.032 and quantification limit of 0.096 ?g/mL. The suggested method was successfully applied for the analysis of naftazone in its commercial tablets. Moreover, it was utilized to investigate the kinetics of alkaline, acidic and oxidative degradation of the drug. The apparent first-order rate constants, half-life times, and activation energies of the degradation process were calculated. The pH-rate profile curve was derived. Furthermore, the proposed method was successfully applied to the content uniformity testing of naftazone tablets. PMID:21801479

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

2011-08-01

215

Stability-indicating high-performance liquid chromatographic determination of chlorpropamide, tolbutamide, and their respective sulfonamide degradates.  

PubMed

A quantitative high-performance liquid chromatographic method for the determination of chlorpropamide, tolbutamide, and their respective hydrolysis products, p-chlorobenzenesulfonamide and p-toluenesulfonamide, in solid dosage forms was developed. The method is stability indicating and can be used to determine the sulfonamide hydrolysis product and the intact drug in the presence of minor degradates. Method reproducibility, demonstrated by repeated injections of a calibration standard, was 1.21%. The lower limit of quantitation of the hydrolysis products, p-chlorobenzenesulfonamide and p-toluenesulfonamide, was 0.2 microgram/5-microliter injection. The accuracy of the method for intact drugs was determined by comparison of the HPLC results to those obtained by the appropriate USP or BP assays. The mean of the results obtained by the two methods differed by 0.7% for chlorpropamide and 0.3% for tolbutamide. Pure drug samples were spiked with amounts of the hydrolysis products ranging from 20 to 120% of the intact content. The mean percent recovery for p-chlorobenzenesulfonamide was 98.6%; for p-toluenesulfonamide, it was 100.6%. A qualitative TLC procedure for the detection of chlorpropamide, p-chlorobenzenesulfonamide, dipropylurea, propylurea, n-propylamine, tolbutamide, p-toluenesulfonamide, dibutylurea, butylurea, and n-butylamine is also described. PMID:430494

Robertson, D L; Butterfield, A G; Kolasinski, H; Lovering, E G; Matsui, F F

1979-05-01

216

Stability Indicating High-Performance Liquid Chromatography Method for the Estimation of Artemether in Capsule Dosage Forms  

PubMed Central

A new simple, sensitive, precise, and accurate high-performance liquid chromatography (HPLC) method of analysis for artemether both as a bulk drug and in capsule formulations was developed and validated. The method employed mobile phase acetonitrile (ACN) and buffer in the ratio 65:35 of pH 6.5 adjusted with tryethylamine. The linear regression analysis data for the calibration plots showed good linear relationship with r2 = 0.9996 in the concentration range 250-750 ?g/ml. The mean value slope and intercept were 9355.5 and ?93.5, respectively. The method was validated for precision, accuracy, and recovery studies. Limit of detection (LOD) and Limit of quantitation (LOQ) for artemether were found to be 21.83-750 ?g/ml, respectively. The method has been successfully applied in the analysis of marketed capsule formulations. The presented method was found to be reliable to separate all the degradents from all the stress conditions with resolution of more than 1.5 showing that it is a stability indicating method. PMID:21331197

Shrivastava, A; Issarani, R; Nagori, BP

2010-01-01

217

Kinetic Study of the Alkaline Degradation of Oseltamivir Phosphate and Valacyclovir Hydrochloride using Validated Stability Indicating HPLC  

PubMed Central

Aqueous alkaline degradation was performed for oseltamivir phosphate (OP) and valacyclovir hydrochloride (VA). Isocratic stability indicating the use of high-performance liquid chromatography (HPLC) was presented for each drug in the presence of its degradation product. The separations were performed using the Nucleosil ODS column and a mobile phase consisting of phosphate buffer (pH = 7), acetonitrile, and methanol 50:25:25 (v/v/v) for OP. For VA separation, a Nucleosil CN column using phosphate buffer (pH = 7) and methanol 85:15 (v/v) was used as a mobile phase. Ultraviolet detection at 210 nm and 254 nm was used for OP and VA, respectively. The method showed high sensitivity concerning linearity, accuracy, and precision over the range 1–250 ?g mL?1 for both drugs. The proposed method was used to determine the drug in its pharmaceutical formulation and to investigate the degradation kinetics of each drug’s alkaline-stressed samples. The reactions were found to follow a first-order reaction. The activation energy could also be estimated. International Conference on Harmonisation guidelines were adopted for method validation. PMID:24932100

Al-Bagary, Ramzia I; El-Zaher, Asmaa A; Morsy, Fahima A; Fouad, Mai M

2014-01-01

218

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

PubMed

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 C(18) 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. PMID:23440900

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

2012-05-01

219

Enhanced cellular uptake and metabolic stability of lipo-oligoarginine peptides.  

PubMed

Developing efficient cellular delivery vectors is crucial for designing novel therapeutic agents to enhance their plasma membrane permeability and metabolic stability in cells. Previously, we engineered cell penetrating peptide vectors named as "lipo-oligoarginine peptides" (LOAPs) by conjugating a proper combination of fatty acid and oligoarginine that translocated into cell easily without adverse effect on cell viability. In the present study, we report a systemic evaluation of cellular uptake and metabolic stability of LOAPs in Jurkat cells by introducing different combination of D-Arg residues in the peptide backbone. The cellular uptake and intracellular fate, cell viability, and metabolic stability and proteolytic degradation patterns of various LOAPs consisted of different combination of L- and D-Arg sequences were confirmed by flow cytometry, cytotoxicity assay, and analytical RP-HPLC with MALDI-TOF mass. All investigated LOAPs penetrated the cell efficiently with low cellular toxicity. The LOAPs having D-Arg residues at their N-termini seemed to have better metabolic stability than the LOAPs having C-terminal D-Arg residues. The metabolic degradation patterns were similar among all investigated LOAPs. The major hydrolytic site was between lauroyl group and ?-Ala residue. Without the lipid chain, the oligoarginine peptide was pumped out ofcells easily. The results presented in this study suggest that structurally modified LOAPs could be used as a novel CPP design toward improved therapeutic application. PMID:22252426

Lee, Jae Sam; Tung, Ching-Hsuan

2011-01-01

220

A Stability-Indicating HPLC Method for the Determination of Nitrosylcobalamin (NO-Cbl), a Novel Vitamin B12 Analog  

PubMed Central

Nitrosylcobalamin (NO-Cbl), a novel vitamin B12 analog and anti-tumor agent, functions as a biologic ‘Trojan horse’, utilizing the vitamin B12 transcobalamin II transport protein and cell surface receptor to specifically target cancer cells. a stability-indicating HPLC method was developed for the detection of NO-Cbl during forced degradation studies. This method utilized an ascentis® RP-amide (150 mm × 4.6 mm, 5 ?m) column at 35 °C with a mobile phase (1.0 mL min?1) combining a gradient of methanol and an acetate buffer at pH 6.0. Detection wavelengths of 450 and 254 nm were used to detect corrin and non-corrin-based products, respectively. NO-Cbl, synthesized from hydroxocobalamin and pure nitric oxide gas, was subjected to degradative stress conditions including oxidation, hydrolysis and thermal and radiant energy challenge. The method was validated by assessing linearity, accuracy, precision, detection and quantitation limits and robustness. The method was applied successfully for purity assessment of synthesized NO-Cbl and for the determination of NO-Cbl during kinetic studies in aqueous solution and in solid-state degradation assessments. This HPLC method is suitable for the separation of cobalamins in aqueous and methanolic solutions, for routine detection of NO-Cbl and for purity assessment of synthesized NO-Cbl. additionally, this method has potential application in identification and monitoring of diseases involving altered nitric oxide homeostasis where vitamin B12 therapy is utilized to scavenge excess nitric oxide, subsequently resulting in the in vivo production of NO-Cbl. PMID:24855323

Dunphy, Michael J.; Sysel, Annette M.; Lupica, Joseph A.; Griffith, Kristie; Sherrod, Taylor

2014-01-01

221

A Stability-Indicating HPLC Method for the Determination of Nitrosylcobalamin (NO-Cbl), a Novel Vitamin B12 Analog.  

PubMed

Nitrosylcobalamin (NO-Cbl), a novel vitamin B12 analog and anti-tumor agent, functions as a biologic 'Trojan horse', utilizing the vitamin B12 transcobalamin II transport protein and cell surface receptor to specifically target cancer cells. a stability-indicating HPLC method was developed for the detection of NO-Cbl during forced degradation studies. This method utilized an ascentis(®) RP-amide (150 mm × 4.6 mm, 5 ?m) column at 35 °C with a mobile phase (1.0 mL min(-1)) combining a gradient of methanol and an acetate buffer at pH 6.0. Detection wavelengths of 450 and 254 nm were used to detect corrin and non-corrin-based products, respectively. NO-Cbl, synthesized from hydroxocobalamin and pure nitric oxide gas, was subjected to degradative stress conditions including oxidation, hydrolysis and thermal and radiant energy challenge. The method was validated by assessing linearity, accuracy, precision, detection and quantitation limits and robustness. The method was applied successfully for purity assessment of synthesized NO-Cbl and for the determination of NO-Cbl during kinetic studies in aqueous solution and in solid-state degradation assessments. This HPLC method is suitable for the separation of cobalamins in aqueous and methanolic solutions, for routine detection of NO-Cbl and for purity assessment of synthesized NO-Cbl. additionally, this method has potential application in identification and monitoring of diseases involving altered nitric oxide homeostasis where vitamin B12 therapy is utilized to scavenge excess nitric oxide, subsequently resulting in the in vivo production of NO-Cbl. PMID:24855323

Dunphy, Michael J; Sysel, Annette M; Lupica, Joseph A; Griffith, Kristie; Sherrod, Taylor; Bauer, Joseph A

2014-04-01

222

Stability indicating spectrophotometric and spectrodensitometric methods for the determination of diatrizoate sodium in presence of its degradation product  

NASA Astrophysics Data System (ADS)

Three sensitive, selective, and precise stability indicating methods for the determination of the X-ray contrast agent, diatrizoate sodium (DTA), in the presence of its acidic degradation product (highly cytotoxic 3,5 diamino metabolite) and in pharmaceutical formulation were developed and validated. The first method is a first derivative (D1) spectrophotometric one, which allows the determination of DTA in the presence of its degradate at 231.2 nm (corresponding to zero crossing of the degradate) over a concentration range of 2-24 ?g/mL with mean percentage recovery 99.95 ± 0.97%. The second method is the first derivative of the ratio spectra (DD1) by measuring the peak amplitude at 227 nm over the same concentration range as D1 spectrophotometric method, with mean percentage recovery 99.99 ± 1.15%. The third method is a TLC-densitometric one, where DTA was separated from its degradate on silica gel plates using chloroform:methanol:ammonium hydroxide (20:10:2 by volume) as a developing system. This method depends on quantitative densitometric evaluation of thin layer chromatogram of DTA at 238 nm over a concentration range of 4-20 ?g/spot, with mean percentage recovery 99.88 ± 0.89%. The selectivity of the proposed methods was tested using laboratory-prepared mixtures. The proposed methods have been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives. The results were statistically compared with the official US pharmacopeial method. No significant difference for either accuracy or precision was observed.

Abd El-Rahman, Mohamed K.; Riad, Safaa M.; Abdel Gawad, Sherif A.; Fawaz, Esraa M.; Shehata, Mostafa A.

2015-02-01

223

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

224

Validation of a high performance liquid chromatography method for the stabilization of epigallocatechin gallate.  

PubMed

Epigallocatechin gallate (EGCG) is a green tea catechin with potential health benefits, such as anti-oxidant, anti-carcinogenic and anti-inflammatory effects. In general, EGCG is highly susceptible to degradation, therefore presenting stability problems. The present paper was focused on the study of EGCG stability in HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) medium regarding the pH dependency, storage temperature and in the presence of ascorbic acid a reducing agent. The evaluation of EGCG in HEPES buffer has demonstrated that this molecule is not able of maintaining its physicochemical properties and potential beneficial effects, since it is partially or completely degraded, depending on the EGCG concentration. The storage temperature of EGCG most suitable to maintain its structure was shown to be the lower values (4 or -20 °C). The pH 3.5 was able to provide greater stability than pH 7.4. However, the presence of a reducing agent (i.e., ascorbic acid) was shown to provide greater protection against degradation of EGCG. A validation method based on RP-HPLC with UV-vis detection was carried out for two media: water and a biocompatible physiological medium composed of Transcutol(®)P, ethanol and ascorbic acid. The quantification of EGCG for purposes, using pure EGCG, requires a validated HPLC method which could be possible to apply in pharmacokinetic and pharmacodynamics studies. PMID:25175728

Fangueiro, Joana F; Parra, Alexander; Silva, Amélia M; Egea, Maria A; Souto, Eliana B; Garcia, Maria L; Calpena, Ana C

2014-11-20

225

Application of spectrophotometric, densitometric, and HPLC techniques as stability indicating methods for determination of Zaleplon in pharmaceutical preparations  

NASA Astrophysics Data System (ADS)

Spectrophotometric, spectrodensitometric and HPLC are stability indicating methods described for determination of Zaleplon in pure and dosage forms. As Zaleplon is easily degradable, the proposed techniques in this manuscript are adopted for its determination in presence of its alkaline degradation product, namely N-[4-(3-cyano-pyrazolo[1,5a]pyridin-7-yl)-phenyl]- N-ethyl-acetamide. These approaches are successfully applied to quantify Zaleplon using the information included in the absorption spectra of appropriate solutions. The second derivative (D 2) spectrophotometric method, allows determination of Zaleplon without interference of its degradate at 235.2 nm using 0.01N HCl as a solvent with obedience to Beer's law over a concentration range of 1-10 ?g ml -1 with mean percentage recovery 100.24 ± 0.86%. The first derivative of the ratio spectra ( 1DD) based on the simultaneous use of ( 1DD) and measurement at 241.8 nm using the same solvent and over the same concentration range as (D 2) spectrophotometric method, with mean percentage recovery 99.9 ± 1.07%. The spectrodensitometric analysis allows the separation and quantitation of Zaleplon from its degradate on silica gel plates using chloroform:acetone:ammonia solution (9:1:0.2 by volume) as a mobile phase. This method depends on quantitave densitometric evaluation of thin layer chromatogram of Zaleplon at 338 nm over a concentration range of 0.2-1 ?g band -1, with mean percentage recovery 99.73 ± 1.35. Also a reversed-phase liquid chromatographic method using 5-C8 (22 cm × 4.6 mm i.d. 5 ?m particle size) column was described and validated for quantitation of Zaleplon using acetonitrile:deionised water (35:65, v/v) as a mobile phase using Paracetamol as internal standard and a flow rate of 1.5 ml min -1 with UV detection of the effluent at 232 nm at ambient temperature over a concentration range of 2-20 ?g ml -1 with mean percentage recovery 100.19 ± 1.15%. The insignificance difference of the proposed methods results with those of the reference one proved their accuracy and precision.

Metwally, Fadia H.; Abdelkawy, M.; Abdelwahab, Nada S.

2007-12-01

226

On the possibility of the space-dependence of the stability indicator (decay ratio) of a BWR  

E-print Network

to the discontinuous dependence of the decay ratio (DR) on the working point of the reactor on the power-flow map (Van Christophe Demazie`re *, Imre Pa´zsit Department of Reactor Physics, Chalmers University of Technology, SE ratio (DR) which is used to quantify the stability properties of boiling water reactors (BWRs

Pázsit, Imre

227

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

228

Granulocyte-macrophage colony stimulating factor: Evaluation of biopharmaceutical formulations by stability-indicating RP-LC method and bioassay  

Microsoft Academic Search

The granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that regulates the proliferation and differentiation of hematopoietic cells and activates granulocytes and macrophages. A reversed-phase liquid chromatography (RP-LC) method was validated for the assessing of the stability of non-glycosylated recombinant rhGM-CSF (Molgramostim) in biopharmaceutical formulations. The RP-LC method was carried out on a Jupiter C4 column (250 mm × 4.6 mm i.d.), maintained at

Diogo Paim Leal; Ricardo Bizogne Souto; Renato Schutkoski; Ana Cláudia Bergamo; Sérgio Luiz Dalmora

2011-01-01

229

A Fast, Stability-Indicating, and Validated Liquid Chromatography Method for the Purity Control of Lercanidipine Hydrochloride in Tablet Dosage Form  

PubMed Central

A robust, sensitive, and stability-indicating rapid resolution liquid chromatography method for the simultaneous determination of process impurities and degradation products of lercanidipine hydrochloride in pharmaceutical dosage form was developed and validated. The chromatographic separation was performed on the Zorbax SB C18 [(50 × 4.6) mm] 1.8 ?m column, using gradient elution of a potassium dihydrogen phosphate buffer (pH 3.5, 0.01 M) and acetonitrile. The flow rate was 1.0 ml/min and UV detection was performed at 220 nm. The method was further evaluated for its stability-indicating capability by hydrolytic, oxidative, thermal, thermal with moisture, and photolytic degradation studies. All acceptance criteria of the International Conference on Harmonization guidelines for validation were covered in the method validation. This method can be used for purity control during manufacture and real time stability studies. A shorter run time of 10 minutes and good solution stability for at least 48 hours allowed the quantification of more than 50 samples per day with comparatively lower costs than existing methods. PMID:24959405

Mehta, Saumil; Singh, Sukhdev; Chikhalia, Kishor

2014-01-01

230

Stability-indicating high-performance thin-layer chromatographic determination of levonorgestrel and ethinyloestradiol in bulk drug and in low-dosage oral contraceptives  

Microsoft Academic Search

A stability-indicating high-performance thin-layer chromatography (HPTLC) method was developed and validated for simultaneous determination of steroidal hormones levonorgestrel and ethinyloestradiol both in bulk drug and in low-dosage oral contraceptives. Optimization of conditions for the spectrodensitometric procedure was reached by eluting HPTLC silica gel plates in a 10cm×10cm horizontal chamber. The solvent system consisted of hexane–chloroform–methanol (1.0:3.0:0.25, v\\/v\\/v). This system was

Ali Reza Fakhari; Afshin Rajabi Khorrami; Mojtaba Shamsipur

2006-01-01

231

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

232

A VALIDATED STABILITY INDICATING HPTLC METHOD FOR SIMULTANEOUS ESTIMATION OF CEFPODOXIME PROXETIL AND POTASSIUM CLAVULANATE IN BULK AND TABLET DOSAGE FORM  

Microsoft Academic Search

Cefpodoxime proxetil (Cef) and Potassium clavulanate (Pot.clav.) are used in the treatment of acute otitis media, typhoid fever, pharyngitis and tonsillitis. A simple, selective and stability indicating HPTLC method has been established for the simultaneous analysis of Cef and Pot.clav. in pharmaceutical formulations. The method uses aluminum-backed silica gel 60F254 HPTLC plates as stationary phase with toluene:methanol:chloroform:acetonitrile [4:3:2:1.5 (v\\/v\\/v\\/v)] as

A. B. Thomas; S. B. Dighe; R. K. Nanda; L. P. Kothapalli; S. N. Jagdale; A. D. Deshpande

2010-01-01

233

Chromium Oxidation State in Planetary Basalts: Oxygen Fugacity Indicator and Critical Variable for Cr-Spinel Stability  

NASA Technical Reports Server (NTRS)

Cr is a ubiquitous and relatively abundant minor element in basaltic, planetary magmas. At the reduced oxidation states (stability and Cr concentration of magmatic phases such as spinel, clinopyroxene, and olivine. However, understanding the Cr valence in quenched melts has historically been plagued with analytical issues, and only recently has reliable methodology for quantifying Cr valence in quenched melts been developed. Despite this substantial difficulty, the pioneering works of Hanson and Jones and Berry and O'Neill provided important insights into the oxidation state of Cr in in silicate melts. Here we present a series of 1-bar gas mixing experiments performed with a Fe-rich basaltic melt in which have determined the Cr redox ratio of the melt at over a range of fO2 values by measuring this quantity in olivine with X-ray Absorption Near Edge Spectroscopy (XANES). The measured Cr redox ratio of the olivine phenocrysts can be readily converted to the ratio present in the conjugate melt via the ratio of crystal-liquid partition coefficients for Cr3+ and Cr2+. We have applied these results to modeling Cr spinel stability and Cr redox ratios in a primitive, iron-rich martian basalt.

Bell, A. S.; Burger, P. V.; Le, Loan; Papike, J. J.; Jone, J.; Shearer, C. K.

2014-01-01

234

Improvement of a stability-indicating method by Quality-by-Design versus Quality-by-Testing: a case of a learning process.  

PubMed

The understanding of the method is a major concern when developing a stability-indicating method and even more so when dealing with impurity assays from complex matrices. In the presented case study, a Quality-by-Design approach was applied in order to optimize a routinely used method. An analytical issue occurring at the last stage of a long-term stability study involving unexpected impurities perturbing the monitoring of characterized impurities needed to be resolved. A compliant Quality-by-Design (QbD) methodology based on a Design of Experiments (DoE) approach was evaluated within the framework of a Liquid Chromatography (LC) method. This approach allows the investigation of Critical Process Parameters (CPPs), which have an impact on Critical Quality Attributes (CQAs) and, consequently, on LC selectivity. Using polynomial regression response modeling as well as Monte Carlo simulations for error propagation, Design Space (DS) was computed in order to determine robust working conditions for the developed stability-indicating method. This QbD compliant development was conducted in two phases allowing the use of the Design Space knowledge acquired during the first phase to define the experimental domain of the second phase, which constitutes a learning process. The selected working condition was then fully validated using accuracy profiles based on statistical tolerance intervals in order to evaluate the reliability of the results generated by this LC/ESI-MS stability-indicating method. A comparison was made between the traditional Quality-by-Testing (QbT) approach and the QbD strategy, highlighting the benefit of this QbD strategy in the case of an unexpected impurities issue. On this basis, the advantages of a systematic use of the QbD methodology were discussed. PMID:24176744

Hubert, C; Lebrun, P; Houari, S; Ziemons, E; Rozet, E; Hubert, Ph

2014-01-01

235

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

236

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

2007-11-01

237

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

2013-02-01

238

Validated Stability indicating Spectrophotometric Method for the Determination of Acetazolamide in Dosage Forms through Complex Formation with Palladium (II)  

PubMed Central

A simple and sensitive spectrophotometric method was developed for the determination of acetazolamide (ACM) in pure form and pharmaceutical preparations. The proposed method is based on the complex formation of acetazolamide with Palladium (II) chloride in acetate buffer pH5.4 and measuring the absorbance at 308 nm. The absorbance- concentration plot was rectilinear over the concentration range of 5-70 ?g/ml with a minimum detection limit (LOD) of 0.98 ?g/ml, limit of quantification (LOQ) of 2.96 ?g/ml, and a molar absorptivity ?=2.7 × 103 L/mol.cm. The factors affecting the absorbance of the formed complex were carefully studied and optimized. The composition of the complex as well as its stability constant was also investigated. The proposed method was applied for the determination of acetazolamide in its tablets and the results obtained were favorably compared with those obtained using the official method. A proposal of the reaction pathway was postulated. PMID:23675188

Walash, M. I.; El-Brashy, A.; El-Enany, N.; Wahba, M. E. K.

2010-01-01

239

Stability-indicating HPLC-UV for the determination of 4-bromomethyl-3-nitrobenzoic acid, a bioactive nitrocompound.  

PubMed

The nitroaromatic compound 4-bromomethyl-3-nitrobenzoic acid (ANB) is a promising antitumoral agent whose activity has recently been investigated. Forced degradation studies were conducted on ANB with a high-performance liquid chromatography-ultraviolet assay to establish its stability and selectivity. ANB was subjected to degradation studies under hydrolytic (acid and alkaline), oxidative and light exposition conditions. The compound showed greater lability only in acid and alkaline conditions by forming a major degradation product. The chromatographic separation of ANB and its degradation product was achieved on an octadecylsilane column using a mobile phase of methanol-water (80:20, v/v), pH 4.0 adjusted with formic acid, flow rate of 0.7 mL/min, ultraviolet diode array detection at ? 271 nm, injection volume of 20 µL and temperature of 30°C. The method was validated according to International Conference on Harmonization guidelines with respect to precision (average relative standard deviation 0.67%), accuracy (average 99.97%), linearity (y = 118730x + 12912; coefficient of determination > 0.999), specificity and robustness (p > 0.05). The degradation product formed as a result from the hydrolysis of nitrobenzyl bromide, corresponded to its benzyl alcohol, 4-hydroxymethyl-3-nitrobenzoic acid (ANOH) and was characterized by co-elution with a synthetic ANOH working standard. PMID:23788018

de Freitas, Maria Betânia; Lages, Eduardo Burgarelli; Gonçalves, Isadora Marques Brum; de Oliveira, Renata Barbosa; Vianna-Soares, Cristina Duarte

2014-07-01

240

Engineering deamidation-susceptible asparagines leads to improved stability to thermal cycling in a lipase.  

PubMed

At high temperatures, protein stability is influenced by chemical alterations; most important among them is deamidation of asparagines. Deamidation kinetics of asparagines depends on the local sequence, solvent, pH, temperature, and the tertiary structure. Suitable replacement of deamidated asparagines could be a viable strategy to improve deamidation-mediated loss in protein properties, specifically protein thermostability. In this study, we have used nano RP-HPLC coupled ESI MS/MS approach to identify residues susceptible to deamidation in a lipase (6B) on heat treatment. Out of 15 asparagines and six glutamines in 6B, only five asparagines were susceptible to deamidation at temperatures higher than 75°C. These five positions were subjected to site saturation mutagenesis followed by activity screen to identify the most suitable substitutions. Only three of the five asparagines were found to be tolerant to substitutions. Best substitutions at these positions were combined into a mutant. The resultant lipase (mutC) has near identical secondary structure and improved thermal tolerance as compared to its parent. The triple mutant has shown almost two-fold higher residual activity compared to 6B after four cycles at 90°C. MutC has retained more than 50% activity even after incubation at 100°C. Engineering asparagines susceptible to deamidation would be a potential strategy to improve proteins to withstand very high temperatures. PMID:25043738

Bhanuramanand, K; Ahmad, Shoeb; Rao, N M

2014-10-01

241

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

242

Improved efficiency and stability of secnidazole – An ideal delivery system  

PubMed Central

Secnidazole (?,2-Dimethyl-5-nitro-1H-imidazole-1-ethanol) is a highly effective drug against a variety of G+/G? bacteria but with significant side effects because it is being used in very high concentration. In this study, gold nanoparticles (GNPS) were selected as a vehicle to deliver secnidazole drug at the specific site with more accuracy which made the drug highly effective at substantially low concentrations. The as-synthesized GNPs were capped with Human Serum Albumin (HSA) and subsequently bioconjugated with secnidazole because HSA provides the stability and improves the solubility of the bioconjugated drug, secnidazole. The quantification of covalently bioconjugated secnidazole with HSA encapsulated on enzymatically synthesized GNPs was done with RP-HPLC having SPD-20 A UV/VIS detector by using the C-18 column. The bioconjugation of GNPs with secnidazole was confirmed by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The bioconjugated GNPs were characterized by UV–VIS spectroscopy, TEM, Scanning Electron Microscopy (SEM) and DLS. Zeta potential confirmed the stability and uniform distribution of particles in the emulsion of GNPs. The separation of bioconjugated GNPs, unused GNPs and unused drug was done by gel filtration chromatography. The minimal inhibitory concentration of secnidazole-conjugated gold nanoparticles (Au-HSA-Snd) against Klebsiella pneumonia (NCIM No. 2957) and Bacillus cereus (NCIM No. 2156) got improved by 12.2 times and 14.11 times, respectively, in comparison to pure secnidazole. Precisely, the MIC of Au-HSA-Snd against K. pneumonia (NCIM No. 2957) and B. cereus (NCIM No. 2156) were found to be 0.35 and 0.43 ?g/ml, respectively whereas MIC of the pure secnidazole drug against the same bacteria were found to be 4.3 and 6.07 ?g/ml, respectively. PMID:25561882

Khan, Salman; Haseeb, Mohd; Baig, Mohd Hassan; Bagga, Paramdeep Singh; Siddiqui, H.H.; Kamal, M.A.; Khan, Mohd Sajid

2014-01-01

243

Improved efficiency and stability of secnidazole - An ideal delivery system.  

PubMed

Secnidazole (?,2-Dimethyl-5-nitro-1H-imidazole-1-ethanol) is a highly effective drug against a variety of G(+)/G(-) bacteria but with significant side effects because it is being used in very high concentration. In this study, gold nanoparticles (GNPS) were selected as a vehicle to deliver secnidazole drug at the specific site with more accuracy which made the drug highly effective at substantially low concentrations. The as-synthesized GNPs were capped with Human Serum Albumin (HSA) and subsequently bioconjugated with secnidazole because HSA provides the stability and improves the solubility of the bioconjugated drug, secnidazole. The quantification of covalently bioconjugated secnidazole with HSA encapsulated on enzymatically synthesized GNPs was done with RP-HPLC having SPD-20 A UV/VIS detector by using the C-18 column. The bioconjugation of GNPs with secnidazole was confirmed by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The bioconjugated GNPs were characterized by UV-VIS spectroscopy, TEM, Scanning Electron Microscopy (SEM) and DLS. Zeta potential confirmed the stability and uniform distribution of particles in the emulsion of GNPs. The separation of bioconjugated GNPs, unused GNPs and unused drug was done by gel filtration chromatography. The minimal inhibitory concentration of secnidazole-conjugated gold nanoparticles (Au-HSA-Snd) against Klebsiella pneumonia (NCIM No. 2957) and Bacillus cereus (NCIM No. 2156) got improved by 12.2 times and 14.11 times, respectively, in comparison to pure secnidazole. Precisely, the MIC of Au-HSA-Snd against K. pneumonia (NCIM No. 2957) and B. cereus (NCIM No. 2156) were found to be 0.35 and 0.43 ?g/ml, respectively whereas MIC of the pure secnidazole drug against the same bacteria were found to be 4.3 and 6.07 ?g/ml, respectively. PMID:25561882

Khan, Salman; Haseeb, Mohd; Baig, Mohd Hassan; Bagga, Paramdeep Singh; Siddiqui, H H; Kamal, M A; Khan, Mohd Sajid

2015-01-01

244

A Stability-Indicating HPLC-DAD Method for Determination of Stiripentol: Development, Validation, Kinetics, Structure Elucidation and Application to Commercial Dosage Form  

PubMed Central

A rapid, simple, sensitive, and accurate isocratic reversed-phase stability-indicating high performance liquid chromatography method has been developed and validated for the determination of stiripentol and its degradation product in its bulk form and pharmaceutical dosage form. Chromatographic separation was achieved on a Symmetry C18 column and quantification was achieved using photodiode array detector (DAD). The method was validated in accordance with the ICH requirements showing specificity, linearity (r2 = 0.9996, range of 1–25??g/mL), precision (relative standard deviation lower than 2%), accuracy (mean recovery 100.08 ± 1.73), limits of detection and quantitation (LOD = 0.024 and LOQ = 0.081??g/mL), and robustness. Stiripentol was subjected to various stress conditions and it has shown marked stability under alkaline hydrolytic stress conditions, thermal, oxidative, and photolytic conditions. Stiripentol degraded only under acidic conditions, forming a single degradation product which was well resolved from the pure drug with significantly different retention time values. This degradation product was characterized by 1H-NMR and 13C-NMR spectroscopy as well as ion trap mass spectrometry. The results demonstrated that the method would have a great value when applied in quality control and stability studies for stiripentol. PMID:25371844

Darwish, Hany W.; Abdelhameed, Ali S.; Bakheit, Ahmed H.; Khalil, Nasr Y.; Al-Majed, Abdulrahman A.

2014-01-01

245

Development and validation of a stability-indicating LC-UV method for the determination of pantethine and its degradation product based on a forced degradation study.  

PubMed

Pantethine (d-bis-(N-pantothenyl-?-aminoethyl)-disulfide, PAN), the stable disulfide form of pantetheine, has beneficial effects in vascular diseases being able to decrease the hyperlipidaemia, moderate the platelet function and prevent the lipid peroxidation. Furthermore, recent studies suggested that PAN may be an effective therapeutic agent for cerebral malaria and, possibly, for neurodegenerative processes. Interestingly, in the literature, there were no data dealing with the chemical stability and the analytical aspects of PAN. Hence, in the present work the chemical stability of PAN was for the first time established through a forced degradation study followed by liquid chromatography tandem mass spectrometry investigation showing the formation of three degradation products of PAN (PD1, PD2 and POx) arising from hydrolytic, thermal and oxidative stresses. Based on these data a stability-indicating LC-UV method for simultaneous estimation of PAN, and its most relevant degradation product (PD1) was developed and validated; moreover the method allowed also the separation and the quantification of the preservative system, constituted by a paraben mixture. The method showed linearity for PAN (0.4-1.2mgmL(-1)), MHB, PHB (0.4-1.2?gmL(-1)) and PD1 (2.5-100?gmL(-1)); the precision, determined in terms of intra-day and inter-day precision, expressed as RSDs, were in the ranges 0.4-1.2 and 0.7-1.4, respectively. The method demonstrated to be accurate and robust; indeed the average recoveries were 100.2, 99.9, and 100.0% for PAN, MHB and PHB, respectively, and 99.9% for PD1. By applying small variations of the mobile phase composition, counter-ion concentration and pH the separation of analytes was not affected. Finally, the applicability of this method was evaluated analyzing the available commercial forms at release as well as during stability studies. PMID:24863372

Canavesi, Rossana; Aprile, Silvio; Varese, Elena; Grosa, Giorgio

2014-08-01

246

Determination of lumiracoxib by a validated stability-indicating MEKC method and identification of its degradation products by LC-ESI-MS studies.  

PubMed

A stability-indicating MEKC method was developed and validated for the analysis of lumiracoxib (LMC) in pharmaceutical formulations using nimesulide as the internal standard (IS). Optimal conditions for the separation of LMC and degradation products were investigated. The method employed 50?mM borate buffer and 50?mM anionic detergent SDS solution at pH 9.0. MEKC method was performed on a fused-silica capillary (50??m id; effective length, 40?cm) maintained at 30°C. The applied voltage was 20?kV and photodiode array (PDA) detector was set at 208?nm. The method was validated in accordance with the International Conference on Harmonisation requirements. The stability-indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using PDA detection. The degradation products formed under stressed conditions were investigated by LC-ESI-MS and the two degraded products were identified. MEKC method was linear over the concentration range of 5-150??g/mL (r(2) =0.9999) of LMC. The method was precise, accurate, with LOD and LOQ of 1.34 and 4.48??g/mL, respectively. The robustness was proved by a fractional factorial design evaluation. The proposed MEKC method was successfully applied for the quantitative analysis of LMC in tablets to support the quality control. PMID:21688392

Sangoi, Maximiliano S; Wrasse-Sangoi, Micheli; Oliveira, Paulo R; Bernardi, Larissa S

2011-08-01

247

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. PMID:23264939

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

2012-01-01

248

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. PMID:24106670

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

2013-01-01

249

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. PMID:21886901

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

2011-01-01

250

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

2013-01-01

251

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

252

A stability-indicating, ion-pairing, reversed-phase liquid chromatography method for studies of daunorubicin degradation in i.v. infusion fluids.  

PubMed

A new stability-indicating method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the quantification of daunorubicin. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 ?m (150 mm × 4.6 mm). The mobile phase was 6.2mM nonafluoropentanoic acid in aqueous solution and acetonitrile under isocratic elution mode. The drug was subjected to oxidation, basic and acid hydrolysis to apply stress conditions. Good resolution was achieved between daunorubicin, related products and all degradation products in an overall analytical run time of approximately 16 min with the parent compound daunorubicin eluting at approximately 8 min. The method was fully validated according to ICH guidelines and SFSTP protocols in terms of accuracy, precision, specificity and linearity. For daunorubicin, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains daunorubicin (0.25-0.45 mg/mL) and shown to provide a very effective method. Physical and chemical stability study was carried out on daunorubicin preparation in our hospital centralized pharmacy unit. PMID:23747490

Respaud, R; Quenum, L; Plichon, C; Tournamille, J F; Gyan, E; Antier, D; Viaud-Massuard, M C

2013-09-01

253

A Validated Stability-indicating Reverse Phase HPLC Assay Method for the Determination of Memantine Hydrochloride Drug Substance with UV-Detection Using Precolumn Derivatization Technique  

PubMed Central

This present paper deals with the development and validation of a stability indicating high performance liquid chromatographic method for the quantitative determination of Memantine hydrochloride. Memantine hydrochloride was derivatized with 0.015 M 9-fluorenylmethyl chloroformate (FMOC) and 0.5 M borate buffer solution by keeping it at room temperature for about 20 minutes and the chromatographic separation achieved by injecting 10 ?L of the derivatized mixture into a Waters HPLC system with photodiode array detector using a kromasil C18 column (150 × 4.6 mm), 5 ?. The mobile phase consisting of 80% acetonitrile and 20% phosphate buffer solution and a flow rate of 2 milliliter/minute. The Memantine was eluted at approximately 7.5 minutes. The volume of FMOC used in derivatization, concentration of FMOC and derivatization time was optimized and used. Forced degradation studies were performed on bulk sample of Memantine hydrochloride using acid (5.0 Normal (N) hydrochloric acid), base (1.0 N sodium hydroxide), oxidation (30% hydrogen peroxide), thermal (105°C), photolytic and humidity conditions. The developed LC method was validated with respect to specificity, precision (% RSD about 0.70%), linearity (linearity of range about 70–130 ?g/mL), ruggedness (Overall % RSD about 0.35%), stability in analytical solution (Cumulative % RSD about 0.11% after 1450 min.) and robustness. PMID:20703320

Narola, Bhavil; Singh, A.S.; Santhakumar, P. Rita; Chandrashekhar, T.G.

2010-01-01

254

A comparative study between three stability indicating spectrophotometric methods for the determination of diatrizoate sodium in presence of its cytotoxic degradation product based on two-wavelength selection.  

PubMed

Three sensitive, selective, and precise stability indicating spectrophotometric methods for the determination of the X-ray contrast agent, diatrizoate sodium (DTA) in the presence of its acidic degradation product (highly cytotoxic 3,5-diamino metabolite) and in pharmaceutical formulation, were developed and validated. The first method is ratio difference, the second one is the bivariate method, and the third one is the dual wavelength method. The calibration curves for the three proposed methods are linear over a concentration range of 2-24?g/mL. The selectivity of the proposed methods was tested using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives. The results were statistically compared with the official US pharmacopeial method. No significant difference for either accuracy or precision was observed. PMID:25791882

Riad, Safaa M; El-Rahman, Mohamed K Abd; Fawaz, Esraa M; Shehata, Mostafa A

2015-06-15

255

A novel validated stability indicating high performance liquid chromatographic method for estimation of degradation behavior of ciprofloxacin and tinidazole in solid oral dosage  

PubMed Central

Objective: The objective of current investigation was to study the degradation behavior of Ciprofloxacin and Tinidazole. The study was performed as per International Conference on Harmonization recommended stress condition. A novel stability-indicating reverse phase HPLC method was developed for the determination of Ciprofloxacin and Tinidazole purity in the presence of its impurities and forced degradation products. This method is also capable to separate placebo peaks as well in pharmaceutical dosage forms. The solid oral dosage form was subjected to the stress conditions such as oxidative, acid, base hydrolysis, heat and photolytic degradation. Materials and Methods: The method was developed using Waters symmetry shield, Reverse Phase (RP) C18, 250mm x 4.6mm, 5? as a stationary phase. The mobile phase containing a gradient mixture of solvent A and B. 10mM phosphate buffer, adjusted pH 3.0 with phosphoric acid was used as a buffer. Buffer pH 3.0 was used as solvent A and buffer pH 3.0: Acetonitrile in the ratio of 20: 80 v/v were used as solvent B. The eluted compounds were monitored 278 nm (Ciprofloxacin), 317 nm (Tinidazole). The run time was 50 minute. Results: In the precision study the % RSD for the result of Ciprofloxacin, Tinidazole and its impurities was below 10%. The method was linear with the correlation coefficient greater than 0.997. The percentage recoveries were calculated and observed from 93.0% to 106.7%. The peak purity of Ciprofloxacin, Tinidazole peak had not shown any flag, thus proved the stability-indicating power of the method. Conclusion: 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:24302838

Vaghela, Bhupendrasinh K.; Rao, Surendra Singh

2013-01-01

256

Stability indicating LC method for rapid determination of related substances of O-desmethyl venlafaxine in active pharmaceutical ingredients and pharmaceutical formulations.  

PubMed

A simple, precise and accurate stability-indicating reversed phase-high performance liquid chromatography method was developed for the quantitative determination of O-desmethyl venlafaxine (ODV) and its related substances in active pharmaceutical ingredient and pharmaceutical formulation. The method was developed using YMC-pack ODS-A (150 × 4.6 mm, 3 ?m) column with mobile phase containing a gradient mixture of solvents A and B. Solvent A contained a mixture of buffer and acetonitrile in the ratio of 85:15 (v/v). The buffer consisted of 10 mM potassium dihydrogen phosphate and 2 mM 1-octane sulfonic acid sodium salt (pH adjusted to 6.0 by using diluted potassium hydroxide solution). Solvent B contained a mixture of water and acetonitrile in the ratio of 20:80 (v/v). The eluted compounds were monitored at 230 nm. ODV and its six impurities were well separated within 14 min run time. It was subjected under the stress conditions of oxidative, acid, base, water, thermal and photolytic degradation. It was sensitive towards acidic, basic, oxidative and water stress conditions, stable in photolytic and thermal degradation conditions. The degradation products were well resolved from main peak and its impurities, the mass balance in each case was >99.0%, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to its specificity, linearity (correlation coefficient >0.9996), limit of detection, limit of quantification, accuracy (recovery range 97.1-103.2%), precision (% relative standard deviation ?1.9%) and robustness. PMID:24474426

Rao, Karri Visweswara; Reddy, Kesareddy Padmaja; Kumar, Yelavarthi Ravindra

2014-01-01

257

Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules  

NASA Astrophysics Data System (ADS)

Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40 °C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080 ± 0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (?max: 520 nm) or amaranth dye (?max: 530 nm). The reacted oxidant corresponds to the drug content. Beer’s law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 ?g mL-1 for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 ?g mL-1 and 0.782, 0.973 and 0.376 ?g mL-1 for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them.

Gouda, Ayman A.; Hashem, Hisham; Jira, Thomas

2014-09-01

258

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

2012-11-15

259

Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules.  

PubMed

Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40°C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080±0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (?max: 520 nm) or amaranth dye (?max: 530 nm). The reacted oxidant corresponds to the drug content. Beer's law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 ?g mL(-1) for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 ?g mL(-1) and 0.782, 0.973 and 0.376 ?g mL(-1) for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them. PMID:24813276

Gouda, Ayman A; Hashem, Hisham; Jira, Thomas

2014-09-15

260

Synthesis and identification of the primary degradation product in a commercial ophthalmic formulation using NMR, MS, and a stability-indicating HPLC method for antazoline and naphazoline.  

PubMed

HPLC analysis of an anti-infective ophthalmic solution (Albalon-A), containing the active drugs naphazoline and antazoline, revealed a degradation peak of unknown identity. To elucidate the identity of the degradant, the active drugs were each hydrolyzed by refluxing at high pH, and their respective hydrolysis products were isolated and spectrally characterized by NMR, FT-IR, and MS for conclusive structure elucidation. The degradant's identity was confirmed by HPLC-MS analysis of Albalon-A ophthalmic solution to be the antazoline hydrolysis product N-[(N-benzylanilino)acetyl]ethylenediamine (IV). A stability-indicating HPLC method was then developed which was able to resolve IV from the active drugs. This HPLC method was then validated for quantitating the active drugs and IV. Validation studies demonstrated linear UV response at 280 nm, recovery > 98%, good reproducibility, and a detection limit of 2 micrograms/mL IV. Overall, the data demonstrated that the HPLC method was quantitative and specific for antazoline, naphazoline, and IV. Analysis of an expired stabilitry lot of the ophthalmic solution indicated the concentration of IV was 0.002% (w/v). PMID:7629745

Ruckmick, S C; Marsh, D F; Duong, S T

1995-04-01

261

Longitudinal stability of social competence indicators in a Portuguese sample: Q-sort profiles of social competence, measures of social engagement, and peer sociometric acceptance.  

PubMed

This study examines the temporal stability (over 3 years) of individual differences in 3 domains relevant to preschool children's social competence: social engagement/motivation, profiles of behavior and personality attributes characteristic of socially competent young children, and peer acceptance. Each domain was measured with multiple indicators. Sociometric status categories (Asher & Dodge, 1986) and reciprocated friendships were derived from sociometric data. Composites for social competence domains were significantly associated across all time points. Within age-periods, social competence domains were associated with both sociometric and friendship status categories; however, neither sociometric status nor reciprocated friendships were stable over time. Nevertheless, analyses examining the social competence antecedents to reciprocated friendship at age-4 and age-5 suggested that more socially competent children in the prior year were more likely to have a reciprocated friendship in the current year. Popular and rejected sociometric status categories were also associated with social competence indicators in prior years, but this was most clearly seen at age-5. PMID:24015691

Santos, António J; Vaughn, Brian E; Peceguina, Inês; Daniel, João R

2014-03-01

262

A new, rapid, stability-indicating UPLC method for separation and determination of impurities in amlodipine besylate, valsartan and hydrochlorothiazide in their combined tablet dosage form.  

PubMed

A new rapid stability-indicating UPLC method for separation and determination of impurities in amlodipine besylate, valsartan and hydrochlorothiazide in their combined tablet dosage form was developed. The separation of Ph. Eur. related substances of amlodipine besylate (A, B, D, E, F, G), hydrochlorothiazide (A, B, C), valsartan (B, C), two other valsartan impurities (S)-2-(N-{[2'-cyanobiphenyl-4-yl]methyl}pentanamido)-3-methylbutanoic acid and (S)-3-methyl-2-{[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methylamino}butanoic acid and several unknown impurities was achieved by reversed phase liquid chromatography with UV detection. The detection wavelengths were set as follows: 225nm for valsartan, its impurities and for the impurity D of amlodipine, 271nm for hydrochlorothiazide and its impurities and 360nm for amlodipine and its impurities except for impurity D. Zorbax Eclipse C8 RRHD (100mm×3.0mm, 1.8?m) was used as a separation column and the analytes were eluted within 11min by a programmed gradient mixture of 0.01M phosphate buffer pH 2.5 and acetonitrile. The method was successfully validated in accordance to the International Conference of Harmonization (ICH) guidelines for amlodipine besylate and its impurity D, valsartan and its impurity C and hydrochlorothiazide and its impurities A, B and C. The triple-combined tablets were exposed to thermal, higher humidity, acid, alkaline, oxidative and photolytic stress conditions. Stressed samples were analyzed by the proposed method. All the significant degradation products and impurities were satisfactory separated from each other and from the principal peaks of drug substances. The peak purity test complied for peaks of amlodipine, valsartan and hydrochlorothiazide in all the stressed samples and indicated no co-elution of degradation products. The method was found to be precise, linear, accurate, sensitive, specific, robust and stability-indicating and could be used as a routine purity test method for amlodipine besylate, valsartan, hydrochlorothiazide and their pharmaceutical combinations. PMID:25756663

Vojta, Ji?í; Jedli?ka, Aleš; Coufal, Pavel; Jane?ková, Lucie

2015-05-10

263

A rapid stability-indicating, fused-core HPLC method for simultaneous determination of ?-artemether and lumefantrine in anti-malarial fixed dose combination products  

PubMed Central

Background Artemisinin-based fixed dose combination (FDC) products are recommended by World Health Organization (WHO) as a first-line treatment. However, the current artemisinin FDC products, such as ?-artemether and lumefantrine, are inherently unstable and require controlled distribution and storage conditions, which are not always available in resource-limited settings. Moreover, quality control is hampered by lack of suitable analytical methods. Thus, there is a need for a rapid and simple, but stability-indicating method for the simultaneous assay of ?-artemether and lumefantrine FDC products. Methods Three reversed-phase fused-core HPLC columns (Halo RP-Amide, Halo C18 and Halo Phenyl-hexyl), all thermostated at 30°C, were evaluated. ?-artemether and lumefantrine (unstressed and stressed), and reference-related impurities were injected and chromatographic parameters were assessed. Optimal chromatographic parameters were obtained using Halo RP-Amide column and an isocratic mobile phase composed of acetonitrile and 1mM phosphate buffer pH 3.0 (52:48; V/V) at a flow of 1.0 ml/min and 3 ?l injection volume. Quantification was performed at 210 nm and 335 nm for ?-artemether and for lumefantrine, respectively. In-silico toxicological evaluation of the related impurities was made using Derek Nexus v2.0®. Results Both ?-artemether and lumefantrine were separated from each other as well as from the specified and unspecified related impurities including degradants. A complete chromatographic run only took four minutes. Evaluation of the method, including a Plackett-Burman robustness verification within analytical QbD-principles, and real-life samples showed the method is suitable for quantitative assay purposes of both active pharmaceutical ingredients, with a mean recovery relative standard deviation (± RSD) of 99.7 % (± 0.7%) for ?-artemether and 99.7 % (± 0.6%) for lumefantrine. All identified ?-artemether-related impurities were predicted in Derek Nexus v2.0® to have toxicity risks similar to ?-artemether active pharmaceutical ingredient (API) itself. Conclusions A rapid, robust, precise and accurate stability-indicating, quantitative fused-core isocratic HPLC method was developed for simultaneous assay of ?-artemether and lumefantrine. This method can be applied in the routine regulatory quality control of FDC products. The in-silico toxicological investigation using Derek Nexus® indicated that the overall toxicity risk for ?-artemether-related impurities is comparable to that of ?-artemether API. PMID:23631682

2013-01-01

264

A new lignan from the Jian-er syrup and its content determination by RP-HPLC  

Microsoft Academic Search

The Jian-er syrup is a commonly used traditional Chinese medicinal preparation refined from two herbs, Metaplexis japonica (Thunb.) Makino and Justicia procumbens L. A new lignan, named 6?-hydroxy-Justicidin B, was isolated from the ethyl acetate extract of the Jian-er syrup and its structure was established on the basis of spectral analysis. The content of 6?-hydroxy-Justicidin B in the Jian-er syrup

Meihua Yang; Jun Wu; Xudong Xu; Yue Jin; Yi Guo; Jianmin Chen

2006-01-01

265

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

266

Determination of Partition Coefficients of 2Amino2-Oxazolines by RP-HPLC: Application to Hydrophobicity Studies  

Microsoft Academic Search

A comparative study of the hydrophobicity for a series of bioactive 5-aryloxy-methyl-2-amino-2-oxazolines is reported. Octanol-water partition coefficients were measured using the classical shake-flask method. For two lipophilic compounds, high-performance liquid chromatography (HPLC) was used as a detector for the shake-flask method. The capacity factors (log k') were determined by an HPLC method using methanol-water as a mobile phase and a

J. Thomas; O. Adetchessi; F. Pehourcq; P. Dallet; C. Jarry

1997-01-01

267

Octadecyl, Phenyl and Cyano Phases Comparison for the RP-HPLC Prediction of Octanol-Water Partition Coefficient  

Microsoft Academic Search

On phenyl and cyano phases log k' values were determined, for a series of benzodiazepines. The log k' values linearly extrapolated at 100% water were highly significantly correlated to log P values.A comparison with the most commonly used octadecyl phase demonstrates that phenyl is the best phase for log P prediction, cyano the most sensitive to the presence of particular

M. C. Pietrogrande; F. Dondi; G. Blo; P. A. Borea; C. Bighi

1987-01-01

268

Identification and Quantification of Trans-Resveratrol in Dietary Supplements by a Rapid and Straightforward RP-HPLC Method  

Microsoft Academic Search

This paper reports the results of a study performed to develop a rapid and straightforward chromatographic method for the identification and quantification of trans-resveratrol in commercial trans-resveratrol containing dietary supplements. The method employs an Alltech Platinum EPS 100 A C-18 column operated under isocratic elution mode with a 70:30 (v\\/v) water-acetonitrile mixture as the mobile phase, at flow rate of

Antonella Brizzi; Vittorio Brizzi; Danilo Corradini

2008-01-01

269

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...

270

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

271

Simplified RP-HPLC method for multi-residue analysis of abamectin, emamectin benzoate and ivermectin in rice.  

PubMed

A rapid, reliable and sensitive reverse-phase high-performance liquid chromatography method with fluorescence detection (RP-FLD-HPLC) was developed and validated for simultaneous analysis of the abamectin (ABA), emamectin (EMA) benzoate and ivermectin (IVM) residues in rice. After extraction with acetonitrile/water (2 : 1) with sonication, the avermectin (AVMs) residues were directly derivatised by N-methylimidazole (N-NMIM) and trifluoroacetic anhydride (TFAA) and then analysed on RP-FLD-HPLC. A good linear relationship (r(2 )> 0.99) was obtained for three AVMs ranging from 0.01 to 5 microg ml(-1), i.e. 0.01-5.0 microg g(-1) in rice matrix. The limit of detection (LOD) and the limit of quantification (LOQ) were between 0.001 and 0.002 microg g(-1) and between 0.004 and 0.006 microg g(-1), respectively. Recoveries were from 81.9% to 105.4% and precision less than 12.4%. The proposed method was successfully applied to routine analysis of the AVMs residues in rice. PMID:21132591

Xie, Xianchuan; Gong, Shu; Wang, Xiaorong; Wu, Yinxing; Zhao, Li

2011-01-01

272

Simultaneous RP-HPLC-DAD separation, and determination of flavonoids and phenolic acids in Plantago L. species.  

PubMed

A rapid reversed-phase (RP) high-performance liquid chromatography method was developed and applied for simultaneous separation, and determination of flavonoids and phenolic acids in eight Plantago L. taxa (P. altissima L., P. argentea Chaix, P. coronopus L., P. holosteum Scop. ssp. depauperata Pilger, P. holosteum ssp. holosteum, P. holosteum ssp. scopulorum (Degen) Horvati?, P. lagopus L., and P. maritima L.) growing in Croatia. Chromatographic separation was carried out on Zorbax Eclipse XDB-C18 using gradient elution with a H2 O (pH?2.5, adjusted with CF3 COOH) and MeCN mixture at 30°. The contents of analyzed phenolic compounds (% of the dry weight of the leaves, dw) varied among examined species: rutin (max. 0.024%, P. argentea), hyperoside (max. 0.020%, P. lagopus), quercitrin (max. 0.013%, P. holosteum ssp. holosteum), quercetin (max. 0.028%, P. holosteum ssp. scopulorum), chlorogenic acid (max. 0.115%, P. lagopus), and caffeic acid (max. 0.046%, P. coronopus). Isoquercitrin was detected only in P. argentea (0.020%), while isochlorogenic acid content was below limit of quantification in all investigated species. Multivariate analyses (UPGMA and PCA) showed significant differences in contents of investigated polyphenolic compounds between different Plantago taxa. Accordingly, investigated substances might be employed as chemotaxonomic markers in the study of the complex genus Plantago. PMID:23847075

Juriši? Grubeši?, Renata; Sre?nik, Goran; Kremer, Dario; Vukovi? Rodríguez, Jadranka; Nikoli?, Toni; Vladimir-Kneževi?, Sanda

2013-07-01

273

Simultaneous Determination of Ofloxacin and Ornidazole in Solid Dosage Form by RP-HPLC and HPTLC Techniques  

PubMed Central

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 C18 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 60F254 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 Rf 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.

2010-01-01

274

Development and Validation of RP-HPLC Method for Simultaneous Estimation of Cefpodoxime Proxetil and Dicloxacillin Sodium in Tablets  

PubMed Central

A simple, accurate, rapid and precise reversed-phase high-performance liquid chromatographic method has been developed and validated for simultaneous determination of cefpodoxime proxetil and dicloxacillin sodium in tablet. The chromatographic separation was carried out on kromasil C18 analytical column (250×4.6 mm; 5 ?m) with a mixture of acetonitrile:methanol:trifloroacetic acid (0.001%) with pH 6.5 (30:50:20, v/v/v) as mobile phase; at a flow rate of 1.0 ml/min. UV detection was performed at 235 nm. The dicloxacillin sodium and cefpodoxime proxetil were eluted at 1.92 and 3.35 min, respectively. The peaks were eluted with better resolution. Calibration plots were linear over the concentration range 0.5-20 ?g/ml for cefpodoxime proxetil (r2=0.9996) and 5-50 ?g/ml for dicloxacillin sodium (r2=0.9987). The method was validated for accuracy, precision, linearity and specificity. The method was very sensitive with limit of detection 0.0726, 0.3685 ?g/ml and limit of quantification 0.220, 1.116 ?g/ml for cefpodoxime proxetil and dicloxacillin sodium, respectively. The high recovery and low relative standard deviation confirm the suitability of the method for routine determination of cefpodoxime proxetil and dicloxacillin sodium in bulk drug and tablet dosage form. PMID:23901158

Acharya, D. R.; Patel, Dipti B.

2013-01-01

275

Development and Validation of RP-HPLC Method for Simultaneous Estimation of Cefpodoxime Proxetil and Dicloxacillin Sodium in Tablets.  

PubMed

A simple, accurate, rapid and precise reversed-phase high-performance liquid chromatographic method has been developed and validated for simultaneous determination of cefpodoxime proxetil and dicloxacillin sodium in tablet. The chromatographic separation was carried out on kromasil C18 analytical column (250×4.6 mm; 5 ?m) with a mixture of acetonitrile:methanol:trifloroacetic acid (0.001%) with pH 6.5 (30:50:20, v/v/v) as mobile phase; at a flow rate of 1.0 ml/min. UV detection was performed at 235 nm. The dicloxacillin sodium and cefpodoxime proxetil were eluted at 1.92 and 3.35 min, respectively. The peaks were eluted with better resolution. Calibration plots were linear over the concentration range 0.5-20 ?g/ml for cefpodoxime proxetil (r(2)=0.9996) and 5-50 ?g/ml for dicloxacillin sodium (r(2)=0.9987). The method was validated for accuracy, precision, linearity and specificity. The method was very sensitive with limit of detection 0.0726, 0.3685 ?g/ml and limit of quantification 0.220, 1.116 ?g/ml for cefpodoxime proxetil and dicloxacillin sodium, respectively. The high recovery and low relative standard deviation confirm the suitability of the method for routine determination of cefpodoxime proxetil and dicloxacillin sodium in bulk drug and tablet dosage form. PMID:23901158

Acharya, D R; Patel, Dipti B

2013-01-01

276

Determination of underivatized long chain fatty acids using RP-HPLC with capacitively coupled contactless conductivity detection.  

PubMed

A reversed-phase high-performance liquid chromatographic method with capacitively coupled contactless conductivity detector (C(4)D) has been developed for the separation and the simultaneous determination of five underivatized long chain fatty acids (FAs), namely myristic, palmitic, stearic, oleic, and linoleic acids. An isocratic elution mode using methanol/1mM sodium acetate (78:22, v/v) as mobile phase with a flow rate of 0.6 mL min(-1) was used. The separation was effected by using a Hypersil ODS C(18) analytical column (250 mm x 4.6 mm x 5 microm) and was operated at 45 degrees C. Calibration curves of the five FAs were well correlated (r(2)>0.999) within the range of 5- 200 microg mL(-1) for stearic acid, and 2-200 microg mL(-1) for the other FAs. The proposed method was tested on four vegetable oils, i.e., pumpkin, soybean, rice bran and palm olein oils; good agreement was found with the standard gas chromatographic (GC) method. The proposed method offers distinct advantages over the official GC method, especially in terms of simplicity, faster separation times and sensitivity. PMID:20188881

Makahleh, Ahmad; Saad, Bahruddin; Siang, Gan Hui; Saleh, Muhammad Idiris; Osman, Hasnah; Salleh, Baharuddin

2010-04-15

277

Development and validation of an ion-pair RP-HPLC method for the determination of oligopeptide-20 in cosmeceuticals.  

PubMed

Oligopeptide-20 is a growth-factor mimicking peptide used in cosmeceuticals. This article describes the development and validation of an ion-pair reversed-phase liquid chromatography method that allows, after liquid-liquid extraction, the quantification of oligopeptide-20 in cosmetic creams. Chromatographic separation was achieved on a cyanopropyl Hypersil analytical column (100 mm × 2.1 mm i.d., 5 ?m particle size), using a mobile phase of acetonitrile-heptafluorobutyric acid (pH=2.5, 9.0 mM) (70:30, v/v) containing 0.045% diethylamine at a flow rate of 0.50 mL min(-1). Ultraviolet (UV) spectrophotometric detection at 225 nm was used. The method had linear calibration curve over the range 1.35-4.95 ?g mL(-1) for oligopeptide-20. The intra- and inter-day RSD values were less than 3.3%, while the relative percentage error, %E(r), was less than 1.9. The developed method was applied successfully to the quality control of a cosmetic cream containing 0.003% (w/w) oligopeptide-20. PMID:21795001

Papagianni, Panagiota; Varvaresou, Athanasia; Papageorgiou, Spyros; Panderi, Irene

2011-11-01

278

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

2011-09-01

279

Multivariate optimization and validation of an analytical methodology by RP-HPLC for the determination of losartan potassium in capsules  

Microsoft Academic Search

This paper describes the optimization and validation of an analytical methodology for the determination of losartan potassium in capsules by HPLC using 25-1 fractional factorial and Doehlert designs. This multivariate approach allows a considerable improvement in chromatographic performance using fewer experiments, without additional cost for columns or other equipment. The HPLC method utilized potassium phosphate buffer (pH 6.2; 58mmolL?1)–acetonitrile (65:35,

Rudy Bonfilio; César Ricardo Teixeira Tarley; Gislaine Ribeiro Pereira; Hérida Regina Nunes Salgado; Magali Benjamim de Araújo

2009-01-01

280

Development and validation of a stability-indicating HPLC-UV method for the determination of alizapride and its degradation products.  

PubMed

A stability-indicating high-performance liquid chromatography procedure has been developed for the determination of alizapride (AL) and its main degradation products alizapride carboxylic acid (AL-CA) and alizapride N-oxide (AL-NO2) in drug substance and product. The method was developed based on forced degradation data obtained by HPLC-MS analysis. Indeed AL underwent chemical degradation by acid/base catalyzed hydrolysis and oxidation the main degradation products being AL-CA and AL-NO2 respectively. The separation and quantisation were achieved on a 150-mm reverse phase column with a hydrophilic linkage between silica particles and hydrophobic alkyl chains. The mobile phase was constituted (flow rate 1.5mLmin(-1)) of eluant A: aqueous acetate buffer (pH 4.0; 20mM) and eluant B: CH(3)OH using a gradient elution and detection of analytes at 225nm. The method showed good linearity for the AL, AL-CA, AL-NO2 mixture in the 25-75, 1-15 and 1-15microgmL(-1) ranges respectively, being all the square of the correlation coefficients greater than 0.999. The precision, determined in terms of intra-day and inter-day precisions and expressed as RSDs were 0.8, 1.3 and 2.1% and 1.0, 1.7, 4.8% for AL, AL-CA and AL-NO2 respectively. The method demonstrated also to be accurate; indeed the average recoveries, at 100% and 0.2% of the target assay concentration, were 100.5, 98.6, and 96.8% for AL, AL-CA and AL-NO2 respectively. The robustness was also evaluated by variations of mobile phase composition and pH. Finally, the applicability of the method was evaluated in commercial dosage form analysis as well as in stability studies. PMID:19962264

Tamaro, Ilaria; Aprile, Silvio; Giovenzana, Giovanni B; Grosa, Giorgio

2010-04-01

281

Using an innovative Quality-by-Design approach for development of a stability indicating UHPLC method for ebastine in the API and pharmaceutical formulations.  

PubMed

A stability-indicating ultra high performance liquid chromatographic (UHPLC) method has been developed for purity testing of ebastine and its pharmaceutical formulations. Successful chromatographic separation of the API from impurities was achieved on a Waters Acquity UPLC BEH C18, 50 mm × 2.1 mm, 1.7 ?m particle size column with gradient elution of 10 mM acetate buffer pH 6.2 and a mixture of acetonitrile/2-propanol (1:1) as the mobile phase. Incorporating Quality by Design (QbD) principles to the method development approach by using the chromatography modeling software DryLab4 allows the visualization of a "Design Space", a region in which changes to method parameters will not significantly affect the results as defined in the ICH guideline Q8 (R2). A verification study demonstrated that the established model for Design Space is accurate with a relative error of prediction of only 0.6%. The method was fully validated for specificity, linearity, accuracy and precision, and robustness in compliance to the ICH guideline Q2 (R1). The method was found to be linear in the concentration range from the quantification limit (LOQ) to 125% of the specification limit for ebastine and each of the impurities with correlation coefficients of not less than 0.999. The recovery rate was between 98.15 and 100.30% for each impurity. The repeatability and intermediate precision (RSD) were less than 3.2% for ebastine and each of the impurities. The robustness of the developed method was studied by varying the six parameters: gradient time, temperature, ternary composition of the eluent, flow rate and start and end concentration of the gradient at 3 levels (+1, 0, -1). The resulting 729 experiments were performed in silico from the previously constructed model for Design Space and showed that the required resolution of 2.0 can be reached in all experiments. To prove the stability-indicating performance of the method, forced degradation (acid and base hydrolysis, oxidation, photolytic and thermal stress conditions) of ebastine was carried out. Baseline separation could be achieved for all peaks of the impurities, the degradation products and the API. Total run time was only 4 min, which is an impressive 40-fold increase in productivity in comparison to the method published in the Ph. Eur. monograph and allowed purity testing of more than 360 samples per day. PMID:23454599

Schmidt, Alexander H; Molnár, Imre

2013-05-01

282

Rapid and sensitive bioanalytical stability-indicating method for quantification of talinolol, a selective ?1 adrenoceptor antagonist in lipid based formulations using ultrafast UHPLC systems.  

PubMed

The current study evaluates the ultra high performance liquid chromatography (UHPLC) method for the quantification of talinolol in lipid-based formulations. A simple, rapid, reliable and precise reversed phase UHPLC method has been developed and validated according to the regulatory guidelines, which was composed of isocratic mobile phase; acetonitrile and phosphate buffer saline (pH 4.5) with a flow rate of 0.4 mL/min, and column HSS C18 (2.1 x 50 mm, 1.8 ?m). The detection was carried out at 245 nm. The developed UHPLC method was found to be rapid (1.8 min run time), selective with high resolution of talinolol peak (0.88 min) from different lipid matrices and highly sensitive (limit of detection and lower limit of quantification were 0.14 ppm and 0.5 ppm, respectively). The linearity, accuracy and precision were determined as acceptable over the concentration range of 0.5-100 ppm for talinolol. The results showed that the proposed UHPLC method can be used for the estimation of talinolol in lipid-based formulation by indicating its purity and stability with no interference of excipients or related substances of active pharmaceutical ingredient. PMID:25362802

Mohsin, Kazi; Al-Qahtani, Safar; Alanazi, Fars K

2014-01-01

283

Development of a stability-indicating HPLC method of Etifoxine with characterization of degradation products by LC-MS/TOF, 1H and 13C NMR.  

PubMed

This paper describes a new LC-MS/TOF method for the degradation products determination when Etifoxine (ETI) is submitted to different stress conditions. Chromatography is performed by using Kromasil C18 column (250mm×4.6mm, 5?m particle size). The selected mobile phase consists of formate buffer 0.02M, pH 3 and methanol (70/30, v/v). ETI is submitted to oxidative, acidic, basic, hydrolytic, thermal and UV light degradations. Detection is made at 254nm by photodiode array detector and mass spectrometry. A number of degradation products (DPs) called DPA, DPB, DPC and DPD are found depending on the stress; DPA with heat, DPA and DPB in acidic media or under UV-light; DPA, DPB and DPC under basic stress; DPA, DPB, DPC and DPD with oxidation. LC-MS/TOF is used to characterize the four DPs of ETI resulting from different stress conditions. (1)H and (13)C NMR are used to confirm the DP structures. The ETI fragmentation pathway is proposed. The method is validated with reference to International Conference on Harmonization guidelines and ETI are selectively determined in presence of its DPs, demonstrating its stability-indicating nature. Finally, for the validation step, specificity, linearity, accuracy and precision are determined for ETI and its DPs. PMID:25117950

Djabrouhou, Nadia; Guermouche, Moulay-Hassane

2014-11-01

284

A Single Gradient Stability-Indicating Reversed-Phase LC Method for the Estimation of Impurities in Omeprazole and Domperidone Capsules.  

PubMed

A gradient reversed-phase liquid chromatographic (RP-LC) method was developed for the quantitative estimation of impurities in the pharmaceutical dosage form of Omeprazole and Domperidone capsules. The developed method is a stability-indicating test method for the estimation of impurities generated during the formulation and storage of Omeprazole and Domperidone capsules. The chromatographic separation was achieved on a column packed with octadecyl silane, having a column length of 250 mm and diameter of 4.6 mm with a particle size of 5 ?m, and by following a gradient program using a combination of a monobasic potassium phosphate buffer (0.05M) and acetonitrile. Since the spectral properties were similar, both compounds' individual impurities were estimated at 285 nm. Forced degradation studies were performed on Omeprazole pellets (enteric coated) and Domperidone pellets (SR coated) encapsulated in size '1' hard gelatin capsules. Omeprazole and Domperidone were degraded using acid hydrolysis (0.1 N hydrochloric acid), base (0.1 N sodium hydroxide), oxidation (50% hydrogen peroxide), heat (105 °C), and UV light (254 nm). The established method was validated and found to be linear, accurate, precise, specific, robust, and rugged. PMID:23833712

Seshadri, Raja Kumar; Raghavaraju, Thummala Veera; Chakravarthy, Ivon Elisha

2013-06-01

285

Development and validation of stability-indicating high performance liquid chromatography method to analyze gatifloxacin in bulk drug and pharmaceutical preparations.  

PubMed

Quantitative determination of gatifloxacin in tablets, solid lipid nanoparticles (SLNs) and eye-drops using a very simple and rapid chromatographic technique was validated and developed. Formulations were analyzed using a reverse phase SUPELCO® 516 C-18-DB, 50306-U, HPLC column (250 mm × 4.6 mm, 5 ?m) and a mobile phase consisting of disodium hydrogen phosphate buffer:acetonitrile (75:25, v/v) and with orthophosphoric acid pH was adjusted to 3.3 The flow rate was 1.0 mL/min and analyte concentrations were measured using a UV-detector at 293 nm. The analyses were performed at room temperature (25 ± 2 °C). Gatifloxacin was separated in all the formulations within 2.767 min. There were linear calibration curves over a concentration range of 4.0-40 ?g.mL(-1) and correlation coefficients of 0.9998 with an average recovery above 99.91%. Detection of analyte from different dosage forms at the same Rt indicates the specificity and stability of the developed method. PMID:25685047

Aljuffali, Ibrahim A; Kalam, Mohd Abul; Sultana, Yasmin; Imran, Ahamad; Alshamsan, Aws

2015-01-01

286

Application of a Stability-Indicating HPTLC Method for Simultaneous Quantitative Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Pharmaceutical Dosage Forms.  

PubMed

A rapid, precise, sensitive, economical, and validated high performance thin layer chromatographic method is developed for simultaneous quantification of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage form. The method used amlodipine as internal standard (IS). Chromatographic separations were achieved on silica gel 60?F254 plates using toluene-methanol-ethyl acetate-acetone (2.5?:?1?:?0.5?:?2, v/v/v/v) as mobile phase. Densitometric analysis was carried out in the reflectance mode at 258?nm. Calibration curves were linear over a range of 80-480?ng/band for olmesartan medoxomil and 25-150?ng/band for hydrochlorothiazide. The detection and quantification limits were found to be 18.12 and 56.35?ng/band for olmesartan medoxomil and 6.31 and 18.56?ng/band for hydrochlorothiazide, respectively. Intra- and interassay precision provided relative standard deviations lower than 2% for both analytes. Recovery from 99.60 to 101.22% for olmesartan medoxomil and 98.30 to 99.32% for hydrochlorothiazide show good accuracy. Both the drugs were also subjected to acid, alkali, oxidation, heat, and photodegradation studies. The degradation products obtained were well resolved from pure drugs with significantly different R f values. As the method could effectively separate the drugs from their degradation products, it can be used for stability-indicating analysis. Validation of the method was carried out as per international conference on harmonization (ICH) guidelines. PMID:24319604

Ilango, Kaliappan; Shiji Kumar, Pushpangadhan S

2013-01-01

287

Development and validation of stability-indicating high performance liquid chromatography method to analyze gatifloxacin in bulk drug and pharmaceutical preparations  

PubMed Central

Quantitative determination of gatifloxacin in tablets, solid lipid nanoparticles (SLNs) and eye-drops using a very simple and rapid chromatographic technique was validated and developed. Formulations were analyzed using a reverse phase SUPELCO® 516 C-18-DB, 50306-U, HPLC column (250 mm × 4.6 mm, 5 ?m) and a mobile phase consisting of disodium hydrogen phosphate buffer:acetonitrile (75:25, v/v) and with orthophosphoric acid pH was adjusted to 3.3 The flow rate was 1.0 mL/min and analyte concentrations were measured using a UV-detector at 293 nm. The analyses were performed at room temperature (25 ± 2 °C). Gatifloxacin was separated in all the formulations within 2.767 min. There were linear calibration curves over a concentration range of 4.0–40 ?g.mL?1 and correlation coefficients of 0.9998 with an average recovery above 99.91%. Detection of analyte from different dosage forms at the same Rt indicates the specificity and stability of the developed method. PMID:25685047

Aljuffali, Ibrahim A.; Kalam, Mohd. Abul; Sultana, Yasmin; Imran, Ahamad; Alshamsan, Aws

2014-01-01

288

Validated stability-indicating liquid chromatographic method for the determination of ribavirin in the presence of its degradation products: application to degradation kinetics.  

PubMed

Ribavirin was found to be liable to acidic, alkaline, oxidative and photolytic degradation. Hence, a simple, sensitive and stability-indicating reversed-phase liquid chromatographic method was developed and validated for the determination of ribavirin in the presence of its degradation products. The analysis was carried out on an ODS C18 (250 × 4.6 mm i.d.) stainless steel column using a mobile phase consisting of 0.02 M potassium dihydrogen phosphate. The analysis was performed at ambient temperature with a flow rate of 1 mL/min and UV detection at 207 nm. Pyridoxine hydrochloride was used as an internal standard. The method showed good linearity over the concentration range of 2.0-40 µg/mL with limit of detection of 0.34 µg/mL and limit of quantification of 1.03 µg/mL. The suggested method was successfully applied for the analysis of ribavirin in its commercial capsules. Statistical evaluation and comparison of the data obtained by the proposed and comparison method revealed good accuracy and precision of the proposed method. The drug was exposed to forced alkaline, acidic, oxidative and photolytic degradation according to the ICH guidelines. Moreover, the method was utilized to investigate the kinetics of alkaline and acidic degradation of the drug. The apparent first-order rate constants, half-life times and activation energies of the degradation process were calculated. PMID:25092904

Belal, Fathalla; Sharaf El-Din, Mohie K; Eid, Manal I; El-Gamal, Rania M

2015-04-01

289

Stability-Indicating Liquid Chromatographic Method for Determination of Saxagliptin and Structure Elucidation of the Major Degradation Products Using LC-MS.  

PubMed

A new, simple, selective, reproducible and sensitive stability-indicating liquid chromatographic method was developed and subsequently validated for the determination of saxagliptin (SXG). SXG was subjected to oxidation, thermal, acid hydrolysis, alkali hydrolysis and photodegradation according to ICH guidelines. The major degradation products were separated from the pure drug and the proposed structures' elucidation was performed, using an LC-MS technique. Isocratic chromatographic elution was achieved on a Symmetry(®) C18 column (150 × 4.6 mm, 5 µm), using a mobile phase of potassium dihydrogen phosphate buffer (pH 4.6)-acetonitrile-methanol (40 : 30 : 30, v/v/v) at a flow rate of 1 mL min(-1) with UV detection at 208 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 25-400 µg mL(-1). All the results were statistically compared with the reference method, using one-way analysis of variance. The developed method was validated and proved to be specific and accurate for quality control of SXG in pharmaceutical dosage form. PMID:25060753

Abdel-Ghany, Maha F; Abdel-Aziz, Omar; Ayad, Miriam F; Tadros, Mariam M

2015-04-01

290

Application of a Stability-Indicating HPTLC Method for Simultaneous Quantitative Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Pharmaceutical Dosage Forms  

PubMed Central

A rapid, precise, sensitive, economical, and validated high performance thin layer chromatographic method is developed for simultaneous quantification of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage form. The method used amlodipine as internal standard (IS). Chromatographic separations were achieved on silica gel 60?F254 plates using toluene-methanol-ethyl acetate-acetone (2.5?:?1?:?0.5?:?2, v/v/v/v) as mobile phase. Densitometric analysis was carried out in the reflectance mode at 258?nm. Calibration curves were linear over a range of 80–480?ng/band for olmesartan medoxomil and 25–150?ng/band for hydrochlorothiazide. The detection and quantification limits were found to be 18.12 and 56.35?ng/band for olmesartan medoxomil and 6.31 and 18.56?ng/band for hydrochlorothiazide, respectively. Intra- and interassay precision provided relative standard deviations lower than 2% for both analytes. Recovery from 99.60 to 101.22% for olmesartan medoxomil and 98.30 to 99.32% for hydrochlorothiazide show good accuracy. Both the drugs were also subjected to acid, alkali, oxidation, heat, and photodegradation studies. The degradation products obtained were well resolved from pure drugs with significantly different Rf values. As the method could effectively separate the drugs from their degradation products, it can be used for stability-indicating analysis. Validation of the method was carried out as per international conference on harmonization (ICH) guidelines. PMID:24319604

Ilango, Kaliappan; Shiji Kumar, Pushpangadhan S.

2013-01-01

291

Development and Validation of a Stability-Indicating RP-UPLC Method for Determination of Cloxacillin Sodium in Its Bulk Form and Formulation.  

PubMed

A simple, linear gradient, rapid, precise and stability-indicating RP-UPLC method was developed for the determination of Cloxacillin Sodium in its bulk form and formulation. Ultra performance liquid chromatography, a most promising advancement in a world of chromatography, reduces analysis time, increases reliability through higher resolution, sensitivity and selectivity as well as used as an economic method due to reducing solvent consumption. A chromatographic separation of a drug as well as its degradants was achieved using Waters acquity BEH, 2.1 × 100 mm, 1.7 ?m C18 column with gradient of mobile phase A: phosphate buffer, pH 6.8 and mobile phase B: methanol:acetonitrile (75:25). The drug and degradants were monitored at a detection wavelength of 225 nm with a flow rate of 0.35 mL/min and an injection volume of 10 µL. The temperature of the column and auto sampler compartments was at 30°C and 25°C ± 1°C, respectively. The retention time of the drug was ?6.9 min. The resolution of the drug and degradant peak was >1.5 in all cases. Force degradation of CLOX SOD was carried under alkaline, acidic, oxidative, thermal, photo degradation conditions and it was analyzed by the proposed method. The drug degrades under alkaline, acidic and oxidative conditions but was stable in temperature and light. A developed method was validated as per ICH guidelines using validation parameters such as precision, linearity and range, limit of quantification, specificity, assay and robustness. PMID:25368408

Patel, Nikita; Contractor, Pooja; Keshrala, Rajesh; Patel, Parag R; Shridhar, Bhimagoni

2014-11-01

292

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). PMID:23641331

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

2013-01-01

293

Simultaneous determination of some water-soluble vitamins and preservatives in multivitamin syrup by validated stability-indicating high-performance liquid chromatography method.  

PubMed

HPLC stability-indicating method has been developed for the simultaneous determination of some water-soluble vitamins (ascorbic acid, thiamine hydrochloride, riboflavin-5'-phosphate sodium, pyridoxine hydrochloride, nicotinamide, D(+)-panthenol) and two preservatives (methylparaben and sodium benzoate) in multivitamin syrup preparation. Water-soluble vitamins, preservatives and their degradants were separated on Zorbax SB-Aq (C(18)) (250 mm x 4.6 mm, 5 microm) column at an ambient temperature. Combined isocratic and gradient elution was performed with a mobile phase consisting of 0.0125 M hexane-1-sulfonic acid sodium salt in 0.1% (m/v) o-phosphoric acid, pH 2.4-2.5 (solvent A) and acetonitrile (solvent B) at the flow-rate 1 ml min(-1). Starting with solvent A an isocratic elution was performed for 15 min, then the composition was changed to 85% of A and 15% of B during the next 20 min and it was constant for 5 min, then the composition was changed to 70% of A and 30% of B during next 15 min and it was constant for 5 min and finally was changed to 100% of A as at the beginning of the elution. Detection was performed with diode array detector at 210, 230 and 254 nm. Multivitamin syrup preparation was subjected to stress testing (forced degradation) in order to demonstrate that degradants from the vitamins, preservatives and/or product excipients do not interfere with the quantification of vitamins and preservatives. Typical validation characteristics: selectivity, accuracy, precision, linearity, range, limit of quantification and limit of detection were evaluated for vitamins and preservatives. PMID:18644604

Vidovi?, Stojanka; Stojanovi?, Biljana; Veljkovi?, Jelena; Prazi?-Arsi?, Ljiljana; Rogli?, Goran; Manojlovi?, Dragan

2008-08-22

294

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. PMID:24106669

Shaalan, Rasha A.; Belal, Tarek S.

2013-01-01

295

Selective and stability-indicating methods for the simultaneous determination of mexiletine hydrochloride and/or its related substance: 2,6-dimethylphenol.  

PubMed

Four simple, rapid, sensitive, and selective analytical procedures were developed for determination of mexiletine hydrochloride (MX) and/or its related substance: 2,6-dimethylphenol (DMP). The latter is a synthetic impurity for which a maximum pharmacopeial limit is defined. The first method depends on derivative-ratio spectrophotometry, for which the first-derivative signals of the ratio spectra at 259 nm (Deltalambda = 3 nm) are selected for the determination of MX. The second method is based on the spectrofluorometric measurement of MX in alkaline solution in the presence of 15 mM sodium dodecyl sulfate micellar medium at 292 nm (lambdaEx 260 nm). The third method is based on liquid chromatographic (LC) separation of MX and DMP on an RP-C8 column with a mobile phase consisting of 50 mM Na2HPO4-acetonitrile (60 + 40, adjusted to pH 2.4), and quantification of the analytes is achieved with UV detection at 212 nm based on peak area. The fourth method uses the coupling reaction of DMP with 2,6-dibromo-quinone-4-chlorimide (DBQC) in borate buffer to form an intensely colored product that was spectrophotometrically measured using first-derivative amplitudes at 670 nm (Deltalambda = 6 nm) for the determination of DMP. Different variables affecting each method were carefully investigated and optimized. The reliability and analytical performance of the proposed methods, including linearity, range, precision, accuracy, and detection and quantitation limits, were statistically validated. The first 3 methods were successfully applied for the stability-indicating determination of MX in laboratory-prepared mixtures with DMP, as well as for the determination of MX in capsules. Also, the LC and the DBQC spectrophotometric methods permitted the selective determination of DMP in the presence of a large excess of the parent drug at or near the pharmacopeial limit (0.1-1%). PMID:18727529

Belal, Tarek S; Haggag, Rim S; Shaalan, Rasha A

2008-01-01

296

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  

Microsoft Academic Search

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

Jun Lu; Yuchien Wei; Abu M. Rustum

2010-01-01

297

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. PMID:21617773

Nalwade, Santaji; Ranga Reddy, Vangala; Durga Rao, Dantu; Koteswara Rao, Inabathina

2011-01-01

298

Stabilization of insulin against agitation-induced aggregation by the GMO cubic phase gel.  

PubMed

The main objective of the study was to evaluate if the liquid crystalline cubic phase gel of glyceryl monooleate (GMO) protects insulin from agitation induced aggregation. The aggregation of Humulin(R), Regular Iletin I(R) and Regular Iletin II(R), in cubic phase GMO gels at 30 U/g of gel was compared with that in PBS at 100 oscillations/min at 37 degrees C using optical density at 600 nm. The effect of agitation on the secondary structure of insulin in solution and in the gels was determined with circular dichroism (CD) spectroscopy, and the time course of aggregation was also followed by HPLC. A sigmoidal increase in optical density of solution with time indicated formation of increasing amounts of insoluble insulin aggregates. However, in the gels, optical density values stayed at, or around, the initial optical density value, comparable with that of a blank gel suggesting that insulin had not aggregated in the gel. CD spectroscopy of the soluble insulin showed a total loss of native conformation upon aggregation of insulin in solution. In contrast, CD spectra of insulin in the gel were unaltered suggesting protection from aggregation during agitation. Furthermore, agitation of insulin in gels for a duration as long as 2 months at 37 degrees C, had very little adverse effect on the native conformation of insulin, as indicated by the lack of a significant change in its CD spectrum. Therefore, the cubic phase gel was indeed able to protect insulin from agitation-induced aggregation and subsequent precipitation. Although the majority of insulin in solution appeared to have aggregated and precipitated after 8 days by UV and CD spectroscopy, RP-HPLC results indicated the presence of some soluble aggregates of insulin. In summary, the liquid crystalline cubic phase gel of GMO protects peptides, like insulin, from agitation-induced aggregation. PMID:10556740

Sadhale, Y; Shah, J C

1999-11-25

299

Longitudinal Stability of Social Competence Indicators in a Portuguese Sample: Q-Sort Profiles of Social Competence, Measures of Social Engagement, and Peer Sociometric Acceptance  

ERIC Educational Resources Information Center

This study examines the temporal stability (over 3 years) of individual differences in 3 domains relevant to preschool children's social competence: social engagement/motivation, profiles of behavior and personality attributes characteristic of socially competent young children, and peer acceptance. Each domain was measured with multiple…

Santos, António J.; Vaughn, Brian E.; Peceguina, Inês; Daniel, João R.

2014-01-01

300

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

301

Integrative regulatory mapping indicates that the RNA-binding protein HuR couples pre-mRNA processing and mRNA stability.  

PubMed

RNA-binding proteins coordinate the fates of multiple RNAs, but the principles underlying these global interactions remain poorly understood. We elucidated regulatory mechanisms of the RNA-binding protein HuR, by integrating data from diverse high-throughput targeting technologies, specifically PAR-CLIP, RIP-chip, and whole-transcript expression profiling. The number of binding sites per transcript, degree of HuR association, and degree of HuR-dependent RNA stabilization were positively correlated. Pre-mRNA and mature mRNA containing both intronic and 3' UTR binding sites were more highly stabilized than transcripts with only 3' UTR or only intronic binding sites, suggesting that HuR couples pre-mRNA processing with mature mRNA stability. We also observed HuR-dependent splicing changes and substantial binding of HuR in polypyrimidine tracts of pre-mRNAs. Comparison of the spatial patterns surrounding HuR and miRNA binding sites provided functional evidence for HuR-dependent antagonism of proximal miRNA-mediated repression. We conclude that HuR coordinates gene expression outcomes at multiple interconnected steps of RNA processing. PMID:21723170

Mukherjee, Neelanjan; Corcoran, David L; Nusbaum, Jeffrey D; Reid, David W; Georgiev, Stoyan; Hafner, Markus; Ascano, Manuel; Tuschl, Thomas; Ohler, Uwe; Keene, Jack D

2011-08-01

302

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

303

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. PMID:23653862

Ozer, A. F.; Keskin, F.; Oktenoglu, T.; Suzer, T.; Ataker, Y.; Gomleksiz, C.; Sasani, M.

2013-01-01

304

Development and validation of stability indicating method for determination of sertraline following ICH guidlines and its determination in pharmaceuticals and biological fluids  

PubMed Central

Background Sertraline is a well known antidepressant drug which belongs to a class called selective serotonin reuptake inhibitor. Most published methods do not enable studying the stability of this drug in different stress conditions. Results Two new methods were developed for the determination of sertraline (SER). Both methods are based on coupling with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.8 and measuring the reaction product spectrophotometrically at 395 nm (Method I) or spectrofluorimetrically at 530 nm upon excitation at 480 nm (Method II). The response-concentration plots were rectilinear over the range 2-24 ?g/mL and 0.25-5 ?g/mL for methods I and II respectively with LOD of 0.18 ?g/mL and 0.07 ?g/mL, and LOQ of 0.56 ?g/mL and 0.21 ?g/mL for methods I and II, respectively. Conclusion Both methods were applied to the analysis of commercial tablets and the results were in good agreement with those obtained using a reference method. The fluorimetric method was further applied to the in vivo determination of SER in human plasma. A proposal of the reaction pathway was presented. The spectrophotometric method was extended to stability study of SER. The drug was exposed to alkaline, acidic, oxidative and photolytic degradation according to ICH guidelines. Moreover, the method was utilized to investigate the kinetics of oxidative degradation of the drug. The apparent first order rate constant and t1/2 of the degradation reaction were determined. PMID:21996025

2011-01-01

305

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. PMID:23833715

Talebpour, Zahra; Pourabdollahi, Hakimeh; Rafati, Hasan; Abdollahpour, Asem; Bashour, Yusef; Aboul-Enein, Hassan Y.

2013-01-01

306

Development and validation of a stability-indicating high-performance liquid chromatography method for the simultaneous determination of albuterol, budesonide, and ipratropium bromide in compounded nebulizer solutions.  

PubMed

In recent years, there has been a large increase in the use of pharmaceutical compounding to prepare medications that are not commercially available. The treatment of asthma typically includes the use of albuterol (ALB), ipratropium bromide (IPB), and/or budesonide (BUD) nebulizer solutions. There is currently no commercially available nebulizer solution containing all three of these compounds, and patients must rely on often-unregulated compounding. There is a distinct need for methodologies that can be used to analyze compounded formulations to ensure patient safety. We report an HPLC-UV method to separate and quantitate ALB, IPB, and BUD in nebulizer solutions. The method used a gradient elution to achieve separation via an RP C18 column. The method was validated, showed good selectivity, and was linear over several orders of magnitude. The method was applied to the analysis of nebulizer solutions and determination of their storage stability. Significant ALB-dependent degradation occurred within 5 h in solutions formulated with the free base of ALB, while those containing the sulfate salt of ALB produced no degradation. Alkali solutions can cause base-catalyzed hydrolysis of IPB and degradation of BUD. Compounded formulations containing ALB need to include an acid to control pH and prevent degradation. PMID:21391487

Blewett, Anthony J; Varma, Deepti; Gilles, Tiffany; Butcher, Rashidi; Jacob, Jaini; Amazan, Jean; Jansen, Susan A

2011-01-01

307

Immunolocalization of junctional proteins in human hairs indicates that the membrane complex stabilizes the inner root sheath while desmosomes contact the companion layer through specific keratins.  

PubMed

The inner root sheath (IRS) sustains and addresses the hair shaft outside the follicle. Ultrastructural analysis of immunolabeling for beta-catenin, plakophilin-1, desmoglein-4 and keratin-17 in human hairs has indicated that adherens junctions and desmosomes initially connect cells in mature IRS and the companion layer. Beta-catenin immunolabeling for adherens junctions is only seen in sparse regions of differentiating Huxley cells, Flugelzellen cells and Henle cells, but disappears in cornified cells of the IRS. Desmoglein-4 and plakophilin-1 immunolabeling are observed in differentiating and cornified desmosomes of the Huxley and Henle layers and in the membrane complex joining these cells. Desmoglein-4 and plakophilin-1 are more frequently immunolocalized in the intracellular side of the junctions, but some labeling is also present in the delta-layer of the membrane complex. The labeling indicates a prevalent intracellular redistribution of desmoglein-4 and plakophilin-1 when the final cornification of the IRS occurs. Intense keratin-17 immunolabeling is observed in tonofilaments of the companion layer joining the plakophilin-1 rich desmosomes of the Henle layer. This suggests that this elastic type of keratin is present at desmosome junctions during the movements of the companion layer along the slippage plane of the hair shaft. PMID:23312593

Alibardi, Lorenzo; Bernd, Noecker

2013-06-01

308

Capability measurement of size-exclusion chromatography with a light-scattering detection method in a stability study of bevacizumab using the process capability indices.  

PubMed

In this study, we investigated if the size-exclusion chromatography coupled with light-scattering and refractive index detection (SEC/LS/RI) method is fitted for its intended purpose and checked if the analytical method is able to provide enough conforming results. For this, the process capability indices Cp, Cpk, and Cpm were computed. The traditional X-chart and moving range (MR) chart were used by the same analyst to monitor the equipment in the laboratory over a 1-year period. For this, a bovine serum albumin (BSA) sample (0.3 mg mL(-1)) with a nominal Mw of 66.4 kDa was analyzed each working day. The results confirmed that the analytical method is in-control and stable. To determine whether the given process meets the present capability requirement and runs under the desired quality conditions, the Pearn and Shu (2003) method based on the lower confidence bound C on Cpm was used. The estimator Cpm was 1.81, and the lower confidence bound C was 1.40. We therefore conclude that the true value of the method capability Cpm is no less than 1.40 with a 95% level of confidence. This result indicates that the method is satisfactory and no stringent precision control is required. The usefulness of this method was applied in the characterization of bevacizumab commercial pharmaceutical preparations stored under different conditions that lead to aggregation. In this case, the computed Cpm index was 0.98 (0.70, 1.26), which indicates that the method does not comply with the specification limits and needs to be revised. The quality improvement effort should: (1) reduce the uncertainty in the absolute Mw determination; (2) either move the process mean closer to the target value or reduce the process variation, i.e. improve the method accuracy (?-T) and precision (?(2)). On this point, the Bayesian posterior distribution of the mean and standard deviation pointed out the need to control the precision but specially accuracy in order to reduce the overall uncertainty of analytical method and thus, the method is capable. PMID:24786652

Oliva, Alexis; Llabrés, Matías; Fariña, José B

2014-08-01

309

The "Golden Shale": An indicator of coastal stability for Marble Point, McMurdo Sound, over the last four million years  

USGS Publications Warehouse

A small sedimentary deposit near Gneiss Point on the western side of McMurdo Sound, previously identified as shale, is described. The deposit is phillipsite, a zeolite that is believed to have formed from the deposition and alteration of volcanic ash in a small ice-marginal saline lake. Other previously recorded occurrences of phillipsite in the dry valleys are believed to be several million years old. A similar age for this deposit is suggested for the Gneiss Point deposit. This is consistent with other weathering and landscape features found in the immediate area, including traces of halloysite in soils. The deposit is very close to sea level but could not have formed if the site had been below sea level, indicating that there has been very little uplift following that which caused the sea to retreat from the Wright Fiord.

Claridge, G.G.C.; Campbell, I.B.

2007-01-01

310

Degradation kinetics study of cabozantinib by a novel stability-indicating LC method and identification of its major degradation products by LC/TOF-MS and LC-MS/MS.  

PubMed

The chemical stability of cabozantinib (CBZ) was investigated using a novel stability-indicating LC method. Forced degradation of CBZ was carried out under acidic, basic, thermal, oxidative and photolytic stress conditions. Hydrolysis and oxidation were the primary pathways for this compound and three major unknown degradation products were characterized by LC/TOF-MS and LC-MS/MS. The major oxidative degradation product was isolated by preparative LC and identified by UV, HRMS and NMR techniques to be N-{4-[(N-oxide-6,7-dimethoxyquinolin-4-yl)oxy]phenyl}-N'-(4-fluorophenyl)-cyclopropane-1,1-dicarboxamide. The developed method was validated as per ICH guidelines and then successfully applied to investigate the degradation kinetics of CBZ. Degradation of CBZ followed first-order kinetics under all experimental conditions. A V-shaped pH-rate profile over the pH range 2-10 was observed with maximum stability at pH 6. The effect of temperature on the rate of CBZ degradation was characterized using the Arrhenius equation. The activation energy for hydrolysis was 57.31kJmol(-1) in alkaline solution. PMID:24992215

Wu, Chunyong; Xu, Xue; Feng, Chao; Shi, Yuanyuan; Liu, Wenyuan; Zhu, Xiaoyun; Zhang, Junying

2014-09-01

311

Complexity in estimation of esomeprazole and its related impurities' stability in various stress conditions in low-dose aspirin and esomeprazole magnesium capsules.  

PubMed

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. PMID:23833714

Reddy, Palavai Sripal; Hotha, Kishore Kumar; Sait, Shakil

2013-06-01

312

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. PMID:23833714

Reddy, Palavai Sripal; Hotha, Kishore Kumar; Sait, Shakil

2013-01-01

313

Indices To Measure Stability of Rule Application.  

ERIC Educational Resources Information Center

When learning is taking place, students test their hypotheses and evaluate them, and modify their current theories on the basis of new information. This phenomenon is known as "hypothesis testing view" or "theory changes." Many students change their rules to another while they are taking a test. This study introduced a new concept called "slip…

Tatsuoka, Kikumi K.

314

Community indicators  

PubMed Central

Community indicators are used to assess the impact of alcohol on communities. This article reviews the main data sources for community indicators, discusses their strengths and limitations, and discusses indicators used in reference to four main topics relating to alcohol use and problems at the community level: alcohol use, patterns, and problems; alcohol availability; alcohol-related health outcomes/trauma; and alcohol-related crime and enforcement. It also reviews the challenges associated with collecting community indicator data, along with important innovations in the field that have contributed to better knowledge of how to collect and analyze community-level data on the impact of alcohol. PMID:24881322

Flynn, Andrea; Wells, Samantha

2014-01-01

315

Determination of amino acid contents of manketti seeds (Schinziophyton rautanenii) by pre-column derivatisation with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and RP-HPLC.  

PubMed

Defatted kernel flour from manketti seed kernels (Schinziophyton rautanenii) is an underutilised natural product. The plant grows in the wild, on sandy soils little used for agriculture in Southern Africa. The kernels are rich in protein and have a great potential for improving nutrition. The protein content and amino acid profile of manketti seed kernel were studied, using a new analytical method, in order to evaluate the nutritional value. The crude protein content of the press cake and defatted kernel flour was 29.0% and 67.5%, respectively. Leucine and arginine were found to be the most abundant essential and non-essential amino acids, respectively. The seed kernel contained 4.77 g leucine and 12.34 g arginine/100 g of defatted seed kernel flour. Methionine and proline were the least abundant essential and non-essential amino acids to with 0.23 g methionine and 0.36 g proline/100 g of defatted seed kernel flour, respectively. Validation of the pre-column derivatisation procedure with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) for the determination of amino acids was carried out. The analytical parameters were determined: linearity (0.0025-0.20 mM), accuracy of the derivatisation procedure: 86.7-109.8%, precision (method: 0.72-5.04%, instrumental: 0.14-1.88% and derivatisation: 0.15-2.94% and 0.41-4.32% for intraday and interday, respectively). Limits of detection and quantification were 6.80-157 mg/100 g and 22.7-523 mg/100 g kernel flour, respectively. PMID:23870943

Gwatidzo, Luke; Botha, Ben M; McCrindle, Rob I

2013-12-01

316

Identification of lipopeptide isoforms by MALDI-TOF-MS/MS based on the simultaneous purification of iturin, fengycin, and surfactin by RP-HPLC.  

PubMed

A three-stage linear gradient strategy using reverse-phase high-performance liquid chromatography (HPLC) was optimized for rapid, high-quality, and simultaneous purification of the lipopeptide isoforms of iturin, fengycin, and surfactin, which may differ in composition by only a single amino acid and/or the fatty acid residue. Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) was applied to detect the lipopeptides harvested from each reversed-phase HPLC peak. Amino acid analysis based on phenyl isothiocyanate derivatization was further used for confirmation of the amino acid species and molar ratio in a certain HPLC fraction. By this MALDI-TOF-MS/MS coupled with amino acid analysis, it was revealed that iturin at m/z 1,043 consists of a circular Asn-Tyr-Asn-Gln-Pro-Asn-Ser peptide and C14 ?-OH fatty acid. Surfactin homologs from Bacillus subtilis THY-7 at m/z 1,030, 1,044, 1,058, and 1,072 possess a circular Glu-Leu-Leu-Val-Asp-Leu-Leu peptide and the ?-OH fatty acid with a different length (C13-C16). Fengycin species at m/z 1,463 and 1,477 are homologs possessing the circular peptide Glu-Orn-Tyr-Thr-Glu-Ala-Pro-Gln-Tyr-Ile linked to a C16 or C17 ?-OH fatty acid, whereas fengycin at m/z 1,505 contains a Glu-Orn-Tyr-Thr-Glu-Val-Pro-Gln-Tyr-Ile sequence with a Val instead of Ala at position 6. The method developed in this work provided an efficient approach for characterization of diverse lipopeptide isoforms from the iturin, fengycin, and surfactin families. PMID:25662934

Yang, Huan; Li, Xu; Li, Xue; Yu, Huimin; Shen, Zhongyao

2015-03-01

317

Simultaneous determination of sparfloxacin and commonly used H 2 receptor antagonists by RP-HPLC: application to in vitro drug interactions  

Microsoft Academic Search

Innovative, simple, economical, and rapid reverse phase HPLC method has been developed and validated for simultaneous determination\\u000a of sparfloxacin (SPFX) and cimetidine, ranitidine, and famotidine (H2 receptor antagonists) in bulk material, pharmaceutical formulations, and human serum. Chromatographic system was consisting\\u000a of schemed HPLC system having UV detector set at 232 nm for cimetidine and, 250 nm for famotidine and ranitidine. Purospher\\u000a STAR

Najma Sultana; M. Saeed Arayne; Somia Gul; Mahwish Akhtar; Sana Shamim

318

SIMPLE AND FAST RP-HPLC METHOD FOR THE DETERMINATION OF PREDNISOLONE SODIUM PHOSPHATE, PREDNISOLONE, ATROPINE AND HOMATROPINE AS RESIDUALS IN CLEANING VALIDATION OF INDUSTRIAL PHARMACEUTICAL EQUIPMENT  

Microsoft Academic Search

Determining traces of pharmaceuticals in equipment is an important step for controlling cross-contamination during production cycle. Long time consuming analysis cannot be applicable because it increments costs, especially in evaluating residuals as steroids and alkaloids that require a fast and specific technique. Here an isocratic reversed phase HPLC method is developed for the traces analysis of Prednisolone Sodium Phosphate (PSP),

Alen Nils Baeza Fonte; Magdiel Pulido Legró; Yodarka Rodríguez Céspedes

2012-01-01

319

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

320

Development and Validation of a RP-HPLC Method for the Simultaneous Determination of Aceglutamide and Oxiracetam in an Injection Formulation.  

PubMed

This paper describes a rapid method to determine aceglutamide (ACE) and oxiracetam (OXI) present in an injection formulation using reversed-phase high-performance liquid chromatography. The method was validated with respect to suitability, linearity, accuracy, precision and robustness. Chromatography was carried out on an Elite SinoChrom ODS-BP C18 (5 ?m, 250 × 4.60 mm) column with an isocratic mobile phase composed of methanol-phosphate buffer (pH 3.0) in the ratio of 5:95, v/v, at a flow rate of 1.0 mL/min. Detection was carried out using a UV-PDA detector at 210 nm. The linearity range for ACE and OXI were 10-500 and 10-300 ?g/mL, respectively. The relative standard deviations for replicate measurements were always <2%. PMID:25238766

Wang, Dandan; Wu, Shengde

2015-05-01

321

Comparison of adsorption coefficient (K[sub oc]) for soils and HPLC retention factors of aromatic hydrocarbons using a chemically immobilized humic acid column in RP-HPLC  

SciTech Connect

The determination of soil adsorption coefficients (K[sub oc]) via HPLC capacity factors (k[prime]) has been studied, including the effect of column type and mobile phase composition on the correlation between log K[sub oc] and log k[prime]. K[sub oc] values obtained by procedures other than HPLC correlate well with HPLC capacity factors determined on a chemically immobilized humic acid stationary phase, and it is suggested that this phase is a better model for the sorption onto soil or sediment than the octadecyl-, phenyl- and ethylsilica phases. By using log k[prime][sub w] a theoretical capacity factor has been obtained by extrapolation of the retention data in a binary solvent system to pure aqueous eluent. There is a better correlation between log K[sub oc] and log k[prime][sub w] than the correlation between log K[sub oc] and log k[prime].

Szabo, G. (National Research Inst. for Radiobiology and Radiohygiene, Budapest (Hungary)); Bulman, R.A. (National Radiological Protection Board, Didcot (United Kingdom))

1994-01-01

322

Analysis of flurbiprofen, ketoprofen and etodolac enantiomers by pre-column derivatization RP-HPLC and application to drug–protein binding in human plasma  

Microsoft Academic Search

A stereoselective reversed-phase high-performance liquid chromatography (HPLC) assay to determine the enantiomers of flurbiprofen, ketoprofen and etodolac in human plasma was developed. Chiral drug enantiomers were extracted from human plasma with liquid–liquid extraction. Then flurbiprofen and ketoprofen enantiomers reacted with the acylation reagent thionyl chloride and pre-column chiral derivatization reagent (S)-(?)-?-(1-naphthyl)ethylamine (S-NEA), and etodolac enantiomers reacted with S-NEA using 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide

Yin-Xiu Jin; Yi-Hong Tang; Su Zeng

2008-01-01

323

RP-HPLC-DAD method for the identification of two potential antioxidant agents namely verminoside and 1-O-(E)-caffeoyl-?-gentiobiose from Spathodea campanulata leaves.  

PubMed

A simple and reliable high-performance liquid chromatographic method was successfully developed for the study of fingerprint chromatograms of extract and fractions from the leaves of Spathodea campanulata (SC) using verminoside (1) and 1-O-(E)-caffeoyl-?-gentiobiose (2) as marker compounds. Antioxidant activity of SC was determined by using free radical of 2,2-diphenyl-1-picryl-hydrazyl-hydrate as an experimental model. The docking study of selected target, tyrosinase and ligands (ascorbic acid, compounds 1 and 2) was performed through Autodock Vina v0.8. Fingerprints of methanol, chloroform, ethylacetate, n-butanol and water extracts could resolve 13, 11, 22, 16 and 5 peaks, respectively. Extract, fractions and compounds 1 and 2 previously isolated from SC displayed remarkable antioxidant activity with radical-scavenging activity ranging from 2.5 to 6.7 ?g/mL. In silico study identified compounds 1 and 2 as potential inhibitors of tyrosinase correlating with the observed antioxidant activity in vitro. PMID:25429989

Boniface, Pone Kamdem; Singh, Manju; Verma, Surjeet; Shukla, Aparna; Khan, Feroz; Srivastava, Santosh Kumar; Pal, Anirban

2015-04-01

324

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

325

A simple reversed phase high-performance liquid chromatography (RP-HPLC) method for determination of curcumin in aqueous humor of rabbit  

PubMed Central

This article describes a simple and rapid method for determination of curcumin (diferuloylmethane) in aqueous humor of rabbit using high-performance liquid chromatography (HPLC). Analysis was performed using a C-18 column (250 × 4.6 mm, 5 ? luna) by isocratic elution with a mobile phase containing 25 mM potassium dihydrogen orthophosphate (pH 3.5): Acetonitrile (40:60) and detection at 424 nm using a photodiode array (PDA) detector for curcumin. The regression data for curcumin showed a good linear relationship with r2> 0.998 over the concentration range of 0.1-10 ?g ml?1. Relative standard deviations (RSD) for the intraday and interday coefficient of variations for the assay were less than 5.0 and 8.5, respectively. The recovery of the method was between 79.8-83.6%. The quantification limit of the method for curcumin was 0.01 ?g ml?1. This method has good accuracy, precision, and quantitation limit. It is also concluded that the method is useful for measuring very low curcumin concentrations in aqueous humor. PMID:25126537

Mishra, Akhilesh; Dewangan, Gayatri; Singh, W Ramdas; Hazra, Sarbani; Mandal, Tapan Kumar

2014-01-01

326

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

327

Development of a RP-HPLC Method for Analysis of Triphala Curna and its Applicability to Test Variations in Triphala Curna Preparations.  

PubMed

A sensitive, rapid, reverse phase HPLC method is reported for analysis of Triphala Curna using gallic acid, chebulagic acid and chebulinic acid as markers. Validation data for the method has been provided. Unlike methods of recovery testing adopted for synthetic chemicals, a modified approach has been presented here for a formulation like Triphala Curna having three myrobalans in its composition. Data has been provided to demonstrate applicability of the method developed to assess the variation in the Triphala Curna preparations. PMID:20502543

Pawar, V; Lahorkar, P; Anantha Narayana, D B

2009-07-01

328

Simultaneous determination of ascorbic acid, aminothiols, and methionine in biological matrices using ion-pairing RP-HPLC coupled with electrochemical detector.  

PubMed

A novel highly sensitive ion-pairing reversed-phase high performance liquid-chromatography/electrochemical detection method for simultaneous determination of L -ascorbic acid, aminothiols, and methionine in biological matrices is presented. Reduced forms of the analytes are extracted from sample matrices with 10% m-phosphoric acid solution(aqueous). To determine the total vitamin C, the total aminothiols, and the total methionine, samples are treated with tris(2-carboxyethyl)phosphine solution in 0.05% trifluoroacetic acid solution(aqueous) subsequent to deproteination to reduce the oxidized forms of these compounds. Various analytes are separated on a C18 (250?×?4.6 mm, 5 ?m) analytical column using methanol-0.05% trifluoroacetic acid solution(aqueous) (05:95 v/v, containing 0.1 mM 1-octane sulfonic acid as the ion-pairing agent) as the isocratic mobile phase that is pumped at a flow rate of 1.5 ml/min at room temperature. The column eluents are monitored at a voltage of 0.85 V. These analytes are efficiently resolved in less than 20 min using n-acetyl cysteine as the internal standard. PMID:25323509

Khan, Muhammad Imran; Iqbal, Zafar; Khan, Abad

2015-01-01

329

RP-HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF ATORVASTATIN CALCIUM, LOSARTAN POTASSIUM, ATENOLOL, AND ASPIRIN FROM TABLET DOSAGE FORM AND PLASMA  

Microsoft Academic Search

A rapid, simple, sensitive, and selective chromatographic method has been developed for the simultaneous estimation of atorvastatin calcium, losartan potassium, atenolol, and aspirin in marketed formulation. The separation was carried out on a KYA TECH HiQ Sil C18HS (250 × 4.6 mm i.d., 5 µm particle size) column using a mobile phase of acetonitrile: 0.02 M potassium dihydrogen phosphate buffer (pH 3.4) (70:30% v\\/v). The

Neela M. Bhatia; Sachin B. Gurav; Swapnil D. Jadhav; Manish S. Bhatia

2012-01-01

330

Development and Validation of RP-HPLC Method for Simultaneous Estimation of Picroside I, Plumbagin, and Z-guggulsterone in Tablet Formulation  

PubMed Central

The aim of the present work was to develop and validate a reversed-phase high-performance liquid chromatography method for the simultaneous estimation of picroside I, plumbagin, and Z-guggulsterone in a polyherbal formulation containing Picrorhiza kurroa, Plumbago zeylanica, and Commiphora wightii extracts. The analysis was performed on a C18 column using the mobile phase consisting of solvent A (acetonitrile) and solvent B (0.1% orthophosphoric acid in water) with the following gradient: 0-12 min, 25% A; 12-17 min, 25-80% A; 17-32 min, 80% A; and 32-37 min, 80-25% A at a flow rate of 1 ml/min. Ultraviolet detection was at 255 nm. The method was validated for accuracy, precision, linearity, specificity, and sensitivity as per the norms of the International Conference on Harmonization. From the validation study, it was found that the method is specific, accurate, precise, reliable, and reproducible. Good linear correlation coefficients (r2>0.900) were obtained for calibration plots in the ranges tested. Limits of detection were 2.700, 0.090 and 0.099 ?g/ml and limits of quantification were 9.003, 0.310, and 0.330 ?g/ml for picroside I, plumbagin, and Z-guggulsterone, respectively. Intra and interday relative standard deviation (RSD) of retention times and peak areas was less than 3.0%. Recovery was found to be 100.21% for picroside I, 102.5% for plumbagin, and 103.84% for Z-guggulsterone. The established method was appropriate and the three markers were well resolved, enabling efficient quantitative analysis of picroside I, plumbagin and Z-guggulsterone. The method is a rapid and cost-effective quality control tool for routine quantitative analysis of picroside I, plumbagin, and Z-guggulsterone in tablet dosage form. PMID:24302803

Akhade, Meenakshi S.; Agrawal, Poonam A.; Laddha, K. S.

2013-01-01

331

RBC indices  

MedlinePLUS

... corpuscular hemoglobin concentration (MCHC); Mean corpuscular volume (MCV); Red blood cell indices ... and hemoglobin. The MCV reflects the size of red blood cells. The MCH and MCHC reflect the ...

332

Centrality Indices  

Microsoft Academic Search

\\u000a Centrality indices are to quantify an intuitive feeling that in most networks some vertices or edges are more central than\\u000a others. Many vertex centrality indices were introduced for the first time in the 1950s: e.g., the Bavelas index [50, 51],\\u000a degree centrality [483] or a first feedback centrality, introduced by Seeley [510]. These early centralities raised a rush\\u000a of research

Dirk Koschützki; Katharina Anna Lehmann; Leon Peeters; Stefan Richter; Dagmar Tenfelde-podehl; Oliver Zlotowski

2004-01-01

333

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

334

Position indicator  

DOEpatents

A nuclear reactor system is described in which a position indicator is provided for detecting and indicating the position of a movable element inside a pressure vessel. The movable element may be a valve element or similar device which moves about an axis. Light from a light source is transmitted from a source outside the pressure vessel to a first region inside the pressure vessel in alignment with the axis of the movable element. The light is redirected by a reflector prism to a second region displaced radially from the first region. The reflector prism moves in response to movement of the movable element about its axis such that the second region moves arcuately with respect to the first region. Sensors are arrayed in an arc corresponding to the arc of movement of the second region and signals are transmitted from the sensors to the exterior of the reactor vessel to provide indication of the position of the movable element.

Tanner, David E. (Poway, CA)

1981-01-01

335

Validated stability-indicating high-performance thin-layer chromatographic method for estimation of cefpodoxime proxetil in bulk and in pharmaceutical formulation according to International conference on harmonization guidelines  

PubMed Central

Aim: A simple, selective, precise, and stability-indicating high-performance thin-layer chromatographic (HPTLC) method for analysis of cefpodoxime proxetil both in bulk and in pharmaceutical formulation has been developed and validated. Materials and Methods: The method employed HPTLC aluminum plates precoated with silica gel 60 RP-18 F254 as the stationary phase. The solvent system consisted of toluene:methanol:chloroform (4:2:4 v/v). The system was found to give compact spot for cefpodoxime proxetil (Rf value of 0.55 ± 0.02). Densitometric analysis of cefpodoxime proxetil was carried out in the absorbance mode at 289 nm. Results: The linear regression analysis data for the calibration plots showed good linear relationship, with r2 = 0.998 ± 0.0015 with respect to peak area in the concentration range of 100–600 ng per spot. The mean value±SD of slope and intercept were 3.38 ± 1.47 and 986.9 ± 108.78 with respect to peak area. The method was validated for precision, recovery, and robustness. The limits of detection and quantification were 3.99 and 12.39 ng per spot, respectively. Cefpodoxime proxetil was subjected to acid and alkali hydrolysis, oxidation, and thermal degradation. The drug undergoes degradation under acidic and basic conditions, indicating that the drug is susceptible to both acid and base. The degraded product was well resolved from the pure drug, with significantly different Rf value. Statistical analysis proves that the method is repeatable, selective, and accurate for the estimation of the investigated drug. Conclusion: The proposed HPTLC method can be applied for identification and quantitative determination of cefpodoxime proxetil in both bulk drug and pharmaceutical formulation. PMID:22557919

Jain, Pritam; Chaudhari, Amar; Bang, Anup; Surana, Sanjay

2012-01-01

336

Social Indicators  

NSDL National Science Digital Library

The House of Commons Library Research Papers are published for the benefit of Parliament members, but this one should be of interest to both researchers and general readers wanting to learn more about contemporary British social issues. Social Indicators is the first paper in a new series that will be published three times a year. The 71-page paper includes a wide range of topic pages that present social statistics on a variety of issues, from the prison population to defense expenses to agricultural outputs. Each Social Indicator paper will also offer feature articles that give a closer look at specific subjects (in this instance,, election turnout and adult literacy) and an article on statistical sources for a particular issue (in this paper, social security statistics). The last few pages are devoted to a list of important, recent governmental statistical publications.

Bolton, Paul.

337

Development and Validation of a Stability-Indicating Capillary Electrophoresis Method for the Determination of Zolpidem Tartrate in Tablet Dosage Form with Positive Confirmation using 2D- and 3D-DAD Fingerprints  

PubMed Central

The aim of the current study was to develop a simple, precise, and accurate capillary zone electrophoresis method for the determination of zolpidem tartrate in tablet dosage form. Separation was conducted in normal polarity mode at 25°C, 22 kV, using hydrodynamic injection for 10 s. Separation was achieved using a background electrolyte of 20 mM disodium hydrogen phosphate adjusted with phosphoric acid (85%), pH at 5.50, and detection at 254 nm. Using the above optimized conditions, complete determination took place in less than 3 min using amiloride HCl as the internal standard. The method was linear over the range of 3–1000 ?g mL?1 with a correlation coefficient of 0.9999. Forced degradation studies were conducted by introducing a sample of zolpidem tartrate standard and pharmaceutical sample solutions to different forced degradation conditions, being neutral (water), basic (0.1 M NaOH), acidic (0.1 M HCl), oxidative (10% H2O2), temperature (60°C in oven for 3 days), and photolytic (exposure to UV light at 254 nm for 2 h). Degradation products resulting from the stress studies did not interfere with the detection of zolpidem tartrate and the assay can be considered stability-indicating. PMID:24959406

Al Azzam, Khaldun M.; Yit, Lee Kam; Saad, Bahruddin; Shaibah, Hassan

2014-01-01

338

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

339

Indices to detect Hopf bifurcation in Induction motor drives  

E-print Network

The loss of stability of induction motor controlled by Indirect Field Oriented Control (IFOC) is a matter of great concern of operators and design engineers. This paper reports indices to detect and predict stability problem such as system oscillations. Oscillations as a result of loss of stability, due to Hopf bifurcation, for different parameter values of IFOC motor are studied using the proposed indices.

Krishnendu Chakrabarty; Urmila Kar

2014-10-24

340

Stability monitoring of fuzzy systems using trend analysis  

Microsoft Academic Search

Research in stability analysis of fuzzy logic controlled systems have intensified in the last decade without producing an adequate stability theory for the design of such systems. The paper presents an on-line stability indicator that identifies the stability state of the control system by monitoring system response. Unlike most stability analyses, the indicator does not depend on the development of

Natalie R. Spooner; Patrick P. K. Lim

1996-01-01

341

SRR Ecological Assessment Indicators: Selection and  

E-print Network

, Soil aggregate stability · Water - Surface water frequency, Volume · Plants - Key species, Invasives are documented and assessed. #12;Water ­ Specific Methods · Frequency or duration of surface water (TIMESRR Ecological Assessment Indicators: Selection and Monitoring Techniques Dr. Mike Smith University

Wyoming, University of

342

Influence of plant growth stage and season on the release of root phenolics by mulberry as related to development of phytoremediation technology  

Microsoft Academic Search

The phenolics released by red mulberry (Morus rubra L.) roots at different growth stages within a season were quantified and the makeup of phenols analyzed by reverse-phase high performance liquid chromatography (RP-HPLC). The data show that total phenols released into the soil solution increased continuously from an early vegetative stage to leaf senescence, indicating their accumulation in the rhizosphere. From

Ramesh S. Hegde; John S. Fletcher

1996-01-01

343

Mass Spectrometric Identification of the Arginine and Lysine deficient Proline Rich Glutamine Rich Wheat Storage Proteins  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tandem mass spectrometry (MS/MS) of enzymatic digest has made possible identification of a wide variety of proteins and complex samples prepared by such techniques as RP-HPLC or 2-D gel electrophoresis. Success requires peptide fragmentation to be indicative of the peptide amino acid sequence. The f...

344

Metallic alloy stability studies  

NASA Technical Reports Server (NTRS)

The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

Firth, G. C.

1983-01-01

345

Purification and identification of dipeptidyl peptidase (DPP) IV inhibitory peptides from the macroalga Palmaria palmata.  

PubMed

Dipeptidyl peptidase (DPP)-IV inhibitory peptides were purified and identified from an aqueous Palmaria palmata protein extract hydrolysed with Corolase PP. The hydrolysate was fractionated by solid phase extraction (SPE) using a C18 matrix followed by semi-preparative reverse phase-high performance liquid chromatography (SP RP-HPLC). IC50 values of 1.47 ± 0.09, 0.54 ± 0.03 and 0.36 ± 0.03 mg/ml were obtained for the hydrolysate, the 25%--acetonitrile (ACN) SPE fraction and the most active SP RP-HPLC peptide fraction (SP RP-HPLC 25_F28), respectively. Thirteen peptide sequences were identified following UPLC-ESI MS/MS analysis of SP RP-HPLC 25_F28. Three novel DPP-IV inhibitory peptides, Ile-Leu-Ala-Pro, Leu-Leu-Ala-Pro and Met-Ala-Gly-Val-Asp-His-Ile, with IC50 values in the range 43-159 ?M were identified. The results indicate that P. palmata derived peptides may have potential as functional food ingredients in the prevention and management of type 2 diabetes. PMID:25442570

Harnedy, Pádraigín A; O'Keeffe, Martina B; FitzGerald, Richard J

2015-04-01

346

Indicators+: a proposal for everyday peace indicators.  

PubMed

Many of the approaches to measuring peace favoured by international organisations, INGOs and donor governments are deficient. Their level of analysis is often too broad or too narrow, and their aggregated statistical format often means that they represent the conflict-affected area in ways that are meaningless to local communities. This article takes the form of a proposal for a new generation of locally organised indicators that are based in everyday life. These indicators are inspired by practice from sustainable development in which indicators are crowd sourced. There is the potential for these to become 'indicators+' or part of a conflict transformation exercise as communities think about what peace might look like and how it could be realised. The article advocates a form of participatory action research that would be able to pick up the textured 'hidden transcript' found in many deeply divided societies and could allow for better targeted peacebuilding and development assistance. PMID:22868180

Mac Ginty, Roger

2013-02-01

347

ECOLOGICAL PERFORMANCE INDICATORS  

EPA Science Inventory

EMAP has traditionally relied on indicators of ecological condition to report on the extent to which coastal waters are impaired. Correlations between biological indicators and physical or chemical indicators may generate hypotheses about potential causes of impairment but are n...

348

Stabilizing biocatalysts.  

PubMed

The area of biocatalysis itself is in rapid development, fueled by both an enhanced repertoire of protein engineering tools and an increasing list of solved problems. Biocatalysts, however, are delicate materials that hover close to the thermodynamic limit of stability. In many cases, they need to be stabilized to survive a range of challenges regarding temperature, pH value, salt type and concentration, co-solvents, as well as shear and surface forces. Biocatalysts may be delicate proteins, however, once stabilized, they are efficiently active enzymes. Kinetic stability must be achieved to a level satisfactory for large-scale process application. Kinetic stability evokes resistance to degradation and maintained or increased catalytic efficiency of the enzyme in which the desired reaction is accomplished at an increased rate. However, beyond these limitations, stable biocatalysts can be operated at higher temperatures or co-solvent concentrations, with ensuing reduction in microbial contamination, better solubility, as well as in many cases more favorable equilibrium, and can serve as more effective templates for combinatorial and data-driven protein engineering. To increase thermodynamic and kinetic stability, immobilization, protein engineering, and medium engineering of biocatalysts are available, the main focus of this work. In the case of protein engineering, there are three main approaches to enhancing the stability of protein biocatalysts: (i) rational design, based on knowledge of the 3D-structure and the catalytic mechanism, (ii) combinatorial design, requiring a protocol to generate diversity at the genetic level, a large, often high throughput, screening capacity to distinguish 'hits' from 'misses', and (iii) data-driven design, fueled by the increased availability of nucleotide and amino acid sequences of equivalent functionality. PMID:23807146

Bommarius, Andreas S; Paye, Mariétou F

2013-08-01

349

Urban indices as environmental noise indicators  

Microsoft Academic Search

The objective of this paper is to analyze the noise levels of an urban area by treating them as a function of several features resulting from block shapes and urban indices in a residential neighborhood of a medium sized Brazilian city. Inside this area a sample of 40 reference points was chosen for data collection and their noise levels were

Léa Cristina Lucas de Souza; Mariene Benutti Giunta

2011-01-01

350

Stability Tunnel  

NASA Technical Reports Server (NTRS)

Engineers operate the controls of the Stability Tunnel: Plans for a new tunnel to study stability problems began in the late thirties. The Stability Tunnel was authorized in 1939 and began operations in June 1941. The installation was completed in December that year with the completion of a new 10,000 Horsepower Diesel-electric generating plant. It was a single return, closed jet tunnel with a 6-foot square test section. The tunnel was disassembled and shipped to Virginia Polytechnic Institute and State University in 1958. The tunnel had two separate test sections: one for curved flow, the other for rolling flow. 'The facility...simulates the motion of the aircraft in curved or rolling flight. This is done by actually curving or rolling the airstream as it passes over the model and at the same time providing the proper velocity distribution.' (From AIAA-80-0309) >From Alan Pope, Wind-Tunnel Testing: 'The only tunnel directly designed for dynamic stability work is located at the Langley Field branch of the NACA. Its most vital feature is its ability to subject the models to curving air streams that simulate those actually encountered when an airplane rolls, pitches, or yaws. the rotating airstream for simulating roll is produced by a motor-driven paddle just ahead of the test section. Curved air of properly varying velocity for simulating pitch and yaw is produced by a combination of a curved test section and velocity screens. The proper use of this apparatus makes possible the determination of the stability derivatives.' (pp. 13-14)

1943-01-01

351

Alternative solar indices  

NASA Astrophysics Data System (ADS)

Possible alternative Solar Indices which could either be a perturbation from the currently defined Solar Index or possible indices based on current technologies for other media markets are discussed. An overview is given of the current project, including the logic that was utilized in defining its current structure and then alternative indices and definitions are presented and finally, recommendations are made for adopting alternative indices.

Lantz, L. J.

1980-07-01

352

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...

353

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

354

Analysis of Wheat Prolamins, the Causative Agents of Celiac Sprue, Using Reversed Phase High Performance Liquid Chromatography (RP-HPLC) and Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS)  

PubMed Central

Wheat prolamins, commonly known as “gluten”, are a complex mixture of 71–78 proteins, which constitute ~80% of the proteins in the wheat grains and supply 50% of the global dietary protein demand. Prolamins are also responsible for numerous gluten-induced disorders and determine the unique visco-elastic properties of the wheat dough. These properties necessitate the reliable determination of the prolamin composition in wheat grains and their derived products. Therefore, this study examined the impact of HPLC conditions, including column type, column temperature, flow rate, and the gradient of polar and non-polar solvents in the mobile phase, to improve the analytical resolution of prolamins. The following conditions were found optimal for analyses: column temperature 60 °C, flow rate 1.0 mL/min and an elution gradient of 20%–60% of 0.1% trifluoroacetic acid + acetonitrile in 60 min. For further improvement of resolution, gliadin and glutenin extracts were analyzed using MALDI-TOF-MS in combination with HPLC fractionation. Two semi-quantitative methods, densitometry of stained polyacrylamide gels and HPLC, were used to determine relative prolamin quantities and the correspondence between the methods was established. The combinatorial gluten analyses approach developed during the present study was used to analyze prolamin profiles of wheat transformants expressing DEMETER silencing artificial microRNA, and the results are discussed. PMID:24739977

Mejías, Jaime H.; Lu, Xiaoqiao; Osorio, Claudia; Ullman, Jeffrey L.; von Wettstein, Diter; Rustgi, Sachin

2014-01-01

355

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

2013-12-01

356

Fluid leak indicator  

NASA Technical Reports Server (NTRS)

A fluid leak indicator for detecting and indicating leaks in visually inaccessible fluid tubing joints, such as those obstructed by insulation includes a bag system and a wicking system surrounding or wrapping the joints under the visual obstructing material. Leaking fluid is collected in the bag or on the wicking material where it is conducted along the wicking material to a visily accessible capturing transparent indicator bulb for providing a visual indication of the leak without requiring a chemical change in the capturing indicator bulb.

Anderson, G. E.; Loo, S. (inventors)

1985-01-01

357

Some Investigations with Indices.  

ERIC Educational Resources Information Center

Suggests activities involving the use of indices. Provides five activities with examples for routine practice, pattern recognition, prediction, conjecture, generalization, factorization, and limit concept. (YP)

Andrews, Paul

1989-01-01

358

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. 

Center for Disease Control

359

Indicators of Quality.  

ERIC Educational Resources Information Center

Surveyed students, faculty, administrative staff, governing board, and employers affiliated with a public two-year college to determine their perceptions of various quality indicators and congruence between the groups. Found that all groups placed importance on indicators of customer satisfaction and skill development; beyond that, considerable…

Cleary, Thomas S.

2001-01-01

360

Indicators and Statewide Assessment.  

ERIC Educational Resources Information Center

This report is designed to share the experiences of Oregon's Department of Education, thus far, with both the conceptual and actual use of indicators in assessing progress toward State level goals and objectives. The first chapter outlines the history of the study and briefly discusses the concept of indicators as used in the report. The report…

Clemmer, Robert; And Others

361

Temperature-indicating Paints  

NASA Technical Reports Server (NTRS)

This report is an attempt at a new method of coating the surface of the cylinder with materials that undergo chemical change at definite temperatures as indicated by a change in color. In this way it was hoped that the substance itself would indicate directly the position of its isotherms, which in measurements with thermocouples requires a tedious amount of labor.

Penzig, F

1939-01-01

362

Retractable Visual Indicator Assembly  

NASA Technical Reports Server (NTRS)

A retractable indicator assembly may be mounted on a container which transmits air through the container and removes deleterious gases with an activated charcoal medium in the container. The assembly includes: an elongate indicator housing has a chamber therein; a male adaptor with an external threads is used for sealing engagement with the container; a plug located at the upper end of the housing; a housing that includes a transparent wall portion for viewing at least a portion of the chamber; a litmus indicator, moveable by a retractable rod from a retracted position within the container to an extended position within the chamber of the housing; and an outer housing that is secured to the upper end of the rod, and protects the indicator housing while the litmus indicator is in its normally retracted position. The assembly may be manually manipulated between its extended position wherein the litmus indicator may be viewed through the transparent wall of the indicator housing, and a retracted position wherein the outer housing encloses the indicator housing and engages the exterior of the container.

Hackler, George R. (Inventor); Gamboa, Ronald J. (Inventor); Dominquez, Victor (Inventor)

1998-01-01

363

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

364

Cabbage Juice Indicator  

NSDL National Science Digital Library

In this chemistry activity, learners make indicator solution from red cabbage. Then, learners test everyday foods and household substances using the cabbage juice indicator. Learners will record the color change, approximate pH (using the pH scale), and identify if it is an acid or base. As an extension, learners can make pH paper strips to conduct an "at home" pH test of other household items. The indicator solution can be frozen in ice trays and when mixed with alcohol, can last for months. For safety reasons, adult supervision is recommended.

The Science House

2014-01-28

365

Tamper indicating bolt  

DOEpatents

A tamper-indicating fastener has a cylindrical body with threads extending from one end along a portion of the body, and a tamper indicating having a transducer for converting physical properties of the body into electronic data; electronics for recording the electronic data; and means for communicating the recorded information to a remote location from said fastener. The electronics includes a capacitor that varies as a function of force applied by the fastener, and non-volatile memory for recording instances when the capacitance varies, providing an indication of unauthorized access.

Blagin, Sergei V.; Barkanov, Boris P.

2004-09-14

366

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.

367

[KS-02 cardiosignal indicator].  

PubMed

Considerations are given as to principles of designing KC-02 indicator of electrocardiosignals. It provides continuous monitoring of cardiac activity based on examinations of rhythm patterns on ECG-recording. PMID:3999962

Bol'shov, V M; Popov, V P; Prokudin, A S; Shamonin, V V

1985-01-01

368

Riser position indication apparatus  

SciTech Connect

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 secure the riser position indication apparatus to the riser, flexible weight means having one end connected to one of the connection means and the other end operatively engaged with the other of the connection means, weight signal transmitter means associated with at least one end of the flexible weight means and operative to produce a continuous output signal which varies as a function of the weight of the weight means suspended from one end of the connection means.

Moore, B.B.

1986-09-23

369

ENVIRONMENTAL PUBLIC HEALTH INDICATORS  

EPA Science Inventory

Environmental Public Health Indicators (EPHIs), quantitative measures of health factors and environmental influences tracked over time, can be used to identify specific areas and populations for intervention and prevention efforts and to evaluate the outcomes of implemented polic...

370

Sustainability Indicators and Metrics  

EPA Science Inventory

Sustainability is about preserving human existence. Indicators and metrics are absolutely necessary to provide at least a semi-quantitative assessment of progress towards or away from sustainability. Otherwise, it becomes impossible to objectively assess whether progress is bei...

371

World Development Indicators  

NSDL National Science Digital Library

Published by the World Bank Group, World Development Indicators is an annual report containing statistical data on global topics such as people, environment, the economy, and states and markets. The Website for World Development Indicators provides all of the text of the report, but it only contains a small selection of the tables offered in the actual report, which is available on CD ROM for purchasing.

372

Aggregating Governance Indicators  

Microsoft Academic Search

October 1999With the right method, aggregate indicators can provide useful estimates of basic governance concepts as well as measures of the imprecision of these aggregate estimates and their components.In recent years the growing interest of academics and policymakers in governance has been reflected in the proliferation of cross-country indices measuring various aspects of governance.Kaufmann, Kraay, and Zoido-Lobat?n explain how a

Pablo Zoido-Lobaton; Daniel Kaufmann

1999-01-01

373

Stabilizing brokerage  

PubMed Central

A variety of social and economic arrangements exist to facilitate the exchange of goods, services, and information over gaps in social structure. Each of these arrangements bears some relationship to the idea of brokerage, but this brokerage is rarely like the pure and formal economic intermediation seen in some modern markets. Indeed, for reasons illuminated by existing sociological and economic models, brokerage is a fragile relationship. In this paper, we review the causes of instability in brokerage and identify three social mechanisms that can stabilize fragile brokerage relationships: social isolation, broker capture, and organizational grafting. Each of these mechanisms rests on the emergence or existence of supporting institutions. We suggest that organizational grafting may be the most stable and effective resolution to the tensions inherent in brokerage, but it is also the most institutionally demanding. PMID:22198763

Stovel, Katherine; Golub, Benjamin; Milgrom, Eva M. Meyersson

2011-01-01

374

Extraction of polypropylene additives and their analysis by HPLC  

Microsoft Academic Search

Summary  The polypropylene additives were extracted by dissolution-precipitation and Soxhlet. The Soxhlet method was adapted for the\\u000a extraction of phosphorous antioxidants. The RP HPLC method with quaternary gradient elution separated five chemical groups\\u000a of additives: lower molecular mass di-tert-butyl phenol (D.T.B.P.), hindered amine light stabilizers (Tinuvin 326), hindered\\u000a phenolic antioxidants (Irganox 1010) and phosphorous antioxidants (Irgafos 168 and Ultranox 626) with

H. El Mansouri; N. Yagoubi; D. Ferrier

1998-01-01

375

[Activity indices in IBD].  

PubMed

Inflammatory bowel disease (IBD) encompasses two medical conditions, Crohn's disease (CD) and ulcerative colitis (UC). These are chronic idiopathic conditions, marked by recurrent episodes of inflammation of the gastrointestinal tract, interspersed with periods of remission. An important feature of both disorders is that patients vary significantly in their clinical, endoscopic, biochemikal and histologic features. The heterogeneity in disease activity makes objective assessment of disease activity a prerequisite for rationale choice of therapy. At present, a number of activity indices are available for both conditions. These indices may be distinguished in more subjective (clinical), more objective (endoscopic-histological, biochemical) or a combination of the two. All these indices are rather complex and time-consuming; therefore their use is limited to clinical trials. Despite the different indices available, there is no consensus in the literature as to which is the most valid. In everyday clinical practice most gastroenterologists rely on their global clinical judgement, which is less reproducible, but simpler for decision-making in patients treatment. The aim of this article is to provide an overview of the disease activity indices (with a focus on the most frequently used), with analysis of their utilities, strengths and limitations. PMID:24471293

Katici?, Miroslava

2013-04-01

376

Aircraft control position indicator  

NASA Technical Reports Server (NTRS)

An aircraft control position indicator was provided that displayed the degree of deflection of the primary flight control surfaces and the manner in which the aircraft responded. The display included a vertical elevator dot/bar graph meter display for indication whether the aircraft will pitch up or down, a horizontal aileron dot/bar graph meter display for indicating whether the aircraft will roll to the left or to the right, and a horizontal dot/bar graph meter display for indicating whether the aircraft will turn left or right. The vertical and horizontal display or displays intersect to form an up/down, left/right type display. Internal electronic display driver means received signals from transducers measuring the control surface deflections and determined the position of the meter indicators on each dot/bar graph meter display. The device allows readability at a glance, easy visual perception in sunlight or shade, near-zero lag in displaying flight control position, and is not affected by gravitational or centrifugal forces.

Dennis, Dale V. (inventor)

1987-01-01

377

Pulsar braking indices revisited  

NASA Astrophysics Data System (ADS)

Using the standard equation for the slowdown of a neutron star, we derive a formula for the braking index via integration rather than the conventional differentiation. The new formula negates the need to measure the second time derivative of the rotation frequency, nu ? . We show that the method gives similar braking indices for PSR B1509-58 and the Crab pulsar to those already in the literature. We point out that our method is useful for obtaining the braking indices of moderate-aged pulsars without the need for long, phase-connected timing solutions. We applied the method to 20 pulsars and discuss the implications of the results. We find that virtually all the derived braking indices are dominated by the effects of (unseen) glitches, the recovery from which corrupts the value of nu solar. However, any real, large, positive braking index has implications for magnetic field decay and offers support to recent models of pulsar evolution.

Johnston, Simon; Galloway, David

1999-07-01

378

On the crisis stability of a submarine deterrent  

SciTech Connect

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 of the non-survivable land missiles. With ground-based interceptor (GBI) defenses, stability initially falls faster. The number of GBIs could be increased gradually to minimize their impact on stability.

Canavan, G.H.

1992-05-01

379

Rhinoplasty – indications and techniques  

PubMed Central

Rhinoplasty is considered to be one of the most challenging procedures in otolaryngology head and neck surgery. Meticulous planning and excellent surgical skills are pre-requisites for reproducible good outcomes. More than 100 years after the first rhinoplasty, many controversies regarding indication and techniques remain unresolved. The aim of this article is to review current concepts and arguments. PMID:22073085

Tasman, Abel-Jan

2008-01-01

380

Landscape-based Indicators  

EPA Science Inventory

The report is based on data and experience gained through the GLNPO-funded Great Lakes Coastal Wetland Consortium (GLCWC) and the EPA-STAR funded Great Lakes Ecological Indicators Project (GLEI). EPA-MED author Trebitz and other MED personnel were collaborators on the GLEI proje...

381

Universal Indicator Rainbow Trout  

NSDL National Science Digital Library

In this activity on page 2 of the PDF, learners discover how color changes can help scientists distinguish between acids and bases. Learners create colorful rainbow trout artwork using universal indicator solution and various household liquids. Safety note: learners must wear safety goggles.

2013-07-08

382

Triboluminescent indicator system  

DOEpatents

There is provided a light emitting device comprising a plurality of triboluminescent particles dispersed throughout a low density, frangible body and activated by rapidly crushing the body in order to transfer mechanical energy to some portion of the particles. The light emitted by these mechanically excited particles is collected and directed into a light conduit and transmitted to a detector/indicator means.

Goods, Steven H. (Livermore, CA); Dentinger, Paul M. (Sunol, CA); Whinnery, Jr., Leroy L. (Danville, CA)

2003-06-24

383

Industrial Energy Use Indices  

E-print Network

Energy use indices and associated coefficients of variation are computed for major industry categories for electricity and natural gas use in small and medium-sized plants in the U.S. Standard deviations often exceed the average EUI for an energy...

Hanegan, A.; Heffington, W. M.

2007-01-01

384

Supersonic Wave Interference Affecting Stability  

NASA Technical Reports Server (NTRS)

Some of the significant interference fields that may affect stability of aircraft at supersonic speeds are briefly summarized. Illustrations and calculations are presented to indicate the importance of interference fields created by wings, bodies, wing-body combinations, jets, and nacelles.

Love, Eugene S.

1958-01-01

385

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

386

Residential Stability and Academic Sense of Control  

ERIC Educational Resources Information Center

Suggests that stability level of an individual and the community in which he operates is directly related to a child's sense of control and consequently his achievement in school. Findings indicate that for whites, community stability is positively and significantly related to sense of control, with the inverse for blacks. (Author/AM)

Gigliotti, Richard J.

1976-01-01

387

Solid-state stability and compatibility studies of clavulanate potassium.  

PubMed

Abstract The kinetic and thermodynamic parameters of degradation of clavulanate potassium in the solid state were studied by using a reversed phase high performance liquid chromatography (RP-HPLC) method. The degradation of clavulanate potassium was a first-order reaction depending on the substrate concentration at an increased relative air humidity (RH) and in dry air. The dependence ln k?=?f(1/T) became the ln k?=?(0.026?±?166.35)-(2702.82?±?1779.43)(1/T) in dry air and ln k?=?(1.65?±?100.40)?×?10(3)-(5748.81?±?3659.67)(1/T) at 76.4% RH. The thermodynamic parameters Ea, ?H(?a), ?S(?a) of the degradation of clavulanate potassium in the solid state were calculated. The dependence ln k?=?f (RH%) assumed the form ln k?=?(8.78?±?5.75) 10?(-2) (RH%) + (2.64?×?10(-8?)±?40.41). The compatibility of clavulanate potassium with commonly used excipients was studied at an increased temperature and in dry air. The geometric structure of molecule, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbitals were also determined in order to predict the structural changes and reactive sites in clavulanate potassium during degradation and compatibility studies in the solid state. The ultraviolet (UV), Fourier transform infrared spectroscopy (FT-IR) and Raman spectra of degraded samples of the compound were analyzed. PMID:24219797

Cielecka-Piontek, Judyta; Paczkowska, Magdalena; Zalewski, Przemys?aw; Lewandowska, Kornelia; Barszcz, Boles?aw

2015-03-01

388

Magnetic Location Indicator  

NASA Technical Reports Server (NTRS)

Ferrofluidic device indicates point of highest magnetic-flux density in workspace. Consists of bubble of ferrofluid in immiscible liquid carrier in clear plastic case. Used in flat block or tube. Axes of centering circle on flat-block version used to mark location of maximum flux density when bubble in circle. Device used to find point on wall corresponding to known point on opposite side of wall.

Stegman, Thomas W.

1992-01-01

389

Indicators for Inquiry  

NSDL National Science Digital Library

Fifth-grade students use homemade plant-based acid/base indicators to learn about matter at an age-appropriate level and develop process skills. As a result of completing this lesson sequence the students should be able to perform many tasks using process skills such as observing chemical changes; identifying acids and bases by performing tests; classifying common household substances as acidic, basic (alkaline), or neutral; and developing a scheme for solving a performance-based scenario.

Jeffery Townsend

2006-02-01

390

Health Care Indicators  

PubMed Central

This regular feature of the journal includes a discussion of each of the following four topics: community hospital statistics; employment, hours, and earnings in the private health sector; health care prices; and national economic indicators. These statistics are valuable in their own right for understanding the relationship between the health care sector and the overall economy. In addition, they allow us to anticipate the direction and magnitude of health care cost changes prior to the availability of more comprehensive data. PMID:25372574

Donham, Carolyn S.; Maple, Brenda T.; Letsch, Suzanne W.

1993-01-01

391

Enhanced stability and dechlorination activity of pre-synthesis stabilized nanoscale FePd particles  

NASA Astrophysics Data System (ADS)

Nanoscale zero-valent iron (NZVI) particles are promising materials for the in-situ remediation of a wide variety of source zone contaminants. This study presents the results of a systematic investigation of the stability of bimetallic FePd nanoparticle suspensions in water and their capability to degrade trichloroethylene (TCE) synthesized in the presence of various stabilizers (i.e., carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), and guar gum). Results indicate a dramatic improvement in FePd suspension stability when the stabilizer is present in the matrix during the nanoparticle synthesis step. Stability enhancement is controlled by iron nanoparticle/stabilizer electrostatic and steric interactions, which are a function of the molecular structure of the stabilizer. Stabilization mechanisms differed for each stabilizer with CMC and guar gum exhibiting the best nanoparticle suspension stability improvement. Results suggest that the complexation of iron precursors with the stabilizer, during synthesis, plays a key role in nZVI stability improvement. In case of guar gum, gelation during synthesis significantly increased suspension viscosity, enhancing suspension stability. The capability of these materials to degrade TCE was also investigated. Results demonstrated that when stabilizers were present in the matrix dechlorination rates increased significantly. FePd nanoparticles in CMC had the highest observed rate constant; however the highest surface area-normalized rate constant was obtained from FePd stabilized in PVP360K. Results from this study can be used to aid in the selection of appropriate iron nanoparticle stabilizers. Stabilizer selection should be assessed on a case by case basis as no stabilizer will meet the needs of all in-situ remediation applications.

Sakulchaicharoen, Nataphan; O'Carroll, Denis M.; Herrera, Jose E.

2010-11-01

392

Dimensional stability of superinvar  

NASA Astrophysics Data System (ADS)

The unloaded dimensional stability and thermal expansivity of a single furnace melt of superinvar have been measured at room temperature using interferometric techniques. Thermal expansivity has been determined with an uncertainty of several parts in 108 per degree centigrade while dimensional stability has been determined with an uncertainty of order one part in i09 per day. Samples subjected to plastic deformation in their processing history displayed a stability improvement from 20. 5 x 1O/day to 5. 5 x 109/day and a reduction in thermal expansivity from 0. 56 x 1O/C to 0. 23 x 106/C associated with the increased mechanical work in the material. 1. MATERIAL SELECTION AND PROCESSING Modern scientific instruments place increasingly stringent demands on the dimensional stability of materials used for the construction of precision structures. The dimensional change of a material due to a change in temperature is characterized by its coefficient of thermal expansion (CTE). Dimensional changes may also occur over time in a fixed environment. In considering the selection of a material for demanding applications both the CTE and temporal stability must be considered. Indeed with reasonable control of the ambient temperature pressure humidity and magnetic field temporal instability may be the factor limiting performance. Superinvar the material studied here is one alloy in a class of materials of practical interest for the construction of precision systems. The invars are relatively inexpensive materials (by comparison other low-CTE materials) and may be fabricated using conventional metalworking techniques. Superinvar is of particular interest because it exhibits a lower CTE than the other invars and because of an early report by Jacobs Bradford and Berthold indicating that it possessed a particularly high degree of temporal stability. 1 This paper reports a series of CTE and temporal stability measurements performed on superinvar samples taken from the same melt but subjected to different degrees of processing. One of the experimental aims of this study was to learn about the conditions leading to the single high stability result reported by Jacobs. Accordingly the chemistry of the material was specified as a high purity superinvar with 31 Ni and 5 Co. This alloy lies at the minimum CTE point of the Fe-Ni-Co system2 and is the nominal alloy used by Jacobs. Table I shows the composition which was specified the analysis performed at the mill at the time of melt and an independent analysis of the material after receipt at Livermore. For reference purposes the composition of the sample measured by Jacobs is also listed. 3 The material used in the samples was cast in an air induction furnace as part of a large order. Although the same steel mill produced both this material and Jacobs'' samples the furnaces used for the two melts were different: Jacobs'' sample came from a melt in

Patterson, Steven R.

1990-11-01

393

The Boston Indicators Project  

NSDL National Science Digital Library

Coordinated by the partnership of the City of Boston, the Metropolitan Area Planning Council, and the Boston Foundation, the Boston Indicators Project "aims to democratize access to information, foster informed public discourse, track progress on shared civic goals, and report on change in 10 sectors: Civic Vitality, Cultural Life and the Arts, the Economy, Education, the Environment, Health, Housing, Public Safety, Technology, and Transportation." Visitors to the site can review the Project's most recent report as well as past versions. At the top of the page, there are various sections to visit, which cover the 10 sectors mentioned above. In each of these sections, visitors can read a brief summary, view highlights within each sector, read about the goals and measures of each sector, and find related links to research, resources, and news for each sector. The website also includes the feature "The Hub of Innovation" which highlights some of the most forward-looking local, regional, national and international work in the ten sectors tracked by the Boston Indicators Project.

394

Breathiness in Indic languages  

NASA Astrophysics Data System (ADS)

Previous work on breathiness in Indic languages has focused on the acoustic properties of breathy oral stops in languages like Hindi ([bal] hair versus [bhal] forehead) or Bengali ([baSa] house versus [bhaSa] language). However, breathiness in Indic languages often extends to nasals (e.g., Marathi ([maar] beat versus [mhaar] a caste). It is unclear if languages such as Hindi and Bengali have breathy nasals in addition to breathy oral stops. This study addresses the following questions: (1) Are breathy nasals (Nh) acoustically different from N+h sequences, both in languages where they are phonemic and ones where they are not? (2) In sequences of a breathy stop and a modal nasal (e.g., Hindi [udhmi] naughty) where is the breathiness realized, if at all? To answer these questions, audio, aerodynamic, and electroglottographic recordings will be made of Hindi, Bengali, and Marathi speakers. It is hypothesized that acoustically breathy nasals in Hindi and Bengali will not be distinct from sequences of N+ h. We believe that this will also be true for the oral stops. In addition, it is believed that in sequences of breathy oral stop followed by a modal nasal (e.g., ChN), the breathiness will be produced on the nasal.

Esposito, Christina; Khan, Sameeruddowla; Hurst, Alex

2005-04-01

395

Molecular Models of Indicators  

NSDL National Science Digital Library

The article by Nicholas C. Thomas and Stephen Faulk on "Colorful Chemical Fountains" (1) reminds us that color—the colors of acid–base indicators or of metal complexes—is responsible for many of us developing an interest in chemistry. The featured molecules this month are the acid and base forms of three common indicators–phenolphthalein, methyl orange, and methyl red. These three substances display interesting structural features as the pH-induced transformation from one form to another takes place in three different ways. In the case of phenolphthalein, the lactam ring is cleaved on deprotonation to produce a carboxyl group with the concomitant removal of a proton from a phenolic group. In methyl orange, one of the nitrogen atoms is protonated in the acid form, and that proton is lost in the base form. In methyl red, a carboxylic acid function is deprotonated. There are many other interesting aspects of acid–base indicators. Since most plants and fruits contain pigments that show a color change in some pH range, it is difficult to state with any degree of certainty when these changes were first put to use in a systematic fashion. The Spanish alchemist Arnaldus de Villa Nova (Arnold of Villanova) is purported to have used litmus in the early 14th century. In general systematic use of indicators is traced to the latter half of the nineteenth century with the development of the three synthetic indicators described above. Many students will be familiar with the use of phenolphthalein to identify blood—often shown on the various forensic chemistry TV dramas by dropping some solution on a cotton swab that has been used to pick up some of the sample in question. If the swab turns red we frequently hear "It's blood". The reality of using phenolphthalein in this way is more complicated. The test is presumptive for the presence of blood, but not conclusive. It is not an acid–base reaction but rather, in the presence of hydrogen peroxide, relies on hemoglobin to catalyze the oxidation of phenolphthalein. An interesting assignment for students in a high-school or non-majors course would be to have them explore the details of this Kastle–Meyers test to see just what is involved in the correct application of the test, and what factors complicate the process. For example, would tomato juice infused with asparagus juice give a positive Kastle–Meyers test? Historically phenolphthalein was used in a variety of laxatives. Recently that usage has been discontinued due to concern about the carcinogenic nature of the substance. A review of the history of the controversy surrounding the use of phenolphthalein in laxatives would make a good research paper at the high-school level. Lastly, students with some practice building structures and performing calculations might wish to explore the structures of two other forms of phenolphthalein—one found in very acidic solutions, having an orange color, and one found in very basic solutions that is colorless.

396

High-performance liquid chromatography coupled with mass spectrometry for analysis of ultrasmall palladium nanoparticles.  

PubMed

Metal nanoparticles (NPs) have recently attracted considerable attention in many areas of research including bioscience, chemistry and material science. Regrettably, most current and past work usually focuses on studies of multi-component NPs mixture where there is a plethora of NPs species co-existing. This work highlights the merits of reverse-phase high-performance liquid chromatography (RP-HPLC) for disclosing the genuine properties of individual palladium nanoparticles (PdNPs) species present in an as-synthesized N,N'-dimethylformamide-stabilized PdNPs product (DMF-PdNPs) which might have been previously hidden or misinterpreted. DMF-PdNPs is successfully separated by RP-HPLC that smaller DMF-PdNPs are approximately eluted first and then follow by the large ones on a C18 column. The separation fractions are further collected and determined their chemical compositions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results unambiguously reveal that the as-synthesized DMF-PdNPs product is indeed a complex mixture of ultrasmall PdxNPs (x=10-20) stabilized with different numbers of DMF ligands. It is anticipated that the separated fractions afforded by RP-HPLC will offer more accurate determinations of the catalytic, electronic, optical and toxicological properties of metal NPs which might have been previously misinterpreted. PMID:25281151

Zhang, Lei; Li, Zhongping; Zhang, Yan; Paau, Man Chin; Hu, Qin; Gong, Xiaojuan; Shuang, Shaomin; Dong, Chuan; Peng, Xiaoguang; Choi, Martin M F

2015-01-01

397

Fatigue failure load indicator  

NASA Technical Reports Server (NTRS)

An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test is described. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time the specimen is subjected to a compression load, means are provided for applying a positive voltage to the rest of the peak detector to reset it. During the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are provided for disconnecting the load cell from the peak detector when there is a failure in the specimen.

Imig, L. A.; Davis, W. T.; Davis, D. C. (inventors)

1979-01-01

398

Enhanced tamper indicator  

DOEpatents

The present invention provides an apparatus and method whereby the reliability and tamper-resistance of tamper indicators can be improved. A flexible connector may be routed through a latch for an enclosure such as a door or container, and the free ends of the flexible connector may be passed through a first locking member and firmly attached to an insert through the use of one or more attachment members such as set screws. A second locking member may then be assembled in interlocking relation with the first locking member to form an interlocked assembly around the insert. The insert may have one or more sharp projections extending toward the first or second locking member so that any compressive force applied in an attempt to disassemble the interlocked assembly results in permanent, visible damage to the first or second locking member.

Garcia, Anthony R.; Johnston, Roger G.

2003-07-08

399

Stability Puzzles in Phage Lambda  

E-print Network

The lysogeny maintenance switch in phage lambda is one of the simplest examples on the molecular level of computation, command and control in a living system. If, following infection of the bacterium E. coli, the virus enters the lysogenic pathway, it represses its developmental functions, and integrates its DNA into the host chromosome. In this state the prophage may be passively replicated for many generations of E. coli. In fact, this repressed state is intrinsically more stable than the gene encoding the repressor. We develop a mathematical formalism to predict the stability of such epigenetic states from affinities of the molecular components. We apply the model to the behavior of recently published mutants at the right operator complex of lambda, and find that the reported stability indicates that the current view of the switch is incomplete. The approach described here should be generally applicable to the stability of expressed states

Erik Aurell; Stanley Brown; Johan Johanson; Kim Sneppen

2000-10-19

400

How can we measure the soil carbon stabilization capacity?  

Microsoft Academic Search

Soils represent an important potential sink for atmospheric CO2 through the actions of various stabilization mechanisms. However, previously published evidence indicates that soils may have a limited capacity to stabilize organic matter. However, determining what the stabilization capacity (and conversely, the saturation deficit) is for a given soil remains a significant challenge. We propose determining the specific surface area (SSA,

A. F. Plante; A. Conover; A. Aufdenkampe

2008-01-01

401

Aplysia Attractin: Biophysical Characterization and Modeling of a Water-Borne Pheromone  

Microsoft Academic Search

Attractin, a 58-residue protein secreted by the mollusk Aplysia californica, stimulates sexually mature animals to approach egg cordons. Attractin from five different Aplysia species are ?40% identical in sequence. Recombinant attractin, expressed in insect cells and purified by reverse-phase high-performance liquid chromatography (RP-HPLC), is active in a bioassay using A. brasiliana; its circular dichroism (CD) spectrum indicates a predominantly ?-helical

Catherine H. Schein; Gregg T. Nagle; Jason S. Page; Jonathan V. Sweedler; Yuan Xu; Sherry D. Painter; Werner Braun

2001-01-01

402

Does indication drive use, or does use drive indication?  

PubMed

In this issue of The Journal of Clinical Psychiatry, Fu et al report on the results of a study of paliperidone palmitate once-monthly in patients diagnosed with schizoaffective disorder. In this well-designed and well-executed trial, paliperidone monthly was used either as monotherapy or as an adjunct to mood stabilizers or antidepressants. The subjects were randomized to continue paliperidone monthly or switch to placebo after a 12-week fixed-dose stabilization phase. PMID:25830459

Lauriello, John; Ithman, Muaid; Gopalakrishna, Ganesh

2015-03-01

403

High Stability Engine Control (HISTEC)  

NASA Technical Reports Server (NTRS)

Future aircraft turbine engines, both commercial and military, must be able to successfully accommodate expected increased levels of steady-state and dynamic engine-face distortion. The current approach of incorporating a sufficient component design stall margin to tolerate these increased levels of distortion would significantly reduce performance. The objective of the High Stability Engine Control (HISTEC) program is to design, develop, and flight demonstrate an advanced, high-stability, integrated engine control system that uses measurement-based, real-time estimates of distortion to enhance engine stability. The resulting distortion tolerant control reduces the required design stall margin, with a corresponding increase in performance and decrease in fuel burn. The HISTEC concept, consisting of a Distortion Estimation System and a Stability Management Control, has been designed and developed. The Distortion Estimation System uses a small number of high-response pressure sensors at the engine face to calculate indicators of the type and extent of distortion in real time. The Stability Management Control, through direct control of the fan and compressor pressure ratio, accommodates the distortion by transiently increasing the amount of stall margin available based on information from the Distortion Estimation System. Simulation studies have shown the HISTEC distortion tolerant control is able to successfully estimate and accommodate time-varying distortion. Currently, hardware and software systems necessary for flight demonstration of the HISTEC concept are being designed and developed. The HISTEC concept will be flight tested in early 1997.

DeLaat, John C.; Southwick, Robert D.; Gallops, George W.

1996-01-01

404

Selection indices to identify drought-tolerant grain sorghum cultivars.  

PubMed

Twenty-five cultivars of grain sorghum [Sorghum bicolor (L.) Moench] were examined under both drought stress and normal conditions in 4 experiments. In each condition, genotypes were evaluated in a factorial experiment using a randomized complete block design with 3 replications. Eight drought tolerance indices including stability tolerance index, mean productivity (MP), geometric MP, harmonic mean, stress susceptibility index, tolerance index, yield index, and yield stability index were estimated for each genotype based on grain yield under drought (Ys) and irrigated conditions (Yp). The results indicated that there were positive and significant correlations among Yp and Ys with geometric MP, MP, harmonic mean, and stability tolerance index, indicating that these factors are better predictors of Yp and Ys than tolerance index, stress susceptibility index, yield stability index, and yield index. Based on adjusted means at Yp and Ys, indices geometric MP, MP, harmonic mean, and stability tolerance index, unweighted pair group method with arithmetic mean cluster and biplot analysis, the most tolerant cultivars were '9929020', '9929034', and 'N 95B'. PMID:25501191

Menezes, C B; Ticona-Benavente, C A; Tardin, F D; Cardoso, M J; Bastos, E A; Nogueira, D W; Portugal, A F; Santos, C V; Schaffert, R E

2014-01-01

405

Workshop on Feedback Stabilization of MHD Stabilities  

SciTech Connect

The feedback stabilization of MHD instabilities is an area of research that is critical for improving the performance and economic attractiveness of magnetic confinement devices. A Workshop dedicated to feedback stabilization of MHD instabilities was held from December 11-13, 1996 at the Princeton Plasma Physics Laboratory, Princeton NJ, USA. The resulting presentations, conclusions, and recommendations are summarized.

McGuire, K.; Kugel, H. [Princeton Univ., NJ (United States). Plasma Physics Lab.; La Haye, R. [General Atomics, San Diego, CA (United States); Mauel, M. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics; Nevins, W. [Lawrence Livermore National Lab., CA (United States); Prager, S. [Wisconsin Univ., Madison, WI (United States). Dept. of Physics

1996-12-31

406

Relationship Stability through Lenses of Complexity  

PubMed Central

Research on relationship stability usually considers the effect of couple outcomes and individual differences on relationship stability in isolation from each other. These separate bodies of research often lead to inconsistent results. In order to better understand relationship stability and explain inconsistencies in the literature, it is important to investigate more complex models that integrate couple outcomes and behaviors with individual differences. Motivated by these considerations, we examined the complex interplay between personal characteristics, couple interactions, and relationship stability. In particular, we investigated the relationships among investment model, big five personality traits, attachment dimensions, relationship factors and relationship stability. Participants of this study included 162 individuals (Female N=117) who are currently in a relationship from a large Midwestern university campus. Analyses were conducted using Structural Equation Modeling. Examination of the structural path parameters indicated that attachment had significant direct effect on personality, relationship factors, and relationship stability. Personality also had a significant direct effect on relationship stability. Finally personality had no direct effect on relationship factors and relationship factors had no direct effect on relationship stability. These results suggest that the effect of personality on relationship stability is direct, rather than being mediated by relationship factors. PMID:23124824

Karakurt, Gunnur

2012-01-01

407

Evidence for isomerization in myotoxin a from the prairie rattlesnake (Crotalus viridis viridis).  

PubMed

Myotoxin a, from the venom of the prairie rattlesnake, Crotalus viridis viridis, exists as a temperature-dependent equilibrium of two interconverting forms. Reverse-phase high-performance liquid chromatography (RP-HPLC) shows that the two forms interconvert slowly enough at 25 degrees C to be seen as two separate peaks with a molar ratio of c. 1:4. Each peak can be isolated and individually injected to give the same two peaks in the same ratio of areas. The two peaks merge during chromatography at elevated temperatures, indicating an increase in the rate of interconversion. At low temperature, c. 5 degrees C, the individual peaks can be isolated and maintained for several days without reaching equilibrium. Mass analysis by matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometry shows that myotoxin a is present in both RP-HPLC peaks, suggesting that the two resolved forms are conformational isomers. Capillary zone electrophoresis (CZE) also shows two resolved, but interconvertible peaks over a range of pH values. Furthermore, RP-HPLC chromatograms of myotoxin a at concentrations from 0.013 mM to 0.41 mM maintain a consistent ratio of peak areas, without evidence of dimerization. Two-dimensional 1H-NMR nuclear Overhauser enhancement spectroscopy indicates the presence of a cis-proline peptide bond, consistent with an equilibrium mixture of cis-trans isomers; however, addition of peptidyl-prolyl cis-trans isomerase (PPI) does not enhance the rate of equilibration of the RP-HPLC peaks isolated at c. 5 degrees C. PMID:8735241

O'Keefe, M P; Nedelkov, D; Bieber, A L; Nieman, R A

1996-04-01

408

Illustrating Chemiluminescence with Siloxene Indicator.  

ERIC Educational Resources Information Center

Discusses the nature of light-producing reactions and provides a procedure for demonstrating chemical luminescence using siloxene indicator. Indicates source of this chemical and safety precautions. (SK)

Hoff, Ray

1981-01-01

409

Delamination-Indicating Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

The risk of premature failure of thermal barrier coatings (TBCs), typically composed of yttria-stabilized zirconia (YSZ), compromises the reliability of TBCs used to provide thermal protection for turbine engine components. Unfortunately, TBC delamination proceeds well beneath the TBC surface and cannot be monitored by visible inspection. Nondestructive diagnostic tools that could reliably probe the subsurface damage state of TBCs would alleviate the risk of TBC premature failure by indicating when the TBC needs to be replaced before the level of TBC damage threatens engine performance or safety. To meet this need, a new coating design for thermal barrier coatings (TBCs) that are self-indicating for delamination has been successfully implemented by incorporating a europium-doped luminescent sublayer at the base of a TBC composed of YSZ. The luminescent sublayer has the same YSZ composition as the rest of the TBC except for the addition of low-level europium doping and therefore does not alter TBC performance.

Eldridge, Jeffrey I.

2007-01-01

410

Driving stability of superconducting magnetic bearing system  

NASA Astrophysics Data System (ADS)

A superconducting bearing system including a 7.5 kg disc shaped rotor is stabilized by using superconducting and magnetic levitation combination. The rotor is stabilized with the Evershed type bearing where the majority of the rotor mass is lifted via attractive permanent magnets configuration, and the stability of the rotor is provided by superconductors. The stability tests are performed via obtaining levitation force characteristic. Preliminary levitation force results show that the system is stable and robust; indicating rotor mass can be increased more without losing the efficiency. Dynamic tests are performed during spin of the designed bearing system. The resonance behavior of the system indicates that the bearing is not vulnerable to higher speeds.

Cansiz, Ahmet; Oral, Emin Argun; Gundogdu, Omer

2012-06-01

411

FLIR stabilization study  

Microsoft Academic Search

Precision pipeline correlation has been shown to be a superior method for stabilizing FLIR imagery. A pipeline correlation stabilization module provides better performance than gyro transducers, is inherently tuned to image parameters, can be remotely located from the sensor and can be used for passive or active stabilization of the image. In addition, the pipeline correlation module will provide edge

D. Defoe; T. Goodrich; J. Martin; C. Schleifer

1982-01-01

412

Automatic Stability of Airplanes  

NASA Technical Reports Server (NTRS)

It is endeavored in this report to give a full outline of the problem of airplane stability and to classify the proposed solutions systematically. Longitudinal stability, which can be studied separately, is considered first. The combination of lateral and directional stabilities, which cannot be separated, will be dealt with later.

Haus, FR

1932-01-01

413

Food Fortification Stability Study  

NASA Technical Reports Server (NTRS)

NASA has established the goal of traveling beyond low-Earth orbit and extending manned exploration to Mars. The extended length of a Mars mission, along with the lack of resupply missions increases the importance of nutritional content in the food system. The purpose of this research is to assess the stability of vitamin supplementation in traditionally processed spaceflight foods. It is expected that commercially available fortificants will remain stable through long-duration missions if proper formulation, processing, and storage temperatures are all achieved. Five vitamins (vitamin E, vitamin K, pantothenic acid, folic acid, and thiamin) were blended into a vitamin premix (DSM, Freeport, TX); premixes were formulated to be compatible with current processing techniques (retort or freeze-dried), varied water activities (high or low), and packaging material. The overall goal of this process is to provide 25% of the recommended daily intake of each vitamin (per serving), following processing and two years of ambient storage. Four freeze-dried foods (Scrambled Eggs, Italian Vegetables, Potatoes Au Gratin, Noodles and Chicken) and four thermostabilized foods (Curry Sauce with Vegetables, Chicken Noodle Soup, Grilled Pork Chop, Rice with Butter) were produced (with and without the vitamin premix), to assess the impact of the added fortificant on color and taste, and to determine the stability of supplemental vitamins in spaceflight foods. The use of fortification in spaceflight foods appears to be a plausible mitigation step to inadequate nutrition. This is due to the ease of vitamin addition as well as the sustainability of the premixes through initial processing steps. Postprocessing analysis indicated that vitamin fortification with this premix did not immediately impact organoleptic properties of the food. At this stage, the largest hurdle to fortification is the preciseness to which vitamins can be added; the total amount of vitamins required for production is 10 - 20 grams, a minor percentage of the formulation. As demonstrated by the over-fortification measured in Italian Vegetables and Grilled Pork Chop, homogeneity may be difficult to achieve with such small amounts. Thus, pouch-to-pouch variability, over-fortification, and underfortification may ensue if a method for precise addition is not identified. Stability will continue to be evaluated over two years of storage at three temperatures, and future analysis should reveal the extent to which this issue should be a concern

Abdulmalik, T. O.; Cooper, M. R.; Douglas, G. L.

2015-01-01

414

CONFIDENTIAL INDICATOR/NO PRINT INDICATOR Georgia Institute of Technology  

E-print Network

CONFIDENTIAL INDICATOR/NO PRINT INDICATOR Georgia Institute of Technology Registrar's Office, Atlanta GA 30332-0315 Fax 404-894-0167 "CONFIDENTIAL" INDICATOR ­ (Option A) Checking the "Confidential records are "confidential" each time your record is viewed. Your name and associated information

Weber, Rodney

415

Feedback stabilization initiative  

SciTech Connect

Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes.

NONE

1997-06-01

416

Parafermion stabilizer codes  

E-print Network

We define and study parafermion stabilizer codes which can be viewed as generalizations of Kitaev's one dimensional model of unpaired Majorana fermions. Parafermion stabilizer codes can protect against low-weight errors acting on a small subset of parafermion modes in analogy to qudit stabilizer codes. Examples of several smallest parafermion stabilizer codes are given. A locality preserving embedding of qudit operators into parafermion operators is established which allows one to map known qudit stabilizer codes to parafermion codes. We also present a local 2D parafermion construction that combines topological protection of Kitaev's toric code with additional protection relying on parity conservation.

Utkan Güngördü; Rabindra Nepal; Alexey A. Kovalev

2014-10-29

417

Investigating step-pool sequence stability  

NASA Astrophysics Data System (ADS)

Step-pool units, common features in steep, narrow streams, are highly dynamic systems that adjust during high flows and active sediment transport conditions. Consecutive step pools in a reach form a step-pool sequence, and though these features are prevalent in nature, quantifying the stability of such systems is challenging. This study focuses on the statistical relationships between 445 stable sequences of three or more steps and nine geometric and resistance-based parameters. Step sequence stability is parameterized through a sequence stability parameter, a metric of how long a given step-pool sequence exists relative to the total run time. Despite variability in the strength of the statistical relationships, the results allow identification of dominant trends between sequence stability and both roughness and geometric parameters. The sediment concentration ratio provides a means for comparing the relative strength of these statistical relationships. As sediment concentration ratios increase, the relations between flow resistance parameters and step stability change from dominantly inverse to dominantly direct. Thus, at higher sediment concentration ratios, sequence stability is more likely to increase with flow resistance, but the reverse is more likely at low sediment concentration ratios. A connection exists between bed morphology, flow resistance, and stability. For the majority of stable step sequences, resistance parameters increase over time, indicating some sequences adjust their geometry to increase stability during flood events. The influence of sediment concentration over the stability-geometric and stability-resistance parameter relationships may enable the use of the sediment concentration ratio as a predictor of step sequence stability during a flow event.

Waters, Kevin A.; Curran, Joanna Crowe

2012-07-01

418

Investigating step-pool sequence stability  

NASA Astrophysics Data System (ADS)

Step-pool units, common features in steep, narrow streams, are highly dynamic systems that adjust during high flows and active sediment transport conditions. Consecutive step-pools in a reach form a step-pool sequence, and though these features are prevalent in nature, quantifying the stability of such systems is challenging. This study focuses on the statistical relationships between 445 stable sequences of three or more steps and nine geometric and resistance based parameters. Step sequence stability is parameterized through a sequence stability parameter, a metric of how long a given step-pool sequence exists relative to the total run time. Despite variability in the strength of the statistical relationships, the results allow identification of dominant trends between sequence stability and both roughness and geometric parameters. The sediment concentration ratio provides a means for comparing the relative strength of these statistical relationships. As sediment concentration ratios increase, the relations between flow resistance parameters and step stability change from dominantly inverse to dominantly direct. Thus, at higher sediment concentration ratios, sequence stability is more likely to increase with flow resistance, but the reverse is more likely at low sediment concentration ratios. A connection exists between bed morphology, flow resistance, and stability. For the majority of stable step sequences, resistance parameters increase over time, indicating some sequences adjust their geometry to increase stability during flood events. The influence of sediment concentration over the stability-geometric and stability-resistance parameter relationships may enable the use of sediment concentration ratio as a predictor of step sequence stability during a flow event.

Waters, K. A.; Curran, J. C.

2012-12-01

419

Edible Acid-Base Indicators.  

ERIC Educational Resources Information Center

Reports on the colors observed during titrations of 15 natural indicators obtained from common fruits and vegetables. These edible indicators can be used for a variety of teacher demonstrations or for simple student experiments. (JN)

Mebane, Robert C.; Rybolt, Thomas R.

1985-01-01

420

A study of the anti-plasmodium activity of angiotensin II analogs.  

PubMed

Controlling the dissemination of malaria requires the development of new drugs against its etiological agent, a protozoan of the Plasmodium genus. Angiotensin II and its analog peptides exhibit activity against the development of immature and mature sporozoites of Plasmodium gallinaceum. In this study, we report the synthesis and characterization of angiotensin II linear and cyclic analogs with anti-plasmodium activity. The peptides were synthesized by a conventional solid-phase method on Merrifield's resin using the t-Boc strategy, purified by RP-HPLC and characterized by liquid chromatography/ESI (+) MS (LC-ESI(+)/MS), amino acid analysis, and capillary electrophoresis. Anti-plasmodium activity was measured in vitro by fluorescence microscopy using propidium iodine uptake as an indicator of cellular damage. The activities of the linear and cyclic peptides are not significantly different (p?indicate that the effects of these peptides on plasmodium viability overtime exhibit a sigmoidal profile and that the system stabilizes after a period of 1?h for all peptides examined. The results were rationalized by partial least-square analysis, assessing the position-wise contribution of each amino acid. The highest contribution of polar amino acids and a Lys residue proximal to the C-terminus, as well as that of hydrophobic amino acids in the N-terminus, suggests that the mechanism underlying the anti-malarial activity of these peptides is attributed to its amphiphilic character. PMID:23893516

Chamlian, Mayra; Bastos, Erick L; Maciel, Ceres; Capurro, Margareth L; Miranda, Antonio; Silva, Adriana F; Torres, Marcelo Der T; Oliveira, Vani X

2013-09-01

421

Social Indicators and Social Forecasting.  

ERIC Educational Resources Information Center

The paper identifies major types of social indicators and explains how they can be used in social forecasting. Social indicators are defined as statistical measures relating to major areas of social concern and/or individual well being. Examples of social indicators are projections, forecasts, outlook statements, time-series statistics, and…

Johnston, Denis F.

422

Educational Indicators and Enlightened Policy  

Microsoft Academic Search

This article examines how educational indicators have been and may be used to serve educational policy ends, what the potential benefits and dangers are of various uses, and how guidelines for appropriate relationships between indicators and policy might be forged. The article draws particular attention to recent debates and difficulties in fashioning a constructive role for educational indicators—a role that

Linda Darling-Hammond

1992-01-01

423

Hydrostratigraphic interpretation using indicator geostatistics  

Microsoft Academic Search

In this paper we describe an approach that uses indicator geostatistics to interpret qualitative borehole logs and compute experimental variograms for complex alluvial sediments. Borehole descriptions are first transformed into binary indicator values based on inferred relative permeability from the borehole descriptions. The resulting indicator data can then be used to compute variograms and construct three-dimensional variogram models. The ranges

Nicholas M. Johnson; Shirley J. Dreiss

1989-01-01

424

Gas turbine combustor stabilization by heat recirculation  

NASA Technical Reports Server (NTRS)

The feasibility of heat recirculation for stabilization of lean mixtures and emission reduction has been studied in detail for a typical aircraft gas turbine combustor. Thermodynamic calculations have indicated temperature and heat recirculation rates for operation of the combustor over a range of combustion zone equivalence ratios and for varying modes of desired engine operation. Calculations indicate the feasibility of stabilizing the combustion zone at equivalence ratios as low as 0.2 with achievable heat recirculation rates. Detailed chemical kinetic calculations suggest that combustor heat release is maintained with reaction completion substantially before the NO forming reactions, even though CO is rapidly oxidized in this same region.

Ganji, A.; Short, J.; Branc