New HPLC Method For Determination Research Articles

New HPLC Method for Determination of Cefquinome in Cattle Plasma and its Application for Pharmacokinetic Study

New HPLC Method for Determination of Cefquinome in Cattle Plasma and its Application for Pharmacokinetic Study

Facile HPLC/UV method for determination of metformin and 1-cyanoguanidine using novel halogenated stationary phase

Metformin is the most prescribed drug for diabetes. We aimed to develop a new HPLC method for determination of metformin and its main impurity 1-cyanoguanidine in raw material and its pharmaceutical tablets. The separation was achieved on pentabromobenzyl column using a mixture of 20% 10.0 mM phosphate buffer (pH 5.5) and 80% methanol as a mobile phase at a flow rate of 1.0 mL min-1 and UV detection at 227 nm. The analysis time was less than 4.0 minutes. The method was linear through concentration ranges of 3.0 – 80 µg mL-1 and 0.5 – 10 µg mL-1 and detection limits of 0.73 µg mL-1 and 0.11 µg mL-1 for metformin and 1-cyanoguanidine, respectively. The method was successfully applied for determination of metformin in bulk and pharmaceutical dosage forms. The high sensitivity of the developed method allowed for determination of 1-cyanoguanidine below its specified limits in metformin raw material and tablets.

A new HPLC Method for Determination of Carvedilol in Human Plasma and its Application in Bioequivalence Studies

A new HPLC Method for Determination of Carvedilol in Human Plasma and its Application in Bioequivalence Studies

A New HPLC Method for Determination of Ropinirole in Human Plasma and its Application in Bioequivalence Studies

A New HPLC Method for Determination of Ropinirole in Human Plasma and its Application in Bioequivalence Studies

Development of a New HPLC Method for Determination of Papaverine in Presence of Its Photooxidation Products

A new HPLC method was developed for determination of papaverine in a papaverine naturally photooxidized solution using a Duet C18/SCX column. The mobile phase used was a mixture of phosphate buffer (pH = 3.80) and acetonitrile in 40:60 ratio. The compounds identified were: papaverinol, papaveraldine, papaverine, and pyrrocolonium ion. Very good resolutions, peak shapes, and asymmetries were obtained. An ion exchange experiment was developed in order to identify and separate the pyrrocolonium ion. This was retained completely by a cation exchange resin in its Na+ form, while papaverine, papaverinol, and papaveraldine were retained more or less, due to a retention explained by a combined ion exchange-solvent extraction mechanism. Voltammetric studies showed that natural photooxidation of papaverine occurs in three irreversible steps and yields to stable compounds in solution.

Validation of a new HPLC method for determination of midazolam and its metabolites: Application to determine its pharmacokinetics in human and measure hepatic CYP3A activity in rabbits

Midazolam (MDZ) is a commonly used benzodiazepine in clinical practice. In addition, its metabolic oxidation is used as a surrogate marker for Cytochrome P450 (CYP) 3A enzyme activity as well. Thus, a new simpler method to measure MDZ and its metabolites is welcomed. Herein we report a new and simple HPLC method with ultraviolet detection for the simultaneous determination of midazolam and its hydroxyl metabolites using lorazepam as an internal standard. A liquid–liquid extraction was used to extract the compounds from rabbit hepatic microsomes and human plasma. The separation was performed on a Zorbax Eclipse XDB C 18 column using a mobile phase composed of 0.05 M Na 2PO 4 (pH 4.5) and acetonitrile mixture (67:33) pumped at 1.2 mL/min. The calibration curves showed good linearity with correlation coefficient higher than 0.999 for all analytes in the range 10–500 ng/mL. Accuracy in the measurement of quality control (QC) samples was in the range 95–106% of the nominal values. The intra-day and inter-day precisions in the measurement of QC samples were less than 11% coefficient of variation. Although less sensitive than GC–MS, the proposed method was adequately sensitive to measure midazolam hydroxylase activity as a marker for CYP3A activity, and was applied to measure midazolam pharmacokinetics in human plasma.

Development and validation of a new HPLC method for determination of lamotrigine and related compounds in tablet formulations

A simple HPLC method was developed and validated for quantitation of lamotrigine and its related substances which may coexist in solid pharmaceutical dosage forms. The HPLC separation was achieved on a C18 μ-Bondapack column (250 mm × 4.6 mm) using a mobile phase of acetonitrile–monobasic potassium phosphate solution (35:65, v/v) containing orthophosphoric acid to adjust pH to 3.5 at a flow rate of 1.5 ml/min. The UV detector was operated at 210 nm, and column temperature was adjusted at 40 °C. The method was validated for specificity, linearity, precision, accuracy, robustness and limit of quantitation. The degree of linearity of the calibration curves, the percent recoveries of lamotrigine and related substances, the limit of detection and quantitation, for the HPLC method were determined. The method was found to be simple, specific, precise, accurate, and reproducible. The method was applied for the quality control of commercial lamotrigine tablets to quantify the drug and its related substances and to check the formulation content uniformity.

Determination of thiopurine methyltransferase phenotype in isolated human erythrocytes using a new simple nonradioactive HPLC method.

Genetic polymorphism of the S-methylation pathway catalyzed by thiopurine methyltransferase (TPMT) is responsible for variation in the metabolism, toxicity, and therapeutic efficacy of thiopurine drugs. This paper describe a new simple, nonradioactive HPLC method for determination of TPMT activity in isolated erythrocytes (Ery), based on the conversion of 6-mercaptopurine (pH 7.5, 37 degrees C) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-l-methionine as methyl donor. The incubation step was stopped by a mixture of trichloroacetic acid/acetonitrile containing the internal standard 4-aminoacetophenone. 6-MMP was quantified by absorbance at 290 nm after chromatographic separation on a Zorbax SB-Phenyl column (5 microm, 4.6 x 250 mm) using mobile phases (flow rate 1.1 mL/min) consisting of acetonitrile, phosphate buffer pH 3.0, triethylamine, and dithiothreitol. The assay was linear up to 50 nmol/(mL Ery. h), and the detection limit was 0.3 nmol/(mL Ery. h). The extraction efficiency of 6-MMP was 95-103% (n = 3), and its analytic recovery ranged between 98.3% and 101.8% (n = 12). The within-day imprecision using pooled human erythrocytes (n = 12) was 4.4% at a TPMT activity of 14.3 nmol/(mL Ery.h) and 4.9% at 6.5 nmol/(mL Ery.h). The between-day imprecision (n = 12) was 6.8% and 7.5% nmol/(mL Ery.h), respectively. A very good agreement was found between TPMT activity determined with this method (y) and a widely used radiochemical procedure (x) (r = 0.94; n = 130; y = 0.502 + 0.946x; P < 0.05). Genotype analysis of all individuals with TPMT activity under 12.5 nmol/(mL Ery.h) revealed a genotype/phenotype concordance of 86%. The new HPLC method for determination of TPMT activity in Ery is a simple, rapid, and reliable nonradioactive procedure that can be successfully used for both research and routine clinical analysis.

Comparisons of home blood glucose testing and glycated protein measurements

We examined the relationships between 4 glycated protein assays and home blood glucose monitoring (HBGM) in 26 children with poorly-controlled insulin-dependent diabetes mellitus (IDDM) during a period of improved management. At 2 week intervals for 6 visits (12 weeks in total), HBGM records were collected and a blood sample was obtained for measurement of glycated proteins and glucose. Assays included glycated hemoglobin (GHb) and glycated serum proteins (GP) by boronate affinity chromatography, hemoglobin A 1C by PolyCAT A high performance liquid chromatography (HAC) and fructosamine (FA). All 4 glycated protein levels declined significantly over the 12 week period. Significant correlations between the glycated proteins and HBGM were observed over 2 week intervals. None of the 4 assays were affected by the glucose level in the sample. Changes in mean HBGM readings over 2 week intervals were correlated with both FA and GP with wide prediction intervals. Over cumulative 2 week intervals, which may more accurately reflect longitudinal trends, all 4 glycated proteins were correlated with mean HBGM readings. At each cumulative interval, GHb and GP showed the largest variation with MBG, while FA showed the least variation with MBG. Our data indicate that of the 4 assays tested, FA has limited clinical value as compared to other glycated protein assays, whereas assays based on boronate affinity chromatography (GHb and GP) provide the most useful clinical indicators of short-term changes in glycemic control. The clinical utility of a new HPLC method for determination of glycated hemoglobins is also demonstrated.

Studies on the stability of Kathon® CG/ICP Microbicide in alpha olefin sulfonate Based systems

AbstractKathon® CG/ICP Microbicide (Rohm &amp; Haas Co.) which contains 1.5% 5‐chloro‐2‐methyl‐4‐isothiazolin‐3‐one and 0.35% 2‐methyl‐4‐isothiazolin‐3‐one as active ingredients has been found to be a highly efficient antimicrobial preservative for formulated products. However, its use has been contra‐indicated for formulations containing certain anionic surfactants, especially AOS, because of the suspected presence of residual bisulfite ion added to remove residual hypochlorite remaining at the end of the bleaching process.It has been found that sulfite ion is not stable in the complex mixture of components in commercially produced AOS. AOS samples tested, whether bleached or not, contained residual reducing capacity, but of a sufficiently low redox potential as to not affect Kathon® CG/ICP Microbicide stability.Alternative analytical methods for analysis for bisulfite in AOS and other surfactant systems are discussed.A new HPLC method for determination of Kathon® CG/ICP Microbicide level in formulated products was developed.