Determination of etoricoxib in human plasma using automated on-line solid-phase extraction coupled with LC-APCI/MS/MS

A liquid chromatography-tandem mass spectrometry method with atmospheric pressure chemical ionization (LC-APCI/MS/MS) was validated for the determination of etoricoxib in human plasma using antipyrin as internal standard, followed by on-line solid-phase extraction. The method was performed on a Luna C18 column and the mobile phase consisted of acetonitrile:water (95:5, v/v)/ammonium acetate (pH 4.0; 10 mM), run at a flow rate of 0.6 mL/min. The method was linear in the range of 1-5000 ng/mL (r²>0.99). The lower limit of quantitation was 1 ng/mL. The recoveries were within 93.72-96.18%. Moreover, method validation demonstrated acceptable results for the precision, accuracy and stability studies.

Performance characteristics of bioassay UV-spectrophotometry and high perfomance liquid chromatographic determination of gatifloxacin in tablets

The microbiological bioassay, UV-spectrophotometry and HPLC methods for assaying gatifloxacin in tablets were compared. Validation parameters such as linearity, precision, accuracy, limit of detection and limit of quantitation were determined. Beer's law was obeyed in the ranges 4.0-14.0 μg/mL for HPLC and UV-spectrophotometric method, and 4.0-16.0 μg/mL for bioassay. All methods were reliable within acceptable limits for antibiotic pharmaceutical preparations being accurate, precise and reproducible. The bioassay and HPLC are more specific than UV-spectrophotometric analysis. The application of each method as a routine analysis should be investigated considering cost, simplicity, equipment, solvents, speed, and application to large or small workloads.

Development and validation of a GC-FID assay for determination of fluvastatin in pharmaceutical preparations

A gas chromatographic method has been developed for the assay of fluvastatin sodium (FLU). FLU was silylated with N,O-bis(trimethylsilyl)trifluoroacetamide-1% trimethylchlorosilane at 90 ºC for 30 min and analysed in a DB-1 column by capillary gas chromatograph with a flame ionization detector. The method was validated. The assay was linear over the concentration range at 10.0 to 50.0 µg mL-1. The limit of detection and the limit of quantitation were 1.0 and 3.0 µg mL-1, respectively. The recoveries of FLU derivatives were in the range of 99.25-99.80%. In inter-day and intra-day analysis, the values of relative standard deviation (%) and the relative mean error (%) were found between 0.20-0.80% and -0.20-0.75%, respectively. The developed method was succesfully applied to analyze the FLU content in tablet formulation. The results were statistically compared with those obtained by the official method, and no significant difference was found between the two methods. Therefore, it can be recommended for the quality control assay of FLU in pharmaceutical industry.

Development and validation of UV spectrophotometric method for determination of levofloxacin in pharmaceutical dosage forms

The objective of this research was to develop and validate an alternative analytical method for quantitative determination of levofloxacin in tablets and injection preparations. The calibration curves were linear over a concentration range from 3.0 to 8.0 μg mL-1. The relative standard deviation was below 1.0% for both formulations and average recovery was 101.42 ± 0.45% and 100.34 ± 0.85% for tablets and injection formulations, respectively. The limit of detection and limit of quantitation were 0.08 and 0.25 μg mL-1, respectively. It was concluded that the developed method is suitable for the quality control of levofloxacin in pharmaceuticals formulations.

UV derivative spectrophotometric method for determination of estradiol valerate in tablets

A derivative UV spectrophotometric method for determination of estradiol valerate in tablets was validated. The parameters specificity, linearity, precision, accuracy, limit of detection and limit of quantitation were studied according to validation guidelines. The first-order derivative spectra were obtained at N = 5, Δλ = 4.0 nm, and determinations were made at 270 nm. The method showed specificity and linearity in the concentration range of 0.20 to 0.40 mg mL-1. The intra and interday precision data demonstrated the method has good reproducibility. Accuracy was also evaluated and results were satisfactory. The proposed method was successfully applied to a pharmaceutical formulation.

Performance characteristics of high performance liquid chromatography, first order derivative UV spectrophotometry and bioassay for fluconazole determination in capsules

The bioassay, first order derivative UV spectrophotometry and chromatographic methods for assaying fluconazole capsules were compared. They have shown great advantages over the earlier published methods. Using the first order derivative, the UV spectrophotometry method does not suffer interference of excipients. Validation parameters such as linearity, precision, accuracy, limit of detection and limit of quantitation were determined. All methods were linear and reliable within acceptable limits for antibiotic pharmaceutical preparations being accurate, precise and reproducible. The application of each method as a routine analysis should be investigated considering cost, simplicity, equipment, solvents, speed, and application to large or small workloads.

Determination of fipronil in bovine plasma by solid-phase extraction and liquid chromatography with ultraviolet detection

A fast and efficient method has been developed and validated for the determination of fipronil in bovine plasma. Samples were subjected to solid-phase extraction (SPE) followed by reversed phase liquid chromatography (LC) separation, using acetonitrile/water (60:40 v/v) as the mobile phase with a flow rate of 1.0 mL/min and ultraviolet (UV) detection at 210 nm. Ethiprole was used as the internal standard (IS). The method was found to be linear over the range 5-500 ng/mL (r = 0.999). The limit of quantitation (LOQ) was validated at 5 ng/mL. The method was successfully applied to monitor plasma concentrations following subcutaneous administration of fipronil in cattle.

Strong-segregation limit of the self-consistent field theory for diblock copolymer melts

The self-consistent field theory (SCFT) introduced by Helfand for diblock copolymer melts is expected to converge to the strong-segregation theory (SST) of Semenov in the asymptotic limit, $\chi N \rightarrow \infty$. However, past extrapolations of the lamellar/cylinder and cylinder/sphere phase boundaries, within the standard unit-cell approximation, have cast some doubts on whether or not this is actually true. Here we push the comparison further by extending the SCFT calculations to $\chi N = 512,000$, by accounting for exclusion zones in the coronae of the cylindrical and spherical unit cells, and by examining finite-segregation corrections to SST. In doing so, we provide the first compelling evidence that SCFT does indeed reduce to SST.

The long wavelength limit of hard thermal loop effective actions

We derive a closed form expression for the long wavelength limit of the effective action for hard thermal loops in an external gravitational field. It is a function of the metric, independent of time derivatives. It is compared and contrasted with the static limit, and with the corresponding limits in an external Yang-Mills field. (C) 2009 Elsevier B.V. All rights reserved.

Development and Validation of a Mice liar Electrokinetic Chromatography Method for Quantitative Determination of Butenolides in Piper malacophyllum (C. Presl) C. DC.

Introduction - A large number of natural and synthetic compounds having butenolides as a core unit have been described and many of them display a wide range of biological activities. Butenolides from P. malacophyllum have presented potential antifungal activities but no specific, fast, and precise method has been developed for their determination. Objective - To develop a methodology based on micellar electrokinetic chromatography to determine butenolides in Piper species. Methodology - The extracts were analysed in an uncoated fused-silica capillaries and for the micellar system 20 mmol/L SDS, 20% (v/v) acetonitrile (ACN) and 10 mmol/L STB aqueous buffer at pH 9.2 were used. The method was validated for precision, linearity, limit of detection (LOD) and limit of quantitation (LOQ) and the standard deviations were determined from the standard errors estimated by the regression line. Results - A micellar electrokinetic chromatography (MEKC) method for determination of butenolides in extracts gave full resolution for 1 and 2. The analytical curve in the range 10.0-50.0 mu g/mL (r(2) = 0.999) provided LOD and LOQ for 1 and 2 of 2.1/6.3 and 1.1/3.5 mu g/mL, respectively. The RSD for migration times were 0.12 and 1.0% for peak area ratios with 100.0 +/- 1.4% of recovery. Conclusions - A novel high-performance MEKC method developed for the analysis of butenolides 1 and 2 in leaf extracts of P. malacophyllum allowed their quantitative determined within an analysis time shorter than 5 min and the results indicated CE to be a feasible analytical technique for the quantitative determination of butenolides in Piper extracts. Copyright (C) 2010 John Wiley & Sons, Ltd.

Development of a Validated Stability-Indicating LC Assay and Stress Degradation Studies of Linezolid in Tablets

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

LC Evaluation of Intestinal Transport of Praziquantel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Development of practical HPLC methods for the separation and determination of eggplant steroidal glycoalkaloids and their aglycones

A practical set of HPLC methods was developed for the separation and determination of the eggplant steroidal glycoalkaloids, solanine, chaconine, solasonine, solamargine, and their aglycones, solasodine and solanidine. A gradient method was initially developed, but proved to be neither robust nor practical. Three separate isocratic methods using acetonitrile and ammonium dihydrogen phosphate were developed and shown to be more repeatable, less subject to fluctuations in mobile phase composition, and less time consuming. The effect of adjusting buffer pH, column temperature, and buffer type (triethylammonium phosphate vs. ammonium dihydrogen phosphate) were evaluated. It was also discovered that, by addition of 10% methanol to the acetonitrile portion of the mobile phase, more control over the separations was possible. The use of methanol as a mobile phase entrainer greatly improved separations in some cases and its effectiveness was also dependent upon column temperature. Assessments of the method recovery, limit of detection, and limit of quantitation were made using extracts from S. melongena and S. linnaeanum.