Analysis of antibiotics by gas chromatography. 3. Griseofulvin

Development and validation of a HPLC method to determine griseofulvin in rat plasma: application to pharmacokinetic studies

A simple, specific, sensitive, and rapid high performance liquid chromatography (HPLC) method for the determination of griseofulvin in small volumes of rat plasma was developed and validated using warfarin as an internal standard. Biological sample preparation involved simple extraction with acetonitrile, followed by dilution with aqueous mobile phase buffer (20 mM sodium dihydrogen phosphate, pH 3.5) to eliminate any chromatographic solvent effects. Griseofulvin and warfarin were baseline separated and quantitated on a C₁₈ reversed phase column (4.6 × 150 mm, 3.5 μm), using a mobile phase composed of a 20 mM aqueous solution of sodium dihydrogen phosphate-acetonitrile (55:45, v/v, pH 3.5) delivered at a flow rate of 1.0 mL/min, and with fluorescence detection (λexcitation = 300 nm, λ_emission = 418 nm). The method was proven to be linear over a plasma griseofulvin concentration range of 10 to 2500 ng/mL with a mean correlation coefficient of 0.9996. The intra-day and inter-day accuracy (relative error) were in the range of 0.89% to 9.26% and 0.71% to 7.68%, respectively. The within-day precision (coefficient of variation) was less than 3.0% and the between-day precision was less than 7.5%. The mean recovery of griseofulvin from rat plasma was found to be 99.2%. The limit of detection (LOD) and the limit of quantification (LOQ) of griseofulvin were determined to be 1 ng/mL and 10 ng/mL, respectively. The developed method was successfully applied to quantitatively assess the pharmacokinetics of griseofulvin in rats following a single 50 mg/kg oral dose of the drug.

High-performance liquid chromatographic analysis of griseofulvin in drug substance and solid dosage forms: separation of impurities and metabolites

A high-performance liquid chromatographic (HPLC) system, consisting of a methanol-water (3:2 v/v) mobile phase and a Zorbax CN column with m-phenylphenol as the internal standard, was utilized to determine the purity of griseofulvin bulk drug substance, to assay griseofulvin in powders, tablets, capsules, and boluses, and to separate griseofulvin from its metabolites. The method was tested on commercial griseofulvin samples, griseofulvin tablets, and a mixture of griseofulvin and its metabolites. The HPLC method is compared to a GLC method.

GLC determination of N,N-dimethylaniline in penicillins

A reliable GLC procedure was developed for the determination of residual N,N-dimethylaniline as a contaminant in ampicillin commerical samples from various sources. The procedure was similarly applied to other penicillins and cephalosporins. The method involves dissolution of the sample in aqueous alkali, extraction of the organic base with cyclohexane containing naphthalene as an internal standard, and injection into gas chromatograph with a phenyl methyl silicone column. Levels of 0.1 ppm of dimethylaniline were easily measured with a coefficient of variation less than 10%, and recoveries from spiked samples exceeded 99%.

GLC analysis of griseofulvin: a collaborative study

A GLC method for the assay of griseofulvin in bulk and dosage forms was subjected to a wide and rigorous collaborative study. An overall recovery of 99.52 plus or minus 2.33% for three samples from 19 participating laboratories was obtained. The success of this study is ascribed to the fact that strict performance requirements are specified for the operating system.