Determination of pyrrolidinone in plasma by high-performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic method for the determination of pyrrolidinone (I) in plasma is described. Compound I was extracted from plasma with methylene chloride using kieselguhr as aqueous phase support. The gamma-aminobutyric acid (II) formed after alkaline hydrolysis of I was derivatised with o-phthalaldehyde, chromatographed on a reversed-phase column, and quantified by fluorescence detection. The limit of quantification was 2.5 ng/ml (intra-assay R.S.D. 5%) using a 1-ml plasma sample. The inter-assay precision was 3-14% (R.S.D.) over the concentration range 2000-5 ng/ml, and the recovery from plasma was quantitative (99.3 +/- 2.9%). The accuracy of this method was established from the good agreement between the values obtained after the analysis of plasma samples by both this method and a gas chromatography--mass spectrometry method. The high-performance liquid chromatographic procedure was applied to the determination of (a) endogenous I in human plasma samples and (b) I in plasma following intravenous administration of this substance to a dog. In twelve human subjects, endogenous concentrations of I of 8.3 +/- 2.3 ng/ml (gas chromatography--mass spectrometry method: 6.1 +/- 2.6 ng/ml) were found.