Determination of diltiazem and its main metabolites in human plasma by automated solid-phase extraction and high-performance liquid chromatography: a new method overcoming instability of the compounds and interference problems

An automated sample preparation method, based on solid-phase extraction (SPE) was developed on an ASPEC-Gilson device and combined with HPLC for the determination of diltiazem and three of its metabolites in human plasma (N-desacetylmonodesmethyldiltiazem, N-monodesmethyldiltiazem, O-desacetyldiltia...

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Bibliographic Details
Published in:Journal of chromatography. B, Biomedical applications Biomedical applications, 1994-07, Vol.657 (1), p.133-140
Main Authors: Ascalone, V, Locatelli, M, Malavasi, B
Format: Article
Language:English
Subjects:
Acetylation
Autoanalysis
Chromatography, High Pressure Liquid - methods
Chromatography, High Pressure Liquid - statistics & numerical data
Diltiazem - blood
Diltiazem - chemistry
Diltiazem - pharmacokinetics
Drug Stability
Humans
Methylation
Molecular Structure
Quality Control
Sensitivity and Specificity
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Summary:An automated sample preparation method, based on solid-phase extraction (SPE) was developed on an ASPEC-Gilson device and combined with HPLC for the determination of diltiazem and three of its metabolites in human plasma (N-desacetylmonodesmethyldiltiazem, N-monodesmethyldiltiazem, O-desacetyldiltiazem). A 1-ml volume of plasma is diluted with 0.5 ml of 0.1 M ammonium dihydrogen phosphate and the sample is automatically loaded onto a SPE silica (C18) column (100 mg); the column is flushed with two different solvents, then eluted with 0.5 ml of a 0.1 M ammonium dihydrogen phosphate-acetonitrile mixture (20:80, v/v) containing 0.06% of triethylamine. The eluate is evaporated to dryness and the residue reconstituted with a suitable solvent and injected onto a C8 silica column connected to a UV detector (lambda = 238 nm). This method overcomes problems caused by the partial instability of diltiazem and metabolites in human plasma during analysis. There is no chromatographic interference from endogenous compounds. The limits of quantitation (LOQ) are 2.5 and 2 ng ml-1 for diltiazem and the metabolites in human plasma, respectively. Linearity between concentrations and detector response for diltiazem and metabolites ranged from 10-200 and 5-100 ng ml-1 in human plasma, respectively. The method has been validated.
ISSN:1572-6495