METHODS FOR THE MEASUREMENT OF BENZODIAZEPINES IN BIOLOGICAL SAMPLES

A review of methods for the measurement of benzodiazepines in biologic al specimens published over the last five years is presented. A range of immunoassay procedures using EIA, ELISA, FPLA, agglutination or kin etic interaction of microparticles, or RIA methods are now available. Cross reactivities to benzodiazepines are variable such that no one ki t will recognise all benzodiazepines and their relevant metabolites at concentrations Likely to be encountered during therapeutic use. Prior hydrolysis of urine to convert glucuronide metabolites to immunoreact ive substances improves detection limits for many benzodiazepines. Sev eral radioreceptor assays have now been published and show good sensit ivity and specifity to benzodiazepines and offer the advantage (over i mmunoassay) of being able to detect these drugs with equal sensitivity . Solvent extraction techniques using a variety of solvents were still popular and offer acceptable recoveries and lack of significant inter ference from other substances. A number of papers describing solid pha se extraction procedures were also published. Direct injection of spec imens into a HPLC column with back flushing were also successfully des cribed. Seventy two chromatographic methods using HPLC, LC-MS, GC and CC-MS methods were reviewed. HPLC was able to achieve detection limits for many benzodiazepines using UV or DAD detection down to 1-2 ng/ml using 1-2 mi of urine or serum (blood). ECD detectors gave detection l imits better than 1 ng/ml from 1 mi of specimen, which was an order of magnitude lower than for NPD. EI-MS offered similar sensitivity, whil st NCI-MS was capable of detection down to 0.1 ng/ml. Methods suitable for the separation of enantiomers of benzodiazepines have been descri bed using HPLC. Electrokinetic micellar chromatography has also been s hown to be capable of the analysis of benzodiazepines in urine. (C) 19 98 Elsevier Science B.V. All rights reserved.