Gas chromatographic assay of diethylcarbamazine in human plasma for application to clinical pharmacokinetic studies

A sensitive and selective gas chromatography method using flame ionization detection was developed for the determination of diethylcarbamazine (DEC) i n human plasma. DEC and the internal standard, 1-diethylcarbamyl-4-ethyl pi perazine HCl (E-DEC). were extracted from human plasma after loading onto a conditioned C-18 solid phase extraction cartridge, rinsed with water and e luted with methanol. After evaporation under a stream of nitrogen and recon stitution in methanol, 3 mul were injected onto the GC system. Separation w as achieved on a A Heliflex(R) AT-35 capillary column (length 30 m, interna l diameter 0.32 mm). Gas flow rates were: hydrogen, 35 ml/min; carrier gas (helium), 1.5 ml/min, make-up gas (helium), 25 ml/min; and air 420 ml/min. The retention times of DEC and internal standard were approximately 5.5 and 7.28 min, respectively. The GC run time was 22 min. The assay was linear i n concentration range 100-2000 ng/ml for DEC in human plasma. The analysis of quality control samples for DEC (120, 1000. 2000 ng/ml) demonstrated exc ellent precision with coefficients of variation of 4.5, 1.3, and 1.6%, resp ectively (n = 6), The method was accurate with all intra-day (n = 6) and in ter-day (n = 12) mean concentrations within 4.3% from nominal at all qualit y control sample concentrations. DEC was found to be stable after 3 freeze- thaw cycles, and with storage at -20 degreesC for 12 weeks. The method is c urrently being used for pharmacokinetic studies of DEC in healthy volunteer s. (C) 2001 Elsevier Science B.V. All rights reserved.