Quantification of dimethindene in plasma by gas chromatography-mass fragmentography using ammonia chemical ionization.

A gas chromatographic-mass fragmentographic method using ammonia chemical ionization for the determination of dimethindene in human plasma is described. The drug was isolated from plasma by liquid-liquid extraction with hexane-2-methylbutanol. Plasma components were separated on a capillary column coated with chemically bonded methyl silicone. For detection of dimethindene, its quasi-molecular ion (M + H+) was mass fragmentographically monitored after chemical ionization with ammonia as reagent gas. Dimethindene was quantified using methaqualone as the internal standard: the quantification limit in plasma was 0.2 ng/ml, the within-run precision was 8.0% and the inter-run precision 5.6%. The plasma concentration-time profile was established after a single dose of 4 mg of dimethindene with an average maximum concentration of 5.5 ng/ml, detectable up to 48 h post application.