Determination of citalopram enantiomers in human plasma by liquid chromatographic separation on a Chiral-AGP column.

A liquid chromatographic method for the quantitative analysis of S-(+)- and R-(-)-citalopram in human plasma has been developed and validated. The enantiomers of citalopram and the internal standard, R-(+)-propranolol, were extracted from alkaline plasma with 2% n-butanol in n-hexane. After a clean-up step, the organic phase was evaporated and the residues dissolved in 50-100 microliters of 0.001 M HCl. The separation was performed on a Chiral-AGP column with 3.0 mM N-dodecyl-N,N-dimethylammonio-3-propanesulfonate and 10 mM hexanoic acid in phosphate buffer pH 6.5 as the mobile phase. The limit of detection was estimated to be 1 ng/ml (S/N approximately equal to 3) for each enantiomer monitoring UV absorption at 240 nm. In the range studied, 2.31-191 ng/ml, the recoveries were quantitative and the coefficients of variations were between 2.47% and 11.5%.