Direct analysis of clomipramine in human plasma by microbore high performance liquid chromatography with column-switching

An automated microbore, liquid chromatographic method with column-switching was developed for the determination of clomipramine from human plasma samp les. After direct injection of samples (60 mu L), plasma proteins and clomi pramine were separated in size-exclusion mode using 20 % acetonitrile in 20 mM phosphate buffer (pH 7.0) on Capcell Pak MF Ph-1 precolumn (10 x 4 mm I .D.). By valve switching, a fraction containing clomipramine was directed t o an intermediate column for subsequent main separation on a microbore C-18 column (250 X 1.5 mm I.D.) using 50 % acetonitrile in 20 mM phosphate buff er (pH 2.5) at 0.1 mL min(-1). The method was advantageous for rapidity (to tal analysis time: 15min), reproducibility (C.V. < 4.8 %), and increased se nsitivity (1 ng mL(-1)). The linearity of response was good (r(2) greater t han or equal to 0.999) over the concentration range 1-250 ng mL(-1.)