Non-aqueous capillary electrophoresis of biological samples after at-line solid-phase extraction

Solid-phase extraction (SPE) wets coupled at-line to capillary electrophore sis (CE) for the determination of a series of basic lest compounds (i.e. tr icyclic antidepressants). The analysis was performed using a non-aqueous CE buffer, which resulted in baseline separation of all test compounds. This is in marked contrast with CE using aqueous buffers where hardly any separa tion was obtained either with or without micelles. The SPE procedure was us ed to remove simultaneously most of the water from the sample, because no d irect analysis of aqueous samples is possible when a non-aqueous CE buffer is used. With the present method the antidepressants can be determined in b oth urine and serum. Analyte detectability is increased up to to-fold due t o trace enrichment during the extraction process the limits of detection (L ODs; UV 214 nm) are 30 - 300 ng mL(-1) in urine and 300 - 1000 ng mL(-1) in serum. The RSD values (n = 5) of the within-day and between-day precision are below 9% and 11%, respectively. Therefore, the present procedure can be used for drug monitoring.