A fully automated method is presented for the determination of acidic drugs
in urine and serum using on-line dialysis-solid-phase extraction (SPE)-cap
illary electrophoresis (CE) with UV detection. With non-steroidal anti-infl
ammatory drugs (NSAIDs) as test compounds, detection limits in the biologic
al samples were 0.05-1.0 mu g ml(-1). Calibration plots were linear over tw
o orders of magnitude and the within-day and between-day repeatability were
better than 10%. The CE capillary and SPE column were used for over 500 an
alyses; the dialysis membrane was replaced after 250 analyses. A general pr
otocol for dialysis-SPE-CE which can be used for amphoteric and acidic drug
s was devised. The present results show that this protocol has general vali
dity and can be recommended for future work on other classes of drugs.