Capillary electrophoretic determination of S-carboxymethyl-L-cysteine and its major metabolites in human urine: feasibility investigation using on-column detection of non-derivatized solutes in capillaries with minimal electroosmosis

The capillary electrophoretic analysis of S-carboxymethyl-L-cysteine and some of its metabolites in human urine is reported using (i) on-column detection of underivatized solutes, (ii) minimal sample pretreatment and (iii) capillary columns with minimized electroosmosis. Experimental results obtained with two apparatus, the HPE-100 (Bio-Rad), featuring coated fused silica capillaries of 25 microns i.d., and with the Tachophor 2127 (LKB), having Teflon capillaries of 500 microns i.d. are discussed. Drug concentrations down to 0.2 mg/mL on capillary isotachophoresis and 0.03 mg/mL on capillary zone electrophoresis can be monitored with these instruments.