DUAL-ELECTRODE AMPEROMETRIC DETECTION FOR THE DETERMINATION OF SR4233AND ITS METABOLITES WITH MICROBORE LIQUID-CHROMATOGRAPHY

3-Amino-1,2,4-benzotriazine-2,4-di-N-oxide (SR4233) is a promising new antineoplastic agent based on reductive activation. SR4233 and its ma jor metabolites (SR4317 and SR4330) are all easily reduced at a carbon electrode. Reductive amperometric detection can therefore provide hig h selectivity and low detection limits with chromatographic analysis a nd is an ideal approach to detection of SR4233 in microdialysis sample s. However, in order to use amperometric detection in the reductive mo de, sample deoxygenation is necessary. This is typically done by purgi ng the sample with either argon or nitrogen prior to injection. This a pproach is not feasible for microdialysis samples because only 5-10 mu l is usually available. In this report, a microbore liquid chromatogr aphic method with dual-electrode amperometric detection is described f or the determination of SR4233 and its metabolites without predeoxygen ation. A dual-electrode amperometric detector was used in the series c onfiguration with an upstream potential of -450 mV to reduce SR3233 an d its metabolites to a common product and a downstream potential of +4 00 mV to oxidize this product. Oxygen is only electroactive at the ups tream electrode because of its irreversible behavior. This method is c ompatible with the small sample volumes provided by microdialysis samp ling. Linear calibration graphs were obtained up to 55 mu M for SR4233 , and 140 mu M for both SR4317 and SR4330. The detection limits were 7 0 nM for SR4233, and 50 nM for SR4317 and SR4330. The average intra-da y variation over 5 days was 1.8% (SR4233), 1.4% (SR4330), and 1.8% (SR 4317), whereas the inter-day variation over 5 days was 14.1% (SR4233), 8.6% (SR4317), and 2.6% (SR4330).