Microchip capillary electrophoresis with electrochemical detector for precolumn enzymatic analysis of glucose, creatinine, uric acid and ascorbic acid in urine and serum

Abstract

An integrated multiple-enzymatic assay was performed on a (microchip capillary electrophoresis) μCE–EC chip capable of precise intake of sample or reagents in nanoliters. Incorporating multiple-enzyme assay into the μCE chip is relatively new—rendering simultaneous analysis of creatinine and uric acid a snap.Added to the list of merits in this study are the enhanced sensitivity down to 1μM and a broader spectrum of analytes—inclusive of glucose for the long-time sufferers of diabetes. The performance was orchestrated to attain the claimed level: employing the end-channel electrode mode to tame the noises and the precolumn enzymatic reaction to stabilize the baseline. The 10μm embedded Pt electrode, deposited at the end of the 30μm wide separation channel, benefited chip fabrication besides noise reduction. The optimized conditions were 20mM phosphate buffer (pH 7.5), +1.5kV separation voltage and +1.0 V detection potential (versus Ag/AgCl). The migration time was repeatable within the deviation of 0.5% R.S.D. (n=7), but the peak currents ranged from 1.5 to 2.2% R.S.D. The detection limits (S/N=3) ranged from 0.71μM for ascorbic acid to 10μM for glucose. The calibration curve was linear from 10 to 800μM (R2>0.995). Glucose, creatinine, uric acid and ascorbic acid as model analytes, in pure form or in serum and urine samples, were tested to verify its feasibility.