Rapid analysis of traditional Chinese medicine Pinellia ternata by microchip electrophoresis with electrochemical detection.

Traditional Chinese herbal medicine has long enjoyed the reputation of the world's most advanced system of natural medicine. Pinellia ternata is one of the most commonly used herbs in the traditional Chinese medical science. In this study, five representative ingredients of Pinellia ternata guanosine, methionine, glycine, 3,4-dihydroxybenzaldehyde, and homogentisic acid, were assayed using simple derivatization procedures. Under optimized experimental condition, five analytes in Pinellia ternata were rapidly separated and detected using microchip electrophoresis, affording the benefits of speed, minimal sample requirements, and sensitive on-the-chip electrochemical detection, in 5 min with linearity over a concentration of 20-500 µM (R2  = 0.994) with nearly complete recovery (95.6-98.5%).

Microchip capillary electrophoresis with amperometric detection for several carbohydrates.

Microchip capillary electrophoresis (muCE) with amperometric detection at Cu electrode benefited fast separation and direct detection of carbohydrates. The working electrode of 50-mum Cu wire attached nearly against the channel outlet-4mum, where it benefited collecting detection current and suppressing overwhelming noise. The use of alkaline medium was essential to separating and detecting carbohydrates, which dissociated into the sensitive alcolate anions. The 10-cm serpentine chip, though lengthening the migration time, it provided better efficiency. Sucrose, cellobiose, glucose, and fructose migrated from the outlet in 400s +2000V. The linear calibration plots ranging from 10 to 1000muM with regression coefficients better than 0.996 were obtained. The injection-to-injection reproducibility of 1.24% (n=7) for glucose in peak current and 0.6% for migration times were excellent. The detection limit was low, down to 2.3muM for glucose (S/N=3) or 27.6attomole in mass detection.

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

An integrated multiple-enzymatic assay was performed on a (microchip capillary electrophoresis) muCE-EC chip capable of precise intake of sample or reagents in nanoliters. Incorporating multiple-enzyme assay into the muCE 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 1muM 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 10mum embedded Pt electrode, deposited at the end of the 30mum 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 0.71muM for ascorbic acid to 10muM for glucose. The calibration curve was linear from 10 to 800muM (R(2)>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.