A system of capillary electrophoresis with electrochemiluminescence detection (CE-ECL) together with UV spectroscopic and electrochemical methods were used to study the chemical oxidation of p-hydroxyphenylpyruvic acid (pHPP) by dissolved oxygen in aqueous solution. The pHPP was observed to be readily oxidized by dissolved oxygen in alkaline solution and yielded a compound that strongly enhanced the electrochemiluminescence of Ru(bpy)2 3+. This compound was separated and detected by a new CE-ECL system and revealed to be oxalate by being compared with an authentic sample of oxalate. The chemical oxidation mechanism of pHPP by dissolved oxygen was discussed in this paper.

Aesculetin is the product of the hydrolysis reaction of aesculin.Ahigh sensitivity and good repeatability method based on capillary electrophoresis with amperometric detection (CE-AD) was developed for simultaneous determination of aesculin and aesculetin in the hydrolysate of aesculin. Under the optimum condition: 10mmol/L KH2PO4–5 mmol/L Na2B4O7 (pH 6.0) buffer, separation at 18 kV and +900mV (versus Ag/AgCl) as the detection potential, the hydrolysis rate constants of aesculin hydrolysis at 25, 30, 35, 40 and 45℃ in 0.1 mol/L KOH were obtained as 1.45×10−2 min−1, 2.01×10−2 min−1, 2.93×10−2 min−1, 3.76×10−2 min−1 and 5.05×10−2 min−1, respectively. It was calculated that the activation energy for aesculin hydrolysis was 49.4 kJ/mol.

A capillary electrophoresis system coupled with wall-jet amperometric detection was used to determine five flavonoids (kaempferol, rutin, hyperoside, quercitrin, quercetin) in Herba Leonuri. Several important effect factors, such as the pH and concentration of running buffer, separation voltage, injection time, and detection potential, were investigated to acquire the optimum conditions. With 50 mmoL/L Na2B4O7-100 mmoL/L NaH2PO4 buffer (pH=7.50) as the running buffer, the five flavonoids were baseline separated within 15 min in a 60 cm length capillary at a separation voltage of 15 kV. The relationship between peak currents and analyte concentrations was linear over about 2 orders of magnitude, with detection limits (S/N=3) ranging from 0.03 to 0.08μg/mL for all analytes. The use of this method for the quantitation of the above flavonoids present in the real sample of Herba Leonuri was reported.

The main aim of this paper is to explore a new label for electrochemiluminescence(ECL) bioassays. Tetra-substituted sulphonated cobalt(II) (CoTSPc)acting as a mimetic peroxidase ofhorseradish peroxidase was first found to be able to catalyze the ECL reaction of luminol-H2O2 at a glass carbon electrode. CoTSPc also retained its ECL catalytic activity when it was conjugated to BSA. Moreover, the enhanced ECL intensity of the luminol–H2O2 system at pH 7.4 was proportional to the amount of target bovine serum albumin (BSA). The spectrum characteristics of CoTSPc–BSA conjugate was examined. The effects of the pH, reaction medium of the solution, the concentration of luminal, H2O2 and the electrochemical scanning mode were also investigated. Although refinements in the technique are still necessary before it can be used in practice, a new ECL probe for protein, CoTSPc, has been preliminarily developed.

A rapid, easy and reproducible capillary electrophoresis (CE) method for the simultaneous determination of allantoin, choline and arginine in Rhizoma Dioscoreae was developed first time. Under the optimum condition, the three analytes could be well separated within 5 min in a 70 cm (60 cm effective length) ×75μmi.d. capillary. The relative standard deviations for both migration time and peak height were less than 3.20%. The linear response range was 5.0-150, 0.9-100 and 1.0-200μg/ml for arginine, choline and allantoin, respectively. The detection limit of three components was 2.0, 0.4 and 0.5g/ml for arginine, choline and allantoin, respectively. Contents of arginine, choline and allantoin in the crude drug of Rhizoma Dioscoreae could be easily determined by the proposed method with satisfactory results.