Determination of Nicotine in Tobacco by Capillary Electrophoresis with Electrochemical Detection

A sensitive, simple and low-cost method based on capillary electrophoresis（CE） with electrochemical（EC） detection at a carbon fiber microdisk electrode（CFE） was developed for the determination of nicotine. Effects of de- tection potential, concentration and pH value of the phosphate buffer, and injection time as well as separation voltage were investigated. Under the optimized conditions： a detection potential of 1.20 V, 40 rnmol/L phosphate buffer（pH 2.0）, a sample injection time of 10 s at 10 kV and a separation voltage of 16 kV, the linear range obtained was from 5.0×10^-7 mol/L to 1.0×10^-4 mol/L with a correlation coefficient of 0.9989 and the limit of detection（LOD, S/N=3） obtained was 5.0×10^-8 mol/L. The method was also used to determine the nicotine in cigarettes. Nicotine amount ranged from 0.211 mg/g to 0.583 mg/g in the pipe tobacco of seven brands of cigarette and the amount in one ciga- rette varied from 0.136 mg/cigarette to 0.428 mg/cigarette.

Facile Synthesis of Gold Nanoparticle-loaded Carbon Nanofiber Composites and Their Electrocatalytic Activity Towards Dopamine, Ascorbic Acid and Uric Acid

A facile approach for the synthesis of gold nanoparticle-loaded carbon nanofiber（Au/CNF） composites was developed. When applied to electrochemistry, these composites showed attractive performances such as high conductivity and facile electron transfer kinetics. Under physiological conditions, the Au/CNF composite modified electrode exhibits highly electrocatalytic activity for the oxidation of dopamine, ascorbic acid and uric acid. Owing to the good selectivity for the simultaneous detection of these three species, the novel composites are promising for the development of effective electrochemical biosensors.

Determination of Amino Acids by Ru(bpy)_3^(2+) Cathodic Electrochemiluminescence with High Sensitivity

The unique cathodic electrochemiluminescence（ECL） emission of Ru（bpy）3^2＋（bpy=2,2′-bipyridine） was observed via Nation film at Au electrode[Au/Nafion/Ru（bpy）3^2＋] at about 0.20 V（vs. Ag/AgCl） and applied to the determination of several amino acids without prior derivatization with high sensitivity. The cathodic electrochemiluminescence（ECL） exhibits the detection limits and linear ranges of several amino acids comparable to or better than those of capillary electrophoresis with conventional ECL detection method（at 1.10-1.20 V vs. Ag/AgCl） based on precolumn derivatization. The results suggest that the cathodic ECL is promising for the detection of amino acids in bioanalysis.

Enantiomeric Separation of Antidepressant Trimipramine by Capillary Electrophoresis Combined with Electrochemiluminescence Detection in Aqueous-organic Media

The antidepressant trimipramine（Tri） enantiomers were successfully separated by capillary electrophoresis（CE） coupled with electrochemiluminescence（ECL） detection in aqueous-organic media. A dual cyclodextrin（CD） system combining β-CD and hydroxypropyl-β-cyclodextrin（HP-β-CD） was used as chiral selector. Acetonitrile（ACN） was added to the running buffer to improve the separation efficiency, detection sensitivity and repeatability. The method was also successfully applied to the chiral separation of Tri in spiked human urine sample.

Quality Analysis of Herbal Medicine Products Prepared from Herba Sarcandrae by Capillary Electrophoresis with Electrochemical Detection

A capillary electrophoresis with electrochemical detection（CE-ED） method was developed for the quality analysis of herbal medicine products prepared from the same herb of Herba Sarcandrae： Fufang Caoshanhu tablets, Qingrexiaoyanning capsules, and Xuekang oral liquids. Under the optimal analysis conditions, the low detection limit[l.0×10^-7 mol/L（S/N=3）] and the wide linear range（1.0×10^-7-1.0×10^-4 mol/L） were obtained for quality standard compound of isofraxidin. The precisions of the peak current and the migration time（as RSDs） for the real sample analysis were 2.0%-2.6%, and 1.2%-1.8% for isofraxidin, respectively. The contents of isofraxidin detected were 15.77 μg/tablet, 0.48 mg/capsule, 1.2 mg/ampoule（Jiangxi）, and 0.44 mg/ampoule（Dalian） for Fufang Caoshanhu tablets, Qingrexiaoyanning capsules, and Xuekang oral liquids from different manufacturers, respectively. Quality estimate was conducted by comparing the contents of isofraxidin in the herbal medicine products with the demanded values of Chinese pharmacopeia. In addition, based on their own unique CE-ED profiles（namely, CE-ED electropherograms） the Xuekang oral liquids from the different manufacturers could be easily identified.