Determination of Nicotine in Tobacco by Capillary Electrophoresis with Electrochemical Detection SUN Jin-ying1, XU Xiao-yu1,2, YU Huan1 and YOU Tian-yan1*
1. State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China; 2. Ministry of Public Security of Jilin Province, Changchun 130051, P. R. China Abstract 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 detection 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 mmol/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 cigarette varied from 0.136 mg/cigarette to 0.428 mg/cigarette. Keywords Capillary electrophoresis; Electrochemical detection; Nicotine; Tobacco Article ID 1005-9040(2012)-03-415-04
Nicotine accounts for about 98%(mass fraction) of the total alkaloids and presents in a concentration of 0.5%―8% (mass fraction) in tobacco[1,2]. And nicotine addiction is related with higher risk for many kinds of diseases such as Alzheimer’s, Parkinson’s and even suicide[3,4]. Thus it’s necessary to control nicotine amount in tobacco products. Determination of nicotine is very important in both the tobacco industry and toxicology area. A lot of analytical methods have been established for the analysis of nicotine and related alkaloids, such as radioimmunoassay, spectrophotometry, near-infrared spectroscopy, and recently flow injection(FI) with electrochemiluminescence(ECL) detection. The most frequently used analytical techniques for nicotine and its relative compounds determination are high performance liquid chromatography(HPLC)[9―15] and gas chromatography (GC)[16―23] with mass spectrometry(MS). Besides, HPLC coupled with UV-visible absorption(UV)[24―28] or GC with flame ionization detector(FID)[1,29,30] and atomic emission detector(AED) have also been developed to determine nicotine and related alkaloids. Capillary electrophoresis(CE) is characterized by high separation efficiency, short analysis time and a small amount of reagent consumed. Moreover, capillary column is flexible for use, easy to be treated with and cost effective. CE has been considered as an efficient alternative for HPLC technique. Up to now, various detectors have been combined with CE separation for nicotine analysis, such as CE-MS[33,34], nonaqueous CE(NACE)-MS, CE-UV[36―38], microchip mi-
cellar electrokinetic chromatography(microchip MEKC)-UV and CE with dual light-emitting diode induced fluorescence (LEDIF) and ECL detection. Electrochemical(EC) detection has received more attention due to the simple manipulation and good selectivity. Electrocatalytic oxidation properties of nicotine have been investigated at multi-walled carbon nanotube-alumina-coated silica nanocomposite modified glassy carbon electrode(MWCNTACS-GCE), MWCNT-GCE and pencil graphite electrode[3,41,42]. HPLC with EC detection has been used for nicotine assay in plasma and hair[43,44]. NACE-EC was also established for tobacco nicotine detection. In this paper, a simple CE-EC analytical procedure at a carbon fiber microdisk electrode(CFE) was developed. The linear range was 5.0×10–7―1.0×10–4 mol/L,...