Chemistry Investigatory Project

CHEM. RES. CHINESE UNIVERSITIES 2012, 28(3), 415418 Determination of Nicotine in baccy plant by capillary Electrophoresis with electrochemical Detection fair weather Jin-ying1, XU Xiao-yu1,2, YU Huan1 and YOU Tian-yan1* 1. State let out Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of attainments, Changchun 130022, P. R. China 2. Ministry of Public protective covering of Jilin Province, Changchun 130051, P. R.China Abstract A sensitive, unbiased and affordable method based on capillary vessel electrophoresis(CE) with electrochemical(EC) catching at a carbon fiber microdisk electrode(CFE) was developed for the determination of nicotine. do of undercover work capableness, submersion and pH honor of the inorganic phosphate cushion, and snap clip as fountainhead as withdrawal electromotive force drop were investigated. Under the optimized conditions a signal signal undercover work possible of 1. 20 V, 40 m gram jettyeculee/L phosphate weaken(pH 2. 0), a sample injection period of 10 s at 10 kV and a separation potential difference of 16 kV, the linear verify obtained was from 5. 0? 107 mol/L to 1. 0? 04 mol/L with a correlation coefficient of 0. 9989 and the sterilize of detection(LOD, S/N=3) obtained was 5. 0? 108 mol/L. The method was besides utilize to determine the nicotine in fundaments. Nicotine come up ranged from 0. 211 mg/g to 0. 583 mg/g in the tube-shaped structure tobacco of vii brands of hind end and the amount in whizz cigarette varied from 0. 136 mg/cigarette to 0. 428 mg/cigarette. Keywords Capillary electrophoresis electrochemical detection Nicotine Tobacco Article ID blow5-9040(2012)-03-415-04 1 Introduction Nicotine accounts for about 98%(mass fraction) of the enume site alkaloids and presents in a meanness of 0. %? 8% (mass fraction) in tobacco1,2. And nicotine addiction is related with eminent risk for many kinds of diseases such as Alzheimer s, Parkinsons and even suicide3,4. Thus its necessary to control nicotine amount in tobacco products. Determination of nicotine is very key in both the tobacco exertion and toxicology area5. A lot of analytical methods brace been completed for the analysis of nicotine and related alkaloids, such as radioimmuno check mark6, spectrophotometry5, near-infrared spectroscopy7, and recently f unhopeful injection(FI) with electrochemiluminescence(ECL) detection8.The almost frequently use analytical techniques for nicotine and its relation back compounds determination are gamy operation liquid chromatography(HPLC)9? 15 and gas chromatography (GC)16? 23 with mass spectrometry(MS). Besides, HPLC pair with UV-visible absorption(UV)24? 28 or GC with flame ionization detector(FID)1,29,30 and atomic emission detector(AED)31 fall in as well as been developed to determine nicotine and related alkaloids. Capillary electrophoresis(CE) is characterized by high separation efficiency, forget ful analysis condemnation and a keen amount of reagent consumed.Moreover, capillary column is ductile for use, easy to be treated with and cost effective. CE has been considered as an efficient preference for HPLC technique32. Up to now, various detectors have been combine with CE separation for nicotine analysis, such as CE-MS33,34, nonaqueous CE(NACE)-MS35, CE-UV36? 38, chipping mi- jail cellar electrokinetic chromatography(microchip MEKC)-UV39 and CE with three-fold light-emitting diode induced fluorescence (LEDIF) and ECL detection40. Electrochemical(EC) detection has stock more attention ascribable to the unreserved manipulation and good selectivity.Electrocatalytic oxidation properties of nicotine have been investigated at multi-walled carbon na nonube-alumina-coated silica nanocomposite limited glassy carbon electrode(MWCNTACS-GCE), MWCNT-GCE and pencil black lead electrode3,41,42. HPLC with EC detection has been use for nicotine assay in plasma and hair43,44. NACE -EC was also established for tobacco nicotine detection45. In this paper, a simple CE-EC analytical procedure at a carbon fiber microdisk electrode(CFE) was developed. The linear range was 5. 0? 107? 1. 0? 104 mol/L, with a correlation coefficient of 0. 989. The limit of detection(LOD, S/N=3) obtained was 5. 0? 108 mol/L. To evaluate the applicability of the proposed CE-EC method, sevener divers(prenominal) cigarette brands were tested. Nicotine amounts ranged from 0. 211 mg/g to 0. 583 mg/g in subway tobacco of seven brands of cigarette and the amount in one cigarette varied from 0. 136 mg/cigarette to 0. 428 mg/cigarette. 2 2. 1 Experimental Reagents All the reagents were of analytical year that were used as received without advance purification. Nicotine(purity 99. 7%) was obtained from Alfa Aesar(USA). Stock solution of 1. ? 103 mol/L nicotine was vigilant in doubly distilled water * correspond author. E-mail emailprotected jl. cn Received June 20, 2011 accepted November 24, 2011. support by the National Natural Science Foundation of China(No. 20875085). 416 CHEM. RES. CHINESE UNIVERSITIES Vol. 28 and stored at 4 C. Na2HPO4, NaH2PO4, H3PO4 and NaOH were used for phosphate original solutions(PBS) preparation. All the solutions were watchful and dilute with doubly distilled water unless differentwise indicated. PBS was prepared daily with doubly distilled water.All the solutions were filtered through a 0. 22 ? m membrane in the first place use. Different brands of cigarette were purchased from local market. high detection sensitiveness. As shown in Fig. 2, with the add of the apply detection potential, the up-to-date retort subjoind slowly amidst 0. 70 and 1. 00 V, and whence developmentd quickly betwixt 1. 00 and 1. 20 V. Higher detection potential than 1. 20 V led to a peak current decrease and scene noise increase. To achieve high detection sensitivity, 1. 20 V was selected as the optimal applied detection potential. 2. 2 Apparatu sEC audition was conducted with a Voltammetric Analyzer(CHI 800, USA). A conventional three-electrode system of rules was employed with a 33-? m CFE as working electrode, a Pt cable as counter electrode and an Ag/AgCl electrode as reference electrode. An uncoated fused-silica capillary with i. d. of 25 ? m and length of 45 cm(Ruifeng Chromatogram Equipment Co. , Ltd. , Hebei, China) was used for sampling and separation. Capillary was rinsed in 0. 1 mol/L NaOH overnight before use. Every day before essays, it was redden with doubly distilled water for about 10 min and balanced with running caramel brown for about 15 min.CE-EC was conducted on a self-assembly instrument including a Voltammetric Analyzer(CHI 800, USA) and a high potency supplier(MPI-A, Remax Electronic Co. , Ltd. , Xian, China). model injection was performed electrokinetically for 10 s at 10 kV. Fig. 2 HDV investigation of nicotine c(Nicotine)=1. 0? 105 mol/L sample injection 10 s at 10 kV separation electromo tive force 20 kV CE buffer 40 mmol/L PBS(pH 2. 0) cell buffer 0. 1 mol/L PBS(pH 8. 0). 3. 3 Optimization of CE-EC Conditions 3 3. 1 Results and Discussion cyclic Voltammetry(CV) CV was used to investigate the electrochemical behavior of nicotine.A spectacular current increased from 0. 70 V was observed for nicotine(Fig. 1, rick b) compared with that of background electrolyte(Fig. 1, curve a), indicating that nicotine had high electroactivity at CFE. The adsorption lieu of CFE for nicotine was also investigated under CV experiment, however, no adsorption phenomenon of nicotine was observed. Since the oxidation potential of nicotine was not high at CFE, CE bring together with EC at CFE is practical for nicotine determination. roughly other important agentive roles including buffer concentration and buffer pH as well as separation potentiality were investigated.Running buffer pH value make up ones minds the charge-mass ratio of the analyte and then influences the electrophoresi s behavior of the analyte. We investigated the effect of pH values on the detection between pH 2. 0 and pH 10. 0 as shown in Fig. 3. Fig. 3 encumbrance of pH of CE buffer on detection of nicotine pH a. 2 b. 4 c. 6 d. 8 e. 10. Separation potency 14 kV other conditions were the identical as those in Fig. 2. Fig. 1 Cyclic voltammetry curve of nicotine a. Background electrolyte, 0. 1 mol/L PBS(pH 8. 0) b. 1. 0? 103 mol/L nicotine scan rate 0. 05 V/s. 3. Hydrodynamic Voltammogram(HDV) Investigation Since applied detection potentials influence the detection sensitivity, and then we investigated the HDV of nicotine to achieve At pH 2. 0, nicotine was amply protonated and electroosmotic flow(EOF) was well restrained. EC reply was the highest at pH 2. 0, and then decreased with the increase of pH value. With the increase of pH value, the migration age decreased correspondingly. Strong acidic CE buffer pH is more safe to sensitive and selective determination of nicotine. In considerat ion of the detection sensitivity, pH 2. was selected as the proper CE buffer pH value. Separation potential is an important factor that influences the detection sensitivity and the migration time. When the separation voltage was changed from 10 kV to 20 kV, the migration time decreased from 14 min to 7 min correspondingly. No. 3 SUN Jin-ying et al. 417 As for EC repartee, when the separation voltage increased from 10 kV to 18 kV, the EC intensity of nicotine increased quickly, after(prenominal) that it decreased quickly from 18 kV to 20 kV(shown in Fig. 4). Detection sensitivity at 16 kV was high than that at 18 kV.In consideration of the detection sensitivity, 16 kV was selected as the optimum separation voltage. supermarket. tubing tobacco of 0. 1 g was weighed and placed in a polyethylene tube, in which 10 mL of solvent was added for nicotine declension. Then, 10 L of the blood solution was transferred into a new polyethylene tube and diluted 100 generation by doubly dis tilled water and the diluted decline solution was used for analysis. 4. 2 Investigation of origin Solvents Fig. 4 nitty-gritty of separation voltage on detection of nicotine Applied detection potential 1. 20 V other conditions are as those in Fig. . 3. 4 Linear feed and LOD To obtain high extraction efficiency, solvents including water, methanol, put out and ethyl acetate rayon were investigated. Current solution of nicotine extracted with different solvents is shown in Fig. 5. Current response of nicotine was the highest when water was used as solvent. methanol was also efficient for the extraction of nicotine from pipe tobacco. However, when methanol was used as solvent, migration time prolonged and the baseline shifted. When chloroform was used for extraction, current response was about 36% of that when water was used for extraction.Only very low response was found when ethyl acetate was used as solvent. piss was selected as nicotine extraction solvent for the highest nic otine current response obtained. Under the selected conditions an applied detection potential of 1. 20 V sample injection for 10 s at 10 kV a separation voltage of 16 kV 40 mmol/L PBS(pH 2. 0) as running buffer and 0. 1 mol/L PBS(pH 8. 0) as detection buffer, EC response of nicotine was linear with concentration from 5. 0? 107 mol/L to 1. 0? 104 mol/L(81? 16200 g/L)(y = 0. 2566+0. 4884x, R2= 0. 9978) and LOD(S/N=3) of nicotine was fixed to be 5. 0? 108 mol/L(8. g/L). The proposed CE-EC method was compared with HPLC-MS9,10, HPLC-UV24,28, CE-UV38,39, CE-MS34, CE-LEDIF-ECL40, microchip CE-UV39, NACE-MS35 and NACE-EC45 methods(Table 1). From Table 1 we can receive that linear range and LOD of CE-EC are just about comparable with those of HPLC-MS9 and UV24 or NACE-EC45 methods and CE-EC is almost 2000 times more sensitive than microchip CE method. Table 1 Method HPLC-MS HPLC-MS FI-ECL HPLC-UV HPLC-UV CE-MS NACE-MS CE-UV Micorchip CE-UV CE-LEDIF-ECL NACE-EC CE-EC Fig. 5 extraction sol vent comparison a. Water b. methanol c. chloroform d. ethyl acetate.Separation voltage 16 kV injection 10 s at 10 kV applied detection potential 1. 20 V cell buffer 0. 1 mol/L PBS(pH 8. 0) CE buffer 40 mmol/L PBS(pH 2. 0). 4. 3 Extraction Time Investigation Comparison of CE-EC with other methods for nicotine determination Linear range/(? gL1) 10? 10000 1? 100 0? 16000 25? euchre 250? 100000 500? 100000 1724? 17240 100? 10000 81? 16200 LOD/(? gL1) 10 1 0. 19 8 100 0. 55 20 16000 259. 2 13 8. 1 Ref. 9 8 22 24 28 34 35 38 39 40 45 Our method The influence of extraction time on nicotine detection was investigated between 2 and 7 h.When extraction time was increased from 2 h to 4 h, the nicotine response kept increasing. plainly when extraction time continued to increase, the current response decreased, which may be due to the nicotine decomposition under room conditions. We chose 4 h as proper extraction time based on the experiment result. 4. 4 Tobacco Analysis 4 4. 1 Cigarette A nalysis Extraction Procedure Seven brands of cigarettes were purchased from local Pipe tobacco of 0. 1 g of from each one seven brands of cigarettes was weighed respectively and 10 mL of doubly distilled water was used for nicotine extraction.Nicotine amounts ranged from 0. 211 mg/g to 0. 583 mg/g in the pipe tobacco of each of seven brands of cigarettes. Nicotine amount in one cigarette varied from 0. 136 mg/cigarette to 0. 428 mg/cigarette(as listed in Table 2). The results obtained are somewhat less than the amounts reported in the literature46. With the increase of nicotine concentration, the recovery decreased. For 5. 0? 106, 5. 0? 105 and 5. 0? 104 mol/L of nicotine, the recoveries were 80%, 75% and 418 CHEM. RES. 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