毛细管区带电泳法分析绿茶中的痕量成份

采用毛细管电泳/安培检测法(CE/AD)同时分离测定了绿茶中的芦丁、没食子酸、槲皮素、绿原酸等生物活性成分的含量, 考察了运行缓冲液酸度、浓度、分离电压、氧化电位和进样时间等实验参数对分离、检测的影响。在最优化条件下, 以300 μm碳圆盘电极为检测电极, 检测电位为+ 950 mV (vs. SCE) , 60 mmol/L硼酸盐运行缓冲液(pH 8.7)中, 上述各组分在20 min内可实现基线分离。各组分浓度与峰电流在3个数量级范围内呈良好线性, 检出限(S/N=3)在1.0×10^-7到1.0×10^-4g^.mL^-1范围,四种标样7次平行进样的相对标准偏差(RSD)小于3.0 %。该方法已成功地应用于绿茶中生物活性成分的测定, 结果令人满意。     

Determination of Active Ingredients of Origanum Vulgare L. and Its Medicinal Preparations by Capillary Electrophoresis with Electrochemical Detection

Abstract

A method based on capillary electrophoresis with electrochemical detection (CE‐ED) has been developed for the first time for the separation and determination of isovanillic acid, vanillic acid, quercetin, rosmarinic acid, caffeic acid, and protocatechuic acid in Origanum vulgare L. and its medicinal preparations. The effects of working electrode potential, pH level, concentration of running buffer, separation voltage, and injection time on CE‐ED were investigated. Under the optimum conditions, the analytes could be separated in a 50 mmol L^?1 borate buffer (pH 8.7) within 21 min. A 300‐µm diameter carbon disk electrode has a good response at +0.95 V (vs. SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N=3) ranging from 4×10^?8 g mL^?1 to 2×10^?7 g mL^?1 for the analytes. The method has been successfully applied to the analysis of real sample, with satisfactory results.     

Determination of Taurine in Lycium Barbarum L. and Other Foods by Capillary Electrophoresis with Electrochemical Detection

A method based on capillary electrophoresis (CE) with electrochemical detection (ED) was developed for the determination of taurine in Lycium Barbarum L., LIPOVIYAN beverage and milk powder. The effects of some important factors such as the acidity of the running buffer, separation voltage, injection time, and applied potential to working electrode were investigated. Operated in a wall‐jet configuration, a 300 μm diameter carbon‐disk electrode was used as the working electrode, which exhibits good responses at +1.05 V (vs. SCE) for taurine. Excellent linearity was obtained in the concentration range from 5.0×10^?4 mol/L to 5.0×10^?6 mol/L. The detection limit (S/N=3) was 1.0×10^?7 mol/L. This proposed method has been successfully applied to analyze the actual samples with satisfactory assay results.     

毛细管电泳-电化学检测法测定中药杠版归中的活性成分

采用毛细管电泳-电化学检测法（CE-ED）同时分离测定了中药杠板归中的阿魏酸、香草酸、槲皮素、咖啡酸、原儿茶酸等主要生物活性成分的含量。考察了工作电极电位、运行缓冲液的pH值和浓度、分离电压和进样时间等实验参数对实验结果的影响。在优化的实验条件下,以直径300 μm的碳圆盘电极为工作电极,检测电位为＋0.95V(vs. SCE),在10mmol/L磷酸盐（pH 9.2）的运行缓冲溶液中,五个分析物能够在17min内实现很好的基线分离,被测物浓度与峰电流在3个数量级呈良好的线性,检测限（S/N＝3）范围从7.1×10-8 到 9.3×10-8g mL-1。该方法已应用于实际样品的分析,样品处理简单,获得了令人满意的结果。     

Determination of Active Ingredients of Hawthorn by Capillary Electrophoresis with Electrochemical Detection

A method based on capillary electrophoresis with electrochemical detection has been developed for the separa-tion and determination of epicatechin,kaempferol,chlorogenic acid,4-hydroxybenzoic acid,quercetin and proto-catechuic acid in hawthorn for the first time.The effects of working electrode potential,pH and concentration ofrunning buffer,separation voltage and injection time on CE-ED were investigated.Under the optimum conditions,the analytes could be separated in a 60 mmol·L~(-1) borate buffer(pH 8.7)within 21 min.A 300 μm diameter carbondisk electrode has a good response at 0.95 V(vs.SCE)for all analytes.The response was linear over three ordersof magnitude with detection limits(S/N=3)ranging from 3×10~(-8) to 2×10~(-7) g·mL~(-1) for the analytes.The methodhas been successfully applied to the analysis of real sample,with satisfactory results.     

Electrochemical Detection of Methimazole by Capillary Electrophoresis at a Carbon Fiber Microdisk Electrode

We developed a sensitive, simple and low cost method to determine methimazole based on capillary electrophoresis with electrochemical detection (CE‐EC) at a carbon fiber microdisk electrode (CFE). We investigated the effects of detection potential, the concentration and pH value of the phosphate buffer, and injection time as well as separation voltage on the detection of methimazole. Under the optimized conditions: the detection potential at 1.30 V, 10 mmol/L phosphate buffer (pH 7.0), injection time 30 s at a height of 20 centimeter and separation voltage at 15 kV, the linear range was obtained from 1.0×10^?7 to 2.0×10^?4 mol/L, covering 3 orders of magnitude with a correlation coefficient of 0.9995. The LOD (S/N=3) obtained was 5.0×10^?8 mol/L. The RSD of migration time and peak current for 2.0×10^?4 mol/L methimazole was 1.04% and 1.54% (n=10), respectively. The method was also used to analyze methimazole tablets and human urine sample.     

The Electrocatalytic Oxidation of Thymine at α‐Cyclodextrin Incorporated Carbon Nanotube‐Coated Electrode

Electrocatalytic oxidation of thymine at α‐cyclodextrin (α‐CD) incorporated carbon nanotube‐coated electrode (CNT/CE) was thoroughly studied in alkaline media. CNT showed an electrocatalytic effect on the oxidation of thymine, formation of a supramolecular inclusion complex between α‐CD and thymine at CNT/CE further enhanced the sensitivity to thymine. The electrocatalytic behavior was further developed as a sensitive detection scheme for thymine by differential pulse voltammetry. A linear calibration over the concentration range from 2.5×10^?5 to 1.8×10^?3 mol/L in pH 10.8 NaHCO₃‐Na₂CO₃ buffer solution was obtained with a detection limit of 5×10^?6 mol/L.     

Boron‐chelating fluorescent probe (BOPB) in the red region combined with CE‐LIF for the detection of NO in mice liver

Precise measurement of nitric oxide (NO) is of great importance to understand the function of NO in liver and the mechanism of liver injury. 8‐(3’,4’‐Diamino phenyl)‐3,5‐(2‐hydroxyphenyl)‐dimethylene pyrrole (BOPB), a fluorescent probe in the red region (>600 nm) newly developed in our group, has good photostability and excitation/emission wavelength of 622/643 nm matching well with commercial 635 nm semiconductor laser of CE‐LIF detection. Therefore, BOPB was used in CE‐LIF for the determination of NO in mice liver. Both derivatization and separation conditions were optimized. Derivatization reaction of BOPB and NO was carried out in pH 7.4 PBS buffer at 35°C for 12 min and the separation of NO derivative of BOPB (BOPB‐T) was achieved within 7.0 min in pH 9.0 running buffer containing 15 mM H₃BO₃–NaOH and 15 mM SDS. Good linearity was found in the range of 1.0 × 10^?9–5.0 × 10^?7 M with the LOD of 0.02 nM. The proposed method was applied to the analysis of NO in real samples, and NO concentration was obviously increased in acute liver injury of mice. Compared to existing derivatization‐based CE‐LIF methods for NO, this method has lower LOD and less background interference owing to detection wavelength of BOPB in the red region.     

CE-electrochemiluminescence with ionic liquid for the facile separation and determination of diester-diterpenoid aconitum alkaloids in traditional Chinese herbal medicine

A CE‐electrochemiluminescence(CE‐ECL) detection system, CE/tris(2,2′‐bipyridyl) ruthenium(II)ECL with ionic liquid, was established for the determination of diester‐diterpenoid aconitum alkaloids (aconitine (AC), mesaconitine (MA) and hypaconitine (HA)) in traditional Chinese herbal medicine. Running buffer containing 25 mM borax‐20 mM 1‐ethyl‐3‐methylimidazolium tetrafluoroborate at pH 9.15 was used, which resulted in significant changes in separation and obvious enhancement in ECL intensity for AC, MA and HA with similar structures. End‐column detection was achieved in 50 mM phosphate buffer with 5 mM (pH 9.15) at applied detection voltage of 1.20 V when the distance between the Pt working electrode and outlet of capillary (50 cm×25 μm id) was set at 150 μm. One single quantitative analysis of three alkaloids was achieved at a separation voltage of 15 kV within 10 min. Moreover, two extraction processes (ethanol extraction and ethyl ether extraction after basification) were investigated. The result showed that ethanol extraction process has higher extraction efficiency than ethyl ether extraction process. Under the optimized conditions, the detection limits of AC, MA and HA were 5.62×10^?8, 2.78×10^?8 and 3.50×10^?9 mol/L (S/N=3), respectively. The method was successfully applied to determine the amounts of AC, MA and HA in the aconitum herbal samples.     

Study on the Effect of Moderate Exercise on Lactic Acid Content in Breast Milk by Indirect CE with Amperometric Detection

An indirect high-performance capillary electrophoresis with amperometric detection (CE-AD) method has been developed for determination of lactic acid (LA) in body fluids of lactating postpartum women. Several important factors such as the running buffer additive and concentration, the working electrode potential, the pH value and concentration of the running buffer, the separation voltage and injection time were investigated. Under the optimum conditions, LA could be well separated with co-existing interferences including uric acid (UA) in real samples in a 90-cm-length capillary at separation voltage of 12 kV in 4.0 × 10^?6 g mL^?1 3,4-dihydroxybenzylamine (DHBA)/40 mmol L^?1 H₃BO₃?CNa₂B₄O₇ buffer (pH 7.8). The linearity between peak current and concentration of LA was over three orders of magnitude with detection limit of 5.00 × 10^?7 g mL^?1 (S/N = 3). This proposed method has been successfully used to study the effects of moderate exercise on LA content in breast milk and urine samples of lactating postpartum women, and assay results showed that LA content in breast milk can return to normal level through 60 min rest without decreasing acceptance by breast-feeding infants, although the LA level did increase by 4?C6 times in both breast milk and urine samples at 10 min after moderate exercise.     

Simultaneous Determination of Phenolic Additives in Cosmetics by Micellar Electrokinetic Capillary Chromatography with Electrochemical Detection

A micellar electrokinetic capillary chromatography method with electrochemical detection (MECC‐ED) has been developed for the simultaneous determination of eight phenolic additives, including propyl gallate (PG), tert‐butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in cosmetic products. Method development involved optimization of the working electrode, the pH value of running buffer, the concentration of sodium dodecyl sulfate (SDS), the separation voltage, and the sample injection time. Under the optimum conditions, all analytes can be well separated within 26 min at the separation voltage of 18 kV in a 9 mmol·L^?1 sodium dodecyl sulfate (SDS) ?60 mmol·L^?1 borate running buffer (pH 8.0). A 300 μm diameter carbon disk electrode generated good response at +0.90 V (vs. SCE) for all analytes. Linearity of the present method was over three orders of magnitude of analyte concentration with detection limits (S/N=3) ranging from 1.1×10^?7 to 1.2×10^?6 g·mL^?1 for all analytes. This proposed method has been successfully applied to the simultaneous determination of the above additives in commercial cosmetics, and the assay results were satisfactory.     

Use of capillary electrophoresis with chemiluminescence detection for sensitive determination of homocysteine

A sensitive capillary electrophoresis (CE) method with chemiluminescence (CL) detection was developed for the determination of homocysteine (HCys) in human plasma. In this work, N‐(4‐aminobutyl)‐N‐ethylisoluminol was used as tagging reagent to label the analyte for achieving high assay sensitivity. N‐(4‐Aminobutyl)‐N‐ethylisoluminol‐tagged HCys after CE separation reacted with hydrogen peroxide in the presence of horseradish peroxidase, producing CL emission. Experimental conditions for labeling analyte, CE separation, and CL detection were studied. The CL intensity was proportional to the concentration of HCys in the range of 2.5×10^?8 to 5.0×10^?6 M. Detection limit (S/N=3) was 7.6×10^?9 M. Human plasma samples from healthy donors were analyzed by the presented method. HCys levels were found to be in the range of 9.50–15.3 μM.     

Capillary Electrophoresis Coupled with Electrochemiluminescence for the Facile Separation and Determination of Salbutamol and Clenbuterol in Urine

A capillary electrophoresis coupled with tris(2,2′‐bipyridyl) ruthenium(II) (Ru(bpy)₃²⁺) electrochemiluminescence detection system was developed to determine salbutamol and clenbuterol in urine. Some factors that affected the performances of separation and detection were investigated. Under the optimized conditions, one single quantitative analysis of salbutamol and clenbuterol was achieved at a separation voltage of 15 kV within 9 min, and the LODs (S/N=3) and LOQs (S/N=10) of salbutamol and clenbuterol were 8.43×10^?8 mol/L, 2.61×10^?7 mol/L and 2.73×10^?7 mol/L, 8.21×10^?7 mol/L, respectively. The recovery obtained from the analysis of spiked urine samples was between 88.6 % and 104.7 % with RSDs lower than 6.70 %. The method was successfully applied to determine salbutamol and clenbuterol in urine samples.     

Capillary electrophoresis coupled with electrochemiluminescence detection for the separation and determination of thyreostatic drugs in animal feed

A rapid, simple, and practical method for the determination of four of the most used thyreostatic drugs (methimazole, 2‐thiouracil, 6‐methyl‐2‐thiouracil, and 6‐propyl‐2‐thiouracil) using CE coupled to electrochemiluminescence detection has been established, based on the electrochemiluminescence enhancement of tris(2,2‐bipyridyl)ruthenium(II) with these analytes. Parameters that affect separation and detection were optimized. Under the optimum experimental conditions, the four analytes could be well separated within 11 min at the separation voltage of 16 kV in a running solution containing 20 mM phosphate buffer (pH 9.0) and 1.0 × 10^?4 M Ru(bpy)₃²⁺, with a solution of 20 mM phosphate buffer (pH 12.0) containing 1.0 × 10^?4 M Ru(bpy)₃²⁺ in the electrochemiluminescence detection cell. The detection limits for methimazole, 6‐methyl‐2‐thiouracil, 6‐propyl‐2‐thiouracil, and 2‐thiouracil were 0.1, 0.05, 0.05, and 0.01 μM, respectively. The proposed method was applied to analyze these drugs in spiked animal feed samples. The recoveries were 88.2～99.0 and 86.4～98.7% for the intraday and interday analyses, respectively. The RSDs were 2.7～4.8 and 1.8～5.0% for the intraday and interday analyses, respectively. The results demonstrate that the proposed method has promising applications in the detection of thyreostatic drugs in animal feeds.     

Electrocatalytic Oxidation and Voltammetric Determination of L‐Cysteic Acid at the Surface of p‐Bromanil Modified Carbon Paste Electrode

The electrochemical properties of L ‐cysteic acid studied at the surface of p‐bromanil (tetrabromo‐p‐benzoquinone) modified carbon paste electrode (BMCPE) in aqueous media by cyclic voltammetry (CV) and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of L ‐cysteic acid at the surface of BMCPE occurs at a half‐wave potential of p‐bromanil redox system (e.g., 100 mV vs. Ag|AgCl|KCl_sat), whereas, L ‐cysteic acid was electroinactive in the testing potential ranges at the surface of bare carbon paste electrode. The apparent diffusion coefficient of spiked p‐bromanil in paraffin oil was also determined by using the Cottrell equation. The electrocatalytic oxidation peak current of L ‐cysteic acid exhibits a linear dependency to its concentration in the ranges of 8.00×10^?6 M–6.00×10^?3 M and 5.2×10^?7 M–1.0×10^?5 M using CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (2σ) were determined as 5.00×10^?6 M and 4.00×10^?7 M by CV and DPV methods. This method was used as a new, selective, rapid, simple, precise and suitable voltammetric method for determination of L ‐cysteic acid in serum of patient's blood with migraine disease.     

Capillary Electrophoresis of the Active Ingredients of Dioscorea bulbifera L. and its Medicinal Preparations

A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of epicatechin, isovanillic acid, vanillic acid and myricetin in Dioscorea bulbifera L. and its medicinal preparations. The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time were investigated. Under optimum conditions, the analytes could be separated in a 40 mmol L^?1 borate buffer (pH 8.7) within 15 min. A 300 μm diameter carbon disk electrode has a good response at + 0.95 V (vs. SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N = 3) ranging from 3.0 × 10^?8 g mL^?1 to 1.0 × 10^?7 g mL^?1. The method has been successfully applied to the analysis of real samples.     

Study on the Electrochemical Behavior of Dopamine and Uric Acid at a 2‐Amino‐5‐mercapto‐[1,3,4] Triazole Self‐Assembled Monolayers Electrode

Selected from a series of structurally related heteroaromatic thiols, a newly synthesized reagent 2‐amino‐5‐mercapto‐[1,3,4] triazole (MATZ) was used to fabricate self‐assembled monolayers (SAMs) on gold electrode for the first time. The MATZ/Au SAMs was characterized by electrochemical methods and scanning electronic microscopy (SEM). In 0.04 mol/L Britton–Robinson buffer solution (pH 5), the electrochemical behavior of dopamine showed a quasireversible process at the MATZ/Au SAMs with an electrode kinetic constant 0.1049 cm/s. However, the electrochemical reaction of uric acid at the SAMs electrode showed an irreversible oxidation process, the charge‐transfer kinetics of uric acid was promoted by the SAMs. By Osteryoung square‐wave voltammetry (OSWV), the simultaneous determination of dopamine and uric acid can be accomplished with an oxidation peak separation of 0.24 V, the peak current of dopamine and uric acid were linearly to its concentration in the range of 2.5×10^?6–5.0×10^?4 mol/L for dopamine and 1×10^?6–1×10^?4 mol/L for uric acid with a detection limit of 8.0×10^?7 mol/L for dopamine and 7.0×10^?7 mol/L for uric acid. The MATZ/Au SAMs electrode was used to detect the content of uric acid in real urine and serum sample with satisfactory results.     

Fast Determination of Ethylendiamine in Aminophylline Tablets by Small-sized Capillary Electrophoresis with Amperometric Detection

A novel method for fast determination of ethylendiamine (EDA) in Aminophylline Tablets has been developed by small‐sized capillary electrophoresis with amperometric detection (small‐CE‐AD) coupled with field‐amplified sample injection (FASI). Under the optimum conditions, EDA and four aliphatic diamine homologs (1,3‐diaminopropane, 1,4‐diaminobutane, 1,5‐diaminopentane and 1,6‐diaminohexane) could be well separated within 6 min at a separation voltage of 2.0 kV in an acetate buffer solution of pH 3.8 with low limit of detection (LOD) of 1.3×10^?11 g/mL for EDA (S/N=3). The proposed method has been successfully applied to direct determination of EDA content in different batches of Aminophylline Tablets. The method does not require off‐line preconcentration and derivatization steps, which should find wide application fields including pharmaceuticals as an alternative to conventional and microchip CE approaches.     

Application of ionic liquid as additive in determination of three β‐agonists by capillary electrophoresis with amperometric detection

CE coupled with amperometric detection method was developed using ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMImBF₄) as additive for the simultaneous detection of clenbuterol (CLB), terbutaline (TER), and ractopamine (RAC) in feed. The effects of detection potential, concentration of EMImBF₄, pH, and concentration of the running buffer, separation voltage as well as injection time on the separation and detection of these three β‐agonists were investigated in detail. Under the optimum conditions: the detection potential at 1.05 V, 50 mmol/L Tris‐HAc at pH 8.0 with 0.6% (v/v) EMImBF₄, electrokinetic injection 6 s at 16 kV and separation voltage at 16 kV, a baseline separation for these three analytes could be achieved within 11 min. Introduction of EMImBF₄ into the running buffer resulted in significant improvement in separation selectivity and enhancement in peak currents for those β‐agonists, especially for TER and RAC, which could not be separated in the running buffer without additive. The method exhibited wide linear range with LOD (S/N = 3) of 2, 1, and 2 nmol/L for CLB, TER, and RAC, respectively. The precision was determined in both intraday (n = 5) and interday (n = 3) assays, and the RSDs for both migration time and peak current were less than 6%. The proposed method was also applied to analyze β‐agonists in feed sample.     

Electrochemical Behavior and Determination of L‐Tyrosine at Single‐walled Carbon Nanotubes Modified Glassy Carbon Electrode

Based on single‐walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE/SWCNTs), a novel method was presented for the determination of L ‐tyrosine. The GCE/SWCNTs exhibited remarkable catalytic and enhanced effects on the oxidation of L ‐tyrosine. In 0.10 mol/L citric acid‐sodium citrate buffer solution, the oxidation potential of L ‐tyrosine shifted negatively from +1.23 V at bare GCE to +0.76 V at GCE/SWCNTs. Under the optimized experimental conditions, the linear range of the modified electrode to the concentration of L ‐tyrosine was 5.0×10^?6–2.0×10^?5 mol/L (R₁=0.9952) and 2.7×10^?5–2.6×10^?4 mol/L (R₂=0.9998) with a detection limit of 9.3×10^?8 mol/L. The kinetic parameters such as α (charge transfer coefficient) and D (diffusion coefficient) were evaluated to be 0.66, 9.82×10^?5 cm² s^?1, respectively. And the electrochemical mechanism of L ‐tyrosine was also discussed.