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.     

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.     

Application of Polymer‐Modified Hanging Mercury Drop Electrode in the Indirect Determination of Certain β‐Lactam Antibiotics by Differential Pulse,Ion‐Exchange Voltammetry

A selective and sensitive polymer‐modified electrode was developed for β‐lactam antibiotics (cefaclor, amoxycillin and ampicillin) present in formulated and blood plasma samples for the quantitative analysis in aqueous environment. The detection was made using an ion‐exchange voltammetric technique, in differential pulse mode, on poly(N‐chloranil N,N,N′,N′‐tetramethylethylene diammonium dichloride)‐modified hanging mercury drop electrode of a three‐electrode system (PAR Model 303A) attached with a Polarographic Analyzer/Stripping Voltammeter (PAR Model 264A). Antibiotics, which are electroinactive compounds, were essentially converted to their electroactive oxazolone analogues through acid treatment under drastic conditions (0.1 mol L^?1 HCl, ～85 °C, 2 h). These analytes in the form of their respective oxazolones were indirectly analyzed by oxazolone entrapment in the polymeric film through ion‐exchange process at modified electrode surface (accumulation potential ?0.20 V (vs. Ag/AgCl), accumulation time 120 s, pH 7.4, KH₂PO₄‐NaOH buffer (ionic strength 0.1 mol L^?1), scan rate 10 mV s^?1, pulse amplitude 25 mV). The limit of detection of cefaclor‐derived oxazolone was found to be 2.12 nmol L^?1 (0.82 ppb, S/N 3, RSD 3.21%) in terms of cefaclor (a representative β‐lactam) concentration.     

Simultaneous Determination of Ranitidine and Metronidazole at Glassy Carbon Electrode Modified with Single Wall Carbon Nanotubes

Single‐walled carbon nanotubes(SWCNTs) were dispersed into DMSO, and a SWCNTs‐film coated glassy carbon electrode was achieved via evaporating the solvent. The results indicated that CNT modified glassy carbon electrode exhibited efficiently electrocatalytic reduction for ranitidine and metronidazole with relatively high sensitivity, stability and life time. Under conditions of cyclic voltammetry, the potential for reduction of selected analytes is lowered by approximately 150 mV and current is enhanced significantly (7 times) in comparison to the bare glassy carbon electrode. The electrocatalytic behavior is further exploited as a sensitive detection scheme for these analytes determinations by hydrodynamic amperometry. Under optimized condition in amperometric method the concentration calibration range, detection limit and sensitivity were about, 0.1–200 μM, detection limit (S/N=3) 6.3×10^?8 mol L^?1 and sensitivity 40 nA/μM for metronidazole and 0.3–270 μM 7.73×10^?8 mol L^?1 and 25 nA/μM for ranitidine. In addition, the ability of the modified electrode for simultaneous determination of ranitidine and metronidazole was evaluated. The proposed method was successfully applied to ranitidine and metronidazole determination in tablets. The analytical performance of this sensor has been evaluated for detection of these analytes in serum as a real sample.     

Development of an Amperometric Biosensor for β‐N‐Oxalyl‐L‐α,β‐Diaminopropionic Acid (β‐ODAP)

An amperometric method for the determination of the neurotoxic amino acid β‐N‐oxalyl‐L ‐α,β‐diaminopropionic acid (β‐ODAP) using a screen printed carbon electrode (SPCE) is reported. The electrode material was bulk‐modified with manganese dioxide and used as a detector in flow injection analysis (FIA). The enzyme glutamate oxidase (GlOx) was immobilized in a Nafion‐film on the electrode surface. The performance of the biosensor was optimized using glutamate as an analyte. Optimum parameters were found as: operational potential 440 mV (vs. Ag/AgCl), flow rate 0.2 mL min^?1, and carrier composition 0.1 mol L^?1 phosphate buffer (pH 7.75). The same conditions were used for the determination of β‐ODAP. The signal was linear within the concentration range 53–855 μmol L^?1 glutamate and 195–1950 μmol L^?1 β‐ODAP. Detection limits (as 3σ value) for both analytes were 9.12 and 111.0 μmol L^?1, respectively, with corresponding relative standard deviations of 3.3 and 4.5%. The biosensor retained more than 73% of its activity after 40 days of on‐line use.     

Electrocatalytic Oxidation of Acyclovir on Poly(p‐Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode

Acyclovir is an antiviral effective drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p‐aminobenzene sulfonic acid (p‐ABSA) in phosphate buffer solution (PBS). The polymer film‐modified electrode was used to electrochemically detect acyclovir. Polymer film showed excellent electrocatalytic activity for the oxidation of acyclovir. The anodic peak potential value of the acyclovir at the poly(p‐ABSA) modified glassy carbon electrode was 950 mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the acyclovir concentration range 2×10^?7–9×10^?6 mol L^?1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 5.57×10^?8 and 1.85×10^?7 mol L^?1 respectively. The proposed method exhibits good recovery and reproducibility.     

Determination of Active Components in St. John's Wort (Hypericum Perforatum) by Capillary Electrophoresis with Electrochemical Detection

St. John's Wort (Hypericum perforatum) is a medicinal plant which has been known in traditional medicine as an anti‐inflammatory and healing agent. Nowadays, the alcoholic extract of its aerial parts finds wide application for its antidepressant activity. A capillary electrophoresis method for the identification of its constituents using electrochemical detection was developed. Effects of several important factors were investigated to acquire the optimum conditions. The working electrode was a 300 μm carbon disc electrode at a working potential of +0.90 V (vs. SCE). The analytes can be well separated within 20 min in a 75 cm length fused‐sillica capillary at a separation of 16 kV in 50 mmol L^?1 borate buffer (pH=9.0). The current response was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 0.2 to 0.5 mg L^?1 for all the analytes. The method was successfully used in the analysis of Hypericum perforatum with relatively simple extraction procedures, and the assay results were satisfactory.     

Simultaneous Detection of Dopamine and Uric Acid under Coexistence of Ascorbic Acid with DNA/Pt Nanocluster Modified Electrode

A novel biosensor by electrochemically codeposited Pt nanoclusters and DNA film was constructed and applied to detection of dopamine (DA) and uric acid (UA) in the presence of high concentration ascorbic acid (AA). Scanning electron microscopy and X‐ray photoelectron spectroscopy were used for characterization. This electrode was successfully used to resolve the overlapping voltammetric response of DA, UA and AA into three well‐defined peaks with a large anodic peak difference (ΔE_pa) of about 184 mV for DA and 324 mV for UA. The catalytic peak current obtained from differential pulse voltammetry was linearly dependent on the DA concentration from 1.1× 10^?7 to 3.8×10^?5 mol·L^?1 with a detection limit of 3.6×10^?8 mol·L^?1 (S/N=3) and on the UA concentration from 3.0×10^?7 to 5.7×10^?5 mol·L^?1 with a detection limit of 1.0×10^?7 mol·L^?1 with coexistence of 1.0×10^?3 mol·L^?1 AA. The modified electrode shows good sensitivity and selectivity.     

Preparation of Polypyrrole/Nuclear Fast Red Films on Gold Electrode and Its Application on the Electrocatalytic Determination of Methyl‐dopa and Ascorbic Acid

A novel voltammetric method using the Ppyox/NFR/Au (poly pyrrole – nuclear fast red – gold) modified electrode was developed for simultaneous measurement of various combinations of ascorbic acid (AA) and methyldopa (MDA). Polypyrrole film was prepared by incorporation of nuclear fast red (NFR) as doping anion, during the electropolymerization of pyrrole onto a gold (Au) electrode in aqueous solution using cyclic voltammetric (CV) method, and then it was overoxidized at constant potential. Differential pulse voltammetry was utilized for the measurement of both analytes using modified electrode. Well‐separated voltammetric peaks were observed for ascorbic acid (AA) and methyldopa at the Ppyox/NFR/Au modified electrodes with peak separation of 0.210 V. It has been found that under optimum condition (pH 3.0), the oxidation of AA and MDA at the surface of the electrode occurs at a potential about 260 and 50 mV less positive than unmodified Au electrode respectively. The current catalytic oxidation peaks showed a linear dependent on the concentration of AA and MDA in the range of 9.0×10^?6 to 1.0×10^?3 and 1.0×10^?7 to 2.0×10^?5 mol L^?1 respectively. The detection limit of 5.8×10^?6 and 5.0×10^?8 mol L^?1 (S/N=3) were obtained for AA and MDA respectively. The modified electrode was used for determination of AA and MDA in some real samples such as human serum and tablet.     

Simultaneous Determination of Ascorbic Acid and Uric Acid by Using a PVC/TTF‐TCNQ Composite Electrode as Detector in a FIA System

A PVC/TTF‐TCNQ composite electrode has been employed as detector in a flow injection system. The proposed method allows the simultaneous detection of ascorbic acid (AA) and uric acid (UA) in mixtures by using a FIA system in a simple manner, without pre‐treatment or modified electrode. This method is based on the amperometric determination of (a) ascorbic acid at 0.15 V and (b) both analytes at 0.35 V, being the response linear in the range 1×10^?2–4×10^?4 M for both analytes with detection limits (S/N=3) of 1.2×10^?4 M and 8.1×10^?5 M for AA and UA, respectively.     

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.     

Determination of phenoxy herbicides in water samples using phase transfer microextraction with simultaneous derivatization followed by GC‐MS analysis

A sensitive and accurate method for the determination of two model phenoxy herbicides, 4‐chloro‐2‐methylphenoxy acetic acid and 4‐chloro‐2‐methylphenoxy propanoic acid, in water is explained. This method utilizes a simple phase transfer catalyst‐assisted microextraction with simultaneous derivatization. Factors affecting the performance of this method including pH of the aqueous matrix, temperature, extraction duration, type and amount of derivatization reagents, and type and amount of the phase transfer catalyst are examined. Derivatization and the use of phase transfer catalyst have proven to be especially vital for the resolution of the analytes and their sensitive determination, with an enrichment factor of 288‐fold for catalyzed over noncatalyzed procedure. Good linearity ranging from 0.1 to 80 μg L^?1 with correlation of determination (r²) between 0.9890 and 0.9945 were obtained. Previous reported detection limits are compared with our new current method. The low LOD for the two analytes (0.80 ng L^?1 for 4‐chloro‐2‐methylphenoxy propanoic acid and 3.04 ng L^?1 for 4‐chloro‐2‐methylphenoxy acetic acid) allow for the determination of low concentrations of these analytes in real samples. The absence of matrix effect was confirmed through relative recovery calculations. Application of the method to seawater and tap water samples was tested, but only 4‐chloro‐2‐methylphenoxy propanoic acid at concentrations between 0.27 ± 0.01 and 0.84 ± 0.06 μg L^?1 was detected in seawater samples.     

N‐(3,4‐Dihydroxyphenethyl)‐3,5‐dinitrobenzamide‐Modified Multiwall Carbon Nanotubes Paste Electrode as a Novel Sensor for Simultaneous Determination of Penicillamine,Uric acid,and Tryptophan

N‐(3,4‐dihydroxyphenethyl)‐3,5‐dinitrobenzamide modified multiwall carbon nanotubes paste electrode was used as a voltammetric sensor for oxidation of penicillamine (PA), uric acid (UA) and tryptophan (TP). In a mixture of PA, UA and TP, those voltammograms were well separated from each other with potential differences of 300, 610, and 310 mV, respectively. The peak currents were linearly dependent on PA, UA and TP concentrations in the range of 0.05–300, 5–420, and 1.0–400 µmol L^?1, with detection limits of 0.021, 2.0, and 0.82 µmol L^?1, respectively. The modified electrode was used for the determination of those compounds in real samples.     

Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl)ruthenium(II) Immobilized in Humic Acid‐Silica‐Poly(vinyl alcohol) Composite Films

In this paper, we report the first attempt to use humic acid (HA) as modifiers to prepare the organic‐inorganic hybrid modified glassy carbon electrodes based on HA‐silica‐PVA (poly(vinyl alcohol)) sol‐gel composite. Electroactive species of tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy) ) can easily incorporate into the HA‐silica‐PVA films to form Ru(bpy) modified electrodes. The amount of Ru(bpy) incorporated in the composite films strongly depends on the amount of HA in the hybrid sol. Electrochemical and electrogenerated chemiluminescence (ECL) of Ru(bpy) immobilized in HA‐silica composite films coated on a glassy carbon electrode have been studied with tripropylamine (TPA) as the coreactant. The analytical performance of this modified electrode was evaluated in a flow injection analysis (FIA) system with a homemade flow cell. The as‐prepared electrode showed good stability and high sensitivity. The detection limits (S/N=3) were 0.050 μmol L^?1 for TPA and 0.20 μmol L^?1 for oxalate, and the linear ranges were from 0.10 μmol L^?1 to 1.0 mmol L^?1 for TPA and from 1.0 μmol L^?1 to 1.0 mmol L^?1 for oxalate, respectively. The resulting electrodes were stable over two months.     

Simultaneous Determination of Rosmarinic Acid and Protocatechuic Acid at Poly(o‐Phenylenediamine)/Pt Nanoparticles Modified Glassy Carbon Electrode

A system of Pt nanoparticles and poly(ortho‐phenylenediamine) film electrochemically deposited onto a glassy carbon electrode (GCE/PoPD/Pt) was fabricated. Scanning electron microscopy, Fourier‐transform infrared spectroscopy, and atomic force microscopy techniques were used to identify the surface characteristics of the composite electrode. The conductive polymers and Pt nanoparticles together resulted in a synergistic effect, and the new formed surface was highly active against polyphenolic structures. Rosmarinic acid (RA) and protocatechuic acid (PCA) are phenolic compounds found in plants, and they are used in many applications, particularly as pharmaceuticals. The GCE/PoPD/Pt was used for the simultaneous determination of RA and PCA in a pH 2.0 H₂SO₄ solution for the first time. The RA and PCA concentrations were determined using differential pulse voltammetry (DPV) and chronoamperometry. By the amperometry measurement, for RA and PCA, a linear relation was observed in the concentration ranges of 1–55 μmol L^?1 and 1–60 μmol L^?1, with detection limits of 0.5 μmol L^?1 and 0.6 μmol L^?1, respectively. In the simultaneous determination with DPV, the detection limits for both RA and PCA were calculated as 0.7 μmol L^?1. The GCE/PoPD/Pt was successfully used for the simultaneous determination of RA and PCA in a real sample, and its accuracy was verified by high‐performance liquid chromatography studies.     

A New Amperometric Biosensor Based on HRP/Nano-Au/L-Cysteine/Poly（o-Aminobenzoic acid）-Membrane-Modified Platinum Electrode for the Determination of Hydrogen Peroxide

The third generation amperometric biosensor for the determination of hydrogen peroxide （H2O2） has been described. For the fabrication of biosensor, o-aminobenzoic acid （oABA） was first electropolymerized on the surface of platinum （Pt） electrode as an electrostatic repulsion layer to reject interferences. Horseradish peroxidase （HRP） absorbed by nano-scaled particulate gold （nano-Au） was immobilized on the electrode modified with polymerized o-aminobenzoic acid （poABA） with L-cysteine as a linker to prepare a biosensor for the detection of H2O2. Amperometric detection of H2O2 was realized at a potential of ＋20 mV versus SCE. The resulting biosensor exhibited fast response, excellent reproducibility and sensibility, expanded linear range and low interferences. Temperature and pH dependence and stability of the sensor were investigated. The optimal sensor gave a linear response in the range of 2.99×10^-6 to 3.55×10^-3 mol·L^-1 to H2O2 with a sensibility of 0.0177 A·L^-1·mol^-1 and a detection limit （S/N = 3） of 4.3×10^-7 mol·L^-1. The biosensor demonstrated a 95% response within less than 10 s.     

Simultaneous Differential Pulse Voltammetric Determination of Ascorbic Acid and Caffeine in Pharmaceutical Formulations Using a Boron‐Doped Diamond Electrode

A cathodically pretreated boron‐doped diamond electrode was used for the simultaneous anodic determination of ascorbic acid (AA) and caffeine (CAF) by differential pulse voltammetry. Linear calibration curves (r=0.999) were obtained from 1.9×10^?5 to 2.1×10^?4 mol L^?1 for AA and from 9.7×10^?6 to 1.1×10^?4 mol L^?1 for CAF, with detection limits of 19 μmol L^?1 and 7.0 μmol L^?1, respectively. This method was successfully applied for the determination of AA and CAF in pharmaceutical formulations, with results equal to those obtained using a HPLC reference method.     

Selective Electrochemical Determination of Dopamine with Molecularly Imprinted Poly(Carbazole‐co‐Aniline) Electrode Decorated with Gold Nanoparticles

Dopamine (DA) is a significant neurotransmitter in the central nervous system, coexisting with uric acid (UA) and ascorbic acid (AA). UA and AA are easily oxidizable compounds having potentials close to that of DA for electrochemical analysis, resulting in overlapping voltammetric response. In this work, a novel molecularly imprinted (MI) electrochemical sensor was proposed for selective determination of DA (in the presence of up to 80‐fold excess of UA and AA), relying on gold nanoparticles (Au_nano)‐decorated glassy carbon (GC) electrode coated with poly(carbazole (Cz)‐co‐aniline (ANI)) copolymer film incorporating DA as template (DA imprinted‐GC/P(Cz‐co‐ANI)‐Au_nano electrode, DA‐MIP‐Au_nano electrode). The DA recognizing sensor electrode showed great electroactivity for analyte oxidation in 0.2 mol L^?1 pH 7 phosphate buffer. Square wave voltammetry (SWV) was performed within 10^?4–10^?5 mol L^?1 of DA, of which the oxidation peak potential was observed at 0.16 V. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0×10^?6 and 6.7×10^?6 mol L^?1, respectively. Binary and ternary synthetic mixtures of DA‐UA, DA‐AA and DA‐UA‐AA yielded excellent recoveries for DA. Additionally, DA was quantitatively recovered from a real sample of bovine serum spiked with DA, and determined in concentrated dopamine injection solution. The developed SWV method was statistically validated against a literature potentiodynamic method using a caffeic acid modified‐GC electrode.