Determination of puerarin and daidzein in Puerariae radix and its medicinal preparations by micellar electrokinetic capillary chromatography with electrochemical detection

The use of micellar electrokinetic capillary chromatography (MECC) with electrochemical detection is described for the determination of puerarin and daidzein in Puerariae radix and its medicinal preparations. Operated in a wall-jet configuration, a 300 μm diameter carbon-disk electrode was used as the working electrode, which exhibits good responses at +900 mV (versus SCE) for the two analytes. Under the optimum conditions, the analytes were base-line separated within 11 min in a sodium dodecyl sulphate—borax (pH 7.8) running buffer, and excellent linearity was obtained in the concentration range from 5.0×10⁻⁴ to 5.0×10⁻⁶ mol/l. The detection limit (S/N=3) was 6×10⁻⁷ and 1.1×10⁻⁶ mol/l for puerarin and daidzein, respectively. This work provides a useful method for the analysis of traditional Chinese medicines.     

毛细管电泳-电化学检测法测定饲料中的磺胺类药物

采用毛细管电泳-电化学检测法(CE-ED),对饲料中的6种磺胺类药物磺胺脒、磺胺二甲嘧啶、磺胺甲嘧啶、磺胺二甲氧嘧啶、磺胺嘧啶、磺胺甲恶唑进行了分离和测定。分别考察了工作电极电位、运行缓冲液的pH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300μm的碳圆盘电极为工作电极,检测电位为0.95 V(vs.SCE),在30 mmol/L硼砂-KH2PO4(pH7.6)的运行缓冲溶液中,6个分析物能够在16 min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,检出限(S/N=3)范围0.08～0.20μg/mL。该方法已应用于实际样品的分析。     

毛细管电泳电化学检测法测定烟草中的多元酚

采用毛细管电泳电化学检测法同时测定了烟草中的多元酚,即芦丁、绿原酸,槲皮素和咖啡酸。考察了工作电极的氧化电位、运行缓冲溶液浓度和pH值,分离电压和进样时间对分离和检测的影响。在优化条件下,以300μm直径的碳圆盘电极为工作电极,检测电位为+0.9 V(vs.SCE),在50 mmol/L硼酸盐(pH 8.4)的运行缓冲液中,被测物浓度与峰电流在三个数量级范围内呈良好线性,检出限为2×10-7或5×10-7g/mL。方法有着良好的重现性,被测组分的迁移时间和峰高的相对标准偏差(RSDs)小于4%(n=7)。单次测定可在16 min内完成,已用于实际样品多元酚的测定,样品处理简单,无须预富集。     

Determination of diclofenac sodium by capillary zone electrophoresis with electrochemical detection

Capillary zone electrophoresis was employed for the determination of diclofenac sodium using an end-column amperometric detection with a carbon fiber microelectrode, at a constant potential of 0.83 V vs. saturated calomel electrode. The optimum conditions of separation and detection are 4.90 x 10(-3) mol/l Na2HPO4-3.10 x 10(-3) mol/l NaH2PO4 (pH 7.0) for the buffer solution, 10 kV for the separation voltage, 5 kV and 10 s for the injection voltage and the injection time, respectively. The limit of detection is 2.5 x 10(-6) mol/l or 5.2 fmol (S/N=2). The relative standard deviation is 0.8% for the migration time and 4.7% for the electrophoretic peak current. The method was applied to the determination of diclofenac sodium in human urine.     

Determination of enkephalin peptides by nonaqueous capillary electrophoresis with electrochemical detection

Nonaqueous capillary electrophoresis with electrochemical detection (NACE-ED) was applied to the analysis of enkephalin peptides. The effect of different buffer compositions on the electrophoretic behavior of methionine enkephalin, leucine enkephalin, and [D-Ala2]-leucine enkephalin was studied. Separation of the protonated and the deprotonated peptides was obtained using ACN/methanol-based electrolyte systems. The electrochemical behavior of the enkephalins was studied by the capillary batch injection analysis technique. NACE-ED yielded well-defined signals in the oxidation mode only for the negatively charged analytes. The optimized BGE for the counterelectroosmotic separation consisted of 10 mM ammonium acetate in ACN/methanol (3:1 v/v). Using a platinum microdisk electrode set to an actual potential of +0.65 V detection limits in the submicromolar range were observed which are about one order of magnitude lower compared to UV detection. Problems concerning EOF instability and electrode fouling caused by water and other neutral sample impurities transported by the EOF can be avoided in the EOF-inverted mode using poly(ethylene glycol)-coated capillaries and an actual working electrode potential of +1.0 V. For the quantification of the enkephalins [D-Ala2]leucine enkephalin was used as internal standard. The practical utility for the determination of enkephalins in spiked plasma samples after SPE was demonstrated.     

Determination of diethylene glycol in toothpaste by capillary electrophoresis with electrochemical detection

Microchimica Acta - Diethylene glycol (DEG) can be determined in toothpaste via capillary electrophoresis at 16 kV using a fused silica capillary of 75 cm length and of...     

Determination of sulfadiazine and sulfamethoxazole by capillary electrophoresis with end-column electrochemical detection.

Capillary electrophoresis (CE) with end-column electrochemical detection (EC) of sulfadiazine (SDZ) and sulfamethoxazole (SMZ) is described. Under the optimum conditions, SDZ and SMZ were separated satisfactorily, and a highly sensitive and stable response was obtained at a potential of 1.1 V versus Ag/AgCl. Optimized end-column detection provides detection limits as low as 0.1 microM for both compounds, which corresponds to 0.024 and 0.021 fmol with peak efficiencies of 394,000 and 335,000 theoretical plates for SDZ and SMZ, respectively. The calibration graph was linear over three order of magnitude. The relative standard deviations (n = 12) of peak currents and migration times were 2.3 and 2.7%, and 0.8 and 1.3%, respectively, for the two compounds. The proposed method was applied to the analysis of tablets and human urine samples with satisfactory results.     

Determination of textile dyes by means of non-aqueous capillary electrophoresis with electrochemical detection

Eight textile dye compounds including five cationic dyes, namely, basic blue 41, basic blue 9, basic green 4, basic violet 16 and basic violet 3, and three anionic dyes, acid green 25, acid red 1 and acid blue 324, were separated and detected by non-aqueous capillary electrophoresis (NACE) with electrochemical detection. Simultaneous separations of acid and basic dyes were performed using an acetonitrile-based buffer. Particular attention was paid to the determination of basic textile dyes. The optimized electrophoresis buffer for the separation of basic dyes was a solvent mixture of acetonitrile/methanol (75:25, v/v) containing 1 M acetic acid and 10 mM sodium acetate. The limits of detection for the basic dyes were in the range of 0.1–0.7 μg mL⁻¹. An appropriate solid-phase extraction procedure was developed for the pre-treatment of aqueous samples with different matrices. This analytical approach was successfully applied to various water samples including river and lake water which were spiked with textile dyes.     

毛细管电泳电化学检测法同时测定三种氨基酸的电离常数

利用自制微圆盘铜电极,建立了一种毛细管电泳电化学检测同时测定色氨酸、丝氨酸和半胱氨酸pKα值的新方法。在不同pH条件下测定各氨基酸的有效淌度（μeff）,利用Origin软件对μeff-[H^＋]按理论关系式进行非线性拟合,得到其pKα值。该方法简便、快速,测定值与文献值符合良好。     

Determination of flavonoids in Houttuynia cordata Thunb. and Saururus chinensis (Lour.) Bail. by capillary electrophoresis with electrochemical detection

Four flavonoids (rutin, hyperoside, quercitrin and quercetin) in Houttuynia cordata Thunb. and Saururus chinensis (Lour.) Bail. were determined by capillary electrophoresis with wall-jet amperometric detection. The working electrode was a 500 μm diameter carbon disc electrode and the detection potential was +0.95 V (versus Ag/AgCl). Effects of several important factors, such as the running buffer and its corresponding pH and concentration, separation voltage, injection time were investigated to acquire the optimum conditions for separation of these four flavonoids. Baseline separation for the four flavonoids was obtained within 21 min in a 60 cm length capillary at a separation voltage of 15 kV with a 60 mmoL/L Na₂B₄O₇-120 mmoL/L NaH₂PO₄ buffer (pH 8.8) as running buffer. The relationship between peak currents and analyte concentrations was linear over about two orders of magnitude with detection limits (defined as S/N = 3) ranging from 0.02 to 0.05 μg/mL for all analytes. This method was applied for the determination of the above four flavonoids in H. cordata Thunb. and S. chinensis (Lour.) Bail. with simple extraction procedures, and the assay results were satisfactory.     

Determination of the active ingredients in Gastrodia rhizoma by capillary electrophoresis with electrochemical detection

A simple, reliable and reproducible method, based on capillary electrophoresis (CE) with electrochemical detection (ED), for the determination of five active ingredients and three carbohydrates in extracts of Gastrodia rhizoma is described in this work. The main active ingredients are gastrodin, 4-hydroxybenzyl alcohol, vanillyl alcohol, 4-hydroxybenzylaldehyde and vanillin. Operated in a wall-jet configuration, a 300 microm diameter carbon disc electrode was used as a working electrode, with a good response at +1000 mV (vs. SCE) for 4-hydroxybenzyl alcohol, vanillyl alcohol, 4-hydroxybenzylaldehyde and vanillin; a 300 microm diameter copper disc electrode exhibits a good response at +650 mV (vs. SCE) for gastrodin, sucrose, glucose and fructose. Under optimum conditions, 4-hydroxybenzyl alcohol, vanillyl alcohol, 4-hydroxybenzylaldehyde and vanillin in 100 mmol l(-1) borate buffer (pH 9.2) and gastrodin, sucrose, glucose and fructose in 50 mmol l(-1) sodium hydroxide buffer were baseline separated within 18 min. The response was linear over two orders of magnitude with a detection limit (S/N = 3) in the range 3 x 10(-7)-1.8 x 10(-6) mol l(-1) for all eight analytes. This method was successfully used in the analysis of traditional Chinese medicine, and the assay results were satisfactory.     

Determination of tryptophan and kynurenine in brain microdialysis samples by capillary electrophoresis with electrochemical detection

Capillary electrophoresis with electrochemical detection (CEEC) is evaluated for the determination of tryptophan and kynurenine in microdialysis samples obtained from rat brain. These compounds were separated from all other electroactive metabolites of tryptophan. Limits of detection for both compounds were in the low attomole range. The response was linear for kynurenine between 4.9 and 980 fmol injected with a correlation coefficient of 0.9992 (n = 12). The system was evaluated for monitoring tryptophan and kynurenine in the extracellular fluid of the rat brain following systemic administration of tryptophan.     

Determination of active ingredients in hawthorn and hawthorn piece by capillary electrophoresis with electrochemical detection

Capillary-zone electrophoresis with electrochemical detection has been used for the separation and determination of (-)-epicatechin, rutin, hyperin, chlorogenic acid, and quercetin in hawthorn and hawthorn piece. The effects of several important factors, including the running buffer acidity, the separation voltage, and the working electrode potential, were evaluated to acquire the optimum analytical conditions. The working electrode was a 300-μm carbon-disk electrode at a working potential of +0.95 V (vs. SCE). Under the optimum conditions, the analytes can be well separated within 16 min in a 75-cm-long fused-silica capillary. The current response was linear over two orders of magnitude with detection limits (S/N = 3) ranging from 6.00 × 10⁻⁸ to 3.75 × 10⁻⁷ g/mL for all analytes. The method was successfully used in the analysis of hawthorn and hawthorn piece and the assay results were satisfactory. The text was submitted by the authors in English.     

Determination of hesperidin and synephrine in Pericarpium Citri Reticulatae by capillary electrophoresis with electrochemical detection

A method based on capillary electrophoresis with electrochemical detection (CE-ED) has been developed for the determination of hesperidin (HP) and synephrine (SP) in the Chinese traditional herbal drug, Pericarpium Citri Reticulatae, the dried rind of the ripe fruits of Citrus reticulata Blanco (mandarin orange). The effects of some important factors such as the acidity and concentration of running buffer, separation voltage, and detection potential were investigated to determine the optimum conditions. The working electrode was a 300 microm diameter carbon disc electrode positioned opposite the outlet of the capillary. Both analytes could be well separated within 5 min in a 40 cm long capillary at a separation voltage of 12 kV in 50 mmol L(-1) borate buffer (pH 9.0). Excellent linearity was observed for the dependence of peak current on analyte concentration in the range from 2.5 x 10(-6) to 1.0 x 10(-3) mol L(-1) for SP and from 5.0 x 10(-6) to 1.0 x 10(-3) mol L(-1) for HP. The detection limits (S/N=3) for SP and HP were 4.96 x 10(-7) mol L(-1) and 6.54 x 10(-7) mol L(-1), respectively. This method has been successfully applied for the analysis of real samples, with satisfactory results.     

Determination of aromatic amines in water samples by capillary electrophoresis with electrochemical and fluorescence detection

Two capillary electrophoresis methods have been compared for the determination of aniline derivatives in environmental water samples. With the first method the anilines were separated as cations by free zone electrophoresis at low pH, and detected by amperometry. For this, the separation capillary was connected through a palladium field decoupler to an electrochemical detection cell which had been modified to match the volume scale of the separation. Most anilines tested, except chlorinated compounds, could be detected with full sensitivity at a detection potential of +0.7 V. Detection limits with this detection scheme were on a low microg/l level. The alternative method involved the derivatization of the anilines with fluorescamine, the separation of the derivatives formed by micellar electrokinetic chromatography, and fluorescence detection. For detection a lamp-based, fibre optics instrument was used. Detection limits with fluorimetry were comparable with those obtained with amperometric detection (in the order of 1 microg/l). Still, this method was preferred since it gave a higher separation efficiency and shorter analysis times (approximately 4 min). The most important argument, however, was its higher reliability and ease-of-handling. Preliminary experiments with water samples collected in areas where pollution with anilines may be expected showed that the method is highly specific, with few interferences showing up in the electropherograms.     

Determination of monoamine transmitters and tyrosine in biological samples by capillary electrophoresis with electrochemical detection

Summary Capillary electrophoresis (CE) has been employed for the separation of monoamine transmitters (MAs) and tyrosine (Tyr), combined with electrochemical detection (ED) at a carbon disc electrode. The effects of several factors such as the acidity and concentration of running buffer, the separation voltage, the potential applied to the working electrode and the injection time were investigated to find the optimum conditions. Detection limits (S/N=3) ranged from 48.8 to 315.4 nmol·L⁻¹, and the response was linear over 3 order of magnitude for MAs and Tyr. The proposed method was successfully applied to determine MAs and Tyr in the cerebral cortex, thalamus and spinal cord of rats with satisfactory assay results.     

Determination of rutin and forsythin in fruit ofForsythia suspensa(Thunb.) Vahl by capillary electrophoresis-electrochemical detection

Summary Capillary electrophoresis-amperometric detection is evaluated for simultaneous determination of rutin and forsythin. The cyclic voltammogram, hydrodynamic voltammogram, effect of pH, buffer concentration and SDS, and percent organic modifier on separation and detection were studied. Conditions were optimized as follows: 1.2 V detection potential; separation at 12 kV; 5 s at 15 kV for sample injection time and sample injection voltage; mobile phase 20 mM boric acid buffer; pH 8.4, containing 40 mM SDS and 10% (v/v) acetontrile. The method gave low detection limit as 0.001 mg mL⁻¹ and 0.0005 mg mL⁻¹ (S/N=3), wide linear range 0.005–0.5 mg mL⁻¹ for rutin and forsythin, respectively. The relative standard deviations of peak current and migration time for 8 consecutive injections of the standard solution containing 0.1 mg mL⁻¹ each compound were 4.78%, 3.63% and 6.40%, 2.95% for rutin and forsythin, respectively. In addition, levels of the two compounds in traditional Chinese herbal drugs were easily determined.     

Separation and determination of rutin and quercetin in the flowers ofSophora japonica L. by capillary electrophoresis with electrochemical detection

Summary Capillary electrophoresis with amperometric detection has been evaluated for the simultaneous determination of rutin and quercetin. The cyclic voltammogram, hydrodynamic voltammogram, and the effects of pH, concentration of buffer and sodium dodecyl sulfate (SDS), and amount of organic modifier on the separation and the detection were studied. The optimized conditions were: detection potential 1.2V, separation at 12 kV, 5 s at 15 kV for sample injection, running electrolyte 20 mmol L⁻¹ borate buffer, pH 8.8, containing 40 mmol L⁻¹ SDS and 10% acetonitrile. The detection limit of the method was low, 0.001 and 0.0005 mg mL⁻¹, for rutin and quercetin, respectively; the linear ranges were wide −0.005–0.5 and 0.005–0.4 mg mL⁻¹, respectively. The variations in peak current and migration time for eight consecutive injections of a standard solution containing 0.1 mg mL⁻¹ of each compound were 4.78 and 3.63%, and 6.50 and 2.59% for rutin and quercetin, respectively. The levels of the two compounds in traditional Chinese herbal drugs were easily determined.     

毛细管电泳安培检测法测定儿茶中的儿茶素,表儿茶素

用毛细管电泳安培检测法同时测定了中药儿茶中儿茶素和表儿茶素的含量,研究了各种实验条件对分离效果的影响,得到了优化的实验条件.以直径为50 μm的碳纤维微电极为工作电极,电极电位为+1.2V(vs.Ag/AgCl),20mmol/L的Na2B4O7-H3BO3(pH值为8.4)+80 mmol/L SDS为缓冲溶液.在此条件下,儿茶素和表儿茶素在10 min内得到了良好的分离.儿茶素和表儿茶素分别在5.0×10-3～0.5mg/mL浓度范围内与电泳峰电流呈现良好线性关系,检测下限分别为0.1 mg/mL和0.05 mg/mL.将之应用于实际样品的测定.