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.     

反相高效液相色谱法测定一种口腔炎喷雾剂中绿原酸和咖啡酸的含量

取1mL口腔炎喷雾剂样品,用甲醇-水(1+1)溶液定量稀释至10mL,分取此溶液25μL供反相高效液相色谱法测定其绿原酸和咖啡酸含量。采用Shim-packVP-ODS色谱柱分离,以甲醇-0.012mol·L-1磷酸(27+73)混合溶液为流动相,柱温为30℃,流量为0.8mL·min-1,紫外检测器波长为323nm。结果表明:绿原酸在0.51～91.80mg·mL-1,咖啡酸在2.0～360.0mg·mL-1范围内呈线性关系,用标准加入法测定方法的回收率,结果依次在95.9%～97.4%和100.1%～100.9%范围内,检出限(3S/N)依次为0.10,0.40mg·mL-1,测定下限(10S/N)依次为0.36,1.40mg·mL-1。     

茶叶样品中绿原酸含量的高效液相色谱法测定

建立了茶叶绿原酸含量测定的择相高效液相色谱法,采用PecosphereC18柱,以甲醇－水（体积比18：20,水中含φ＝1／61的甲酸）淋洗,用紫外检测器于326nm处测定,各组分的色谱峰达到基线分离。绿原酸在0．02－4．02μg范围内线性关系良好,线性相关系数 r＝0．9996。在安徽黄山产贡菊和安徽产金银花中加标的回收率分别为86．8％、102．0％,该法已用于十多种茶趺实际样品的测定。     

向日葵仁中绿原酸和咖啡酸的反相高效液相色谱法测定

建立了同时测定向日葵仁中绿原酸和咖啡酸的反相高效液相色谱法 ;采用美国Alltech公司的ALLTIMAC18 柱(250mm×4.6mmID,5μm) ,流动相为乙腈 -2 %(φ)乙酸溶液 (体积比15∶85) ,流速为1.0mL/min ,紫外检测波长327nm ;向日葵仁中绿原酸(chlorogenicacid)和咖啡酸(caffeicacid)在18min内得到很好的分离 ,该法简便、快速、结果准确、重复性好。     

Selective and Simultaneous Voltammetric Determination of Glutathione,Uric Acid and Penicillamine by a Modified Carbon Nanotube Paste Electrode

In this paper, the use of a carbon paste electrode (CPE) modified by (E)‐3‐((2‐(2,4‐dinitrophenyl)hydrazono)methyl)benzene‐1,2‐diol (DHB) and carbon nanotubes (CNTs) for the determination of glutathione (GSH), uric acid (UA) and penicillamine (PA) is described. Initially, cyclic voltammetry was used to investigate the redox properties of the modified electrode in phosphate buffer. Next, the electrocatalytic oxidation of GSH via EC′ mechanism at the modified electrode was described. At the optimum pH of 7.0, the oxidation of GSH occurs at a potential that is 530 mV less positive than that of an unmodified carbon paste electrode. The values of the diffusion coefficient (D=2.5×10^?6 cm² s^?1) and the catalytic rate constant (k=1.7×10³ M^?1 s^?1) were calculated for GSH, using chronoamperometry. Based on differential pulse voltammetry, the oxidation of GSH exhibited a dynamic range between 0.4 and 700.0 µM and a detection limit (3σ) of 70.0 nM. Also, simultaneous determination of GSH, UA and PA was described at the modified electrode. Finally, this method was used for the determination of these substances in synthetic solutions and blood serum samples.     

聚对氨基苯磺酸修饰电极用于差分脉冲伏安法测定酪氨酸

采用电化学方法将对氨基苯磺酸聚合在玻碳电极表面制得聚对氨基苯磺酸修饰电极,并用循环伏安法和差分脉冲伏安法研究了酪氨酸在该修饰电极上的电化学行为。结果表明:在pH 7.00的磷酸盐缓冲溶液中,酪氨酸在0.478 V处出现一良好的氧化峰,且峰电流与酪氨酸浓度在1.0×10~(-7)～6.0×10~(-5)mol·L~(-1)范围内呈线性关系,检出限(3S/N)为2.0×10~(-8)mol·L~(-1)。方法用于测定人尿中酪氨酸的含量,回收率在91.5%～106.0%之间。     

毛细管电泳测定三精双黄连口服液中的黄芩甙元、黄芩甙、绿原酸和咖啡酸

建立了毛细管电泳法测定中药复方制剂双黄连口恨液中黄芩甙元、黄芩甙、绿原酸和咖啡酸的方法,通过研究缓冲溶液pH和浓度、分离电压、进样时间和有饥添加剂的影响优化了分析条件在优化的条件下,20min内实现了4种物质的良好分离黄芩甙元、黄芩甙、绿原酸和咖啡酸峰高和质量浓度分别在0．05～1．50、0.06～1．20、0．02～0．50和0．02～0．50g／L范围内呈良好线性;俭出限分别为0．015、0．020、0．004、0．004g／L基于迁移时间和峰高的重复性分别为：黄芩甙元,1．70％和3．94％;黄芩甙,1．60％和3．63％;绿原酸,1．60％和2．05％;咖啡酸,1．51％和2．83％通过分析实际样品并做加标回收实验验证了该方法的可行性。     

反相高效液相色谱法同时测定沙棘叶中绿原酸和芦丁

建立了同时测定沙棘叶中绿原酸和芦丁含量的反相高效液相色谱(RP-HPLC)法。采用Kromasil C18色谱柱(150×4.6mm,5μm),流动相为体积比20∶80的乙腈-1%乙酸水溶液,检测波长358nm。结果表明:绿原酸、芦丁的浓度分别在0.0284～0.1704mg.mL-1(r=0.9995)和0.0566～0.3396mg.mL-1(r=0.9992)范围内与色谱峰面积呈良好线性关系;平均加标回收率分别为100.5%(n=5)和98.5%(n=5)。该方法快速、准确,重现性好,可用于同时测定沙棘叶中绿原酸和芦丁含量。     

Electrocatalytic Characteristics of Ferrocenecarboxylic Acid Modified Carbon Paste Electrode in the Oxidation and Determination of L‐Cysteine

The electrochemical behavior of L ‐cysteine studied at the surface of ferrocenecarboxylic acid modified carbon paste electrode (FCMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of L ‐cysteine is occurs at a potential about 580 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and catalytic reaction rate constant, K′_h were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L ‐cysteine showed a linear dependent on the L ‐cysteine concentration and linear calibration curves were obtained in the ranges of 10^?5 M–10^?3 M and 4.1×10^?8 M–3.7×10^?5 M of L ‐cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (2δ) were determined as 2.4×10^?6 M and 2.5×10^?8 M by CV and DPV methods. This method was also examined for determination of L ‐cysteine in some samples, such as Soya protein powder, serum of human blood by using recovery and standard addition methods.     

毛细管电泳法测定复方鱼腥草片中的绿原酸和槲皮素

建立了毛细管电泳法分析复方鱼腥草片中绿原酸和槲皮素的方法,通过研究缓冲溶液酸度和浓度、工作电压和进样时间的影响优化了分析条件。在优化的条件下,15min内实现了两种分析物质的良好分离。绿原酸和槲皮素峰高和质量浓度分别在0．05～0．80g／L和0．05～1．00g／L范围内成良好线性。基于迁移时间和峰高的重复性(RSD)分别为：绿原酸,1．91％和4．32％;槲皮素,2．30％和3．18％。绿原酸和槲皮素的检出限(S／N=3)分别为0．014g／L和0．015g／L。通过分析实际样品并做加样回收实验进一步验证了该方法的可行性。     

A Boron Doped Diamond Electrode Modified with Nano‐carbon Black for the Sensitive Electrochemical Determination of Chlorogenic Acid

An electrochemical method was developed for the sensitive determination of chlorogenic acid using a boron doped diamond electrode (BDDE) modified with nano‐carbon black (nano‐CB). The active surface areas were found to be 0.059 and 0.146 cm² for the unmodified BDDE, and nano‐CB/BDDE, respectively. Compared with a BDDE, the nano‐CB/BDDE exhibited a well‐defined redox couple for chlorogenic acid. In addition, the plot of the peak current response changing from a square root to a linear dependence on scan rate is attributed to the transition from planar diffusion to surface behaviour. The anodic and cathodic peak separations (ΔE_p) were 97 mV and 14 mV at BDDE and nano‐CB/BDDE, respectively. The decrease in ΔE_p at the proposed electrode indicated that the process of chlorogenic acid was greatly accelerated. Square wave voltammetry (SWV) exhibited a dynamic range in which the current versus the concentration of chlorogenic acid were linear from 2.0×10^?8 to 2.0×10^?6 M with a LOD of 4.1×10^?9 M (based on 3S_b/m). The nano‐CB modified BDDE provided improved electrochemical behavior, high electrocatalytic activity, high sensitivity and good reproducibility.     

Autooxidative Activity of Chlorogenic Acid and Damage to DNA

The interaction of chlorogenic acid with double‐stranded calf thymus DNA was investigated in solution by cyclic voltammetry at a glassy carbon electrode (GCE). The different working electrodes were prepared by covering solution containing different components onto the surface of GCE. The autooxidative activity of chlorogenic acid and inducement of DNA damage were evaluated by employing the prepared working electrode in pH 5.0, 0.10 M acetate buffer solution with differential pulse voltammetry (DPV). The influences of temperature and metal ions (cupric ions) on the extent of DNA damage were examined. Chlorogenic acid possessed autooxidative activity and could induce DNA damage under certain conditions. The increasing temperature and existing cupric ions could enhance the autooxidative capability of chlorogenic acid and enlarge the extent of DNA damage. It was possible that the DNA damage induced by chlorogenic acid preferentially took place at guanosine‐containing segments, with the formation of 8‐oxo‐deoxyguanosine (a biomarker of DNA oxidative damage). A mechanism on the autooxidative activity of chlorogenic acid and inducing DNA damage was proposed.     

绿原酸的直接荧光分析法及其抗氧化性研究

绿原酸水溶液能产生微弱荧光,当加入95%的乙醇后,其荧光强度大大增强,基于此,建立了直接测定绿原酸的荧光分析新方法.pH=1.72时,在1.416～14.16μg/mL浓度范围内,绿原酸的荧光强度与其浓度呈良好的线性关系,相关系数r为0.9963;检出限为0.081 μg/mL;相对标准偏差为0.54%.该方法灵敏度高...     

HPLC-MS/MS多反应监测法测定藜蒿中绿原酸的含量

藜蒿(Artem isia SelengensisTurcz)是菊科蒿属草本植物,主要生长在江西鄱阳湖区域的草滩上,在我国其它地区也有分布。该植物不仅可食用,风味独特,是长江中下游地区的地方特色蔬菜,而且可作药用,具有抑菌、消炎、抗氧化等功效,是一种具有重要开发价值的植物资源[1]。近年来许多     

Development of a microchip‐pulsed electrochemical method for rapid determination of L‐DOPA and tyrosine in Mucuna pruriens

L ‐3,4‐dihydroxyphenylalanine (L‐DOPA) is a well‐recognized therapeutic compound to Parkinson's disease. Tyrosine is a precursor for the biosynthesis of L‐DOPA, both of which are widely found in traditional medicinal material, Mucuna pruriens. In this paper, we described a validated novel analytical method based on microchip capillary electrophoresis with pulsed electrochemical detection for the simultaneous measurement of L‐DOPA and tyrosine in M. pruriens. This protocol adopted end‐channel amperometric detection using platinum disk electrode on a homemade glass/polydimethylsiloxane electrophoresis microchip. The background buffer consisted of 10 mM borate (pH 9.5) and 0.02 mM cetyltrimethylammonium bromide, which can produce an effective resolution for the two analytes. In the optimal condition, sufficient electrophoretic separation and sensitive detection for the target analytes can be realized within 60 s. Both tyrosine and L‐DOPA yielded linear response in the concentration range of 5.0–400 μM (R² > 0.99), and the LOD were 0.79 and 1.1 μM, respectively. The accuracy and precision of the established method were favorable. The present method shows several merits such as facile apparatus, high speed, low cost and minimal pollution, and provides a means for the pharmacologically active ingredients assay in M. pruriens.     

Simultaneous Determination of Peroxide Hydrogen and Ascorbic Acid by Capillary Electrophoresis with Platinum Nanoparticles Modified Micro‐disk Electrode

In this study, the first application of a capillary zone electrophoresis‐electrochemical detection (CE‐ECD) method for concurrent determination of hydrogen peroxide (H₂O₂) and ascorbic acid (AA), was developed using the Pt nanoparticles (PtNPs) modified Pt micro‐disk electrode (PtME). The electrocatalytic activity of the modified electrode for H₂O₂ and AA was characterized by cyclic voltammetry. Under optimized experimental conditions, highly linear calibration plots were observed for both H₂O₂ and AA, with concentration linear ranges of 0.8 μM to 0.8 mM and 1.0 μM to 0.8 mM. Detection limits of 0.2 μM H₂O₂ and 0.5 μM AA were determined on the basis of the signal‐to‐noise characteristics (S/N=3) of an electropherogram. Compared with the unmodified PtME, the sensitivity was promoted in that PtNPs/PtME provided an increased effective electrode surface and high catalytic activity toward H₂O₂ and AA. Using this method, the added H₂O₂ and AA in Mizone, a kind of functional drink, were detected, and the concentration of AA was found to be 2.33 mM (n =3). The recovery rates were 95.3 % for H₂O₂ and 98.7 % for AA. The novel approach provided a wide linear range, low detection limit, good reproducibility and stability. It will provide a new insight into the balance of reactive oxygen species and antioxidant in biological systems.     

A Polarographic Study of Chlorogenic Acid and Its Interaction with Some Heavy Metal Ions

The behavior of chlorogenic acid (CGA) and its interaction with Hg(II), Pb(II), Cu(II), Cd(II) and Zn(II) has been studied using direct current (DC) and differential‐pulse polarography (DPP). Adsorptive and kinetic/catalytic anodic waves of CGA have been detected at ?0.02 and ?0.18 V vs. SCE, respectively; Hg(I)‐CGA surface disproportionation has been assumed. Reduction of Hg(II)‐ions, added in the buffered solution of CGA (pH 7.5), occurs rather than complexation, while the complex forming ability of CGA towards Pb(II) and Cu(II) has been observed. Stoichiometry 1 : 1 for Pb(II)‐CGA, and 1 : 1 and 1 : 2 for Cu(II)‐CGA has been established applying Job’s method of continuous variation on DPP data. UV‐vis spectrophotometric measurements additionally confirmed the existence and stoichiometry of Cu(II) complexes.     

用毛细管区带电泳技术测定杜仲叶中氯原酸含量的研究

用毛细管区带电泳技术测定杜仲叶中氯原酸含量，方法的相对迁移率为１．４０，回收率在９９．７４％～１０２．０％之间，５次测定的变异系数为０．４５％，满足分析要求，为杜仲叶提取液中氯原酸的测定提供了样品用量少、分析时间短、运行成本低的最新分析方法。     

Voltammetric Determination of Boric Acid Using the Ternary Complexation System with Salicylaldehyde and H‐Acid

A square‐wave voltammetric method for the determination of boric acid in water has been described based on the new understanding of the electrochemical behavior of boric acid‐Azomethine H complexation. Salicylaldehyde and H‐acid were used as the starting materials of boric acid‐Azomethine H complex and their concentrations were optimized for boric acid determination in water. A glassy carbon electrode, instead of a conventional mercury electrode, was used in the measurement. The detection limit of the proposed method was 0.10 mg B dm^?3. The proposed method was successfully used for boric acid determination in the water from a seawater desalination RO plant.     

超声提取-高效液相色谱法测定新疆昆仑雪菊中绿原酸的含量

以新疆昆仑雪菊为研究对象,以绿原酸为考察指标,以甲醇浓度、超声功率、超声时间和料液比为考察单因素,应用L9(34)正交试验优化超声提取工艺,并用高效液相色谱法(HPLC)测定雪菊中绿原酸的含量。最佳提取工艺条件是:80%甲醇溶液,超声时间为60min,超声功率为300 W,料液比为1∶25,在此条件下绿原酸的提取量为9.9810mg/g。采用Agilent TC-C18色谱柱(150×4.6 mm,5μm),流动相为甲醇-0.5%冰乙酸溶液(40∶60,V/V),流速为1.0mL/min,检测波长326nm。结果表明,绿原酸在0.01728~0.1210μg线性关系良好,平均加标回收率为108.16%,相对标准偏差(RSD)为1.10%(n=5)。