Determination of codeine and its metabolite in human urine by CE with amperometric detection

The amperometric detection of codeine and its metabolite, morphine following capillary zone electrophoretic separation is described. A carbon-disk electrode used as working electrode for two analytes exhibited a good response at 0.90 V (vs. Ag/AgCl). The optimal conditions of separation and detection were pH 8.4 phosphate buffer solution (0.06 mol x l(-1)), 12 kV for the separation voltage, sample injection at 12 kV for 10 s. The linear ranges were from 3.1 x 10(-7) to 2.5 x 10(-5) mol x l(-1) for codeine and 1.9 x 10(-7) to 1.5 x 10(-5) x mol l(-1) for morphine with a correlation coefficient of 0.9996 and 0.9999, respectively. The detection limits for codeine and morphine were 1.6 x 10(-7) and 6.8 x 10(-8) x mol l(-1). The method developed was successfully applied to the determination of codeine and its metabolite, morphine in the human urine without any other sample pretreatment except filtration, and the results were satisfactory.     

Differential pulse adsorption voltammetry for determination of procaine hydrochloride at a pumice modified carbon paste electrode in pharmaceutical preparations and urine

Procaine hydrochloride was determined by the differential pulse voltammetry (DPV) using a 6% (m/m) pumice modified carbon paste electrode in 1.25 x 10(-3) mol x l(-1) KH(2)PO(4) and Na(2)HPO(4) buffer solution (pH 6.88, 25 degrees C). The anodic peak potential used was +0.980 V (vs. SCE). A good linear relationship was realized between the anodic peak current and procaine concentration in the range of 9.0 x 10(-7)-2.6 x 10(-5) mol x l(-1) with the detection limit of 5.0 x 10(-8) mol x l(-1). The recovery was 95.2-104.8% with the relative standard deviation of 3.2% (n=10). The pharmaceutical preparations, procaine hydrochloride injection and the urine samples were determined with the desirable results.     

Voltammetric determination of fenbendazole in veterinarian formulations

A versatile voltammetric method for quantitative determination of fenbendazole (FBZ) in commercial tablets has been proposed, where direct dissolution of tablets is carried out in 0.1 mol l(-1) tetrabutylamoniun tetrafluorborate containing dimethylformamide solutions. Linear sweep (LSV), square wave (SWV) and differential pulse (DPV) voltammetry techniques were applied to study FBZ at a glassy carbon electrode, exhibiting a well defined irreversible oxidation peak at 1.15 V vs. SCE. This methodology allows a precise quantitative determination of FBZ presenting detection limits of 5.2 x 10(-5) (LSV), 5.0 x 10(-6) (DPV) and 5.0 x 10(-5) mol l(-1) (SWV).     

Determination of hydrochlorothiazide and rutin in Chinese herb medicines and human urine by capillary zone electrophoresis with amperometric detection

In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was firstly applied to the simultaneous determination of rutin (RT) and hydrochlorothiazide (HCT) in compound Chinese herb medicines and human urine samples. The two analytes could be perfectly analyzed within 12 min and showed significant current responses at carbon electrode under the optimum conditions. It was found that the linear range of HCT was from 2.0 x 10(-6) to 1.0 x 10(-4) mol l(-1) and that of RT was from 1.0 x 10(-6) to 1.0 x 10(-4) mol l(-1). Their sensitivity was determined by linear regression and calculated as 7.02 x 10(4) and 2.17 x 10(5) nA l mol(-1), respectively, and their detection limits were 5.0 x 10(-7) and 2.0 x 10(-7) mol l(-1), respectively (S/N=3). Above results demonstrated that this method was of high sensitivity, good repeatability, high selectivity and could be used in metabolic kinetics studies of medicines. Satisfactory results were obtained when this method was used to simultaneously analyze the amounts of RT and HCT in one general compound Chinese herb medicine-Zhen Ju jiang Ya Pian and human urine samples.     

The effects of alpha-adrenoceptor antagonists on contractile responses to 5-hydroxytryptamine in dog saphenous vein.

1 5-Hydroxytryptamine (5-HT) contracted isolated saphenous vein strips of the dog, producing a biphasic concentration-effect curve. The first phase occurred with low concentrations of 5-HT (1.0 X 10(-8) TO 5.0 X 10(-6) mol/l) with a plateau between 1.0 x 10(-6) mol/l and 1.0 x 10(-5) mol/l. The second phase occurred with high concentrations of 5-HT (greater than 1.0 x 10(-5) mol/l). 2 The alpha-adrenoceptor antabonists, phentolamine (5.0 x 10(-8) to 5.0 x 10(-7) mol/l), labetalol (1.0 x 10(-6) to 1.0 x 10(-5) mol/l) and thymoxamine (1.0 x 10(-6) to 1.0 x 10(-5) mol/l), antagonized responses to high concentrations of 5-HT but responses to low concentrations of 5-HT were not antagonized. 3 The effects of high concentrations of 5-HT were antagonized by cocaine (1.0 x 10(-6) to 1.0 x 10(-5) mol/l) and were not evident in veins removed from dogs pretreated with syrosingopine. 5-HT receptors and that high concentrations of 5-HT also act indirectly on alpha-adrenoceptors by displacing noradrenaline from neuronal stores.     

Determination of the composition of Chinese ligustrum lucidum polysaccharide by capillary zone electrophoresis with amperometric detection

In this paper, capillary zone electrophoresis with amperometric detection was firstly applied to indirectly determine the composition of Chinese ligustrum lucidum polysaccharide (LLPS) by analyzing its hydrolyzates: fucose, glucose, arabinose and rhamnose. Under the selected optimum conditions, the four monosaccharides could be perfectly separated within 30 min and showed significant current responses at the copper electrode. The linear ranges of fucose, glucose and arabinose were all from 5.0 x 10(-6) to 1.0 x 10(-4) mol l(-1) and that of rhamnose was from 1.0 x 10(-5) to 1.0 x 10(-4) mol l(-1), and their detection limits were lower or near 1.0 x 10(-6) mol l(-1) (S/N=3). Experiments showed that the mole ratio of fucose, glucose, arabinose and rhamnose in Chinese LLPS was 1.80:4.58:2.55:1.91, and the purity of this polysaccharide leached by the introduced leaching method was 93.3%. Analyzing polysaccharide by this method has some merits of quickness, low-volume sampling, simple instrument, high sensitivity and high reproducibility.     

Study of the interaction of 6-mercaptopurine with protein by microdialysis coupled with LC and electrochemical detection based on functionalized multi-wall carbon nanotubes modified electrode

Microdialysis sampling coupled with liquid chromatography and electrochemical detection (LC-ECD) was developed and applied to study the interaction of 6-Mercaptopurine (6-MP) with bovine serum albumin (BSA). In the LC-ECD, the multi-wall carbon nanotubes fuctionalized with carboxylic groups modified electrode (MWNT-COOH CME) was used as the working electrode for the determination of 6-MP. The results indicated that this chemically modified electrode (CME) exhibited efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP were linear to its concentrations ranging from 4.0 x 10(-7) to 1.0 x 10(-4) mol l(-1) with the calculated detection limit (S/N = 3) of 2.0 x 10(-7) mol l(-1). The method had been successfully applied to assess the association constant (K) and the number of the binding sites (n) on a BSA molecular, which calculated by Scatchard equation, were 3.97 x 10(3) mol(-1) l and 1.51, respectively. This method provided a fast, sensible and simple technique for the study of drug-protein interactions.     

Interaction of methylparaben preservative with selected sugars and sugar alcohols

The interaction of methylparaben preservative with selected sugars (glucose, fructose, sucrose, lactose, maltose, cellobiose) and sugar alcohols (lactitol, maltitol) were demonstrated in this study. It was observed that the formation of transesterification reaction products between methylparaben and the selected sugars occurred only under mild reaction conditions (e.g., pH 7.4 at 50 degrees C ), which were confirmed by HPLC-UV studies and mass spectrometry. On the other hand, under alkaline conditions and high temperature, degradation of the sugars predominated. Because sugars could easily undergo many possible degradation reactions and isomerization including on-column anomerization, the chromatograms of the reaction products were more complicated than those obtained from sugar alcohols. Sucrose, a nonreducing sugar, was much more stable than other selected sugars. The chromatogram of the transesterification reaction products of methylparaben with sucrose clearly showed eight peaks, which were likely to correspond to the same number of hydroxyl groups of sucrose. To compare the rate of the transesterification reaction of methylparaben with sucrose to that with sorbitol, kinetic studies were carried out. Similar rate constants were observed: 5.4 x 10(-7) L mol(-1) s(-1) and 4.9 x 10(-7) L mol(-1) s(-1) for sucrose and sorbitol, respectively.     

Determination of active ingredients in Huangdan Yinchen Keli by CZE with amperometric detection

A simple, reliable and reproducible method, based on capillary zone electrophoresis with amperometric detection (CZE-AD), has been developed for simultaneous determination of five active ingredients in complicated traditional Chinese medicines including chlorogenic acid, caffeic acid, aloe-emodin, emodin and rhein. A carbon-disk electrode was used as working electrode. The optimal conditions of CZE detection were 30 mM borate solution (pH 9.5) as running buffer, 18 kV as separation voltage and 1.00 V (versus Ag/AgCl) as detection potential. There was excellent linearity between current response and analyte concentration over two orders of magnitude, while the limits of detection were 1.1 x 10(-7), 3.0 x 10(-7), 1.5 x 10(-7), 2.9 x 10(-7), 1.4 x 10(-6) mol/l for aloe-emodin, emodin, rhein, chlorogenic acid and caffeic acid, respectively (S/N = 3). The utility of this method was demonstrated by monitoring a kind of complicated Chinese medicine named Huangdan Yinchen Keli. Two samples manufactured by different companies were monitored with satisfactory results.     

Flow injection potentiometric determination of bismuth(III) in anti-acid formulations

A flow injection potentiometric procedure is proposed for determining bismuth(III) in anti-acid formulations. In this work, a tubular electrode coated with an ion-pair formed between [Bi(EDTA)](-) and tricaprylylmethylammonium cation (Aliquat 336) in a poly(vinylchloride) (PVC) was constructed and used in a single channel flow injection system. The effect of membrane composition, pH and flow injection parameter over the Bi(III) tubular electrode response (slope (mV/decade)) was initially evaluated in quintuplicate in 0.5 mol l(-1) EDTA solution as carrier. The best response (-59.6+/-0.9 mV/decade) was attained with the 5% m/m ion-pair; 65% m/m o-nitrophenyl octyl ether (o-NPOE) and 30% m/m PVC in pH 6-9. The electrode showed a linear response to E (mV) versus log [Bi(EDTA)](-) in the bismuth(III) concentration range from 2.0x10(-5) to 1.0x10(-2) mol l(-1) and a useful lifetime of at least 5 months (more than 1000 determinations for each polymeric membrane). The detection limit was 1.2x10(-5) mol l(-1) and the R.S.D. was less than 2.0% for a solution containing 5.0x10(-4) mol l(-1) bismuth(III) (n=10). Several species such as Cd(II), Mn(II), Ni(II), Zn(II), Co(II), Cu(II), Mg(II), Cr(III) and Al(III) at 1.0x10(-3) mol l(-1) concentration in 0.5 mol l(-1) EDTA solution did not cause any interference. The frequency rate was 90 determinations per hour and the results obtained for bismuth(III) in anti-acid formulations using this flow procedure and those obtained using a spectrophotometric procedure are in agreement at the 95% confidence level.     

阿霉素在纳米钴修饰电极上的电化学行为及其应用

采用NaBH₄还原法制备了钴纳米粒，将其固定于氧化铟锡(ITO)电极上，首次制成了纳米钴修饰电极(NpCo/ITO)，并研究了阿霉素(adriamycin，ADM)在NpCo/ITO上的电化学性质。用循环伏安法(CV)、扫描电子显微镜(SEM)和能量色散谱(EDS)等对纳米钴修饰电极表面进行了表征。在纳米钴修饰电极上，阿霉素(ADM)在0.01 mol·L^-1 KH₂PO₄-K₂HPO₄溶液(pH 8.0)中，出现还原峰，峰电位为-0.67 V(vs Ag/AgCl),峰电流与ADM浓度在1.0×10^-8～2.0×10^-6 mol·L^-1呈线性关系，检测限为5.0×10^-9 mol·L^-1。循环伏安法研究表明，该体系属于具有吸附性的不可逆过程，NpCo/ITO对ADM的电化学还原过程产生较大的促进作用。     

Determination of active components in rosemary by capillary electrophoresis with electrochemical detection

Rosemary (Rosmarinus officinalis L.) is a spice and medicinal herb widely used around the world. Among natural antioxidants, rosemary has been widely accepted as one of the spices with the highest antioxidant activity. A capillary electrophoresis method for the determination of its active components using electrochemical detection was developed. Effects of several important factors were investigated to acquire the optimum conditions. The detection electrode was a 300 microm carbon disc electrode at a working potential of +0.90 V (versus SCE). The analytes can be well separated with 25 min in a 75 cm length fused-silica capillary at a separation voltage of 16 kV in an 80 mmol/l borate buffer (pH 9.0). The current response was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 2 x 10(-7) to 1 x 10(-6)g/ml for all the analytes. The method was successfully used in the analysis of rosemary with relatively simple extraction procedures, and the assay results were satisfactory.     

Determination of baclofen enantiomers in pharmaceutical formulations using maltodextrin-based enantioselective, potentiometric membrane electrodes

Two enantioselective, potentiometric membrane electrodes (EPMEs) based on maltodextrins with different value of dextrose equivalent (DE) (maltodextrin I: DE 4.0-7.0; maltodextrin II: DE 16.5-19.5) were proposed for the assay of baclofen enantiomers in baclofen raw materials and from its pharmaceutical formulation, Norton-Baclofen tablets. The slopes of the electrode function of the proposed electrodes were 55.0 mV/pS-baclofen for maltodextrin I-based electrode and 59.0 mV/pR-baclofen for maltodextrin II-based electrode and the detection limits were 1.34 x 10(-6) mol l(-1) (S-baclofen) and 2.52 x 10(-10) mol l(-1) (R-baclofen), respectively. The surfaces of the electrodes are stable and easily renewable by simply polishing on alumina paper.     

Sensitive determination of ketoprofen using flow injection with chemiluminescence detection

A rapid chemiluminescence method is described for the determination of ketoprofen by combining the flow injection technique and its sensitizing effect on the weak chemiluminescence reaction between sulfite and acidic permanganate. The optimum conditions for the chemiluminescence emission were intensity. A mechanism for the chemiluminescence reaction has been proposed on the basis of chemiluminescent spectra. Ketoprofen can be determined over the concentration range of 5.0x10(-8) to 3.0x10(-6) mol/L with a correlation coefficient of 0.9999 and a detection limit of 2.0x10(-8) mol/L (3sigma). The relative standard deviation (R.S.D.) for 15 repetitive determinations of 1.0x10(-6) mol/L ketoprofen is 0.8%. The utility of this method was demonstrated by determining ketoprofen in capsules and human urine sample.     

Study of electrochemical oxidation and determination of albendazole using a glassy carbon-rotating disk electrode

In this work, electrochemical oxidation of albendazole (ABZ) was carried out using a glassy carbon-rotating disk electrode. Development of electroanalytical methodology for ABZ quantification in pharmaceutical formulations was also proposed by using linear sweep voltammetric technique. Electrochemical oxidation is observed for ABZ at E(1/2)=0.99 V vs. Ag/AgCl(sat), when an anodic wave is observed. Kinetic parameters obtained for ABZ oxidation exhibited a standard heterogeneous rate constant for the electrodic process equal to (1.51+/-0.07) x 10(-5) cm s(-1), with a alphan(a) value equal to 0.76. Limiting current dependence against ABZ concentration exhibited linearity on 5.0 x 10(-5) to 1.0 x 10(-2) mol l(-1) range, being obtained a detection limit of 2.4 x 10(-5) mol l(-1). Proposed methodology was applied to ABZ quantification in pharmaceutical formulations.     

The study on a PVC membrane electrode for gemfibrozil

In this paper, a poly(vinyl chloride) (PVC) membrane electrode is prepared for gemfibrozil, 2, 2-dimethyl-5-(2,5-xylyloxy) valeric acid, based on its ion pair complexes with hexadecyltrioctyl ammonium iodide (HTOA). The membrane composition of the electrode was optimized by using the sequential level elimination method for orthogonal experimental design. The electrode has a Nernstian response range from 2.5 x 10(-5) to 0.1 mol/l with an average slope of 55.3 mV/decade. The limit of detection is 7.1 x 10(-6) mol/l. The electrode responses were not affected by pH in the range 10.0-12.3. A Na2B4O7-Na2CO3 buffer of pH = 11.0 was selected as the background electrolyte solution for potentiometric measurements. The electrode was used for determining gemfibrozil in pharmaceutical preparations with satisfactory results.     

氧氟沙星在Pt/GC离子注入修饰电极上的电化学行为及其应用

目的　研究氧氟沙星在Pt/GC离子注入修饰电极上的电化学行为。方法　氧氟沙星在0.40mol·L^-1KCl溶液中,用Pt/GC离子注入修饰电极进行伏安测定。结果　得到一良好的还原峰,峰电位Ep=-1.35V(vsSCE)。峰电流与氧氟沙星的浓度在1.0×10^-6-3.0×10^-5mol·L^-1呈线性关系,相关系数γ=0.9992;检出限为5.0×10^-7mol·L^-1。该法用于药片的测定,获得满意结果。用线性扫描和循环伏安法等电化学手段研究体系的电化学行为和电极反应机理。用俄歇电子能谱(AES)、光电子能谱(XPS)和扫描电子显微镜(SEM)等表面分析技术检测了注入电极表面的元素的组成、价态和深度分布,对离子注入电极的催化性质进行了探讨。结论　实验表明,体系属于两电子还原的不可逆过程。     

谷胱甘肽在10-甲基吩噻嗪修饰碳糊电极上的电催化氧化及电分析方法

研究了谷胱甘肽(还原型, glutathione, GSH)在10-甲基吩噻嗪(10-methylphenothiazine, MPT)修饰碳糊电极(MPT/CPE)上的电催化氧化行为。GSH在裸碳糊电极(carbon paste electrode， CPE)上的直接电化学氧化过程十分迟缓， 但在MPT/CPE上于0.702 V处出现一个不可逆氧化峰， 氧化电流大幅度增大。计时电流(chronoamperometry， CA)实验测得该电催化氧化反应速率常数k为(5.44±0.03)×10² (mol·L^-1)^-1·s^-1。用线性扫描伏安法(linear sweep voltammetry, LSV)测得催化氧化峰电流与GSH在5.0×10^-6～2.0×10^-3 mol·L^-1呈良好的线性关系， 线性回归方程I_pa=3.536c+2.117， r=0.999 0， 检测限为1.0×10^-6 mol·L^-1。同时用本方法对含GSH的市售药品进行了含量测定， 结果可靠。     

PVC membrane ion-selective electrodes for the determination of Hyoscyamine in pure solution and in pharmaceutical preparations under batch and flow modes

New PVC membrane electrodes selective for the determination of hyoscyamine ion (Hy(+)) based on hyoscyamine tetraphenylborate (Hy-TPB) or hyoscyamine phosphotungstate (Hy-PT) ion-exchangers as electroactive materials are described. The electrodes show a linear response for Hy(+) over the concentration range of 1.00 x 10(-5) to 1.26 x 10(-2) mol L(-1) and 1.00 x 10(-4) to 1.00 x 10(-2) mol L(-1) in case of Hy-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 1.00 x 10(-5) to 4.52 x 10(-3) mol L(-1) and 6.31 x 10(-5) to 1.00 x 10(-2) mol L(-1) in case of Hy-PT electrode for batch and FIA, respectively. The lower detection limits are 3.90 x 10(-6) and 4.51 x 10(-6) at 25 degrees C for Hy-TPB and Hy-PT electrodes, respectively. The electrodes posses near Nernstian slopes of 56.5 and 57.8 mV/decade for Hy-TPB and Hy-PT electrodes, respectively, and a fast potential response of < or =20 s which is almost constant over a pH range of 3-10. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components, other than hyoscyamine, of the mixed drugs investigated show negligible interference. The electrodes have been applied to the potentiometric determination of hyoscyamine in pure solution and in pharmaceutical preparations under batch and FIA conditions and as end point indicator electrode for the determination of hyoscyanine using potentiometric titration. For the concentrations (1.08 x 10(-5) mol L(-1) to 3.16 x 10(-3) mol L(-1)) an average recovery of 99.95% with relative standard deviation of 0.63% has been achieved. The effect of temperature on the electrodes was also studied.     

毛细管电泳/柱端安培检测血清中谷氨酰胺

目的建立毛细管区带电泳/柱端安培检测血清中谷氨酰胺的方法。方法通过研究谷氨酰胺柱前衍生化反应条件以及缓冲液pH值、缓冲液浓度、分离电压和检测电势对分离检测谷氨酰胺衍生产物的影响,确定了最佳实验条件。结果毛细管电泳/柱端安培检测谷氨酰胺的最佳条件是:衍生反应时间为30min,缓冲液为2.00×10-2mol/LNa2B4O7-8.57×10-3mol/L NaOH(pH=9.7),分离电压为20kV,检测电势为1.10V。谷氨酰胺的检测限为1.0×10-6mol/L即1.08fmol(S/N=3),线性范围为1.0×10-6mol/L～1.0×10-4mol/L,迁移时间及峰电流的相对标准偏差分别为2.2%、3.1%。结论所建立的毛细管电泳/柱端安培检测法灵敏、快速、准确,适用于血清样品中谷氨酰胺的测定。