Direct Electroanalytical Determination of Fluvastatin in a Pharmaceutical Dosage Form: Batch and Flow Analysis

Abstract

The reduction of luvastatin (FLV) at a hanging mercury-drop electrode (HMDE) was studied by square-wave adsorptive-stripping voltammetry (SWAdSV). FLV can be accumulated and reduced at the electrode, with a maximum peak current intensity at a potential of approximately ?1.26 V vs. AgCl/Ag, in an aqueous electrolyte solution of pH 5.25. The method shows linearity between peak current intensity and FLV concentration between 1.0 × 10^?8 and 2.7 × 10^?6 mol L^?1. Limits of detection (LOD) and quantification (LOQ) were found to be 9.9 × 10^?9 mol L^?1 and 3.3 × 10^?8 mol L^?1, respectively.

Furthermore, FLV oxidation at a glassy carbon electrode surface was used for its hydrodynamic monitoring by amperometric detection in a flow-injection system. The amperometric signal was linear with FLV concentration over the range 1.0 × 10^?6 to 1.0 × 10^?5 mol L^?1, with an LOD of 2.4 × 10^?7 mol L^?1 and an LOQ of 8.0 × 10^?7 mol L^?1. A sample rate of 50 injections per hour was achieved.

Both methods were validated and showed to be precise and accurate, being satisfactorily applied to the determination of FLV in a commercial pharmaceutical.     

Electrochemical Determination of Citalopram by Adsorptive Stripping Voltammetry–Determination in Pharmaceutical Products

Abstract

The electrochemical behavior of citalopram was studied by square‐wave and square‐wave adsorptive‐stripping voltammetry (SWAdSV). Citalopram can be reduced and accumulated at a mercury drop electrode, with a maximum peak current intensity being obtained at a potential of approximately ?1.25 V vs. AgCl/Ag, in an aqueous electrolyte solution of pH 12. A SWAdSV method has been developed for the determination of citalopram in pharmaceutical preparations. The method shows a linear range between 1.0×10^?7 and 2.0×10^?6 mol L^?1 with a limit of detection of 5×10^?8 mol L^?1 for an accumulation time of 30 s. The precision of the method was evaluated by assessing the repeatability and intermediate precision, achieving good relative standard deviations in all cases (≤2.3%). The proposed method was applied to the determination of citalopram in five pharmaceutical products and the results obtained are in good agreement with the labeled values.     

Methylene Blue Poly(Vinyl Chloride) Membrane Electrode Based on the Methylene Blue-Teteraphenylborate Ion-Pair Complex and Its Application to Pharmaceutical Analysis

Abstract

A methylene blue (MB) poly (vinyl chloride) membrane electrode based on MBtetraphenylborate (TPB) ion-pair complex is described. The linear response covers the range 1x10^?2 - 1x10^?6 mol dm^?3 MB solution, with a slope of 56.5±0.5 mv/decade (pH range 3.0-1 0.0). The detection limit is 7.75x 10^?7 mol dm^?3. The electrode shows stability, good reproducibility and fast response. Interferences from common inorganic cations and some organic bases are negligible. These characteristics of the electrode enabled it to be used successfully for the determination of MB in injection.     

微流控分析系统中的自动控制和数据分析

介绍了自动控制及数据分析方法在微流控分析系统中的应用技巧及可行方案.以芯片电泳系统为例,具体介绍电子技术应用于微流控检测仪器搭建及检测数据处理,同时,拓展说明了未来信息技术在微流控分析系统中可能的应用领域.     

A Simple Minimized System Based on Moving Drops for Antioxidant Analysis Using a Smartphone

In this paper, a novel antioxidant analysis is proposed using a simple minimized device based on moving drops as solution handling and a smartphone as a detector. This approach is based on the colorimetric determination of the scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•), expressed as the half-maximal inhibitory concentration (IC₅₀), vitamin C equivalent antioxidant capacity (VCEAC), and Trolox equivalent antioxidant capacity (TEAC). A small drop of the positive control or the samples moves by eluting an ethanol drop down by the force of gravity to react with a DPPH^• drop in the detection zone. The color change of DPPH^• is monitored by a smartphone camera, and the color signals are processed using Adobe Photoshop software. The magenta-to-yellow ratio was successfully applied to evaluate the percentage of DPPH^• inhibition with no significant difference compared with the reference spectrophotometric method at a confidence level of 95%. The total phenolic content (TPC) was measured using the Folin–Ciocalteu assay. An application to Miang (fermented tea leaf extract) showed the consonant relationship between the scavenging activity of DPPH^• and TPC.     

基于遗传进化的聚类分析新方法

提出了一种基于遗传进化策略的聚类分析新方法，将聚类问题转换为实数空间的优化问题．用遗传策略在连续的实数空间寻找最优类中心，既可避免求解组合优化问题，减少计算量，又可避免在优化过程中陷入局部最优．此遗传聚类方法用于对4组实际数据进行硬分类和模糊分类，结果令人满意．     

Degeneration of Limit Cycle Oscillation in BZ Electrode Reaction System Controlled Externally

A dynamical model of electrode BZ reaction system was establisheed on the basis of three variables Oregonator model and kinetics of electrode process. Under weak periodical constraint approximation, dynamical stability of quasi steady state on the slow manifold of the system is analyzed by means of linearized stability analysis of three variable system. Meanwhile, the corresponding regime favorable for the appearance of limit cycle oscillation is calculated. Computer simulation shows that limit cycle oscillatory regime has degenerated because of the external periodical potential constraint in the electrode phase. In this regime the system behaves as a temporary self-organization. Whereas, outside this regime a kind of response oscillation appear, with same period as the constraint.     

Stripping Chronopotentiometry and Stripping Voltammetry of Mixtures of Heavy Metal Ions Producing Close Signals: The Cd(II)‐Pb(II)‐Phthalate System

The effects of the proximity of the signals of two heavy metal ions in stripping voltammetry (SV) and constant‐current stripping chronopotentiometry (SCP) is studied at mercury drop (HMDE) and mercury film (MFE) electrodes. For this purpose, the Cd(II)‐Pb(II)‐phthalate system is used, taking advantage of the approaching of the signals corresponding to Cd(II)‐phthalate and Pb(II)‐phthalate labile complexes as phthalate is added to mixtures of Cd(II) and Pb(II)‐ions. The results are compared with those obtained by differential pulse polarography (DPP) and by stripping measurements on the Pb(II)‐phthalate system alone, showing discrepancies in SCP data under nondepletive conditions and negligible differences in the other cases.     

基于离散流的微全分析系统

针对基于连续流的微全分析系统的弊端,详细研究了几种基于离散流的微分分析系统的原理及结构。     

铂电极BZ反应体系的系统动力学分析

在一定的条件下,将铂电极BZ化学反应的六变量高维动力学系约化为三变量体系,同时对该体系进行了全面的系统动力学分析.研究结果表明,通过改变耦合体系的外控参数条件,在将体相保持在均一稳定定态的参数范围内,电极反应相可能进入振荡区,而呈现出电极反应相与体相的动力学行为不一致性.进一步计算出体相处于非振荡状态时,电极反应相产生电化学振荡的外控参数区域.     

A New and Sharp Ternary Indicator System for Argentometric Titration of Microamounts of Iodide

 A ternary indicator system, Cadion 1B-silver ion-emulsifier octylphenyl polyglycol ether, for visual and direct titration of iodide ion with silver nitrate (as the titrant) is described. The advantages of the method are as follows: (1) when the titration reaches the equivalence point, the color of the resulting solution sharply changes from pure yellow to orange and the solution remains transparent rather than turbid; (2) the method is sensitive (the detection limit is 2 × 10⁻⁴ mol/L iodide) and accurate (the recoveries of standard addition are 99.60%–100.8%); (3) the results of titrating iodide by the method agree with those obtained by eosin B as an indicator for iodide; (4) the endpoint is much sharper than that obtained by eosin B as indicator for iodide ion; (5) the method has been successfully applied to determination of iodide in the tincture of iodine and tetrapropyl ammonium iodide samples with satisfactory results; (6) a vast amount of iodate, sulphate and fluoride ions does not interfere; (7) the method also may be automated if necessary. Received November 23, 1998. Revision November 6, 2000.     

A Batch Injection Analysis System with Square-wave Voltammetric Detection for Fast and Simultaneous Determination of Zinc and Ascorbic Acid

The determination of organic and inorganic compounds in a single run is still a great challenge. In this paper, we developed a method for fast simultaneous determination of ascorbic acid (AA) and zinc ions (Zn) using batch injection analysis with detection by square-wave anodic stripping voltammetry (BIA-SWASV). Britton-Robinson (BR) buffer solution (pH=6.0) as the supporting electrolyte and boron doped diamond (BDD) as the working electrode. The method presented favorable analytical characteristics such as fast response (67 injections h⁻¹), low detection limits (0.2 and 5.4 μmol L⁻¹ for Zn ions and AA, respectively) and recovery values of 99±3%.     

新型微填充柱－毛细管柱色谱操作条件的优化及灰色关联分析

通过正文设计实验方法优化了新型微填充柱。毛细管柱色谱操作条件，并利用灰色关联分析方法考察了操作条件与柱效的相关程度，对实验能起一定的指导作用。