Masking Ability of Various Complexing Agents for Aluminum in the Fluorine Determination with a Fluoride Ion-Selective Electrode

Abstract

In the determination of fluoride ion with a fluoride ion-selective electrode, tiron is the most effective of masking agents tested for aluminum. The higher the pH, the more effective the masking, but the hydroxide ion raises the lower limit of determinable fluoride ion concentration at higher pH.

Therefore, measurements at pH 6.0 are preferable. Fluorine in two glass samples has been successfully determined with tiron.     

自动化流动注射停流动力学分析仪的研制及其性能测试

本文研制了一套自动化流动注射停流动力学分析仪，该仪器由苹果Ⅱ型微机通过１２位ＡＤ／ＤＡ卡，流动注射停流控制仪及用ＢＡＳＩＣ语言编制的软件控制泵的起动和停止，试样的输送和混合，数据采集和处理，结果显示和打印，通过以铁（Ⅲ）与硫氰酸盐的反应体系采用固定时间法和以钒（Ｖ）的胶束催化反庆体系采用安始速法的现场测试证明，该仪器具有结构简单，操作方便，恒温性能好，通用性强等特点。     

用氟离子电极对土壤中铝作直接电位法测定

本文提出用氟离子电极对土壤中铝作直接电位法测定。大大减少了以往的用终点电位滴定法测定土壤中铝含量的实验步骤与时间,并较大地提高了测定的准确度。方法是取一定量的土壤试液加入到pH为5,离子强度为1.0的缓冲溶液中,再加入一定量的F~-离子标液,让F~-与Al_(3 )络合稳定后,用氟离子电极测出溶液中的游离态F~-浓度,从而计算出Al~(3 )的总浓度。     

Fluoride Determination in Water: An Optimum Buffer System for Use with the Flouride-Selective Electrode

Abstract

The departure from linear response which often occurs at dilute fluoride concentrations of the calibration curve reduces the sensitivity of the electrode. The linear portion of the standard curve may be extended to lower fluoride levels by dilution of the buffer itself. TISAB III M. tri-Ammonium citrate (TAC) is the superior of the eleven buffer systems examined in terms of masking ability. Of the potentially interfering species studied, only Al and Mg pose interference problems.     

Flow-Injection Determination of Glucose by a Photoinduced Chemiluminescent Reaction

Abstract

A flow-injection procedure for the photochemical determination of glucose has been developed. The method is based on the photo-oxidation of glucose sensitized by 9,10-anthraquinone-2.6-disulfonate (disodium salt). The hydrogen peroxide formed in the photochemical reaction was measured by means of the chemiluminescent reaction with luminol and hematin. A linear calibration graph was obtained over the range 2.0x10^?6-8.5 x 10^?5 mol L^?1. The method was applied to determining glucose in blood serum, urine and fruit juices.     

Flow-Injection Differential Spectrophotometric pH Selectivity System for the Determination of Cyclamate Contaminants

A flow-injection system with differential spectrophotometric detection is proposed for the simultaneous determination of aniline and cyclohexylamine based on their reaction with 1,2-naphthoquinone-4-sulfonate (NQS). The pH is chosen to achieve selectivity since only aniline reacts at acidic pH whereas the two amines are derivatized in basic medium. The flow manifold comprises two reactors and two detection cells for developing and monitoring the reaction under selective and general (non-selective) conditions. A double beam spectrophotometer is used for differential detection, with two flow cells placed in the sample and reference holders. Figures of merit such as sensitivity, linear range, detection limit and precision are established. The evaluation of accuracy using a series of synthetic mixtures indicates overall prediction errors of 3% and 5% for aniline and cyclohexylamine, respectively. The method is applied to the determination of amine impurities in commercial sweeteners. Good concordance between the proposed and the standard chromatographic methods is found.     

沉积物中铝含量的流动注射分光光度法测定

本文根据自行设计的一套流动注射（ＦＩＡ）双光束分光光度计装置，研究了河底沉积物中微量铝测定的适宜条件，设备简单，操作容易。灵敏度较普通光度法提高近１倍，进样速率为８０－９０次／ｈ，相对标准偏差小于０．９％。     

Determination of Total Fluoride in Oral Products by Using of Potentiometry With Ion Selective Electrode: A Critical Study

ABSTRACT

In this work, a critical study of the determination of fluoride in oral products with an ion selective electrode was performed. The influence of the type of fluorine compound in the sample as well as the practical factors involved in the analysis were investigated. Fluoride could be determined, directly, in samples where it is in the form of NaF or SnF₂. However, in samples where it is as MFP (sodium monofluorophosphate) an acid treatment was needed for removal of fluoride from the PO₄F^2? ion. In both cases, problems were noted related to the continuous use of the electrode, caused by the adsorption of fluoride ions onto the electrode surface. This problem was solved by using of KOH and Al₂(SO₄)₃ solutions. Good results were obtained for the analysis of real commercial samples.     

Masking Agents in Metal Titration with Edta Part IV - Thorium Titration in the Presence of Some Metals

Abstract

The authors studied the possible employment of various compounds containing sulfur as masking agents for divalent and trivalent metals, in the titration of thorium with EDTA. Reagents studied were thioglicolic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, 2,3-dimercaptopropanol, BIS (2-hydroxy ethyl) dithlocarbamate, ethylxantate, thionalid, thiourea and thiosulfate.

The ones which proved more efficient were 2,3-dimercaptopropanol and BIS (2-hydroxyethyl) dithiocarbamate.     

Determination of L-Ascorbic Acid by Adsorption Potentiometry with Carbon Paste Electrode

Abstract

This paper reports the potentiometric measurement of ascorbic acid in the solution of 0.10 mol/L NaOH-0.1 mol/L NaCl using carbon paste (the mixture of spectroscopic graphite powder and di-iso-octyl phthalate) electrode(room temperature 15°C), with the linear range 7.0 × 10^?7 × 4.0 × 10^?5mol/L, average response slope 95mV/decade and detection limit 1 × 10^?7mol/L. Phenol, sulfite, Mn²⁺ and so on pose no interference to the measurement of ascorbic acid. This method is characterized by fine selectivity, reproducibility and accuracy. The potential response behavior is caused chiefly by chemisorption of ascorbic acid to the surface of the carbon.

Each year yields a number of papers concerning the determination of ascorbic acid by various methods, including gas chromatographymass spectrometry¹, capillary electrophoresis², spectrophotometry³, voltammetry⁴, titrimetric method⁵, biosensor⁶ and so on, Each method has its merits and defects in analyzing different samples. M. Petersson⁷ worked out the potentiometric sensor for determining ascorbic acid by modifying monolayer of ferrocene upon the surface of half-oxidized platinum electrode with an average response slope 50±8.8mV/decade, but this sensor suffers from inadequate selectivity. In our study, carbon paste electrode (without ionophore) is applied in the determination of ascorbic acid by potentiometry with an average response slope 95mV/decade. This method displays fine selectivity, accuracy, convenience and rapidity of determination.     

Flow-Injection Analysis Based on Extraction and Spectrophotometric Determination of Penicillins with Thiazine Dyes

Abstract

A new method for flow-injection analysis (FIA) for the determination of penicillins based on the extraction and spectrophotometric determination of ion associates with selected thiazine dyes (methylene blue, azure A, and azure B) is proposed. The reaction conditions (c_dye = 2 × 10^?4 mol l^?1, c_KCl = 1 mol l^?1, pH ? 6, λ = 635 nm) were found. The factorial design has been carried out to determine the optimum flow conditions. A wide linear dynamic range of calibration curves (5.1–700 µg ml^?1 for penicillin V with all dyes, R = 0.9985) and good repeatability (e.g., relative standard deviation [RSD] = 4.6–0.6% in this concentration range for the reaction with azure B) were found. The detection limit for penicillin V is 1.5 µg ml^?1, and the determination limit is 5.1 µg ml^?1. The maximum analysis rate is 35 samples per h. The practical samples of pharmaceutics were tested. There are no interferences from the additives in pharmaceutics.     

Flow-Injection Spectrophotometric Determination of Diclofenac or Mefenamic Acid in Pharmaceuticals

 Two flow injection (FI) spectrophotometric methods are proposed for the determination of diclofenac (DCF) or mefenamic acid (MF) in bulk samples and pharmaceuticals. Both methods are based on the reaction of DCF or MF with potassium ferricyanide in a sodium hydroxide medium. The absorbance of the orange products obtained is measured at 455 nm for DCF and 465 nm for MF. The corresponding calibration graphs are linear over the range 0.20–20.0 mg L⁻¹ for DCF and 1.00–100 mg L⁻¹ for MF, while the limits of detection were 0.05 and 0.18 mg L⁻¹, respectively. Received March 27, 2000. Revision November 15, 2000.     

Rapid Determination of Fluoride in Potable Waters by Potentiometric Flow Injection Analysis

Abstract

A potentiometric flow injection analysis system is described, enabling tap water and other fluoride-bearing matrices of low interferent level to be determined at the rate of 360 samples per hour using an electrode polished with slurried alumina. Important parameters, such as carrier stream composition, sample volume and detector cell design are discussed with respect to this system, Fluoride electrodes regenerated with silver fluoride and silver epoxy are evaluated in flow injection mode, both before and after polishing.     

分光光度法测定豆类中铝含量

用分光光度法测定了豆类中的铝含量。利用Al^3＋在乙酸-乙酸钠缓冲介质中，与铬天青S（CAS）及十六烷基三甲基溴化铵（CTMAB）反应形成蓝色三元络合物，在610nm处测定其吸光度，并对CTMAB质量浓度进行了最佳选择。结果表明，该法提高了测定灵敏度。10种豆类中的铝含量中绿豆的铝含量最高，29．49μg／g；菜豆的铝含量最少，8．24μg／g；10种豆类的平均铝含量为15．33μg／g。可见豆类中的铝含量很低，建议放心多食豆类食品。     

Indirect Complexometric Determination of Aluminium using a Solid-Membrane Cupric Ion-Selective Electrode

Abstract

Indirect complexometric determination of 0.4–4 mg of A1 in 0.2 M solutions of NaNO₃, NH₄NO₃ and 0.01 M Mg(NO₃)₂ or 0,01 M Ca(NO₃)₂ was studied. The solid membrane cupric-ion selective electrode was used for end-point detection in back‐titration of DCTA (added in excess) with a cupric standard solution.     

Dioctadecyldimethylammonium Chloride Bilayer Membrane Vesicle-Enhanced and Manganese (II)-Catalyzed Chemiluminescence for Determination of Adrenaline by a Flow-Injection Method

Abstract

A new chemiluminescence system reinforced by use of a surfactant and a metal catalyst is demonstrated for selective determination of adrenaline by a flow-injection method. The weak light emission originating from an aerobic oxidation of adrenaline in an alkaline solution is dramatically enhanced by ordered surfactant molecular assemblies, dioctadecyldimethylammonium chloride bilayer membrane vesicles, with the largest enhancement factor of 1000 which has not ever been realized. The enhanced emission is further increased by a Mn(II) catalyst with an enhancement factor of ca. 40. The limit of determination(S/N=2) is 1×10^?8M (0.2 ng in 100-μ1 injection), the linear range is four ordrers of magnitude, the sample throughput is 100 h^?1. and the relative standard deviation(n=5) is 0.9 % for 5×10^?7M adrenaline. Of other substances including dopamine, noradrenaline, and related compounds, p-hydroxymandelenic acid chemiluminesces most strongly after adrenaline, the 1×10^?3M solution providing a signal 24% of that for 1×10^?6M adrenaline.     

干法灰化-铬天青S光度法测定血清铝含量

建立了一种快速、灵敏测定血清铝的分光光度方法。血清标本经灰化处理后 ,在表面活性剂CPC存在下 ,用铬天青S (CAS)作显色剂测定血清铝 ,线性范围 0～ 7 4μmol/L ,平均回收率为 1 0 0 6% ,批内变异系数 (CV)和批间变异系数分别为 0 0 2 8和 0 0 3 7,与Al-CAS络合法比较具有良好的相关性 ,y =0 .990 2x -0 0 1 3 0 ,r =0 .9977,P >0 0 5。 42例健康人血清铝含量为 0 92～ 4 1 6μmol/L ( x± 2s)。用本法测定血清铝方法简便、灵敏可靠 ,适合临床应用。     

Indirect Flow-Injection Analysis of Ascorbic Acid by Photochemical Reduction of Methylene Blue

Abstract

Ascorbic acid was determined indirectly by spectrophotometry at 666 nm based on the photochemical reduction of methylene blue using flow-injection analysis. The carrier stream was 12.7 μgml^?1 methylene blue in phthalate-HCl buffer solution at pH 3.2. The reactor was irradiated with a 500-Watt halogen lamp to facilitate the development of the photochemical reaction. The system allows determination of ascorbic acid in the range 0.18–6.12 μgml^?1 with relative standard deviations of 2.09 and 0.31% for 1.97 and 4.92 μgml^?1 samples, respectively, and a sampling frequency of 50–55 h^?1. The proposed method was applied successfully to the determination of ascorbic acid in vitamin C tablets.