Multicomponent analysis with a computerized flow injection system using LED photometric detection

An original computer-controlled solid-state photometer has been developed and its potential for simultaneous multicomponent flow-injection analysis of binary and ternary mixtures is demonstrated. The device is simple in construction. Its principle of operation is based on rapid sequential measurements of the absorbance of the complexes formed by the analytes with chromogenic reagents at the wavelengths corresponding to the emission maxima of three light emitting diodes (563, 580 and 638 nm).     

巯基化合物的电位分析法研究

本文对用直接电位法测试巯基化合物的可行性进行了研究。发现由硫化银，硫化汞等金属难溶盐制成的膜电极对６－巯基嘌呤，高胱氨酸，１，４－二巯基苏糖经合物可产生响应，其斜率为３０－１１０ｍＶ／ｐＣ，电极响应时间，则为十几秒至十几分钏，测试结果具有较好的重现性。因此，该方法可望得到应用。文中还对有关响应机理进行了探讨。     

聚对甲苯胺修饰电极的研制及其PH特性的研究

本文叙述了聚对甲苯胺修饰电极的制备及其电化学响应特性。在ＰＨ２－１３范围内电极电位与ＰＨ有良好的线性关系，电极响应应快，导电性能良好，抗干扰性能强，不受氧化还原物物质影响。用于测定饮料、湖水的ＰＨ值，结果与玻璃电极测定值基本相符。     

Potentiometric Membrane Sensor for Determination of Saccharin

A potentiometric poly(vinyl chloride) membrane sensor for determination of saccharin is described. It is based on the use of Aliquat 336S-saccharinateion-pair as an electroactive material in plasticized PVC membranes with o-nitrophenyloctylether or dioctylphthalate. The sensor is conditioned for at least two days in 0.1 mol L⁻¹ sodium saccharinate before use. It exhibits fast, stable and Nernstian response for saccharinate ions over the concentration range of 1.0 × 10⁻¹–5.0 × 10⁻⁵ mol L⁻¹ and pH range of 4.5–11. The sensor is used for determination of saccharin in some dosage forms. Results with an average recovery of 101% and a mean standard deviation of 0.2% are obtained which is compared favourably with data obtained using the British pharmacopoeia method. The sensor shows reasonable selectivity towards saccharin in presence of many anions and natural sweeteners.     

Multi-element trace analysis of tungsten

Investigations carried out in order to determine traces of 25 elements in tungsten in the lower g/g range are reported on. Atomic absorption spectrometry and plasma atomic emission spectrometry as well as solution photometry and activation analysis were the main techniques used.     

Spectrophotometric and titrimetric determination of gallium in minerals and ores using semimethylthymol blue

The composition, overall stability constant and molar absorptivity of the chelate of gallium(III) ion with semimethylthymol blue, SMTB, were determined spectrophotometrically in acetate buffer (pH 4.5–5). A violet Ga(SMTB) chelate was formed with logarithmic overall stability constant of 18.0±0.1 (I=0.1) and molar absorptivity of 4.25×10⁴l mol^–1cm^–1 (_max 580 nm). SMTB is proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of gallium(III). The colour development depends on time, temperature, pH and buffer species. The interference of different cations, anions and organic acids on gallium(III) determination was also investigated. Beer's law was obeyed for 3.5–31.3 gGa(III)/25ml (0.14–1.25 g ml^–1). SMTB was used for the spectrophotometric determination of gallium in different grade minerals and ores and the results were of acceptable error and relative standard deviation. Comparison between the two suggested methods and atomic absorption spectrometry for Ga(III) determination was carried out.     

Spectrophotometric assay of cephalosporins in pharmaceutical products,using chromotrope 2B and chromotrope 2R

A simple, rapid and sensitive Spectrophotometric method is proposed for the determination of cephadroxil (I), cephalexin (II) and cephradine (III). The method is based on ion-pair complex formation between these derivatives and Chromotrope 2B (C2B) or Chromotrope 2R (C2R), to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 542 and 564 nm for C2B and C2R, respectively. The optimization of the experimental conditions is described. The method has been used for the determination of 0.4–15, 0.4–14 and 0.4–18 g/ml of drugs I, II and III, respectively. The accuracy of the method is indicated by the excellent recovery (100.0±1.7%) and the precision is supported by the low relative standard deviations 1.5%. The sensitivity of the method is discussed and the results are compared with the official method. The interference from common degradation products and excipients was also studied. The proposed method was applied successfully to the determination of the different cephalosporins in dosage forms, with good precision and accuracy. The results were compared with those given by the official B.P. 1993 method.     

Kinetic determination of trace levels of selenium(IV) and total selenium by Nile Blue A/hydrogen peroxide method

A kinetic method for the determination of selenium(IV) traces is proposed, based on its inhibitory action on the oxidation of Nile Blue A by hydrogen peroxide in phosphate buffer (pH 10.5). A linear dependence was established between the rate of the proposed indicator reaction and selenium concentration in the range 9.5 × 10^–2-1.58 ng cm^–3. The experimental conditions of maximal selenium effect were established. Selenium, determined by the tangent method, was determined at concentrations over the range 0.22–1.26 ng cm^–3, with relative standard deviations up to 4.5%. The reaction rate was followed spectrophotometrically. The effect of foreign ions on the accuracy of this method was also investigated. The method was applied to the determination of selenium in pharmaceutical preparations and wheat flour.     

铜(Ⅱ)-铬天青S-过氧化氢体系催化光度法测定痕量铜

本文研究了在氨水介质中,痕量铜对过氧化氢氧化铬天青S褪色反应的催化作用,建立了一个催化光度法测定痕量铜的新方法。线性范围为0～20ng/mL,检出限为5.59×10~(-11)g/mL,并用于铝合金标准样品,环境标准样品和自来水中痕量铜的测定。     

银（Ⅰ）－硫脲－四正丁基溴化铵体系电致化学发光法测定水中痕量银

本文研究了银（Ⅰ）－硫脲－四正丁基溴化铵体系的电致化学发光（ＥＣＬ）。发现在正矩形脉冲下，银对含有硫脲的ＴＢＡＢｒ溶液的ＥＣＬ有明显催化作用，银（Ⅰ）的浓度在１．４×１０￣（－８）～３．５×１０￣（－６）ｍｏｌ／Ｌ范围内与ＥＣＬ强度呈良好线性关系。检出限为９．０×１０￣（－９）ｍｏｌ／Ｌ相对标准偏差为５％。用于天然水中银的测定，获得较满意的结果。