Determination of Nitrite via Reaction with Pyridine-4-Carboxylic Acid Hydrazide

Abstract

Nitrite is determined by its reaction with a measured but excessive amount of pyridine-4-carboxylic acid hydrazide in acid medium (when the two substances react in a 1:1 molar ratio) and evaluation of the surplus hydrazide by titration with chloramine-T in the presence of acidified potassium bromide, the end-point being shown by the decolorization of the methyl red indicator. Nitrate, copper(II), mercury(II), etc. are found not to interfere, and the determination of nitrite in the presence of diazotized aromatic amines is demonstrated.     

Scheme and studies of reference materials for volumetric analysis in Japan

This paper describes the history and scheme of reference materials and standard solutions for titrimetry in Japan. Titrimetry is one of the most fundamental and precise methods for determination of a constituent, based on the effective purity of reference materials in stoichiometric analysis. It has wide-ranging applications based on titrimetric reactions such as neutralization, redox, chelatometric, and precipitation titration processes, which are used in various analytical fields all over the world. Japanese Industrial Standards (JIS) have played an important role in establishing a stable supply of reference materials for titrimetry since the 1950s. There are several reports of preparations and their determination, including coulometric studies, in order to establish highly reliable reference materials. This paper briefly reviews the schemes and studies of standardization through the provision of reference materials and standard solutions based on JIS, and several applications in other standards. Presented at Berm-11, October 2007, Tsukuba, Japan.     

Determination of stoichiometry of Li1+yCoO2 materials by flame atomic absorption spectrometry and automated potentiometric titration

A rapid, accurate and precise analytical method to determine the stoichiometry of pure, excess lithium and magnesium-doped Li_1+yCoO₂ materials is described. The method is based on the determination of lithium, cobalt and magnesium by flame atomic absorption spectrometry after dissolution of samples in dilute hydrochloric acid. Five-point calibration curves using aqueous standard solutions have been constructed for all the analytes. Relative standard deviation (R.S.D.) of five repeated measurements are better than 0.3% for all metals when the absorbance signal of analytes is set near the middle of the regression lines.The total oxygen content is indirectly determined by potentiometric titration of average oxidation state of cobalt. The Co³⁺ present in the oxide powders is reduced to Co²⁺ at room temperature with a known excess of 0.1 M Fe²⁺ solution in 6 M sulphuric and phosphoric acid mixture. The samples completely dissolved in a few minutes developing a pink coloured and clear solution. The excess of Fe²⁺ ions is back titrated with potassium dichromate standard solution using automated potentiometric end-point detection. The difference between the total cobalt content (found by AAS) and Co³⁺ (found by potentiometric titration) gives the amount of Co²⁺ present in the materials. The S.D. of the determined Co³⁺ value has been estimated to be below 0.03 mg for samples of 10-20 mg. By the proposed method the LiCoO₂ is well characterised and can be applied as a standard reference material for use in lithium batteries technology.     

微分倒数示波计时电位法的研究—定量测试及滴定分析

首次利用微分倒数示波图定量测试微量金属离子并滴定分析药物，结果满意。     

滴定分析的统一数学处理(Ⅰ)——通用终点误差公式

本文建立了通用的滴定终点误差公式,考虑了副反应的影响,也适用于非水滴定。可用于判断准确滴定的可能性或分步滴定的可行性,选择指示剂的用量和确定最佳分析条件等。     

Coulometric argentometric determination of microamounts of sulphur in iron and steel after reduction to hydrogen sulphide with iron(II) in strong phosphoric acid medium

A coulometric method was developed for the determination of microamounts of sulphur in iron and steel. Hydrogen sulphide is quantitatively evolved by reduction with iron(II) in strong phosphoric acid medium and is titrated with electrolytically generated silver ion from a silver anode. Microamounts of sulphide (2.96–224.3 μg) in sodium sulphide standard solutions could be determined with an error of only a few percent. Sulphur in a potassium sulphate standard solution is quantitatively reduced to hydrogen sulphide and could be separated from the solution by heating and determined accurately. Trace amounts of sulphur (7–100 μg g^?1) in iron and steels could be determined with a standard deviation of 0.7–2.1 μg g^?1.     

神经网络法用于多元混酸同时测定

利用多层神经网络误差反向传播算法处理酸碱电位滴定数据，求得出多元混合酸各组分的浓度，优化了神经网络的结构和参数，测定了三组分有机酸混合样品，结果良好，平均相对偏差ＲＳＤ≤４％。     

Conductimetric,Potentiometric and Visual Titrimetric Methods for Analysis of Nadolol

Abstract

Nadolol, a beta-blocking agent, has been assayed in pure form and in pharmaceutical formulation by acidimetric titrations using visual, potentiometric and conductimetric methods for detecting the end point in aqueous as well as in non-aqueous media. The method of assay involves the determination of the amount of nadolol in a given weight of sample. Six samples were run for each method and the percentages of recovery of nadolol from its tablets were calculated. For aqueous titrations, the average percentages of recovery for the visual, potentiometric and conductimetric methods are 100.6 ± 1.0, 99.3 ± 1.9 and 100.1 ± 2.0 respectively. For the non-aqueous titrations, the average percentages of recovery are 98.6 ± 0.8, 99.5 ± 0.5 and 98.4 ± 1.3 for the visual, potentiometric and conductimetric methods respectively.     

D1-Differential Potentiometric and 1H-NMR Spectrometric Determinations of Ketoconazole and its Formulations

Abstract

Two rapid and direct quantitative assays have been investigated for ketoconazole alone and in tablet form. the first one is a non-aqueous potentiometric titration in which the equivalence point has been located graphically using its distinct and sharp D₁differential (peak-shape) potentiograph. the second is based on ₁H-NMR spectrometry and involves the integration of the methyl protons-signal of ketoconazole (at 2.07 δ) relative to that of benzocaine (at 1.30 δ) which is used as internal standard. the obtained results were in good agreement with regard to accuracy, precision as well as sensitivity and reproducibility. However, by comparison with the official USP procedure, the two methods were significantly more accurate and more sensitive. the validity of the two methods were confirmed using the authentic addition technique.     

Thallimetric photochemical oxidation in titrimetric and spectrophotometric methods for the analysis of mixtures of oxalate and hydrogen peroxide

Thallium(III) in the presence of bromide photochemically oxidizes oxalate and hydrogen peroxide, whereas in the presence of a large excess of chloride, only oxalate is oxidized. Two procedures are based on these observations. In the titrimetric method (applied to mmol amounts of analytes) the thallium(I) formed is determined with bromate. In the spectrophotometric procedure (μmol amounts of analytes) unreduced thallium(III) is determined at 260 nm. In each case measurements are made after reaction under both conditions, so that both analytes can be determined.