Masahiro Tsubouchi

Spectrophotometric determination of anions by solvent extraction with neutral red

Abstract Spectrophotometric methods are proposed for the determination of anions such as thiocyanate, perchlorate and iodide. The methods are based on solvent extraction of the ion pairs formed between colored neutral red cations and the anions into an organic solvent. Mercury(II) can also be determined by extraction of the bromomercurate(II) complex with neutral red. Calibration graphs were linear in the range 10 -6 –10 -5 M for each anion or mercury(II) in aqueous solution. Optimal conditions for the extraction and the composition of the extracted species are described.

Determination of poly(oxyethylene) non-ionic surfactants by two-phase titration.

The solvent extraction of non-ionic surfactants with sodium hydroxide and tetraphenylborate has been studied, and a method developed for the determination of non-ionic surfactants by two-phase titration. A hydrophobic indicator system was used. The method is valid only when the concentration of anionic surfactant in the sample solution is lower than 1 x 10(-4)M.

Hydrophobic indicators for two-phase titrations and their application to the determination of silver and pentachlorophenol

The hydrophobic dyes tetrabromophenolphthalein ethyl ester and 2,6-dichlorophenolindo-phenol are proposed as visual indicators for two-phase titrations. The aqueous phase is colourless throughout the titration and these indicators make it possible to detect the end-point of the titration by the colour of one or the other phase. The indicators allow the two-phase titration of the silver(I)-1,10-phenanthroline complex with tetraphenylborate and of pentachlorophenol with tetraphenylphosphonium chloride.

Spectrophotometric determination of strychnine and methylatropine by extraction with tetrabromophenolphthalein ethyl ester

A new application of monoacidic dyes is reported for the determination of strychnine and methylatropine. The method is based on solvent extraction into 1,2-dichloroethane of the ion-pair or addition compound formed between tetrabromophenolphthalein ethyl ester and quaternary ammonium salts or alkaloids. The absorbance of the extracts is linearly dependent on the concentration of strychnine or methylatropine initially present in the aqueous solution.

A sensitive two-phase titration of anionic surfactants with a dilute tetraphenylphosphonium chloride solution

Abstract A visual indicator method is described for titrations of anionic surfactants with 5 × 10 -5 M tetraphenylphosphonium solution. Two dyes, the hydrophilic neutral red and the hydrophobic tetrabromophenolphthalein ethyl ester, are used as indicator in the presence of 1,2-dichloroethane.

Spectrophotometric Determination of Atropine with Tetrabromophenolphatalein Ethyl Ester

テトラブロムフェノールフタレインエチルエステルを含むアルカリ性水溶液を1,2-ジクロルエタンとともにふりまぜると,その有機層は黄色を呈する。このとき微量のアトロピンが共存すると有機層は赤紫色を呈する。このような現象を利用して無色のアトロピンを比色定量する方法を確立した。pH9.5-10.5の水溶液から抽出したときにほぼ最大一定の吸光度が得られる。測定波長576mμにおいて1.6×10-6-8.0×10-6mol/lのアトロピン濃度につき検量線が直線となる。呈色種は試薬とアトロピンが1:1の組成比である。本法は感度がすぐれており呈色も安定である。本法を製剤中のアトロピンの定量に応用した。

Colorimetric determination of homatropine with tetiabromophenolphthalein ethyl ester

A colorimetric method for the determination of homatropine has been developed by means of solvent extraction, In the recommended procedure for preparing calibration curve, 210 ml of a standard homatropine solution (2.0×10-5M) is taken in a separatory funnel, and 5 ml of borate (0.1M) -phosphate (0.3M) buffer (pH 8.5) and 2 ml of a tetrabromophenolphthalein ethyl ester (TBPE) ethanol solution (4×10-3M) are added. It is diluted to 25 ml with water, and shaken with 10 ml of 1, 2-dichloroethane for 2 min. The extract is filtered through a dried filter paper to remove droplets of water. The absorbance is measured at 570 mμ against a reagent blank.The colored species was assumed to be [homatropine]·[H(TBPE)] (red-violet) and [quaternary ammonium ion]+·[TBPE]- (blue).