Tsuyoshi Nomura

Indirect polarographic determination of microgram amounts of iron by means of the catalytic oxidation of 5-aminosalicylic acid

Abstract A sensitive indirect polarographic determination of microgram amounts of iron by means of the catalytic oxidation of 5-aminosalicylic acid with sodium bromate was examined. The most suitable conditions of the pH range, reaction temperature and standing time are 4.8–5.4, 50°C and 1 h respectively. A linear calibration curve is obtained over the range 0.002–0.016 μg ml −1 iron with a relative error of about 3%. Interference by various ions and compounds and the application to the determination of iron in city water and river water are described.

Tensammetric determination of microgram amounts of EDTA using a catalytic oxidation of 2-amino-4-methylphenol with vanadium

Abstract The catalytic oxidation of 2-amino-4-methylphenol proceeds rapidly with microgram amounts of vanadium in the presence of sodium chlorate. The oxidation product of this reagent shows a sensitive tensammetric wave at the potential about −0.45 V vs. SCE (pH 3.0). The oxidation reaction is intensively inhibited by EDTA according to the formation of a stable vanadium-EDTA complex. This inhibitory effect for the catalytic oxidation of 2-amino-4-methylphenol is applied to the determination of microgram amounts of EDTA. Using the procedure recommended, EDTA can be determined accurately in the concentration range between 0.015 and 0.29 μg ml−1. Interferences of foreign species are described.

Silver Diethyldithiocarbamate Membrane as a Nitrate Ion Selective Electrode

Abstract A new type of an ion selective electrode for nitrate ion was developed. Silver diethyldithiocarbamate, obtained by mixing a silver nitrate solution to a sodium diethyldithiocarbamate solution, was used as the active membrane material. The response to nitrate ion is linear with a Nernstian slope (60 mV/1 pNO3) over the concentration range 10−1 to 10−6 M in the pH range from 4 to 11. From IR spectra, the potential response to nitrate ion may arise from nitrate ion adsorbed in the membrane material. No response is observed to any cations, except hydrogen, mercury (II) and silver ions.

Tensammetric determination of microgram amounts of vanadium by catalytic oxidation of o-aminophenol.

A tensammetric method is proposed for the determination of microgram amounts of vanadium, based on catalysis of the oxidation of o-aminophenol with sodium chlorate in acidic solution (pH 2.0). The oxidation product gives a very sensitive tensammetric wave; under optimum conditions, the wave-height is proportional to the concentration of va vanadium. From 0.2 to 3.0 mug of vanadium can be determined in a final volume of 50 ml. Mo(VI), W(VI), Mn(VII), Ce(IV) and large amounts of Al(III) and Fe(III) cause positive errors, and Hg(II) and thiosulphate negative errors. Interference from Fe(III), Al(III) and Cu(II) can be eliminated by solvent with oxine at about pH 8.0.

Alternating current polarographic determination of microgram amounts of iodide ion by means of the catalytic oxidation of 1-amino-2-naphthol-4-sulfonic acid

The catalytic oxidation of 1-amino-2-naphthol-4-sulfonic, acid proceeds quickly with microgram amounts of iodide in the presence of sodium chlorate at pH between 1.3 and 2.0. The oxidation product shows a sensitive tensammetric wave at potentials of about +0.03 V vs. SCE (pH 1.75), so that the catalytic reaction was applied for the determination of microgram amounts of iodide ion. The most suitable conditions of the pH range, the concentration of ANS and sodium chlorate, reaction temperature and standing are 1.3–2.0, 3 × 10−4 M, 0.05 M, 50° C and 1 h respectively. Using the recommended procedure, iodide ion can be determined precisely in the concentration range 0.4–6.5 ng ml−1 with a relative error of about 3%. Interference of foreign species and the application to the determination of total iodine in river and sea water are described.

Use of a Tensammetric Wave for the End-Point Detection in Chelatometry

Abstract A new method for the end-point detection in complexometric titration using a tensammetric wave of organic reagents such as oxine and alizarin complexone (ALC) was studied. The tensammetric wave of these reagents disappears by their chelate formation and reappears by the liberation of free indicator during the exchange reaction between indicator chelate and EDTA. This mechanism is utilized for the end-point detection in complexometric titration of metals. Since the sensitivity of tensammetric wave is extremely high, very sharp end-point can be obtained for the titration of metals even in the concentration of 10−5M.

Alternating current polarographic determination of microgram amounts of palladium by means of the catalytic reduction of 2-methyl-1,4-naphthoquinone in the presence of hypophosphorous acid

Abstract An accurate and specific electroanalytical method for the quantitative detemination of microgram amounts of palladium is based on the catalytic effect of palladium on the reduction of 2-methyl-1,4-naphthoquinone (MNQ) by hypophosphorous acid in acidic solution. Under the recommended conditions, the reduction of MNQ is proportional to the concentration of palladium present. The concentration of palladium is determed by measuring the decrease of the ac polarographic wave of MNQ at potentials about +0.03 V vs. SCE (pH 1.84). The most suitable conditions of pH range, concentration of hypophosphorous acid and MNQ, reaction temperature and standing time are 1.0–2.2, 0.05 M, 5×10−5 M, 20°C and 1 h respectively. Under the recommended procedure, palladium can be determined precisely in the concentration range of 0.005–0.064 μg ml−1 with a relative standard deviation of about 2%. Interference of foreign species is described.

Determination of Copper by Catalysis of the Oxidation Reaction of O-Amino Phenol

Abstract The oxidative dimerization reaction of o-amino phenol with dissolved oxygen is catalyzed by the presence of an extremely small amount of copper(II) ion. In a. c. polarography, the oxidation product of o-amino phenol gives a very sensitive tensammetric wave in the pH range 5 to 9. This tensammetric wave is used for the determination of copper(II) ion from 0.3 to 3.5 μg/100 ml final solution.

Rapid polarographic determination of manganese in ferromanganese and manganese slag

フェロマンガンおよびマンガンスラッグ中のマンガンをKolthoffらの提案しているピロ燐酸支持塩を用いてポーラログラフ分析を試みた結果つぎのことがわかった.(1)0.3Mピロ燐酸塩中のポーラログラフ波はpHが2.5～3.4の範囲内では一定値を示し,マンガン(III)→(II)の比較的よい還元波を示す.(2)極大抑制剤としてゼラチンの0.01%濃度を使用した場合50mg/100ml位までのマンガン量は良好な比例性が成立するが,それ以上になると極大も現れ比例性も悪くなる.(3)ピロ燐酸塩中でのマンガン(III)波は+0.15Vvs.S.C.E.ですでに限界電流に達するので,大過剰の鉄,およびクロム,バナジウム,塩素の他は妨害とならない.(4)実際の試料について蒼鉛酸ソーダ法と比較分析したところ,精度もよく,迅速に分析することができた.