Tsutomu Fukasawa

Catalytic spectrophotometric determination of nitrite using the chlorpromazine–hydrogen peroxide redox reaction in acetic acid medium

In a 0.2 mol l–1 acetic acid–6.6 × 10–3 mol l–1 oxalic acid medium at 20 °C, 5 × 10–3 mol l–1 chlorpromazine hydrochloride (CPH) was oxidized by 5 × 10–2 mol l–1 H2O2 with the reaction being catalysed by nitrite ions. The maximum absorbance occurs within 2–4 minutes of the start of the oxidation reaction and is proportional to the nitrite concentration; this allows the determination of nitrite in the range 3–1500 ng ml–1. Reagent concentrations, except for CPH, have little effect on the determination. The effects of experimental conditions and foreign ions are described. The interference of iron(III) can be masked by oxalic acid and ethylenediaminetetraacetic acid. The method was applied to the determination of nitrite in rain and river water.

Flow injection determination of trace vanadium with catalytic photometric detection

Abstract A catalytic photometric detection system based on the chromotropic acid—bromate reaction is adapted to a flow injection system for the rapid, simple and sensitive determination of vanadium. Vanadium in the range 0.3–4.8 ng (10–160 ppb) can be determined at a rate of ca. 60 samples per hour.

Catalytic determination of vanadium using the perphenazine–bromate redox reaction and a citric acid activator

Citric acid was found to have a highly activating effect on the vanadium-catalysed oxidation of perphenazine (PP) with bromate. An extremely sensitive, selective and simple method was developed for the determination of vanadium based on this effect. The reaction rate was followed spectrophotometrically by monitoring the formation of the red oxidation product of PP at 526 nm within 1 min of mixing. Using the recommended procedure, vanadium can be determined up to 6.5 ng ml–1 with a linear calibration graph and a detection limit of 0.08 ng ml–1. A suggested mechanism of the reaction and the activating mechanism of citric acid is presented. The method surpassed the standard Fishman–Skougstad catalytic method in sensitivity, selectivity and speed and was successfully applied to the determination of vanadium in polluted river waters.

Effect of tartrate on vanadium-catalysed chlorpromazine-bromate redox reaction and its application to the determination of vanadium in natural waters

The spectrophotometric determination of vanadium using the catalytic oxidation of chlorpromazine (CPH) with bromate was sensitized in the presence of sodium tartrate (TART) as an activator. The red oxidation product of CPH was monitored at 525 nm within a 1 min reaction time. Vanadium was determined by the measurement of its oxidation rate. The detection limit was 0.2 ng cm–3 using optimized reaction conditions of 5 × 10–4 mol dm–3 CPH, 5 × 10–3 mol dm–3 KBrO3, 0.1 mol dm–3 TART and 0.35 or 0.5 mol dm–3 H3PO4 at 25 °C. The calibration graph was linear up to 150 ng cm–3 VV or VIV. The interferences from Br–, I–, S2– and NO2– were eliminated by the addition of AgI and methanol. The proposed method was successfully applied to the determination of vanadium in rain and river waters.

Determination of trace vanadium in natural waters by a combined ion exchange—catalytic photometric method

A sensitive, selective and simple method is described for the determination of trace vanadium in natural waters. Vanadium is separated and concentrated by a combined cation- and anion-exchange procedure in 0.05 M HCl—0.1 % H2O2 media, and determined by the catalytic method based on the oxidation of gallic acid by bromate. The proposed method is applied to the analysis of natural waters. The relative standard deviations are 3.9 % for 0.8 p.p.b. of vanadium in river water and 3.2 % for 1.9 p.p.b. of vanadium in lake water (surface). As little as 0.03 p.p.b. of vanadium can be determined in samples of 100 ml or less.

Determination of trace manganese in high-purity titanium, silicon and mineral acids by a flow-injection method based on a catalytic reaction

Abstract A preliminary microscale ion-exchange separation and a three-line flow-injection manifold are described for the spectrophotometric determination of trace (ng-μg g −1 ) manganese in ⩾ 10 mg- samples of high-purity titanium and silicon. The catalytic effect of manganese on the malachite green/periodate reaction is utilized. The method is also conveniently applied to the determination of sub-μg l −1 levels of manganese in 1–3-ml samples of high-purity hydrofluoric, hydrochloric and nitric acids.

State analysis and relationship between lattice constants and compositions including minor elements of synthetic magnetite and maghemite

Abstract Chemical formulae were constructed after the determination of the composition including the minor elements in commercially available synthetic magnetite and maghemite, which gave similar x-ray diffraction patterns with close diffraction lines. The contents of FeO in reagent grade magnetite and high-purity magnetite powders were about 8 mol% less and that in a needle-shaled magnetite powder was about 24 mol% less than the 50 mol% in the expected composition (FeO · Fe2O4) of magnetite. They were solid solutions of magnetite-maghemite (γ-Fe2O3) including minor elements in the lattice. A linear relationship was found between the total mole percentage if divalent iron, manganese and zinc oxides and their lattice constants ac corrected by increments of the lattice constant based on the replacement of divalent iron with manganese and zinc atoms. The possibility of a non-destructive total analysis of the same iron oxide samples by an x-ray method is discussed. It was found that magnetite was considerably oxidized in air even at 110°C to form a solid solution, but not to form any separated compound.

X-ray diffraction analysis of airborne particulates collected by an Andersen sampler. Compound distribution vs. particle size.

Commercially available Nuclepore and Fuji microfilters were used as the collection media in an Andersen sampler. After sampling, the filter with the particulates was dissolved in dichloromethane, centrifuged to reduce the amount of the filter material, and formed to a suitably small film for X-ray diffraction analysis. Preparation of the small-film sample, sample mounting on the diffractometer, recovery, reproducibility in the X-ray diffraction intensity, identification of compounds in the particulates, and construction of a compound distribution vs. particle size curve are described. The distribution curves of the compounds are also given for the particulates collected in dry and wet seasons as examples.

Flow-injection spectrophotometric determination of trace vanadium based on catalysis of the gallic acid bromate reaction

Abstract High sensitivity is obtained by using high concentrations of gallic acid and bromate, although the uncatalyzed reaction is significant. Various reactant concentrations, reaction temperature, pH and residence times can be used to alter the linear calibration ranges and sensitivity for vanadium. With reagent streams of 1.76 M bromate and 0.06 M gallic acid at pH 3.8 (each at 1 ml min −1 ), 0.2–20 ng of vanadium (20-μl injections) can be determined at 30°C. Oxidized gallic acid is detected at 380 nm. When the bromate concentration is decreased to 0.5 M and the temperature is 65°C, 0.05–4 ng of vanadium can be determined; the relative standard deviation is ca. 5% for 0.6 ng of vanadium. The toleranes for Al(III), Fe(III), Mo(VI) and iodide are 10 ng, 10 ng, 50 ng and 200 ng, respectively, for the determination of 1 ng of vanadium. About 12 samples can be injected per hour.

Highly sensitive spectrophotometric kinetic determination of vanadium by catalysis of the gallic acid-bromate reaction

Abstract Conditions are described for improving the speed and sensitivity of this catalytic determination of vanadium. The reaction of 0.018 M gallic acid with 0.96 M sodium bromate at pH 3.8 and double-beam spectrophotometric measurement at 380 nm are recommended. The calibration curves are obtained by the tangent (2-point) and fixed-time (single-point) method. The highest practical sensitivity at 22–30°C was ca. 40 pg for an absorbance change of 0.0005, 50 times better than previously. The detection limit was ca. 0.5 ng of vanadium. Reaction at 50°C gave even better sensitivity.