Ryozo Nakashima

Syntheses of azo dyes containing 4,5-diphenylimidazole and their evaluation as analytical reagents

Abstract Eight azo dyes containing the 4,5-diphenylimidazole group have been synthesized, and their potential for determinations of metals has been studied spectrophotometrically. Of these reagents, the pyridylazo and quinolylazo derivatives are suitable as chromogenic reagents, the best being 2-(quinolylazo)-4,5-diphenylimidazole (QAI), which reacts with several metal ions. The copper and mercury complexes of QAI show molar absorptivities of the order of 80 000 l mol−1 cm−1.

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Abstract Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beers law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10 5 1 mol −1 cm −1 at 555 nm.

Determination of niobium, titanium and zirconium by high-frequency plasma torch emission spectrometry and its application to steel

Abstract The basic conditions for the determination of niobium, titanium and zirconium with an argon plasma and a Hitachi UHF Plasma Spectrascan operated at 2450 MHz and 450 W maximum output, have been established. The niobium 405.89-nm, titanium 365.35-nm and zirconium 339.19-nm lines gave detection limits of 0.5, 0.1 and 2.0 p.p.m., respectively, when pure solutions were used. Effects of gas flow rates, high-frequency output and concentration of acids were examined. In applications to steel, titanium was determined without prior chemical separation from iron at the 499.95-nm line, whereas niobium and zirconium could not be determined in the presence of large amounts of iron. When a cupferron precipitation method followed by extraction of iron with methyl isobutyl ketone was applied, satisfactory results were obtained.

Determination of silver in biological materials by high-frequency plasma-torch emission spectrometry.

Abstract Nanogram amounts or silver in small samples of biological materials can be determined by high-frequency plasma-torch emission spectrometry. Samples are digested with perchloric and nitric acids, silver is collected with a bismuth iodide carrier, and the precipitate is decomposed with concentrated nitric acid before dilution. Bismuth shows an enhancing effect on the silver emission at 328.06 nm, and the sensitivity is further improved by elimination of moisture in the aerosol with a second condenser at -3 to -5°C. The detection limit is 0.5 ng per 0.2 ml of sample solution. Condensed milk and whole blood were analyzed satisfactorily.

Determination of iron, manganese, and magnesium in high-purity molybdenum by high-frequency plasma torch emission spectrometry

Abstract The determination of impurities in molybdenum metals by high-frequency plasma torch emission spectrometry with direct introduction of sample solutions without prior separation has been studied. Iron, manganese and magnesium present in amounts greater than 0.005 % can be determined by means of the 248.8-nm, 279.5-nm and 279.6-nm lines, respectively. The lanthanum carrier technique, with 8-hydroxyquinoline as precipitant at pH 12–12.5 can be used when the content of these elements is less than 0.005 %. The effects of molybdenum and lanthanum on the spectral intensities of iron. manganese and magnesium are also discussed.

Determination of trace amounts of thorium and uranium in coal ash by inductively coupled plasma atomic emission spectrometry after extraction with 2-thenoyltrifluoroacetone and back-extraction with dilute nitric acid

A method of sample preparation is described that can be used for the determination of trace amounts of thorium and uranium in coal ash by inductively coupled plasma atomic emission spectrometry. After acid digestion of the samples, the elements are separated independently from the matrix by 2-thenoyltrifluoroacetone (TTA)-benzene extraction procedures. Thorium is extracted with 0.25 M TTA at pH 1.2 in the presence of ascorbic acid. Uranium(VI) is extracted with 0.16 M TTA at pH 3.5 in the presence of EDTA. The amount of EDTA to be added to the sample solutions must be properly controlled because an excess reduces the recovery of uranium. Thorium and uranium are finally measured in the back-extract in 2 M nitric acid. The detection limits were 11 µg l–1 for Th and 29 µg l–1 for U and the relative standard deviations ranged from 3.0 to 8.6% for Th and 3.9 to 4.3% for U.

Electrothermal atomic absorption spectrometric determination of ng g-1 levels of cadmium in bone after dithizone extractions

Abstract After removal of lipid and acid digestion of bone samples, cadmium is separated from the matrix by two extractions with dithizone in carbon tetrachloride. The first extraction at pH 3–3.5 removes cadmium from the matrix; the second extraction, at pH 8.5 in the presence of 2-hydroxyethylethylenediaminetriacetic acid, is needed to prevent suppression of the cadmium signal by zinc. Cadmium is finally measured in the back-extract into 0.24 M hydrochloric acid. Less than 10 ng g-1 cadmium in fresh bone can be determined within a relative standard deviation of 10%.

Polarographic analysis using potassium iodide as a supporting electrolyte: The polarographic behavior of trivalent arsenic

The polarography of arsenic(III) in 0.1 or 1.0 M potassium iodide solutions has been studied.