Eijiro Kamata

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.

Syntheses and spectrophotometric studies of 5-(2-pyridyl-azo)-2,4-diaminotoluene and its derivatives as analytical reagents : Spectrophotometric determination of cobalt with 5-[(3,5-dichloro-2-pyridyl)azo]-2,4-diaminotoluene

Abstract Seven pyridylazo dyes containing the m -tolylenediamine group were synthesized and their analytical potential for the determination of cobalt was studied spectrophotometrically. The molar absorptivities and selectivity of these reagents increased compared with those of PADAB. Cobalt(II) and 3,5-diCl-PADAT (5-[(3,5-dichloro-2-pyridyl)azo]-2,4-diaminotoluene) at pH 3 form a complex which is very stable even in the presence of strong mineral acids. The complex has two absorption maxima at 548 and 590 nm in hydrochloric acid (2.4 M ) solution. The color is very stable and the system conforms to Beers law; the optimal range for measurement in a 1-cm cell is 0.01–0.4 p.p.m. cobalt. In practice, this color reaction is specific. The molar absorptivity is 1.38 ·10 5 1 mol -1 cm -1 at 590 nm. The sensitivity is 0.00042 μg Co cm -2 at 590 nm for log I 0 /I = 0.001. The method was applied to the determination of cobalt in steel and waspaloy.

I-[(5-Bromo-2-pyridyl)azo]-2-naphthol as a possible new chromogenic reagent

Abstract The heterocyclic azo compound, 1-[(5-bromo-2-pyridyl)azo]-2-naphthol (5-Br-β-PAN), forms various coloured metal chelates, wliich can be extracted with different organic solvents. Most of the reacting metals form reddish chelates, except for cobalt-(III) and palladium(II) (green), and vanadium(V) (olive). Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelates. A correct choice of pH, solvent and masking reagents allows 5-Br-β-PAN to be made reasonably selective.

1-[(5-Chloro-2-Pyridyl)Azo]-2-Naphthol as a new extraction- photometric reagent for metals

Abstract The heterocyclic azo compound, 1-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-Cl-β-PAN), forms various coloured metal chelates, which can be extracted with different organic solvents. Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelate. Although the bathochromic shifts produced on chelation are no greater than those with 5-Br-β-PAN, the selectivity is increased. The reactivity of tri- and tetravalent metal ions is decreased appreciably by introduction of the chlorine. A correct choice of pH, solvent and masking reagent allows 5-C1-β-PAN to be made reasonably selective.

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%.

Rapid BOD Measurement Using Activated Sludge

DO (溶存酸素) で飽和した活性汚泥懸濁液の液面が外気と接触した状態で, ばっ気することなく懸濁液中のDO濃度の減少を連続的に計測した場合, DO濃度は直線的に減少する。検水 (基質または有機汚濁物を含む) を添加すると急激に減少した後, 安定し再び直線的な減少勾配を示す。DO濃度の減少勾配が検水添加前と同じになった時点で成立する平行線の間のDO濃度の差が添加した基質濃度に比例することから, 簡易, 迅速にBOD (迅速BOD) を求める方法である。検水採取量は100mlまでとする。本法の測定時間は約10分である。本法では, 活性汚泥濃度はMLSSとして3,000～5,000mg・l-1の範囲で, 検水の迅速BOD測定に影響を与えない。

A procedure for the separation of the mixture of succinic and lactic acids with silica column chromatography

The mixture of succinic and lactic acids has been hardly isolated even with a longer column. In practice, in order to transfer the sample solution containing small amounts of the acids quantitatively onto a silica column (55cm long, 0.7cm dia.), the solution is mixed with one gram of silica gel which gives 6 cm of the sample column. The two acids are completely separated. by the development with an 18% tert-butanol-chloroform accompanied by a preliminary development with 10ml of 14% tert-butanol-chloroform. The effect of the preliminary development to give the clear-cut separation of the elution bands is attributed to the concentration gradient of tert-butanol occurring around each solvent front, namely, this concentration gradient is effective in constricting the individual chromatograms in the column.