Tamotsu Yashiro

Analytical study of low-concentration gases : IV. Investigation of the reaction by trapping nitrogen dioxide in air using the triethanolamine method

Abstract An investigation was made of the absorption of nitrogen dioxide (NO2) by the triethanolamine (TEA) plate method, which is simple for determination of NO2 in air. NO2, generated from a permeation tube was exposed to a TEA plate and to TEA-coated glass beads. One of the reaction products was found to be N-nitrosodiethanolamine (NDEA). It was also detected on a TEA plate subjected to exposure to NO2 in air, as in the case with the permeation tube reaction. The product was positive to the Liebermann nitroso reaction, and the product and NDEA synthesized by NO2 and diethanolamine were identified by gas chromatography, gas chromatography—mass spectrometry and UV spectrometry.

Determination of human serum ceruloplasmin by measurement of its 3,3′,5,5′-tetramethylbenzidine oxidase activity

The copper-containing glycoprotein, ceruloplasmin, in plasma shows oxidase activity towards various substrates [l, 21 such as aromatic polyamines, polyphenols, ascorbic acid and Fe’+. The determination of ceruloplasmin by a calorimetric method using p-phenylenediamine (PPD) was first reported by Ravin [3]. Thereafter, many methods based on several reactions have been reported; these include oxidative calorimetric methods [4-81 using PPD or its derivatives and ascorbic acid, enzymatic methods [9, lo] using Fe2+, chromatographic methods [ll, 121 and immunodiffusion methods [13, 141. The calorimetric methods are the most widely used but are not as sensitive as the enzymatic methods. Schosinsky et al. [15] devised a sensitive calorimetric method to determine the odianisidine oxidase activity of ceruloplasmin but such benzidine derivatives are not used now because they are carcinogenic [ 16, 171. However, some benzidine derivatives such as 3,3’,5,5’-tetramethylbenzidine (TMB) [18] and dicarboxidine are not carcinogenic [19]. Experiments have been conducted to test whether TMB can be used to determine ceruloplasmin by measurement of its TMB oxidase activity.

Analytical study of low-concentration gases : II. Collection of acetaldehyde at low concentrations in air in a solid reaction tube and its analysis using a flame thermionic detector

Abstract A method for the determination of acetaldehyde at low concentrations in air is discussed. Acetaldehyde was collected using silica gel treated with 2,4-dinitrophenylhydrazine. Recoveries were 98–100% with good analytical precision, the coefficients of variation being less than 5% when 50–100 1 of air were sampled. Determination by gas chromatography with a flame thermionic detector gave a detection limit of 0.05–0.25 ppb and a coefficient of variation of about 4%. The method is precise, simple and rapid. Acetaldehyde concentrations in air determined by this method were 3–4 ppb.

Analytical study of low-concentration gases : III. Determination of lower fatty acids and their trimethylsilyl esters in air by gas chromatography

Abstract A gas chromatographic method for the determination of lower fatty acids as odour pollutants is discussed. A sample gas was introduced on to glass beads coated with 1% sodium hydroxide solution to collect fatty acids, which were isolated in a sampling tube and then submitted to gas chromatography without concentration. These fatty acids were reacted with trimethylsilylimidazole to form trimethylsilyl esters, which were also subjected to gas chromatography. The latter method resulted in a sensitivity 5–10-fold greater than that by the former method. The recoveries were more than 90% in both methods, with coefficients of variation of less than 5% in the former and about 8% in the latter. The gas chromatographic method gave good reproducibility, with detection limits of 0.5–1 ppb when 200 1 of gas were sampled. Air quality was determined by both the methods on samples from a hog farm and a refuse incinerator.

Kinetics and mechanism of the acid-base equilibrium of mexazolam analogues: A modification of the mechanism proposed previously for mexazolam

Abstract Oxazolidine ring-opening and ring-closing (acid-base equilibrium) reactions of 3-methyl-11 b -hydrogen ( 1 ) and −11 b -methyl ( 2 ) analogues of mexazolam ( 3 ) have been studied kinetically in solutions of various pH values and at 25°C. Compound 2 isomerizes to the cis/trans isomers (referring to substituents at the 3- and 11 b -position) in methanol-d 4 withh a half-life of baout 50 min, and at equilibrium the ratio of the cis to trans isomers is 6.9:1. The acid-base equilibrium reactions of 1 and 2 proceed via two steps due to the cis and trans isomers, the reactions of the trans isomer being faster than those of the cis isomer. The large difference between the cis and trans isomers of 2 is ascribed to their conformational differences (normal boat X 1 and flat form Y 11 , respectively). These results required a modification of the mechanism previously proposed for mexazolam (Kurono et al., Chem. Pharm. Bull. , 35 (1987) 3831–3837).

Stereochemistry of benzodiazepinooxazoles: crystal structure and NMR spectroscopic investigations of new conformational variants of mexazolam analogues

The varied stereochemistry of mexazolam analogues is described on the basis of six crystal-structure analyses of the 11b-hydro (2), methyl (3 and 4), phenyl (5) and 2′-chlorophenyl (6; mexazolam) derivatives of 3-methylbenzodiazepinooxazole and the benzodiazepinooxazole (1), all determined by X-ray diffraction techniques. Two new comformations for the benzodiazepinooxazole ring system have been found in these analyses, i.e., a flat conformation YII in the case of 2 and 3, and a skewed conformation YI in 1. The usual ‘boat-wing’ conformation XI has been found in compounds 4–6. The solution-state 1H NMR spectra of 1, 3 and 4 at room temperature have been examined by phenyl ring-current effects and support retention of the three types of solid-state conformation. In polar solvents, all these compounds (except for 1) show a diastereoisomeric equilibrium of trans↔cis interconversion through epimerization at the 11b position. The diastereoisomeric and conformational differences in these compounds are discussed along with the steric interaction of the substituents.