Hiroyuki Masaki

Determination of the stable isotope of nitrite flux in the blood of mice by gas chromatography—mass spectrometry with selected ion monitoring

A simple and reliable method for the determination of the stable isotope of nitrite (15NO2) flux in the blood of mice is described. It is based on the reaction of 15NO2 with 1-hydrazinophthalazine in acidic solution to form [15N]tetrazolophthalazine, a stable compound which can be extracted with an organic solvent and then determined by gas chromatography-mass spectrometry with selected ion monitoring using the pentafluorobenzoyl ester of 2,4-dinitro-6-sec.-butylphenol as an internal standard. Amounts of 0.2-10 micrograms of 15NO2 can be determined. The detection limit of 15NO2 was 0.1 microgram/ml. This is a specific method for 15NO2. The procedure for determining 15NO2 in the blood of mice involves extraction with solvent, followed by further clean-up by alumina column chromatography; the detection limit is 0.05 microgram. With the new technique we were able to perform a metabolic fate study of nitrite in the blood of mice following a single oral dose of 15NO2 or the stable isotope of nitrate (15NO3).

Residues of Clopidol (3, 5-Dichloro-2, 6-dimethyl-4-pyridinol) in Tissues and Eggs of Chickens

Residues of clopidol (3, 5-dichloro-2, 6-dimethyl-4-pyridinol) in chicken tissues and eggs were studied. Clopidol isolated from various tissues was determined by gas chromatography. Chickens of 10 weeks of age were given feed containing 250, 375 and 750ppm of clopidol for 10 days before laying eggs. The average contents of clopidol in the eggs were 6ppm, 10ppm and 19ppm, respectively. The concentration ratio (clopidol in whole egg/clopidol in feed ×100) of clopidol was found to be 2.64% on average, and clopidol in the egg disappeared within approximately one week.In other experiment, chickens of 4 weeks of age were given clopidol-containing feed (250, 375 and 750ppm) for 8 weeks. High concentrations of clopidol were found in the liver, blood and kidneys as compared with the breast, thigh muscle and fat. After cessation of medication, the clopidol concentration in each tissue fell below 0.1ppm within 3 days.

The Preservative Effects of Propionic Acid for Bread and Sponge Cake

The preservative effects of propionic acid for bread and sponge cake stored at 25°C was investigated.The results obtained were as follows:1) Addition of 0.25% propionic acid in sponge cake and bread prolonged their shelflife for two days as compared with the non-addition of propionic acid as revealed by sensory test.The sponge cake and bread with added propionic acid at the level of 0.25% maintained their quality for four to five days as shown by the bacterial, molds, yeasts counts.2) In the inoculated studies using Bacillus subtilis results showed that in the nonaddition of propionic acid it exhibited Rope in bread, four days after inoculation. On the other hand, the bread with added propionic acid at the level of 0.25% could be preserved for seven days at about 25°C.While the sponge cake with added 0.25% propionic acid could be preserved for three weeks without the appearance of rope.3) In the inoculated groups of molds, Aspergillus niger and Penicillium expansum which were allowed to grow in the sponge cake and bread which treated with 0.25% propionic acid, but Mucor sp. was not allowed to grow on it.