A new accurate direct colorimetric method by p-dimethyl-aminobenzaldehyde (DAB) for determining the concentration of urinary hippuric acid and methylhipp-uric acids as indices of toluene or xylenes exposure was devised by us. To 0.02 ml of urine containing hippuric acid, 2.0 ml of 0.4% DAB solution in pyridine and 1.0 ml of acetic anhydride were added, and the solution was kept at 30°C for 1 hr. after thoroughly mixing. Then, the absorbance was determined at 460 nm. against a blank solution containing acetic anhydride, DAB and pyridine and water instead of urine. This direct and sensitive colorimetric method for the determination of hippuric acid in urine is applicable to the concentrations under at least 2.0 mg/ml of water or urine according to Beer-Lowbert law. The variation coefficient in the determination of hippuric acid by this method was small ranging from 1.3 to 2.7%, and the recovery was between 100.5 and 104.8% when a urine sample contained about 1.0-2.0 mg hippuric acid per ml of the urine. In the present paper, moreover, normal value of urinary hippuric acid determined by this method is described. As on application of this new method, urinary hippuric acid and methylhippuric acids in the urine of six workers in shipbuilding yard, who used paint thinner containing both toluene and m-xylene, were determined.
Dimethyl sulfoxide (DMSO) and its metabolite, dimethyl sulfone (DMSO2), ex-creted in the urine of rat were determined quantitatively after administration of DMSO using gas chromatograph equipped with a flame photometric detector (FPD). The results obtained were as follows: 1) DMSO and DMSO2 were well separated using the column packed with 5% polyethylene glycol (20M) on Shimalite W (60-80 mesh). 2) Very small amount of DMSO and DMSO2 could be determined by using gas chromatograph equipped with FPD by which analytical sensitivity of sulphur com-pounds had increased compared with a flame ionization detector (FID) because of its specific response. 3) The rats treated with intraperitoneal injection of 0.55g/kg DMSO excreted 75.21% of DMSO and 13.64% of DMSO2 in the urine during 8 days.
The outputs of inorganic arsenic compound (As+3, As+5), monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) in the urine were observed with passage of time after oral intake of arsenic trioxide. The subject was completely restricted from the ingestion of seafoods for two days before the experiment and during the urine sampling period, because of high arsenic content of these foods. As+3 was excreted in large amounts during the first 12 hours, the outputs corres-ponding to about 12% of the ingested amount, and the outputs of As+3 also were greater than those of MMAA and DMAA during the same period. The urinary outputs of arsenic compounds as total arsenic following the ingestion of arsenic trioxide amounted to 40% of the ingested amount during the first 12 hours, and 70% by 72 hours. Under restricted ingestion of seafoods, if the ratios of arsenite to total arsenic increase in the urine of arsenic workers, it is of importance as suggesting an increased absorption of toxic arsenite.
A mechanical low pass filter (LPF) was applied to between the human hands and a portable vibrating tool of a grinder, that is, the tool was separated from the hand by the isolator (LPF) for the purpose of protection of the hands. Equiv-alent electric circuits were used for analysis of the mechanical system in which the mechanical impedances of the tool, of the isolator and of the human hand were simulated by mass-capacitance correspondence. The good effectiveness on this type of the vibration isolation was proved in acceleration measurements in three directions of X, Y and Z. The model being commercially available was also developed using knowledge of the results.
Effectiveness of vibration isolation was examined on a commercially availableisolator made of Nighthart system which was applied to a rock-drill of leg-type. As the effectiveness was not so high, these handles were tried to improve by chang-ing their mechanical parameters. The vibration characteristic on them was ob-served on the vibration table and their results were explained mathematically. Thus, the isolators more or newly tentatively made were also tested on the vibration table and practically on the rock-drill. Besides, the method of mea-surement for effectiveness of the isolator was studied at the same time, namely, on spectrum difference, on attenuation measurement on the vibration table and on vibration level measured with a vibration level meter for portable vibrating tools (JIS-C-1511).