ON THE SPECTRO-PHOTOMETRICAL DETERMINATION OF BENZENE IN BLOOD

The determination of benzene in blood is usually performed by the so-called Butanone method. However, this method is complicated in practice. This paper introduces a simple and convenient method applying ultraviolet absorption spectra of benzene. The determination methods of benzene in air and expired air were reported already in other paper. It is based on the following facts, that the benzene easily and immensely soluble in ethyl alcohol and this solution has many absorption maxima in ultraviolet regions such as at 2485 Å, 2545 Å, 2606 Å and others. The maximum absorption at 2545 Å is the greatest and the existence of a small amount of benzene in alcoholic solution is detected by measuring the absorption spectra with ultraviolet spectro-photometer. K.Hirasawa, one of the author's collaborators, reported the detection method of benzene in blood by Conway's micro-diffuser. The author developed this method as a quantitative determination. The apparatus is shown in Fig. 1. The sample tube is kept in thermoregulated water bath at 37 to 45°C. The absorbent tube containing 3 cc of pure alcohol is put in ice flask and cooled to 0°C. Those tubes are connected by a polyvinyl tube instead of using a rubber tube, because of avoiding the effect of rubber. Aerating the sample tube with hot air passing through a spiral glass tube kept in the bath. This promotes the separation of benzene from the blood sample. The benzene vapor is transfused to the absorbent tube which contains pure alcohol. The experimental results are followings. 1. 0.5 cc of blood is enough for a sample, if the content of benzene in blood is more than 0.03mg per 1 cc of blood. 2. For aeration, 600 to 1000 cc of fresh air is needed for above mentioned range. The aeration is carried out 3 to 5 min. in the velocity of 200 cc/min. 3. The recovery is almost complete at the benzene content less than 0.3mg per cc of blood, and if the amount of benzene is more than value, the recovery rate remains at 80%. 4. The limit of the determination lies between 0.0075mg to 0.3mg per cc of blood. In the case of the benzene is contained less than 0.03mg, two to four samples should be repeatedly aerated in the same absorber. 5. Experimental error is supposed mainly by an inadequate aeration, so three times repetitions are at least desirable for one sample.