Study on the determination of heavy water in plasma or urine.

EBAL PROCEDURES are available for determination of deuterium in water by mass spectrometry. In the method of Solomon (1), water and deuterium oxide are reduced with hot zinc, and lative concentrations of deuterium and hydrogen are measured. ber of investigators have utilized this procedure in precise and ive studies (2-5). Other indirect methods were mentioned by burn et at. (6) in a study in which direct determination of the ratio was facilitated by establishing that spurious m/e 19 ion tion can be minimized with the use of a mass spectrometer of le design, and by a procedure in which unknown samples were ared with known ones having nearly the same deuterium oxide ntration. These investigators (6) also mentioned that vapor pure solutions of deuteriuni oxide in water could be used, but it re conventional to use liquid samples introduced through a merorifice with a small capillary dipper. e purpose of the present paper is to describe technics developed is laboratory to determine excesses of deuterium oxide in urine asma by measuring the 19:18 ratio in vapor samples obtained these fluids. Our procedure embodied principles established revious investigators (6), followed a pattern familiar in clinical tories, avoided the need for preparing water samples from or plasma, and minimized the unavoidable delay caused by the ory effect.t* Although we used a Pyrex inlet system, we found