268 



MERCURY 



Intake Levels. Nearly all foods contain about 0.005 to 0.05 ppm mer- 

 cury. The daily intake by man is of the order of 0.02 mg. Human 

 glandular tissues range from 0.01 to 0.13 ppm on the fresh basis, whereas 

 others contain 0.001 to 0.01 ppm. About 50 mg/kg of mercuric chloride 

 given orally is fatal to rats. A biologic interest in this element, besides 

 its toxicity, is the use of organic mercurial drugs, particularly for diuresis. 



Radioassay. Hg^^^ exists in two isomeric states; thus the two half- 

 lives. Preparation Hg-203-P appears to be the one of choice, and soft- 

 beta counting or gamma counting will be required. An advantage of 

 the latter will be the elimination of sample preparation and self-absorption 

 problems. 



Chemistry. Routine wet-ashing, dry-ashing, or even heating of certain 

 organic mercury compounds may lead to volatilization losses. A method 

 described for estimation of mercury in biological material is as follows 

 (Hg-l) : The sample is digested in a special apparatus by boiling with H2SO4 

 and HNO3, followed by addition of permanganate and a second boiling. 

 Mercury is extracted from the digest with a chloroform solution of di-|S- 

 naphthylthiocarbazone which is then treated with a sulfuric acid-sodium 

 thiosulf ate mixture to separate the mercury from copper. The mercury is 

 extracted from the copper-free aqueous phase with a chloroform solution 

 of di-/3-naphthylthiocarbazone which is used for colorimetric evaluation. 



Typical Methods. Measurements of Hg^"^ were made on water, 

 plasma, and urine to which the radioisotope had been added and also on 

 serum, plasma, urine, and ascitic fluid from subjects who had previously 

 been injected (Hg-2). Either 0.25 or 0.30 ml of the fluid was delivered 

 onto a filter-paper disk by means of a micropipette. The preparation 



