US EPA

2070465 

Technical Report 

Determination of phosphides and white phosphorus in biological materials by neutron activation analysis 

Kirshman, SS; Gupta, RC 

1970 

HAPAB/71/00622 

Chem 

6 

HAPAB A method for the identification and quantitative determination of toxic phosphorus (such as zinc phosphide or white phosphorus) in lever or other biological materials using neutron activation analysis is described. The technique can be adapted to differentiate the phosphine from putrefaction in tissues, metal phosphides and white phosphorus. Ground tissue samples were washed and placed in a 250-ml flask. A stream of nitrogen was passed through the sample for 30 min. The mixture was acidified to 10% with sulfuric acid. The liberated phosphine was passed through a saturated solution of basic lead acetate maintained at 70 C to remove hydrogen sulfide and was abosrbed by glass wool, which had been soaked in methanolic silver nitrate and dried. The phosphine was oxidized to white silver phosphate by chlorine vapors. The silver phosphate was produced from the phosphorus in the tissue sample and not from neutral phosphate which does not distill as phosphine. The glass wool containing the silver phosphate was subjected to neutron activation analysis for the estimation of the phosphorus content. The amount of radioactivity from induced 32-P in the final precipitate was proportional to the phosphorus content in the sample. The glass wool and a weighed quantity of the phosphorus standard in a plastic vial were sealed in an aluminum irradiation capsule and irradiated in a nuclear reactor at a thermal flux of about 10 trillion neutrons/sq cm/sec for 12 hr. Radioactivity was determined by proportional counting. An ion-exhcnage method of radiochemical separation using a radioactive silver tracer precipitation method was found to be more efficient (100%) than the Mullins and Leddicotte (55 to 60%), which employed 32-P as a tracer (1962). Irradiated ammonium phosphate (32-P) in 3 M nitric acid was mixed with a large quantity of 110-silver tracer. The solution was passed through a cation exchange column and the column washed. The effluent was centrifuged. The precipitated magnesium ammonium phosphate was filtered, washed, dried and mounted for beta radioactivity measurement using a proportional counter. The results of tests using these procedures and different control tissues with known amounts of phosphorus showed that phosphorus in tissues could be identified and quantitatively determined to about 10 ng (plus/minus 10%). Therefore, this method can be useful and effective for medicolegal applications in detecting nanogram quantities of phosphorus in either small or large samples. 1970