Quantitative analysis of phosphine in variety of biological samples from two cases of fatal poisoning

Abstract

To highlight the importance of confirmation and quantitation of phosphine in variety of biological specimens using gas chromatography coupled with nitrogen phosphorus detector. Phosphine, a highly poisonous gas is liberated when aluminium or zinc phosphide come in contact with acid. These phosphides are commonly encountered in poisoning cases received in the author's laboratory. After reaction of phosphide with acid in the stomach, the formed gas is rapidly absorbed into blood from where it is distributed through out the body. Therefore, it is important to test multiple specimens for confirmation and quantitation of phosphine because of its rapid distribution throughout the body. Case 1. A 22-year-old male was allegedly poisoned due to conflict over money. He was taken to nearby hospital but he could not survive and died within three hours of incident. There was no significant finding in postmortem report. Stomach contents and liver were processed for toxicological analysis. Case 2. A 23-year-old female attempted suicide by ingesting poisonous pills due to marital conflicts. She was brought to hospital where she got treatment accordingly. Her blood, urine and gastric lavage samples were submitted to author's laboratory for identification of poison. Presumptive testing of phosphine using silver nitrate strips was performed on stomach contents in case 1 and gastric lavage in case 2. Confirmation and quantitation for phosphine was performed on Gas Chromatography-Nitrogen phosphorous detector with PLOT column. Specimens from both cases (10 mL) were taken in headspace vial. Small amount of Zinc dust was added along with 2 mL of 6 N sulphuric acid. Vials were then crimped and heated at 70 °C in oven for 30 minutes. 0.5 mL sample from headspace was then manually injected in GC-NPD. Total run time of the method is 2 min. Calibrators (10–500 ng/mL) were prepared by serial dilution and run concurrently in order to estimate the concentration of phosphine in submitted samples. All analyzed specimens from both cases were found positive for phosphine. Stomach contents and liver from case 1 contained 264 and 30 ng/mL phosphine respectively. Blood, urine and gastric lavage in case 2 were found to contain 21, 5 and 268 ng/mL phosphine respectively. Although manual injection may produce large variation in quantitation but it is still useful to get an estimate of phosphine concentration in biological samples. Detection of phosphine in stomach contents and gastric lavage in significant amount supports oral intake of phosphine by the victims. Furthermore, presence of phosphine in blood and liver indicates its systemic distribution while phosphine in urine demonstrates its excretion pathway. Phosphine is a deadly poison that should be analyzed at earliest because it has tendency to escape from biological specimens. This also emphasizes the availability of sensitive method for rapid identification of phosphine from multiple biological specimens.