Detection of phosphine in abdominal cavity material of woman dead body and ingesta of cow using Gas Chromatography-Nitrogen Phosphorous Detector technique (GC-NPD)

Abstract

Detection of phosphine (poison) in unusual specimens (i.e abdominal cavity material of putrefied woman body) as well as in Ingesta of a cow using GC-NPD. Introduction: aluminium and Zinc Phosphides are commonly used as insecticides and rodenticides respectively. In Pakistan, these poisons are major contributors for homicidal and suicidal deaths because it is cheap and easily available. Phosphine is a gas liberated from Aluminium and Zinc Phosphides, in a reaction with acid. We report two cases of phosphine detection in such complex matrices. Case 1. A decapitated putrefied body of a woman was found whose legs and arms were not present. Internal organs including heart, lungs and kidneys were also eaten by animals. Abdominal cavity material was sent for forensic toxicological analysis in author's laboratory. Chances for detection of phosphine gas were very low, as specimen was highly decomposed and putrefied. Case 2. A Cow was found dead in the house of owner with no previous history of any disease. Ingesta of the Cow was submitted to author's laboratory with no pathological information by the veterinary doctor. Ingesta is also considered as a very complex matrix for toxicological analysis. Presumptive testing of phosphine was performed on abdominal cavity material and Ingesta with silver nitrate strip using Conway micro diffusion cell colorimetric technique. Confirmation was performed on Gas Chromatography-Nitrogen phosphorous detector with PLOT column. 10 mL samples of both abdominal cavity material and Ingesta were taken in separate headspace vials. Small amount of Zinc dust was added along with 2 mL of 6N sulphuric acid. Vials were then crimped and heated at 70 °C in oven for 30 minutes. 0.5 mL sample from headspace was manually injected in GC-NPD. Phosphine was detected in abdominal cavity material of woman and ingesta of cow. Total run time of the method is only 2 minutes. Peak of the phosphine was observed at 1.2 min retention time. Although there was less probability of phosphine gas detection from these specimens however analysis was attempted and results were found positive for phosphine. There is very less data available for the detection of poisons on putrefied specimens. Detection of phosphine, in matrices like exhumed specimens, putrefied parts or Ingesta of animals is a bit-challenging task for Forensic Toxicologists due to its tendency to escape from decomposed samples. In such cases, analysis must be attempted for the provision of justice. Phosphine is a very small molecule, but it can still be detected in abdominal cavity material of a putrefied body and Ingesta. There is also a strong need to regularize the sale, availability and purchase of Aluminum or Zinc Phosphide.