Determination of quinalphos in human whole blood samples by high-performance thin-layer chromatography for forensic applications.

A simple and rapid procedure for the determination of quinalphos in human whole blood using liquid-liquid extraction and high-performance thin-layer chromatography was developed and validated. Seven different organic solvents were tested for optimum extraction of quinalphos from spiked blood samples. The effect of pH on the extraction yield of quinalphos was also examined. An average recovery of 93.61% was achieved from diethyl ether solvent at pH 3. Chromatographic separation was performed on silica gel 60F254 plates using mobile phase n-hexane-acetone in the ration 9:1 (v/v). Densitometric detection was carried out at 325 nm in absorbance mode. The interference of other organophosphorus pesticides of forensic relevance was not observed. The linear regression analysis in spiked whole blood samples resulted in linear calibration plot in the range 1 to 100 µg mL-1 with r2 = 0.9981. Sensitivity was represented by LLOQ at 1 µg mL-1. The within-day precision and between-day precision ranged from 0.18 to 1.04%, and 0.14 to 0.79% with an overall average recovery of 91.06% at three concentrations 1, 10, and 50 µg mL-1. No significant decrease in the concentration of quinalphos was observed for samples under different storage conditions. Finally, the developed procedure was applied to postmortem blood samples obtained in three fatal cases of poisoning by quinalphos.

HPTLC method for the assay of thiopental in post-mortem blood in a fatal case of suicide.

Thiopental is an ultra-short-acting barbiturate, used as an induction agent during general anesthesia and to manage intra cranial pressure in traumatic brain injuries. Because of its rapid onset of action, the potential for accidental or intentional abuse of thiopental is high. In this paper, a case is presented in which a 25-year-old female deliberately injected a fatal dose of thiopental. A method is developed for the evaluation of thiopental levels in the post-mortem blood (PMB) by simple and rapid HPTLC. Three different extraction procedures were compared for optimum recovery of thiopental from spiked blood samples. The effect of pH on the extraction yield of thiopental over a pH range of 5-6.5 was examined. An average analytical recovery of 90.5% was achieved from an ethyl acetate extract at pH 5.5. Chromatographic separation was achieved on silica gel 60F254 plates with an optimized mobile phase consisted of hexane-dichloromethane-ethyl acetate in the ratio 7.5:2:0.5 (v/v). Densitometric detection was carried out at 290nm in absorbance mode. No significant chromatographic interference was observed from other drugs used to diagnose the brain death. Calibration curve for thiopental in blood were linear from 1 to 100µgml(-1) with r(2)=0.994. The detection limit was 0.5µgml(-1) and its lower limit of quantification was 1.5µgml(-1). The method showed excellent intra-assay precision (R.S.D. 1.07-6.28%) and inter-assay precision (R.S.D. 0.39-1.43%) for spiked blood samples at concentration of 1, 10, and 50µgml(-1). The toxicological analysis revealed high concentrations of thiopental in PMB (204.75µgml(-1) ±0.34), which is of immense help to conclude that the death occurred due to fatal doses of thiopental.