The undetected murder? Evaluation and validation of a practicable and rapid inductively coupled plasma-mass spectrometry method for the detection of arsenic, lead, and thallium intoxications in postmortem blood.

Abstract

Homicide, suicide, or accident - elemental intoxication may be a cause in each of these types of deaths. Inductively coupled plasma mass spectrometry (ICP-MS) has emerged as the gold standard analytical method for toxic metal analysis in both clinical and forensic settings. An ICP-MS method was developed using a modified acidic workup for the quantitative determination of arsenic, lead, and thallium. Method validation focused on the assessment of linearity, between- and within-day precisions, limits of detection (LoD) and lower limits of quantification (LLoQ), and carryover. The method was applied to analysis of postmortem peripheral blood samples from 279 forensic cases for which orders for chemical-toxicological examination had been received from the public prosecutor's office. Using six-point and one-point calibrations (latter for rapid screening purposes), precisions and accuracies ranged from -4.8 to 5.8% and -6.4 to 7.5%. Analytical sensitivities for As, Pb, and Tl were 0.08, 0.18, and 0.01 μg/l (LoD) and 0.23, 0.66, and 0.03 μg/l (LLoQ), respectively. Observed postmortem peripheral blood concentrations were As, 1.31 ± 3.42 μg/L; Pb, 17.4 ± 13.1 μg/L; and Tl, 0.11 ± 0.07 μg/L (mean ± standard deviation [SD]). Elemental concentrations, determined in additional quality control samples, were in good agreement to those obtained with an external ICP-MS method based on alkaline sample processing. The current method is practicable and compatible with an ICP-MS system used for trace element analysis in an accredited medical laboratory. It allows for implementation of low-threshold investigations when metal intoxications are suspected in forensic routine.