General unknown screening in postmortem tissue and blood samples: a semi-automatic solid-phase extraction using polystyrene resins followed by liquid-liquid extraction.

The identification of general unknown poisons in complex biological materials like postmortem blood and tissue is a great challenge for the forensic toxicologist. Therefore, a screening procedure utilizing a semi-automatic work-up with an ASPEC system was developed. A broad range of different compounds can be isolated by using non-selective and generally applicable organic polymeric sorbents such as OASIS HLB or Isolute 101. Because colloidal solutions were applied to these sorbents, the denaturation of proteins, which can result in an irreversible loss of significant compounds by adsorption and occlusion, could be avoided. Because of the process of micellar chromatography followed by liquid-liquid extraction of the crude extract, very clean fractions were obtained from such complex matrices as postmortem blood, liver, and brain samples. High recoveries (72-100%) and good day-to-day relative standard deviations (1-17%) could be achieved with both polymeric sorbents. The procedure paves the way for the identification of general unknown poisons in target organs and is therefore a useful tool in the field of forensic toxicology.