Liquid/solid extraction on diatomaceous earth for drug analysis in postmortem blood.

Absorption extraction on diatomaceous earth was examined and found to be compatible with typical postmortem blood specimens encountered in forensic toxicology. The effects of solvent, solvent volume, eluate flow rate, and pH on drug recovery and extract quality were investigated. It was concluded that the best method was not necessarily that with the highest recoveries, but that considerations of extract quality were also required. The optimized method was compared with a single-step liquid/liquid extraction method and found to be superior in terms of ease of operation, extract quality, and absolute recovery. The results indicated also that although useful for screening, quantitative methods using liquid/solid extraction may be prone to error.