Optimization and validation of a procedure for the determination of total chromium in postmortem material by ETAAS

A study was conducted to optimize and validate a procedure for the determination of total chromium in wet digested samples of human blood and body tissues for forensic toxicological purposes. Five experimental setups of electrothermal atomic absorption spectrometry (ETAAS) using a Solaar MQZe (Thermo Electron Co.) were compared, using the following: (i) no modifier, (ii) magnesium nitrate, (iii) palladium nitrate, (iv) magnesium and palladium nitrate mixture and (v) palladium nitrate and ammonium dihydrogen phosphate mixture as chemical modifiers. Furthermore, for the mineralization process in the Ethos 1 microwave system (Milestone), it was found that the temperature program suggested by the producer should be improved, thus, four experimental setups are presented. Finally, the whole procedure was validated, obtaining a linear range of calibration from 0.22 to 12.0 µg/L, limit of detection at 0.07 µg/L, limit of quantification at 0.22 µg/L, precision (as relative standard deviation) up to 6%, and accuracy of 98.4-104.4% for the analysis of certified material (ClinChek Whole Blood Control Level III, SRM Whole Blood Level II and III and SRM 1577c Bovine Liver) and within a range from 84.5 to 103.2% for the recovery of spiked samples. It was ascertained that modified wet digestion, followed by ETAAS with magnesium nitrate as a modifier (5 µg) with 1,400/2,500°C as the pyrolysis and atomization temperatures, respectively, can be used to determine chromium at reference levels in biological materials (blood and internal organs) and levels found in chronic or acute poisonings with chromium compounds.