Speciation analysis of mercury employing volatile species generation: Approaches to reliable determination in blood and hair
Abstract
Two approaches to Hg speciation analysis, both employing volatile species generation (VSG) were optimized and subsequently applied to biological sample analysis. The first one employs post-column VSG after HPLC separation of Hg species (Hg2+, MeHg+, EtHg+ and PhHg+) prior to their ICP-MS detection (HPLC-VSG-ICP-MS).
The optimized post-column VSG step enhances sensitivity 30-40 times and improves limits of detection (LOD) by a factor of five in comparison with the setup without VSG step (HPLC-ICP-MS). LODs between 3 and 6 ng L-1 have been reached by HPLC-VCG-ICP-MS while those reached by HPLC-ICP-MS ranged significantly higher (15-26 ng L-1).
Additionally, the VSG step reduces significantly the effect of organic mobile phase on ICP plasma during gradient elution required for PhHg+ determination. Moreover, a simple and short (7 min) two-stage extraction procedure was proposed for simultaneous determination of Hg2+, MeHg+ and EtHg+ in human blood.
Acceptable extraction efficiency of Hg species without their inter-conversions was confirmed by Hg speciation analysis in human blood certified reference materials (Seronorm Trace Elements Whole Blood L-1 and L-2) resulting in recoveries better than 90% (Hg2+, MeHg+) and 80% for EtHg+, respectively. The second approach to Hg speciation analysis is based on selective extraction of MeHg+ from hair samples with 2 mol L (-1) HCl.
Extraction selectivity was verified by HPLC-ICP-MS employing the IAEA-086 certified reference material of human hair. Three spectrometric detectors were compared for subsequent Hg determination in the extracts from hair including single purpose mercury analyzer AMA-254, VSG-AAS and ICP-MS resulting in MeHg+ recovery of 100 +/- 10%.