Automated sample preparation and GC-API-MS/MS as powerful tool for analysis of legacy POPs in human serum and plasma

An automated high-throughput solid phase extraction method for selected persistent organic pollutants (POPs) as 17 organochlorine pesticides, 22 polychlorinated biphenyls (PCBs), 9 polybrominated diphenylethers (PBDEs) and octachlorostyrene (OCS), in human serum and plasma was developed. Importance was attached to application of small volumes of reagents and solvents in addition to low sample volumes (150 µL) in order to save the highly valuable sample material for follow-up and other studies. Instrumental analysis was performed by gas chromatography with atmospheric pressure ionisation coupled to tandem mass spectrometry (GC-API-MS/MS). The recoveries of the selected analytes were satisfactory and between 70% and 120% for most of the compounds at three investigated spike concentrations (75 pg/mL, 450 pg/mL and 1250 pg/mL). Inter-day recoveries for pesticides were within 80-120% and for PCBs and PBDEs within 86 – 130% with RSDs ranging from 2% to 35%. The accuracy of the method was evaluated with standard reference materials and samples from the ringtest of the Arctic Monitoring and Assessment Program and was slightly better with lower RSDs for most of the compounds compared to previous published methods. Method detection limits (MDLs) ranged from 0.009 pg/mL to 34.6 pg/mL for pesticides, from 0.435 pg/mL to 57.8 pg/mL for PCBs and from 0.855 pg/mL to 34.6 pg/mL for PBDEs when blank contamination was taken into account. Low MDLs together with high accuracy, repeatability and robustness were demonstrated for an appropriate concentration range. The applicability for real samples was satisfactory demonstrated by analysis of 40 serum samples from the general population from Tromso, Norway, where in total 33 analytes were measured above the MDL. The most important marker compounds are detected in this low exposure population which shows the suitability of the presented method for retrospective as well as prospective studies with high number of samples.