Improved sample preparation method for selected persistent organochlorine pollutants in human serum using solid-phase disk extraction with gas chromatographic analysis

An improved solid-phase extraction (SPE) method was developed to isolate and concentrate trace levels of selected POPs (persistent organochlorine pollutants) in human serum prior to GC–MS in SIM mode or GC–ECD quantitation. The extraction involves denaturation of serum proteins with formic acid, SPE using C₁₈ Empore™ disk cartridges, followed by elimination of lipid interferences using a sulfuric acid wash of the eluate. Use of the SPE disk improved assay throughput and gave a cleaner analytical matrix compared with previously reported solid-phase and liquid–liquid extraction techniques. The extraction method provided consistent recoveries at three fortification levels using ¹³C₁₂ PCB 149 as internal standard. Recoveries ranged from 48 to 140% for organochlorine pesticides (6.25, 12.5 and 25 ng/ml) and 71 to 126% for polychlorinated biphenyls (0.625, 1.25 and 2.5 ng/ml).