Sample pretreatment optimization for the analysis of short chain chlorinated paraffins in soil with gas chromatography–electron capture negative ion-mass spectrometry

Accurately quantifying short chain chlorinated paraffins (SCCPs) in soil samples with gas chromatograph coupled with electron capture negative ionization mass spectrometry (GC–ECNI-MS) is difficult because many other polychlorinated pollutants are present in the sample matrices. These pollutants (e.g., polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and toxaphene) can cause serious interferences during SCCPs analysis with GC–MS. Four main columns packed with different adsorbents, including silica gel, Florisil and alumina, were investigated in this study to determine their performance for separating interfering pollutants from SCCPs. These experimental results suggest that the optimum cleanup procedure uses a silica gel column and a multilayer silica gel–Florisil composite column. This procedure completely separated 22 PCB congeners, 23 OCPs and three toxaphene congeners from SCCPs. However, p,p′-DDD, cis-nonachlor and o,p′-DDD were not completely removed and only 53% of the total toxaphene was removed. This optimized method was successfully and effectively applied for removing interfering pollutants from real soil samples. SCCPs in 17 soil samples from different land use areas within a suburban region were analyzed with the established method. The concentrations of SCCPs in these samples were between 7 and 541 ng g−1 (mean: 84 ng g−1). Similar homologue SCCPs patterns were observed between the soil samples collected from different land use areas. In addition, lower chlorinated (Cl6/7) C10- and C11- SCCPs were the dominant congeners.