Screening for chlorinated paraffins in vegetable oils and oil-based dietary supplements by planar solid phase extraction

Abstract

Extraction of chlorinated paraffins (CPs) in samples with high fat content is generally performed by a sulfuric acid treatment and liquid-liquid partitioning in n-hexane, followed by clean-up by column chromatography. Analysis and quantitation are commonly carried out via gas chromatography coupled with electron capture negative ionization mass spectrometry (GC/ECNI-MS) when low- and high-resolution MS (LRMS and HRMS) are used. In this work, we present a completely different and innovative approach for the determination of CPs by applying the planar solid phase extraction (pSPE) concept for a rapid and selective screening. pSPE offers the concentration of the analytes in a single target zone followed by the densitometric determination of the total CP content. After sulfuric acid treatment and liquid-liquid partition into n-hexane, pSPE was performed on silica gel plates employing a twofold development with cyclohexane/toluene (94:6, v/v) and methylene chloride/n-hexane (9:1, v/v) as mobile phases. CPs were quantified via the visual (VIS) absorption of the target zone after derivatization with o-tolidine, and amounts were calculated as the sum by means of a reference CP. Limits of detection and quantitation for the reference CP were 0.2 and 0.7 mg/kg oil, respectively, and recoveries from different vegetable oils were near 100%. The analysis of total CPs in dietary supplement samples by pSPE-VIS compared to GC/ECNI-HRMS proved the method as a reliable and suitable screening tool providing an appropriate alternative to existing time-consuming and complex methods.

Keywords: Chlorinated paraffins (CPs); Dietary supplements; High-performance thin-layer chromatography (HPTLC); Planar solid phase extraction (pSPE); Screening; Vegetable oils.