Determination of individual carbon chain homologue groups of polychlorinated alkanes in lipid-rich samples by gas chromatography with high-resolution mass spectrometry

Chlorinated paraffins (CPs) are mainly comprised of polychlorinated alkanes (PCAs) and widely used in industrial and commercial purposes, such as flame retardants, plasticisers and high temperature lubricants for metallurgy. Analysis of PCAs remains a challenge in complex biological samples. A robust and sensitive analysis method was presently developed for quantitation of individual carbon chain homologue groups of C₉ to C₂₀ PCAs in lipid-rich samples based on gas chromatography (GC) with high-resolution mass spectrometry (HRMS). Samples were extracted and then subjected to a freeze removal step where > 95 % of lipid was removed. This was followed by a sulfuric acid silica gel/silica gel multilayer SPE cartridge clean-up and then subjected to GC with Orbitrap HRMS operated in negative ion chemical ionization (NCI). A deconvolution and quantification procedure was generated for the data analysis process using a program in R language. Matrix effects (ME) showed an enhancement effect for PCA quantitative analyses by GC but was rectified by using olive oil as an analyte protectant. Method limits of quantification for PCAs in the test samples ranged from 1.1 to 17.5 ng/g. Mean recoveries of C₀₉Cl_X to C₂₀Cl_X homologues ranged from 56 to 120 % and 79 to 160 % in 50 ng/g and 10 ng/g fortified sunflower oil, respectively, and with relative standard deviations < 11 % and < 19 %, respectively. Reliable method applicability was demonstrated as homologue groups C₀₉Cl_X to C₁₈Cl_X were detectable whereas C₁₉Cl_X and C₂₀Cl_X were not in all polar bear adipose test samples and with ΣPCA concentrations up to 48.2 ng/g.