Improved analytical performance using semi-permeable membrane extraction of lipid rich matrix

Lipids are good matrices to accumulate many non-polar persistent organic pollutants (POPs) due to the lipophilic nature of these chemicals. Dairy products are easily accessible and available world-wide and analysis of this matrix supplies estimation of human food chain exposure and, at the same time, reflects the contamination level of the environmental compartment from which they derive.The Stockholm Conventions and the Global Monitoring Plan encourage the production of monitoring data to effectively evaluate the presence of the POPs in all regions, in order to identify changes in levels over time, as well as to provide information on their regional and global environmental transport. Often large sample amounts must be extracted to achieve sufficiently low detection limits of the priority POPs. Consequently, large amounts of lipids can be present in the extracts depending on the lipid content of the sample. The first step of analyzing lipid rich matrices is to extract the pollutants, preferably without extracting the lipids themselves. The presence of lipids, in the form of phospholipids, triglycerides and free fatty acids or cholesterol can disturb the chromatographic capabilities in the further clean up or fractionation steps, as well as suppresses the ionization at the chemical analysis. Dialysis with a semi permeable membrane (SPM) enables a non-destructive separation technique of the analytes from matrix, i.e. it efficiently extracts the smaller non-polar compounds, and retaining the larger compounds in animal or plant fat samples. The membranes are made from low-density polyethylene film with approximately 1-nm pores; and enables permeation of small (analyte) molecules whereas dialysis of molecules of matrix compounds larger than this is not possible. The aim of this study is to develop and evaluate an improved clean-up methodology for large volume lipid rich samples. 5 grams of lipids from butter has been extracted with SPM and with several different solvent compositions to identify the optimal conditions for POP analysis with sufficient recovery. The extract was further cleaned up with alumina (basic) and sulphuric acid SPE columns. The target compounds of this study are PCDD/Fs, PCBs, PBDEs, and OCPs subject to the Stockholm Convention as by 2009. Analyses are executed with high resolution GC/MS and quantifications will be carried out based on labeled surrogate standards.

WEISS Jana;  MARIANI Giulio;  UMLAUF Gunther; 

2011-08-29

SETAC Europe

JRC61921