Extraction of PCBs and PCDD/Fs from Food and Feed Matrices Using Pressurised Liquid Extraction (PLE)

Since the Belgian dioxin crisis in 1999 there has been a great demand for fast, cheap and reliable methods to analyse food and feed samples. Traditional methods use large amounts of solvent for the extraction, are time demanding and laborious, but new and more sophisticated methods have been developed in recent years. Among these new techniques, pressurised liquid extraction (PLE) is a good alternative to classical techniques. In this thesis a non-selective PLE method was developed for the extraction of PCBs from feed samples using the ASE 200 instrument. Using the larger ASE 300 instrument a method for selective extraction of polychlorinated biphenyls (PCBs) from fat containing food and feed samples was developed. In this selective PLE method, silica impregnated with concentrated H2SO4 (40 %, w/w), was incorporated into the extraction cell. First the required fat/fat retainer ratio (FFR) was investigated for the 34 ml cells, as well as temperature, extraction solvents and flush volume. The larger cells (100 ml) were tested for extracting high fat containing samples and it was discovered that when using 100 ml cells the FFR only needed to be 0.050 whereas in the 34 ml cells a FFR of 0.025 was needed. The method using the 100 ml cells was successfully used for extracting polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin like PCBs from several food and feed matrices.

A new shape selective extraction and clean-up procedure was additionally developed. By using special designed inserts, it was possible to incorporate a carbon column into the PLE cells and thereby eliminate the traditional carbon column fractionation.

Both developed methods drastically reduces the overall time needed measuring PCDD/Fs and PCBs in food an feed matrices, as well as lowering the solvent consumption and minimising the manual work need for the extraction, clean-up and fractionation.