RAPID ISOLATION OF POLYCHLORINATED-BIPHENYLS FROM MILK BY A COMBINATION OF SUPERCRITICAL-FLUID EXTRACTION AND SUPERCRITICAL-FLUID CHROMATOGRAPHY

The extraction and isolation of polychlorinated biphenyls (PCBs) from sample matrices such as freeze-dried milk is a lengthy and expensive p rocess that conventionally requires the isolation of microgram amounts of PCBs from large volumes of flammable organic solvents used in the extraction and chromatographic stages. Supercritical-fluid extraction (SFE) and chromatography (SFC) using carbon dioxide has been investiga ted as a replacement procedure using a Simplex optimisation approach t o optimise the working conditions. The SFE conditions required to extr act PCBs and milk fat from freeze-dried milk were investigated, and it was found that although extraction was rapid (10 min), the conditions required were identical so that there was no separation of PCBs and f at. However, SFC conditions have been developed that permit the resolu tion of PCBs from milk fat in 15 min. Thus, a combination of SFE and S FC have the potential to replace the existing methods of extraction an d isolation with procedures that are quicker, cheaper, and avoid the u se of flammable organic solvents.