PH04 Advances in Analysis and Measurements
Exhibit Hall
8:00 AM - Thursday
(PH012) Increasing extraction efficiency of organic contaminants from solid substrates using freeze drying: a case study.
Salata, G.1, Coronado, J.1, Poyfair, T.1, Degner, C.1, 1 Columbia Analytical Services, Kelso, WA, USA
ABSTRACT- The accurate identification of organic contamination in any environmental matrix is dependent on the ability to efficiently extract contaminants from a particular substrate. In many cases, the most efficient extraction solvents for organic contaminants are non-polar. The extraction efficiency of organic contaminants from a variety of environmental matrices, including soil, sediment, sludge, and tissue, is therefore directly dependent on the removal of water from the sample matrix prior to extraction. Traditional drying techniques such as mixing the substrate with sodium sulfate can generate excess heat, potentially degrading and/or volatilizing low molecular weight target analytes. Alternatively, the use of diatomaceous earth (Celite®, Hydromatrix®, etc.) to bind water in a matrix eliminates problems associated with heat generation, but can significantly increase the volume of a sample with low solids significantly, limiting the amount of substrate that can be placed in a single extraction vessel. An alternative to these methods is water removal by freeze drying which, when properly used, has been shown to efficiently remove water from frozen sample matrices by sublimation without significant loss of target analytes. The study presented here compares the extraction efficiency of freeze drying with that of sodium sulfate drying for analysis of Chlorinated Pesticides, PCBs, Organotins, Semivolatile Organics, and Polycyclic Aromatic Hydrocarbons. The study shows that extraction of freeze dried samples consistently yields higher recoveries of analytes when compared with analytical results for chemically dried sediments. Because freeze drying also allows for larger amounts of a given substrate to be extracted without increasing the size of the extraction vessel, the higher extraction efficiency may allow for lower detection limits for these analytes to be achieved using traditional laboratory extraction techniques.
Key words: extraction, freeze drying, contaminant, sample preparation