PARENT SESSION
3A Advances in environmental analytical chemistry
9:00 AM to 7:00 PM, Tuesday, 08 May 2001

(T/EH096) PRESSURISED LIQUID EXTRACTION OF POLYCHLORINATED BIPHENYLS FROM BIOTA SAMPLES.

Gómez-Ariza, José Luis¹, Bujalance, Manuel¹, Gallego, Mercedes¹, Velasco, Alfredo¹, Sánchez-Rodas, Daniel¹, Giráldez, Inmaculada ¹, ¹

ABSTRACT- PCBs are an important environmental problem due to the large anthropogenic inputs into the environment. The determination of PCBs in various complex matrices is mandatory for environmental monitoring, and consists of many steps: sample homogenisation, extraction, clean-up, preconcentration, and separation by a HRGC using ECD or MS detection. In these studies the more time consuming step is often the extraction, mainly when a "traditional method" is used (Soxhlet,shake-flask method,sonication). Other new methods, namely supercritical fluid extraction (SFE), microwave assisted extraction (MAE) and pressurised fluid extraction (PFE), are not only faster but reduce the use of hazardous organic solvents. PFE uses conventional liquid solvents at elevated temperatures (50-200oC) under a high pressure (500-2000 psi) to extract solid samples quickly and with small solvent volumes (10-50 ml). The sample is enclosed in a high-pressure stainless-steel cell and, after an initial heating step, is allowed to interact statically with the solvent during a time period, and then is purged from the cell by a nitrogen stream into a collection vial. Most of applications of PFE have considered sediments and soils as environmental samples. In this study, we evaluate the use of PFE to extract PCBs from eggs of spoonbill, mussels, oysters and clams. The variables of temperature, pressure, static extraction time, matrix dispersing agent, polarity and volume of solvent and number of extraction cycles were optimized for recovery of PCBs from samples, and results were compared to those obtained by using Soxhlet extraction. The most influencing parameters were temperature and dispersing agent, and both quantitative recoveries and reproducible results (RSD between 5.1-11.6 %) were obtained under optimized conditions (1:2 sample-Celaton, 50 ml pentane, 175oC, 2000 psi, 15 min static extraction, 2 cycles) using native and spiked samples. The extracts obtained were cleaned up through a Florisil column and the fraction consisting of PCBs was analyzed by gas chromatography and an ion trap mass spectrometer operated in the electron ionisation mode and using the tandem mass spectrometry (MS/MS) option.

Key words: PCBs, PFE, MS/MS, biota