Polychlorinated biphenyls, PCBs have been classified as dangerous substances to the environment due to their toxicity and bioaccumulation, and are unfortunately found in the environment worldwide. Effective extractions are needed to test for PCBs in the environment. Traditional techniques for extraction of environmental solids, sediments, sludges and other matrices consume large amounts of solvent and have long extraction times. Microwave assisted extraction of PCBs per US EPA method 3546, provides a rapid, reproducible method without the high solvent consumption.
Milestone’s Ethos EX microwave extraction labstation can extract 24 samples simultaneously in a closed vessel system. With increased pressure capabilities, temperatures above the boiling point of the solvent are used to decrease the extraction time to 30 minutes with 30 mL of solvent per sample. The closed vessel system along with magnetic stirring for constant agitation, direct temperature monitoring and the ability to reuse stored methods, allows for great reproducibility of PCB recoveries from environmental samples.
|Figure I. Ethos EX complete with PRO-24 Rotor for microwave extraction are comparable to or better than recoveries with soxhlet extraction.|
Extraction rates with Milestone’s Ethos EX microwave extraction labstation are 14 times faster, with recoveries comparable or better than traditional soxhlet extraction, and 500% reduction in solvent required. The ability to perform 24 samples simultaneously is ideal for high throughput labs looking to save space, time, and money while getting great recoveries of PCBs from environmental samples.
Microwave assisted extraction using the Ethos EX was compared to soxhlet extraction for PCB extraction from sediments. For the Ethos EX, 3 grams of sediment was weighed into a microwave vessel with 1.5 g of diatomaceous earth (a drying agent). A stir bar and 30-mL of 1:1 hexane: acetone mixture was added and the vessel. Extractions were completed at 120°C with a total program time of 30 minutes. For soxhlet, 5 g of sediment was extracted with 150-mL 1:1 hexane: acetone mixture with a total extraction time of 7 hours. Both extracts were analyzed by GC-ECD, and calibration was done by internal standardization with PCB 155.
|Figure 2. A simple microwave program for the Ethos EX extractions of PCBs from environmental samples makes operation easy for all laboratory personnel.|
|Table I. GC spiked recovery results of PCB extractions from both microwave assisted extraction and soxhlet extraction. Recoveries|
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