Microextraction of polychlorinated biphenyls (PCBS) from soil samples

The standard method of polychlorinated biphenyl (PCB) analysis in soil samples requires Soxhlet extraction of gram amount of sample, considerable amounts of hazardous solvents, and a clean-up and extraction time of 3 days per sample. An efficient microextraction procedure has been developed for the trace quantitative analysis of PCBs in soil samples that will only necessitate a small fraction of the Soxhlet extraction requirements ad still achieve good recoveries for PCB congeners. The microextrcation procedures requires only 0.1g amount of sample and is relatively inexpensive extraction technique, which can be completed within 18 hours. The technique uses standard glassware and only minimal amount of solvent. In this work, parameters such as the type and amount of extracting solvent were evaluated. The congener-specific recoveries of the 20 target PCBs were compared using hexane and heptane as extracting solvents. When compared to the certified concentrations of the 20 congeners in the soil standard reference material (SRM) from the National Institute of Standards and Technology (NIST), the proposed microextraction method using heptane showed excellent recoveries for 10 of the congeners. The other 10 target congeners were found with other PCB congeners or contaminants. Moreover, the recoveries of the 2 surrogate internal standards, PCB #30 and 112, were also within the acceptable limit of ±30% even at 25 ng/g