Solid Phase Microextraction

For analysis of environmental samples, common goals include decreasing extraction and analysis times, reducing or eliminating organic solvent use, and developing field analysis and screening techniques. Headspace solid-phase microextraction (HS-SPME) can measure concentrations of more volatile contaminants with minimal or no sample pretreatment. Also, more freely available contaminants will be sampled giving information on bioavailability. HS-SPME has been used to sample PAHs from soil at an old gasworks site.198 PDMS-coated fibers were used to sample for 5 min and analysis had to be within two days. Calibration was done internally by standard addition and externally by spiking sand. Results comparable to those obtained by Soxhlet extraction were obtained for two- and three-ring PAHs. The method was only valuable as a screening tool for PAHs with four or more rings due to their lower vapor pressures. Certified soil samples (CRM-104) were analyzed by direct immersion or headspace SPME following equilibration with water using PDMS and PA fibers.199 Only FLA and PYR were at high enough concentrations in the headspace to be extracted at 25°C. A temperature of 80°C was necessary to volatilize enough of the five-ring PAHs for successful quantitation. Surfactant addition further enhanced the sensitivity of the method.

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