Optimization of the SPME device design for field applications

Solid Phase Microextraction (SPME) is a powerful tool for field investigations. With the help of a portable gas chromatograph it can be used for fast analysis directly on-site, or it can be utilized for field sampling and then transported to the laboratory for instrumental analysis. In the latter case, it is important for the reliability of the results that losses of volatiles and contamination of the fiber during storage and transport are minimized. A number of dedicated devices, designed and built for SPME field sampling and storage, have been developed and tested. Sealing capacity of the prototypes was investigated by storing compounds ranging in volatility from methylene chloride to 1,3-dichlorobenzene on selected SPME fibers (100 mu m PDMS, 65 mu m PDMS/DVB and 75 mu m Carboxen/PDMS) at different temperatures. Significant differences were noticed in storage capacity from coating to coating. A comparison between the field samplers optimized in this study and the field sampler commercially available from Supelco revealed advantages and limitations of each of the designs. A gas-tight valve syringe (50 mu L SampleLock by Hamilton), modified in order to accommodate the SPME Fiber, had the best storage capacity for very volatile compounds. With this device, over 80% of the initial amount of methylene chloride was retained by the 100 mu m PDMS fiber after 24 h of refrigerated storage, which is a very good result considering that the PDMS coating is characterized by very low storage capacity for volatiles. Field sampling Investigations with the SPME prototypes confirmed the usefulness of these devices for field analysis.