CALIBRATION OF A COMMERCIAL SOLID-PHASE MICROEXTRACTION DEVICE FOR MEASURING HEADSPACE CONCENTRATIONS OF ORGANIC VOLATILES

Solid-phase microextraction (SPME) is a versatile new technique for co llecting headspace volatiles prior to GC analysis. The commercial avai lability of uniform SPME fibers makes routine, practical quantitation of headspace concentrations possible, but straightforward information for relating GC peak areas from SPME analyses to headspace concentrati ons has not been available. The calibration factors (amount absorbed b y the fiber divided by headspace concentration) were determined for 71 compounds using SPME fibers with a 100 mu m poly(dimethylsiloxane) co ating, The compounds ranged from 1 to 16 carbons in size and included a variety of functional groups. Calibration factors varied widely, bei ng 7000 times higher for tetradecane than for acetaldehyde, Most compo unds with. a Kovats retention index of <1300 on a nonpolar GC column ( DB-1) equilibrated with the fiber in 30 min or less, A regression mode l is presented for predicting the calibration factor from GC retention index, temperature, sued analyte functional class, The calibration fa ctor increased with retention index but decreased with increasing samp ling temperature, For a given retention index, polar compounds such as amines and alcohols were absorbed by the fibers in greater amounts th an were hydrocarbons, Henry's law constants determined using SPME were in general agreement with literature values, which supported the accu racy of the measured calibration factors, An unexpected concentration dependence of calibration factors was noted, especially for nitrogen-c ontaining and hydroxy compounds; calibration factors were relatively h igher (the SPME fiber was more sensitive) at the lower analyte concent rations.