DETERMINATION OF FATTY-ACIDS USING SOLID-PHASE MICROEXTRACTION

Solid-phase microextraction (SPME) is a simple, fast, economic, and so lvent-free sample preparation method, The sensitivity of this techniqu e for the determination of fatty acids in water can be enhanced with t he addition of strong acid and salt to the aqueous phase, Under the lo w-pH and saturated salt conditions, SPME combined with GC-FID can anal yze less polar acids (C-6-C-10) containing relatively long hydrocarbon chains directly from aqueous samples with ppt detection limits, The R SD of the method was 15% for all compounds tested. Under the same cond itions as above, the detection limits of free short-chain fatty acids (C-2-C-4) in the aqueous samples are in the high ppb level, However, t he detection limits can be lowered with in situ derivatization of thes e acids directly in the SPME polymeric coating doped with a derivatizi ng reagent. Headspace SPME/derivatization has been investigated, and t he target analytes can be quantified with GC/MS by comparing the ratio of the native analytes with that of spiked isotopically labeled analo gues. For air analysis, quantitative derivatization of short-chain fat ty acids has been achieved. SPME without derivatization was also used to extract C-3 and C-4 acids from air samples, demonstrating the poten tial of SPME to monitor very polar, relatively volatile acids in air.