DETERMINATION OF FATTY-ACIDS USING SOLID-PHASE MICROEXTRACTION

Solid-phase microextraction (SPME) is a simple, fast, economic, and solvent-free sample preparation method, The sensitivity of this technique for the determination of fatty acids in water can be enhanced with the addition of strong acid and salt to the aqueous phase, Under the low-pH and saturated salt conditions, SPME combined with GC-FID can analyze less polar acids (C-6-C-10) containing relatively long hydrocarbon chains directly from aqueous samples with ppt detection limits, The RSD of the method was 15% for all compounds tested. Under the same conditions 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, the detection limits can be lowered with in situ derivatization of these acids directly in the SPME polymeric coating doped with a derivatizing reagent. Headspace SPME/derivatization has been investigated, and the target analytes can be quantified with GC/MS by comparing the ratio of the native analytes with that of spiked isotopically labeled analogues. For air analysis, quantitative derivatization of short-chain fatty acids has been achieved. SPME without derivatization was also used to extract C-3 and C-4 acids from air samples, demonstrating the potential of SPME to monitor very polar, relatively volatile acids in air.