Optimization of solid-phase microextraction of volatile phenols in water by a polyaniline-coated Pt-fiber using experimental design.

Solid-phase microextraction (SPME) coupled to gas chromatography (GC) was applied to the extraction of phenol and some of its volatile derivatives in water samples. The SPME fiber consisted of a thin layer of polyaniline, which was electrochemically coated on a fine Pt wire. The stability of the coating was such that it could be used at temperatures as high as 325 degrees C, without any deterioration. The effects of various parameters affecting the extraction efficiency were studied, simultaneously. From these, optimization of the extraction temperature, extraction time, coating thickness, sample pH, salt concentration and desorption time was carried out by means of a (2(6-2)) fractional factorial design. It was found that the effects and interactions of five out of six factors were significant. However, the coating thickness showed a large main effect but an insignificant interaction effect, so it was kept constant. Also, the effect of desorption time was insignificant if sufficient time was allowed for desorption to take place. Therefore, a central composite design (CCD) with four remaining factors, i.e., sample pH, salt concentration, extraction time and sample temperature was performed and a response surface equation was derived. The statistical parameters of the derived model were r=0.97 and F=25.3. The optimum conditions were obtained using a grid method. Using the optimum conditions, the method was analytically evaluated. The detection limit, relative standard deviation, linear range and recovery were 1.3-12.8 ng mL(-1), 2.2-5.3%, 0.01-5.0 microg mL(-1), and 88-103%, respectively. The results showed the suitability of polyaniline-coated fiber in analyzing volatile phenolic compounds in water samples.