Development of an Analytical Procedure for the Determination of Trihalomethanes in Leafy Vegetable by Headspace-SPME Followed by GC-ECD Determination

An analytical procedure for the determination of trihalomethanes (i.e., CHCl3, CHBrCl2, CHBr2Cl, and CHBr3) in leafy vegetable matrices was developed consisting of headspace solid-phase microextraction (HS-SPME) followed by GC-electron capture detector (ECD) determination. Factors affecting the extraction yield were optimized by multivariate methods in two steps. First, a 2(5-1) fractional factorial design was applied to screen for and assess the effects and interactions of sample mass (g), extraction temperature (A degrees C), extraction time (min), the salting-out effect, and total volume (mL). Second, a response surface methodology design, i.e., central composite design, was applied to optimize the variables found to have a significant impact on the extraction process (extraction time, extraction temperature, and total sample volume), thereby making it possible to simulate the behavior of all the analytes except CHBr3. Finally, the multiple responses were simultaneously optimized using the desirability function. The optimum overall extraction conditions were achieved with an extraction time of 30 min, a temperature of 40 A degrees C, and a total volume of 5 mL. These analytical conditions were validated by spiking plant samples at two concentration levels (2 and 5 mg kg(-1)), which yielded accurate and precise results for the target analytes. Detection and quantitation limits ranged from 0.09 to 0.64 mu g kg(-1) and 0.14 to 0.97 mu g kg(-1), respectively. Finally, chloroform and bromoform were detected in lettuce irrigated with a chlorinated secondary effluent at concentrations of 1.01 and 0.33 mu g kg(-1), respectively.