Development and application of an SPME/GC method for the determination of trace phthalates in beer using a calix[6]arene fiber

A simple, low-cost and sensitive method for the determination of phthalate acid esters (PAEs) in beer has been developed based on solid-phase microextraction (SPME) followed by gas chromatography using a novel sol-gel calixarene-contained fiber. Generally speaking, matrix interference is one of the most important problems that researchers have to face when quantifying trace compounds in the complicated beer samples. In order to reproduce the influence of the matrix, synthetic beer solutions were popularly used, while they could not represent the real beer matrix absolutely. Owing to the good selectivity and high sensitivity of this new calixarene fiber, matrix interference from the beer samples was effectively avoided and low limits of detection (LODs) could be achieved. As a result, the SPME was performed in real beer matrices. Five experimental parameters including extraction temperature, extraction time, stirring speed, salt concentration and ultrasonic time were evaluated and optimized by means of a Taguchi's L25 (5(6)) orthogonal array experimental design. Under the optimized conditions, LODs of 0.003-3.429 mu g L-1 were obtained and the relative standard deviation values were <= 13.51% for all of the eight PAEs. The method was validated using standard addition methodology and recovery values were between 86.3% and 109.3%. The survey of three bottled beer samples showed that dibutyl-phthalate ester and bis(2-ethylhexyl)-phthalate ester (DEHP) were the main PAEs found in beer. The concentration of DEHP was as high as 5.24 mu g L-1. In order to investigate the source of phthalates contamination in beer, the composition of phthalates in the plasticized polyvinyl chloride (PVC) gaskets of the lids was analyzed. Results revealed that the high content of DEHP incorporated in PVC gaskets could be a potential source of PAEs in bottled beers during transportation and storage. (C) 2009 Elsevier B.V. All rights reserved.