Multiple headspace solid-phase microextraction (MHS-SPME) combined with gas chromatography-nitrogen phosphorus detector is proposed to determine the toxic contaminant ethyl carbamate (EC) in various alcoholic beverages after matrix modification. The remarkable feature of this method is that matrix effect, which commonly appears in SPME-based analysis, is avoided by determining the total amount of the analyte in the sample. To increase the sensitivity of the method, a novel polyethylene glycol/hydroxy-terminated silicone oil fiber was developed by sol–gel technique and applied for the analysis. Owing to the high polarity and hydrophilia of EC, an important problem still remains because the adsorption by sample matrix causes low transport of EC to the headspace and thus invalidates MHS-SPME for quantification. Mixing with anhydrous sodium sulphate, the sensitivity of the method can be improved. A Taguchi's L16 (45) orthogonal array design was employed to evaluate potentially significant factors and screen the optimum conditions for MHS-SPME of EC. Under the optimized conditions, limit of detection of 0.034 mg L−1 was obtained. Relative standard deviation of replicate samples (n = 6) was 2.19%. The proposed method was linear in the range of 0.04–100 mg L−1, and the coefficient of determination was 0.9997. The method was used to determine EC in various alcoholic beverages. The concentrations obtained were compared with those obtained by standard addition method and no statistically significant differences were observed.

A simple, sensitive and inexpensive method has been developed for the quantitative determination of eight polycyclic aromatic hydrocarbons (PAHs) in vegetables based on headspace solid-phase microextraction coupled with gas chromatography using a sol–gel calix[6]arene-containing fiber. Parameters related to the extraction efficiency such as extraction temperature, extraction time, ionic strength, stirring speed, and solvents’ addition were evaluated and optimized. Owing to the good selectivity and high extraction capability of the sol–gel calix[6]arene-containing fiber, low detection limits of 0.04–2.32 ng g−1 and good linearities with linear correlation coefficients >0.9964 were obtained. The relative standard deviation values were <11.6% for all of the PAHs. Average recoveries ranged from 81.07 to 107.5%. The method was applied to analyze nine kinds of vegetables near South Lake, Wuhan, China. The total concentrations of PAHs in these vegetables were found to vary between 3.91 and 96.98 ng g−1 wet weight with 2- and 3-ring PAHs predominating. Generally speaking, PAHs levels in leafy vegetables were higher than those in fruit vegetables, and root and subterranean stem vegetables had the lowest levels. The effect of cooking methods on PAHs concentration in vegetables was tested, and the results showed that PAHs in vegetables reduced a little after blanching, and was not detected after stir-frying.

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 (56) orthogonal array experimental design. Under the optimized conditions, LODs of 0.003–3.429 μg 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 μg 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.