Abstract
A simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitating polychlorinated biphenyls (PCBs) in vegetable samples. Parameters affecting both the extraction yields and cleanup efficiency, including the type and volume of extraction solvent, extraction time, type and volume of cleanup sorbent, and cleanup time, were optimized. Matrix effects were evaluated, and matrix-matched calibration was recommended. Under the optimized conditions, carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), which exhibit excellent adsorption capabilities due to large surface area and unique structure, were employed as d-SPE sorbent to remove interfering substances, rather than the analytes, from vegetable samples. Satisfactory linear relationship was observed for all PCBs across a concentration range of 5–500 μg/kg with correlation coefficients no less than 0.9993. Four representative vegetables (cucumber, tomato, lettuce, and cabbage) were selected as matrices for method validation. Each matrix was spiked at concentrations of 5, 10, and 100 μg/kg to evaluate recoveries, which ranged from 84.5% to 116.5% with relative standard deviations (n=6) between 0.6% and 17.6%. The limits of detection and the limits of quantification ranged from 0.3 to 1.4 μg/kg and 0.8 to 4.5 μg/kg, respectively. Twelve real vegetable samples were analyzed using the proposed method. Three of the target PCBs were detected in one lettuce sample with the total concentration of 17.9 μg/kg.
Highlights
Polychlorinated biphenyls (PCBs), a group of 209 congeners that differ in the number and position of chlorine atoms on the biphenyl ring, are anthropogenic chemicals that have been classified and regulated as one of the 12 persistent organic pollutants under the Stockholm Convention on POPs [1]
We aimed to establish a simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) with Multiwalled carbon nanotubes (MWCNTs)-COOH as sorbent for the determination of PCBs in vegetables
In order to obtain the best separation conditions for the analytes, a lowpolarity and low-bleed HP-5MS capillary column was selected for chromatographic separation with the optimal parameters including chromatographic temperature program, carrier gas flow rate, inlet temperature according to the sensitivity, and analytic time of the target analytes
Summary
Polychlorinated biphenyls (PCBs), a group of 209 congeners that differ in the number and position of chlorine atoms on the biphenyl ring, are anthropogenic chemicals that have been classified and regulated as one of the 12 persistent organic pollutants under the Stockholm Convention on POPs [1]. Large amounts of PCBs have been released into the environment, and congeners are still frequently detected in environmental media including soil [5], sediment [6], water [7], and air [8]. Given their extensive historical usage, environmental persistence, and nondegradable nature, PCBs are found in a variety of foodstuffs originating from contaminated soils worldwide [9, 10].
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