Determination of trace contaminants in foods
thesisposted on 11.04.2016, 08:38 authored by Kathy Ridgway
Determination of low levels of chemicals unintentionally present in foods (trace contaminants) often requires extensive wet chemistry extraction and clean-up regimes prior to instrumental analysis and this is usually the bottleneck in analysis. In order to determine if levels pose a human health risk, rapid reliable methods are required that can unequivocally identify and quantify contaminants at trace levels. In particular, current methods for targeted food taint analysis have long extraction times and rapid screening methods such as direct headspace, do not provide the sensitivity required. In order to address the issues raised above, this study set out to review all aspects of sample preparation and the applicability of each technique for the determination of trace organic contaminants in foods. Following the review, solid-phase dynamic extraction (SPDE) was evaluated for the determination of example food contaminants furan and the BTEX compounds (benzene, toluene, ethyl benzene and 0, rn, and p-xylene). Stir bar sorptive extraction (SBSE) was also evaluated for the determination of furan, benzene and toluene. A SBSE method for the determination of furan in food and beverages was developed which gave the advantage of extraction at ambient temperature, (thus minimising potential formation) and was comparable to direct static headspace in performance and sensitivity. The use of SBSE was then evaluated for use as a generic screening method for compounds known to cause taints in foods. Twenty example compounds were chosen based on previously reported taints from a range of origins and included those most commonly investigated (such as halogenated phenols and anisoles). The optimised SBSE method was compared to the more established techniques, direct static headspace and steam distillation extraction using Likens Nickerson apparatus. The SBSE method provided an increase in sensitivity for most compounds and further improvements were demonstrated for more targeted analysis, using a GC-MS, GC-MS/MS and GC-HRMS instrumentation.