Retrospective Analysis of Pesticide and Drug Transformation Products

Liquid chromatography – high resolution mass spectrometry (LC-HRMS) is ideally suited to detecting drug and pesticide contamination in food products. Gomez-Perez et al. (2015) recently also demonstrated its suitability for deeper interrogation, detecting the transformation products (TPs) derived from these contaminants that may be the only evidence remaining in the products themselves¹.

Food safety standards protect the consumer from harm, frequently governing use of growth-and yield-enhancing chemicals in production. Regulations either ban these compounds or restrict them to maximum inclusion levels below those that are harmful to consumers. Regular monitoring programs help with food industry compliance. However, detection of the parent compound can be difficult since food preparation and industrial processing often results in conditions favorable for transformative chemical reactions to proceed. In these cases, the parent drug or pesticide can be changed or completely degraded, leaving only TPs present as a clue to their earlier existence. Furthermore, TPs may be toxic to human consumers, and frequently contribute to the maximum dose levels permitted for a compound in a food product.

Gomez-Perez et al. took 31 samples, previously extracted and known to contain contaminants according to traditional analytical methodologies. The samples included a variety of food and nutraceutical matrices, including honey, meat, feed, green tea and gingko biloba. Following optimization and validation steps, the team separated the samples by ultra-high performance liquid chromatography (UHPLC), using a Transcend 600 LC in conjunction with a Hypersil GOLD aQ C18 column (both Thermo Scientific). They followed this with HRMS using an Exactive Orbitrap mass spectrometer (Thermo Scientific) in full acquisition mode. The team used Xcalibur 2.2.1 to analyze the data acquired from the extracts

Using a retrospective analysis approach, the team re-examined the 31 extracts. Referring to previous data and using commercial standard preparations as references, they were able to identify possible TPs present in the samples. From the data and comparisons, Gomez-Perez et al. could positively identify one TP and one metabolite, referring to parameters such as absolute mass error, isotopic pattern and comparison of observed against theoretical spectral patterns obtained from commercial standards for conclusive identification.

The two compounds detected and identified with certainty, anhydroerythromycin and 3,5,6-trichloro-2-pyridinol, indicated contamination by an antibiotic (erythromycin – honey sample) and a pesticide (chlorpyrifos – feed) respectively. The latter is restricted in certain European Union countries due to a variety of moderately toxic effects in humans, including neurological and developmental disorders, and autoimmune problems.

In summary, the research team considers that the retrospective analysis workflow described in the paper is a useful tool for food safety monitoring in general, allowing greater interrogation of samples for evidence of contaminants. They describe it as suitable for wider screening techniques to cover a greater number of potentially harmful food contaminants before the product reaches the consumer.

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Reference

1. Gómez-Pérez, M.L. et al. (2015) Identification of transformation products of pesticides and veterinary drugs in food and related matrices: Use of retrospective analysis“, Journal of Chromatography A 1389 (pp.133–8)