How to optimize workflows for sample prep and rapid analysis of contaminants in foods by LC-MS/MS: Your questions answered

Understanding the pros and cons of different approaches for detecting and quantifying pesticides and toxins in different foods is essential when optimizing your LC workflows, especially for challenging matrices.

In this on-demand SelectScience^® webinar, Joe Konschnik, business development manager for the food and agriculture market at Restek, presents insights into recent advances in chromatography technology. Konschnik also discusses how to apply these technologies to food commodity testing workflows to overcome common challenges, simplify sample preparation, speed up analysis, and minimize the reporting of false negatives and positives in your results.

Read on for highlights from the Q&A session or register to watch the full webinar on demand.

Q: Do you think the use of graphitized carbon black (GCB) for your celery and spinach solid-phase extraction (SPE) cleanup procedures had an impact on some pesticides’ poor recovery?

JK: Yes, we looked at GCB and conducted a couple of experiments for some of the pesticides. We noticed issues with compounds such as thiabendazole, a planar pesticide which can be affected by the graphitized carbon black in the dispersive SPE cleanup. We also had some ionization challenges in the source with other pesticides because they tended to break down. In the future, we intend to look at studying this further. If you refer to the blog on Restek's website, my colleague Jana Rousova posted about her work with pesticides by GC-MS/MS where she did some comparative QuEChERS experiments, looking at the impact of GCB on various pesticides.

Q: In your work with mycotoxin analysis on rice flour and peanut powder, what kind of backpressures did you observe? You are running at 0.5 milliliters per minute for your fast analysis — was this an issue?

JK: Most of our backpressures were just under or just over 4,000 psi, with one exception. We did have issues with wheat flour. We observed clogging and very high backpressure and even killed one column with wheat flour. We have heard from other people that this tends to be a challenging matrix even after filtering through a 0.2um PTFE filter. Properly removing fine particles is recommended for wheat flour, but with the rest of the commodities, we had no issues with backpressure or clogging.

Q: Do you have a mix of polar pesticides and plant growth regulators?

JK: We have not yet formulated a stock product for polar pesticides in a mix. However, we are working on that, and we are preparing custom mixtures for polar pesticides. I would encourage you to send us an email directly, and we will respond back with a formulation, depending on which polar pesticides you are interested in. For the European QuPPe method, there are as many as 17 or 18 different polar pesticides, so I would be happy to look at that for you.

Q: Could you suggest any Restek products for samples with animal origin for quantifying flumethrin honey? Could you also help with method optimization and sample preparation?

JK: While I don’t think we’ve done any work with flumethrin in honey, we do have some work that was done on fish tissues for pesticide analysis. Some of that data can be found on our blog site. We have a ChromaBLOGraphy webpage that you can click on and search in there. If we can correspond via email, that is probably the best way for me to direct you to those specific posts.

Q: When you mix the 10 LC multiresidue kit ampules together to make a single mix of 200+ compounds, were you concerned about the stability?

JK: This has been a concern for several years and since then we have launched multiple studies to look at the degradation of pesticides upon mixing. For example, we conducted one study where we looked at the stability of the pesticide mixes once the ampule is cracked open. The contents are tested repeatedly after being transferred to a storage vial, then stored in refrigerator and freezer conditions over 31 days. We also looked at some routine mixture degradation studies for both LC-MS/MS and GC-MS/MS workflows.

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