Chemical Residues to Wardrobe Revolutions: My 13 Years Attending NACRW

Simon Hird | Waters Corporation

The first time I attended the Florida Pesticide Residue Workshop (FPRW), precursor to the current North American Chemical Residue Workshop (NACRW), was, I think, back in 2011. Joe Romano kindly invited me to speak at the Waters breakfast seminar and then forgot to book my hotel room! There I was in my fancy suit, sweating like hell at 7 in the morning, watching folk eat breakfast, whilst I droned on through my 90 plus slides on the use of LC-MS/MS for vet drug residue testing! Luckily, I brought shorts and so changed quickly to better fit in…

I have attended every year since, thanks to support initially from Fera and then Waters. Roll on 13 years and I was honored to serve as President for the 2024 meeting. My periodic table pants, made by my wife, were a popular addition to my wardrobe! The 2024 meeting celebrated the rich history of 60 years of the workshop, now covering all sorts of topics related to the analysis of all chemical residues and contaminants in food, feed, and environmental samples.

The conference kicked off on Sunday, July 14th with the NACRW Veterinary Drugs Working Group meeting and a fascinating interactive workshop with Antony Williams from the US EPA on using the EPA Dashboards to support analysis of residues and contaminants. Antony followed this up on the Monday with a keynote. The community is so lucky to have these valuable resources, such as CompTox Chemicals Dashboard, freely available and to have such a passionate and articulate speaker willing to share.

I gave a presentation “Determination of nitrofuran metabolites, including nifursol, in shrimp and fish by UPLC-MS/MS: in-house method validation according to Commission Implementing Regulation (EU)2021/808.” This focused on showing a mainly US-based audience the challenges faced by laboratories in other countries, in this case India, and the support and solutions provided by Waters to help make them successful. Waters also presented 8 posters illustrating solutions on a wide range of topics. It was great to see the use of the BEH zHILIC Column for determination of some polar pollutants vet drugs in water in a prize-winning poster from Katherine Poisson from Northeastern University Department of Chemistry and Chemical Biology.

As expected, PFAS remained a popular topic but with talks not just on the analytical challenges but also reporting findings in a wide range of sample types. Highlights for me included Benedict Liu (CEM), who gave a nice talk on “Automated Solvent Extraction Method of PFAS From Difficult food and Environmental Matrices”, acknowledging Waters contribution to carrying out analyses. In this study, an automated solvent extraction system, the EDGE PFAS, was used to extract fish tissue using the alkaline methanol approach and methanol/water for a range of fresh produce. Critically, the system appears “PFAS-free”. Thomas Simones (Maine Center for Disease Control and Prevention) gave an excellent talk on “PFAS Contamination in Agricultural Settings and Assessment of Human Exposure Pathways through Food Products”. This was an insightful overview of the issues with PFAS in milk and beef in Maine caused by contaminated biosolids. Sampling by Maine state agencies found elevated PFAS levels in farm products and wildlife on and around PFAS-impacted farms. The presentation also showed how EPA 1633 is being adopted by some laboratories for the analysis of food. It was great to hear how labs had done their due diligence to cross validate the use of the EPA 1633 method by successfully comparing results with the more established FDA method.

Non-targeted analysis (NTA) was strongly represented at NACRW in 2024. Anton Kaufmann has come up with an innovative approach to NTA for PFAS that he has applied to the analysis of complex food matrices. The absence of fluorine isotopes, which makes the mass spectrometry based NTA of PFAS difficult, he devised an approach that relies on the fact the presence of the fluorine atom not only increases the mass defect, but also makes the molecule heavier. Plotting mass defect/C versus m/z/C strongly discriminates exogenous PFAS from endogenous compounds. This was demonstrated by analyzing fish tissues (muscle and liver). Unlike other techniques, this simple approach does not rely on fragmentation data, neutral losses, assumption of homologous series or the availability of spectra libraries. The application of the nDATA (nontarget data acquisition for target analysis) workflow for semi-quantitative screening of pesticide residues in fruits and vegetables continues to be developed and doesn’t disappoint. There is a constant demand to include more and more analytes in pesticide residue risk-based monitoring schemes. Typical LC-MS/MS methods are limited to the pesticides targeted and therefore blinded to those (and other residues and contaminants) in the food sample that have not been defined in the method. The nDATA workflow uses liquid chromatography-high-resolution accurate mass (LC-HRAM) spectrometry, operating in full-scan MS and data independent acquisition mode, spectral screening software, and a compound database to screen for over 1000 pesticides in foods. A one-point standard calibration was used to provide semi-quantitative results for any residues detected.

I hope those who attended made the most of their time at NACRW and enjoyed all that sunny Florida has to offer; unwind, soak up the sun, and engaged in thought-provoking discussions about residue and contaminant testing. I look forward to welcoming everyone to NACRW at Charleston, South Carolina, in 2025. If you are one of the many who made this meeting fizz over the previous 60 years, come along for a reunion with that crazy informality and fun that you so loved the last time. I promise to wear the periodic table pants again. You won’t regret it!

Gordon Fujimoto Joel Keelor Nathaniel Moore Michael MacDonald Naren Meruva, PhD, MBA

Are you interested in learning more about PFAS analysis? Check out our PFAS Testing Application Notebook.

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