Detect Pesticides With Mass Spec

More than once in my marriage—in fact, more than once in the last month—my significant other has presented me with a mysterious substance and asked, “Does this taste funny to you?” I generally decline these invitations to explore the unknown, not because I lack the courage, though that is true, but as someone with a science background, I feel I lack the proper instrumentation.

Actually, real scientists are increasingly faced with this same dilemma. According to “The Analytical Cornucopia,” a report issued recently by Los Angeles-based consulting firm Strategic Directions International (SDI), the global market for laboratory instrumentation dedicated to food applications amounted to $2 billion last year. Technology geared toward the detection of pesticides—which really do taste funny—garnered a large stack of those dollars.

“Although simple, non-quantitative test kits can provide information on the presence of pesticides and other residues, the food industry is increasingly turning toward the quantitative analytical solutions like those used by regulatory agencies,” said Michael Tice, vice president of consulting for SDI. He added that the technologies currently experiencing the greatest growth in pesticide analysis are liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS).

Contributing to that growth is the recent purchase by the Environmental Protection Agency (EPA) of the Acquity UPLC/ Xevo TQ Mass Spectrometry System, from the Waters Corp., Milford, Mass. “We’re continually trying to stay abreast of new technology,” says Charles Stafford, team leader of the analytical chemistry branch of the EPA lab in Fort Meade, Md. “We need machines that can detect lower and lower levels of pesticides, and frankly, we need more machines. All our instruments are booked.”

Since the melamine scare of two years ago, Stafford has noticed not only an uptick in overall activity but also a new emphasis on screening samples for unknowns. “We just weren’t doing things like that before, looking for what shouldn’t be there. The same holds true for novel pesticides. So we’re struggling with approaches and instrumentation which will allow us to screen samples for untargeted compounds.”

That is not to say that Stafford is actually doing most of the testing. His lab primarily develops the analytic methods to support regulatory activities, those that discern the dietary exposure side of the risk-assessment equation. “We help either develop methods or provide maximum residue levels (MRL) data that will help scientists determine whether a chemical is safe.”

The globalized nature of foods with multiple ingredients begs the question of harmonization of “safe” MRLs. “From the perspective of my lab,” says Stafford, “if someone asks me to evaluate data that comes from another source, the most important thing we say is ‘how did they do the sample, what method did they use from start to finish,’ and that includes the detector. That’s not to say that data is bad if generated by using an element-specific detector, but in the back of your mind …”

Certainly there are valid alternatives to GC or LC-MS out there. Any number of element-specific assays and instruments exist, but their efficacy hinges on knowing exactly what you’re looking for, and that knowledge can no longer be assumed.

LC or GC?

“There is reasonably good harmonization within the United States,” says Walter Hammack, environmental manager at the Florida Department of Agriculture, “but it’s more of an issue internationally.” Hammack’s mission is to enforce EPA tolerances, collaborating efforts with the United States Department of Agriculture as well as other agencies. “We’re trying to get an idea what residue pesticides people are exposed to right at the dinner table,” regardless of the source. Hammack receives samples from all over the world.

Hammack also assigns the technology and has long coordinated the activities of his LC and GC spectrometers. “Both have very powerful strengths, LC because a lot of the newer pesticides that we’re looking for are amenable to LC separation.” Historically, however, GCs had the advantage of more sensitive detectors, and a true unknown could be tackled with GC-MS and electron ionization with spectra matched against known libraries. “The limit here is the GC part. The analyte may not survive, whereas the LC is far more gentle.”

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