Choice of instrument may also depend on the sample source. “If you’re looking for a compound that you suspect may be fat soluble, then the advantage goes to GC. The class of pesticide may also tell you what to use. Older generations of pesticides tended to be chemically nonpolar and, therefore, more stable. Today the focus is on pesticides that do their job and then go away,” said Hammack. “These are far more amenable to LC.” But don’t be complacent, he warns; the older compounds are still very much in use.
In the meantime, pesticide detection is all about stretching the detection limits, and to that end, Hammack is looking to tweak his tools. “We’re looking at tandem MS. This initially pushed the pesticide field toward LC because the GC simply didn’t have those detectors available, but now we’re looking at GCs with the added horsepower we need.” His hope is that GC upgrades will bring more balance to a field currently dominated by LC and its inadvertent limitations.
Selling just such an upgrade is Vivian Watts, PhD, an application chemist at Chromsys in Alexandria, Va., a partner of Agilent Technologies. “Agilent was one of the last players to come up with the GC-MS/MS, and so what we decided to do in 2006 is to develop an upgrade to the existing system,” the so-called Evolution Triple Quad upgrade for the Agilent 5973/5 system. With the addition of Chromsys’ proprietary IonRail collision cell and another high-precision quadrupole Q3, the upgrade results in a state-of-the-art, triple quadrupole GC-MS/MS at a fraction of the cost of a new machine.
It’s a timely idea, and business is good. “As time goes on, more and more pesticides are invented, and countries are in a position of constantly amending watch lists of compounds that can no longer be allowed for consumption,” said Dr. Watts. And better detection limits may be nudging tolerances downward. Can you really detect five parts per billion of whatever in my organic tomato? Well, by all means, let’s consider that. “It does take time for regulations to catch up to the technology. But I can tell you that the EU and Japan already have stricter standards. The U.S. is just now catching up.” Upgrading the Agilent instruments already in play can certainly aid in that effort.
Within every industry, there are troubleshooters. Rachel Linck, PhD, is one of those. She describes her duties as director of technologies at Chemir Analytical Services in Maryland Heights, Mo. “We’re specifically set up to handle non-routine analysis. When companies have issues where they’re not sure if their products are safe for consumption, that’s an answer they need right away.” Dr. Linck will quickly develop a method that facilitates the need of a company’s particular sample matrix. “They tell me of the situations they’re facing, and I design the testing that we’re going to do in the lab to answer the question.”
Often, the protocol required is not on the shelf because, as the song goes, “the times they are a-changing.” “It’s been interesting lately,” Dr. Linck said. “Half the phone calls I get are, ‘We sourced this raw material in China, and we don’t trust the source anymore.’” In essence, the analytical game has become one of expecting the unexpected.
As far as instrumentation is concerned, Dr. Linck recognizes the need for both GC and LC capabilities—the requests she receives demand both. Recently, for example, a meat processing plant had, during a normal application of pesticide to the facility, inadvertently left a freezer door ajar. “So, they knew what they had been spraying. They just needed to know if any residue had reached their product.” Samples were shipped overnight, and the GC-MS quickly did the rest (result: no exposure was detected).