Alberta Invests in Food Residue Analysis

EDMONTON - Sep 29/05 - SNS -- Alberta Agriculture has invested in a new tandem mass spectrometer (LC-MS/MS) system so that it can rapidly test for chemical residue in food products.

"The instrument is not cheap, but the stakes for the agri-food industry are very high," says Dr. Tom Thompson of Alberta Agriculture's food safety division, Edmonton.

"Various chemicals and medications are used in agriculture to improve the health and production of plants and animals. My job is to monitor certain commodities to ensure that any residues, if present, are present at safe levels."

If present at all, residues of agricultural chemicals and medications occur at very low levels - often less than one part per million. The tandem mass spectrometer was specifically designed to detect these very low levels of chemical residues in complex samples such as food products.

This new instrument is the current "gold standard" for chemical residue analysis. The liquid chromatograph portion of the instrument separates various chemicals from each other, and then passes them to the mass spectrometer for detection.

The mass spectrometer provides something similar to a chemical fingerprint - a detailed description of a molecule based on its mass and structure. The mass spectrometer uses two mass filters in tandem separated by a collision cell.

The first filter discards chemical information related to all but the mass that is characteristic of the target compound. The collision cell breaks that molecule apart, producing fragments that are distinctive for the target compound - a molecular fingerprint. These fragments are then detected by the second mass filter.

"This tandem configuration gets rid of a lot of chemical 'noise'," says Thompson. "As a result, the specificity and sensitivity are dramatically increased. We can detect very low levels and detect them with a very high level of accuracy.

"I've always been fascinated with being able to detect a minuscule amount of a contaminant in a complex matrix, the proverbial needle in a haystack. With LC-MS/MS technology we can detect substances that were previously very difficult or impossible to analyze. It is comforting to be able to tell people with certainty that our food has very few residues and that the ones we find are at very low levels."

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