Lowering Detection Limits for Routine Analysis of Pesticides Residues in Foods

Concerns regarding threats to the environment and human health from the use of pesticides have prompted government agencies worldwide to continually lower required detection limits for these compounds. These limits are necessary to ensure compliance to mandated maximum residue levels (MRLs).

The European Commission has been very active in establishing MRLs, described as safe limits that define the maximum expected levels of a pesticide on a food commodity after safe and authorized use of that pesticide (guidance document SANCO/3346/2001 rev 7). They serve to prevent illegal or excessive use of a pesticide, and protect the health of consumers. These MRLs are based upon residue levels from trials in which the pesticide was used on the crop at the correct application rate and waiting time. To check if this level is acceptable for consumer exposure, intake calculations for various consumer groups are made for acute and chronic intake. If the level is acceptable, the MRL is set by the Commission. If not, the limit of detection (LOD) is applied.

The default threshold MRL value is set at 0.01 mg/kg, or 10 ng/g, in the European Union (EU) and Japan. However, there is interest in collecting pesticide residue data at levels as low as possible in infant and baby food to assess exposure in this sensitive population.

Many foodstuffs are very complex, or “dirty”, due to the presence of a large number of background compounds. Backflushing the GC column ensures that high-boiling compounds in the matrix are not passed through the column, reduces column bleed, eliminates ghost peaks, and minimizes contamination of the mass spectrometer.

In addition, tandem mass spectrometry (MS/MS) on a triple quadrupole platform is very useful for screening, confirming, and quantitating trace level target compounds in these complex matrices because it can minimize interferences. This application note describes a study using backflushing and the Agilent 7000C Triple Quadrupole GC/MS to measure pesticide residue levels well below the current threshold of 10 ng/g.

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