A New Risk Based Approach to Testing Pesticides
The latest ISO17025 standard that labs are accredited to has been released, with one important change (Clause 8.5.3) being that “laboratories are now required to address any risk that has the potential to impact on the validity of laboratory results”. Because of this Eurofins-ELS has significantly changed the way we test and report pesticide residues
Each pesticides residue sample is analysed for over 500 compounds across several instruments. This technique is common for all of the labs in NZ, but it is considered a screening technique only.
To increase the certainty of our results using this screening method, for each sample type we analyse, we prepare a second sample called a matrix-matched overspike. We add a known value of every pesticide compound we report to this second sample, and then we analyse it alongside the original sample.
Occasionally we don’t see a result for some compounds in the second sample because of the complex chemistry between the residue compound and the matrix of the sample. For example, some residues are fat soluble, others are water soluble, and others can be destroyed by the acids within the sample, or have other chemical interactions with substances like sugars and proteins that are present in the sample.
When we identify this type of matrix effect on the pesticide residue we cannot say with certainty that it is in the sample: it may be present and is being masked by the makeup of the sample itself. When this happens, instead of reporting the result as “Not detected”, and indicating that everything is OK, we would report it as “Not Recovered”. Please note: If the result is an important pesticide residue, we can possibly do further work on the sample to recover a result.
Sometimes, a matrix effect stops us from clearly identifying the pesticide residue at our normal level of reporting. This forces us to raise the limit of reporting to the point we can be certain of. For example: instead of seeing <0.010 on our report you will see <0.050 or higher.
This matrix matching technique looks at the result of every compound we report and provides you with the most accurate result possible.
Our approach may be different than you are used to, but it does provide you with a report that minimises the risk of reporting a pesticide residue incorrectly. Please Contact Us for more information.
Shimadzu GC-MSMS
Shimadzu LC-MSMS