A pesticide multi-residue test screens one sample for many pesticides in a single analysis. Most labs extract the sample and run it on two instruments: liquid chromatography with tandem mass spectrometry (LC-MS/MS) and gas chromatography with tandem mass spectrometry (GC-MS/MS).
How many compounds it covers depends on the lab and the package you order. Screens commonly cover a few hundred compounds, and larger packages cover more. There is no standard number, so ask for the compound list.
How the test works
The lab grinds and mixes the sample, then extracts residues with a solvent. A common approach is QuEChERS, a quick extraction and clean-up method used worldwide. Spices are a difficult matrix. Their oils, colours and strong flavours interfere with the analysis, so the lab must have validated its method on spices, not only on fruit and vegetables.
Each compound is identified and measured against a reference standard. The result is reported in mg/kg, with a limit of quantification (LOQ) for each compound.
What a multi-residue screen misses
Some pesticides and residues cannot be measured by the standard screen. They need separate single-residue methods, ordered and priced separately.
- Ethylene oxide and 2-chloroethanol.
- Glyphosate and similar very polar herbicides.
- Dithiocarbamates, usually measured as carbon disulphide.
- Chlorate and perchlorate.
- Fosetyl and phosphonic acid.
- Some fumigants, such as residues linked to phosphine or bromide.
Questions to ask the lab
- How many compounds are in this package, and can you send the full list?
- Is the method accredited for spices, or for this exact spice?
- What is the LOQ for each compound? Is it at or below 0.01 mg/kg?
- Does the list include the pesticides used on this crop in India?
- Are residue definitions reported as the EU defines them, for example as sums?
- Which single-residue tests do you recommend for this product?
More compounds is not always better
A list of 500 compounds that leaves out the three most used on Indian chilli is less useful than a shorter list that includes them. Check that the list covers the pesticides that farmers actually use on your crop and those seen in RASFF notifications. Then check the LOQs. A long list with LOQs too high for EU limits gives false comfort.
For how residues fit into EU limits, see what MRLs are and how to check the EU limit.
A good report lists every compound tested, not only those found. Any detection should be shown with its value, even if below the MRL. A clean screen tells you about the sample tested. If that sample was not drawn from your lot by someone independent, it tells you little more.
How we help
We choose a multi-residue package for your product by its compound list and LOQs, and add single-residue tests where the crop needs them. We send sealed samples from the packed lot to an NABL-accredited lab. Ask for a free sourcing review.