Variation in pesticide Residue Testing results
Hi all,
I am working in spices industry; expecting expertise advice on why and how pesticide residue analysis results of 3 tests of same sample varies?
To be more clear, I draw sample from 30 bags and make composite of drawn quantity, dividing the composite into 3 parts, then testing those, gives mixed results of pass and fail? Why this variation? What are the variable factors in pesticide residue analysis?
Do you get the product from one source/grower?
Spices can have an issue with commingling with other crops, due to close proximity with other crops and the regions it is grown:
Following is a good read for understanding, why you could be getting various results:
This is most probably due to non homogeneous distribution of pesticide contamination throughout your product.
Some part of the plants could retain more pesticides that others, plus once grounded, not all surfaces are from the outside of the plant.
It is also very possible that the pesticide have been sprayed un-evenly.
Are you testing the pesticide residues in house or using an outside lab? If in house I would suspect it is your instrumentation or methodology which may not be consistent.
How much variation are you talking about? What percent difference?
If this is an outside laboratory I would contact their technical services to get assistance. If you truly had 3 of the same samples from your composite sample you should not have significant variation in the test results.
Could you be buying from a middleman who is mixing spices from different producers?
Variation is good; it indicates that the testing is actually being conducted rather than the lab making up numbers. If one has enough datapoints, one can even use the variation numbers to run statistical tests and develop expectations for future test results.