Pesticides are chemical compounds used to kill, repel or control unwanted plants, animals and microorganisms (i.e. those considered to be weeds, pests and diseases). Pesticides such as herbicides, insecticides, fungicides, antimicrobials and disinfectants are used routinely on agricultural products, including food and animal feed, to maximize crop output and protect produce during storage and transportation. Through the consumption of such products, humans and animals are exposed to low levels of pesticides in their diets.
In order to protect consumers, pesticide residues are under strict legislation worldwide. The maximum residue level (MRL) is the highest amount of an individual pesticide residue that is permitted to be present in or on food or animal feed. MRLs vary from region to region across the world and food manufacturers exporting produce to other countries must meet all the individual MRLs in each target region.
The process for analyzing pesticide residues typically involves extracting the residues, clean-up procedures to remove other components, and an analytical procedure to identify and measure the amount of pesticide residue.
The pesticide residues are usually analyzed by the following methods:
- Gas Chromatography – Mass Spectrometry Coupled (GC-MS), especially for volatile compounds in complex samples
- Liquid Chromatography – Mass Spectrometry Coupled (LC-MS), suitable for non-volatile compounds (thermally unstable molecules)
Pesticide residue analysis using these techniques enables individual pesticides in a sample to be identified and quantified when compared against a matrix of known pesticides. For best results, the method requires reproducible conditions and the use of high quality reference standards.
Why Accurate Preparation of Reference Standards is Crucial
Analysis of pesticide residues is a highly sensitive procedure requiring extremely accurate solutions. Accurate weighing and dosing of reference standards, as well as dilution with solvents, is therefore critical. Given the inherent errors associated with both pipetting and volumetric glassware, preparing solutions gravimetrically offers an increased level of accuracy.