Evaporated Extracts of Samples for Pesticide Residue Analysis Simplifies Transport from Remote Places

The increasing use of pesticides demands a world-wide control of residue levels in food and the environment. However, pesticide residue analysis is challenging and needs both experience and instrumentation. Although much can be done with fairly simple means, many countries with limited resources can only perform certain analyses. Also in technologically more advanced countries, different laboratories may specialize in certain kinds of analyses and there is also a need to confirm results with an exchange of samples between laboratories. There are usually several technical difficulties connected with the transport of pesticide samples, in addition to the risk of transmission of pests and diseases and related customs control; and in many areas of the world transport of pesticide samples is not feasible at all. A way to circumvent these difficulties is presented here. Even if a laboratory lacks the basic requirements to purchase, run and maintain instrumentation to analyze pesticide residues, there are often possibilities to extract the pesticide samples. The extracts are taken to dryness in the presence of a ‘keeper’ substance, and the residues can then be sent in apparently empty glass vials. We have investigated the use of polyethylene glycol as a keeper at harsh conditions, for up to three weeks at 44°C. This was done to find out whether the residues remain in the vials at simulated transport conditions. In all, 64 pesticides were tested and of these 56 substances give recoveries of at least 70% after storage at 44°C for 3 weeks. Thus, according to the results it would be possible to send pesticide samples as evaporated extracts even in a hot climate. In conclusion, the results presented here clearly show that a much simplified method of transfer of samples between laboratories is adequate, which enables monitoring of pesticide residues in any part of the world.