The Column - August 2008 - (Page 6)

Helle, Baden and Gil The Column www.thecolumn.eu.com August 2008 Purestock/foodcollection/Getty Images Pesticide Residues in Fruit and Vegetables 1TeLa Norbert Helle,1 Meike Baden1 and Carlos Gil,2 GmbH, Bremerhaven, Germany, 2Gerstel GmbH & Co. KG, Mülheim an der Ruhr, Germany. From avocados to zucchinis — when the sample matrix no longer matters. In the chemical tool-kit of today’s farmers or agricultural engineers, pesticides such as insecticides, fungicides, herbicides and acaricides are essential ingredients that help provide an adequate supply of food to the ever-growing human population. Whenever chemical tools are applied to protecting our food supply from competing species, residues in foods must, of course, be limited to levels that don’t endanger or affect the health of the consumer. Maximum acceptable levels, sometimes referred to as tolerated levels, have been established for individual compounds. If these levels were exceeded, it would be illegal to market the contaminated product in Europe. Corresponding laws have been established by the EU. This legal basis must be, or, in some instances, already has been, adapted into National law by EU member states. In Germany, the details on maximum acceptable levels of residues can be found in the German LFGB, the compendium of laws governing food, feed and various consumer products. In May 2008, Germany further decided to temporarily ban eight neo-nicotinoid pesticides on the suspicion that one or more could be related to the death or disappearance of whole colonies of bees; the widely reported Colony Collapse Disorder (CCD), which endangers vital pollination and, thereby, crop yields. Rules, unless properly enforced, may have little impact. In other words trust is fine but we should verify and take corrective action as needed to ensure compliance and best possible consumer safety. This requires a network of reliable laboratories — not a trivial matter as is reported later in this article. Author: Norbert Helle E-mail: postfach@tela-bremerhaven.de The analytical aspects pose a significant challenge. Worldwide, approximately 700 pesticides are in use, very few of which can be legally used throughout Europe. Various compound classes have been established but even these can cover a wide range of polarities, making it difficult to develop a fast, all encompassing analysis method. Still, effective multiresidue methods are in use for the determination of pesticides, helping to ensure food safety. When fruit and vegetables are analysed for pesticide residues, often several pesticides are found. The effects on human health have only been documented for very few of these compounds or compound groups. Tracking Down Pesticide Residues using GC–MS and LC–MS In Germany, the analytes that are mainly in focus are those listed in the DFG S19 method, a multiresidue method for the determination of pesticides in food, which enjoys Europe-wide recognition. The analysis of the 270 compounds listed in the S19 method does, however, require significant sample preparation including a gel chromatography clean-up step to separate analytes from matrix. Different analysis techniques are used for different types of pesticides. Liquid chromatography (LC) combined with a mass selective detector (MS) is used to determine polar to moderately apolar compounds, which covers the more “modern” types of crop protecting compounds, examples of which are shown in Figure 1. These types of pesticides are more reactive than traditional pesticides. Glyphosat, for 6 http://www.thecolumn.eu.com

Table of Contents for the Digital Edition of The Column - August 2008

The Column - August 2008
Contents
Pesticide Residues in Fruit and Vegetables - From Avocados to Zucchinis
News
Incognito
Market Trends and Analysis
Tips and Tricks: GPC/SEC What are The Applications for Polymer Reference Standards?
Transferring Existing HPLC Methods to MicroLC
Q&A

The Column - August 2008