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Validation of a Simple and Rapid Multiresidue Method (QuEChERS) and its Implementation in Routine Pesticide Analysis
Michelangelo Anastassiades, Ellen Scherbaum and Dorothea Bertsch Chemisches und Veterinäruntersuchungsamt Stuttgart, Schaflandstrasse 3/2, 70736 Fellbach

Poster presented at the MGPR Symposium (May 2003, Aix en Provence, France)

CONTENTS
IntroductionMini-Multiresidue-Method (QuEChERS) Validation studies Solvent consumption Conclusions Reference

INTRODUCTION
Many pesticide multiresidue methods (MRMs) used are complicated, laborious, time consuming, require high amounts of solvents and are therefore expensive. What makes traditional multiresidue methods inefficient?
Main Drawbacks
Large Sample-Sizes “Macro-Approach”

Consequences
Wasteful: High Solvent &Material Consumption

End Result
Environmentally Critical

Too Many, Analytical Steps
Time-Consuming and Troublesome Procedures

Expensive

Complicated Tasks

Error-Prone

Considering that the time spent for instrumental analysis is also continuously growing due to the introduction of new analytes and instrument techniques, laboratories are not able to analyse the number of samples theywould like to. In addition, some important analytes can not be satisfactorily covered by many common MRMs (e.g. basic, acidic and very polar compounds). In order to cover such analytes, laboratories have to additionally perform laborious single analyte methods, which is often not possible. This results in a large grey area of pesticides which are not routinely monitored by most laboratories. Inthe last decade there has been a general trend to develop faster analytical methods. The automated instrument based extraction procedures SFE and ASE, MGPR, May 2003, Aix en Provence, France

which were introduced in the mid 1990s to speed up extraction, did not succeed to replace traditional multiresidue approaches. Ideally, a multiresidue method should be fast and easy to perform, require aminimum amount of chemicals, provide a certain degree of selectivity to avoid complicated cleanup procedures and still cover a sufficiently broad spectrum of analytes. Analysts accustomed to performing complex traditional analytical procedures often hesitate to switch to simpler ones assuming that a simpler and faster analytical procedure can not be accurate enough and should, if at all, only beused for screening procedures. In reality, however, the more analytical steps a procedure entails and the more complicated it is the more likely is the introduction of systematic and random errors.

MINI-MULTIRESIDUE-METHOD (QUECHERS)
During the development of the method the principal aim was to make it as streamlined as possible by avoiding complicated and time consuming analytical steps.
TimeConsuming, Complicated or Error-Prone Steps Sample Processing/Homogenization Blending (e.g. with Ultra-Turrax) Filtration Multiple Partitioning Steps Separation/Transfers of Entire Extract Use of a Lot of Glassware Evaporation/Reconstitution Classical SPE with Columns & Manifold Simplified Alternatives

No Way Around this Shaking Centrifugation Single Partitioning (“On-line”-Approach) TakeAliquots (Use ISTD) Extraction/Partitioning in Single Vessel Large Volume Injection; Sensitive Instr. Dispersive SPE

The analytical procedure
A schematic view of the analytical procedure is shown below. The entire method is published under [1].
Weigh 10 g of Sample (50 mL Teflon-Tube)

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Add 10 mL Acetonitrile
Shake Vigorously 1 min

Add 4 g MgSO4 and 1 g NaClShake Vigorously 1 min

Add ISTD-Solution

Shake 30 s and Centrifuge 3, 6, 7

Take Aliquot and Add MgSO4 (and Sorbent)
(Add 0.1 % HAc and “Analyte Protectants” )

Shake 30 s and Centrifuge 9, 10

MGPR, May 2003, GC-MSD and LC-MS Aix en Provence, France

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MGPR, May 2003, Aix en Provence, France

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