QuEChERS method

The QuEChERS method was invented and described for the first time in 2003 by Anastassiades et al. [98] as a fast, simple, inexpensive, and convenient preparation procedure for fruit and vegetable samples used for pesticide multiresidue analysis. Currently, this methodology is used for determinations of pesticides, pesticide residues, and other compounds of environmental concern such as phenol derivatives, perfluorinated compounds, and chlorinated hydrocarbons pharmaceutical compounds in food and agricultural matrices and environmental samples such as soil, sediments, and water (see for example [99-102]). 

Table 6.6 GC-MS analytical conditions used for analysis of pesticides by the QuEChERS method.

Table 6.7 Pesticides with their retention time and ions used for quantification in SIM mode by performing GC-MS analysis with QuEChERS method.

GC/MS-SIM analysis coupled with QuEChERS method (section 9.2.1.1) is performed using the analytical conditions reported in Table 9.6. Pesticides analyzed are reported in Table 9.7 with their GC retention time and the m/z ion used for quantification. 

TABLE 9.7. Retention Times (RT) and Quantification Ions in the GC/MS-SIM Analysis of Pesticides in Grape Extract and Wine Coupled with the QuEChERS Method"... 

With the implementation of the original QuEChERS-method in our pesticide residue analysis laboratory in 2002, and the associated validation experiments for numerous pesticides in different representative commodities, it soon became clear that some amendments to the original procedure had to be introduced to improve the recoveries of certain pH-dependent pesticides and to expand the spectrum of commodities amenable to the method. The routine use of the method furthermore raised the need to further improve its selectivity in order to enhance the robustness of determinative analysis. The modifications introduced are subject of this paper. 

Selectivity of partitioning The addition of citrus buffering salts to elevate the pH of sour fruits has also dramatically reduced the amount of co-extractives in the raw extracts. This observation was also made during the development of the original QuEChERS method where the peaks of fatty acids as well as of maleic and fumaric acid in full-scan GC/MS became smaller as the pH of acidic samples... 

Figure 2. Influence of buffering on the selectivity of the QuEChERS method.

The modifications introduced to the QuEChERS method in order to prevent degradation of pH sensitive pesticides, improve selectivity of partitioning and cleanup, and to expand the spectrum of commodities covered, clearly improved... 

Anastassiades, M. Lehotay, S.J. Stajnbaher, D. Schenck, F. Fast and easy multiresidue method employing acetonitrile extraction/ partitioning and dispersive solid phase extraction for the determination of pesticide residues in produce. (QuEChERS method). J. AOACInt. 2003, 86, 412 31. 

Koesukwiwat, U., Lehotay, S. J., Mastovska, K., Dorweiler, K. J., and Leepipatpiboon, N. 2010. Extension of the QuEChERS method for pesticide residues in cereals to flaxseeds, peanuts, and doughs. J. Agric. Food Chem. 58 5950-5958. 

The extraction of milk samples was done by the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method [13], modified by adding disodium ethylene-diaminetetraacetate dihydrate (Na2-EDTA). Without any further cleanup, the extract was separated on HPTLC silica gel plates modified by Na2-EDTA. The development was performed with chloroform/methanol/ammonium hydroxide solution (25%), 60/35/5 (v/v/v), followed by fluorescence densitometry (ELD) at 366 nm/<400 nm... 

A popular approach for sample treatment is the QuECHERS method, which is gaining increasing recognition in PRA laboratories [12]. It is based on the use of acetonitrile (ACN) and MgS04 for salting-out... 

EN 15662 Determination of pesticide residues using GC-MS and/or LC-MS(/MS) following acetonitrile extraction/partitioning and cleanup by dispersive SPE—QuECHERS method. In European Committee for Standardization, Technical Committee CEN/TC 275, Food analysis—horizontal methods. Brussels European Committee for Standardization, 2008. 

The QuEChERS method is a streamlined approach that makes it easier and less expensive for analytical chemists to examine pesticide residues in food. 

Figure 2.45 Recoveries in the QuEChERS method, 229 pesticides analysed by GC-MS and LC-MS/MS (Lehotay, 2013).

Brondi, S.H.G., de Macedo, A.N., Vicente, G.H.L., and Nogueira, A.R.A. (2011) Evaluation of the QuEChERS method and gas chromatography—mass spectrometry for the analysis pesticide residues in water and sediment. Bull. Environ. Contam. Toxicol., 86, 18-22. 

European Standard EN15662. (2008) Foods of Plant Origin - Determination of Pesticide Residues Using GC-MS and/or LC-MS/MS Following Acetonitrile Extrac-tion/Partitioning and Clean-Up by Dispersive SPE -QuEChERS Method. European Standard. 

Lesueur, C., R Knittl, M. Gartner et al. 2008. Analysis of 140 pesticides from conventional farming foodstuff samples after extraction with the modified QuEChERS method. Food Control. 19 906-914. 

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