QuEChERS

Several groups have adapted the method to analyze residues in a variety of matrices. Acetic acid (HQAc, 1%) and sodium acetate have been widely used to adjust and maintain pH and promote stability and recovery of base-sensitive residues. HOAc was used to adjust pH by Stubbings and Bigwood to determine residues [sulfonamides, quinolones, (fluoro)quinolones, ionophores, and nitroimidazoles] in chicken muscle. Buffering to acidic conditions improved the extraction efficiency of quinolones. Aeetonitrile extracts were subsequently purified by dSPE (see also Section 4.4.6.1) over Bondesil NH2 sorbent. An aliquot of the extracts was evaporated to dryness and re-dissolved in acetonitrile water (90 10, v/v) before LC-MS/MS analysis. Validation was performed on chicken muscle samples, and matrix-matched standards were used because suppression of the MS response was observed for many of the target analytes. 

The SPE field is still developing, with the introduction in 2009 of an automated SPE instrument from Dionex designed to be used with large-volume samples (20 mL to 4 L) for the isolation of trace organics in water and other aqueous matrices. 

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Recent trends in pesticide analysis in food aims for reduced sample pretreatments or simplified methodologies (as QuEChERS approaches), the use of online purification processes, the use of new adsorbents (such as molecular imprinted polymers (MIPs) and nanomaterials) for the extraction and clean-up processes, and focused on the development of large multiresidue methods, most of them based on LC-MS/ MS. In spite of the relevant role of LC-MS/MS, GC-MS-based methods still play an important role in pesticide analysis in food. Despite the development achieved in the immunochemical approaches, the need for multi-residue methods has supported the development and use of instrumental techniques. 

QuEChERS (quick, easy, cheap, effective, rugged, and safe) is an acronym used as the name of a sample preparation procedure, generally based on a combination of solvent extraction of analytes from a sample and dispersive SPE applied for cleaning an extractant. 

Universal kits, developed and widely commercially available for the QuEChERS procedures, provide excellent recoveries and reproducibility. The complete commercial QuEChERS kits are of great advantage in standardization of this technique and in assuring high quality of analytical achievements, compatible with current methodologies recommended by both the Association of Analytical Communities (AOAC) and European Committee for Standardization (CEN). 

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]). 

Wilkowska, A., Biziuk, M. Determination of pesticide residues in food matrices using the QuEChERS methodology. Food Chem. 125, 803-812 (2011)... 

Golge, O., Kabak, B. Evaluation of QuEChERS sample preparation and liquid chromatography-triple-quadrupole mass spectrometry method for the determination of 109 pesticide residues in tomatoes. Food Chem. 176, 319-332 (2015)... 

Bruzzoniti, M.C., Checchini, L., De Carlo, R.M., Orlandini, S., Rivoira, L., Del Buhba, M. QuEChERS sample preparation for the determination of pesticides and other organic residues in environmental matrices a critical review. Anal. Bioanal. Chem. 406, 4089-4116 (2014)... 

Lately, a method called QuEChERS - using acetonitrile as the extraction solvent and MgS04 and NaCl for salting out - was proposed. 

Multiresidue method for the determination of pesticides residues in grape (QuEChERS)(Anastassiades et al., 2003)... 

The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method allows the extraction of a wide variety of pesticides from polar and basic (methamidophos, acephate, omethoate, imazalil and thiabendazole) to less polar, such as pyrethrins. Samples of homogenized grape (lOg) are extracted with 10 mL of acetonitrile. After shaking for 1 min, 4 g of anhydrous MgS04 and 1 g of NaCl are added and mixed. One milliliter of the acetonitrile aliquot is transferred to a 1.5 mL vial... 

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 9.6. The GC/MS Conditions Used for Analysis of Pesticides Coupled with the QuEChERS Method2... 

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"... 

Kaufmann et al. developed a bipolarity extraction method based on principles similar to those of the QuEChERS technique. With the use of this isolation technique, polar and non-polar residues remained in the aqueous phase and underwent clean-up by SPE on a mixed-mode Oasis HLB cartridge. The residues were subsequently analyzed by UPLC-MS/MS. Extracts isolated using the bipolarity approach required a lengthy SPE procedure prior to analysis. Kaufmann stated that extracts produced at the end of the procedure contained less matrix components compared to QuEChERS. However, it can be concluded that... 

QuEChERS, due to its low cost, coupled to its flexibility and ease of use, will be increasingly applied in residue analysis. 

S, Q, M, T Milk QuEChERS liquid extraction with acidified ACN-EDTA in presence of magnesium sulfate and sodinm acetate for removal of water and proteins centrifugation and filtration of organic phase and dilution of extracts 63... 

S, Q, IP, N Chicken muscle QuEChERS liquid extraction with 1% (v/v) acetic acid/ACN and sodium sulfate, followed by d-SPE clean-up with a Bondesil-NH2 sorbent (plus additional strong cation exchange clean-np with Bond Elnt SCX cartridges for NMZs) 15... 

Pinto CG, Laespada MEF, Martin SH, Ferreira AMC, Pavon JLP, Cordero BM, Simplified QuEChERS approach for the extraction of chlorinated compounds from soil samples, Talanta 2010 81 385-391. 

Recent Developments in QuEChERS Methodology for Pesticide Multiresidue Analysis... 

QuEChERS, which stands for Quick, Easy, Cheap, Effective, Rugged, and Safe, is one of those new-generation sample preparation methods for pesticide multiresidue analysis [1]. Although very recently introduced (development between 2000-2002, publication in 2003), the method has been widely embraced by the international pesticide residue analysts community and is already being used in numerous laboratories worldwide [2-6]. Aiming to deliver an economical and... 

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. 

Table I. Grouping of plant products for QuEChERS sample preparation.

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