Multiresidue method analysis

Chlorophenoxy acids are relatively polar pesticides which are usually determined by LC because volatile derivatives have to be prepared for GC analysis. This group of herbicides can be detected by multiresidue methods combined with automated procedures for sample clean-up, although selectivity and sensitivity can be enhanced by coupled-column chromatographic techniques (52). The experimental conditions for Such analyses are shown in Table 13.1. 

Kasprzyk-Hordern B, Dinsdale RM, Guwy AJ (2008) Multiresidue methods for the analysis of pharmaceuticals, personal care products and illicit drugs in surface water and wastewater by solid-phase extraction and ultra performance liquid chromatography-electrospray tandem mass spectrometry. Anal Bioanal Chem 391(4) 1293-1308... 

Bennett DA, Chung AC, Lee SM. 1997. Multiresidue method for analysis of pesticides in liquid whole milk. JAOACInt 80(5) 1065-1077. 

For example, in order to meet the demanding requirements of legislation such as the European Union (EU) Baby Food Directive (Directive 95/5/EC and subsequent revisions), analysts must improve on the scope and sensitivity of multiresidue methods of analysis. This Baby Food Directive, which became effective on 1 July 2002, limits residues of all pesticides to a maximum level of 0.01 mgkg There will also be a banned list of pesticides, annexed to the Directive, which will not permit the use of certain pesticides on crops intended for use in baby food production. As a consequence, food manufacturers often require residue results for raw or primary ingredients within 24 8 h of sample receipt at the laboratory. 

Sample preparation consists of homogenization, extraction, and cleanup steps. In the case of multiresidue pesticide analysis, different approaches can have substantially different sample preparation procedures but may employ the same determinative steps. For example, in the case of soil analysis, the imidazolinone herbicides require extraction of the soil in 0.5 M NaQH solution, whereas for the sulfonylurea herbicides, 0.5M NaOH solution would completely decompose the compounds. However, these two classes of compounds have the same determinative procedure. Some detection methods may permit fewer sample preparation steps, but in some cases the quality of the results or ruggedness of the method suffers when short cuts are attempted. For example, when MS is used, one pitfall is that one may automatically assume that all matrix effects are eliminated because of the specificity and selectivity of MS. 

Crops, food, and feed. The first recommended method is based on the Dutch Multiresidue Method 2 for A-methylcarbamates, which was originally developed by de Kok et The method has recently been validated by DuPont Crop Protection and Batelle, Geneva Research Centres, for the analysis of methomyl and oxamyl in dry, high-water, high-fat, and high-acid content crops and in various grape processed products. The limit of detection for each analyte is 0.003-0.005 mg kg . ... 

The European drinking water guidelines set a maximum admissible concentration of 0.10 pgL for individual pesticides and their related compounds in drinking water. The recommended methods for oxime carbamates and their metabolites in groundwater and surface water are suitable for detection limits below 0.10 pgL. The first method is the HPLC/lluorescence multiresidue method of de Kok et al The second method is an HPLC/MS/MS method of DuPont Crop Protection which is specific for oxamyl and may be applicable for the analysis of other oxime carbamates in heavily polluted waters. 

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. 

The determination of diazinon in foods is important because this chemical is used as a pesticide on plant crops and, at least in some cases, in pesticide dips for the control of parasitic infestations in animals (Brown et al. 1987 Miyahara et al. 1992). Because animals are exposed to this compound, both via pesticide dips and by ingestion of crops to which diazinon has been applied, some methods have been reported for animal products. The majority of methods, however, deal with the determination of residues in plant products. Most of the analytical methods found that describe the extraction from, and determination of, diazinon residues in various crops (plant materials) were developed as part of multiresidue methods. They are based on homogenization of the sample with an organic solvent (polar or non-polar) the isolation of the residues from this initial extract and, usually, some additional cleanup prior to the analysis of the extract by GC. The most common non-MS modes of detection exploit the... 

Jansson B, Andersson R, Asplund L, et al. 1991. Multiresidue method for the gas-chromatographic analysis of some polychlorinated and polybrominated polutants in biological samples. Fresenius Z Anal Chem 340 439-445. 

Tlie demand for reliable, sensitive, automated, fast, low-cost methods for residue analysis that are also applicable to a wide range of drugs and matrices is growing fast, especially in the field of food inspection. A universal analytical scheme that could simultaneously quantify all compounds of interest in the edible animal products, correctly identify the molecular structure of the analytes, and, at the same time, produce very few false-negative and -positive results to protect the consumer, producer and international trade, would provide the most desirable approach. A unified procedure would eliminate the need for using separate multiresidue methods to screen food commodities for potential drug residues, and combinations of suitable single- or multianalyte methods to identify and quantify residues of individual analytes. 

Multiresidue methods that present attractive performance characteristics in the analysis of anabolic hormonal-type growth promoters in meat are those reported by Lagana and Marino (453), and Hartmann and Steinhart (452). 

RT Krause. Multiresidue methods for carbamate pesticides. Emerging Strategies for Pesticide Analysis 5 99-123, 1992. 

The methods most frequently used to monitor for pesticides are high-performance liquid chromatography (HPLC) and gas chromatography (GC) (14,15). On the other hand, multiresidue analytical techniques are preferred to single-residue methods, because multiresidue methods provide the capability to determine different pesticide residues in a single analysis (12,16-18). As... 

A Di Corcia, M Marchetti. Multiresidue method for pesticides in drinking water using a graphitized carbon black cartridge extraction and liquid chromatographic analysis. Anal Chem 63 580-585,1991. 

OP compounds and carbamate are widely used as insecticides, pesticides, and warfare agents [20,21], Detection of pesticides is usually carried out by multiresidue methods (MRMs) of analysis, which are able to detect simultaneously more than one residue and have been developed mainly based on chromatographic techniques. Two groups of MRMs are used (i) multiclass MRMs that involve coverage of residues of various classes of pesticides, and (ii) selective MRMs, which concern multiple residues of chemically related pesticides (e.g., IV-methyl carbamate pesticides (NMCs), carboxylic acids, phenols, etc.). As foods are usually complex matrices all of the pre-analytical steps (matrix modification, extraction, and clean-up) are often necessary. 

Stan, H.-J. (1995a). Analysis of Pesticides in Ground and Surface Water I. Progress in Basic Multiresidue Methods. Chemistry of Plant Protection Series, Vol. 11. Berlin Springer-Verlag. 

The Food and Drug Administration [FDA] Pesticide Analytical Methods Manual QJ and the Environmental Protection Agency [EPA] Manual for Environmental Analysis (2) describe procedures that have been used for many years. Two of the commonly applied techniques are liquid-liquid partitioning and column adsorption chromatography. These approaches are used to isolate lipohilic and moderately polar residues for primary identification and quantitation with GLC. An evaluation of the number of pesticide residues that were satisfactorily analyzed by this approach was published by McMahon and Burke (3). When one looks at the data it can be seen that the highly polar and water soluble residues do not fit into the analytical scheme very well. In an attempt to rectify this problem, FDA is modifying the multiresidue method... 

Cristale, J., Lacorte, S. Development and validation of a multiresidue method for the analysis of polybrominated diphenyl ethers, new brominated and organophosphorus flame retardants in sediment, sludge and dust. J. Chromatogr. A 1305(267) (2013)... 

Jans son et al. [52] described a multiresidue method for PCA analysis in biological samples by acetone-hexane and diethylether-hexane extraction, oxidation with sulfuric acid to remove lipid, and isolation of PCAs on SX-3 Biobeads GPC. A combination of silica and activated charcoal column chromatography was then used to isolate other OCs. With diethylhexylphthalate (DEHP) as a retention indicator and (1 1) DCM/hexane as the mobile phase for GPC, PCAs were selectively removed from other persistent OCs by collecting an initial fraction that corresponded to a factor times the retention time of DEHP. All other... 

Several authors pay attention to the evaluation of matrix effects (Ch. 12.5). This runs from a statement that no matrix effects were observed in the multiresidue method, where fom components ate almost coeluting [15] (Figure 12.1), to an elaborate evaluation [16]. Holt et al. [16] extracts 10 blood samples from patients receiving either CsA or tacrohmus, but no sirolimus. The extract is evaporated to diyness and reconstituted in a solvent containing both sirohmus and the IS at a concentration equivalent to a 10-pg/l cahbrator. The peak areas of these extracts and a 10-pg/l standard sirohmus solution after LC-MS analysis were found to differ less than 1%. From this result, they deduced the absence of matrix effects. 

One of the most important analytical techniques used today is high-resolution gas chromatography (HRGC). The pesticide residues can be analyzed by specihe or multiresidue methods. When crops are treated with several pesticides, the use of a multiresidue method is preferable due the reduced cost and time of analysis. The methods of pesticides residue analysis usually present an initial step of extraction with a solvent which is not miscible with water, followed by a cleanup step and the analyte determination by gas chromatography. 

Increasing demand for screening our environment for pesticide residues has generated a need for more efficient residue methods. Multiresidue methods, or those which measure several compounds at once, are generally more efficient than single residue methods in satisfying these needs. A mass spectrometer can be used as a universal selective detector for multiresidue analysis in different sample matrices, since it is generally blind to interferences present in the sample. In addition to selectivity, use of a mass spectrometer offers structure confirmation, and in many cases, can eliminate sample cleanup steps. 

Thermospray LC/MS has been extensively used for the study of sulfonylurea herbicides (1-2). These compounds are thermally labile and can not be successfully analyzed by conventional GC/MS. Early applications of thermospray LC/MS included metabolite identification and product chemistry studies. We have recently evaluated the use of thermospray LC/MS for multi-sulfonylurea residue analysis in crops and have found the technique to meet the criteria for multiresidue methods. LC/MS offers both chromatographic separation and universal mass selectivity. Our study included optimization of the thermospray ionization and LC conditions to eliminate interferences and maximize sensitivity for trace level analysis. The target detection levels were SO ppb in crops. Selectivity of the LC/MS technique simplified sample extraction and minimized sample clean up, which saved time and optimized recovery. Average recovery for these compounds in crop was above 85%. 

A simple first strategy to recover residues for ELA is to try existing multiresidue methods, or to use solvents and solid-phase extraction media that have proven satisfactory in the first steps of more involved instrumental analyses. This approach makes the transition from instrumental methods to ELA easier for technical personnel, and it facilitates confirmatory instrumental analysis during method validation. The uncommon structure of avermectin antibiotics makes it very unlikely that the ELA would detect compounds other than an avermectin in multi-residue extracts, though this remains to be tested. The greater concerns are completeness of the extractions, efficiency and reproducibility of recoveries, and freedom from non-specific matrix effects and interference by solvents. 

Table 6.3 Characteristics of monoresidue and multiresidue methods for the analysis of pesticide residues.

The use of LC/MS and GC/MS for multiresidue methods reduces the need for a purification step of grapes and wine extracts and circumvents any possible false positive. A description of MS applications in grape and wine pesticides analysis was recently reported by Flamini and Panighel (2006). 

Jansson, C., Pihlstrom, T., Osterdahl, B.G. andMarkides, K.E. (2004) Anew multiresidue method for analysis of pesticides residues in fruit and vegetables using liquid chromatography with tandem mass spectrometric detection, J. Chromatogr. A., 1023(1), 93-104. 

Figure 9.3. Sample preparation method proposed by Wong et al. for multiresidue analysis of pesticides in wine. (Reprinted from Journal of Agricultural and Food Chemistry 51, Wong et al., Multiresidue pesticide analysis in wines by solid-phase extraction and capillary gas chromatography-mass spectrometric detection with selective ion monitoring, p. 1150, Copyright 2003, with permission from American Chemical Society.)...

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