Multiresidue analysis

In multiresidue analysis, where more analytes with a wide polarity range need to be determined, large transfer volumes are required, and consequently, the selectivity is lower. However, since the major interferences in water analysis are the polar humic and fulvic acids, removing this early eluting interference in coupled-column RPLC will also be feasible in multiresidue methodology. 

The minimum detectable level is estimated with the dinifroaniline signal-to-noise ratios (S/N). With fortification levels between 0.2 and 0.5mgkg the recovery of trifluralin from plant matrices is 70-99% with the LOD/LOQ being 0.005 mg kg according to the analytical method of the Ministry of the Environment, Japan. In multiresidue analysis by GC/NPD, the percent recoveries of pendimethalin from each crop with a fortification level of 0.25 mg kg were brown rice 70, potato 70, cabbage 80, letmce 89, carrot 84, cucumber 64, shiitake 74, apple 76, strawberry 99, and banana 99%. The LOD for each sample was 0.01 mg kg for pendimethalin. In residue analysis by GC/ECD, recoveries of the majority of dinifroaniline herbicides from fortified samples of carrot, melon, and tomato at fortification levels of 0.04—0.10 mg kg ranged from 79 to 92%. The LODs were benfluralin 0.001, pendimethalin 0.002 and trifluralin 0.001 mg kg for the GC/ECD method. ... 

Multiresidue analysis of 72 pesticides including three diphenyl ethers was carried out by GC/NPD under the following conditions column, 5% DB-5 (30 m x 0.53-mm i.d., 0.53- xm film thickness) temperature, column 100°C(1 min) increased at 5 °Cmin to 280°C (lOmin), inlet and detector 280°C gas flow rates. He 11.2mLmin H2 3.5mLmin air llOuiLmin" injection volume, 2 rL. The retention times... 

Okumura et al reported State regulatory programs for pesticide residues in food crops analyzed by the CDFA. In the multiresidue analysis of several organochlorine pesticides including diphenyl ether herbicides, bifenox, nitrofen and oxyfluorfen, HPLC has also been used. 

For detection, MS is rapidly becoming the method of choice for multiclass, multiresidue analysis owing to its many advantages, recent improvements in technology, and availability of cost-effective commercial instrumentation. Detection systems in general are continually being improved, and in combination with the improvements in chromatographic instruments and techniques, an exceptionally low limit of detection (LOD) is possible for pesticide residues. 

Nakamura Y, Tonogai Y, Sekiguchi Y, et al. 1994. Multiresidue analysis of 48 pesticides in agricultural products by capillary gas chromatography. J Agric Food Chem 42(11) 2508-2518. 

Kadenczki L, Arpad Z, Gardi I, et al. 1992. Column extraction of residues of several pesticides from fruits and vegetables A simple multiresidue analysis method. J AOAC International 75(1) 53-61. 

In contrast to liquid-liquid partitioning cleanup, which is particularly suitable for individual drugs or groups of drugs with similar chemical properties, solid-phase extraction is more appropriate for multiresidue analysis. On that account, solid-phase extraction in combination with liquid-liquid partitioning has become the method of choice in many laboratories for the purification of residues of sedatives and -blockers that may occur in biological matrices. Purification is usually accomplished on reversed-phase solid-phase extraction columns. Optimum retention of seven sedatives and carazolol on a reversed-phase solid-phase extraction column was reported when 10% sodium chloride solution was added to the acetonitrile hssue extract prior to its solid-phase extrachon cleanup (523, 524). A silica-based diol solid-phase extraction column was further suggested for efficient isolation of sedative and -blocker residues from food extracts (526). 

A multiresidue preparation technique—MSPD—has also been applied to the analysis of CAP residues in meat samples. Two fractions were collected by elution with methylene chloride and ethyl acetate. No additional purification was necessary. Diode assay detection and fluorescence detectors were recommended for the multiresidue analysis of sulfonamides, benzimidazoles, nicarbazin, furazolidone, and CAP. The percentage recoveries and linearity of the method were evaluated. The method was linear from 50 to 250 /tg/kg of CAP. Not only do the authors recommend the MSPD multiresidue procedure for HPLC analysis, but it could be associated with several detection modes, such as immuno- or receptor assays. The MSPD technique represents a new approach in the field of biological-matrix extraction and provides a great possibility for the analysis of a wide range of compounds (20). 

CG Rimkus, M Rummler, I Nausch. Gel permeation chromatography high-performance liquid chromatography combination as an automated clean-up technique for the multiresidue analysis of fats. J Chromatogr A 737 9-14, 1996. 

Multiresidue analysis has been carried out using conventional chromatographic methods, such as HPLC, gas chromatography (GC), and capillary electrophoresis. In the special case of veterinary drug residues, conventional microbiological methods can also be performed based on the inhibition of growing of bacteria promoted by the antibiotic. 

Pichon, V., L. Chen, N. Durand, F. Le Groffic, and M.C. Hennion (1996). Selective trace enrichment on immunosorbents for the multiresidue analysis of phenylurea and triazine pesticides. J. Chromatogr. A, 725 107-119. 

Pichon, V., M. Charpak, and M.C. Hennion (1998). Multiresidue analysis of pesticides using new laminar extraction disks and hquid chromatography and application to the French priority list. /. Chromatogr. A, 795 83-92. 

Pichon, V. 2000. Solid-phase extraction for multiresidue analysis of organic contaminants in water. J. Chromatogr. A 885 195-215. 

Alternatively, ionic compounds can be recovered from solution on hydrophobic sorbents using ion-pair SPE (IP-SPE). Carson [121] notes that advantages of IP-SPE over ion-suppression RP-SPE or ion-exchange SPE include selectivity, compatibility with aqueous samples and rapid evaporative concentration of eluents, and potential application to multiclass multiresidue analysis. IP reagents (e.g., 1-dodecanesulfonic acid for pairing with basic analytes or tetrabutylammonium hydrogen sulfate for pairing with... 

Its largest field of application, which will focus on this chapter, is the multiresidual analysis in biological samples. In so-called confirmatory analyses, LC-MS, or better LC-MS/MS, provides an unequivocal identification, due to the high selectivity of the MS detector. The results of Systematic Toxicological Screening Analysis (STA) or General Unknown Screening (GUS), other applications of LC-MS, needs of subsequent confirmatory analysis to be used in a court [52, 55]. 

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]). 

In the bioanalytical practice, where one or only a few target analytes must be detemtined, 20-50-imn long columns are used offering hmited chromatographic resolution. Often, only separation from the solvent front is pursued. In multiresidue analysis for enviroranental or food-safety applications, longer coluums (100-250 nun) are applied, providing far better separation. Therefore,... 

While the selection of an isotopically-labelled or analogue internal standard is relatively easy in quantitative bioanalysis, the situation is more complicated in multiresidue analysis. It is difficult to select appropriate analogue standards for a wide variety of target compounds, while isotopically-labelled standards are often not available for all target compounds. In addition, if one would introduce one standard per target compound, this would seriously limit the sensitivity of the method as it doubles the number of SRM transitions that have to be monitored. Another problem in multiresidue analysis is the selection of appropriate blanks for the production of the matrix-matched standards and the number of matrices that might have to be studied. When no adequate blank matrix is available, the standard addition method is the only way to achieve sufficiently accurate and precise results [123]. This method is time-consuming and labourious. 

Thurman and Ferrer [109, 135-137] recently promoted the use of oa-TOF-MS in the multiresidue analysis and identification of pesticides and their metabolites and degradation products in fraits and vegetables. 

D. Ortelli, P. Edder, C. Corvi, Multiresidue analysis of 74 pesticides in fruits and vegetables by LC-ESI-MS-MS, Anal. Chim. Acta, 520 (2004) 33. 

Matrix effects ate not only relevant in qnantitative bioanalysis, but in any other application area of LC-MS as well. As long as the method concerns the analysis of a limited number of target compounds, strategies outlined above can be apphed to monitor and reduce matrix effects. The situation is more complicated when multiresidue analysis must be performed, targeted either on a large number of known analytes or even unknown analytes. Two examples are given here. 

Becker et al. [94] evaluated matrix effects in the multiresidue analysis of 15 penicillins and cephalosporins in bovine muscle and kidney tissue and in milk. Comparison of the responses between standard solution and post-extraction spiked samples for all compounds in all three matrices showed different behaviour of different analytes and in different matrices. For one target compound, cefquinone, the standard addition method had to be apphed to get sufficiently accurate and precise results. 

Figure 12.1 Representative chromatogram of a multiresidue analysis of a spiked blood sample containing sirolimus, tacrolimus, CsA, and ritonavir (IS). Reprinted from [15] with permission. 2001, The Canadian Society of Clinical Chemists.

M. Cherlet, M. Schelkens, S. Croubels, P. De Backer, Quantitative multiresidue analysis of TC and their 4-epimers in pig tissues by positive-ion LC-ESI-MS, Anal. Chim. Acta, 492 (2003) 199. 

K.L. Tyczkowska, R.D. Voyksner, R.F. Straub, A.L. Aronson, Simultaneous multiresidue analysis ofbetalactam antibiotics in bovine milk by LC with UV detection and confirmation byESI-MS, J. AOAC Int, 77 (1994) 1122. 

Multiresidue Analysis of Thermally Labile Sulfonylurea Herbicides in Crops by Liquid Chromatography/Mass Spectrometry... 

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. 

General LC/MS Conditions for Sulfonylurea Multiresidue Analysis. We have developed general thermospray LC/MS conditions for the purpose of separating and detecting six different sulfonylurea herbicides. These conditions can be used as a guide fra- a variety of LC/MS residue applications which may require the analysis of one or more of these herbicides. Our procedure includes GLEAN (chlorsulfuron), ALLY (metsulfuron methyl), HARMONY (thiameturon) and EXPRESS cereal herbicides, CLASSIC (chlorimuron ethyl) soybean herbicide and OUST (sulfometuron-methyl) noncrop land herbicide. (Structure 1)... 

For the six sulfonylurea herbicides included in Figure 1, we monitored the protonated molecular ion fen each herbicide in addition to one or two major fragment ions. Table 1 shows the ions selected for each of the sulfonylurea and Figure 4 shows the ion traces for each compound. The table shows two ions which are common for some of these sulfonylurea herbicides. HARMONY, ALLY and GLEAN contain the same triazine urea ion at m/z 184 while ALLY, OUST and EXPRESS contain the same sulfonamide ions at m/z 233. Selecting these common ions for quantitation will increase the overall sensitivity for multiresidue analysis. 

---