Pesticide residues, HPLC analysis

Shibata Y, Oyama M, Sato H, et al. 1998. Simultaneous cleanup method for multi pesticide residue analysis by GC and HPLC. J Food Hyg Soc Jpn 39(4) 241-250. 

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. 

Acetone, n-hexane, acetonitrile, ethyl acetate, pesticide residue analysis grade Aluminum oxide, Aluminumoxid 90, activity 11-111, 70-230 mesh MSTM (Merck) Anhydrous sodium sulfate, sodium chloride, special grade Distilled water, HPLC grade... 

The most common and diverse approach to cleanup (and extraction of water samples) in pesticide residue analysis is SPE. Over the last 20 years, improvements and diversifications in SPE formats, sorbent types, and apparatus have made SPE a widely used approach for a variety of applications, including the analysis of pesticide residues. SPE cartridges or disks can be likened to low-resolution HPLC columns in that similar stationary and mobile phases are used. A typical particle size in SPE is 40 pm, and the plastic cartridges are generally packed with 0.1-1 g of sorbent in plastic tubes. The choice of reversed-phase, normal-phase, and ion-exchange media in SPE is very diverse, and Table 2 lists some of the more popular SPE applications for the cleanup of pesticides. 

The increased use of IV-methyl carbamate insecticides in agriculture demands the development of selective and sensitive analytical procedures to determine trace level residues of these compounds in crops and other food products. HPLC is the technique most widely used to circumvent heat sensitivity of these pesticides. However, HPLC with UV detection lacks the selectivity and sensitivity needed for their analysis. In the late 1970s and early 1980s, HPLC using post-column hydrolysis and derivatization was developed and refined with fluorescence detection to overcome these problems. The technique relies on the post-column hydrolysis of the carbamate moiety to methylamine with subsequent derivatization to a fluorescent isoindole product. This technique is currently the most widely used HPLC method for the determination of carbamates in water" and in fruits and vegetables." " ... 

Acetone, acetonitrile, dichloromethane, ethyl toluene pesticide residue analysis grade Distilled water HPLC grade Sodium chloride special grade... 

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... 

High-performance LC methods for pesticide residue analysis were first developed for nonvolatile or thermally labile compounds, such as carbamate insecticides. Because HPLC offers a simpler and/or faster approach to analysis for a wide range of other compounds, it is becoming more and more widely accepted, and its applications are steadily increasing in number. Although HPLC has been used in the analysis of OCPs and OPPs, the literature on its application in food is scarce. The methods reported have been summarized in Table 4. 

The most commonly used detector for pesticide residue analysis by LC is UV-VIS. It includes fixed wavelength and variable wavelength. Most OCPs and OPPs absorb appreciably only at wavelengths below 250 nm, the same spectral region where many solvents, solvent impurities, and matrix-derived interferences absorb. Analysis of these compounds by HPLC is still possible with very clean environmental substrates such as water. 

The first edition of Food Analysis by HPLC fulfilled a need because no other book was available on all major topics of food compounds for the food analyst or engineer. In this second edition, completely revised chapters on amino acids, peptides, proteins, lipids, carbohydrates, vitamins, organic acids, organic bases, toxins, additives, antibacterials, pesticide residues, brewery products, nitrosamines, and anions and cations contain the most recent information on sample cleanup, derivatization, separation, and detection. New chapters have been added on alcohols, phenolic compounds, pigments, and residues of growth promoters. 

E. A. Hogendoorn, C. E. Goewie and P. van Zoonen, Application of HPLC column switching in pesticide residue analysis, Fresenius , J. Anal. Chem. 339 348-356 (1991). 

A Critical Comparison of Pre-Column and Post-Column Fluorogenic Labeling for the HPLC Analysis of Pesticide Residues... 

Other early food applications included the analysis of pesticide residues in fruits and vegetables, organic acids, lipids, amino acids, toxins (e.g., aflatox-ins in peanuts, ergot in rye), and contaminants. As with pharmaceutical analysis, HPLC provides the ability to analyze for vitamin content in food... 

In the late 1970s HPLC provided an ideal tool for the analysis of pollutants and other environmental contaminants. Techniques were developed for analyzing chlorophenols, pesticide residues, and metabolites in drinking water and soil (parts per trillion) and trace organics in river water and marine sediments, and for monitoring industrial waste water and polynuclear aromatics in air. Techniques were also developed for determining fungicides and their decomposition products and herbicide metabolites in plants and animals. 

Cotterill, E. G. Byast, T. H. "HPLC of Pesticide Residues in Environmental Samples." In Liquid Chromatography in Environmental Analysis Laurence, J. F., Ed. Humana Press Clifton, NJ, 1984. 

This table illustrates one of the major impediments to the rapid assimilation of immunochemical technology into pesticide residue analysis labs. Because of the amount and variety of work involved, new method development costs may be high when compared to routine chromatographic methods. However, the low cost per run allows for rapid recovery of the initial investment with sufficiently high sample loads. For example, the cost of reagents and supplies for an ELISA for diflubenzuron was estimated to be 0.20/sample as compared with 4 for HPLC or 11 for GC (35). In addition to the lower reagent and supply costs, the major economic advantage of immunoassay is the dramatic decrease in labor costs. 

One very important area where HPLC can be employed is trace analysis, where small amounts of the compound of interest have to be analysed in the presence of a large amount of interfering matrix. Typical trace anlysis problems that can be dealt with by HPLC include the determination of drug metabolites in body fluids, the analysis of pesticide residues in environmental samples or the determination of unreacted intermediates or of by-products in various industrial products. 

In addition to laboratoiy glassware and equipment necessary fOT cleanup of the extract, traditional pesticide residue methods require expensive chromatogrsqihic instrumentation for identification and quantitation of residues. EIA methods require minimal amounts of glassware, disposable plasticware, or other supplies. Quantitative EIAs often make use of 96-well microtiter plates fOT multiple simultaneous assays of about a dozen extracts and associated reference standard. Major equipment consists of a plate reader, which automatically measures the absorbance of each well. Plate readers can be used alone or in conjunction with a personal computer, which can correlate replicate measurements, construct the calibration curve, calculate results, and provide a complete statistical analysis. Such an EIA workstation can be obtained for roughly half the cost of the GC or HPLC system typically used for pesticide residue analysis. 

To ensure the compliance with the maximum residue limits of pesticides in food and feed, robust analytical techniques with sensitive and selective techniques are required. The most serious problems in pesticide residue analysis are caused by the huge amount of coextracted matrix compounds. The well-known matrix effects in GC-MS and HPLC-MS often appear in the form of signal suppression, retention time shifting, or inexact quantitation in general. A reliable way to prevent matrix effects in pesticide residue analysis is an efficient and effective cleanup of extracts. The HTpSPE-HPLC-MS concept allows a rapid cleanup by HTpSPE for a full separation of pesticides from coextracted matrix compounds followed by HPLC-MS analysis. 

A study of residual analysis of thirty pesticides and their transformation products was based on SPE on-line with HPLC-UVD or post-column derivatization with o-phthalaldehyde (73) and fluorescence detection (FLD), according to EPA method 531.1 and others. The method allowed determination of many pesticides in river and well waters at 0.01 to 0.5 -ig/L levels195. An automatized procedure was proposed for determination... 

The successful combination of mass spectrometry with gas chromatography (GC-MS) and, subsequently, with liquid chromatography (HPLC-MS) allowed not only the determination of urea pesticides in food but also the identification of their residues at trace level. Mass spectrometry is a technique that can be used as a general detector, with cyclic scanning. The selectivity and sensibility of analysis can be enhanced using characteristic ions of the molecule, with selected ion monitoring (SIM). Urea pesticides have been determined by HPLC-MS directly (175-180), without the thermal instability problems of GC analysis. 

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