Insecticides, HPLC analysis

Chlorinated insecticides The analysis of chlorinated pesticides in residue samples in complicated by the fact that they usually occur along with polychlorinated biphenyls (PCBs). The latter compounds occur widely in the environment due to their use as plasticizers, dye stuff additives and hydraulic oils, and both chlorinated pesticides and polychlorinated biphenyls are persistent in the environment. Since both compound classes include non-polar aromatic molecules, adsorption chromatography has been the mode of choice for the HPLC separation of these compounds. 

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." " ... 

Reversed-phase HPLC followed by post-column derivatization and subsequent fluorescence detection is the most common technique for quantitative determination of oxime carbamate insecticides in biological and environmental samples. However, for fast, sensitive, and specific analysis of biological and environmental samples, detection by MS and MS/MS is preferred over fluorescence detection. Thus, descriptions and recommendations for establishing and optimizing HPLC fluorescence, HPLC/ MS, and HPLC/MS/MS analyses are discussed first. This is followed by specific rationales for methods and descriptions of the recommended residue methods that are applicable to most oxime carbamates in plant, animal tissue, soil, and water matrices. 

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. 

Kongkiatpaiboon S, Mikulicic S, Keeratinijakal V, Greger H, Gritsanapan W. HPLC simultaneous analysis for quality assessment of Stemona curtisii roots and determination of their insecticidal activities. Ind Crop Prod 2013 43 648-53. 

Uses of HPLC include analysis of oil alcoholic beverages antioxidants, sugars and vitamins in foods pharmaceuticals polymers biochemical and biotechnology research presence of the stimulant caffeine in competing athletes and quality control of insecticides and herbicides. 

Minerals are usually analyzed by the traditional method of atomic absorption spectroscopy or with the newer induced coupled plasma analyzers. Most vitamins are analyzed by HPLC systems or colorimetric assays. Many laboratories still quantify folic acid with the use of a microbiological assay. The analysis of dietary and detergent (neutral and acid) fibers are critically important for foods and feeds, respectively. Raw materials and feeds should be examined for rodent contamination, pathogenic bacteria, molds and mycotoxins, and undesirable toxicants such as PCB, insecticides, herbicides, and heavy metals. The proper selection of ingredients will ensure the production of high-quality foods that satisfy sensory properties required for humans, and feeds that are palatable and can meet sensory properties required for domestic animals (Chapter 18). 

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