Insecticides analysis

Glastrup, J. (1987) Insecticide analysis by gas chromatography in the stores of the Danish National Museum s ethnographic collection. Studies in Conservation, 32,... 

The increased use of derivatisation reactions is evident from the gradual increase in the number of publications dealing with the subject. Figure 1 shows the yearly variation in numbers of publications dealing with derivatisation in pesticide analysis over the period 1963 to 1978. While the interest in derivatisation techniques in organophosphorus insecticide analysis has remained fairly constant and a low level of activity, the OC insecticides underwent an increased period of attention from 1968-1972 which has stablized over the last few years. It is in the insecticidal carbamate and herbicide areas that an overall steady increase in the use of derivatisation reactions for quantitative and con-... 

Fig.l Insecticide analysis by the internal standard method (a) chromatogram (b) calibration curve. 1 Benzanilide (internal standard) 2 methyl-A-hydroxythioacetimidate 3 metho-myl. (From Ref. 5.)... 

Claas T.J. and Kintrup J. (1991) Pyrethroids as household insecticides analysis, indoor exposure and persistence. Fresenius J. Anal. Chem., 340, 446-453. 

PoRTMANN, J. E., Progress report on a programme of insecticide analysis and toxicity testing in relation to the marine environment. Helgolander wissenschaftliche Meeresuntersuchungen 17, 247 (1968). 

Noncatalytic Reactions Chemical kinetic methods are not as common for the quantitative analysis of analytes in noncatalytic reactions. Because they lack the enhancement of reaction rate obtained when using a catalyst, noncatalytic methods generally are not used for the determination of analytes at low concentrations. Noncatalytic methods for analyzing inorganic analytes are usually based on a com-plexation reaction. One example was outlined in Example 13.4, in which the concentration of aluminum in serum was determined by the initial rate of formation of its complex with 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone. ° The greatest number of noncatalytic methods, however, are for the quantitative analysis of organic analytes. For example, the insecticide methyl parathion has been determined by measuring its rate of hydrolysis in alkaline solutions. 

Pesticides. Chlorinated hydrocarbon pesticides (qv) are often found in feed or water consumed by cows (19,20) subsequently, they may appear in the milk, where they are not permitted. Tests for pesticides are seldom carried out in the dairy plant, but are most often done in regulatory or private specialized laboratories. Examining milk for insecticide residues involves extraction of fat, because the insecticide is contained in the fat, partitioning with acetonitrile, cleanup (FlorisH [26686-77-1] column) and concentration, saponification if necessary, and determination by means of paper, thin-layer, microcoulometric gas, or electron capture gas chromatography (see Trace and residue analysis). 

Applications. Immunoassays are used in many different disciplines, having clinical, industrial, agricultural, and environmental appHcations. This technique has made possible rapid analysis of such varied analytes as vimses, toxins, hormones, foreign proteins, dmgs, and insecticides. 

Groundwater has also been surveyed for methyl parathion. In a study of well water in selected California communities, methyl parathion was not detected (detection limit of 5 ppb) in the 54 wells sampled (Maddy et al. 1982), even though the insecticide had been used in the areas studied for over 15 years. An analysis of 358 wells in Wisconsin produced the same negative results (Krill and Sonzogni 1986). In a sampling of California well water for pesticide residues, no methyl parathion was detected in any of the well water samples (California EPA 1995). In a study to determine the residue levels of pesticides in shallow groundwater of the United States, water samples from 1,012 wells and 22 springs were analyzed. Methyl parathion was not detected in any of the water samples (Kolpin et al. 1998). In a study of water from near-surface aquifers in the Midwest, methyl parathion was not detected in any of the water samples from 94 wells that were analyzed for pesticide levels (Kolpin et al. 1995). 

Kadoum AM. 1968. Cleanup procedure for water, soil, animal, and plant extracts for the use of electron-capture detector in the gas chromatographic analysis of organophosphorus insecticide residues. Bull Environ Contam Toxicol 3 247-253. 

Vol. 6. Analysis of Insecticides and Acaricides. By Francis A. Gunther and Roger C. Blinn (out of print)... 

Furans occur widely in nature and many are important commercially. Thus alcohol (29) is used in various insecticides. The carbon atoms. joined to the ring oxygen atom are at the carbonyl oxidation level so that (29) can be made by acid-catalysed cyclisation of (30). Analysis... 

Residue analytical chemistry has extended its scope in recent decades from the simple analysis of chlorinated, lipophilic, nonpolar, persistent insecticides - analyzed in the first Si02 fraction after the all-destroying sulfuric acid cleanup by a gas chro-matography/electron capture detection (GC/ECD) method that was sometimes too sensitive to provide linearity beyond the required final concentration - to the monitoring of polar, even ionic, hydrophilic pesticides with structures giving the chemist no useful feature other than the molecule itself, hopefully to be ionized and fragmented for MS or MS" detection. 

The development of class-selective antibodies is another approach to multi-analyte analysis. The analyst may design haptens that will generate antibodies that recognize an epitope common to several compounds, as explained above for the analysis of pyrethroids by measuring PBA. Other examples of class-selective immunoassays that have been developed are mercapturates," glucuronides, pyrethroids, organophosphate insecticides, and benzoylphenylurea insecticides." ... 

Pesticides, including insecticides, herbicides, and fungicides, are widely used in agriculture, and the potential for these residues to accumulate in food has led to concern for human safety. Pesticide residues may enter food animals from environmental sources or from treated or contaminated feeds. Immunoassay development for pesticides has had major impacts for pesticide registrations, analysis of residues in foods, monitoring environmental contamination, determination of occupational exposure, and integration of pest management. 

L.H. Stanker, B. Watkins, M. Vanderlaan, R. Elhs, and J. Rajan, Analysis of heptachlor and related cyclodiene insecticides on food products, in Immunoassays for Trace Chemical Analysis, ed. M. Vanderlaan, L.H. Stanker, B.S. Watkins, and D.W. Roberts, American Chemical Society, Washington, DC, Chapter 12, pp. 108-123 (1991). 

Electrospray ionization (ESI) and APCI are the two popular API techniques that will be discussed here. The applications to the analysis of pesticides that will be discussed include imidazolinone herbicides, phenoxy acid herbicides, and A-methyl carbamate insecticides. Matrix effects with respect to quantitation also will be discussed. Eor the... 

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." " ... 

Oxime carbamates are not directly amenable to gas chromatography (GC) because of their high thermal instability, which often leads to their breakdown at the injection port or in the column during analysis. Analysis of oxime carbamates by GC with sulfur detection or flame photometric detection involves oxidation of the intact insecticides or alkaline hydrolysis to form the more volatile but stable oxime compound. Enzymatic techniques have been reported for the analysis of these compounds. Enzyme-linked immunosorbent assay (ELISA) has been used to determine aldicarb and its sulfone and sulfoxide metabolites and methomyl in water, soil, and sediment samples. 

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. 

The development of new insecticides means even more. It requires appraisal of the effect of the material on the operator in all stages of use. It involves knowledge of the amount of residue that may remain on, or in, the part of the product that is used as food for man or beast and the effect of such residue on their health. Leadership in such studies belongs to the toxicologist. The chemist, however, has a very important relation to these problems. He must supply the method for analysis and for removal of insecticidal residues. For some of the new insecticidal chemicals the entomologist has accurate information on their effect on insects. Suitable, satisfactory methods of analyses of the chemical and its residues await determination. 

Some think that efforts should be made to simplify the nomenclature and to encourage industry to do proper toxicological research and supply methods for analysis before a new compound is submitted for registration. The study of antidotes should be encouraged. It is clear that research in the health hazards as well as the benefits of insecticides must be intensified and that the efforts of different laboratories should be better coordinated. Education of industry, of handlers and operators, of the medical and public health profession, and of the public must be advanced. 

The importance of methods of analysis for new insecticides is evidenced by the fact that during the past two years industry and government have cooperated in developing methods for two of them—tetraethyl pyrophosphate and benzene hexachloride (1,2,3,4,5,6-hexachlorocyclohexane) (37, 45). 

In one procedure that has been widely used, the sample, after suitable treatment, is refluxed with sodium and isopropyl alcohol, after which the solution is diluted with water and the inorganic chloride is determined by standard methods (13, 54) The method has been adopted by the Association of Official Agricultural Chemists 29, 30) as a tentative one for technical DDT and for dusts, oil solutions, and aqueous emulsions of DDT, for use in the absence of other chlorine-containing compounds. The National Association of Insecticide and Disinfectant Manufacturers has also accepted the total-chlorine method for the analysis of these preparations 28). Essentially the same procedures have been described by Donovan 22), of the Insecticide Division of the Production and Marketing Administration, for technical DDT and various commercial DDT products containing no other compounds interfering with the chlorine determination. 

The total-chlorine method has been used extensively in the determination of spray residues of the chlorinated hydrocarbons 56). Usually the kind of insecticide applied has been known, and by means of the proper factor the chlorine values could be calculated to the insecticide originally used. This calculation is not entirely valid, as the determinations do not differentiate between the insecticide and its degradation products or other contaminants containing organic chlorine. The values obtained by the total-chlorine method are useful, however, because they indicate the magnitude of the residue and the analysis can be made in a short time with standard laboratory equipment. 

Methods utilizing characteristic physical properties have been developed for several chlorinated hydrocarbon insecticides. Daasch (18) has used infrared spectroscopy for the analysis of benzene hexachloride. By this means it is possible to determine the gamma-isomer content, as well as that of the other isomers of technical benzene hexachloride, provided the product is substantially free of the higher chlorinated cyclohexanes. 

Of the three piperonyl compounds that have received considerable commercial attention as insecticides, a method of analysis is available only for piperonyl butoxide (41). This product gives a blue color on treatment with a reagent comprising tannic acid in a mixture of phosphoric and acetic acids. Satisfactory results can be obtained in the presence of small amounts of pyrethrins, but larger amounts tend to obscure the color. A modification of the method (21) which overcomes this difficulty is the removal of the pyrethrins by saponification with alcoholic sodium hydroxide prior to carrying out the test. 

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