Fungicide determination

Environment, the cultivar, infection by other pathogens, and foliar fungicides determine seed infection by P. longicolla. Warm, wet weather favors infection of the pod... 

Mancozeb is a dithiocarbamate pesticide with a very low solubility in organic and inorganic solvent. In this work we have developed a solvent free, accurate and fast photoacoustic FTIR-based methodology for Mancozeb determination in commercial fungicides. The proposed procedure was based on the direct measurement of the solid samples in the middle infrared region using a photoacoustic detector. A multivariate calibration approach based on the use of partial least squares (PLS) was employed to determine the pesticide content in commercially available formulations. 

We studied conditions for the determination of tiametoxam (TM), the active component of the fungicide Actai a (Syngenta, Switzerland) by the method of thin layer chromatography with use of the Perkin-Elmer liquid chromatograph combined with spectrophotometric detector. The 250 mm-long and 4.6 mm in diameter steel column filled with Silasorb was used. 

These methods are employed for the detection and determination of antibiotics and substances with similar effects, like alkaloids, insecticides, fungicides, mycotoxins, vitamins, bitter principles and saponins [14]. 

The two examples of sample preparation of solids containing low concentrations of the substances of interest will be the analysis of aflatoxins in corn meal (7) and the determination of the fungicide thiabendazole in citrus fruits. It should be pointed out that the applications chosen in this section attempt to reflect a range of analyses that the analyst is likely to meet in both research and industrial laboratories. 

Figure 5,39 Structures of various fungicides used in the control of post-harvest decay in citrus fruits. Reprinted from J. Chrormtogr., A, 912, Fernandez, M., Rodriguez, R., Pico, Y. and Manes, J., Liquid chromatographic-mass spectrometric determination of post-harvest fungicides in citrus fruits , 301-310, Copyright (2001), with permission from Elsevier Science.

This far into a nitrosamine symposium it should hardly be necessary to point out that nitrosamines are technically just one of a group of Ji-nitroso compounds that also includes nitros-amides, nitrosocarbamates, nitrosoureas, etc. Or that nitrosa-table pesticides encompass all the categories just mentioned and more. Or that many diverse pesticides, including herbicides, insecticides, and fungicides have been converted to Ji-nitroso derivatives in the laboratory (a recent review contained a 3-page, probably incomplete, compilation), or that some of the Ji-nitroso compounds thus synthesized were determined to be carcinogenic in test animals or mutagenic in various assays. 

Reemtsma T, O Fiehn, G Kalnowski, M Jekel (1995) Microbial transformations and biological effects of fungicide-derived benzothiazoles determined in industrial wastewater. Environ Sci Technol 29 478-485. 

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. 

The analysis of azole compounds is becoming increasingly important. For the regulation of their residues, the multi-method Deutsche Forschungsgemeinschaft (DFG) S19 is used throughout Europe. Within the last few years, this method has been validated for many new azole fungicides in various crop matrices. The multi-residue method and the most important procedural details for the detection and determination of azole compounds are described below. Some important properties are shown in Table 1. 

Fungicidal activity was determined by the disc method and zones of inhibition were recorded by measuring the diameter (mm) of the inhibition zone. Yeast cultures (S. cerevisiae) showed growth inhibition (clear area surrounding disc) by sediment extracts from all stations when compared to control discs. HPLC analysis of sediment extracts showed more than 20 components in the migration profile of each station. Of these components, a fraction demonstrated to possess cytolytic activity in the crude extract (Ve = 24 ml) was present in all stations when compared to the migration profile of the active fraction (Figure 2). 

Hutta, M., Rybar, I., Chalanyova, M. (2002). Liquid chromatographic method development for determination of fungicide enantiomers by achiral and chiral column switching technique in water and soil. J. Chromatogr. A 959, 143-152. 

Edwards S G, Pirgozliev S R, Hare M C and Jenkinson P (2001), Quantification of trichothecene-producing Fusarium species in harvested grain by competitive PCR to determine efficacies of fungicides against Fusarium head blight of winter wheat , Appl. Environ. Microbiol., 67, 1575-1580. 

A Spectrophotometric method has been described for determining down to 2pg of this fungicide in soil based on the formation of a coloured reaction product with aniline [256],... 

The recovery of the two fungicides from peat composts and soils was measured by the addition of stock solutions to the air-dried materials and, after thorough mixing and standing for 24h, extraction with acetone as detailed above. The mean recoveries of duplicate determinations are given in Table 9.23 and are illustrated in Fig. 9.13 and 9.14. 

Work has also been done on the absorption and inactivation of organomercurials by micro-organisms that tolerate and even thrive on mercurials [26, 27]. It has been postulated that inactivation occurred by the uptake of fungicide by micro-organisms, followed by metabolic breakdown and by possible utilization of portions of the byproducts. However, whether or not biological inactivation and mercury evolution occur together has not been determined. 

Kimura and Miller [28] have also studied the decomposition of organic fungicides in soil to mercury vapour and to methyl- or ethylmercury compounds and devised methods for the determination of these compounds in the vapours liberated from the soil sample. The mixed vapours of mercury and organomercury compounds is passed successively through bubblers containing a carbonate-phosphate solution to absorb organic... 

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