Fluorescent pesticides, naturally

The main drawback with pesticides is that only a limited number are naturally fluorescent. The procedure is usually straightforward for fluorescent pesticides and measurements can be made immediately after separation. But for those that are not fluorescent, physical, chemical or biochemical treatments are required. 

Mallet, V., Surette, D., Brun, G.L. (1973). Detection of naturally fluorescent pesticides on silica gel layers. J. Chromatogr. 79 217-22. 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

K)°C, 45 min Induction of fluorescence in weakly pg] fluorescent or nonfluorescent pesticides and amplification of natural fluorescence. There are some differences between basic and acidic aluminium oxide layers. 

Pesticides, e.g. dursban, azinphos-methyl, menazon, imidan, phosalone, zinophos 200-225°C, 20-120 min Induced fluorescence or amplification of natural fluorescence detection limits 10-300 ng. [20]... 

Organophosphorus pesticides, e.g. coumaphos, menazon, maretin, dursban 200 °C, 45 min Induced fluorescence or amplification of natural fluorescence, detection limits 1-80 ng. [21]... 

Amplification of the natural fluorescence of some pesticides and bathochromic shift of the excitation and emission maxima detection limits 5-100 ng. 

Note A range of pesticides can be detected on cellulose layers using 3-hydroxyflavones without prior bromination. Thus, the natural fluorescence of robinetin or fisetin, which is weak in a non-polar environment, is significantly enhanced by the presence of polar pesticides [2, 5, 7, 8],... 

Fluorescence and Ultraviolet Absorbance of Pesticides and Naturally Occurring Chemicals in Agricultural Products After HPLC Separation on a Bonded-CN Polar Phase... 

For purposes of this symposium, I have limited myself to still another of these approaches. That approach includes extraction, separation by HPLC, and direct measurement of the relatively high natural fluorescence inherent in the molecular structure of the pesticides themselves. You will find that solvent polarity and instrumental parameters are important variables when I attempt to contrast the chromatograms obtained in the absorbance mode with those obtained in the fluorescence mode. 

A fluorescence monitor can conveniently confirm and support data obtained with an absorbance detector. However, any comparison of the relative sensitivity/selectivity of the absorbance mode vs the fluorescence mode depends on the spectrochemical nature of both the pesticide itself, and the co-extracted co-elutants found in the agricultural product extracted. A judicious selection of mobile phase is required to optimize separation of the pesticide and co-extractives on a CN-bonded polar stationary phase. 

Pesticides Possessing Native Fluorescence. The number of pesticides that possess enough natural fluorescence to enable their quantitative determination directly on thin-layer chromatograms is rather limited. Typical examples are given in Table X which includes their spectral characteristics [9]. With the exception of diphacinone, most fluoresce in the blue region of the spectrum. The limit of detection for each compound is in the low nanogram per spot range. 

Normally, the chiral pollutants in the environment occur at low concentrations and therefore a sensitive detection method is essential and is required in chiral CE. The most commonly used detectors in the chiral CE are UV, electrochemical, fluorescence, and mass spectrometry. Mostly, the detection of the chiral resolution of drugs and pharmaceutical in CE has been achieved by a UV mode and therefore the detection of the chiral pollutants may be achieved by the same method. The selection of the UV wavelength depends on the type of buffer, chiral selector, and the nature of the environmental pollutants. The concentration and sensitivity of UV detection are restricted insofar as the capillary diameter limits the optical path length. It has been observed that some pollutants, especially organochloro pesticides, are... 

Argauer, R.J. (1980), Fluorescence and ultraviolet absorbance of pesticides and naturally occurring chemicals in agricultural products after HPLC separation on a bonded-CN polar phase. Am. Chan. iV -, Symp. See. 1980-Vol. Pen. Anal. Methadai. 136, 103-126,... 

A. Karcher and Z. El Rassi, Electrically driven microseparation methods for pesticides and metabolites IV. Effects of the nature of fluorescent labels on the enantioseparation of pesticides and their degradation products by capillary zone electrophoresis with UV and laser-induced fluorescence detection. Electrophoresis, 21,2043-2050, 2000. 

PCBs were first manufactured commercially in 1929. Because of the insulating capacity and flame retardant nature of PCBs, they were widely used as coolants and lubricants in transformers and electrical equipment. PCBs were also commonly used in the formulation of a great variety of common products such as plastics, paints and varnishes, pesticides, carbonless copy paper, adhesives, sealants, newsprint, fluorescent light ballasts, and... 

Some parameters affect the conversion of nonflu-orescent compounds into fluorescent ones, e.g., UV irradiation time and the nature of the solvent used (see Table 1). For example, pesticides such as fenvalerate, diflubenzuron, and deltamethrin are efficiently converted into fluorescent products (high signal with short irradiation time) in protic solvents, while for fenitrothion and chlorpyriphos polar apro-tic solvents are the choice. Comparing the analytical performances of the photoconversion method with other derivatization approaches, it can be considered a rapid, sensitive, and precise method for quantifying several classes of pesticides in stationary media and as postcolumn detection mode in HPLC and in FIA. 

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