Dichlorvos mixtures

Valdes-Ramirez, G., Gutierrez, M., del Valle, M., Ramirez-Silva, M. T., Fournier, D., and Marty, J.-L. (2009). Automated resolution of dichlorvos and methylparaoxon pesticide mixtures employing a Flow Injection system with an inhibition electronic tongue. Biosens. Bioelectron. 24(5), 1103-1108. 

Chemical and Physical Properties Trichlorfon is an organophosphate compound, which has an empirical formula of C4HgCl304P and a molecular weight of 257.44. It is a racemic mixture of two isomers. Trichlorfon is a pale clear, white or yellow crystalline powder, melting point 75-84°C, boiling point 100°C, vapor pressure 7.8mmHg at 20°C, and is stable at normal temperatures and pressure. At higher temperatures and pH less than 5.5, trichlorfon decomposes to form dichlorvos (0,0-dimethyl-0-(2,2-dichlorovinyl) phosphate, DDVP). It is readily soluble in chloroform and methylene chloride, and less soluble in water, benzene, and diethyl ether. 

Ethylene Oxide Mixture with not more than 12% Ethylene Oxide Dichlorvos 2783 55... 

A mixture of equimolar concentrations of chlorpyrifos, diazinon, dichlorvos, malathion and parathion (which sum to the plotted concentrations) was analyzed by this assay using the bromine oxidation protocol. Shown in Figure 7 are the inhibition profiles for paraoxon and the previously described mixture. Over a limited concentration range (i.e., 0.1 nM and above), the inhibition profile of the mixture is similar in shape to the paraoxon curve with paraoxon showing greater inhibition than the mixture. At concentrations below 0.1 nM, the curve deviates from its typical shape and the mixture appears to inhibit to a greater extent than paraoxon. This feature in the inhibition profile (i.e., the plateau in the activity at about 80% of maximum at low compound concentrations) was also observed with chlorpyrifos-oxon (see Figure 5). 

A very specialized application of enzyme-based biosensor arrays has been reported for the resolution of pesticide mixtures containing dichlorvos and methylparaoxon, with a three-element array and a flow injection system [41]. The screen-printed, amperometric electrode array was modified with three acetylcholinesterase enzyme variants, one from electric eel and two from Drosophila (fruit fly) mutants, and were used to measure signal inhibition in conjunction with an artificial neural network. Good results down to the low uM range of pesticide concentrations were reported. 

Valdes-Ramirez G, Gutierrez M, del Valle M, Ramfrez-SUva MT, Fournier D, Marty J-L (2009) Automated resolution of dichlorvos and methylparaoxrai pesticide mixtures employing a flow injection system with an inhibition electrraiic tongue. Biosens Bioelectron 24 1103-1108... 

The first work in the literature named as inhibition BioET was a collaborative work between our laboratory and a French laboratory commanding pesticide analysis. In this work, the BioET was developed, employing an array of inhibition biosensors and ANNs [15]. The array of biosensors was formed by three ampero-metric pesticide biosensors that used different AChE enzymes the wild type from electric eel (EE) and two different genetically modified enzymes (B1 and B394). The system was employed for the simultaneous determination and/or resolution of mixtures of two pesticides, dichlorvos and carbofuran, with mean values of... 

Later, these concepts were translated into an automated flow-injection system, now using dichlorvos and methylparaoxon pesticide mixture, a more difficult to resolve mixture than the previous ones, given both pesticides are from the same family of organophosphates [16]. Figure 25 displays the performance of the developed device, where it can be observed how dichlorvos can be determined down to the 10 nM level and methylparaoxon down to 200 nM level, both with satisfactory comparison between calculated and expected values (especially for the external test set). 

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