Thiophosphate pesticides

The detection limits as substance per chromatogram zone are 1 pg for polyacrylonitrile [20] and 2-arylazo-2-nitroethane derivatives [19] and 6-100 ng for thiophosphate pesticides [16]. 

Tetrabromophthalein ethyl ester potassium salt is a pH indicator that changa from blue to yellow in the pH range 4.2-3. It is known that proteins and alkaloids fordli blue-colored salt-like adsorption compounds with this indicator that are not destroyeti by weak acids [3]. Thiophosphate pesticides and triazines possibly form similar conhi pounds. 

Parathion and Paraoxon. Again, this represents a reaction (the sulfur oxidation of a thiophosphate pesticide) that is familiar to most in the pesticide area. Unlike heptachlor epoxide, paraoxon is not a stable compound and its actual presence in a poisoned animal was very difficult to demonstrate. The oxons of other organo-phosphorothioates are not so elusive. In any event, the paraoxon metabolite is an excellent example of where an understanding of metabolic processes and their potential toxicological significance alerted scientists to the likelihood that such a metabolite existed. Many years of work with similar compounds had established that the insecticidal thiophosphates required oxidation to the P=0 form in order to inhibit the neurotrasmitter acetylcholinesterase, the biochemical basis of their toxic action. Paraoxon was eventually isolated in vivo and now consideration of the oxon is a vital part of the overall risk assessment of this group of pesticides. 

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