Studies on the photochemical stability of organo phosphorus insecticides for textile mothproofing

The light stability of 0,0-diethyl-0-(4-ethylthiophenyl)phosphorothioate, a parent structure of a new class of fibre-reactive organophosphorus insectproofing agents for use on wool textiles was extensively examined. The rate of degradation of 0,0-diethyl-0-(4-ethylthiophenyl)phosphoro-thioate in polar and non-polar solution and on wool upon irradiation by simulated sunlight was investigated using high performance liquid chromatography.. The major photodegradation products in each case were correlated with the HPLC retention times of synthetically prepared compounds. The main product formed was the sulphoxide, 0,0-diethyl-O-(4-ethylsulphinylphenyl)phosphorothioate, whose insecticidal activity against the major textile pests was shown to be similar to that of the parent compound. In polar solution a polar product which could not be identified was formed. Both 4-ethylsulphinylphenol and 4-ethyIsulphony1-phenol were found on wool but not in solution. The effect of various ultraviolet stabilizers on the rate of photodegradation of 0,0-diethyl-0-(4-ethylthiophenyl)phosphorothioate was also examined. Ultraviolet absorbers of the 2-hydroxybenzophenone and 2-hydroxybenzotriazole classes conferred the best protection in each case. However, on wool typical wool dyes applied at conventional levels were also effective.

Electrochemical behaviour of the pyrethroid insecticides

A systematic study is made of the electrochemical reduction and oxidation of eighteen pyrethroid insecticides and six model compounds. In addition the electrochemical oxidation of an insecticide synergist and the reduction of an insect repellent is studied. Oxidation and reduction mechanisms were partially or fully assigned for the the electrochemical reactions. The results indicate the presence of two oxidation sites common to the majority of pyrethroids. Specific sites of electrochemical reduction are observed for a number of pyrethroids. The electrochemical respones may be applied to the selective determination of a number pf pyrethroids synergists and repellents in commercial formulations without the requirement of pyrethroids, synergists and repellents in commerical formulations without the requirement for extensive sample preparation or the use of a separation technique.