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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.

A physiologically-based toxicokinetic and toxicodynamic (PBTK/TD) model was developed, from the open literature, to predict the toxicokinetic disposition and toxicodynamic response (acetylcholinesterase inhibition) of a ternary organophosphorus (OP) insecticide mixture: chlorpyrifos (CP), methyl parathion (MP) and parathion (P). In vivo studies were conducted in adult male Sprague-Dawley rats, orally administered one of two CP/MP/P mixtures (2.5, 0.5, 0.5 mg/kg or 5, 1, 1 mg/kg) with selected tissues (blood, brain, diaphragm, liver, lung and skeletal muscle) collected at 30min, 4, 12 and 24hr postdosing. Low dosages were studied so the mixture did not result in significant disruption of cardiovascular function nor invalidate the model’s underlying general physiological assumptions. The data were used to validate the model. CP and its metabolites (CP-oxon, 3,5,6-trichloro-2-pyridinol (TCP)), as well as MP, P and 4-nitrophenol, were quantified in the tissues of interest. Peak concentrations of CP were attained by 4hr in all tissues with the exception of the liver, whose peak occurred at 30min; MP, 30min in all tissues; P, 12hr in all tissues with the exception of the liver, 30min. This was supported by the model simulations. MP, P, and their respective oxons were below limits of quantitation for the lower dosage. No toxicokinetic interactions were observed in the present study. Cholinesterase inhibition in the tissues ranged from 11- 37% for the lower dosage, and 29-93% for the higher dosage group; with few exceptions, inhibition was generally additive and was also supported by the model simulations. This study demonstrates the utility of using previously developed individual PBTK/TD models and in vitro/in vivo data from the open literature to construct reliable mixture PBTK/TD models.

The use of Multi-Walled Carbon Nanotubes (MWCNT) as solid sorbent in Matrix Solid-Phase Dispersion (MSPD) extraction and preconcentration method was presented to determine some commonly used organophosphorus insecticides/OPIs in honey samples using a Gas Chromatography Flame Ionization Detector (GC-FID). OPIs are poisonous compounds used to kill insects and rodents by affecting their nervous system. The limit of detections obtained after MSPD extraction were 7.0 ng/g for Malathion, Malaoxon and Fenitrothion and 33.3 ng/g for Isomalathion. The recovery of the insecticides from spiked honey, ranged from 83.6% to 103.3% with % RSD ranged from 9.8% to 12.3% (n=3). The correlation coefficient (R2) of the calibration data varied from 0.9945 to 0.9987. Standard addition method was utilized to examine matrix-induced effects on analyte peaks, and to demonstrate the efficiency of the method. The MSPD extraction was successfully applied for the analysis of four honey samples but no insecticide residues were detected.