Organophosphorus systems

Amine systems achieve higher uranium purity than organophosphorus systems (due to the greater selectivity of amines for uranium) and have lower extractant losses due to their lower aqueous-phase solubility. SX is applied either directly to the weakly acidic leach liquor (also known as the Purlex or Amex process, Vaal River West, South Africa) or to the strongly acidic eluate from an ion-exchange preconcentration treatment of the leach liquor (the Bufflex or Eluex process, Vaal River South, South Africa) (Nicol et al. 1987). A more modem variation (such as at Southern Cross Resources Uranium One, South Africa) is to treat the ore by pressure leaching followed by SX. 

In 1994, Nam and King (68) developed a SFE/SFC/GC instrumentation system for the quantitative analysis of organochlorine and organophosphorus pesticide residues in fatty food samples (chicken fat, ground beef and lard). In this way, SFC was used as an on-line clean-up step to remove extracted material. The fraction containing pesticide residues is then diverted and analysed by GC. 

Discovered in the late 1930s in Germany as improved poisonous insecticides, organophosphorus ChEIs were developed as chemical warfare agents (e.g. sarin, soman, and tabun) and were more recently employed in the 1995 terrorist attack in the Tokyo subway system [5]. 

Chen HH, Sirianni SR, Huang CC. 1982. Sister chromatid exchanges in Chinese hamster cells treated with seventeen organophosphorus compounds in the presence of a metabolic activation system. Environ Mutagen 4 621-624. 

Hahn T, Ruhnke M, Luppa H. 1991. Inhibition of acetylcholinesterase and butyrylcholinesterase by the organophosphorus insecticide methyl parathion in the central nervous system of the golden hamster i Mesocricetus aumtus). Acta Histochem (Jena) 91 13-19. 

Xamena N, Velazquez A, Batiste-Alentom M, et al. 1988. Genotoxicity studies with four organophosphorus insecticides using the unstable white-zeste system of drosophila melanogaster. Mutat Res 204 251-256. 

The main purpose of this work is development of small-scale and mobile dsMmposition system of these chemicals. A number of studies on decomposition of organophosphorus insecticides have been conducted [1-3]. It is well known that or nophosphorus insecticides are decomposed by hydrolysis under alkaline condition, and its meciianisms have been studied [4], Even so, relatively few papers have address the devdopment of kinetic equations for reactor desipi. In this study, we aim to get kinetic equaticms for their decomposition under alkaline condition. As organophosphtous, we used parathion, fenitrothion, diazinon, malathion and phenthoate. 

The use of SPE with porous materials such as alumina, diatomaceous earth, Horisil and silica for the cleanup of fat-soluble organochlorine pesticides in fatty foods such as meat, flsh, shellfish, milk and vegetable oils has been well documented. The choice of elution solvents is critical because relatively small amounts of lipid in the final extract can cause rapid deterioration of GC capillary columns and also contaminate the gas chromatograph. A number of workers have used a porous material in tandem with Cig to effect an improved cleanup.Di Mucchio employed a multicartridge system comprising Extrelut, silica and Cig to extract organophosphorus pesticides from oils and fatty extracts. Relatively few literature applications include the pyrethroids, but Ramesh and Balasubramanian reported a simple carbon-based SPE method for the analysis of pyrethroids in vegetable oil. 

Azinphos-methyl is unstable in basic conditions and can degrade to benzazimide, hydroxymethyl-benzazimide, mercaptomethylbenzazimide or bis(benzazimide-A/-methyl) sulfide Azinphos-methyl is an organophosphorus insecticide used to control chewing and sucking mites and insects such as aphids and scale. Azinphos-methyl has both contact and stomach action. Azinphos-methyl is a cholinesterase inhibitor and interferes with the nervous system... 

Diazaphospholes constitute the most widely investigated class of heterophospholes, the 67t-aromatic phosphorus heterocycles [1,2]. Diazaphospholes are unique in the manner that the five-membered ring incorporates one phosphorus atom. First diazaphosphole representative, i.e. 2//-[l,2,3 diazaphospholc was obtained as early as 1967 [3] and until 1980s the interest of organophosphorus chemists remained in the development of different synthetic routes and in investigating their varied reactivity due to the structural diversity within the class [4], On the basis of the relative positions of the three heteroatoms in the five-membered ring, six monocyclic diazaphosphole systems (A-F) are possible and all of them have been reported (Structure 1). 

Preston, J. S. duPreez, A. C. Solvent extraction of nickel from acidic solutions using synergistic mixtures containing pyridinecarboxylate esters. 1. Systems based on organophosphorus acids. J. Chem. Technol. Biotechnol. 1996, 66, 86-94. 

Preston, J. S. Solvent extraction of cobalt and nickel by organophosphorus acids. I. Comparison of phosphoric, phosphonic, and phosphinic acid systems. Hydrometallurgy 1982, 9, 115-133. 

L. Pogacnik and M. Franko, Optimisation of FIA system for detection of organophosphorus and carbamate pesticides based on cholinesterase inhibition. Talanta 54, 631-641 (2001). 

Whereas ligand selection for the biphasic water-organic and the induced phase separation system are somewhat limited, there is very wide array of organophosphorus... 

Smith, H.G., Jr. and R.L. Goulding. 1970. Toxicological aspects of three organophosphorus compounds (cythioate, famphur, and fenthion) in the host-ectoparasite system. Jour. Econ. Entomol. 63 1640-1646. 

---