Methanearsonates

Monosodium methanearsonate (MSMA) [2163-80-6] CH AsONaOOH, disodium methanearsonate (DSMA) [144-21-8], CH2AsO(NaO)2, cacodyhc acid [75-60-5], (CH2)2AsOOH, and arsenic acid [7778-39-4], H AsO, are used ia agriculture appHcations (11,12). MSMA, DMSA, and cacodyUc acid are used as herbicides (qv) especially ia cotton (qv) fields for the control of Johnson and nutsedge grass and other weeds. Arsenic acid (13) and cacodyhc acid may be used as a desiccant for the defoHation of the cotton boU prior to harvesting. Calcium arsenate [7778-44-1], Ca2(As0 2> once an important chemical for the control of the boU weevil and cotton worm, has disappeared from appHcation and the use of lead arsenate [7784-40-9], Pb AsO, for fmit crops is currentiy restricted. 

Marine algae transform arsenate into nonvolatile methylated arsenic compounds such as methanearsonic and dimethylarsinic acids (Tamaki and Frankenberger 1992). Freshwater algae and macrophytes, like marine algae, synthesize lipid-soluble arsenic compounds and do not produce volatile methylarsines. Terrestrial plants preferentially accumulate arsenate over arsenite by a factor of about 4. Phosphate inhibits arsenate uptake by plants, but not the reverse. The mode of toxicity of arsenate in plants is to partially block protein synthesis and interfere with protein phosphorylation — a process that is prevented by phosphate (Tamaki and Frankenberger 1992). 

Porter 1989). It is speculated that these deer licked trees injected with Silvisar 550, which contains monosodium methanearsonate, probably because of its salty taste (Mathews and Porter 1989). Snowshoe hares (Lepus sp.) appear to be especially sensitive to methylated arsenicals hares died after consuming plants heavily contaminated with monosodium methanearsonate as a result of careless silviculture practices (Hood 1985). 

Dimethylarsinic acid is the major metabolite of orally administered arsenic trioxide, and is excreted rapidly in the urine (Yamauchi and Yamamura 1985). The methylation process is true detoxification, since methanearsonates and cacodylates are about 200 times less toxic than sodium arsenite (NAS 1977). The marmoset monkey (Callithrix jacchus), unlike all other animal species studied to date, was not able (for unknown reasons) to metabolize administered As+5 to demethylarsinic acid most was reduced to As+3. Only 20% of the total dose was excreted in urine as unchanged As+5, and another 20% as As+3. The rest was bound to tissues, giving distribution patterns similar to arsenite (Vahter and Marafante 1985). Accordingly, the marmoset, like the rat, may be unsuitable for research with arsenicals. 

Methanearsonic acid Calves were anorexic in 3-6 days when fed diets containing 5... 

Methanearsonic acid Fed diets containing 30 mg/kg for 90 days with no ill effects 5... 

Naqvi, S.M. and C.T. Flagge. 1990. Chronic effects of arsenic on American red crayfish, Pmcambarus clarkii, exposed to monosodium methanearsonate (MSMA) herbicide. Bull. Environ. Contam. Toxicol. 45 101-106. 

In a further study the oxidation of the methyl carbon of methanearsonate was associated with the oxidation of soil organic matter in a number of soils. Additions of organic matter to a Norfolk loamy sand greatly increased the decomposition of methanearsonate. In three of the soils, there was no evidence of microbiological adaptation to methanearsonate. In Norfolk loamy sand, however, increasing decomposition of methanearsonate relative to soil organic matter occurred with time of incubation. 

Thin layer chromatography was carried out on 20x20cm glass plates coated 0.25mm thick with a suitable support and dried overnight. Silica gel G, silica gel H and cellulose were examined as the solid phases for chromatography of methanearsonate, arsenite and arsenate. Several sprays for the visualization of the arsenicals on plates were tested. Three of the more successful reagents and the colour produced with final product are shown in Table 13.2. 

Judd, F.W. Acute toxicity and effects of sublethal dietary exposure of monosodium methanearsonate herbicide to Peromyscus leucopus (Rodentia Cricetidae), Bull. Environ. Contam. Toxicol, 22(1/2) 143-150, 1979. 

Stevens, J.T., DiPasquale, L.C., and Farmer. J.D. The acute inhalation toxicology of the technical grade organoarsenical herbicides, cacodylic acid and disodium methanearsonic acid a route comparison, Bull. Environ. Contam. Toxicol, 21 (3) 304-311, 1979. 

Some metals, arsenic and mercury for example, may be volatilized by methylation due to activity of anaerobic microorganisms. Arsenic can be methylated by methanogenic Archaea and fungi to volatile toxic dimethylarsine and trimethylarsine or can be converted to less toxic nonvolatile methanearsonic and dimethylarsinic acids by algae [42]. 

Methanearsonic acid, disodium salt see Arsenic and arsenic compounds) Methanearsonic acid, monosodium salt see Arsenic and arsenic compounds Methotrexate... 

Disodium Arsenate Heptahydrate Disodium Ethylenebis (Dithiocarbamate) Disodium Methanearsonate Disodium Methyl Arsonate Disodium Nitrilotriacetate Distillate Flashed Feed Stocks Distillate Straight Run Disulfatozirconic Acid Dithane Sodium Arsenate Nabarn Methanearsonic Acid, Sodium Salts Medianearsonic Acid, Sodium Salts Nitrilotriacetic Acid and Salts Distillate Flashed Feed Stocks Distillate Straight Run Zirconium Sulfate Nabam... 

Methanearsonic Acid, Sodium Salts Medranearsonic Acid, Sodium Salts Carbon Monoxide Morpholine... 

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