Trimethylarsine oxide

Main metabolites in urine after 7 months of exposure to 100 mg As/L drinking water were DMA and trimethylarsin oxide (TMAO) with minute amounts of tetramethylarsonium (TMA)... 

Trimethylarsin oxide (TMAO) 100 mg As/L in drinking water for 7 months was excreted in urine mostly unchanged with some TMA 24... 

Edmonds, J.S. and K.A. Francesconi. 1987. Trimethylarsine oxide in estuary catfish (Cnidoglanis macroceph-alus) and school whiting (Sillago bassensis) after oral administration of sodium arsenate and as a natural component of estuary catfish. Sci. Total Environ. 64 317-323. 

Arsenic compounds with one to four methyl groups attached to the arsenic atom are common constituents of marine samples. The relevant species are monomethylarsonic acid (MMA) (3), dimethylarsinic acid (DMA) (4), trimethylarsine oxide (TMAO) (5), and tetramethylarson-ium ion (TeMA) (6). Of these, MMA and DMA are readily separated... 

Chen et al. [77] studied metabolites of dimethylar-sinic acid in the urine of rats exposed to DMA in drinking water. Anion-exchange chromatography was used to monitor the increased concentrations of arsenite, DMA, trimethylarsine oxide and an unidentified compound in the urine. Results showed that DMA was demethylated to inorganic As which is achieved by the action of intestinal bacteria. 

Lehr et al. (2003) found that Mycobacterium neoaurum could demethylate MMA(III) and MMA(V) to inorganic arsenic, but not DMA(V) or trimethylarsine oxide. Their results suggest that at least some MMA(V) reductively demethylates to inorganic As(III), which is a reversal of Reaction 2.13 (see above) in the Challenger mechanism (Lehr et al., 2003), 833. Other mechanisms by which microorganisms demethylate arsenic are largely unknown (Lehr et al., 2003). Chapter 4 presents additional information on the demethylation of arsenic. 

Trimethylarsine oxide — (ChEEAsO Arsenobetaine — (ChEEAs+ChECOO-Copper acetoarsenite — CU4C4H6AS6O16 (Paris green)... 

Cullen, W.R., McBride, B.C. and Reglinski, J. (1984a) The reduction of trimethylarsine oxide to trimethylarsine by thiols a mechanistic model for the biological reduction of arsenicals. Journal of Inorganic Biochemistry, 21(1), 45-60. 

Shen, J., Wanibuchi, H Salim, E.I. et al. (2003) Liver tumorigenicity of trimethylarsine oxide in male Fischer 344 rats — association with oxidative DNA damage and enhanced cell proliferation. Carcinogenesis, 24( 11), 1827-35. 

Waters, S.B., Devesa, V., Fricke, M.W. et al. (2004b) Glutathione modulates recombinant rat arsenic (+3 oxidation state) methyltransferase-catalyzed formation of trimethylarsine oxide and trimethylarsine. Chemical Research in Toxicology, 17(12), 1621-29. 

Trimethylarsine oxide (TMAO) An organoarsenical with a composition of (CH3)3AsO (see Figure 2.2). 

Dimethyl arsenic acid yields predominantly dimethylarsine, while methylarsonic acid yields predominantly methylarsine and trimethylarsine oxide yields predominantly trimethylarsine. 

There have been few elemental speciation studies in the literature involving cation-exchange chromatography (CEC) coupled to ICP-MS. A cation-exchange column was used by Larsen et al. [57,69] for arsenic speciation in several seafood sample extracts. The chromatography was optimized for the separation of arsenocholine, trimethylarsinic, trimethylarsine oxide, inorganic As, and two unknown cationic arsenic compounds. A mobile phase of 20 mM pyridinium ion, at pH 2.65, was used to perform the separation (Fig. 10.10). 

Fig. 12.1 HPLCICPMS chromatogram of an extract from the standard reference material, after the extract was stored at 4 °C for 9 months, AB arsenobetaine, TMAsO trimethylarsine oxide, U1 and U2 unidentified arsenic species [50] (Reprinted with permission. Copyright (1994) American Chemical Society)...

Low column recovery can also be caused by an excessively large surface area of the stationary phase in relation to the quantity of analyte, which is a common tendency in trace analysis. For example, the recovery of arsenic in the separation of arsenic(V) acid, its methylated derivatives MMA, DMA, trimethylarsine oxide (TMAO), and arsenic(lll) acid was 101-104 % in extracts from frog tissue in which arsenic was found at the milligram per kilogram level, and only 20 % in extracts from fish tissue containing arsenic in nanogram per kilogram amounts [169]. 

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