Trimethylarsine gas

Museums and industrial facilities, especially, often have exotic minerals, pigments, and chemicals that release arsenic-bearing dust and vapors. In particular, mold growing on arsenic pigments in old wallpaper has been a potentially dangerous source of trimethylarsine gas in the past (Chapter 5). 

Arsenic detoxification and evolution of trimethylarsine gas by a microbial arsenite S-adenosylmethionine methyl-transferase. Proc. Natl Acad. Sci. USA 103 2075-80. 

DP Cox, M Alexander. Production of trimethylarsine gas from various arsenic compounds by three sewage fungi. Bull Environ Contam Toxicol 9 84-88, 1973. 

Cox DP, Alexander M (1973) Production of trimethylarsine gas from various arsenic compounds by three sewage fungi. Bull Environ Contam Toxicol 9 84-88 Crecelius EA (1977) Changes in the chemical speciation of arsenic following ingestion by man. Environ Health Perspect 19 147-150 Dabeka RW, McKenzie AD, Lacroix GMA, Cleroux C, Bowe S, Graham RA, Conacher HBS, Verdier P (1993) Survey of arsenic in total diet food composites and estimation of the dietary intake of arsenic by Canadian adults and children. J AOAC Int 76 14-25... 

Longwood House on Saint Helena Island, where Napoleon lived in exUe, had a particular green floral pattern. Wallpaper of that time was made vivid green by using copper arsenite (Scheele s green) in the paint. When copper arsenite becomes damp (not unlikely, considering that the house was on an island), it is converted by molds into trimethylarsine gas, and it is most likely that it was this gas, not an assassin s poison, that was the source of the arsenic found sequestered in Napoleon s hair. 

Trimethyl arsine [593-88-4] C H As, has been identified as the toxic volatile arsenical, once known as "Gosio gas," produced by the reaction of certain molds that grow on wallpaper paste and react with inorganic arsenic compounds present in the paper. A number of microorganisms can methylate arsenic trioxide and other arsenic-containing compounds to yield trimethylarsine. These microorganisms include Scopulariopsis brevicaulis Candida humicola and Gliocladium roseum (72). 

The compounds MMA, DMA, and TMAO are reduced in acidic aqueous media by borohydride solutions to methylarsine (MeAsH2, bp 2°C), dimethylarsine (Me2AsH, bp 35°C), and trimethylarsine (Me3As, bp 55°C), respectively. These products are useful derivatives for speciation analysis of arsenic because they are readily separated from complex sample matrices and may be further separated from each other by distillation (41) or by gas chromatography (42) prior to their determination by element-specific detectors. Consequently, arsine generation techniques are the most commonly used methods for determining MMA, DMA, and TMAO in marine samples. 

The gas-phase dipole moment of arsabenzene was found to be 1.10D 45). In cyclohexane solution it was measured as 1.02D27). These values are typical of those found for tertiary arsines for trimethylarsine p = 0.86D76), for triethylarsine p = 1.04D77) and for triphenylarsine p = 1.23D78). No dipole moment data are available for stibabenzene and bismabenzene. However, based on trends shown in acyclic compounds 79), it is expected that they have smaller moments. 

Gas phase proton affinities of phosphabenzene and arsabenzene have been determined by ion-cyclotron resonance techniques 94>. These confirm the qualitative solution phase data (see Fig. 5). Phosphabenzene (PA = 194.5 kcal/mol) has a proton affinity nearly 30 kcal/mol less than trimethylphosphine and only slightly greater than that of phosphine. Arsabenzene (PA = 188.0 kcal/mol) has a proton affinity 23 kcal/mol less than trimethylarsine. In the case of arsabenzene, protonation occurred on carbon rather than arsenic so the As-basidty may be even lower. By contrast, the proton affinity of pyridine (PA = 218 kcal/mol) is only slightly less than that of trimethylamine (PA = 222 kcal/mol) but considerably larger than ammonia (PA = 202 kcal/mol). 

SFC has received attention as an alternative separation technique to liquid and gas chromatography. The coupling of SFC to plasma detectors has been studied because plasma source spectrometry meets a number of requirements for suitable detection. There have been two main approaches in designing interfaces. The first is the use of a restrictor tube in a heated cross-flow nebuliser. This was designed for packed columns. For a capillary system, a restrictor was introduced into the central channel of the ICP torch. The restrictor was heated to overcome the eluent freezing upon decompression as it left the restrictor. The interface and transfer lines were also heated to maintain supercritical conditions. Several speciation applications have been reported in which SFC-ICP-MS was used. These include alkyl tin compounds (Oudsema and Poole, 1992), chromium (Carey et al., 1994), lead and mercury (Carey et al., 1992), and arsenic (Kumar et al., 1995). Detection limits for trimethylarsine, triphenylarsine and triphenyl arsenic oxide were in the range of 0.4-5 pg. 

At room temperature, methylene trimethylarsorane (73) is a colorless crystalline compound, mp 33°C, which sublimes in a vacuum at 20°C/0.1 mm Hg. It is rapidly decomposed above 33°C trimethylarsine and polymethylene are the main products formed. Blue and brown colors develop and some gas is evolved, predominantly ethylene. With trimethylphos-phine, a methylene transfer reaction takes place yielding trimethylarsine and methylene trimethylphosphorane ... 

The thermal decomposition of (CH3)5As at 100°C leads to quantitative yields of trimethylarsine, methane, and ethylene, as followed by gas chromatography. Only traces of ethane were detectable. It is, therefore, assumed that the compound is decomposed via the ylide, which is known to be unstable under these conditions ... 

FIGURE 12. Comparison of atomization efficiency curves for trimethylarsine in a silica-lined graphite furnace with and without hydrogen added to the carrier gas. Reprinted with permission from Reference 162. Copyright (1977) American Chemical Society... 

Andreae described a method for the sequential determination of arsenate, arsenite, mono-, di- and trimethyl arsine, MMAA, DMAA and trimethylarsine oxide in natural waters with detection limits of several ng/1. The arsines are volatilized from the sample by gas stripping the other species are then selectively reduced to the corresponding arsines and volatilized. The arsines are collected in a cold trap cooled with liquid nitrogen. They are then separated by slow warming of the trap or by gas chromatography, and measured with atomic absorption, electron capture and/or flame ionization detectors. He found that these four arsenic species all occurred in natural water samples. 

The basis of the second fairly simple routine method is transformation of arsenobeta-ine and arsenocholine into trimethylarsine and determination by headspace gas chromatography with a flame ionization or AAS detector. A detection limit below 10 /working conditions (Ballin et al., 1992 Ballin, 1992). 

Gas chromatography is not commonly used for the determination of arsenic compounds. The reason for this is that not all arsenic compounds are easily volatilized. A rapid method for the determination of arsine, methylarsine, dimethylar-sine, and trimethylarsine in air based on gas chromatography-mass spectrometry (GC-MS) was recently published (65). In another smdy, DMA and MA present in urine were derivatized with thioglycol methylate and extracted with a 100 qm solid-phase microextraction fiber in 40 minutes. Thereafter, the two arsenic compounds were determined with GC-MS (66). The combination of purge and trap gas chromatography with atomic fluorescence spectrometry was used for the determination of arsenous acid, arsenic acid, MA, and DMA in a mushroom sample (67). Low-temperature gas chromatography coupled to ICP-MS was used to determine the volatile arsenic compounds in intraoral air (68). This method is also applicable to the determination of volatile arsenic compounds in landtill gases. 

M Pantsar-Kallio, A Korpela. Analysis of gaseous arsenic species and stabflity studies of arsine and trimethylarsine by gas chromatography-mass spectrometry. Anal Chim Acta 410 65-70, 2000. 

Trimethylarsine has been found as a trace constituent in six prawn species and two lobster species (27). Possibly, it results from microbial breakdown of arseno-betaine via trimethylarsine oxide (18). Trimethylarsine has also been detected in landfill and sewage gases (14,16,28), and in headspace gases from hot springs environments (15,29). Methylarsine and dimethylarsine have also been detected in these gas samples. 

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