Organic arsenicals compounds, determination

The major organic arsenic compound in the environment is dimethyl arsinate. Specific and sensitive methods for the determination of this compound are needed, since the direct atomic spectrometric method does not distinguish between different organoarsenic species... 

Inoue,Y., Kawabata, K.,Takahashi, H., and Endo, G. (1995). Determination of inorganic and organic arsenic compounds in urine using ion chromatography with ICP-MS. Bunseki Kagaku 44(3), 203. 

HPLC-ICP-MS METHODS FOR THE DETERMINATION OF INORGANIC AND ORGANIC ARSENIC COMPOUND... 

HPLC-ICP-MS Methods for the Determination of Inorganic and Organic Arsenic Compound... 

Brannon and Patrick [129] reported on the transformation and fixation of arsenic V in anaerobic sediment, the long term release of natural and added arsenic, and sediment properties which affected the mobilization of arsenic V, arsenic III and organic arsenic. Arsenic in sediments was determined by extraction with various solvents according to conventional methods. Added arsenic was associated with iron and aluminium compounds. Addition of arsenic V prior to anaerobic incubation resulted in accumulation of arsenic III and organic arsenic in the interstitial water and the exchangeable phases of the anaerobic sediments. Mobilization of... 

Since many of the above-mentioned compounds possess major anti-infectious activity in addition to their role as growth promoters, the methods of their determination in edible animal products have already been discussed in other sections of this chapter. Hence, this section concentrates on the remaining compounds within this group, namely the organic arsenicals, peptide antibiotics, quinoxaline-1,4-dioxides, and miscellaneous substances. 

Toxicity of the various arsenic compounds in mammals extends over a wide range, determined in part by unique biochemical actions of each compound, but also by absorbability and efficiency of biotransformation and disposition. Overall, arsines present the greatest toxic hazard, followed closely by arsenites (inorganic trivalent compounds). Inorganic pentavalent compounds are somewhat less toxic that arsenites, while the organic (methylated)... 

Because of the stability of most of the arsenic compounds of interest for speciation studies, nearly all work commences with homogenized, predominantly lyophylized, materials. Extraction of arsenic species from dry and finely ground samples is often performed with methanol/water/chloroform mixtures or just methanol (Luten et al., 1982 Francesconi et al., 1985 Momplaisir et al., 1991 Ballin et al., 1992 ). Methanol and phosphate buffer (1 1) extraction was applied with especially good results for methylated forms of inorganic arsenic (Arenas, 1991). Rather simple approaches are the solubilization of various types of organic materials by treatment with e.g. tetramethyl ammonium hydroxide (TMAH) at ambient temperature for the subsequent determination of inorganic arsenic and its metabolites (Stoeppler and Apel, 1984, Burow and Stoeppler, 1987) and the solubilization of As(lll) and As(V) by treatment with perchloric acid and Fe2(S04)3 at elevated temperatures with subseqent separation and determination of As(lll) and As(V) (Holak and Specchio, 1991). Some speciation procedures based on NaOH treatment will be described under Speciation procedures. 

For the determination of arsenic compounds, three major steps must be taken into consideration. The arsenic species must be extracted from the sample (unfortunately in situ determination of arsenic compounds is not possible at environmental concentrations). During the extraction step, the arsenic compounds must not change or decompose chemically. Therefore, the extraction step should be as mild as possible and almost all the arsenic present in a sample must be extracted (51). A combination of various extractants is often necessary to reach all the arsenic. Polar organic solvents or water are commonly used for these purposes. 

Volatile arsines are produced from several inorganic and organic arsenicals using the hydride generation technique (see Sec. IFF). After cryotrapping of the volatile arsines AsHs (bp. -55°C), MeAsHj (bp. 2°C), Me2AsH (bp. 36°C), and MesAs (bp. 70°C), these compounds can be detected after fractionated distillation (25). An improvement for the determination of all arsenic compounds is only possible when a chromatographic separation precedes the detection of the arsenic compounds. 

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