Arsenate Arsenite

Spectrophotometric Methods, Phosphate, Arsenate, Arsenite, and Sulfide... 

In REACT, we prepare the calculation by disenabling the redox couple between trivalent and pentavalent arsenic (arsenite and arsenate, respectively). As well, we disenable the couples for ferric iron and cupric copper, since we will not consider either ferrous or cupric species. We load dataset FeOH+.dat , which contains the reactions from the Dzombak and Morel (1990) surface complexation model, including those for which binding constants have only been estimated. The procedure is... 

Kit solution for the determination of toxic anions (e.g., arsenate, arsenite, azide, or cyanide) and other inorganic and organic anions with indirect UV detection... 

Cell Culture As Mass spectrometry Identification of arsenate, arsenite, monomethyl-arsonate and dimethyl-arsinate 89)... 

The important inorganic toxic compounds to be considered in the following pages are arsine, arsenic trichloride, white arsenic, arsenites and arsenates and arsenic sulphides. Metallic arsenic itself is not poisonous, and the intravenous injection of a colloidal solution of this substance has been found 8 to benefit greatly a case of bone sarcoma of the femur which did not respond to X-ray treatment. 

H. Stamm also measured the solubilities of the salts of the alkalies in liquid ammonia —potassium hydroxide, nitrate, sulphate, chromate, oxalate, perchlorate, persulphate, chloride, bromide, iodide, carbonate, and chlorate rubidium chloride, bromide, and sulphate esesium chloride, iodide, carbonate, and sulphate lithium chloride and sulphate sodium phosphate, phosphite, hypophosphite, fluoride, chloride, iodide, bromate, perchlorate, periodate, hyponitrire, nitrite, nitrate, azide, dithionate, chromate, carbonate, oxalate, benzoate, phtnalate, isophthalate ammonium, chloride, chlorate, bromide, iodide, perchlorate, sulphate, sulphite, chromate, molybdate, nitrate, dithionate, thiosulphate, persulphate, thiocyanate, phosphate, phosphite, hypophosphite, arsenate, arsenite, amidosulphonate, ferrocyanide, carbonate, benzoate, methionate, phenylacetate, picrate, salicylate, phenylpropionate, benzoldisulphonate, benzolsulphonate, phthalate, trimesmate, mellitate, aliphatic dicarboxylates, tartrate, fumarate, and maleinate and phenol. 

Csanaky, I. and Gregus, Z. (2002) Species variations in the biliary and urinary excretion of arsenate, arsenite and their metabolites. Comparative Biochemistry and Physiology C-Toxicology and Pharmacology, 131(3), 355-65. 

Aqueous extracts of soil samples Arsenic Arsenite, arsenate, monomethyl arsonate dimethylarsenite, arsenbetaine, arsenocholine, tetramethyl arsonium ion Ion exchange (both cationic and anionic) Approximately 1 jug cnT1 Hansen et al. (1992)... 

In a departure from the usual study of arsenic metabolites in mammals, Kuehnelt et at. (1997) found mainly arsenate, arsenite and dimethylarsinic acid, and traces of methylarsonic acid and arsenobetaine in ants living close to an arsenic smelter. The low total arsenic levels, about 12.6mg kg-1, in the ants was suggested as indicative of a protective mechanism which prevents the uptake of arsenic from the high ambient levels. The resistance of micro-organisms to arsenic compounds has been reviewed (Cervantes et at., 1994). 

Aggett and Kadwani [13] report the development and application of a relatively simple anion exchange method for the speciation of arsenate, arsenite, monomethylarsonic acid and dimethylarsinic acid. As these four arsenic species are weak acids the dissociation constants of which are quite different it seemed that separation by anion exchange chromatography was both logical and possible. 

Andreae [683] described a sequential volatilisation method for the sequential determination of arsenate, arsenite, mono-, di- and trimethylarsine, monomethylarsonic and dimethylarsinic acid, and... 

Tye et al.56 used hydride generation coupled to AAS to quantify organic and inorganic arsenic species in soil pore waters, after pre-concentration on a pellicular anion-exchange column. They were able to detect down to 2 ng of arsenate, arsenite, and monomethyl arsenite and down to 1 ng of dimethyl arsonate. More recently, an argon-hydrogen-entrained air flame fitted with a... 

Sulphate, peroxodisulphate, phosphate, phosphite, hypophosphite, arsenate, arsenite, chromate, dichromate, silicate, hexafluorosilicate, salicylate, benzoate, and succinate. 

If the acidity of the filtrate from 2 is reduced (to about pH 5) by just neutralizing with sodium hydroxide solution and adding dilute acetic acid, silver nitrate solution will precipitate phosphate, arsenate, arsenite, oxalate, and possibly other organic acids. 

In solutions faintly acid with acetic acid, phosphate, arsenate, arsenite, and oxalate are precipitated by AgN03 solution. 

Four arsenic species common in natural samples are arsenate, arsenite, methanearsonic acid (MMAA) and dimethylarsinic acid (DMAA). These species possess different chemical properties which affect the mobility of arsenic in natural systems. For example, methanobacteriurn form trimethyl arsine from DMAA faster than fromMMAAor arsenate 3) and arsenate and MMAA are more strongly adsorbed than DMAA on alluvial soils ( ). Transformation between the different oxidation states and species of arsenic may occur as a result of chemical or biochemical reactions (J, 2, 7, 9). Inorganic chemical... 

Adsorption processes may be particularly important in influencing species concentrations, since the arsenic present in the pore waters will probably be in equilibrium with arsenic adsorbed on solid surfaces. Arsenic in any species measured in pore waters may be only a fraction of the total amount of that species present in the sediments, the rest being adsorbed to or incorporated into particulate matter. Thus, it is important to study the sorptive characteristics of each of the arsenic species in the sediments. In the Menominee River sediments studied, the four oxygenated arsenic species (arsenate, arsenite, monomethyl arsonic acid and cacodylic acid) are often present together and competing among themselves and with phosphate for the same sorption sites. The competitive adsorptive characteristics of the species could greatly influence... 

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. 

FIGURE 23. Tracing of ultraviolet (UV), refractive index RI and graphite furnace atomic absorption (GF-AA) recordings using 95/5/6 HjO/ acetonitrile/acetic acid and 0.005 M heptanesulphonic acid as solvent A = 1 arsenate/arsenite mixture B = 1 /rg arsenobetaine C = 1 /tg arsenocholine. 

The toxicity of arsenic is well-documented. Trivalent arsenic (arsenite) is almost always more toxic than the pentavalent species (arsenate)The differential toxicity is due to their different modes of action. The primary biological targets of trivalent arsenic are thiol-containing molecules, e.g. in active sites of enzymes (see below). Arsenate, on the other hand, is better tolerated (detoxified) at low concentrations and, at higher levels, competes with phosphate, an ubiquitous biological anion. Indeed the toxicity of pentavalent arsenic in vivo may be partly due to its intracellular reduction to the trivalent form . ... 

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