Anions arsenate/arsenite

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... 

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)... 

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. 

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... 

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 . ... 

Slejkovec et al. [125] used HPLC-atomic fluorescence to separate and quantify the anionic arsenic compounds found in urban aerosol samples. The initial sample preparation produced aqueous extracts. These were found to contain only arsenate, although the separation worked for mixtures of arsenite, arsenate, monomethylar-sonic acid, and dimethylarsonic acid. The detection limit for arsenate was 80 pg mL . ... 

Figure 1. Chromatogram obtained with a solution of arsenate, arsenite, methylarsonic acid, dimethylarsinic acid, arsenobetaine, and arsenocholine (0.5 ng of As each species) in distilled water on a Supelcosil LC-SAX anion-exchange column (mobile phase 30 mM NH4H2PO4 with 1 % methanol at pH 3.75, injection volume 0.100 cm3, flow rate 1.5 cm3 min-l)...

Goldberg (2002) found no evidence of any competition in sorption of arsenate and arsenite on Al or Fe-oxides and montmorillonite, but only a small and apparent competitive effect of equimolar arsenate on arsenite sorption on kaolinite and illite. The minor competitive effect in this study was due to the small concentrations of arsenic which is very low for saturation site. Competition for sorption sites is evident by increasing the surface coverage of the sorbents. Arsenate prevents arsenite sorption on metal oxides when the surfaces of the sorbents are saturated by the anions (Jain and Loeppert 2000 Violante and Pigna 2002). 

The effect of other inorganic anions (sulfate, molybdate, silicate), low molecular mass organic ligands (LMMOLs, such as oxalate, malate, citrate, tartrate and succinate), and fulvic or humic acid on the sorption of arsenate and arsenite onto variable charge minerals and soils has been studied (Roy et al. 1986 Grafe et al. 2001 Liu et al. 2001 Violante et al. 2005a,b). 

Kampf N, Scheinost AC, Schultze DG (2000) Oxides minerals. In Sumner ME (ed) Handbook of soil science, CRC Press, Boca Raton (FL), F125-F168 Jain A, Loeppert RH (2000) Effect of competing anions on the adsorption of arsenate and arsenite by ferrihydrite. J Environ Qual 29 1422-1430 Jain A, Raven KP, Loeppert RH (1999) Arsenite and arsenate adsorption on ferrihydrite surface charge reduction and net OH release stoichiometry. Environ Sci Technol 33 1179-1184... 

Haywood and Riley [14] have described a spectrophotometric method for the determination of arsenic in seawater. Adsorption colloid flotation has been employed to separate phosphate and arsenate from seawater [15]. These two anions, in 500 ml filtered seawater, are brought to the surface in less than 5 min, by use of ferric hydroxide (added as 0.1 M FeC 2 ml) as collector, at pH 4, in the presence of sodium dodecyl sulfate [added as 0.05% ethanolic solution (4 ml)] and a stream of nitrogen (15 ml/minutes). The foam is then removed and phosphate and arsenate are determined spectrophotometrically [16]. Recoveries of arsenate and arsenite exceeding 90% were obtained by this procedure. 

Chanda, M., O Driscoll, K. F., Rempel, G. L., Ligand exchange sorption of arsenate and arsenite anions by chelating resins in ferric ion form I. Weak-base chieating resin Dow XFS-4195. Reactive Polym. 7,1988, 251-261. 

Ghimire, K.N., Inoue, K., Yamaguchi, H. et al. (2003) Adsorptive separation of arsenate and arsenite anions from aqueous medium by using orange waste. Water Research, 37(20), 4945-53. 

Ion exclusion chromatography has been applied to the determination of the following organic compounds and anions ozonisation products, carboxylic acids phosphate, nitrite, nitrate, silicate, bicarbonate, tartrate, malate, malonate, citrate, glycollate, formate and fumarate, arsenite, arsenate, chloride, bromide, iodide, thiocyanate and sulphate carbonate and also the cation arsenic. 

Arsenic species were preconcentrated on Zipax, a pellicular anion exchange material and separated on a column packed with high performance liquid chromatography grade strong anion exchange resin, then continuously reduced with sodium tetrahydroborate and detected by atomic absorption spectrometiy. Detection limits were 2ng for arsenite, arsenate and monomethylarsinate and lng for dimethylarsonate. 

Wine is a very complex matrix and the accurate, selective determination of species constitutes a challenge for analytical chemists. Furthermore, the speciation analysis of metals bound to biological ligands is a subject of increasing interest since complexation may reduce their toxicity and bioavailability. There is a limited number of studies concerning the speciation analysis of metals or metalloids in wines. Arsenite, arsenate, MMA, and DMA were separated in less than 10 min by means of an anion-exchange column [88], Arsenic species detection was accomplished by the direct coupling of the column effluent to an HG system and AFS was used for detection. LoDs in white wine were 0.16, 0.33, 0.32, and 0.57 ng ml-1 for As(III), DMA, MMA, and As(V), respectively. In real samples... 

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