Sodium arsenate reduction

Selenium-induced reduction in growth and survival, and increase in liver histopathology. Effects exacerbated at 7% and 44% protein. Effects alleviated by addition of 200 mg As/kg ration as sodium arsenate, and partially alleviated by methionine dietary supplement... 

Time factors and reagent parameters are the same for As, Sb, Bi, Te, Ge, and Sn when using the modified Perkin-Elmer high sensitivity arsenic-selenium sampling system. The sodium borohydride reduction can be used for arsenic, antimony, bismuth, and tellurium as well. 

The marine facultative anaerobe bacterium Serratia marinoruhm and the yeast Rhodotoruhi rubra both methylate arsenate ion to methylarsonate, but only the latter produces cacodylic acid (258). Human volunteers who ingested 500 fig doses of As as sodium arsenite, sodium methylarsonate, and sodium cacodylate excreted these compounds in their urine (259). Of these three, approximately 75% of the sodium arsenite is methylated, while 13% of methylarsonate is methylated. Rat liver subcellular fractions methylated sodium arsenate in vitro, providing the first direct evidence for possible mammalian methylation independent of symbiotic bacteria (260). Shariatpanahi el al. have reported kinetics studies on arsenic biotransformation by five species of bacteria (261). They found that the As(V)-As(IIl) reduction followed a pattern of two parallel first-order reactions, while the methylation reactions all followed first-order kinetics. Of the five species tested, only the Pseudomonas produced all four metabolites (arsenite, methylarsonate, cacodylate, trimethylarsine) (261). 

Kusaka et al. [760] generated the gaseous hydrides of antimony(III), arsenic(III) and tin by sodium borohydride reduction. The hydrides were swept from solution onto a Porapak Q column where they were separated and detected at a gold gas-porous electrode by measurement of the respective electro-oxidation currents. Detection limits for 5ml samples were As(III) (0.2pg L ) Sn(II) (0.8pg L 1) Sb(III) (0.2pg L 1). The order of elution is hydrogen, arsine, stannane, stibine and mercury, ie the order of increasing molecular weight. 

In this method, arsine and methylarsines produced by sodium borohydride reduction are collected in n-hcptanc (-80°C) and then determined. The limit of detection for a 50mL sample was 0.2-0.4pg L 1 of arsenic. Relative standard deviations ranged from 2% to 5% for distilled water replicates spiked at the lOpg L 1 level. Recoveries of all four arsenic species from river water ranged from 85% to 100%. 

An interesting reduction of aromatic nitro compounds which uses glucose in an alkaline medium (equation 7) has received little attention. The advantages of this reaction include high yields, rapid rate and ease of product isolation from oxidation by-products. Other reagents which bring about the reduction of nitroanenes to azoxy compounds include potassium borohydride, sodium arsenate, phosphine and yellow phosphorus. Electrolytic methods have also been utilized. ... 

The German process of manufacturing this compound was complicated and eompri.sed the following principal steps (1) the conversion of ethyl chloride into ethyl sodium arsenate by treatment with sodium arsenate under pre.ssurc (2) reduction to ethyl arsenious oxide by the action of sulfurous acid (3) conversion of the ethyl araenious oxide to ethyl dichlorarsine by treatment with hydrochloric acid. 

Agemian and Cheam found that in the sodium borohydride reduction of inorganic arsenic to arsenic, concentrations from 0.5 to 1.5 M of hydrochloric acid gave the highest sensitivity both As(III) and As(V) were equivalently detected. When the hydrochloric acid concentration was increased from 2 to 6M, the sensitivity for both species decreased, particularly for As(V). Replacement of the hydrochloric acid line with a sulphuric acid line reduced the sensitivity for As(III) by about 30% and As(V) gave a sensitivity of about 50% ofAS(III). 

The hydrogenation of 4-vinylcyclohexene (46) to 4-ethylcyclohexene (47) was also reported to take place over a supported nickel arsenide, Ni-As(B), which was prepared by the sodium borohydride reduction of nickel arsenate supported on either silica 2,83 or alumina. " These catalysts, however, fimction best in the presence of additives. When the reaction was run in pentane at 125 C and 25 atmospheres of hydrogen in the presence of a small amount of acetone, the product mixture at 96% conversion was 96% 4-ethylcyclohexene (47) and 4% ethylcyclohexane (48). No isomeric olefins were detected. " ... 

Figure 3. Reciprocal of the rate (M/min) of glycerophosphate dehydrogenase-catalyzed reduction of dihydroxyacetone in the presence of 5 mM arsenate vs the reciprocal of enzyme concentration (mg/mL). Reactions were carried out in Tris buffer (20 mM, pH 8.0) containing NADH (0.1 mM), dihydroxyacetone (50 mM), glycerophosphate dehydrogenase and sodium arsenate (5 mM). The decrease in absorbance at 340 nm was monitored versus time.

Reduction of Iron Thermite Reaction Sodium Arsenate and Silver Nitrate Solubility Rules... 

Arsenates are not officially recognised in pharmacy, those in use are iron arsenate (see Iron Salts) and anhydrous sodium arsenate, Na2HAs04, Mol. Wt. 185 9. The latter is assayed by reduction to arsenite with hydrio-dic acid in the presence of a high concentration of hydrochloric or sulphuric acid to prevent reversal of the reaction. 

To about 0-35 g of sodium arsenate add 20 ml of water and 5 ml of concentrated sulphuric acid, followed by 2 ml of 01N iodine and 0 2 g of finely-powdered amorphous phosphorus. Heat the mixture to boiling-point and maintain at this temperature until reduction is complete (approximately three minutes) and the solution is colourless. Filter the mixture whilst still warm through a Gooch crucible and wash the residue with three portions of 10 ml of water. Nearly neutralise the solution with strong alkali and titrate with 0-lN iodine after the addition of excess sodium bicarbonate. 

A flow-injection system with electrochemical hydride generation and atomic absorption detection for the determination of arsenic is described. This technique has been developed in order to avoid the use sodium tetrahydroborate, which is capable of introducing contamination. The sodium tetrahydroborate (NaBH ) - acid reduction technique has been widely used for hydride generation (HG) in atomic spectrometric analyses. However, this technique has certain disadvantages. The NaBH is capable of introducing contamination, is expensive and the aqueous solution is unstable and has to be prepared freshly each working day. In addition, the process is sensitive to interferences from coexisting ions. 

Inorganic ar senic normally occurs in two oxidation states As(V) and As(III). Arsenic (V) gives a significantly lower response than ar senic (III). For pre-reduction As(V) to the As(III) concentrated hydrochloric acid and potassium iodide/ascorbic acid reagents were used. As organoarsenic compounds do not react with sodium tetrahydi oborate, they were decomposed with a mixture of HNO and on a hot plate. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Nakashima et al. [719] detail a procedure for preliminary concentration of 16 elements from coastal waters and deep seawater, based on their reductive precipitation by sodium tetrahydroborate, prior to determination by graphite-furnace AAS. Results obtained on two reference materials are tabulated. This was a simple, rapid, and accurate technique for determination of a wide range of trace elements, including hydride-forming elements such as arsenic, selenium, tin, bismuth, antimony, and tellurium. The advantages of this procedure over other methods are indicated. 

Yamamoto et al. [33] applied this technique to the determination of arsenic (III), arsenic (V), antimony (III), and antimony (V) in Hiroshima Bay Water. These workers used a HGA-A spectrometric method with hydrogen-nitrogen flame using sodium borohydride solution as a reductant. For the determination of arsenic (III) and antimony (III) most of the elements, other than silver (I), copper (II), tin (II), selenium (IV), and tellurium (IV), do not interfere in at least 30 000-fold excess with respect to arsenic (III) or antimony (III). This method was applied to the determination of these species in sea water and it was found that a sample size of only 100 ml is enough to determine them with a precision of 1.5-2.5%. Analytical results for surface sea water of Hiroshima Bay were 0.72 xg/l, 0.27 xg/l, and 0.22 xg/l, for arsenic (total), arsenic (III), and antimony (total), respectively, but antimony (III) was not detected. The effect of acidification on storage was also examined. 

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