Arsenate, determination

SAMPLE STORAGE AND ARSENIC DETERMINATION IN NATURAL WATERS... 

It is well known that arsenic is one of the most dangerous elements in terms of its potential impacts to both to human and ecosystem health. Therefore the problem of As detection at ppb level remains very important from the point of environmental hazard investigation. The goal of the present work is the developing of very simple and inexpensive assay for arsenite and arsenate determination in environmental samples using whole-cell bacterial biosensors. 

The developed assay was successfully applied for the arsenite and arsenate determination in contaminated waters of the gold recovery plant and in snow covers of the industrial anthropogenic sources vicinities as well. The data produced are in a good agreement with the results of independent methods atomic absorptioin and atomic emission spectrometry and capillary electrophoresis. 

Arsenic, determination by x-ray emission spectrography, 328 enhancement effect on, 190 trace analysis by x-ray emission spectrography, 228, 229... 

A UK standard official method [62] has been published for the spectropho-tometric determination of arsenic in sea water. The determination is effected by conversion to arsine using sodium borohydride which is added slowly to the acidified samples by a peristaltic pump. The liberated arsine is trapped in an iodine/potassium iodide solution and the resultant arsenate determined spectrophotometically as the arsenomolybdenum blue complex at 866 nm. The method is applicable down to 0.19 p,g arsenic. 

Arsenic Arsenic determined by cathodic stripping CSV 0.3 nmol [621]... 

Table 12.15 Comparison of arsenic determination in sediments by different analytical methods (pg/g dry weight)...

Maher [130] has described a procedure for the determination of total arsenic in sediments. Arsenic is converted into arsine using a zinc reductor column, as shown in Fig. 12.8. The evolved arsine is trapped in a potassium iodide-iodine solution and other arsenic determined spectrophotometrically as an arsenomolybdenum blue complex. The detection limit is 0.024pg and the coefficient of variation is 5.1% at the 0.1 pg level. The method is free from interferences by other elements at levels normally encountered in sediments. In this method the sediments were freeze-dried and ground (to less than 200pm) before analysis. 

All four dissolution procedures studied were found to be suitable for arsenic determinations in biological marine samples, but only one (potassium hydroxide fusion) yielded accurate results for antimony in marine sediments and only two (sodium hydroxide fusion or a nitricperchloric-hydrofluoric acid digestion in sealed Teflon vessels) were appropriate for determination of selenium in marine sediments. Thus, the development of a single procedure for the simultaneous determination of arsenic, antimony and selenium (and perhaps other hydride-forming elements) in marine materials by hydride generation inductively coupled plasma atomic emission spectrometry requires careful consideration not only of the oxidation-reduction chemistry of these elements and its influence on the hydride generation process but also of the chemistry of dissolution of these elements. 

Gaseous sample introduction into an ICP-MS presents different problems. Owing to its extremely sensitive nature, Dean et al. [13] introduced the sample as the gaseous hydride by a flow-injection approach. This was reasonably effective because lower volumes of samples and reagents were in use. They utibzed nitric acid as a carrier stream to prevent the formation of argon chloride species in the plasma. Argon chloride has the same mass as arsenic which is mono-isotopic, and this severely bmits arsenic determination. An additional problem was that the sensitivity was extremely dependent on the purity of reagents. 

Another type of background correction system that has found some use is that developed by Smith and Hieftje. The Smith-Hieftje background correction technique is of especial use when there is strong molecular interference, such as that observed by phosphate on selenium or arsenic determinations. If the hollow-cathode lamp is run at its normal operating... 

M. V. Reboucas, S. L. C. Ferreira and B. De-Barros-Neto, Arsenic determination in naphtha by electrothermal atomic absorption spectrometry after preconcentration using multiple injections, J. Anal. At. Spectrom., 18(10), 2003, 1267-1273. 

J. M. Trindade, A. L. Marques, G. S. Lopes, E. P. Marques and J. Zhang, Arsenic determination in gasoline by hydride generation atomic absorption spectroscopy combined with a factorial experimental design approach. Fuel, 85(14-15), 2006, 2155-2161. 

The distillation separation procedure was the principal method used for the arsenic determinations, but more recently Santoliquido (24) has developed a method for the carrier-free separation of arsenic from low-temperature coal ash involving retention on an inorganic exchanger column. 

This method for determining arsenic is particularly useful in biological and toxicological studies.8 The material under test is oxidised with a mixture of sulphuric and nitric acids and perhydrol, the arsenic is precipitated as sulphide, which is then oxidised and the arsenic determined colorimetrically after addition of sodium molybdate and stannous chloride. The formation of the molybdenum blue compound is also applied to the micro-determination of arsenic in soil extracts.9... 

The limitations of the Gutzeit method for determining arsenic are well-known. The spectrophotometric molybdenum blue or silver diethyldithio-carbamate procedures tend to suffer from poor precision. Sandhu [34] has described a spectrophotometric method for the direct determination of hydrochloric acid-releasable inorganic arsenic in soils and sediments. The method provides reliable data on the quantitative recovery of 2.0 xg of arsenic(V) added to 5.0 g (0.4 mg/kg) of soil, clay, sand and sediment samples. The method is simple, reliable and relatively rapid 24 samples can be analysed in about an hour. It does not require elaborate equipment and can be routinely used for the quantitative determination of arsenic in soil and soil-like material. The detection limit has been established as 0.5 xg of arsenic. The extent of ionic interference when this method is used for arsenic determination in soil was also quantitatively evaluated. 

Electrochemical methods for arsenic determination were initially based on polarography with a dropping mercury electrode. More recent methods, based on anodic stripping voltammetry (ASV), anodic stripping chronopotentiometry (SC), and CSV, rely almost exclusively on the detection of As(III), since As(V) is detected with difficulty because of its perceived electro-inactivity. 

N. P. Vela, D. T. Heitkemper, Total arsenic determination and speciation in infant food products by ion chromatography-inductively coupled plasma-mass spectrometry, J. AOAC Int., 87 (2004), 244 D252. 

Arsenic Determine as directed under Arsenic Limit Test, Appendix IIIB, using a Sample Solution prepared as directed for organic compounds. 

Method II (Sample Preparation) Transfer approximately 0.2 g of sample, accurately weighed, into the titration flask. The stoichiometric factor (Fs) for Allura Red is 8.06. Arsenic Determine as directed under Arsenic Limit Test, Appendix MIR, using a Sample Solution prepared as directed for organic compounds. 

Arsenic Determine as directed under Arsenic Limit Test, Appendix IIIB, using a solution of 1 g of sample in 35 mL of water. Fluoride Determine as directed in Method /Funder the Fluoride Limit Test, Appendix IIIB, using a 2-g sample, Buffer Solution B, and 0.1 mL of Fluoride Standard Solution. 

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