Selenium in water

Data on selenium in water are limited. The drinking water content is usually less than 1 )-lg/L, and seldom exceeds the 50 )-lg/L upper limit estabhshed in 1993 by the U.S. EPA (23). It may be higher in wells in seleniferous areas, and markedly higher in some river waters where irrigation drainage from seleniferous soil contains up to 2680 )-lg/L. 

Selenium is a vital microelement for people. It has dual properties. Selenium is an essential nutrient at low concentration levels and it becomes toxic at higher concentration levels. Deficiency of selenium results in weakness and hard diseases. Selenium is a building material of many hormones and ferments it neutralizes free radicals, radioactive radicals in organism. The range of selenium safety concentration in food and water is very narrow. The daily normal amount of human consumption of selenium is 10-20 p.g, maximum safe concentration of selenium in water is 5-10 p.g/1. It becomes toxic at 20-30 p.g and bigger content in different objects. 

Funk et al. [231] have demonstrated that the sensitivity of the analysis can be extended down into the femtogram range for the determination of selenium in water and biological matnces (Fig. 53). 

The recovery of selenium was satisfactory. The forms of selenium in waters are known to be selenite and selenate [7]. Selenium occurs in non-saline water at concentrations ranging from less than 0.0002 xg/l to greater than 50 xg/l. Therefore, a large sample size is necessary for analysis at lower concentration levels. 

HMSO (1987) Methods for the Examination of Waters and Associated Materials (40548). Selenium in Waters 1984 Selenium and arsenic in sludges, soils and related materials, 1985 a note on the use of hydric generator kits, London. 

Se° + Se2 ), as described previously. Analytical methods for speciation of selenium in water have been reviewed (Russeva and Havezov, 1996). 

Russeva, E. and Havezov, I. (1996) Speciation of selenium in waters - application of analytical techniques. Anal. Lab., 5, 3-12. 

Darrouzes, J., Bueno, M., Lespes, G., Holeman, M., Potin-Gautier, M. Optimisation of ICPMS collision/reaction cell conditions for the simultaneous removal of argon based interferences of arsenic and selenium in water samples. Talanta 71, 2080-2084 (2007)... 

As noted above, the principal natural sources of selenium in water are likely to be sulfides or metal oxides containing adsorbed selenium, especially Se(IV). Coal can be an additional primary source of selenium either directly through oxidation or indirectly via atmospheric precipitation following combustion. Selenium is readily oxidized during the weathering of minerals. Seleniferous ground-water areas such as those in the USA and Pakistan... 

Fig. 2.S. Determination of selenium in water by reversed-phase HPLC of 5-chloropiazselenol (content 0.8 ppb), detection UV-320 nm (nach Schwedt and Schwarz 1978, Ref. )...

Although selenium occurs naturally in the environment, it also can be released by both natural and manufacturing processes. As an element, selenium cannot be created or destroyed. However, forms of selenium can be transformed (changed) in the environment. Weathering of rocks to soil may cause low levels of selenium in water or it may cause it to be taken up by plants and naturally released into the air. Volcanic eruptions are suspected of contributing to selenium in air, and soils in the areas around volcanoes tend to have enriched amounts of selenium. 

The reaction of o-phenylenediamine derivatives with quadrivalent selenium, which affords 2,1,3-benzoselenadiazoles, has been used as a very sensitive analytical method for the detection of selenium in water, food, and animal tissue. The 2,1,3-benzoselenadiazoles have also been... 

Although it appears in Table I that the percent of analyses rejected and qualified is low, the problems are concentrated within a few species. Both laboratories appeared to have difficulty analyzing these selected parameters. The most difficult parameters appeared to be selenium in water samples (70 to 100 percent qualified) and antimony in solid samples (46 to 75 percent qualified). Other difficult parameters include silver, tin, and thallium. These parameters were not important in terms of risk at the CC/CC site. If these elements are important at other sites, special, instead of routine, analytical procedures should be requested to obtain better results. For example, for tin, thallium, and silver, furnace atomic absorption maybe more accurate and for antimony and selenium, cold vapor atomic absorption may be the method of choice. 

In areas of acid or neutral soils, the amount of biologically available selenium should steadily decline. The decline may be accelerated by active agricultural or industrial practices. In dry areas, with alkaline soils and oxidizing conditions, elemental selenium and selenides in rocks and volcanic soils may oxidize sufficiently to maintain the availability of biologically active selenium. Concentrations of selenium in water are a function of selenium levels in the drainage system and of water pH. In Colorado, for example, streams with pH 6.1-6.9 usually contain <1.0p,g Se/L,... 

The most common approach taken in utilizing the hydrides for analysis is to permit the reaction to proceed for some time, holding the volatile species in a balloon attached to the system. When the reaction is complete, the hydride is analyzed by flame atomic spectroscopy. This general method has been used to determine parts-per-billion levels of arsenic and selenium in water 165-170) and to determine antimony, arsenic, and selenium using an automated system (777). Thompson and Thomerson (772) have used a sodium borohydride solution to convert various ionic forms of arsenic, bismuth, antimony, selenium, tin. 

Trace amounts of selenium can be determined using its reaction with potassium iodine in an acid medium to liberate iodine. The liberated iodine can react with starch to form a blue colored species (570 nm) or can bleach the violet color of thionin (600 nm). This method can be used for the determination of selenium in water, soil, plant materials, human hair, and biological samples. 

Whitworth DJ, Achterberg EP, Nimmo M, Worsfold PJ (1998) Validation and in situ application of an automated dissolved nickel monitor for estuarine studies. Anal Chim Acta 377 217 de Carvalho LM, Schwedt G, Henze G, Sander S (1999) Redoxspeciation of selenium in water samples by cathodic stripping voltammetry using an automated flow system. Analyst 124 1803... 

Heterocyclcs have also been obtained by carbonylation of o/V/70-substituted nitro compounds, by using selenium in water as catalyst. This route seems to be limited by the toxicity and volatility of compounds such as H2SC and COSe. Besides 2-benzoxazolones (37) (cq. 17) [70] ... 

Angeles Quijano, M., Gutierrez, A. M., Perez Conde, M. C., and Camara, C. (1995). Optimization of flow injection hydride generation inductively coupled plasma mass spectrometry for the determination of selenium in water and serum samples./A no/. Al. Spectrom. 10(10), 871. 

Menegario, A. A., and Gine, M. E (2000). Rapid sequential determination of arsenic and selenium in waters and plant digests by hydride generation inductively coupled plasma-mass spectrometry. Spectrochim. Acta, Part B 55(4), 355—362. 

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