Arsenic commonly found

Of the elements commonly found in lead alloys, zinc and bismuth aggravate corrosion in most circumstances, while additions of copper, tellurium, antimony, nickel, silver, tin, arsenic and calcium may reduce corrosion resistance only slightly, or even improve it depending on the service conditions. Alloying elements that are of increasing importance are calcium especially in maintenance-free battery alloys and selenium, or sulphur combined with copper as nucleants in low antimony battery alloys. Other elements of interest are indium in anodesaluminium in batteries and selenium in chemical lead as a grain refiner ". 

The arsenic compounds most commonly found in environmental and biological materials, and in working places, are arsenite and arsenate ions [As(III) and As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsine, di- and tri-... 

In addition to the above two commonly found impurities, there are a number of other acid radical impurities which exist in pharmaceutical substances, namely arsenate, carbonate, cyanide, nitrate, oxalate, phosphate and silicate. 

Arsenic is an ancient and well-known hazard and, along with lead and mercury, is an important environmental contaminant. The inorganic form is far more toxic than organic arsenic, which is commonly found in seafood. Arsenic-contaminated drinking water is a worldwide problem that affects millions of people. Human exposure also occurs from arsenic-treated lumber. 

The SSM sample was spiked with seven different heavy metals. The concentrations of each spike were followed arsenic - 500 mg/kg, cadmium-1000 mg/kg, chromium - 1500 mg/kg, copper - 9500 mg/kg, lead - 14,000 mg/kg, nickel - 1000 mg/kg, and zinc - 22,500 mg/kg. The concentrations used were based on the occurrence, frequency and concentration of contaminants commonly found in Superfund soils. 

Workers come in contact with a large number of chemical substances in work areas, as does the general public. The commonly found chemical carcinogens are grouped under (1) polycyclic aromatic hydrocarbons (PAHs), (2) nitroso compounds, (3) halogenated hydrocarbons (solvents e.g., carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride), (4) inorganic metals and minerals (beryllium, cadmium, nickel, cobalt, chromium, asbestos and arsenic), and (5) naturally occurring chemical substances (aflatoxins). 

Low column recovery can also be caused by an excessively large surface area of the stationary phase in relation to the quantity of analyte, which is a common tendency in trace analysis. For example, the recovery of arsenic in the separation of arsenic(V) acid, its methylated derivatives MMA, DMA, trimethylarsine oxide (TMAO), and arsenic(lll) acid was 101-104 % in extracts from frog tissue in which arsenic was found at the milligram per kilogram level, and only 20 % in extracts from fish tissue containing arsenic in nanogram per kilogram amounts [169]. 

Arsenic Species Commonly Found in Environmental Samples... 

In nature, arsenic is widely but sparsely distributed. Exceptionally higher levels of total arsenic are commonly found in commercially available marine seafood products. These... 

Tantalum ranks about number 50 among elements found in Earth s crust. It is slighdy more common than tungsten, but less common than arsenic. Its abundance is probably about 1.7 parts per million in the earth. The element is most commonly found in the minerals columbite, tantalite, and microlite. It always occurs with niobium. 

Table 3 Arsenic species commonly found in seafood...

Arsenic is found in igneous and sedimentary rocks. The most common commercial source is as the by-product from the refining of copper, lead, cobalt, and gold ores. Although arsenic is actually a metalloid, it is grouped with metals for most environmental purposes. 

Prior to the discovery of Prussian blue, there were three blue pigments available to painters azurite [ 03(011)2(003)2], smalt (a complex cobalt and arsenic compound), and ultramarine blue, which has the complex formula of CaNa7Al6Si6024S04. Prussian blue quickly came to be valued by painters for the intensity and transparency of its color, and it is commonly found in works painted after the early 1700s. 

The following year (1956) another 400 Japanese were poisoned by soy sauce contaminated with arsenic (84). Of the 5000 cases of heavy metal ingestion reported to the American Association of Poison Control Centers in 1984, arsenic was found to be the most commonly involved (over 1200 incidents) in the poisonings (85). The medical literature remains replete with reported cases of accidental arsenic poisoning involving individuals and their families. 

Methylarsonate and dimethylarsinate are common arsenic metabolites found in most environmental compartments. They often occur together, with dimethylarsinate being the more abundant in most samples. Their joint occurrence might be... 

Trimethylarsine oxide has been reported in several marine animals, where it is almost always a trace constituent. The one exception is the fish Kyphosus sydney-anus, which has trimethylarsine oxide as the major arsenical (25). That trimethylarsine oxide is not more widespread is perhaps surprising since it is likely to be a metabolite of the same pathway producing methylarsonate and dimethylarsinate, both of which are more commonly found. Trimethylarsine oxide chromatographs rather poorly on cation-exchange columns often used for determining arsenic species, and the resultant poor detection limits for this compound may partly explain the data indicating its apparent absence in many samples. Trimethylarsine oxide is usually only rarely reported in terrestrial organisms, but more recent work (with better detection limits) has shown it to be present in various terrestrial plants and two lichen samples (26). 

Arsenosugars are the major arsenic compounds in marine algae. They chiefly comprise water-soluble dimethylarsinoyl compounds (see Fig. 2, compounds 1-4 and 6-11), although lipid-soluble derivatives (see Fig. 2, compound 5) and quaternary arsonio analogues (see Fig. 2, compounds 12-14) are also found (4). Although many arsenosugars have been identified in algae, there are only four (see Fig. 2, compounds 1-4) that are commonly found. 

The arsenic chemistry of terrestrial plants is dominated by inorganic arsenic. With few exceptions, all plant species examined so far contain either arsenite or, more usually, arsenate as their major arsenical. Methylarsonate and dimethylarsinate are also commonly found. 

The extraction efficiency of arsenic from soil and sediments is low (11,119). Because most analytical techniques for determining arsenic species are performed on water-based solutions of the analytes (extractable arsenic), the results obtained for soil and sediments represent only a small proportion of the total arsenic present. Of this extractable portion, the inorganic species arsenate and arsenite dominate (1), although methylarsonate and dimethylarsinate are also found as natural constituents in some soils (43). These four arsenicals are also commonly found in sediments or in the interstitial water (porewater) of the sediments (45,134,135), and a trimethylated arsenic species, possibly trimethylarsine oxide, has also been detected in some sediment porewater samples (135). 

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