Analytical Services for Arsenic Speciation
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Total Arsenic and Arsenic Speciation in Human Biological Samples (pdf)
Arsenic Speciation in Soils and Sediments (pdf)
Trace (ppt level) Arsenic and Selenium Analysis (pdf)
Applied Speciation can perform a variety of analytical methods for arsenic speciation analysis. These methods utilize Ion Chromatography Coupled to an ICP-MS to achieve the lowest detection for different matrix types.
Introduction: Arsenic is the 20th most abundant element in the earth's crust.(1) The weathering of the 200+ arsenic-containing minerals and human activities (arsenical pesticides, leaching of wood preservatives, application of fertilizers, irrigation, dust from the burning of fossil fuels, and disposal of industrial and animal wastes) are responsible for the current levels of arsenic in the environment.(2) Different forms of arsenic have different properties and these properties can have significant impacts on the toxicity and treatment efficiency of a water system requiring investigation in the form of speciation analysis. With more stringent regulations on arsenic levels in drinking waters and industrial discharges, accurate determination of arsenic species at sub-ppb levels is a requirement. Arsenic is a tough analyte because of the interferences it faces with every analytical technique and the detection limit requirements of the environmental industry. In order to circumvent various matrix and analytical interferences, Applied Speciation employs the separation power of ion chromatography and couple it with the detection power of ICP-MS (IC-ICP-MS).
Methods for Arsenic Speciation Analysis: Aqueous samples can be analyzed by IC-ICP-MS to determine arsenite, arsenate, and methylated, and other organic forms of arsenic. The separation power of ion chromatography is extremely important for the determination of arsenic speciation in tissues. Arsenic can be present in a variety of different forms and it is not uncommon to observe more than 10 different arsenic containing species in tissue extracts. In the presence of sulfide and reducing conditions, arsenic can be present as thio-arsenic species. While these species produce false positives for inorganic arsenic in other methods, with IC-ICP-MS, it is possible to determine these different forms of arsenic.
The experience of Applied Speciation comes into play when arsenic speciation in difficult matrices is to be determined. We have developed a variety of different methods that utilize different chromatographic separation modes. These methods allow us to provide the lowest detection limits to our clients for their toughest samples. For instance, arsenic speciation in a 10,000 ppm Fe, Ca, Al and high sulfate matrix or highly saline samples (up to 3%) can be determined with ppt detection limits.
The most important variable associated with sampling for arsenic speciation analysis is to maintain sample integrity. Immediately after any sample is removed from its ambient environment the equilibrium may change inducing species conversion. Identification of proper sampling protocols cannot be identified without first understanding the environment the sample is being extracted from. Many variables can assist in identifying sample protocols including, but not limited to: other metals concentrations, redox, pH, concentration of organics, structure of environment (air, water, soil, tissue, etc.). Generic application of any sample preservation protocol for arsenic speciation analysis will ultimately result in highly biased results that will eventually cost time and money to the client.
Our experience with a variety of matrices allow us to choose sampling protocols depending on the target species and the sample environment. For arsenic speciation analysis, possible sampling methods may cryo-freezing in the field, hydrochloric acid, EDTA, and acetic acid.
If you have any questions or would like a quotation, please feel free to email us at info@appliedspeciation.com or call (206) 219 3779.
1) O'Neil, P. In Heavy metals in soils; B.J. Alloway Ed.; Blackie: Glasgow,1990; p83
2) Sandberg, G.R.; Allen, I.K. In Arsenical Pesticides; E.A. Woolson Ed.; American Chemical Society: Washington, DC, 1975; p124
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