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Brooks Applied Labs has developed a proprietary method for characterizing the molecular forms of selenium in soil, sediment, industrial byproducts, and biosolids. The technology we have generated allows our clients to ascertain the fate and transport of selenium in the solid phase environment as well as to identify the efficacy of treatment systems. The molecular form of selenium will dictate the toxicity, mobility through a solid substrate, treatability, bioavailability, and bioaccessibility. Our method currently supports discrete quantitation of selenite, selenate, selenocyanate, and methylseleninic acid, as well as fractionation of reduced selenium complexes (e.g., Cd-Se, Hg-Se, and Pb-Se), elemental selenium, and non-extractable selenium compounds.

Traditionally, characterization of metals and metalloid compounds in solid substrates has been limited to generic selective sequential extraction approaches (SSE), scanning electron microscopy energy dispersive spectrometry (SEM-EDS), or synchrotron based approaches (XAFS and XANES). These analytical approaches have limitations that increase the probability of generating inaccurate data, data of limited use necessitating gross assumptions, or misidentification of molecules.

The information generated from our customized selective sequential extraction (SSE) approach is presented in the table below. Unlike most SSE approaches, the first two fractions allow for speciation analyses via ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) for discrete molecular identification and quantification. Fractions 3 and 4 target insoluble selenium species which have specific reactivity in accordance with the chemical bonds. The final fraction allows for mass balance in comparison to the total selenium concentration.

Fraction Description of Target Selenium Species
Fraction 1 Highly mobile ions (SeO4-2, MeSe(IV), SeCN)
Fraction 2 Adsorbed ions (SeO4-2, SeO3-2, SeCN, MeSe(IV))
Fraction 3 S2Se, Se0 (amorphous and crystalline)
Fraction 4 Selenides (HgSe, PbSe, CdSe, ZnSe)
Fraction 5 Non-extractable Selenium

Our proprietary method has been applied worldwide for over a decade to support selenium concerns. Our partners (clients) have been able to address problems with quantitative results instead of computer models and theories. At Brooks Applied Labs we continue to strive to generate novel preparatory and analytical approaches that meet or exceed the needs of the marketplace and the scientific community.