Element speciation

Speciation of redox-sensitive elements and ionic complexes in solutions, biological materials and solid samples are routinely determined for elements such as As, Se, Cr, Hg, Sn and others using appropriate extraction procedures and analytical methods.

Arsenic:

In simple aqueous matrices, total As (using FI-UV-HGAFS), arsenite, arsenate, monomethyl arsenic acid (MMA) and dimethylarsinic acid (DMA) are determined using HPLC-HGAFS. In complex liquid matrices (milk, serum, plasma), total As is determined after microwave digestion using ICP-MS or FI-HGAFA. Other species are determined in ultra filtrates using HPLC-HGAFS. In biological samples (food, animal tissues, plants, hair, blood), all above mentioned species are determined in extracts. Further, arsenobetaine (AsB), arsenocholine (AsC), tetramethylarsonium ion (TETRA) and trimethylarsine oxide (TMAO) are determined using HPLS-UV-HGAFS.

In soils and sediments, following species can be determined:

  • non-specifically sorbed As (extractable with 0.05 M (NH4)2SO4) and specifically sorbed arsenic (extractable with 0.05 M (NH4)H2PO4),
  • as associated with amorphous and poorly crystalline hydrous oxides of iron and alumimium (extractable with 0.2 M NH4-oxalate buffer) and
  • as associated with well-crystallised hydrous oxides of iron and aluminium (extractable with hot mixture of 0.2 M NH4-oxalate buffer and 0.1 M ascorbic acid).

Selenium:

In various biological samples of plant and animal origin the following selenium species; selenomethionine (SeMet), selenocysteine SeCys2, selenomethyl selenocysteine (SeMeSeCys), selenite (Se IV) and selenite (Se VI) are determined in extracts using HPLC.ICP.MS. Total Se concentrations in biological samples and their extracts are determined by various techniques: ICP-MS, HG-AFS, NAA.

Mercury:

Total mercury concentrations and mercury speciation are routinely measured in atmosphere and stack gasses (gaseous elemental Hg, gaseous oxidised Hg and Hg bound to particulate matter). In water samples (surface water, groundwater, waste water precipitation) total dissolved and dissolved elemental Hg, reactive Hg by SnCl2 and NaBH4, monomethyl-Hg by ethylation and hydration method and dimethyl-Hg can be determined. In biological samples (hair, blood, urine, fish, food) following species are analysed: total Hg by acid digestion and CV AFS/AAS, or combustion and CV AAS (DMA), total Hg by k0-NAA, monomethyl-Hg and ethyl-Hg compounds. Apart from these, temperature fractionation of Hg by CV AAS or mass spectrometry and Hg after sequential extraction followed by CV AAS detection can be determined in solid samples (sediments, ores, soils etc.).

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