Biological interactions of selenocyanate: Bioprocessing, detection and toxicity

The selenocyanate anion, SeCN^-, has been reported in wastewater from refineries whose petroleum comes from Se-rich marine shales. A metalloid-resistant bacterium was exposed to aqueous solutions of SeCN ^- to examine the relative toxicity of SeCN^-, and the results were compared with the toxicity of selenate and selenite and another G16 metalloid oxyanion, tellurite. We also determined the volatile organo-selenium species produced by bacterial cultures amended with selenocyanate anion, and we investigated a solid phase preconcentration technique for collecting SeCN ^- from aqueous samples with different ionic strengths and subsequent detection using capillary electrophoresis. The relative toxicity of SeCN ^- is comparable to that of selenate and selenite using the metalloid-resistant bacterium LHVE as the test organism. Tellurite was more toxic at all concentrations examined than all three selenium-containing anions, SeO₄^2-, SeO₃^2-, SeCN^-. Live cultures of LHVE amended with 1 mM NaSeCN produced volatile organo-sulphides and organo-selenides that could be collected in headspace using a solid phase microextraction fibre. The bioprocessing, i.e. the reduction and methylation of SeCN^-, is similar to that of selenate and selenite by other metalloid-resistant bacteria. An aqueous 1.0 mM solution of SeCN ^- could be captured from solution on solid-phase extraction (SPE) cartridges using an aminopropyl-based stationary phase. Selenocyanate anions, slowly pumped into a wetted SPE cartridge, were trapped on the cartridge's solid phase and were subsequently eluted, thereby providing an increase in concentration above that of the original SeCN^- containing solution. Preconcentration factors of 3.9 were achieved using a mixed sodium hydroxide/methanol elution solvent and by adding NaCl to aqueous SeCN- before loading on the SPE cartridge.