Ft-Ir Spectroscopy Study of the Interactions of Selenium Species with Living Bacterial Cells: Analytical Applications

A method is proposed for the determination of selenium species by using living bacterial cells as an extractant and Fourier transform infrarred (FT-IR) spectroscopy. The extraction medium consists of a strain (K-12) cultivated in a culture medium based on glucose contaminated with selenium species. Firstly, equilibrium between the analyte in the solution and the retention medium is allowed to be established, and then interactions of selenium species with living bacterial cells are characterized by performing FT-IR spectroscopy of whole cells. The presence of the toxicants at various concentrations in the culture medium have an affect on the FT-IR spectra and the concentration of the selenium species is determined directly in the biomass by FT-IR spectroscopy. The relative intensities of several peaks, which vary as a function of the selenium species concentration, are used as the analytical signal. The best detection limits for the organoseleno compounds at their optimum extraction times are of 0.5-1.5 ng ml for seleno-methionine (Se-Met) and 1.0-2.6 ng ml for seleno-ethionine (Se-Et) depending on the intensity ratio used. The relative standard deviations of the retention/determination process are about 5.0% for all the selenium species tested.