Baker's yeast biomass (Saccharomyces cerevisae) for selective on-line trace enrichment and liquid chromatography of polar pesticides in water

Baker's yeast cells (Saccharomices cerevisae) were successfully immobilized onto silica gel and used in the on-line isolation and trace enrichment of desisopropyl-atrazine, desethylatrazine, hydroxyatrazine, simazine, cyanazine, atrazine, carbaryl, propanil, linuron, and fenamiphos, Since humic and fulvic acids were not coextracted, no cleanup was necessary, The pesticides were spiked at 0.1-1 mu g L-1 in tap water, groundwater, and seawater and were preconcentrated using on-line solid-phase extraction into a yeast immobilized on silica gel precolumn followed by liquid chromatography with diode away detection, All the variables that affect the enrichment step, such as amount of yeast immobilized, dimensions of the precolumn, sample pH, and preconcentration flow rate, were optimized, The degree of selectivity was evaluated by comparing the chromatograms obtained after on-line sample preconcentration on the yeast precolumn with those obtained by on-line solid-phase extraction using a precolumn filled with C-18 material, The relative standard deviation for the whole procedure in the determination of the selected pesticides at the 0.3 mu g L-1 concentration level ranged from 1 to 9%, depending on the pesticide and the type of water, Detection limits within the range 0.01-0.5 mu g L-1 were obtained by percolating only 25 mL of water sample without any additional cleanup step.