A solid-phase extraction procedure for the clean-up of thiram from aqueous solutions containing high concentrations...

A simple solid-phase extraction (SPE) procedure with an octadecyl bonded phase silica (C(18)) was developed for clean-up of the fungicide thiram from aqueous solutions containing high concentrations of humic substances, for future studies of thiram adsorption onto solid humic substances or soils. Suspensions of humic acids and soil, in aqueous 0.01M CaCl(2) solution, were prepared and used as samples. These extracts were spiked with thiram and immediately applied to a C(18)-SPE cartridge. Thiram was eluted with chloroform and its concentration measured by spectrophotometry at 283nm. Non-spiked aqueous extracts (blanks) and a control sample of thiram in 0.01M CaCl(2) aqueous solution were also prepared and submitted to the same SPE procedure. The results show that humic substances are extensively retained by the C(18) cartridge but are not eluted with CHCl(3). Recoveries of 100-104% were obtained for thiram in the presence of humic substances. The SPE procedure described in this work is an efficient clean-up step to remove the interference of humic substances absorbance and to be coupled to any spectrophotometric or HPLC-UV method, usually used for thiram analysis in food extracts.