Monday, November 5, 2007 - 4:00 PM
121-10
Probing Roxarsone Degradation in Animal Waste with the Aid of Electrospray Mass Spectrometry.
Recent data suggests that roxarsone degradation in land-applied poultry litter (PL) could contaminate crops and water bodies with toxic inorganic As, posing serious threat to human health. Roxarsone degradation to inorganic As depends upon microbial activity, redox potential, pH and the solution ionic composition. Partial degradation of roxarsone to organoarsenical metabolites has been inferred due to incomplete recoveries of total soluble As concentrations with HPLC-ICPMS analyses of known arsenical (inorganic + organic) compounds. The PL water extract contains large concentrations of NO3-, NO2-, NH3(l), PO43-, and metals, such as, Cu and Zn typically added to poultry feeds. Isolation of organoarsenicals from the highly complex PL water extract is mandatory prior to detecting roxarsone and its metabolites. A liquid/liquid extraction coupled with the use of an anionic-exchange resin procedure was optimized to ensure isolation of the organoarsenicals. Electrospray mass spectrometry (ES-MS) coupled with its collision-induced dissociation (CID) capability is a powerful tool in elucidating the structures of low in molecular mass compounds. Negative ion mode of the ES-MS allowed for qualitative identification of organoarsenical metabolites produced upon possible reaction of roxarsone with inorganic nitrogenous compounds, as well as transition metals, such as Cu. Results were examined in light of roxarsone degradation products and their effects on the overall As fate and mobility in the environment.
Audio File