ANALYTE STABILITY STUDY OF N-METHYLCARBAMATE PESTICIDES IN BEEF AND POULTRY LIVER-TISSUES BY LIQUID-CHROMATOGRAPHY

To optimize conditions for sample collection, preparation, storage, an d analysis and to assure the validity of our previously published liqu id chromatographic (LC) method for carbamate analysis in tissue, stabi lities of 16 N-methylcarbamates in beef, duck, and chicken liver tissu es were studied by using 2 sampling protocols. Tissue samples were for tified at room temperature to a concentration 5 to 10 times greater th an either the Environmental Protection Agency tolerance level for each compound (if established) or the concentration used in the previously published method. Thereafter, samples were continuously frozen at -4- degrees-C for varying time intervals. In the first study, samples were analyzed one day (initial) and 0.5, 1, 1.5, 2, 3, 4, 5, and 6 months after fortification. In the second study, samples were analyzed one da y (initial) and 0.5, 1, 2, 3, and 6 months after fortification. For ea ch residue and species, a minimum of 4 samples were analyzed by LC at each point in time, and the mean represented analyte concentration at the end of each time interval. Rates of residue depletion varied among analytes and among species. Depletion rates were greater in duck live rs than in beef livers. Methomyl and oxamyl were depleted completely w ithin 2 weeks. Between 2 and 6 months after sample fortification, resi due depletions to levels below detection limits were observed for aldi carb, aldicarb sulfoxide, aldicarb sulfone, dioxacarb, promecarb, prop oxur, and bendiocarb. The initial loss of certain carbamates during sa mple preparation in tissues exposed to room temperature for up to 8h w as greater than the subsequent rate of loss. Results indicate that cry ogenic conditions are required for sample preparation and storage. Res ults also provide information on how long a violative evidentiary samp le can be stored for potential litigation.