Development of measurement and analysis method for long-term monitoring of 41-K

This study aimed to develop a double labeling method with 41K and 15N for animal feed and excreta. Guinea pig was used as the subjects for the preliminary experiment. Animal feces and urine were separately collected once a day and the feces were dried at 70degC and urine was lyophilized. Those samples were submitted to analysis after mixing. Then, 41KCl solution and 15NH4SO4 solution were absorbed to the conventional guinea pig feed and 1.0 g of the feed was given once a day. The amount of 41K in feces was determined using flame photometric detector and 15N was determined by ANCA-SL Mass spectrometer. The isotope abundances of 41K and 15N in the feed were 6.11% and 0.829%, respectively and the excess % was -0.062 % and 0.46 % for 41K and 15N, respectively. The present results showed that 15-N labeling for feces was fairly succeeded, but 41K labeling was insufficient. Therefore, it is thought necessary to use K tracer of a larger excess % (-0.3% or more) and raise the accuracy of analysis for total K and 41K. (M.N.)