Theobromine stock solution remained stable for more than two months when stored at 4 °C. Urine samples were diluted 1:5 (vol/vol) in water, filtered through a 0.45-μm nylon filter, and directly injected into the HPLC system.
Theobromine stock solutionremained stable for more than two months when stored at 4 °C.Urine samples were diluted 1:5 (vol/vol) in water, filtered through a0.45-μm nylon filter, and directly injected into the HPLC system.