Caffeine-(3-methyl-13C);1,7-Dimethyl-3-(~13~C)methyl-3,7-dihydro-1H-purine-2,6-dione;3,7-Dihydro-1,7-dimethyl-3-(methyl-13C)-1H-Purine-2,6-dione;
Caffeine-(3-methyl-13C);1,7-Dimethyl-3-(~13~C)methyl-3,7-dihydro-1H-purine-2,6-dione;3,7-Dihydro-1,7-dimethyl-3-(methyl-13C)-1H-Purine-2,6-dione;