An isotopically labeled reagent comprising: a compound having a formula L-( a C b H 2) n a C b H 3 where a in each occurrence is independently a carbon atomic mass number of between 11 and 14 inclusive, and wherein said compound is isotopically enriched with at least one carbon where a is 11, 13 or 14, where b in each occurrence is independently a hydrogen atomic mass number of between 1 and 3, where L is a leaving group R 1 SO 2 -O-, where n is 0, where R 1 is aryl, C 1 -C 20 alkyl, C 2 -C 20 alkenyl, and C 2 -C 20 alkynyl, which aryl, C 1 -C 20 alkyl, C 2 -C 20 alkenyl and C 2 -C 20 alkynyl may optionally be modified by replacing a hydrogen bonded to a carbon atom with a substituent independently selected from alkyl, amino, cycloalkyl, halo, nitro, cyano, -OR 2, acyl and -COOR 3, where said aryl is a monovalent, monocyclic, or bicyclic aromatic hydrocarbon radical of 6 to 10 ring atoms, said alkyl designates C 1 -C 6 alkyl, said amino designates NH 2, NHR 4 or NR 4 R 5, where R 4 and R 5 are independently selected from C 1 -C 6 alkyl, an aryl defined as a monocyclic or bicyclic aromatic hydrocarbon radical of 6 to 10 ring atoms, C 1 -C 6 alkoxy or C 6 phenoxy, said cycloalkyl designates cyclopentyl or cyclohexyl, said halo designates fluoro, chloro, bromo or iodo, said R 2 designates hydrogen, C 1 -C 6 alkyl, C 5 or C 6 cycloalkyl, a heterocycloalkyl selected from furanyl, tetrahydrofuranyl, epoxy, tetrahydropyranyl, dioxynyl, thiacyclopentyl, azeridyl pyrolidyl, piperadyl, morpholyl and C 1 -C 6 alkyl substituted forms thereof, and a phenyl, which has been modified by replacing a hydrogen bonded to a carbon atom with each substituent independently selected from alkyl, amino, cycloalkyl, halo, nitro, cyano, -OR 2, acyl and -COOR 3, and said R 3 designates hydrogen or C 1 -C 6 alkyl. a compound having a formula L-( a C b H 2) n a C b H 3 where a in each occurrence is independently a carbon atomic mass number of between 11 and 14 inclusive, and wherein said compound is isotopically enriched with at least one carbon where a is 11, 13 or 14, where b in each occurrence is independently a hydrogen atomic mass number of between 1 and 3, where L is a leaving group R 1 SO 2 -O-, where n is 0, where R 1 is aryl, C 1 -C 20 alkyl, C 2 -C 20 alkenyl, and C 2 -C 20 alkynyl, which aryl, C 1 -C 20 alkyl, C 2 -C 20 alkenyl and C 2 -C 20 alkynyl may optionally be modified by replacing a hydrogen bonded to a carbon atom with a substituent independently selected from alkyl, amino, cycloalkyl, halo, nitro, cyano, -OR 2, acyl and -COOR 3, where said aryl is a monovalent, monocyclic, or bicyclic aromatic hydrocarbon radical of 6 to 10 ring atoms, said alkyl designates C 1 -C 6 alkyl, said amino designates NH 2, NHR 4 or NR 4 R 5, where R 4 and R 5 are independently selected from C 1 -C 6 alkyl, an aryl defined as a monocyclic or bicyclic aromatic hydrocarbon radical of 6 to 10 ring atoms, C 1 -C 6 alkoxy or C 6 phenoxy, said cycloalkyl designates cyclopentyl or cyclohexyl, said halo designates fluoro, chloro, bromo or iodo, said R 2 designates hydrogen, C 1 -C 6 alkyl, C 5 or C 6 cycloalkyl, a heterocycloalkyl selected from furanyl, tetrahydrofuranyl, epoxy, tetrahydropyranyl, dioxynyl, thiacyclopentyl, azeridyl pyrolidyl, piperadyl, morpholyl and C 1 -C 6 alkyl substituted forms thereof, and a phenyl, which has been modified by replacing a hydrogen bonded to a carbon atom with each substituent independently selected from alkyl, amino, cycloalkyl, halo, nitro, cyano, -OR 2, acyl and -COOR 3, and said R 3 designates hydrogen or C 1 -C 6 alkyl.