Mass spectrometric determination of cytokinins in the top of tobacco plants using deuterium-labeled standards.

Penta-deuterated zeatin, ribosylzeatin, and glucosylzeatin were prepared by the condensation of 6-chloropurine, 9-beta-D-ribosyl- and 9-beta-D-glucosyl-6-chloropurine, and 4-hydroxy-3-methyl-2-butenylamine-d5 derived from acetone-d6. The deuterium contents of these compounds were approximately 96%. Zeatin, ribosylzeatin, N6-isopentenyladenosine and 2-methylthio-ribosylzeatin in the top of tobacco plants were quantitated by mass spectrometry using deuterium-labeled standards.