The present invention further provides an analytical method for determining the purity of 5-Azacytidine in a sample, said method comprising :a) providing a sample of 5-Azacytidine,b) dissolving a first part of the sample in dimethyl sulfoxide ("DMSO"), and a second part of the sample in dimethylpropyleneurea ("DMPU"), providing a first and a second sample solution,c) injecting each sample solution onto an HPLC column under the same conditions, providing a first and a second chromatogram, andd) determining the purity of 5-Azacytidine and the amount of each impurity based on both chromatograms.
