Isolation and characterization of impurities present in 8-chlorotheophylline

A simple isocratic reversed phase high performance liquid chromatography was used to separate three impurities present in the sample of 8-chlorotheophylline. LC-MS was used for the characterization of impurities. Based on mass spectral data, the structures of these impurities were characterized as 3,7-dihydro-1,3-dimethyl-1H-purine-2,6-dione (impurity I), 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione (impurity II) and isomer of 8-chloro-1,3-dimethyl-2,6(3H,1H)-purinedione (impurity III).