Determination of the diastereoisomeric purity of D,L- and meso-HM-PAO by 13C-NMR spectroscopy.

D,L-hexamethylpropyleneamine oxime (HM-PAO) is well known to be the effective isomer when HM-PAO is used as a radiopharmaceutical. Its diastereoisomeric purity is of great importance because meso-impurity decreases the concentration of the 99mTc-complex in the brain. The described investigation shows that 13C-NMR spectroscopy is a suitable analytical method for the determination of the diastereoisomeric purity of HM-PAO. It also can be used for assessment of the relative ratio of both isomers in diastereoisomeric mixtures. It is important to note that the patterns of behaviour of both isomers in 13C-NMR spectra are the same in all solvents tested. The method is simple, fast and explicit.