Patent ID: 7358093

Claim:
A method for determining a level of impurities in an Aztreonam Lysine salt, the method comprising: forming a sample solution by dissolving the Aztreonam Lysine salt in a KH 2 PO 4 buffer solution, having a concentration of about 0.02 M and a pH adjusted to about 2 with about 25 weight percent phosphoric acid; injecting the sample solution of the Aztreonam Lysine salt into a HPLC column; eluting the injected sample with a mixture of a KH 2 PO 4 buffer solution (A) and acetonitrile (B), wherein the buffer solution (A) has a concentration of about 0.02 M and a pH adjusted to about 3 with about 25 weight percent phosphoric acid, and the injected sample is gradient eluted; and determining the amount of each impurity by measuring at a wavelength of about 230 nm with a UV detector and referring to an Aztreonam working standard at a concentration of about 2.5 g/ml.