Analysis Of Azithromycin On The Alliance™ iS HPLC System: System Performance Under Challenging Method Conditions

By Anthony Dovell, Paula Hong

Many legacy monographs rely on buffered mobile phases to ensure consistent HPLC performance. In traditional gradient reversed-phase applications, the mobile phase transitions from a buffered aqueous solution to an organic solvent. This shift can lead to salt precipitation, especially when the water/organic ratio is unfavorable. Additionally, system-to-system variability can arise due to design differences.

To illustrate these challenges, we examined the USP monograph for Azithromycin Organic Impurities. This monograph employs a weak, 12 mM aqueous buffer and a strong organic mobile phase (acetonitrile/methanol). The gradient involves a strong elution step with a 25/75 aqueous/organic ratio.

We tested this monograph on multiple HPLC systems using replicate standard injections to assess system suitability and performance variations.