Validation of a quantitative HPLC method for bacitracin and bacitracin zinc using EDTA as a mobile-phase modifier.

Any product marketed in the United States and labeled bacitracin must comply with the tests, procedures, and acceptance criteria in the relevant monograph published in the US Pharmacopeia (USP). The test procedure relies on accurate recovery of Bacitracin A and many other bacitracin components. The authors determined that the current USP procedure does not recover Bacitracin A at low concentration levels. They postulate that this low recovery is the result of bacitracin's known ability to chelate metal ions, e.g. in bacitracin-zinc complexes. Thus the ubiquitous metal ions in HPLC systems may be responsible for sequestering bacitracin and giving low recoveries. Addition of edetate disodium (EDTA) to the mobile phase improved the recovery. The method validation results include precision, accuracy, linearity, specificity, and robustness.