3. Results and discussion
3.1. Method validation
We have developed previously a robust HPLC method for
modernization of tetracycline-related USP monographs.2 In
brief, the method allowed separation of tetracycline hydrochloride
and its related compounds in less than 8 min using a
gradient mode of HPLC and a mobile phase composed of
0.1% phosphoric acid and acetonitrile. The peaks were well
resolved. Stress studies showed no interference at the retention
time of tetracycline hydrochloride and its related compounds
from the possible degradants. The method was linear, accurate