A green, rapid, and simple HPLC-External standard method (ESM) and a quantitative analysis of multi- components with a single-marker (QAMS) method were established for the simultaneous determination of five nitroimidazole antimicrobials (Metronidazole sodium chloride injection, Tinidazole injection, Ornidazole sodium chloride injection, Morinidazole sodium chloride injection, Secnidazole tablets) in pharmaceutical preparations. The five specified drugs were chromatographed via HPLC on a ZORBAX SB-C