Good day, im having some issues trying to detect ciprofloxacin at 25 mg/l in RP HPLC analysis, im using several mobile phases but there are 2 peaks when in the literature only appears 1, i tried running it in several solutions of the same mobile phase 60:40, 45:55 and 16:84 Acetonitrile: acid water (4% acetic acid pH 3), and 87:13 phosphoric acid (0.025 M pH 2.21): Acetonitrile, there is always a secondary peak and im using laboratory grade CPX, can someone help me