Figure 9: Typical HPLC chromatograms obtained from 20 μl injections of Amlodipine Besylate Amlodipine impurity A, B, Atorvastatin Calcium, Atorvastatin impurity A and C under chromatographic conditions of mobile phase consisted of methanol: phosphate buffer (PH= 5.5) was pumped on Phenomenex kinetex 2.6 u C18 100A columns at a flow rate 1.2 ml/min and detected at 240 nm at constant temperature 40°C. (Ascending order) 1-Methanol 65% 2-Methanol 55% 3-Methanol 45%