Figure 12-6. Comparison of analysis with and without additives in a ultra-high performance supercritical fluid chromatography method for the separation of vardenafil (API, peak 1) and its six impurities on a charged surface hybrid pentaflurophenyl (CSH PFP) column and for the separation of agomelatine (API, peak 4) and its six impurities on a bridged ethyl hybrid (BEH) column. Gradient elution of 5%-40% was performed with methanol as an organic modifier (A), with methanol + 10 mM ammonium formate (B), and with methanol + 10 mM ammonium acetate (C) in 3 min, flow-rate 1.5 mL/min, temperature 40oC, backpressure regulator 2000 psi, UV detection at 225 nm. NE, not eluted.
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