Figure 4: Comparative chromatograms showing isocratic RP-HPLC separation of mixed standard, L-citrulline, and L-arginine from 2 different columns: (a) Zorbax Eclipse XDB-C18, 5 μm, and (b) Gemini C18, 3 μm; efficient separation and the best resolution were achieved by the Gemini C18 column which showed that compounds are well separated. The peaks marked represent (1) L-arginine and (2) L-citrulline.