Effect of stationary phase or organic modifier on resolution of SCMSV peptide pairs substituted with alanine (Ala, A), valine (Val, V) or isoleucine (Ile, I) at position X (Table 1). Column denotions: C8, cross-hatched; C18, white; Hydro, upward slanted line; Fusion, black; Polar, grey; Phenyl-Hexyl, downward slanted line. Sequences of AmN, AcN, AmC and AcC peptides shown in Table 1. HPLC conditions shown in Section 2.3. Data shown in Table 3.