Ent A consisted of 10 mM potassium phosphate and 25 acetonitrile (pH 2.7). Solvent B included 10 mM potassium phosphate, 25 acetonitrile, and 1.0 M sodium chloride (pH 2.7). Separation was monitored by absorbance at 214 and 280 nm. Peptides were bound to the column and washed for 15 min with 100 solvent A. Peptides were then eluted at 1 ml/min where solvent B was gradually increased from 0 to 3