The eluent solution, 2 mol l−1 HCl, was prepared by diluting 167 ml of concentrated acid supplied by Merck (Darmstadt,
Germany), in a volume of water enough to made up 1000 ml.
Borate buffer solution with 0.5 mol l−1 concentration and pH 9.0 was prepared by dissolving 15.45 g of boric acid in
around 400 ml of water.
Afterwards, KOH was added until solution achieved desired pH.
Then, the volume was filled up to 500 ml, and the pH was measured again.