Stock solutions of all analytes (1.0×10−2 mol/L each)
were prepared in anhydrous ethanol (A.R. grade), and were
diluted to the desired concentration with the running buffer
(20 mmol/L H3BO3–Na2B4O7 buffer and sodium dodecyl
sulphate (SDS) ranging from 5 to 30 mmol/L with pH value
7.4).