Sodium hydroxide (Merck), potassium hydrogen phthalate (Fluka), and sodium tetraborate (Fluka) were dried at 110[degrees]C before use and 0.05 mol/kg potassium hydrogen phthalate and 0.01mol/kg sodium tetraborate solutions were prepared for calibration of the electrode systems.
The combination pH electrode was calibrated by the buffer solutions of pH 4.005 (potassium hydrogen phthalate) and 9.018 (sodium tetraborate) at 25.0 ([+ or -] 0.1)[degrees]C according to the instructions of the Molspin Manual [26].
The alkali titre and absence of carbonate were periodically checked by pH-metry, using the appropriate Gran function [40, 41] against primary standard oven-dried
potassium hydrogen phthalate. The pKa values of the MNF and PNF were determined by means of the data obtained from spectrometric titrations in 50 %, 60 % and 70 % (v/v) MeCN-water mixtures at 25.0+-0.1degC and in 0.1 mol L-1 ionic strength (KCl).
(2000) reported that at low supersaturation (0.03 to 0.05), the shallow hillocks are formed by repeated two-dimensional nucleation growth mechanism on the (010) face of
potassium hydrogen phthalate (KAP) crystals.
The mobile phase was modified with
potassium hydrogen phthalate (KHP) that strongly absorbed at the detection wavelength of 260 nm.
Cation separation was performed with 7.5 mM tartaric acid + 0.8 mM pyridine-2,6-dicarbonic acid eluent and anion separation with 2.0 mM
potassium hydrogen phthalate eluent (pH = 4.01).