Capillary electrophoresis of humic acid fractions

Capillary electrophoresis (CE) was used for the characterization of peat humic acid (HA) fractions of different molecular weight. The HA were precipitated from a 0.1M NaOH plus 0.1M Na4P2O7 peat extract acidified at pH < 2 with HCl. The HA fractions with different molecular weights were obtained using an ultrafiltration system. Using phosphate (pH 9) as running buffer, the peaks of the CE profiles were not well resolved, but using berate (pH 8.5) as the running buffer, the resolution of the peaks was improved. The highest resolution of the profiles was obtained using berate as the running buffer with the HA fractions of lower molecular weights. Using both phosphate and berate as the running buffer, the elution time for the HA fractions appeared at shorter times as the molecular size of the HA fractions decreased.