Metal ion interaction with anion chromatography using Waters IC PAK column

Simultaneous detection of polyvalent cations and nitrate anion at pH 8.0, 8.5, and 9.0 was performed using a gluconate-borate eluent with a single column anion chromatography system. Both conductivity and ultraviolet detection were employed in a modified chromatographic system, with the cation complexing reagent, 4-(2 pyridylazo) resorcinol (PAR), being used for cation analysis. The investigation was performed on a Waters IC PAK column with 50ppm nitrate solutions of Zn$\sp{2+}$, Cu$\sp{2+}$, Pb$\sp{2+}$, Cd$\sp{2+}$, Ca$\sp{2+}$, Mg$\sp{2+}$, Ni$\sp{2+}$, and Mn$\sp{2+}$, to elucidate their retention times. The nature of interaction of these cations with the eluent and effects of changing the eluent pH were studied. The retention times of the ions were determined, the chromatograms contained one or two extraneous peaks called system peaks, formed due to the complexation of cations with the eluent. Both the cation and the nitrate peaks showed a decrease in retention with an increase in pH.