Ionchromatography on chelating stationary phases

Ion-chromatography on chelating stationary phases is widely used in analytical chemistry. In this thesis iminodiaceticacid was immobilized onto epoxy-activated silica. This results in the formation of N-(hydroxyethyl)iminodiacetic acid as a chelating functional group. Different silica-materials with varying average pore diameters were compared. To show the wide applicability of these stationary phases different separation systems for the analysis of the alkaline, alkaline earth and several transition metals were developed. Because of the low complex formation constants of the alkaline metals with HIDA the addition of 18-crown-6 to the mobile phase was necessary in order to improve the selectivity of the system. Ammonium, sodium and potassium could be successfully separated and quantitated in the lower ppb-range in drinking-, river and rainwater. Upon optimization of the chromatographic elution conditions the separation of six transitions metals (Hg, Pb, Zn, Cd, Co, Fe) on HIDA-silica was feasible within six minutes. The application of gradient elution allowed the separation of seven transition and four alkaline earth metals within twelve minutes. A theory was developed to calculate the effective complex formation constants from retention data as a function pyridine-2,6-dicarboxylic acid (DPA) concentration. A new selective detection method for iron(II) basing on complex formation with DPA is described. This method allows the highly selective determination of trace amounts of iron(II) in presence of iron(III). A new trace-enrichment method for copper, lead and mercury on HIDA-silica at low pH-values (pH 1,75) was developed. High recoveries for all three analytes in the low ppb-range were obtained. The enrichment of lead and copper from a drinking water sample is shown. (author)