Eluents tartaric acid/ethylenediamine

Fig. 3-143. Separation of alkaline-earth metals at Shimpack IC-C1. -Eluent 0.004 mol/L tartaric acid + 0.002 mol/L ethylenediamine flow rate 1.5 mL/min detection direct conductivity injection volume 20 pL solute concentrations 5 ppm magnesium, 10 ppm calcium, 20 ppm strontium, and 36 ppm barium.

Fig. 3-149. Separation of divalent cations with direct conductivity detection. - Separator column surface-sulfonated cation exchanger (Benson Co., Reno, USA) eluent 0.0015 mol/L ethylenediamine + 0.002 mol/L tartaric acid, pH 4.0 flow rate 0.85 mL/min injection volume 100 pL solute concentrations 10.3 ppm Zn2+, 9.1 ppm Co2+, 16 ppm Mn2+, 16.1 ppm Cd2+, 17.1 ppm Ca2+, 16 ppm Pb2+, and 20.3 ppm Sr2+ (taken from [148]).

In ion chromatography systems with nonsuppressed conductivity detection, mixtures of ethylenediamine and aliphatic dicarboxyhc acids such as tartaric acid or oxalic acid are typically employed as an eluent for the separation of alkaline-earth metals. Those mixtures have a relatively high intrinsic conductance, so that chromatographic signals are registered as negative peaks. 

While both conductivity detection modes are suitable for the detection of alkali and alkaline-earth metals, only nonsuppressed conductivity detection can be used for the analysis of transition metals. The formation of nondissociated metal hydroxides from the suppressor reaction precludes the use of a suppressor system for this type of analysis. Nonsuppressed conductivity detection is also impeded by the presence of complexing agents in the mobile phase these agents are required for separating transition metals. In 1983, Sevenich and Fritz [34] found an eluent mixture suited for nonsuppressed conductivity detection. It was comprised of ethylenediamine and tartaric acid. Ethylenediamine serves as an eluent ion, because it is already fully protonated (EnH ) at pH values < 5. The... 

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