| This dissertation was written to present some applications of zwitterions as eluents in suppressed conductivity detection ion chromatography (SCD-IC) with respect to analysis of species unstable in strong alkaline, improving sensitivity of detection of anions of weak acid and changing selectivity in simultaneous separation of anions and cations. The whole dissertation consists of four parts.The first part summarizes the latest research development of ion chromatography using zwitterions as eluents. Having a myriad of advantages such as being good buffers and having very low conductivity after suppression, eluents containing zwitterions definitely have promising applications in ion exchange chromatography, ion exclusion chromatography, ion pair chromatography.In the second part, the determination of trace anions in heteropoly acid (HPA) samples by SCD-AEC and MPIC are introduced. HPA decomposes and generates phosphate in stroing alkaline solutions, which can be a problem in determination of trace foreign phosphate in HPA samples. By adding certain amounts of2-(cyclohexylamino)ethanesulfonic acid (CHES), a kind of zwitterion, and changing the composition of the eluents to adjust the pH of the eluents, chloride, phosphate and sulfate were precisely determined with the eluent of 2.5mM Na2CO3/9.0mM CHES by SCD-AEC. The method was applied to determination of industrial samples and showed good linearity, reproducibility and recovery. In MPIC, satisfactory results were also obtained with the eluent of 0.5mM TMAOH/0.5mM TBAOH/10mM MOPS/1mM Na2CO3/10% CH3CN.The third part is contributed to the improvement in sensitivity of detection of anions of weak acid, like azide. Basic amino acids (Arginine and Lysine) and acidic amino acid(Glutamic Acid) were added into the common eluents to see if they had any influence in detection of various species. It turned out that Arginine and Lysine have the ability to increase the pH after suppression while Glutamic Acid has the reverse influence.The last part is focused on the effect of zwitterions on simultaneous separation of anions and negatively charged complexes of cations by anion exchange chromatography. Firstly, the effect of CHES on separation of alkaline earth metals (Ca2+, Mg2+) and some common inorganic anions was studied. Ten anions and cations were simultaneous separated with the eluents of 8.2mM Na2CO3/0.02mM EDTA and 6.6mM Na2CO3/0.015mM EDTA/3.9mM CHES respectively. Further study was on the effect of 2-(A^-morpholino)ethanesulfonic acid (MES),3-(#-morpholino)propanesulfonic acid (MOPS), 2-(cyclohexylamino) ethanesulfonic acid (CHES) and 3-(cyclohexylamino)-l-propanesulfonic acid (CAPS) on the separation of some transition metals (Ni2+> Cd2"\ Pb2 etc.) and some common inorganic anions. It turned out that they had some influence upon selectivity and improved the resolution. By means of calculating the valence of the various ions through approximation and simplifying processing, we proposed the mechanism of selectivity. Ions with higher valence were prone to be inflenced by the change in concentration of eluents than those with lower valence, with respect to retention times. F"> BrO3, Cl', Ca2+-EDTA, NO3', Ni2+-EDTA, SO42", Zn2+-EDTA and Cu2+-EDTA were separated with the eluent of 8.5mM Na2CO3/0.02mM EDTA/5.0 mM CAPS and F, BrO3", Cl", Ca2+-EDTA, Cd2+-EDTA, Pb2+-EDTA, NO3", Ni2+-EDTA and Zn2+-EDTA were separated with the eluent of 8.5mM Na2CO3/0.02mM EDTA/lO.OmM CHES respectively. |
