Next generation stationary phases for high performance chelation ion chromatography

This study was dedicated to the development and characterisation of novel stationary phases for the detection and separation of metal cations in high performance chelation ion chromatography (HPCIC). Standard ion exchange chromatography is often unsuitable for the analysis of metals in complex samples as the ion exchange sites can become swamped by the presence of alkali metal salts. Commonly used spectroscopic techniques can be costly and time consuming due to the requirement of sample dilution and/or preconcentration, which can affect sensitivity and limits of detection. Furthermore, many of these methods also require a large sample volume and are unable to tolerate even minute quantities of salts in complex matrices. HPCIC has proven to be a promising alternative to spectroscopic detection techniques and standard ion exchange chromatography, mainly due to the ease in which the selectivity for metal cations can be manipulated. Therefore, in the work presented herein, a number of stationary phases of different morphologies were fabricated and/or characterised for the determination of metal cations in HPCIC. Firstly, polymeric and silica based columns functionalised with IDA were compared for their chromatographic behaviour for selected metal cations. A commercially available silica monolith column was covalently modified with Nhydroxyethyliminodiacetic (HEIDA) groups and successfully characterised for alkaline earth and selected transition and heavy metal cations, achieving peak efficiencies of 54,000, 60,000 and 64,000 N/m, for Zn2+, Mn2+ and Cd2+. The monolithic HEIDA-silica column and a N-(2-hydroxyethyl)-N- (2[phosphonomethyl)amino]acetic (HEPMA) modified silica monolith with alternative selectivity were applied to the development of a new HPCIC method for the quantitative determination of Mn2+, Cd2+ and Zn2+ in mussel digest samples. Finally, a chelating HEIDA modified core-shell stationary phase was fabricated and characterised for a number of metal cations including rare earth elements. The stationary phase was fully characterised and showed peak efficiencies (>200,000 N/m) far exceeding those previously observed on any IDA silica stationary phase. The work carried out proved HPCIC to be a convenient and efficient analytical method for the determination and separation of metal cations in complex samples, and a possible alternative to the aforementioned spectroscopic techniques