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Mixed-mode capillary electrochromatographic separation of anionic analytes
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In this work, mixed-mode capillary electrochromatography is introduced as a method for selectivity manipulation in the separation of charged analytes and is investigated for a number of analytes. This concept involves utilising a component of the eluent to permit the chromatographic and capillary electrophoresis (CE) separation mechanisms to contribute in varying proportions to the separation. This approach was first investigated using a combination of CE with reversed-phase liquid chromatography (RP-LC) for hydrophobic, charged analytes (aliphatic sulfonates), and using the concentration of organic modifier in the eluent to control the contributions of CE and RP-LC. However, the use of reversed-phase columns was found to be problematic for mobile phases with less then 50% organic modifier due to the hydrophobicity of the stationary phase causing the column bed to overheat and dry, and low electroosmotic flow (EOF) values (µ ? 17.8 × 10–9 m2 V–1 s–1) caused additional restrictions. In a second case, ion-exchange stationary phases were used, with the type and concentration of a competing anion in the eluent being used to control the contributions of ion chromatography (IC) and CE to the separation. Nine common inorganic anions were separated using a silica based anion-exchange column and phosphate (pH 7.20) or sulfate (pH 8.2) as eluent with direct UV detection at 214 nm and 17 inorganic and small organic anions were separated using a nitrate eluent (pH 6.80) with indirect UV detection at 214 nm. The separation selectivity was shown to be a combination of IC and CE.
|Keywords:||mixed-mode capillary electrochromatography,charged analytes, chromatographic and capillary electrophoresis (CE) separation mechanisms, reversed-phase liquid chromatography, hydrophobic, charged analytes, ion-exchange stationary phases,|
|Journal or Publication Title:||Analytical Communications|
|Page Range:||pp. 299-303|
|Identification Number - DOI:||10.1039/a904506f|
© Royal Society of Chemistry 1999.
|Date Deposited:||20 Nov 2008 00:03|
|Last Modified:||18 Nov 2014 03:53|
|Item Statistics:||View statistics for this item|
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