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On‐column titration and investigation of metal complex formation for aminopolycarboxylate functionalised monoliths using scanning contactless conductivity detection
Author(s) -
Gillespie Eoin,
Connolly Damian,
Nesterenko Pavel N.,
Paull Brett
Publication year - 2009
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200900232
Subject(s) - iminodiacetic acid , chemistry , conductivity , functional group , monolith , hydrogen bond , monolithic hplc column , density functional theory , analytical chemistry (journal) , amine gas treating , titration , scanning electron microscope , metal , molecule , chromatography , high performance liquid chromatography , inorganic chemistry , organic chemistry , computational chemistry , polymer , materials science , composite material , catalysis
Abstract The application of scanning capacitively coupled contactless conductivity detection (SC 4 D) for the determination of pH dependant behaviour of two aminopolycarboxylates immobilised onto the surface of a monolithic capillary column is described. The use of SC 4 D to visualise changes in conductivity of the discrete zones of functional groups within monolithic capillary columns allows for the effects of immobilisation on the physicochemical properties of zones to be compared to that of the functional group in solution. The perturbation of the p K a values of the functional groups can be attributed to the change in chemical environment experienced by the functional group through the presence of local hydrogen bonding and surface induced effects. These bonds, both between adjacent functional groups and with the monolithic polymethacrylate scaffold, result in a modification of the electron density on the functional group and therefore a change in p K a . Changes in the p K a of N ‐(2‐acetamido)iminodiacetic acid (ADA) from 2.48 to 5.2 for one of the acidic protons, with little change in the p K a of the amine group, were observed, which correlates to similar changes in aggregated systems of aminopolycarboxylates. Similar results were obtained for the iminodiacetic acid (IDA) once immobilised onto the surface of the monolith. Furthermore, the ability to measure changes in the charge of such discrete zones of functional groups allows for the visualisation of complexation events occurring directly on‐column, where such complexes result in a change in charge of the functional group. This potentially useful technique is illustrated within for the formation of aminopolycarboxylate complexes with a selection of metal ions.