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Electrokinetic supercharging with a system‐induced terminator and an optimized capillary versus electrode configuration for parts‐per‐trillion detection of rare‐earth elements in CZE
Author(s) -
Xu Zhongqi,
Kawahito Kouji,
Ye Xiaoxue,
Timerbaev Andrei R.,
Hirokawa Takeshi
Publication year - 2011
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201000582
Subject(s) - electrokinetic phenomena , analyte , capillary electrophoresis , chemistry , analytical chemistry (journal) , capillary action , electrode , detection limit , chromatography , ion , materials science , organic chemistry , composite material
A further improvement of electrokinetic supercharging (EKS) methodology has been proposed, with the objective to enhance the sensitivity of the conventional CZE‐UV method down to a single‐digit part per trillion (ppt) level. The advanced EKS procedure is based on a novel phenomenon displaying the formation of a zone with an increased concentration of the hydrogen ion, capable to perform the function of a terminator, behind the sample zone upon electrokinetic injection. In combination with a visualizing co‐ion of BGE, protonated 4‐methylbenzylamine, acting as the leading ion, such system‐induced terminator a effected the transient ITP state to efficiently concentrate cationic analytes prior to CZE. Furthermore, to amass more analyte ions within the effective electric field at the injection stage, a standard sample vial was replaced with an elongated vial that allowed the sample volume to be increased from 500 to 900 μL. Alongside, this replacement made the upright distance between the electrode and the capillary tips prolonged to 40.0 mm to achieve high‐efficiency electrokinetic injection. The computer simulation was used for profiling analyte concentration, pH, and field strength in order to delineate formation of the terminator during sample injection. The proposed preconcentration strategy afforded an enrichment factor of 80 000 and thereby the LODs of rare‐earth metal ions at the ppt level, e.g. 0.04 nM (6.7 ng/L) for erbium(III).