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Abstract

A method based on indirect photometric detection (IPD) in CE employing a blue LED
(473 nm) as a light source and the highly absorbing (478 nm) anionic dye, Orange G, as the
probe ion was developed for the sensitive analysis of inorganic and organic anions. The use
of nonaqueous solvents was examined as a simple way to reduce the adsorption of the dye
onto the capillary wall and to thereby improve the baseline stability. The benefits of this
approach were confirmed by experiments using BGEs in methanol (MeOH) and DMSO in
which superior baselines were obtained relative to those achieved using aqueous electrolyte
systems. A range of commercial LEDs was tested to improve the detection performance,
with a difference of 25% in sensitivity being observed between the best and worst performing
LED. The final system (4 mM Orange G, 0.05% w/v hydroxypropylcellulose
(HPC), 20 mM triethanolamine (TEA) in pure MeOH) exhibited stable baselines and very
low LODs (0.10–0.18 mM) for a test mixture comprising nine inorganic and organic anions.
These values represent a two- to six-fold improvement over previous studies and the proposed
method provides the most sensitive IPD method for the determination of anions
using CE published to date. RSDs for ten replicates were in the ranges of 0.42–0.62% for
migration time, 1.41–3.46% for peak area and 3.20–5.78% for peak height.

Item Type:	Article
Authors/Creators:	Blanco-Heras, GA and Breadmore, MC and Johns, CA and Hutchinson, JP and Hilder, EF and Lopez-Mahia, P and Haddad, PR
Keywords:	Anions • Dye • Indirect photometric detection • Light-emitting diode • Nonaqueous capillary electrophoresis
Journal or Publication Title:	Electrophoresis
ISSN:	0173-0835
DOI / ID Number:	10.1002/elps.200800116
Additional Information:	The definitive published version is available online at: http://interscience.wiley.com
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