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Selective extraction and elution of weak bases by in-line solid-phase extraction capillary electrophoresis using a pH step gradient and a weak cation-exchange monolith

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Thabano, JE, Breadmore, MC, Johns, CA, Hutchinson, JP and Haddad, PR 2008 , 'Selective extraction and elution of weak bases by in-line solid-phase extraction capillary electrophoresis using a pH step gradient and a weak cation-exchange monolith' , Analyst, vol. 133, no. 10 , pp. 1380-1387 , doi: 10.1039/b804805c.

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Abstract

A polymer monolith bearing weak cation-exchange functionality was prepared for the purpose of
demonstrating pH-selective extraction and elution in in-line solid-phase extraction–capillary
electrophoresis (SPE–CE) utilising a model set of cationic analytes, namely imidazole, lutidine and
3-phenylpropanamine. Optimization of the electrolyte conditions for efficient elution of the
adsorbed analytes using a moving pH boundary required that the capillary and monolith be filled
with 44 mM sodium acetate at high pH (pH 6) and a low pH electrolyte of 3 mM sodium acetate
pH 3 was placed in the electrolyte vials. This combination allowed the adsorbed analytes to be
simultaneously eluted and focused into narrow bands, with peak widths of the eluted analytes
having a baseline width of 1.2 s immediately after the monolith. Using these optimum elution
conditions, the versatility of the SPE–CE approach was demonstrated by removing unwanted
adsorbed components after extraction with a wash at a different pH and also by selecting a pH at
which only some of the model weak bases were ionised. The analytical performance of the
approach was evaluated and the relative standard deviation for peak heights, peak area and
migration times were in the ranges of 1.4–5.3, 1.2–3.3 and 0.4–1.2% respectively. Analytes
exhibited linear calibrations with r2 values ranging from 0.996 to 0.999 over two orders of
magnitude. Analyte pre-concentration provided excellent sensitivity, and limits of detection for the
analyte used in this study were in the range 8.0–30 ng ml-1, which was an enhancement of 63 when
compared to normal hydrodynamic injection occupying 1.3% of the capillary of these bases in
water.

Item Type: Article
Authors/Creators:Thabano, JE and Breadmore, MC and Johns, CA and Hutchinson, JP and Haddad, PR
Journal or Publication Title: Analyst
ISSN: 0003-2654
DOI / ID Number: 10.1039/b804805c
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