Preparation and characterisation of dual-layer latex-coated columns for open-tubular capillary electrochromatographic preconcentration of cations combined in-line with their separation by capillary electrophoresis
✍ Scribed by Shusheng Zhang; Miroslav Macka; Paul R. Haddad
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 260 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0173-0835
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✦ Synopsis
Abstract
A dual‐layer ion‐exchange latex‐coated column was prepared and characterised for on‐capillary preconcentration of cations using an open‐tubular ion‐exchange CEC format. After preconcentration, the analyte cations were eluted with a transient isotachophoretic gradient and separated by CE. The latex double layer was established by first coating the negatively charged wall of the capillary with a layer of cationic quaternary ammonium anion‐exchange Dionex AS5A latex particles (60 nm diameter), and then coating a layer of anionic sulphonated cation‐exchange Dionex CS3 latex particles (300 nm diameter) onto the underlying AS5A layer. The adhesion of layers is based on electrostatic attractions. Several dual‐layer capillaries were characterised for their EOF and ion‐exchange capacity and this showed that coatings could be prepared reproducibly by a simple flushing procedure. The dual‐layer columns exhibited a moderate, pH‐independent EOF (ca. 26×10^−9^m^2^V^−1^s^−1^) and an ion‐exchange capacity of 57 µequiv./g (or 2.69 nequiv./column). Using an 8 cm length of coated capillary combined with a 72 cm length of untreated capillary, a method for on‐line preconcentration and separation of monovalent organic bases, alkali metal ions and alkaline earth metal ions by CE was developed. Recoveries for the preconcentration step were 48% for 4‐methylbenzylammonium, 43% for benzylammonium, 30–32% for alkali metal ions and 71–75% for alkaline earth cations. In all cases, recoveries were reproducible with RSDs being less than 6.2%. The influences of the ion‐exchange selectivity coefficient of the analyte and the sample‐loading rate on analyte recovery were also examined. The proposed method was utilised for the determination of alkaline earth cations and low µM detection limits were obtained.