title: 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.
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 x 10(-9 )m2V(-1)s(-1)) and an ion-exchange capacity of 57 microequiv./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 microM detection limits were obtained.
authors.affiliation: Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Tasmania, Australia.
authors.forename: Shusheng
authors.initials: S
authors.lastname: Zhang
authors.forename: Miroslav
authors.initials: M
authors.lastname: Macka
authors.forename: Paul R
authors.initials: PR
authors.lastname: Haddad
mesh_terms: D050339:Benzylammonium Compounds / Q000302:isolation & purification; D002412:Cations / Q000302:isolation & purification; D002852:Chromatography, Ion Exchange / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D007475:Ion Exchange Resins; D007840:Latex
chemical_list: D050339:Benzylammonium Compounds; D002412:Cations; D007475:Ion Exchange Resins; D007840:Latex