On-column ion-exchange preconcentration of inorganic anions in open tubular capillary electrochromatography with elution using transient-isotachophoretic gradients. 3. Implementation and method development.
A solid-phase extraction method based on an ion-exchange retention mechanism has been used for in-line preconcentration of inorganic anions prior to their separation by capillary electrophoresis (CE). A single capillary containing a preconcentration and a separation zone has been used in a commercial CE instrument without instrumental modification. Analyte anions were retained on a preconcentration zone comprising an adsorbed layer of cationic latex particles, while separation was achieved in a separation zone comprising fused silica modified by adsorption of a cationic polymer. Elution of the adsorbed analytes was achieved using an eluotropic gradient formed by a transient isotachophoretic boundary between a fluoride electrolyte and a naphthalenedisulfonate electrolyte. Optimization of the electrolyte concentrations, sample injection times, and back-flushing times allowed the successful separation of sub-ppb levels of inorganic anions using a 100-min injection at 2 bar pressure, introducing over 40 capillary volumes of sample. A method based on a 10-min injection allowed a 100-fold increase in sensitivity over conventional hydrodynamic injection for Br-, I-, NO3-, CrO4(2-), and MoO4(2-) with a total analysis time of 25 min. Detection limits were dependent on the injection time but were in the range 2.2-11.6 ppb for a 10-min injection time. This approach was used to determine NO3- in Antarctic ice cores where the analysis could be performed using a sample volume 100 times less than that used for ion chromatography.
Breadmore
Michael C
MC
Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Hobart.
Palmer
Anne S
AS
Curran
Mark
M
Macka
Miroslav
M
Avdalovic
Nebojsa
N
Haddad
Paul R
PR
D000838:Anions / Q000032:analysis*; D000864:Antarctic Regions; D019075:Electrophoresis, Capillary / Q000379:methods*; D007053:Ice / Q000032:analysis*; D008722:Methods; D008832:Microchemistry; D009566:Nitrates / Q000032:analysis; D012680:Sensitivity and Specificity
D000838:Anions; D007053:Ice; D009566:Nitrates