On‐line coupled capillary isotachophoresis‐capillary zone electrophoresis in hydrodynamically closed separation system hyphenated with laser induced fluorescence detection

Abstract

An analytical method, based on a column coupling capillary ITP and CZE in a hydrodynamically closed separation mode hyphenated with the detection in the modular arrangement, was developed in this work. Analytical possibilities of this approach are demonstrated on the direct and ultrasensitive quantitative determination of quinine (QUI) in diluted real multicomponent ionic matrices (beverages, urine). The detection cell interface, with the rectangular arrangement of the optical channels inside, connected the separation capillary with the LIF detector via optical fibers in the on-column detection arrangement. ITP enabled the direct large volume (30 μL) injections of the diluted real matrices with an on-line sample pretreatment (preseparation, preconcentration) so that no external sample preparation (except for the dilution) was necessary for the separation of the analyte in the multicomponent ionic matrices. Due to the ITP sample preconcentration and intrinsic sensitivity of the LIF detection, very low concentration LOD (as low as 77 pg/mL), were reached at the same time. This was ca. two orders lower than the corresponding LOD achieved by the same 2D separation system with UV absorbance detection. Compared to the single column CE-LIF methods applied for this model analyte and matrix, this method was found to be superior in terms of concentration LOD, with acceptable selectivity and benefits of the on-line sample preparation. A food control and bioanalytical application clearly illustrates great practical possibilities and routine use of the proposed modular ITP-CZE-LIF technique.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2012–2014)

“…The ITP step allows larger sample volume to be injected (30 μL) giving an LOD of 8.6 ng/mL. The authors then studied cITP‐CZE‐LIF for quantitative determination of quinine . When even this provides insufficient performance, it is possible to add a third dimension: ITP‐ITP‐CZE .…”

Recent advances in microscale separation

“…Mikuš et al. developed a direct and ultrasensitive quantitative determination of quinine in diluted real multicomponent ionic matrices based on CITP‐LIF technique. Due to the CITP sample preconcentration and intrinsic sensitivity of the LIF detection, very low concentration LOD (as low as 77 pg/mL), was reached at the same time.…”

Recent progress in analytical capillary isotachophoresis

“…Mikuš et al. developed a detection cell interface for ITP‐CZE with LIF detection having a rectangular arrangement of the optical channels. Its analytical possibilities were demonstrated on the determination of quinine in diluted real multicomponent ionic matrices like beverages or urine (LE: 10 mM sodium acetate, 20 mM HAc, 1 mM NaH 2 PO 4 , 0.1% w/v methyl‐2‐hydroxyethylcellulose (MHEC), pH 4.5; TE: 10 mM β‐alanine, 10 mM HAc, pH 4.3; BGE: 25 mM β‐alanine, 25 mM HAc, 0.1% w/v MHEC, pH 4.3).…”