Sensitivity Enhancement by Sweeping <i>via</i> Solid Phase Extraction Using Titania Nanoparticles in Capillary Electrophoretic Analysis of Phosphopeptides

Abstract

This paper reports an on-line sample preconcentration by a sweeping technique based on the surface complexation between TiO 2 (titania) nanoparticles and phosphate groups in the capillary electrophoresis (CE) analysis of phosphopeptides. It is well-known that titania particles can trap phosphopeptides under an acidic condition, while under an alkaline condition they are eluted from the titania surfaces. In the sweeping via solid phase extraction using the titania nanoparticles, a phosphopeptide solution is injected as a long plug into a capillary filled with an acidic background solution. Due to the complexation onto the titania surfaces, the analytes in a long sample zone are swept by the titania particles to a narrow zone. This preconcentration technique was applied to the analysis of monophosphopeptide from β-casein. When an 1% titania dispersion and 100 ppm phosphopeptide solution was successively introduced into the capillary at the injection time of 30 s and 60 s, respectively, a sharp peak of the phosphopeptide was obtained by UV detection without any optical interferences of the titania. Comparing with a conventional CE analysis, a 22-fold sensitivity increase was achieved by the preconcentration effect.

Recent progress of sample stacking in capillary electrophoresis (2016–2018)

“…Kitagawa et al. reported an EKC‐sweeping technique based on surface complexation between TiO 2 nanoparticles and phosphate groups and applied it to the analysis of phosphopeptides. Sweeping proceeded by injecting a long plug of acidic sample in 0.05% TFA at pH 2.3 after a plug of an alkaline 0.25% dispersion of TiO 2 in 0.01% NH 3 at pH 10.1, followed by CZE separation with 0.1% NH 3 at pH 11.1 as the BGE.…”

Highly Sensitive Analysis in Capillary Electrophoresis Using Large-volume Sample Stacking with an Electroosmotic Flow Pump Combined with Field-amplified Sample Injection

“…To overcome this drawback, various on-line sample preconcentration techniques have been developed. [1][2][3][4][5][6][7][8] In our research group, on-line sample preconcentration by large-volume sample stacking with an electroosmotic flow pump (LVSEP) was applied to CE and microchip electrophoresis (MCE). [9][10][11][12][13][14][15][16] LVSEP experiments can be performed with simple procedures, i.e., the whole capillary sample-injection and the application of a voltage without polarity switching.…”

LVSEP Analysis of Cationic Analytes in Non-Aqueous Capillary Electrophoresis

“…To improve the sensitivity, several on-line sample preconcentration techniques have been applied to NACE. Among various on-line sample preconcentration techniques in CE [5][6][7][8][9][10][11][12], large-volume sample stacking with an electroosmotic flow pump (LVSEP) has unique characteristics including efficient enrichments by a whole capillary sample-injection, simple experimental procedures based on a voltage application without polarity switching, and high resolutions according to the movement of the stacked analytes zone from the capillary inlet to the outlet [12][13][14][15][16][17][18][19][20]. In this study, LVSEP was combined with NACE to achieve highly sensitive analyses of cationic compounds with unique selectivities in non-aqueous media.…”