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

Abstract

To achieve highly sensitive analysis without labor-intensive experimental procedures in capillary electrophoresis (CE), large-volume sample stacking with an electroosmotic flow pump (LVSEP)-field-amplified sample injection (FASI) was combined with a dynamic coating technique. In this study, poly(vinyl pyrrolidone) (PVP) was employed for the dynamic coating additive. Since a standard fluorescent dye, fluorescein, was well concentrated in a conventional LVSEP, the PVP dynamically-coated capillaries can be also applied to the LVSEP-FASI analysis. In our home-made CE apparatus, however, current breakdown was often caused, especially at a longer electrokinetic injection time due to bubble formation. To avoid the interference of bubble formation, the distance between the tips of the electrode and the capillary in the vertical direction was changed from 0 to 2.5 cm under the magnetic stirring condition. This allowed for a long electrokinetic injection time of up to 20 min, resulting in a sensitive enhancement factor (SEF) of 34900 for fluorescein. The developed method was applied to the chiral analysis of amino acids in CE. As a result, leucine (Leu) was successfully separated in LVSEP-FASI with SEFs of 6420 and 4500 for the D-and L-Leu peaks, respectively.

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.…”

“…In the PVA coating, however, there are several problems, e.g., need of labor-intensive preparations, capillary clogging, and low success yield of the coating. To simplify the experimental procedures, a dynamic coating technique was applied to LVSEP [13]. In the dynamic coating, only the use of a running solution containing polymers alters the zeta potential of the inner surface of the capillary in the conditioning step and during the CE measurements.…”

A Mobile and Self‐Powered Micro‐Flow Pump Based on Triboelectricity Driven Electroosmosis

“…[12][13][14] Among various driving mechanisms, electroosmotic pumps (EOP) are widely employed in microfluidic systems due to their advantages of easy fabrication, constant fluid velocity and high integratability compared with mechanical-pressure and thermal-gradient driven approaches. [15][16][17][18] Electroosmotic pumps are usually controlled by changing the magnitude and direction of electric field in the electric double layer region that induced electroosmotic flow (EOF). [19][20][21] In this case, an external high-voltage (HV) DC source is mandatorily required to manipulate the EOF rate or volume, which would always form bubbles and generate Joule heat near the electrode, thus affect the efficiency of microflow.…”

LVSEP Analysis of Cationic Analytes in Cationic Polymer-Coating Microchannel Prepared by Vacuum-Drying Method

“…To overcome the sensitivity problem, various on-line sample preconcentration techniques, including stacking [4][5][6], sweeping [7,8], selective sweeping [9][10][11], dynamic pH junction [12], transient isotachophoresis [13][14][15] and their modified techniques [16][17][18][19][20], have been developed in capillary electrophoresis (CE) and MCE. Among these techniques, large-volume sample stacking with an electroosmotic flow (EOF) pump (LVSEP) has several unique characteristics, e.g., efficient enrichments by a whole column 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 column inlet to the outlet [21][22][23][24][25][26][27][28][29][30]. However, the LVSEP technique has been mainly applied to the analyses of anionic compounds, i.e., the applications to cations have been limited since a reversal EOF is required.…”