Capillary Electrophoresis Separations on a Planar Chip with the Column-Coupling Configuration of the Separation Channels

Abstract

Some basic aspects of capillary electrophoresis (CE) separations on a poly(methyl methacrylate) chip provided with two separation channels in the column-coupling (CC) configuration and on-column conductivity detectors were studied. The CE methods employed in this study included isotachophoresis (ITP), capillary zone electrophoresis (CZE), and CZE with on-line ITP sample pretreatment (ITP-CZE). Hydrodynamic and electroosmotic flows of the solution in the separation compartment of the chip were suppressed, and electrophoresis was a dominant transport process in the separations performed by these methods. Very reproducible migration velocities of the separated constituents were typical under such transport conditions, and consequently, test analytes could be quantified by various ITP techniques with 1-2% RSD. The CC configuration of the separation channels provides means for an effective combination of an enhanced load capacity of the separation system with high detection sensitivities for the analytes in concentration-cascade ITP separations. In this way, for example, succinate, acetate, and benzoate could be separated also in instances when they were present in the loaded sample (1.2 microL) at 1 mmol/L concentrations while their limits of detection ranged from 8 to 12 micromol/L concentrations. A well-defined ITP concentration of the analyte(s) combined with an in-column sample cleanup (via an electrophoretically driven removal of the matrix constituents from the separation compartment) can be integrated into the separations performed on the CC chip. These sample pretreatment capabilities were investigated in ITP-CZE separations of model samples in which nitrite, phosphate, and fluoride (each at a 10 micromol/L concentration) accompanied matrix constituents (sulfate and chloride) at considerably higher concentrations. Here, both the concentration of the analytes and cleanup of the sample were included in the ITP separation in the first separation channel while the second separation channel served for the CZE separation of the ITP pretreated sample and the detection of the analytes.

Column Coupling Electrophoresis in Biomedical Analysis

“…3) that is extremely convenient for the conductivity detection in ITP. Although convenient to the detection of the ITP zones, conductivity detection technique has a limited applicability in the CZE separations (often measurements of small conductivity changes due to the zones on a relatively high conductivity background of the carrier electrolyte) (Ölvecká et al, 2001;Kaniansky et al, 2000).…”

“…Undoubtedly, the use of MCE can be extended advantageously to 2-D ITP separations (Ölvecká et al, 2001;Kaniansky et al, 2000). CE chip provided with the column-coupling (CC) configuration of the separation channels and corresponding scheme of the equipment for the ITP-ITP separations are the same as those ones for ITP-ZE illustrated in Fig.11.…”

Bioanalytical profile of the l-arginine/nitric oxide pathway and its evaluation by capillary electrophoresis

“…This study suggests that a similar technique could be used to determine macro-and micro-constituents at molar ratios <2×10 4 . The type of combination of CZE and ITP sample treatment can be especially useful for planar chip CE technologies such as the one introduced by Kaniansky and colleagues [318]. Our group has optimized a CZE/CD technique to measure nitrite and nitrate concentrations in hemolymph, tissues, and individual neurons samples from model mollusks [101,315], subepithelial and epithelial tissue microsamples from the midgut of mosquito larvae [249], and submicroliter tissue samples from mammalian neuronal tissues [247].…”

Large-Volume Sample Sweeping with a High Theoretical Plate Number Using a Coupled-Capillary in Capillary Electrophoresis

“…Table 1 summarizes some of these methods and some of the compounds examined. [1][2][3][4][5][6][7][8][9][10][11][12] Each method has unique advantages and disadvantages with respect to the sensitivity, precision and simplicity of use. In fact, the influence of the analyte plug width on the plate number in CE has been discussed previously.…”