Field-amplified Stacking Injection Research Articles

Highly sensitive analysis of nucleic acids using capillary gel electrophoresis with ultraviolet detection based on the combination of matrix field-amplified and head-column field-amplified stacking injection.

To develop a highly sensitive method for analyzing nucleic acids using capillary gel electrophoresis with ultraviolet detection (CGE-UV), we combined matrix field-amplified with head-column field-amplified stacking injection (C-FASI) to employ the advantages of two methods. Without diminishing the resolution, a limit of detection of 0.13 ng/ml (signal/noise=3) in a 300,000-fold diluted sample was obtained, the sensitivity is 102,308 times higher than that achieved with normal pressure injection, 3077 times that with normal electrokinetic injection, 154 times that with pressure field-amplified sample stacking injection, and 31 times that with matrix field-amplified stacking injection. After establishing the method, we tested the detection of a φX174-Hae III digest DNA product without purification and with a high ionic strength. At the lowest dilution of 5000-fold, sample at a concentration of 10 ng/ml was enriched and detected. The relative standard deviations for migration time and peak area (n=3) were 0.03-1.15 and 0.72-6.42, respectively. To further validate C-FASI was applicable for real sample, a 400 bp PCR product without purification was directly detected with a limit of detection at the concentration of 6000-fold dilution (signal/noise=3), The relative standard deviations for migration time and peak area (n=6) were 0.44 and 4.8, respectively. These results indicated that C-FASI had good qualitative and quantitative detection abilities and CGE-UV based on C-FASI is easy to perform, practical, highly-sensitive and robust for nucleic acid detection, which makes it a highly valuable tool for genetic diagnostics based on nucleic acid analysis.

Progress in stacking techniques based on field amplification of capillary electrophoresis.

Numerous strategies have been developed to mitigate the intrinsic low detection sensitivity that is a limitation of capillary electrophoresis. Among them, in-line stacking is an effective strategy to address the sensitivity challenge, and among the different stacking techniques, stacking based on field amplification is the most effective and simplest method of achieving high sensitivity without special complicated mechanisms or operations. This review introduces several stacking techniques based on field amplification. Field-amplified sample stacking, large-volume sample stacking, matrix field-amplified stacking injection (FASI), head-column FASI, matrix FASI combined with head-column FASI, FASI coupled with extraction and clean-up methods, electrokinetic supercharging, cation-anion selective exhaustive injection-sweeping-micellar electrokinetic chromatography, and newly developed techniques based on field amplification combined with other methods are included, and examples of straightforward methods for solving the sensitivity problem are provided. We also present a brief overview of the advantages, limitations, and future developments of these techniques.

On-line sample preconcentration using field-amplified stacking injection in microchip capillary electrophoresis.

Previous reports describing sample stacking on microchip capillary electrophoresis (microCE) have regarded the microchip channels as a closed system and treated the bulk flow as in traditional capillary electrophoresis. This work demonstrates that the flows arising from the intersection should be investigated as an open system. It is shown that the pressure-driven flows into or from the branch channels due to bulk velocity mismatch in the main channel should not be neglected but can be used for liquid transportation in the channels. On the basis of these concepts, a sample preconcentration scheme was developed in a commercially available single-cross glass chip for microCE. Similar to field-amplified stacking injection in traditional CE, a low conductivity sample buffer plug was introduced into the separation channel immediately before the negatively charged analyte molecules were injected. The detection sensitivity was improved by 94-, 108-, and 160-fold for fluorescein-5-isothiocyanate, fluorescein disodium, and 5-carboxyfluorescein, respectively, relative to a traditional pinched injection. The calibration curves for fluorescein and 5-carboxyfluorescein demonstrated good linearity in the concentration range (1-60 nM) investigated with acceptable reproducibility of migration time and peak height and area ratios (4-5% RSD). This preconcentration scheme will be of particular significance to the practical use of microCE in the emerging miniaturized analytical instrumentation.

Field-amplified stacking injection-capillary electrophoresis for quantitative analysis of fluoride released from dental composite

The release of fluoride is an important factor in evaluating a composite restorative material due to its anticariogenic effect. Field amplified stacking injection in capillary electrophoresis was studied to determine the concentration of fluoride released from dental restorative materials. A detection limit of 20 ng/mL was obtained with good reproducibility (relative standard deviation < 4%). The method was applied to the analysis of fluoride released from four different types of commercially available dental composites over 28 days. Results showed that field-amplified stacking injection-capillary electrophoresis was effective in monitoring the fluoride release process and product quality of different kinds of restorative materials.

Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection.

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mM phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mM phosphate - 10 mM borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Field amplified stacking injection--capillary electrophoresis for quantitative analysis of released methacrylic acid from dental composites.

Field-amplified stacking injection-capillary electrophoresis (FASI-CE) applied for the first time to the study of dental materials is demonstrated in this report. CE was used to separate methacrylic acid from the other degraded components. Due to the background electrolyte being weakly basic and methacrylic acid being negatively charged, in-capillary enrichment of the analyte was achieved by FASI. A detection limit of less than 50 ppb was obtained with good reproducibility (relative standard deviation < 3%). The method was applied to the analysis of four commercially available dental composites. Results showed that FASI-CE was effective in monitoring the fabrication process and product quality of restorative materials fabricated from methacrylate-based composites by analyzing the amount of methacrylic acid released from the residual methacrylate monomers.

Field amplified stacking injection - capillary electrophoresis for quantitative analysis of released methacrylic acid from dental composites

Field amplified stacking injection - capillary electrophoresis for quantitative analysis of released methacrylic acid from dental composites

Simultaneous analysis of lead, mercury and selenium species by capillary electrophoresis with combined ethylenediaminetetraacetic acid complexation and field-amplified stacking injection.

In this study, speciation analysis was carried out for multispecies of lead, mercury and selenium by capillary electrophoresis (CE) with combined complexation and field-amplified stacking injection (FASI). Ethylenediaminetetraacetic acid (EDTA) was added to the sample mixture to form UV-absorbing complexes with the analytes, thus enabling direct UV detection. It was also used in the running electrolyte to improve resolution. Under optimal conditions, ten analytes were baseline-separated within 20 min. The influence of operational conditions (pH, EDTA concentration, sodium dodecyl sulfate concentration) on the electrophoretic behavior of the species was studied. The analyte-related parameters were calculated based on the migration equation. Enhancement of detection, up to 1700-fold, was achieved for the charged complexes with FASI, and sub-ng/mL detection limits were obtained. The performance of this method was compared with high-performance liquid chromatography, gas chromatography and other CE procedures.

Simultaneous analysis of lead, mercury and selenium species by capillary electrophoresis with combined ethylenediaminetetraacetic acid complexation and field-amplified stacking injection

Simultaneous analysis of lead, mercury and selenium species by capillary electrophoresis with combined ethylenediaminetetraacetic acid complexation and field-amplified stacking injection

Use of Triethylenetetraminehexaacetic Acid Combined with Field-Amplified Sample Injection in Speciation Analysis by Capillary Electrophoresis

Simultaneous speciation of lead, mercury, and selenium was carried out by capillary electrophoresis. The method used a polyaminocarboxylic acid, triethylenetetraminehexaacetic acid (TTHA), as an off-column complexing agent to form UV-absorbing complexes with the analytes for direct UV detection. TTHA was also added to the background electrolyte for the on-column complexations of the analytes, as well as for improving resolution and detection. To describe the migration behavior of the complexes, a theoretical model, considerating pH value and the concentrations of TTHA and SDS, was proposed. The parameters in the model were calculated on the basis of the experimental data, by nonlinear regression. The results were in good agreement with those from the literature. The model can be used for the prediction of migration behavior and for the optimization of the separation conditions. Field-amplified stacking injection was performed because the complexes were charged. Up to 1500-fold on-line enrichment and down to sub-nanogram-per-milliliter detection limits were obtained for the analytes under the optimal stacking conditions. Finally, the applicability of the method was evaluated on seawater samples.