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ABSTRACT: An extensive search of published research and review articles indicates that enhancing the sensitivity and resolution of capillary electrophoresis (CE) is a very active area of interest. This review focuses on developments and applications in this field over several years, especially from 2009-present. It first reviews developments in the fields of online sample preconcentration and highly sensitive detection for sensitivity enhancement. The online sample preconcentration techniques cover all methods, from electrophoretic preconcentration, extraction-based preconcentration, micelle-based preconcentration and hybrid preconcentration to nanoparticle-based preconcentration. Attention is also given to multiple dimension separations, additives in buffer solution and capillary inner surface modifications that have been used to enhance the resolution and separation efficiency of complex samples in CE. The additives include nanoparticles, chiral selectors and other buffer additives that have been added to the buffer solution.
Journal of chromatographic science 03/2013; · 0.88 Impact Factor
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ABSTRACT: A novel capillary electrophoresis (CE)-based electrochemical (EC) immunoassay (IA) enhanced by gold nanoparticles (AuNPs) was developed for the determination of shellfish toxins. After competitive immunoreaction between shellfish toxin antigen (Ag), horseradish peroxidase (HRP)-labeled antigen (Ag⁎), and limited antibody (Ab), the immune sample was introduced into capillary and conjugated with AuNPs. The presence of AuNPs modifies the mobilities of analytes and improves separation resolution between analytes. Furthermore, the AuNPs were used as multianalyte carriers of the excess signaling Ag* and the bound enzyme-labeled complex (Ag*-Ab) to achieve an amplification of EC signal. Enhanced resolution and sensitivity were obtained by using bioconjugates featuring HRP labels linked to AuNPs. The four shellfish toxins were baseline separated by using AuNPs. The relative standard deviation (RSD) values of the migration time were 1.3-3.5% for intraday and 3.1-4.6% for interday, respectively. The RSDs of the peak area were 2.8-4.6% for intraday and 4.1-6.9% for interday, respectively. The limits of detection (S/N=3) were in the range of 3.1-36.7ng/L. The enhanced CE based EC-IA with AuNPs labels was successfully applied for the simultaneous determination of four shellfish toxins in shellfish samples. With high resolving power and sensitivity, the proposed method has shown great potential to become an attractively alternative method for simultaneous determination of diverse red tide poisons in shellfish samples.
Biosensors & bioelectronics 09/2012; · 5.43 Impact Factor
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ABSTRACT: Neurotoxic shellfish poisoning is a significant food-borne disease caused by potent cyclic polyether toxins (brevetoxins) that accumulate in the flesh of shellfish. Here we report a new procedure for brevetoxin analysis by capillary electrophoresis-based immunoassay (CE-IA) with electrochemical (EC) detection. In this method, after the competitive immunoreaction in liquid phase, the horseradish peroxidase (HRP)-labeled antigen and the bound enzyme-labeled complex were separated and then the system of HRP catalyzing H(2)O(2)-o-aminophenol reaction was adopted. The limits of detection (signal-to-noise = 3) was determined to be 0.1 ng/mL. Intra-day relative standard deviations (RSD, n = 5) for migration time and peak area were 3.6 and 4.5%, respectively. Inter-day RSD was 6.9 and 7.8% for migration time and peak area, respectively. The CE-IA with EC detection provides a sensitive analytical approach, not previously available, for the determination of brevetoxin-B in shellfish samples.
Journal of chromatographic science 07/2012; · 0.88 Impact Factor
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ABSTRACT: A novel method has been developed by integration of multi-concentration and two-dimensional (2D) capillary electrophoresis
(CE) for simultaneous enhancement of detection sensitivity and separation power in complex samples. Capillary zone electrophoresis
(CZE) was used as the first dimension separation according to mobilities, from which the effluent fractions were further analyzed
by micellar electrokinetic capillary chromatography (MEKC) acting as the second dimension. Cation-selective exhaustive injection
(CSEI) preconcentration method was used to introduce more analytes into the capillary. Furthermore, pH junction and sweeping
dual concentration strategies were employed to avoid sample zone diffusion at the interface. The resulting electrophoregram
was quite different from that of either CZE or MEKC separation. Up to (0.5–1.2) × 104 fold improvements in sensitivity were obtained relative to the conventional electrokinetic injection method. The proposed
method was successfully applied to the determination of drugs in human urine.
Keywordsmulti-concentration-two-dimensional capillary electrophoresis-drug-pharmacokinetic study
Science China-Chemistry 04/2012; 53(5):1183-1189. · 1.02 Impact Factor
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ABSTRACT: A novel two-dimensional (2D) separation method, which hyphenated micellar electrokinetic capillary chromatography (MEKC) and capillary zone electrophoresis (CZE), was developed for analysis of flavonoids in Leonurus cardiaca. The Leonurus cardiaca sample was separated and purified in first dimension by MEKC. Then only a selected portion of the first dimension separation was transferred into the second dimension by pressure. Finally, the zone of flavonoids was separated by CZE. As the key to successful hyphenation of MEKC and CZE, an analyte focusing by micelle collapse (AFMC) concentration method was employed between the two dimensions to release analytes from the micelle interior to a liquid zone and to overcome the sample zone diffusion caused by mobilization pressure. The whole heart-cut 2D separation process can be performed in a conventional CE analyzer. The relative standard deviation of peak height, peak area and migration time were in the range of 2.3-4.2%, 1.5-3.8% and 3.6-5.5%, respectively, and detection limits (S/N=3) were 15-55 ng/mL. The new methodology was applied with success for the flavonoids separation of Leonurus cardiaca.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 06/2011; 879(19):1641-6. · 2.78 Impact Factor
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ABSTRACT: A novel sweeping under controlled electroosmotic flow scheme was developed for preconcentration and determination of neutral compounds by micellar electrokinetic chromatography (MEKC). An anionic surfactant, sodium dodecyl sulfate (SDS), was added into the buffer for sweeping and separation. By controlled electroosmotic flow (EOF) equal to the counter electrophoretic flow, the surfactants were at an immobile state in capillary. The neutral analytes with sample solution was injected electroosmotically into capillary and swept by SDS micelle for essentially an unlimited volume. The injected sample plug lengths for phlorizin and quercitrin under 18 kV for 70 min were experimentally estimated as 1532 cm, corresponding to 51-fold the effective capillary length. The sweeping under controlled EOF scheme resulted in increased detection factors for phlorizin and quercitrin of 2.3 × 10⁴ and 2.1 × 10⁴ using 70 min injection relative to a traditional pressure injection. The proposed method has been adopted to analyze trace phlorizin and quercitrin in urine samples successfully.
Journal of pharmaceutical and biomedical analysis 05/2011; 56(2):330-5. · 2.45 Impact Factor
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ABSTRACT: A novel integrated concentration/separation approach involving online combination of sweeping with electrokinetic injection and analyte focusing by micelle collapse (AFMC) with heart-cutting two-dimensional (2D) capillary electrophoresis (CE) in a single capillary was developed for analysis of Herba Leonuri and mouse blood samples. First, a new sweeping with an electrokinetic injection preconcentration method was developed to inject a large volume sample solution and significantly enhance detection sensitivity. Then, the preconcentration scheme was integrated to the 2D-CE to provide significant analyte concentration and extremely high resolving power. The sample was preconcentrated by sweeping with electrokinetic injection and separated in first dimension micellar electrokinetic chromatography (MEKC). Then, only a desirable fraction of the first dimension separation was transferred into the second dimension of the capillary by pressure and further analyzed by capillary zone electrophoresis (CZE) acting as the second dimension. As the key to successful integration of MEKC and CZE, an AFMC step was integrated between the two dimensions to release analytes from the micelle interior to a liquid zone and to overcome the sample zone diffusion caused by mobilization pressure. The injected sample plug lengths for flavonoids under 15 kV for 60 min were experimentally estimated as 546 cm. The dual concentration methods resulted in the increased detection factors of 6000-fold relative to the traditional pressure injection method. The relative standard deviation (RSD) values of peak height, peak area, and migration time were 2.7-4.5%, 1.9-4.3%, and 4.7-6.8% (n = 10), respectively. The limits of detection (S/N = 3) were in the range of 7.3-36.4 ng/L, and the theoretical plate numbers (N) were in the range of 1.7-4.3 × 10(4) plates/m. This method has been successfully applied to determine flavonoids in Herba Leonuri and postdosing mouse blood samples. The pharmacokinetic study also demonstrated that the proposed concentration/separation method was convenient and sensitive and would become an attractively alternative method for online sample concentration and separation in complex samples.
Analytical Chemistry 02/2011; 83(4):1291-9. · 5.86 Impact Factor
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ABSTRACT: A new two dimensional method, which interfaced capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) by a polytetrafluoroethylene (PTFE) tube with a hole of 30-40 microm diameter on the top, was developed for the analysis of drugs and their enantiomers. The CZE was used as the first dimensional separation, from which the eluting components were transferred and further analyzed by MEKC. Online dual concentration method, pH junction-sweeping, was used to avoid sample zone diffusion at the interface. The separation efficiencies and detection limits were (2.8-4.3) x 10(4)/m and 0.015-0.052 mg/L, respectively. The proposed method has successfully demonstrated that in the separation of four drugs and their enantiomers in urine samples, the relative standard deviations (RSDs) of peak area and migration time were in the ranges of 1.7%-3.8% and 1.3%-4.6%, respectively. The method was proved to have good reproducibility, high sensitivity and resolution, large peak capacity. It is reliable and suitable to separate and determine multi-drugs and their enantiomers in urine samples simultaneously.
Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 04/2010; 28(4):397-401.
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ABSTRACT: A novel method to detect beta-antagonists in rat blood was developed by combining heart-cutting 2-D CE in a single capillary with on-column electrochemical (EC) detection. The blood sample was purified in first dimension by non-micellar CZE separation. Then only a desirable fraction of the first dimension separation was transferred into the second dimension of the capillary by pressure. Finally, the purified sample was separated by MEKC. On-line dual concentration method, field amplified sample stacking and sweeping, was employed to accumulate the purified components that effectively counteracted the sample zone diffusion during the mobilization pressure step. A field decoupler joint and an EC detection cell were employed for on-column EC detection. After optimizing the analytical conditions, the RSD of peak height, peak area and migration time were 2.1-4.3%, 1.5-3.9% and 0.7-1.8% (n=10), respectively. This method has been successfully applied to determine beta-antagonists in postdosing rat blood sample. The pharmacokinetic study also demonstrated that the proposed heart-cutting 2-D CE with on-column EC detection was convenient, sensitive and would become an attractively alternative method for on-line sample cleanup and separation in complex samples.
Electrophoresis 10/2009; 30(19):3449-57. · 3.30 Impact Factor
