Effects Of Separation Voltage Research Articles

Use of 3D printing to integrate microchip electrophoresis with amperometric detection.

This paper describes the use of PolyJet 3D printing to fabricate microchip electrophoresis devices with integrated microwire electrodes for amperometric detection. The fabrication process involves 3D printing of two separate pieces, a channel layer and an electrode layer. The channel layer is created by 3D printing on a pre-fabricated mold with a T-intersection. For the electrode layer, a stencil design is printed directly on the printing tray and covered with a piece of transparent glass. Microwire electrodes are adhered over the glass piece (guided by underlaying stencil) and a CAD design of the electrode layer is then printed on top of the microwire electrode. After delamination from the glass after printing, the microwire is embedded in the printed piece, with the stencil design ensuring that alignment and positioning of the electrode is reproducible for each print. After a thermal bonding step between the channel layer and electrode layer, a complete electrophoresis device with integrated microelectrodes for amperometric detection results. It is shown that this approach enables different microwire electrodes (gold or platinum) and sizes (100 or 50µm) to be integrated in an end-channel configuration with no gap between the electrode and the separation channel. These devices were used to separate a mixture of catecholamines and the effect of separation voltage on the potential voltage applied on the working electrode was also investigated. In addition, the effect of electrode size on the number of theoretical plates and limit of detection was studied. Finally, a device that contains different channel heights and a detection electrode was 3D-printed to integrate continuous flow sampling with microchip electrophoresis and amperometric detection.

Screening of eighteen polyphenolic compounds in different carob pekmez by green capillary electrophoresis method

Carob pekmez, a traditional concentrate, has long been produced from Ceratonia siliqua L. for human consumption in Turkey. Although it is already known that carob pekmez contains several classes of polyphenolic substances, a comprehensive analysis of these compounds has not been conducted individually by capillary electrophoresis. Therefore, the polyphenolic compounds were extracted, and a sensitive, green, dependable, simple and rapid method based on capillary electrophoresis with diode array detection was developed for identification and determination of eighteen polyphenolic compounds in five different carob pekmez samples. The effect of separation voltage and pH of the buffer were investigated for determination of optimum conditions. The eighteen compounds were analyzed and fifteen compounds were determined within 17 min without using organic modifier. The developed method was successfully applied to the determination of polyphenolic compounds in five different carob pekmez samples with satisfactory recoveries. As a result of analyses, four major compounds could be determined (gallic acid, vanilic acid, gentisic acid and luteolin) in carob pekmez samples.

Matrix effect and application of field-amplified sample injection in the analysis of four tetracyclines in waters by capillary electrohoresis

The system abilities of two chromatographic techniques, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC), were compared for the analysis of four tetracyclines (tetracycline, chlorotetracycline, oxytetracycline and doxycycline). The pH, concentration of background electrolyte (BGE) were optimized for the analysis of the standard mixture sample, meanwhile, the effects of separation voltage and water matrix (pH value and hardness) effects were investigated. In hydrodynamic injection (HDI) mode, a good quantitative linearity and baseline separation within 9. 0 min were obtained for the four tetracyclines at the optimal conditions; the analytical time was about half of that of HPLC. The limits of detection (LODs) were in the range of 0. 28 - 0. 62 mg/L, and the relative standard deviations (RSDs) (n= 6) of migration time and peak area were 0. 42% - 0. 56% and 2. 24% - 2. 95%, respectively. The obtained recoveries spiked in tap water and fishpond water were at the ranges of 96. 3% - 107. 2% and 87. 1% - 105. 2%, respectively. In addition, the stacking method, field-amplified sample injection (FASI), was employed to improve the sensitivity, and the LOD was down to the range of 17.8-35.5 μg/L. With FASI stacking, the RSDs (n=6) of migration time and peak area were 0. 85%-0. 95% and 1. 69%-3.43%, respectively. Due to the advantages of simple sample pretreatment and fast speed, CE is promising in the analysis of the antibiotics in environmental water.

Determination of sixteen food additives in beverage by capillary zone electrophoresis

A capillary zone electrophoretic (CZE) method for the separation of ten synthetic colorants such as acid red 92, patent blue V, uranine, acid red 1, indigo carmine, black BN, ponceau 6R, quinoline, amaranth, lemon yellow, and six preservatives including benzoic acid, sorbic acid, methyl paraben, ethyl paraben, propyl paraben, butyl paraben in beverages was developed. The effects of separation voltage, capillary temperature, pH and concentration of running buffer on the separation were investigated. A 46 cm x 50 microm uncoated fused silica capillary was used with 70 mmol/L boric acid (pH 9.5) containing 4% (v/v) acetonitrile as background electrolyte solution. The detection wavelength was set at 220 nm, and the run voltage was 30 kV. The injection time was 5 s at 500 mPa and the temperature was 25 degrees C. The linear relationship between the mass concentration and peak area for each of these analytes was obtained in

DETERMINATION OF EPHEDRINE, GASTRODIN, AND LIGUSTRAZIN IN SPIKED RAT PLASMA BY CAPILLARY MICELLAR ELECTROKINETIC CHROMATOGRAPHY

A simple and rapid capillary micellar electrokinetic chromatography (MEKC) method was developed for the separation and determination of ephedrine, gastrodin and ligustrazin in tetraborate buffer by direct UV detection at 200 nm. The effect of separation voltage, the concentration of sodium dodecyl sulfate (SDS) and the buffer pH value on separation was optimized and the following conditions was selected: 20 kV voltage, 15 mM SDS in 50 mM tetraborate buffer at pH = 9.50. The detection limit of these substances was below 1.0 μg/mL, respectively, and the linear range spanned two orders of magnitude. This method was applied to the detection of ephedrine, gastrodin and ligustrazin spiked in rat plasma.

End-column amperometric detection in capillary electrophoresis: influence of separation-related parameters on the observed half-wave potential for dopamine and catechol.

Capillary electrophoresis (CE) was coupled to a micro-electrode-based end-column amperometric detector. The influences of separation voltage, CE buffer concentration, and capillary-to-electrode distance on the observed hydrodynamic voltammetry of dopamine and catechol were studied using a separation capillary with an i.d. of 25 microns. It was found that an increased CE voltage, increased buffer concentration, or decreased capillary-to-electrode distance resulted in a positive shift of the observed half-wave potentials for both dopamine and catechol. At a constant separation current of 1.6 microA, the observed half-wave potential was found to increase with applied separation voltage. Furthermore, when experiments were carried out with a platinum quasi-reference electrode instead of a Ag/AgCl reference electrode, similar shifts in half-wave potential were observed. These results indicate that the observed shifts are an effect of the separation voltage rather than the separation current or a change in the reference potential. The characteristics of end-column detection with and without a fracture decoupler were compared. It was found that the effects of separation voltage, CE buffer concentration, and capillary-to-electrode distance were minimized by the use of a decoupling device. The observed half-wave potentials for dopamine and catechol were more positive when a CE capillary without a decoupler was employed compared to when a decoupler was used. Additionally, using the fracture decoupler, the observed half-wave potentials for both dopamine and catechol were approximately the same as when no CE voltage was applied (i.e., when the hydrodynamic voltammograms were recorded under flow injection conditions).