Capillary detection

High Voltage Power Supply Separation Capillary Detection Capillary ... 

Fig. 3.1 shows a schematic of a typical CE system set-up. Separations are achieved by filling a capillary with an electrolyte solution. A volume of sample is then injected into the end of the capillary furthest from the detector, usually performed by applying a pressure to the sample vial whilst the capillaiy is inserted into the sample vial. The capillary is then immersed in buffer reservoirs, which are placed at either end of the capillary. An electrical field is then applied (between 1 and 30 kV) which causes the compounds in the sample mixture to migrate along the capillary towards the on-capillary detection system. The smaller, higher-charged compounds will reach the detector window first. 

Fig.. . 9. Separation of a mixture of basic, acidic and neutral drugs using a standard MEEKC method. Separation conditions 0.819 w/v, (K tane. 6.619 w/v. butan-I-ol.. . .M9 s/ sixlium dtxlccyl sulphate and 89.279 w/w 10 mM sodium tetraborate butTer. 15 kV.. 0 cm x 50 pm i.d. capillary (detection window at 22 cm). 40°C. 200 nm. Reproduced with permission from 116],...

Most forms of detection in High-Performance Capillary Electrophoresis (HPCE) employ on-capillary detection. Exceptions are techniques that use a sheath flow such as laser-induced fluorescence [1] and electrospray ionization mass spectrometry [2],... 

In high-performance liquid chromatography (HPLC), postcolumn detection is generally used. This means that all solutes are traveling at the same velocity when they pass through the detector flow cell. In HPCE with on-capillary detection, the velocity of the solute determines the residence time in the flow cell. This means that slowly migrating solutes spend more time in the optical path and thus accumulate more area counts [3]. 

Capillary electrophoresis instrumentation is fully automated with respect to sample injection, separation, on-capillary detection, and postrun data analysis. 

Analytes Buffer Capillary Detection Separation Parameters Nature, state, concentration, solubility and solvent Type, additives, concentration, pH Length, diameter, surface properties, maintenance Type, sensitivity Current strength, temperature, separation time... 

In addition to publications detailing criteria for method development, numerous examples of the use of CD-based CE have appeared in the literature. To illustrate method performance, a paper by Zhou et al. details the development and validation of methodology for the determination of enantiomeric purity of the compound shown in Figure 8a. An optimized separation (Fig. 8b) was obtained using 1.5% (w/w) sulfated-/3-CD in pH 2.5 sodium phosphate buffer (25 mM), a 63-cm (56 cm effective length) x 75- xm capillary, detection at 200 nm, a temperature of 30 °C, and an electric held strength of —15 kV. Sample solutions of 0.5 mg/ml in 90/10 (v/v) water/acetonitrile were introduced using hydrodynamic injection at 50 mbar for 3 s. 

The PCR recipe included intercalating dye, ethidium bromide (0.2 ig/mL), to enable in-capillary detection of the amplification. Direct detection of PCR amplicons was achieved by placing the capillaries on a UV transilluminator... 

Peptides and Proteins CE Modes Separation Buffers Capillary Detection Ref. 

Pump, autosampler, capillaries, detection cell Hot water, isopropanol, 6 N HNO (followed by water flush to neutral)... 

On-column capillary detection is the most widely employed configuration in CE with fluorescence detection, as shown in Figure 9.3a. A small window is made on the capillary by burning off a section... 

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