HPCE high performance capillary detection

A high performance capillary electrophoresis (HPCE) was described for the separation and simultaneous determination of OTC, TC, CTC, DC, and chloramphenicol in honey. The use of buffer pH 3.2 containing 0.02 mol/L Na2HP04 and 0.01 mol/L citric acid with addition of 4% (v/v) A-methylmorpholine and 12% (v/v) acetonitrile demonstrated a good separation of these five antibiotics within 20 min. The proposed method gave detection limit (signal to noise ratio > 5) of 20 pg/L for OTC [26],... 

In this book, the focus is on the use of high performance liquid chromatography (HPLC) for the separation and detection of biochemical components produced from enzymatic reactions. But the purpose of the book is also to introduce HPLC and high performance capillary electrophoresis (HPCE) as methods applicable for separation and detection of a variety of components, even those not produced by enzymatic reactions. 

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]. 

One cannot overestimate the importance of fluorescence detection in high-performance capillary electrophoresis (HPCE) [1], The success of the human genome project along with the forthcoming revolutions in forensic testing and genetic analysis might not have occurred without the sensitivity and selectivity of laser-induced fluorescence (LIF) detection. 

Electrophoretic assays may be used to characterize the purity and homogeneity of biopharmaceuticals, based mainly on an ability to differentiate chemical and molecular changes in the compound as a result of oxidation, denaturation, aggregation, and deamidation [11]. Well-established techniques include isoelectric focusing (lEF) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), whilst high-performance capillary electrophoresis (HPCE), utilizing a variety of detection systems, may also be used for routine applications. 

The instrumentation of HPCE is uncomplicated (see the schematic drawing in Figure 1). Briefly, both ends of the narrow-bore fused silica capillary are immersed into reservoirs containing a buffer solution that also fills the capillary. The reservoirs also contain electrodes that provide electrical contact between the high-voltage power supply and the capillary. The sample is loaded onto the capillary by replacing one of the buffer reservoirs by a sample reservoir and applying external pressure (hydrodynamic injection) or an electric field (electrokinetic injection). After the injection, the reservoir is replaced, the electrical field is applied, and the separation starts. The detection is usually performed at the opposite end of the capillary (normal polarity mode). UV/vis detection is by far the most common detection technique in HPCE. Other techniques include fluorescence, amperometry, conductivity, and mass spectrometry. Modem HPCE instruments are fully automated and thereby allow easy operations and precise quantitative analyses. 

---