Capillary zone electrophoresis operating

Altria, K.D. Simpson, C.F. High voltage capillary zone electrophoresis Operating parameter effects upon electro-endosmotic flows and electrophoretic mohihties. Chromatographia 1987, 24, 527-532. 

For capillary zone electrophoresis (CZE) mass spectrometry coupling, another modification of an ESI interface has been developed. This interface uses a sheath flow of liquid to make the electrical contact at the CZE terminus, thus defining both the CZE and electrospray field gradients. This way, the composition of the electro sprayed liquid can be controlled independently of the CZE buffer, thereby providing operation with buffers that could not be used previously, e.g., aqueous and high ionic strength buffers. In addition, the interface operation becomes independent of the CZE flow rate. [62]... 

Capillary zone electrophoresis (CZE) is the most common electrophoretic separation technique due to its simplicity of operation and its flexibility. It is the standard mode for drug analysis, identification of impurities, and pharmacokinetic studies. Other separation modes, such as capillary isotachopho-resis (CITP), micellar electrokinetc chromatography (MEKC), capillary electrochromatography (CEC), capillary gel electrophoresis (CGE), capillary isoelectric focusing, and affinity capillary electrophoresis (ACE), have then-advantages in solving specific separation problems, since the separation mechanism of each mode is different. 

Rudzinski WE, Pin L, Sutcliffe R, et al. 1994. Determination of hexamethylene diisoeyanate in spray-painting operations using capillary zone electrophoresis. Anal chem 66(10) 1664-1666. 

Currently, there are five major modes of operation of CE capillary zone electrophoresis (CZE), also referred to as free solution or free flow capillary electrophoresis micellar electrokinetic chromatography (MEKC) capillary gel electrophoresis (CGE) capillary isoelectric focusing (CIEF) and capillary isotachophoresis (CITP). Of these, the most commonly utilized capillary techniques are CZE and MEKC (Rabel and Stobaugh 1993 Issaq 1999 Smyth and McClean 1998). 

Lin and Wu [137] established a simple capillary zone electrophoresis method for the simultaneous analysis of omeprazole and lansoprazole. Untreated fused-silica capillary was operated using a phosphate buffer (50 mM, pH 9) under 20 kV and detection at 200 nm. Baseline separation was attained within 6 min. In the method validation, calibration curves were linear over a concentration range of 5-100 /iM, with correlation coefficients 0.9990. RSD and relative error were all less than 5% for the intra- and interday analysis, and all recoveries were greater than 95%. The limits of detection for omeprazole and lansoprazole were 2 fiM (S/N = 3, hydroxynamic injection 5 s). The method was applied to determine the quality of commercial capsules. Assay result fell within 94—106%. 

Capillary zone electrophoresis is another technique which has been used to separate products such as organic acids.26 Separation is based on differences in the mobility of analytes exposed to an electric field. Resolution and separation time in such systems depends on factors including electroosmotic flow (EOF), and a number of approaches for adjusting the EOF have been examined. While some of the approaches (pretreatment of capillaries) are not useful as means of process control, adjusting buffer pH and the electric field27 seem to be possible handles for true feedback control of the separation, although closed-loop operation does not seem to have been attempted. 

Bocek and his group [2] developed a method for controlling the composition of the operational electrolyte directly in the separation capillary in isota-chophoresis (ITP) and capillary zone electrophoresis (CZE). The method is based on feeding the capillary with two different ionic species from two separate electrode chambers by simultaneous electromigration. The composition and pH of the electrolyte in the separation capillary is thus controlled by setting the ratio of two electric currents. This procedure can be used, in... 

Capillary Electrophoresis (CE) and Micellar Electrokinetic Chromatography (MEKC). - Di(2-ethylhexyl) thiophosphoric acid (DEHTPA) has been earlier characterised by potentiometric titration, and quantified by capillary zone electrophoresis with carbonate buffer, operating at —20 kV, and using UV detection at 210 nm. ° Also, a comparison has been made of capillary electrophoresis (CE) and liquid chromatography (LC) for the enantiomeric separation of a-phosphonosulfonic acids, where CE used 3-cyclodextrin as chiral selector in a borate electrolyte. Alkylphosphonic acids, at trace levels in water, have been determined by CE coupled online with flame photomeric detection, and alkylphosphonic acid esters have been separated and determined by CE using indirect UV detection. 

Figure 31-1. Diagram of a capillary zone electrophoresis apparatus. A. Normal operation. B. Hydrostatic filling position.

Description of System and its Basic Operating Characteristcs A schematic of the capillary zone electrophoresis (CZE) system is... 

Rudzinski, W. E., Yin, E., England, E., and Charlton, G., Determination of hexamethylene diisocyanate-based isocyanates in spray-painting operations - Part 2 Comparison of high performance liquid chromatography with capillary zone electrophoresis. Analyst, 124, 119-123, 1999. 

Capillary electrophoresis is the generic name for a family of related techniques which have their origin in capillary zone electrophoresis (CZE) and are capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), miscellar electrokinetic capillary chromatography (MECC) and capillary isotachophoresis (CITE). Though the techniques differ significantly in principle of operation they can be carried out largely on the same basic instrumentation. 

Capillary zone electrophoresis. The technique of CZE was first introduced by Jorgenson [86]. Operating principles have already been... 

There are numerous modes of operation in CE. Capillary zone electrophoresis (CZE) is the simplest mode and it was chosen by many authors for PSP toxin analysis. CZE is based on the different migration of solutes in an electric field and toxin separation is performed in narrow-capillaries, which are usually filled only with buffer. Separation occurs because PSP toxins migrate in discrete zones and at different velocities. In this EC mode, selectivity can be readily altered through changes in running buffer pH or by the use of buffer additives. 

Right from the outset of the 1990s, a selection of those interfaces that could be adapted to a routine LC-MS analysis was observable. This trend had been initiated by pharmacological and pharmaceutical research, although it had the TSP interface at its disposal, which was a well-adapted and reliable type of interface that had shown its fiiU capacity in manifold appliances. The sample material, being available only in very limited quantities for such research, and improved separation techniques, as, for example, capillary electrophoresis (CE) or capillary zone electrophoresis (CZE) necessitated different types of interfaces that could be operated with considerably smaller amounts of sample than the TSP interface, which reached its optimized sensitivity with flow rates of about 2 mL min. Such a desirably lower sample demand is guaranteed by atmospheric pressure ionisation (API) interfaces, atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) interface. 

The use of MS in addition to GC/MS includes methods such as capillary zone electrophoresis (CZE/MS), thin layer chromatography (TLC/MS) and others. The major problem in employing these separation-MSD methods is the interface. The very high vacuum required for MS operation requires complete removal of the carrier gas or liquid . Since the present review treats specifically the use of the MSD for the analysis of alkanes and cycloalkanes, we concentrate on the GC/MSD/C (gas chromatography/ mass spectrometry/computerized) method. The MS used can be quadrupole or magnetic and its configuration will, of course, control the power of resolution (PR), the mass range, etc. The ionization mode is also important, e.g. whether El or Cl (see Sections, III.A.l and III.A.2). 

Popsichal, J. Demi, M. Gehauer, P. Bocek, P. Generation of operational electrolytes for isotachophoresis and capillary zone electrophoresis in a three-pole column. J. 

Micellar electrokinetic chromatography performed in capillaries is a separation technique combining some of the operational principles of micellar liquid chromatography and capillary zone electrophoresis. This technique was termed micellar electrokinetic capillary chromatography (MECC) by Burton et al. [79]. MECC uses the addition of a surface-active agent in the working electrolyte, which creates new possibilities for electrophetic separations. 

The primary CE method used for separation of inorganic ions and thus discussed here is capillary zone electrophoresis (CZE). The movement of species in capillary electrophoresis is due to the combination of electrophoretic mobility and electroosmotic flow. In normal operation, the direction of solvent migration, or electroosmotic flow (EOF), is toward the cathode. At pH above about 3, the surface silonal groups (Si-OH) in the... 

CE can be operated in several modes. The approach described in the previous paragraph is referred to as capillary zone electrophoresis, or CZE. A variant called capillary gel electrophoresis uses a capillary tube filled with gel, essentially a miniaturized version of slab-gel techniques. The third variant, and the one of most forensic significance, is micellar electrokinetic chromatography (MEK or MECK). MEK is a modification designed to improve the separation of neutral spedes, which are easily separated from cations and anions, but not well separated among themselves. 

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