Isotachophoresis buffer systems

And CITP is favorably utilized in the analysis of low-molecular-weight ionic species. A difficulty often arises with finding suitable buffer systems that provide leading and terminating ions and also form the appropriate buffer pH. One of the advantages is that the capillary can be loaded with sample up to 30-50% of its length, enabling the analysis of very dilute samples. Furthermore, the principle of predetermined solute concentrations in isotachophoresis is also used as preconcentration step for very dilute samples prior to CZE, MEKC, or CGE. 

Capillary isotachophoresis (CITP) is an electromigration technique, which is performed using a discontinnous buffer system, formed by a leading electrolyte (LE) and a terminating electrolyte... 

Capillary isotachophoresis (CITP) — An electrophoretic separation technique (-> electrophoresis) in a discontinuous -> buffer system, in which the analytes migrate according to their -> electrophoretic mobilities, forming a chain of adjacent zones moving with equal velocity between two solutions, i.e., leading and terminating electrolyte, which bracket the mobility range of the analytes. Ref [i] Riekkola ML, Jonsson jA, Smith RM (2004) Pure Appl Chem 76 443... 

Isotachophoresis is similar to isoelectric focusing but includes the use of additional ampholines or multiphasic buffer systems to act as spacers to improve the separation and resolution. Each of these techniques can be run using columns, tubes, thin layers, or slabs and are comprehensively dealt with by Andrews (1981). 

The advantage of isotachophoresis from the point of view of preparative scale operations is the increase in resolution with increasing load. A higher load increases the length of individual zones. Separation is carried out in an adapted LKB prepara-tive electrophoresis column (Uniphor) and the following buffer systems are recommended by Svendsen [293]. 

Future trends in the separation area will include translation of all these methods to microchip format, which promises to lead the next revolution in chemical analysis. MEKC and isotachophoresis, a CE separation technique in a discontinuous buffer system, have already been adapted to microchips and applied to assay herbicides, biogenic amines, and ions. Micro-channels on a chip-like structure are likely to be exploited more frequently in CE after further development of nanotechnology because it results in extremely rapid separations that consume only picoliter sample volumes and introduce the possibility of merging sample preparation and analysis in a single device. 

Isotachophoresis is a technique based on the principles of moving boundary electrophoresis. Two buffer systems are used a leading electrolyte and a trailing electrolyte. The leading electrolyte has a higher mobility than the fastest sample component likewise the trailing electrolyte has a slower mobility than the slowest component. When an electric field is applied... 

An on-line coupling of capillary electrophoresis or reversed anionic capillary isotachophoresis (CITP) with electrospray ionization mass spectrometry has been described for the separation of monophosphate nucleosides, pyridine, and flavin dinucleotides (87). The combination with CITP gives an enhancement of sample loadability and concentration sensitivity in capillary zone electrophoresis/ mass spectrometry (CZE/MS). MS-compatible buffer systems were developed (trailing electrolyte, 10 mM caproic acid pH 3.4 leading electrolyte, 7 mM HCl/ 13 mM P-alanine pH 3.9). This technique seems to be valuable for the trace analysis of DNA and RNA, e.g., to study radiation-induced DNA damage. 

The main separation modes used in CE are capillary zone electrophoresis (CZE), micellar electrokinetic capillary chromatography (MEKC), capillary isotachophoresis, capillary gel electrophoresis, and capillary isoelectric focusing. CZE and MEKC are used most often. CE buffers are generally aqueous-based, though nonaqueous systems are exploited as well, particularly for analytes that are insoluble or sparingly soluble. 

The principle of isotachophoresis was used in a study for measurement of ascorbic acid in urine, neuroblastoma cell extracts, and cell-free system (99). HCl/p-alanine-methylceUulose was used as leading buffer and caproic acid as terminating electrolyte. The column was 23 cm X 500 pm, but the type of coluum coating was not mentioned. UV detection at the wavelength of 254 nm was used. 

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