ITP-CZE

When a second ITP was cascaded with the first ITP, known as concentration-cascade ITP, SC2 was filled with LE (as in SCI). This concentration-cascade ITP was achieved for 14 anions (200 pM) within 600 s (see Figure 6.18). When ITP was followed by CZE (ITP-CZE), SC2 was filled with a background electrolyte (not necessarily with the greatest mobility). ITP-CZE has been achieved for nitrate, fluoride, and phosphate (10 pM) in the presence of high contents of sulfate (800 pM) and chloride (600 pM) [631]. Subsequent work on the reproducibility on this on-chip ITP separation has been reported [632]. When ITP is performed at pH of greater than 7, there is a common problem of carbonate contamination caused by dissolved atmospheric C02 [633]. 

Recombinant human interleukin-6 ITP-CZE 20-mM ammonium acetate (pH 4.2) Uncoated UV (200nm) ESI-MS [99]... 

Hamoudovd, R., PospSUovd, M., and Spilkova, J., Analysis of selected eonstituents in methanolic extracts of Hypericum perforatum collected in different localities by capillary ITP-CZE, Electrophoresis, 27,4820, 2006. 

Figure 10 ITP-CZE analysis of lO il of five times diluted untreated serum. (A) ITP step in the preseparation capillary, ID 0.8 mm, LE 10mmoll HCI + j3-alanine, pH 3.3, TE lOmmoll" propionic acid. Denoted components migrating behind lactic acid are driven to the second capillary. (B) CZE step in the analytical capillary, ID 0.2mm, BGE SOmmolP propionic acid + -alanine, pH 3.8. The combination of electrolytes corresponds to the T-S-T, system as shown in Figure 6. LOD 5x10 moll ascorbate. Estimated concentration of ascorbic acid in serum 1 5.74mg in serum 2 12.15mg l (Reprinted with permission from Prochazkova A, Kfivankova L, and Bocek P (1998) Quantitative trace analysis of L-ascorbic acid in human body fluids by on-line combination of capillary isotachophoresis and zone electrophoresis. Electrophoresis, vol. 10, p. 302 Wiley-VCH.)...

Besides CZE, recent advances were also made in ITP for the determination of saltforming agents. 

In another report, transient ITP followed by CZE (tITP-ZE) was achieved on a PMMA chip. The stacked zone of fluorescein was visualized in Figure 6.19 [634],... 

The concentration depends only on that of the leading ion it is independent of the initial concentration in the sample. Therefore, ITP can act as an enrichment method, analogous to displacement chromatography and in contrast to zone electrophoresis and elution chromatography. The concentration in the steady state is adjusted to the value given in Eq. (2). If the concentration of the analyte species is lower in the initial sample, the higher steady-state concentration is established. This concentration is independent of the migration distance there is no dilution with a BGE as there is in capillary zone electrophoresis (CZE). 

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 zone electrophoresis (CZE), with direct or indirect photometry and conductivity has become popular in wine analysis. Very little, or sometimes no sample preparation is needed and short analysis times are also apparent advantages of CE and CZE in the analysis of wine. Capillary isotachophoresis (ITP), with conductivity, thermometric, and UV absorption detection, is suitable for the separation of various anionic constituents (organic acids and inorganic anions), currently occurring in wines (Masar et al., 2001). 

Electrophoretic techniques, mainly capillary zone electrophoresis (CZE) and also capillary iso-tachophoresis (ITP) or micellar electrokinetic chromatography (MEKC) have been used in cosmetic analysis (e.g., determination of cationic surfactants in toiletries, parabens in different cosmetics, fluoride, and polyphosphates in toothpaste, hair dyes, or acid preservatives in cosmetic lotions). However, their use is less extensive than LC, probably because the... 

ITP, isotachophoresis CZE, capillary zone electrophoresis RP-CEC, reversed-phase capillary electrochromatography lEF, isoelectric focusing OCEC, open channel electrochromatography. 

As the velocities of the ions are affected by factors such as the charge, pH, concentration, and coions, successful ITP requires careful attention to all these details, which makes it difficult to use in practice. A simpler form of ITP is transient ITP (t-ITP), which is easier to couple to CZE (in the same capillary). Under appropriate conditions, a concentration step due to a brief ITP can occur before the sample enters the separation buffer. In many instances, the t-ITP step occurs accidentally in samples containing high concentrations of salts (self-stacking) or it can be induced by the addition of an appropriate lead-ing/terminating ion to samples with a complex matrix. The method can concentrate both small and large molecules. 

---