Cationic selective exhaustive

Figure 26-34 Cation-selective exhaustive injection—sweeping.

K. Isoo and S. Terabe, Analysis of Metal Ions by Sweeping via Dynamic Complexation and Cation-Selective Exhaustive Injection in Capillary Electrophoresis, Anal. Chem. 2003, 75, 6789. 

CSEI-sweep cationic selective exhaustive injection-sweeping... 

Isoo, K. and Terabe, S., Analysis of metal ions by sweeping via dynamic complexation and cation-selective exhaustive injection in capillary electrophoresis. Anal. Chem., 75, 6789, 2003. 

Combinations of online procedures are often employed in environmental applications. Examples include the analysis of trace metal ions in factory wastewater by a combination of cation-selective exhaustive injection (CSEI) (a form of stacking, CZE format) and sweeping. In this latter case, sweeping was promoted by dynamic complexation with EDTA, used as carrier. The same CSEI principle has also been applied to the analysis of quaternary ammonium herbicides and environmentally relevant aromatic amines in water, both followed by sweeping with SDS. 

Quirino, J. P. and Terabe, S., Approaching a million-fold sensitivity increase in capillary electrophoresis with direct ultraviolet detection Cation-selective exhaustive injection and sweeping, Analytical... 

Lin Y-H, Li J-H, Ko W-K, Wu S-M (2006) Direct and sensitive analysis of methamphet-amine, ketamine, morphine and codeine in human urine by cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography. J Chromatogr A 1130(2) 281-286... 

Chiang H-Y, Sheu S-J (2004) Analysis of ephedra-alkaloids using sweeping and cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography methods. Electrophoresis 25 670-676. doi 10.1002/elps.200305729... 

Cation- and anion-selective exhaustive injection sweeping (CSEI-sweep and ASEI-sweep) techniques are also available in MEKC. CSEI-sweep and ASEI-sweep are combinations of two online preconcentration techniques, sample stacking with electrokinetic injection and sweeping, that can provide more than 100,000-fold enhancements in detection sensitivity. An electropherograms of tap water analysis by CSEI-sweep-MEKC is illustrated in Figure 7. The results of this study suggest that CSEI-sweep-MEKC can be used for the analysis of quaternary ammonium herbicides in drinking water. 

As the DI plant becomes exhausted, silica leakage occurs in the treated MU water and the pH falls abruptly. Furthermore, where sodium ion leakage occurs from the cation bed, it produces a regenerative effect on the anion bed, which may also lead to silica leakage. To differentiate between the two phenomena, sodium ion leakage from the cation bed should be assessed directly using selective sodium-ion electrodes, flame photometric analysis, or other appropriate test methods. 

It was thought unnecessary to give references to work earlier than 1961, since these will be found in the author s book The Chemistry of Cationic Polymerisation. As far as later work is concerned, the references are not intended to be exhaustive, but were selected so as to give the reader an easy entry into the literature. 

Copolymerization of styrene with diolefins provides further support that monomer coordinates with the cationic site prior to addition. Korotkov (218) showed that in homopolymerizations styrene is more reactive than butadiene, but in copolymerization the butadiene reacted first at its homopolymerization rate and when it was exhausted the styrene reacted at its homopolymerization rate. This interesting result has been duplicated by Kuntz (245) and analogous results have been obtained by Spirin and coworkers (237) for the styrene-isoprene system. Presumably, the diene complexes more strongly than styrene with the lithium and excludes styrene from the site. That the complex occurs at a cationic site, rather than at the anion or the metal-carbon bond, is indicated by the fact that dienes form more stable complexes than styrene with Lewis acids (246). It should be emphasized that selective monomer coordination is not the only factor influencing reactivities in copolymerizations. Of greatest importance are the relative reactivities of the different polymer anions. The more resonance-stabilized anion is more readily formed and is less reactive for polymerizing the co-monomer. 

For strongly cationic compounds, such as aliphatic amines, where silanol effects are most dramatic, the separation can be developed by several good approaches, the first of which is column selection. Choosing a column packed with polymerically bound silica and exhaustive endcapping will deactivate most of the... 

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