New silanization coating for DNA fragment analysis by capillary electrophoresis

Capillary electrophoresis of polycationic poly(amidoamine) dendrimers

Generation 2 to generation 5 poly(amidoamine) (PAMAM) dendrimers having different terminal functionalities were analyzed by capillary electrophoresis (CE). Polyacrylamide gel electrophoresis was also used to assess the composition of the individual generations for comparison with the CE results. Separation of PAMAMs can be accomplished by either using uncoated silica or silanized silica capillaries, although reproducibility is poor using the uncoated silica capillary. To improve run-to-run reproducibility, silanized capillary was used and various internal standards were also tested. Relative and normalized migration times of primary amine terminated PAMAM dendrimers were then determined using 2,3-diaminopyridine (2,3-DAP) as an internal standard. Using silanized capillaries and internal standards, the relative and normalized migration times are fully reproducible and comparable between runs. Apparent dimensionless electrophoretic mobilities were determined and the results were compared to theoretical calculations. It is concluded that for PAMAMs a complex separation mechanism has to be considered in CE, where the movement of the ions is due to the electric field, but the separation is rather the consequence of the adsorption/desorption equilibria on the capillary wall ("electrokinetic capillary chromatography"). The described method may be used for quality control and may serve as an effective technique to analyze polycationic PAMAM dendrimers and their derivatives with different surface modifications.

Polypyrrole-coated capillaries for capillary zone electrophoresis

Fused-silica capillaries are permanently coated by silanization with 3-{[3-(N-pyrrole)-2-hydroxypropyl]amino}propyltriethoxysilane followed by oxidative polymerization of the pyrrole moieties with iron (III) or peroxodisulfate in the presence of chloride, perchlorate, or dextransulfate as anions. This approach allows to modulate the EOF in its magnitude as well as in its direction. With the small anions chloride and perchlorate, the EOF is reversed below pH 5 while with the large dextransulfate polyanions (DS) the EOF is relatively constant over the pH range from 2.5 to 9.4. This can be of advantage at low pH, at which the EOF of uncoated capillaries is close to zero. Application for separation of some herbicides is shown. The lifetime of PP-modified capillaries is satisfactory: the decrease in EOF is less than 3% during 80 analyses (160 min) and less than 5% over three months of storage. The reproducibility of capillary modification is about 5% (RSD of EOF).