Biomedical subjects

Dirk Bandilla

Publications and source records attributed to Dirk Bandilla.

4 recordsLinked to original sources

PubMed2006

Pore size characterization of monolith for electrochromatography via atomic force microscopy studies in air and liquid phase.

This paper investigates the use of scanning electron microscopy (SEM) and atomic force microscopy (AFM) for the characterization of monoliths used in capillary electrochromatography (CEC) while focusing on the nature of the information available from both techniques. SEM imaging revealed a compact structure of non-porous micrometer sized particles homogeneously agglomerated. With a simple AFM methodology, we found by direct observation that the same material exhibits mesopores in the nanometer range while SEM showed non-porous surfaces. These results obtained by AFM clearly showed that micrometer sized particles shrank and micrometer sized pores increased in the monolith when wetted. Thus, AFM was capable of demonstrating the morphological differences between wet and dried monolithic materials that are not possible by other imaging methods at micrometer resolution.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2006

Characterization of UV-transparent capillaries for CEC and CE.

This short communication describes features of UV-transparent capillaries employed for CEC and CE. A waveguide effect was observed when using UV-transparent capillaries. Through imaging with SEM, the UV-transparent coating was found to be highly porous unlike polyimide coating, which did not exhibit any porosity at all. Prolonged exposure to several commonly employed solvents with elevated pH caused abrasion of the coating at the capillary tip but no swelling of the UV-transparent coating was observed. Lastly, four different cutting techniques were compared to obtain smooth capillary tips.

Chromatography, Liquid↗

PubMed2004

Capillary electrochromatography of peptides and proteins.

This review surveys the accomplishments in the separation of peptides and proteins by capillary electrochromatography (CEC) over the last decade. A significant number of research articles have been published on this topic since the last review. Peptide and proteins separations have been carried out in all three formats of CEC, i.e., packed bed, continuous bed and open-tubular (OT) format. In addition to electrophoresis, different chromatographic modes have been successfully exploited with the most prevalent being reversed-phase mode followed by ion-exchange. Although many researchers continue to use model proteins and peptides primarily to evaluate the performance of novel stationary phases some researchers have also applied CEC to the analysis of real-life samples. The potential of CEC to yield complementary information and sometimes a superior separation with respect to established techniques, i.e., microbore HPLC and capillary electrophoresis has been demonstrated. Instrumental modifications in order to facilitate coupling of CEC to mass spectrometry have further upgraded the value of CEC for proteomic analysis. Capillaries are still the separation vehicle of choice for most researchers yet the microfluidic platform is gaining momentum, propelled particularly by its potential for multitasking, e.g., performing different chromatographic modes in series.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2003

Protein separation by monolithic capillary electrochromatography.

This work presents the separation of model proteins by capillary electrochromatography involving a monolithic stationary phase with C4 functionality. The monolith was fabricated in UV-transparent capillaries by employing a slight modification of a recently published photopolymerization procedure. With the number of theoretical plates per column ranging between 11000 and 33000, the separation efficiency proved to be lower than capillary zone electrophoresis where plate numbers ranged between 18000 and 66000. However, higher resolution was obtained due to the additional chromatographic separation mechanism. Inter- and intra-column reproducibility were evaluated, the latter could be significantly improved when using a rinsing procedure that contained 0.05% sodium dodecylsulfate in the mobile phase. Plate heights became nearly independent of mobile phase velocities higher than 0.5 mm/s indicating that high velocities can be applied without sacrificing efficiency. Furthermore, peak heights showed a dependence on injection times. For proteins, an increase in capacity factors was found when increasing the percentage of organic solvent in the mobile phase.

Chromatography, Micellar Electrokinetic Capillary↗