Stable capillary coating with successive multiple ionic polymer layers

Electrophoretic mobility-assisted identification of proteins by nanoelectrospray capillary electrophoresis/mass spectrometry under methanolic conditions

A novel method for electrophoretic mobility-assisted identifications of proteins, using capillary electrophoresis/mass spectrometry (CE/MS) under methanolic conditions, was developed. The number of functional groups of the enzymatic digest peptides was estimated from a single run CE/MS analysis and utilized as an additional tag for database searching in addition to the mass map of the peptides. The additional amino acid information thus obtained can improve the confidence level of the protein identification. The database searching software algorithm ProFound was modified to accept the tag, based on this new concept. In this study, optimization of the CE/MS conditions for the estimation of basic functional groups was performed as an example. An accurate value of the number of such functional groups was obtained from CE characteristics when methanolic buffer (methanol/formic acid/water = 60:20:20) was used, via an excellent correlation (r = 0.997) between the number of functional groups of the peptides and [MW((2/3))]. The mass spectrometry sensitivity was also improved when using the methanolic buffer in comparison with that obtained using aqueous 1% formic acid buffer. The identification of a protein of Saccharomyces cerevisiae, which was separated by two-dimensional electrophoresis, was performed using the methanolic buffer in combination with sheathless nanoelectrospray CE/MS. A protein spot that had not been identified by MALDI-TOFMS and LC/MS/MS was successfully identified using this new method.

Capillary electrophoresis of drugs: current status in the analysis of pharmaceuticals

The current status of capillary electrophoresis (CE) in pharmaceutical analyses is reviewed with about 300 references, mainly from 1996 until 1999. This article covers the use of CE for assay and purity determination of the main component, analysis of natural medicines, antisense DNA, peptides, and proteins. Analysis of hydrophobic and/or electrically neutral drugs by electrokinetic chromatography, capillary electrochromatography and nonaqueous CE is critically evaluated. Detailed techniques for the separation of enantiomers are given in the text with some actual applications. Furthermore, this review includes sensitivity and regulatory aspects for the actual use of CE in new drug applications (NDA). The analytical validation required for CE in NDA is also treated.

Stable cationic capillary coating with successive multiple ionic polymer layers for capillary electrophoresis

A coated capillary modified with a cationic polymer was developed by using a novel coating procedure, successive multiple ionic-polymer (SMIL) coating. The SMIL coating was achieved by first attaching the cationic polymer to the capillary inner wall, and then the anionic polymer to the cationic polymer layer, and finally the cationic polymer to the anionic polymer layer. The stability of Polybrene (PB)-modified capillary made by SMIL coating was remarkably improved in comparison with a conventional PB-modified capillary. It endured during 600 replicate analyses and also showed strong stability against 1 M NaOH and 0.1 M HCl. The relative standard deviation of the run-to-run, day-to-day, and capillary-to-capillary coating was all below 1%, and good reproducibilities were obtained. The PB-modified capillary made by SMIL coating was applied to the basic protein analyses. It gave good performances for the protein analyses even when the pH of the electrolyte was near the isoelectric point (pI) of the protein. In addition, 0.1 M NaOH rinse prior to the sample injection allowed the reproducible analysis of a highly adsorptive sample such as plasma because the adsorbed sample could be flushed out of the capillary. Besides protein analyses, an efficient analysis of the cationic drugs by capillary electrophoresis/mass spectrometry (CE/MS) was also possible.