Biomedical subjects

M W Dong

Publications and source records attributed to M W Dong.

5 recordsLinked to original sources

PubMed2003

Mass spectrometry-compatible ICH (International Conference on Harmonization) impurity analysis with a high-pH mobile phase advantages and pitfalls.

Recent advances in bonding chemistry and novel silica synthesis have significantly extended the pH range of silica-based HPLC columns. This extended range now enables the analysis of water-soluble basic drugs at high pH without ion-pairing reagents, thus offering an alternative approach to assay or impurity analyses. This paper describes the many advantages and potential pitfalls of using high-pH mobile phases in the development of MS-friendly LC gradient impurity analytical methods for water-soluble basic drugs under International Conference on Harmonization (ICH) guidelines. Operating at high-pH provides excellent peak shapes and retention, and accentuates selectivity differences of structurally similar impurities and degradants. However, several problems unique to the use of high-pH mobile phases, such as column lifetime, robustness of pH adjustments, peak fronting, and on-column dimerization, were encountered. Each of these problems is discussed with its respective remedy.

Hydrogen-Ion Concentration↗

PubMed1992

Tryptic mapping by reversed phase liquid chromatography.

This chapter reviews the technique of tryptic mapping by reversed phase liquid chromatography by describing its fundamental principles, present status, and recent advances as well as its uses and limitations. Two commonly used S-carboxymethylation/tryptic digestion procedures are documented. Column and instrumental requirements are described and illustrated with examples. Mobile phase selection and operating variables (tG, F) are also discussed in terms of their effects on both peptide resolution and detection sensitivity.

Amino Acid Sequence↗

PubMed1990

Factors influencing the performance of peptide mapping by reversed-phase high-performance liquid chromatography.

Factors controlling the performance of peptide mapping on reversed-phase columns were systematically evaluated. Performance criteria included resolution (peak capacity and selectivity), system reproducibility, sensitivity and analysis speed. Column configuration, characteristics of packing materials, mobile phase composition, operating variables and instrumental designs were found to influence the performance of peptide mapping. Considerations for peptide identification techniques are discussed.

Chromatography, High Pressure Liquid↗

PubMed1990

Rapid analysis and purification of polymerase chain reaction products by high-performance liquid chromatography.

This report describes the use of high-performance liquid chromatography (HPLC) for the rapid analysis and purification of the polymerase chain reaction products. Employing a new anion-exchange nonporous column, efficient separations of both DNA restriction fragments and amplified PCR products are achieved in 10 to 20 minutes and quantitated within +/- 10%. The performance of the HPLC technique is described in terms of resolution, reproductibility, sensitivity and micropreparative capability and compared to that of gel electrophoresis for this application.

Chromatography, High Pressure Liquid↗

PubMed1988

Factors affecting the ion-pair chromatography of water-soluble vitamins.

Factors controlling the separation of seven water-soluble vitamins on reversed-phase columns were systematically evaluated. Factors studied include both mobile phase constituents and column parameters. Data showed that a mobile phase containing hexanesulfonate (5 mM), methanol (15%), acetic acid (1%), and triethylamine (0.10-0.13%) yielded excellent separations with several C8 and C18 columns. Lowering the methanol concentration in the mobile phase enhanced the resolution of early eluting peaks, while the triethylamine level controlled the peak shape and retention of thiamine. The analytical precision, robustness, and sensitivity of the developed liquid chromatographic (LC) separation were evaluated. The stability of the LC separation was found to be satisfactory for over a 4-month period.

Acetates↗