Determination of a new antibacterial agent (Ro 23-9424) by multidimensional high-performance liquid chromatography with ultraviolet detection and direct plasma injection

Off-line comprehensive two-dimensional high-performance liquid chromatography system with size exclusion column and reverse phase column for separation of complex traditional Chinese medicine Qingkailing injection

A comprehensive two-dimensional liquid chromatography system was constructed on the combination of size exclusion chromatography (SEC) and reverse phase liquid chromatography (RPLC). The first dimension used a SEC column with 300 mm x 8mm i.d., packed with Toyopearl HW-40S. The column was eluted with 0.05 mol/l Tris-HCl (pH 6.9) at a flow rate of 0.4 ml/min. The second dimension used a RPLC column with 100 mm x 4.6mm i.d., which was operated in gradient form at a flow rate of 1.0 ml/min. An automatic switching valve was used to collect the effluent of the SEC column every 3 min, and the effluent was automatically injected into the RPLC column. Mass spectrometer was used for peak identification. This system was used to separate Qingkailing injection, a traditional Chinese medicine (TCM). The result showed that the total peak capacity of this system could reach 1134 and the qualitative analysis of seven chemical components of the Qingkailing injection was accomplished by this system. The results show that comprehensive two-dimensional liquid chromatography system is of great importance and high value in the separation of complex TCM.

Application of a semipermeable surface column for the determination of amoxicillin in human blood serum

A high-performance liquid chromatography column-switching system for the automated determination of amoxicillin in human serum was developed as a more efficient alternative for the already existing systems with off-line sample pretreatment. The column-switching system consists of a semipermeable surface (SPS) column and an analytical reversed-phase (RP) C18 column. After centrifuging, pure serum samples were injected into the column-switching system. Clean-up, with regard to removal of proteins, was performed on the SPS column. The fraction containing amoxicillin was concentrated on the analytical RP-C18 column. Finally, chromatography and detection were performed with the RP-C18 column using UV detection at 234 nm. The total analysis time was 15 min. The method has proven to be reliable and to be more time- and resource-efficient compared to previously used methods with off-line sample clean-up. It is now used in bioavailability studies for the development of new amoxicillin formulations.

Comprehensive two-dimensional high-performance liquid chromatography for the isolation of overexpressed proteins and proteome mapping

A two-dimensional liquid chromatographic system is described here which uses size-exclusion liquid chromatography (SEC) followed by reversed-phase liquid chromatography (RPLC) to separate the mixture of proteins resulting from the lysis of Escherichia coli cells and to isolate the proteins that they produce. The size-exclusion chromatography can be conducted under either denaturing or nondenaturing conditions. Peaks eluting from the first dimension are automatically subjected to reversed-phase chromatography to separate similarly sized proteins on the basis of their various hydrophobicities. The RPLC also serves to desalt the analytes so that they can be detected in the deep ultraviolet region at 215 nm regardless of the SEC mobile phase used. The two-dimensional (2D) chromatograms produced in this manner then strongly resemble the format of stained 2D gels, in that spots are displayed on a X-Y axis and intensity represents quantity of analyte. Following chromatographic separation, the analytes are deposited into six 96-well (576 total) polypropylene microtiter plates via a fraction collector. Interesting fractions are analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS) or electrospray mass spectrometry (ESI/MS) depending on sample concentration, which both yield accurate (2 to 0.02%) molecular weight information on intact proteins without any additional sample preparation, electroblotting, destaining, etc. The remaining 97% of a fraction can then be used for other analyses, such Edman sequencing, amino acid analysis, or proteolytic digestion and sequencing by tandem mass spectrometry. This 2D HPLC protein purification and identification system was used to isolate the src homology (SH2) domain of the nonreceptor tyrosine kinase pp60c-src and beta-lactamase, both inserted into E. coli, as well as a number of native proteins comprising a small portion of the E. coli proteome.

Two-dimensional SEC/RPLC coupled to mass spectrometry for the analysis of peptides

A two-dimensional liquid chromatography system is described here which uses size exclusion liquid chromatography (SEC) followed by reversed phase liquid chromatography (RPLC) to separate the mixture of peptides resulting from the enzymatic digestion of a protein. A novel LC/LC interface, using two RPLC columns in parallel rather than storage loops, joins the two chromatographic dimensions. This new interface design permits the use of conventional analytical diameter HPLC columns, 7.8 mm for SEC and 4.6 mm for RPLC, making construction and maintenance of this system very easy. The reversed phase chromatography utilizes 1.5 microns diameter, nonporous C-18 modified silica particles, which produce fast and efficient analyses. Following the high-resolution two-dimensional chromatographic separation, an electrospray mass spectrometer detects the peptide fragments. The mass spectrometer scans a 2000 m/z range to identify the analytes from their molecular weights. The analyses of tryptic digests of ovalbumin and serum albumin are each described.

Determination of a new antifungal agent, voriconazole, by multidimensional high-performance liquid chromatography with direct plasma injection onto a size-exclusion column

A fully automated method has been developed for the analysis of a new antifungal agent, voriconazole, in human plasma. Multidimensional chromatography was used with size-exclusion chromatography as the first step to separate plasma protein from the drug and internal standard which were then trapped on a precolumn of pellicular ODS. A reversed-phase column, Spherisorb ODS2, then separated drug and internal standard from one another and from remaining plasma components. With an injection of 0.56 ml plasma the limit of quantitation of the method was 5 ng/ml.