May 14th 2024
Scientists from the Shenyang Pharmaceutical University in China have developed a new quality assessment system for various types of traditional Chinese medicine (TCM).
The UV Detector for HPLC — An Ongoing Success Story
March 1st 2005In this article, the authors look at the contemporary features of a UV detector and the design improvements that have been made over the last 30 years. Recommendations concerning technical details are also given that may influence the choice in purchase.
New Chromatography Columns and Accessories at the 2005 Pittcon Conference: Part I
March 1st 2005Pittcon 2005 - the 56th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy - returned to the Orange County Convention Center, Orlando, Florida, 27 February-4 March 2005. This year's event hosted more than 900 instrument manufacturers and 1aboratory suppliers in more than 2300 booths. In addition to attending the exposition, the conferees were able to listen to numerous oral presentations, view more than 900 posters, check out 38 seminar rooms, or attend one of 150 short courses.
Planar Chromatography Versus Column Chromatography: A Performance Comparison
March 1st 2005It is hypothesized that in particular cases, conventional planar chromatography provides a more effective and robust system than column chromatography with regard to separation efficiency and peak distribution of mixtures composed of low-retarded analytes. Under similar reversed-phase experimental conditions, a regular distribution of thin-layer chromatography (TLC) spots of four natural estrogens (estetrol, estriol, 17?-estradiol, and estrone) corresponds to strong irregular dispersion of peaks in chromatograms generated by high performance liquid chromatography. In both cases, the efficiency of separation was assessed using simple optimization criteria such as selectivity (?min) and resolution (Rs min). The distribution of chromatographic spots was evaluated using the relative resolution product (r). The results revealed that an excellent separation of the components of interest could be achieved easily using simple nonforced and isocratic TLC. Such an interesting property of planar chromatography is mainly driven by the nonlinear relationship between k and Rf retention factors. This article also reports the practical advantages of TLC for the separation of estrogenic steroid mixtures at different temperatures.
Chromatography Applications in Drug Discovery of Therapeutic Proteins
March 1st 2005In this month's installment of "Directions in Discovery," the authors discuss how, with the arrival of combinatorial libraries and high-throughput screening, pharmaceutical firms can develop new models of drug discovery that not only lessen the initial capital outlay involved in drug discovery, but also refine the discovery process.
HPLC Analysis of Nonvolatile Analytes Using Charged Aerosol Detection
A new detection method based upon aerosol charging was examined for its applicability and performance with high performance liquid chromatography (HPLC). Our results demonstrate universal detection of nonvolatile analytes with response magnitude that is independent of analyte chemical properties, four orders of magnitude dynamic range, low nanogram, lower limits of detection, and < 2% relative standard deviation response variability. Broad applicability was demonstrated for a range of methods including those using gradient elution, reversed phase, hydrophilic interaction, and ion chromatography; normal and narrow bore column formats; and in combination with other detectors (for example, UV detectors, evaporative light-scattering detectors, and mass spectrometers).
Choice of Buffer for the Analysis of Basic Peptides in Reversed-Phase HPLC
February 1st 2005Formic acid often is used for the analysis of peptides in proteomic studies by HPLC-MS, due to its volatility and reduced signal suppression. However, poorer chromatographic performance can be obtained in comparison with trifluoroacetic acid or nonvolatile phosphate buffers due to increased overloading, which can occur even for extremely small sample masses. Comparison of a highly inert silica-ODS and a wholly polymeric phase indicated that overloading effects on both are very similar and caused by the mutual repulsion of solute ions on the hydrophobic column surface.
HPLC Analysis of Nonvolatile Analytes Using Charged Aerosol Detection
A new detection method based upon aerosol charging was examined for its applicability and performance with high performance liquid chromatography (HPLC). Our results demonstrate universal detection of nonvolatile analytes with response magnitude that is independent of analyte chemical properties, four orders of magnitude dynamic range, low nanogram, lower limits of detection, and < 2% relative standard deviation response variability. Broad applicability was demonstrated for a range of methods including those using gradient elution, reversed phase, hydrophilic interaction, and ion chromatography; normal and narrow bore column formats; and in combination with other detectors (for example, UV detectors, evaporative light-scattering detectors, and mass spectrometers).
The Misunderstood Laboratory Solvent: Reagent Water for HPLC
January 1st 2005Reagent water is used in all aspects of liquid chromatography (LC) technology, from preparation of mobile phase to preparation of standards, blanks, and samples. Reagent water is the most widely used analytical solvent, yet it is the least characterized, especially in total organic carbon (TOC) content. TOC adversely effects performance of LC methods and hence, reagent water quality is a major issue. Organics initially present in tap water will be reduced efficiently to low parts-per-billion concentrations by combining several technologies embedded in a water purification system. Monitoring the TOC concentrations gives chromatographers added confidence in their results.
Developments in Preparative-Scale Chromatography Columns and Accessories
December 1st 2004This column focuses on some of the latest developments in preparative-scale columns, bulk packing materials and column hardware designs. Silica, polymeric and other packings are discussed together with the newest monolithic columns.
Facilitated Column Ranking and Selection in Reversed-Phase Liquid Chromatographic Analysis
November 1st 2004In this article, the authors present a column ranking system to facilitate column selection in reversed-phase liquid chromatographic analysis. The system ranks columns based on their similarity to a reference column of choice and its applicability to a real pharmaceutical analysis is demonstrated.
Elevated Temperature HPLC: Principles and Applications to Small Molecules and Biomolecules
October 1st 2004In this article the authors review the use of elevated temperatures in HPLC, and provide examples covering separations of both small molecules and biomolecules. Generic issues of temperature dependence of retention and plate height are discussed, and comparisons are made between temperature gradient and solvent gradient elution. They describe how the use of elevated temperatures allow good chromatographic efficiency to be obtained at flow-rates higher than those optimal at ambient temperature, thus increasing the speed of separation.