Biomedical subjects

L Van Heukelem

Publications and source records attributed to L Van Heukelem.

4 recordsLinked to original sources

PubMed2001

Computer-assisted high-performance liquid chromatography method development with applications to the isolation and analysis of phytoplankton pigments.

We used chromatography modeling software to assist in HPLC method development, with the goal of enhancing separations through the exclusive use of gradient time and column temperature. We surveyed nine stationary phases for their utility in pigment purification and natural sample analysis. For purification, a complex algal matrix was separated on an efficient monomeric column, from which partially purified fractions were collected and purified on polymeric columns that exaggerated resolution between pigments of interest. Additionally, we feature an HPLC method that is simple, fast, demonstrates excellent transferability and is ideal for quantitative analysis of pigments in dilute natural water samples.

Chromatography, High Pressure Liquid↗

PubMed2000

Selectivity differences for C18 and C8 reversed-phase columns as a function of temperature and gradient steepness. I. Optimizing selectivity and resolution.

Four experimental runs where temperature T and gradient time tG are varied allow the computer-prediction of reversed-phase liquid chromatographic (RPLC) separation for different combinations of temperature and gradient time. This in turn can provide significant changes in selectivity and a resulting optimization of separation. If this procedure is repeated for different columns, additional control over selectivity and resolution becomes possible. The simultaneous variation of T and tG for columns from different sources was studied for two samples, as a means of evaluating the general advantage of this approach for RPLC method development. Changes in relative retention with T were found to be approximately constant for different values of tG and for different RPLC columns; similarly, changes in relative retention with tG were roughly independent of changes in temperature or the column. The latter relationships can be useful in matching ("tracking") peaks between runs during method development based on the present approach, as well as for other applications discussed in here and in Part II.

Chromatography, Liquid↗

PubMed1998

Simultaneous variation of temperature and gradient steepness for reversed-phase high-performance liquid chromatography method development. I. Application to 14 different samples using computer simulation.

The optimized reversed-phase HPLC separation of 14 different samples is reported, based on simultaneous changes in temperature and gradient steepness. Four experimental runs are required for each sample, following which preferred conditions can be predicted using computer simulation software (DryLab). The overall accuracy and effectiveness of this method development approach is discussed, with particular attention to the use of resolution maps provided by the software. These maps are useful for maximizing resolution for the total sample, for optimizing the separation of a smaller number of selected sample compounds, and as an initial step in the separation of more demanding samples.

Adrenal Cortex Hormones↗

PubMed1998

Simultaneous variation of temperature and gradient steepness for reversed-phase high-performance liquid chromatography method development. II. The use of further changes in conditions.

The preceding paper (Part I) suggests that simply optimizing temperature and gradient steepness will often provide an adequate reversed-phase HPLC separation. In some cases, however, this procedure will prove unsuccessful, and then further method-development experiments (involving change in other separation conditions) will be required. One strategy is to change a variable other than temperature or gradient steepness, followed by re-optimization of the latter two variables. The present paper examines the application of this approach with the aid of computer simulation to several samples.

Acetonitriles↗