LCGC Europe-05-01-2009
Response Surface Designs Part 1 — Types and Properties
May 1st 2009Experimental designs are used in method development and robustness testing and have been discussed in an earlier article.1 An experimental design is an experimental set-up that allows the simultaneous examination of a predefined number of factors in a predefined number of experiments. Method development is often divided into a screening and an optimization step. During the first step, many factors, potentially affecting the method, are screened to determine the most important factors, which are then further optimized.1
Using Two-dimensional Liquid Chromatography to Separate Complex Mixtures of Peptides
May 1st 2009Two-dimensional liquid chromatography (2D-LC) allows analysts to deal with complex samples that either cannot be adequately separated by one-dimensional liquid chromatography (1D-LC) or require excessively long analysis times. Peptide mixtures, whose characterization is relevant in many areas (e.g., proteomics, food analysis, pharmaceutical, life sciences), are a clear example of such complexity. An overview of the most used 2D-LC modes of operation is presented and several examples of their use for the separation of peptide mixtures are described.
Separation of Ionic Analytes using Supercritical Fluid Chromatography
May 1st 2009Supercritical Fluid Chromatography (SFC) has been practiced for approximately 50 years. SFC on packed columns for both qualitative and quantitative purposes underwent a renaissance in interest at the beginning of the 1990s when limitations of capillary SFC became obvious and important progress in composition gradient techniques for mixed mobile phases was achieved. Even with these instrumental improvements, wide acceptane of the technology was not forthcoming because the perception was that highly polar analytes were not soluble in carbon dioxide and thus were not separable. It is now apparent that the use of additives dramatically extends the range of solute polarity amenable to SFC.
