LCGC Europe-01-01-2016

Ultrahigh-pressure size-exclusion chromatography (UHPSEC) can potentially offer a new direction and overcome some of the disadvantages (for example, limited resolution and long analysis time) associated with conventional SEC analysis. UHPSEC is based on using sub-3-µm silica-organic hybrid particles under elevated pressures (often above 400 bar) to improve the separation efficiency and increase analysis speed. In spite of the benefits promised by the chromatographic theory, there are some uncertainties that may limit the proliferation of UHPSEC in polymer analysis. As a result of possible issues associated with the use of a different stationary phase - including secondary interactions and polymer degradation - it is unclear whether UHPSEC will provide results comparable to those of traditional SEC methods. In this article, the advantages and challenges of UHPSEC for the analysis of different engineering thermoplastics are discussed, as well as a comparison of results obtained with UHPSEC and conventional SEC.

A glimpse of what’s on offer for chromatographers at Pittcon 2016, which will be held from 6–10 March 2016 at the Georgia World Congress Center in Atlanta, Georgia, USA.

This is the third “LC Troubleshooting” column in a series related to problems that we associate with liquid chromatography (LC) columns. This month is the first of several discussions looking at problems that are caused by chemical problems with the column.

Mark Schure spoke to LCGC Europe’s Lifetime Achievement Award winner, Hernan Cortes, about his career with Dow Chemical, multidimensional chromatography, the evolution of mass spectrometry (MS), and the direction that liquid chromatography (LC) is taking.

Thermal desorption sampling often provides a means for bringing otherwise intractable samples to a gas chromatography (GC) column for separation and detection. In this instalment, John Hinshaw describes the principles of thermal desorption sampling in relationship to other analysis techniques for volatile solutes.

Cloud-point extraction (CPE) manipulates temperature and surfactant concentration to move aqueous solutes into a micelle phase for separation. Although CPE has been around for some time, it is still considered an emerging technique. Much of the development, and most applications, of CPE have dealt with extraction and preconcentration of inorganic solutes. More recently, attention has turned to the use of CPE in the isolation of organic solutes. This month, we review how CPE works and focus on applications for extracting organics.

The selectivity of different combinations of organic modifiers, pH, and types of reversed-phase liquid chromatography (LC) materials has been characterized using Tanaka column characterization, linear solvent energy relationships (LSER), and selectivity correlations. The three characterization techniques highlighted the potential complementary selectivity of these phases and conditions as well as the type and dominancy of some of the retention mechanisms involved. Subsequently, selectivity differences were proven to be valid in the practical separation of acids, bases, and neutral analytes. This paper aims to assist chromatographers in producing highly efficiency method development strategies for reversed-phase LC separations in a relatively short time frame.

Click the title above to open the LCGC Europe January 2016 regular issue, Vol 29, No 1, in an interactive PDF format.