Robert A. Shellie | Authors


The Modulator in Comprehensive Two-Dimensional Liquid Chromatography

The interface between the two separation dimensions is a key element of any comprehensive two‑dimensional liquid chromatography (LC×LC) system. LC×LC has typically been implemented by using one or more switching valves, equipped with either sampling loops or trap column(s). Temperature manipulation is a relatively unexplored yet promising route towards non-valve-based LC×LC. The fairly recent emergence of thermal modulation has provided a less conventional method for performing LC×LC separations. This article illustrates the variety of commonly used modulators, paying specific attention to focusing modulators.

Comprehensive 2D GC–QPMS with Differential Flow Modulation

Differential flow modulation is an inexpensive way to perform GCÃ-GC separations which has been attracting growing attention recently. Differential flow modulation uses high carrier gas flow rates in the second dimension column so it is widely thought that this rules out direct coupling with mass spectrometry. However direct coupled GCÃ-GC-QPMS using differential flow modulation is reported here for the first time using an unmodified mass spectrometer comprising a dual inlet turbomolecular pump and fast scanning quadrupole mass analyser. The suitability of the approach for characterization of essential oils is demonstrated.