Profiling Flavours and Fragrances by Heart-cut MDGC(MS) and Comprehensive GCxGC(qMS) in One System - - Chromatography Online
Profiling Flavours and Fragrances by Heart-cut MDGC(MS) and Comprehensive GCxGC(qMS) in One System


The Column
Volume 6, Issue 7

Coelutions using one dimensional chromatography are often observed in flavour and fragrance analysis. There are several approaches to resolve these problematic regions.

What is heart-cut MDGC about? A problematic section of the chromatogram is cut and transferred into a second column, which can be mounted in a second gas chromatograph (GC). Both GCs are connected with a heated transfer line. In the first dimension a flame ionization detector (FID) is normally used as the detector that is suited to an area normalization report. However, in finding coelutions in the first dimension it is very helpful to have an identification in the first dimension as well. This was recently realized by an additional deactivated capillary that splits a part of the effluent going to the FID and leading it into the mass spectrometer of the second dimension. With this kind of analysis chiral separation is often needed frequently as only one enantiomer has some influence on the human body. The regions of interest inside the first dimensional chromatogram can then be transferred by easy heart cuts with simple mouse clicks that define the times for cutting. The retention times of the uncut peaks that elute at retention times behind the cuts remain unchanged in the MDGC-2010 system without using any pressure corrections of retention times. This can be used by the recently described Multi-Deans Switch technology.

In contrast, comprehensive GC×GC(qMS) allows a one shot separation of complex mixtures (no enantiomeric separation). While in MDGC the total peak capacity is a sum of both columns N1 (1st dim) + N2 (2nd dim) in comprehensive GC×GC it is the multiplication N1∙N2 of both. In the latter, an orthogonal set of columns is usually used [i.e., a classical unpolar (polar) column is connected to a polar (unpolar) narrow bore column of about 1 m in length]. There are several modulation technologies available that can be grouped into thermal and flow modulation. For the latter, typical peak column flows of 10–20 mL/min are used and are, therefore, not as suitable for quadrupole MS detection, particularly because the flow dilutes the sample. As a result the sensitivity is drastically reduced. In this instance, thermal modulation with quadrupole detection was used.

Click here for the full article in The Column

ADVERTISEMENT

blog comments powered by Disqus
LCGC E-mail Newsletters
Global E-newsletters subscribe here:




 

LCGC COLUMNISTS 2014

Column Watch: Ron Majors, established authority on new column technologies, keeps readers up-to-date with new sample preparation trends in all branches of chromatography and reviews developments. LATEST: Avoiding Reversed-Phase Chromatography Problems Through Informed Method Development Practices: Choosing the Stationary-Phase Chemistry


Perspectives in Modern HPLC: Michael W. Dong is a senior scientist in Small Molecule Drug Discovery at Genentech in South San Francisco, California. He is responsible for new technologies, automation, and supporting late-stage research projects in small molecule analytical chemistry and QC of small molecule pharmaceutical sciences. LATEST: Seven Common Faux Pas in Modern HPLC


MS — The Practical Art: Kate Yu brings her expertise in the field of mass spectrometry and hyphenated techniques to the pages of LCGC. In this column she examines the mass spectrometric side of coupled liquid and gas-phase systems. Troubleshooting-style articles provide readers with invaluable advice for getting the most from their mass spectrometers. LATEST: Radical Mass Spectrometry as a New Frontier for Bioanalysis


LC Troubleshooting: LC Troubleshooting sets about making HPLC methods easier to master. By covering the basics of liquid chromatography separations and instrumentation, John Dolan is able to highlight common problems and provide remedies for them. LATEST: Estimating Resolution for Marginally Separated Peaks


More LCGC Columnists>>

LCGC North America Editorial Advisory Board>>

LCGC Europe Editorial Advisory Board>>

LCGC Editorial Team Contacts>>


Source: The Column,
Click here