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What’s that smell? – A tale of 2 dimensions

Anna Perkins

29th January 2015

1D/2D-GC/MS, 1D2D, GC/Q-TOF, Kathy Ridgway, NPD, ODP, Smell,


 

The human nose can be the most sensitive detector

The human nose can be the most sensitive detector, but the art of picking out individual odours from a mixture can be a challenge – in particular if those compounds are not chromatographically resolved.

Once upon a time, chromatographic resolution was key – the art of getting the column and temperature program just right, in order to separate all the peaks in a sample has been covered in many a training course.  For GC-MS methods however, with software that is able to do mass spectral deconvolution, you could argue whether this is still as important.

I recently discovered, using the 1D2D system, the power of chromatographic resolution and why for certain applications, good separation can still be critical in data interpretation.  The patented GERSTEL Selectable 1D/2D-GC/MS System can run analysis just through one column (1D mode), but also enables sections of the chromatogram to be cut and separated on a second dimension column (2D), using so called ‘heart cutting’.  As the system is based on a single standard GC/MS system, data are obtained in one chromatogram.

Consider the scenario, you have a complex flavour mix, which is being assessed not only using a mass spectrometer, but also by human assessors via an olfactory (sniffer) port.  There is a particular region of interest from a sensory point of view, but separation of the components on one column is proving difficult.  What if you could cut this region and separate the individual components, without a significant increase in the overall GC run time and still obtain a normal chromatogram for the other compounds in your mixture?  Wouldn’t sensory assessment of the separated compounds be easier once there is a clear distinction between the peaks?  The art of GC-O analysis can be tricky – particulary for closely eluting peaks, but by combining with the 1D2D system, characterisation of components can be more easily achieved, and odour active compounds more easily identified.

A recent paper highlighted the power of this technique further, by the use of an element specific detector and Q-TOF MS for unequivocal identification of compounds.  A link to the full text of this paper can be found here.  I am busy writing an application note on some work performed in our Cambridge laboratory with 1D2D, using a selective nitrogen detector (NPD), ODP and Mass Spectrometer.  If you would like to receive a copy once it is complete, please email: enquiries@anatune.co.uk.