What’s that smell? – A tale of 2 dimensions
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: firstname.lastname@example.org.