Tech Tip: Miniaturisation in GC laboratories – Part IV

Method miniaturisation is the squeezing of as many instrumental and analytical parameters as possible to optimise efficiency. Variables that can be examined include extraction solvent, extraction technique, injection onto the column, separation on column, quantification via the detector and finally the cycle time of one analytical run. As we strive to make the method more robust we should improve quality, obtain an equivalent if not better Limit of Detection (LOD) and deliver the result more quickly and hence more cheaply.

Separation on column

Why change the column dimensions or carrier gas?

By using a shorter, narrower column, with a thinner film and increasing gas flows and oven temperature ramp rates, it is possible to shorten run times considerably with little or no loss in resolution or signal-to-noise ratio. Method translation software has been developed [1] and is freely available to assist analysts.

Diagram 1: Moving to a shorter column but keeping phase ratio the same reduces run time but preserves selectivity

Further possible improvements include using more efficient carrier gases like hydrogen, which compared to helium has a larger linear velocity. Whilst hydrogen is known to be reactive to certain compounds, using a PTV inlet with cool injection reduces the likelihood of artefact production, leaving the major gains of improved efficiency, better signal to noise ratios and further reduced run times.

Diagram 2: Utilising further variables gives even more productivity gains

 

Acknowledgements:

Restek

Agilent

References:

[1] Available from the Agilent website - GC method translation software , Windows 7 compatible - last update 20/03/2015