Tech Tip: Miniaturisation in GC laboratories – Part VI

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.

Cycle time of one analytical run

How can we further shorten the cycle time?

The longest time delay in any GC cycle is the oven cooling down. As the typical GC oven heating process is very inefficient (fundamentally it is heating up air in an oven), improvements have been steadily introduced over history varying from the futuristic (encapsulating the capillary column in a heated metal shield thereby reducing the air volume that is required to be heated and cooled) to the less mechanically challenged (high efficiency secondary cooling fans blowing cold air through the GC oven flap at the end of the cycle). Cryogenic gases can be used to cool ovens even more quickly but are an expensive solution and demand health and safety awareness. Other developments have included thermally stable oven pillows to reduce the volume of air in the oven to secondary heating elements within ovens that accelerate the GC ramp rate. Some broad-minded laboratories have vented the heat from the GCs through chimneys that feed into ductwork and exhausted from the building courtesy of a robust fan. All GC analysts are extremely thankful in the summer for the latter technology but strangely less so in the winter. It must also be noted that modern GC kit invariably brings efficiencies of which a quicker cooldown rate is foremost. All of the above solutions have one thing in common, they shorten cycle times and therefore save money by improving delivery.

Heat extraction helping reduce cycle times