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Balancing speed against resolution
In gas chromatography, it is often difficult to properly resolve components completely without using a technique known as temperature programming. If the column is maintained at a low temperature for the duration of a sample run, the first peaks to elute will likely be well-spaced, but the components staying on the column longer will find themselves bound to the stationary phase for longer periods of time; this results in large band-broadening, and long run times. At higher temperatures, these components spend more time in the mobile (gas) phase, helping them elute faster and minimizing band-broadening; the faster peaks also elute faster however, pressing the peaks so close together that they may not be resolved. In temperature programming, this effect is overcome by maintaining a low temperature for a short period of time, and increasing the temperature to help force out the longer-‘sticking’ compounds. This changes the retention time compared to a isothermal run, but if the same temperature ‘ramp’ is used, the elution times will remain constant for each component. Since retention time generally cannot be used to gain any real molecular information, this situation is acceptable, and can be readily used to speed up assays while giving better-resolved peaks. The temperature program used in this experiment is shown below.