Degradation in column

The use of carbon dioxide as the mobile phase also means that it is possible to carry out assays considerably below subambient temperatures. At -50°C, Gasparrini et al. used a DACH-DNB column to resolve the enantiomers of the thermally enantiolabile 2-methyl-l-(2,2-dimethylpropanoyl) naphthalene, which can undergo rotation around the CO-CAr bond [54]. Reducing the temperature resulted in negligible degradation in column performance. 

The results just described demonstrate that the resolution of GC peaks may be very sensitive to changes in retention time resulting from instability in oven temperatures. Since the number of theoretical plates is related to resolution values, significant degradation in column plate values can occur with variations in oven temperatures. When you compare the time and effort required to obtain a two-plate fractional distillation on a 2-mL mixture (see Experiment [3B] and Technique 2) with the speed and ease used to obtain a 500 plate separation on 12.5 (xL of cyclohexanol in this experiment, it is hard not to be impressed with the enormous power of this technique. 

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