Capillary column selection guidelines

The wealth of publications dealing with RS determination by GC is so impressive that it is difficult to provide an exhaustive review. The interested reader will find plenty of information in the references quoted so far and in others recently published, mentioned below. Packed columns, wide or narrow bore columns, capillary columns, etc. have been used for RS determination. It is true to say that capillary columns and narrow bore columns are the most often mentioned techniques. Today it is almost certain that any user can find in the literature the stationary phase and the relevant conditions to resolve his RS problem, at least in terms of selectivity. By way of example, it has been shown by Brinkmann and Ebel how it was possible to screen 65 of the 69 solvents mentioned in the ICH Guideline (discussed in paragraph 16.2.4) using capillary columns filled with two stationary phases (DB 624 and Stabilwax) which basically constitute the strategy proposed by the European Pharmacopoeia. 

The most popular column diameters available for fused silica capillaries are 0.18, 0.25 narrow bore), 0.32 and 0.52 mm (magabore or wide bore). Other diameters are also available from various manufacturers. The following guidelines apply to selection of a column diameter. 

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