The quality of packed columns is frequently expressed in terms of number of theoretical plates/m packed bed (N/m) and asymmetry factor (As).
Experimentally, both values are easily determined in an efficiency test, by applying a tracer (sample) such as acetone. The calculated theoretical plates/m varies depending on the test conditions and should therefore be regarded as a reference value. To achieve comparable results, conditions and equipment should be kept as constant as possible since changes in buffers, sample volume, liquid velocities, liquid pathway, temperature, etc. will influence the result.