A few years after Van Deemter, Golay proposed a modified relationship reserved to capillary columns used in gas phase chromatography. There is no A term because there is no packing in a capillary column (see paragraph 2.5.2).
Expression 1.33 leads to the minimum value for the HETP for a column of radius r, if the retention factor of the particular compound under examination is known.
The coating efficiency can then be calculated being equal to 100 times the ratio between the value found using expression 1.33 and that deduced from the efficiency H =L/N obtained from the chromatogram.
