Capillary gas chromatography of alkylbenzenes. I. Some problems encountered with the precision of the retention indices of alkylbenzenes

A high-precision gas chromatographic system, in combination with high-resolution stainless-steel capillary columns and three stationary phases of different polarity, was used to study the separation and retention behaviour of 47 alkyl-benzenes up to C15, including all possible isomers between C6 and C10. The precision of the relative retention data is discussed in relation to the method of time measurement, non-ideality of the carrier gas, column temperature and ageing of the column. Taking into account these factors, the inter-laboratory agreement of the retention indices for aromatic hydrocarbons determined within and between laboratories can be improved considerably. Kováts retention indices and their temperature dependence were obtained with a precision corresponding to a standard deviation of about 0.1 index unit.