RETENTION IN MULTISTEP PROGRAMMED-TEMPERATURE GAS-CHROMATOGRAPHY AND FLOW-CONTROL - LINEAR HEAD PRESSURE PROGRAMS

A comparative study of retention in different systems of flow control that provide linear dependence with the temperature of the column's he ad pressure is performed by numerical simulation considering multistep (or multiramp) PTGC (programmed-temperature gas chromatography) as th e most general situation. Calculation algorithms for each flow control mode are developed on the basis of a general retention equation and t he only additional hypothesis is that certain geometric parameters of the column remain practically constant along the program. Procedures a re individually contrasted with experiment, prior to application. The comparative view indicates that simple correlations cannot be obtained between retention times and temperatures in two different pressure co ntrols or pressure programs. It seems that numerical procedures are un avoidable when it is required to convert the retention data from one c hromatographic system to another with the same stationary phase.