In a gas chromatograph system having a column with a stationary phase and a carrier gas moving through the column to contact the stationary phase, the system being useful for detecting analytes in a sample, a method and apparatus for predicting the retention times for the analytes under various conditions, the method utilizing the steps of: a) detecting the analytes under a number of sets of given conditions; b) calculating values for various parameters characteristic of the system based on a mathematical model that includes a correction to compensate for the permeability of said column to said carrier gas; c) entering into the model the values for the characteristic parameters and at least one further set of conditions; and d) using the model to predict retention times for conditions other than those of step a; the apparatus composed of a data handling system including a model for predicting retention times at a variety of conditions of operation of the system, the model having a first set of inputs including retention times determined during a number of operating condition sets; and a second input representative of the permeability of the column to the carrier gas, the data handling system possessing a prediction mechanism for putting into the model a set of conditions other than those of a) above and for putting in the set of parameters, and for predicting retention times for those conditions other than those of a).
