5.1 ASTM standard gas chromatographic methods for the analysis of petroleum products require calibration of the gas chromatographic system by preparation and analysis of specified reference mixtures. Frequently, minimal information is given in these methods on the practice of calculating calibration or response factors. Test Methods D2268, D2427, D2804, D2998, D3329, D3362, D3465, D3545, and D3695 are examples. The present practice helps to fill this void by providing a detailed reference procedure for calculating response factors, as exemplified by analysis of a standard blend of C₆ to C₁₁ n-paraffins using n-C₁₂ as the diluent.

5.2 In practice, response factors are used to correct peak areas to a common base prior to final calculation of the sample composition. The response factors calculated in this practice are "multipliers" and prior to final calculation of the results the area obtained for each compound in the sample should be multiplied by the response factor determined for that compound.

5.3 It has been determined that values for response factors will vary with individual installations. This may be caused by variations in instrument design, columns, and experimental techniques. It is necessary that chromatographs be individually calibrated to obtain the most accurate data.