ASTM D6730 Test Method for Individual Components in Spark Ignition Engine Fuels
ASTM D6730 Standard Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 100-Metre Capillary (with Precolumn) High-Resolution Gas Chromatography
13. Calibration
13.1 Qualitative - Determine the retention times of components by analyzing known reference mixtures or samples under identical conditions. Calculate retention indices from these data using 12.2. Table A1.1 provides a listing of typical values for this test method.
13.2 Quantitative, Hydrocarbons - Use theoretical response factors for correction of the detector response of hydrocarbons determined by this test method, unless response factors have been determined experimentally. The response of an FID to hydrocarbons is determined by the ratio of the molecular weight of the carbon in the analyte to the total molecular weight of the analyte. If experimentally determined response factors are to be used, they must be determined using known purity individual standards and calculated using Practice D4626. The response factors, as listed in Table 3, are relative to that calculated for heptane. Calculations are based on the following equation:
Fi = ((((Caw x Cn) + (Haw x Hn))/Cn) x 0.83905)/Caw)
where:
Fi = relative response factor for a hydrocarbon type group of a particular carbon number.
Caw = atomic weight of carbon 12.011,
Cn = number of carbon molecules in the group,
Haw = atomic weight of hydrogen, 1.008,
Hn = number of hydrogen molecules in the group, 0.83905 is the correction factor with heptane as unity (1.0000), and 0.7487 is used with methane as unity.
13.3 Quantitative, Oxygenates - Determine response factors for methanol, ethanol, and other oxygenated compounds experimentally. The principles in Practice D4626 should be applied when determining these response factors. The response of the flame ionization detector for oxygenated compounds is not directly (theoretically) related to mass concentration. A study has indicated that the FID response is linear for the conditions of this test method (see Figs. 10 and 11). Each individual apparatus must be calibrated using gravimetrically prepared standards, covering the sample concentration ranges expected and the scope of this test method. Standards used must comply with the requirements in Section 7. Figs. 10 and 11 present calibration data for six oxygenates as determined in a preliminary cooperative study report for calibration of this test method. Precision data will be prepared when more data becomes available.
