ASTM D3239 Method for Aromatic Types Analysis of Gas-Oil Aromatic Fractions
ASTM D3239 Standard Test Method for Aromatic Types Analysis of Gas-Oil Aromatic Fractions by High Ionizing Voltage Mass Spectrometry
8. Calibration
8.1 Calibration equations in the computer program given in Table 2 may be used directly provided the following procedures are followed:
8.1.1 Instrumental Conditions - Repeller settings are adjusted to maximize the m/e 226 ion of n-hexadecane. A magnetic field is used that will permit a scan over the mass range from 78 to 700. An ionizing voltage of 70 eV and an ionizing current in the range from 10 to 70 µA is used.
NOTE 3 - The instrument conditions and calibration equations described in this method are based on the use of a 180° magnetic-deflection type mass spectrometer (CEC Model 21-103). Satisfactory results have been obtained with some other magnetic deflection instruments. It is not known if the equations are suitable for use on all other mass spectrometer types.
8.1.2 Computer Program - The FORTRAN program given in Table 2 contains all the equations for calculating the analysis, including those for calculating monoisotopic peak heights. The program is compiled and linked to create a computer load module that is available whenever needed. When the spectrum shown in Table 3 is processed, thee results should agree with those shown in Table 4.
8.1.2.1 Data Input Format - The input format suggested in the main program may be changed to suit the needs of individual laboratories provided that true masses and peak heights are stored in the H(M) array.
8.1.2.2 FORTRAN IV Language - Changes in the program may be required for compatibility with the particular computing system to be used. These are permitted provided that the altered program gives the results shown in Table 4 with the input data of Table 3.
NOTE 4 - The program, as shown in Table 2, has run satisfactorily on IBM System 360 computers.
