Methods of Testing Petroleum and Associated Products Standard Test Method for the Identification of Hydrocarbon Components in Automotive Gasoline Using Gas Chromatography
1. SCOPE 1.1 This test method is a standard procedure for the determination of
paraffins, olefins, naphthenes, aromatics and unknowns (P.O.N.A.U.) in
automotive gasolines using gas chromatography. 1.2 The final boiling point of samples should not exceed that of nC15. 1.3 Individual hydrocarbon components or groups of coeluting components
greater than or equal to 0.01% by mass are determined. 1.4 The separation of individual hydrocarbons by the procedure described in
this test method is not absolute and will result in some peaks that represent
coeluting compounds (Table1). 1.5 A limitation of the method is that toluene and 2,3,3-trimethylpentane
may coelute. if isooctane (2,2,4-trimethylpentane) and 2,3,4-trimethylpentane
are present in the gasoline sample, it is probable that the sample contains,
2,3,3-trimethylpentane. The concentration of 2,3,3-trimethylpentane is almost
certain to be less than the concentration of 2,3,4-trimethylpentane. When
determining the concentration of toluene and 2,3,3-trimethylpentane, it is
essential that the gas chromatographic integrator has individual peak
processing capabilities including peak expansion and perpendicular drop. To
detect 2,3,3-trimethylpentane and toluene, these compounds must be within a 5:1
ratio of each other with either compound having the greater concentration. If
these components are present in a greater than 5:1 ratio, the toluene and
2,3,3-trimethylpentane may appear as a coeluted peak, thus causing the
component in the smallest concentration to be integrated with the more
concentrated component. 1.6 The data obtained from analyzing three hundred and sixty-nine Canadian
automotive gasolines were used to develop this test method. These data,
excluding toluene and 2,3,3-trimethylpentane, did not indicate the presence of
coeluting peaks, which would have a significant influence on the final
interpretation of the information. 1.7 From the gasolines analyzed, forty compounds with concentrations
greater than 1% by mass have been found. These possible forty compounds
constitute an average of 79% by mass of automotive gasoline. From these forty
compounds which may be found in gasoline, this method identifies coeluting
peaks for toluene, 2-methylhexane, methylcyclopentane and n-hexane (Table 1).
The forty compounds are identified in Table 5 by an asterisk beside its
identification number. 1.8 The number of coeluting peaks depends on the total number of individual
compounds and the number of olefinic compounds present. The possibility of
coeluting compounds increases with the increase of compounds detected after
n-octane. 1.9 Oxygenated compounds may be determined by this test method. To analyze
for oxygenated compounds, insert oxygenated compounds of interest (Table 2) in
the hydrocarbon data table (Table 5). Due to the possibility of coeluting
peaks in other areas, the user is cautioned in the interpretation of the data. 1.10 The testing and evaluation of a product against this method may require
the use of materials and/or equipment that could be hazardous. This document
does not purport to address all the safety aspects associated with its use.
Anyone using this method has the responsibility to consult the appropriate
authorities and to establish appropriate health and safety practices in
conjunction with any applicable regulatory requirements prior to its use.