ASTM D7504-09

Determining the type and amount of hydrocarbon impurities remaining from the manufacture of toluene, mixed xylenes, and p-xylene used as chemical intermediates and solvents is often required. This test method is suitable for setting specifications and for use as an internal quality control tool where these products are produced or are used. Typical impurities are: alkanes containing 1 to 10 carbons atoms, benzene, toluene, ethylbenzene (EB), xylenes, and aromatic hydrocarbons containing nine carbon atoms.

This method may not detect all components and there may be unknown components that would be assigned inappropriate response factors and thus, the results may not be absolute.

1.1 This test method covers the determination of the total nonaromatic hydrocarbons and trace monocyclic aromatic hydrocarbons in toluene, mixed xylenes, and p-xylene by gas chromatography. The purity of toluene, mixed xylenes, or p-xylene can also be calculated. Similar test methods, using the internal standard calibration technique and the external standard calibration technique, are Test Method D 2360 and D 5917 respectively.

1.2 Total aliphatic hydrocarbons containing 1 through 10 carbon atoms (methane through decanes) can be detected by this test method at concentrations ranging from 0.0001 to 2.5000 weight %. The limit of detection is 0.00003 weight % and the limit of quantitation is 0.0001 weight %.

1.2.1 A small amount of benzene in mixed xylenes or p-xylene may not be distinguished from the non-aromatics and the concentrations are determined as a composite (see 6.1).

1.3 Monocyclic aromatic hydrocarbon impurities containing 6 through 10 carbon atoms (benzene through C₁₀ aromatics) can be detected by this test method at individual concentrations ranging from 0.0001 to 1.0000 weight %.

1.4 The following applies to all specified limits in this test method: for purposes of determining conformance with this test method, an observed value or a calculated value shall be rounded off “to the nearest unit” in the last right-hand digit used in expressing the specification limit, in accordance with the rounding-off method of Practice E 29.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.