【国外标准】 Standard Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography (Withdrawn 2016)

The determination of hydrocarbon impurities contained in toluene and mixed xylenes used as chemical intermediates and solvents is typically required. This test is suitable for setting specifications and for use as an internal quality control tool where aromatic monocyclic hydrocarbons are produced or are used. This test method is applicable for determining the impurities from the aromatic hydrocarbon production process. Typical impurities are alkanes containing 1 to 10 carbon atoms, benzene, toluene, ethylbenzene (EB), xylenes, and aromatic hydrocarbons containing nine carbon atoms. Refer to Test Methods D3797, D4492, and D7504 for determining the purity of o-Xylene, p-Xylene, and benzene. Refer to Test Method D6563 or D7504 for determining the C8 aromatic hydrocarbon distribution in mixed xylenes. Purity is commonly reported by subtracting the determined expected impurities from 100.00. However, a gas chromatographic analysis cannot determine absolute purity if unknown or undetected components are contained within the material being examined. TABLE 1 Instrumental Parameters DetectorFlame ionization Column: Tubingfused silica Stationary phasecrosslinked polyethylene glycolA Film thickness, μ0.25 Length, m60 Diameter, mm0.32 ID Temperatures: Injector, °C270 Detector, °C300 Oven: Initial, °C60 Time 1, min10 Final, °C150 Rate, °C/min5 Time 2, min10 Carrier gashelium Flow rate, mL/min1.0 Split ratio100:1 Sample size, μL1.0 Analysis time, min38 Linear velocity at 145°C, cm/s20 A Polyethylene glycol such as Carbowax 20 M available from most chromatographic suppliers, has been found suitable for this purpose.1.1 This test method covers the determination of the total nonaromatic hydrocarbons, and trace monocyclic aromatic hydrocarbons in the purity of toluene and mixed xylenes by gas chromatography. 1.2 Nonaromatic aliphatic hydrocarbons containing 1 through 10 carbon atoms (methane through decanes) can be detected by this test method at concentrations ranging from 0.001 % to 2.500 weight %. 1.2.1 A small amount of benzene in mixed xylenes may not be distinguished from the nonaromatics and the concentrations are determined as a composite. 1.3 Monocyclic aromatic hydrocarbon impurities containing 6 through 9 carbon atoms (benzene through C9 aromatics) can be detected by this test method at individual concentrations ranging from 0.001 % to 1.000 weight %. 1.4 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off in accordance with the rounding-off method of Practice E29. 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. For specific hazard statement, see Section 9.