ASTM D7504-17 pdf download.Standard Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography and Effective Carbon Number.
4. Summary of Test Method
4.1 The specimen to be analyzed is injected into a gas chromatograph equipped with a flame ionization detector (FID) and a capillary column. The peak area of each component is measured and adjusted using effective carbon number (ECN) 5 correction factors. The concentration of each component is calculated based on its relative percentages of total adjusted peak area and normalized to 100.0000 %.
5. Significance and Use
5.1 Determining the type and amount of hydrocarbon im- purities remaining from the manufacture of toluene, mixed xylenes, p-xylene, o-xylene, ethylbenzene, benzene, and sty- rene 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 con- taining nine carbon atoms or more.
5.2 This method may not detect all components and there may be unknown components that would be assigned inappro- priate correction factors and thus, the results may not be absolute.
6. Interferences
6.1 The complete separation ofp-xylene from ethylbenzene, or ethylbenzene and m-xylene from p-xylene can be difficult when either ethylbenzene or p-xylene is analyzed, respectively. The separation can be considered adequate if the distance from the baseline to the valley between the two peaks is not greater than 50 % of the peak height of lower of the two peaks.
7. Apparatus
7.1 Chromatographic data system is required.
7.2 Columns—The choice of column is based on resolution requirements. Any column may be used that is capable of resolving all significant impurities from the major component. The column and conditions described in Table 1 have been used successfully and shall be used as a referee in cases of dispute.
7.3 Gas Chromatograph—Any instrument having a flame ionization detector and a splitter injector suitable for use with a fused silica capillary column may be used, provided the system has sufficient sensitivity, linearity, and range to deter- mine 0.0001 wt %, while not exceeding the full scale of either the detector or the electronic integration for the major compo- nent. It shall have a split injection system that will not discriminate over the boiling range of the samples analyzed. The system should be capable of operating at conditions given in Table 1.
7.4 Injector—The specimen must be precisely and repeat- ably injected into the gas chromatograph. An automatic sample injection devise is highly recommended.
7.5 Syringe—chromatographic, capable ofdelivering appro- priate µL volumes.
8. Reagents and Materials
8.1 Purity of Reagent—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents ofthe American Chemical Society, 6 where such specifications are available. Reagents with an establish purity greater than ACS reagent grade may be used.ASTM D7504 pdf download.