ASTM D5501 Standard Test Method for Determination of Ethanol Content of Denatured Fuel Ethanol by Gas Chromatography
6. Apparatus
6.1 Gas Chromatograph, capable of operating at the conditions listed in Table 1. A heated flash vaporizing injector injector designed to provide a linear sample split injection (for example, 200:1) is required for proper sample introduction. Carrier gas controls shall be of adequate precision to provide reproducible column flows and split ratios in order to maintain analytical integrity. Pressure control devices and gauges shall be designed to attain the linear velocity required in the column used. A hydrogen flame ionization detector with associated gas controls and electronics, designed for optimum response with open tubular columns, is required.
6.2 Sample Introduction - Manual or automatic liquid syringe sample injection to the splitting injector is employed. Devices capable of 0.1 to 0.5 µL injections are suitable. It should be noted that inadequate splitter design, poor injection technique, and overloading the column can result in poor resolution. Avoid overloading, particularly of the ethanol peak, and eliminate this condition during analysis.
6.3 Column - This test method utilizes a fused silica open tubular column with non-polar polydimethylsilicoxane bonded (cross-linked) phase internal coating. Any column with equivalent or better chromatographic efficiency and selectivity to those described in 6.3.1 can be used.
6.3.1 Open tubular column with a non-polar polydimethylsilicoxane bonded (cross-linked) phase internal coating, either 150 m by 0.25 mm with a 1.0 µm film thickness, or 100 m by 0.25 mm with a 0.5 film thickness is required.
6.4 Electronic Data Acquisition System - Any data acquisition and integration device used for quantification of these analyses must meet or exceed these minimum requirements:
6.4.1 Capacity for at least 80 peaks/analysis,
6.4.2 Normalized percent calculation based on peak area and using response factors,
6.4.3 Identification of individual components based on retention time,
6.4.4 Noise and spike rejection capability,
6.4.5 Sampling rate for narrow (<1 s) peaks,
6.4.6 Positive and negative sloping baseline correction,
6.4.7 Peak detection sensitivity compensation for narrow and broad peaks, and
6.4.8 Non-resolved peaks separated by perpendicular drop or tangential skimming as needed.
7. Reagents and Materials
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available.
7.2 Carrier Gas, helium, with a minimum purity of 99.95 mol %. Oxygen removal systems and gas purifiers should be used. (Warning - Helium, compressed gas under high pressure.)
7.3 Detector Gases, hydrogen, air, and nitrogen. The minimum purity of the gases used should be 99.95 % for the hydrogen and nitrogen. The air should be hydrocarbon-free grade. Gas purifiers are recommended for the detector gases. (Warning - Hydrogen, extremely flammable gas under high pressure.) (Warning - Air and nitrogen, compressed gases under high pressure.)
7.4 Standards for Calibration and Identification - Standards of all components to be analyzed are required for establishing identification by retention time as well as calibration for quantitative measurements. These materials shall be of known purity and free of the other components to be analyzed.
7.4.1 Ethanol See Note 1. (Warning - Flammable and may be harmful or fatal, if ingested or inhaled.)
NOTE 1 - Two grades of ethanol are available. Only absolute ethanol 99.5 minimum percent meets the requirements of this test method.
7.4.2 Methanol (Warning - Flammable may be harmful or fatal, if ingested or inhaled.)
7.4.3 Heptane (Warning - Flammable may be harmful or fatal, if ingested or inhaled.)
