ASTM D7041-16(R2021) pdf free download

ASTM D7041-16(R2021) pdf free download.Standard Test Method for Determination of Total Sulfur in Liquid Hydrocarbons and Hydrocarbon-Oxygenate Blends by Gas Chromatography with Flame Photometric Detection
3. Summary of Test Method
3.1 The sample is analyzed by gas chromatography with a flame photometric detector. A fixed amount of sample is injected into the gas chromatograph where it is vaporized. The air carrier stream carries the vaporized sample into a high temperature zone (>900 °C) where the compounds present in the sample are oxidized. Sulfur compounds are converted to sulfur dioxide (SO 2 ). The carrier stream carries the oxidation components onto a chromatographic column where they are separated and the SO 2 is quantified by the flame photometric detector. Calibration ofthe detector is achieved by the use ofan appropriate external standard.
4. Significance and Use
4.1 This test method can be used to determine total sulfur levels in process feeds and finished products that fall within the scope of this test method. 4.2 Low levels of sulfur in process feed stocks can poison expensive catalysts used in petroleum refining processes. This test method can be used to monitor sulfur levels in these feedstocks.
5. Apparatus
5.1 Gas Chromatograph, equipped with automatically con- trolled valves, capable of automatic calibration with an exter- nal standard and having a flame photometric detector with an overall sensitivity to detect at least 0.5 mg/kg of SO 2 . It must be able to automatically control all valve switching times. Although originally developed with online analytical measure- ment equipment in an offline mode ofoperation, suitable online or laboratory gas chromatographs may apply this test method as described. Typical instrument parameters are listed in Table 1. 5.1.1 Carrier and Detector Gas Control—The chromato- graph must be equipped with flow controllers or pressure controllers capable of maintaining a constant supply of carrier gas and detector supply gases. Electronic pressure or flow control is highly recommended. 5.1.2 Sample Injection System—An automatic sample injec- tion device is required. The injector must allow the introduc- tion ofsmall sample sizes (0.1 µL to 1 µL). The sample must be accurately and repeatably injected into the gas chromatograph. Rotary or stem type liquid injection valves or auto injectors are recommended. The valve or injector must be equipped with a heated vaporizer section capable of being heated to at least 285 °C. 5.2 Pyrolysis Furnace—A furnace capable of maintaining a sufficient temperature (>900 °C) to pyrolyze the entire sample and oxidize the sulfur compounds to SO 2 . 5.3 Quartz Combustion Tube—Quartz tube capable of with- standing temperatures up to 1200 °C. The oxidation section shall be large enough to ensure complete oxidation of the sample. 5.4 Column—A column that can provide complete separa- tion of SO 2 from the CO 2 quench and the other oxidized components such as H 2 O. 5.5 Detector—Any flame photometric detector (FPD) can be used, provided it can detect a minimum peak height twice that of the baseline noise for a 1 µL injection of a 0.5 mg ⁄kg S standard. Detector linearity shall be at least equal to or greater than 10 3 . The user is referred to Practice E840 for assistance in optimizing the operation and performance of the FPD.
6. Reagents and Materials
6.1 Purity of Reagents—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 Commit- tee on Analytical Reagents of the American Chemical Society, where such specifications are available. 3 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination. 6.2 Carrier-Gas—Zero grade air is recommended. (Warning—Compressed air is a gas under high pressure that supports combustion.) 6.3 Hydrogen—Chromatographic grade recommended, minimum purity 99.995 %. (Warning—Hydrogen is an ex- tremely flammable gas under high pressure.) 6.4 Solvent (Reagent Grade)—The solvent chosen should be capable of dissolving the sulfur-containing compound used to prepare the standard. The solvent of choice should have a density similar to the samples being analyzed and it should have sulfur concentrations less than the instrument detection limit. Mixed solvents such as an isooctane / toluene mixture can be used to reach the desired density. (Warning—Solvents used as reagents such as toluene and isooctane are flammable and may be harmful or fatal if ingested or inhaled.)