ASTM D, D, and EPA 3C are used for the analysis of permanent gases (also called fixed gases) and light hydrocarbons at the percentage level in all. (A) Hydrocarbon compounds containing between one and five atoms of carbon plus benzene using ASTM D–03 (Reapproved ) (incorporated by. American Standards Testing & Materials (ASTM). D Standard D 03 Standard Test Method for Analysis of Natural Gas by Gas. Chromatography.
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The width of the chart shall be not less than mm. The relationship is independent of temperature, sample size, and carrier gas flow rate. The separation should be completed within 40 min, including reversal of flow after n-pentane to yield a group response for hexanes and heavier components. NOTE 1 — T h e sample size limitation of 0.
SuiBcient accuracy can be obtained for the determination of all but the minor constituents by the use of this sample size. Disconnect and weigh Cylinder A to obtain the weight of n-pentane added. Check this average by a second group o f tracings. It is strongly recommended in the absence of valve ovens to mount the gas samphng valve in the chromatograph oven and operate at the column temperature.
This flow should quickly r e m m to the same flow rate and the baseline level out. Correct each peak area to the mol basis by dividing each peak area by the molecular weight of the component. I f samples containing carbon dioxide or hydrogen sulfide, or both, are to be taken, use completely dry sample cylinders, connections, and lines, as moisture w i l l selectively absorb appreciable amounts of the acid gases.
This procedure also removes carbon dioxide, and the results obtained will be on the acid-gas free basis. An accumulation of oily film in the sampling system greatly aggravates this problem. A strip-chart recorder w ith an offset zero is desirable. The attenuator must be accurate to within 0.
ASTM D – 03 Standard Test Method for Analysis of Natural Gas by Gas Chromatography
This analysis method assumes field sampling methods have removed entrained liquids. This component is present i n the daily calibration standard and linearity is assured from previous tests. The sum of the original values should not differ from The thermal conductivity detector must be sufficiently sensitive to produce a signal of at least 0.
This eliminates the need for a multicomponent standard for daily calibration.
40 CFR 600.011 – Incorporation by reference.
This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. The preferred material of construction is stainless steel. The operating conditions, including columns, are also typical and are subject to optimization by competent personnel. This gives the Relative Molar Response factor RMRi for component 0- The reference component must be present in the same instrumental sequence except HexanesH- as the referenced components.
Run a chromatogram of each component to check on its given composition. Other natoral gas components do exhibit a significant compressibility at pressures less than atmospheric. The amount of purging required must be established and verified for each instrument. Two coluimis are necessary to determine all of the components covered in this test method. The U-tube type is useful, since i t permits filling the sample loop w i t h up to two atmospheres of sample pressure, thus extending the range of all components.
I f i n doubt about the composition, check the n-pentane and isopentane values w ith pure components by the procedure prescribed in Annex A 2. Then immediately inject the contents of the loop or mbe into the chromatographic column to avoid infiltration of contaminants. Usually 1 m of 6-mm tubing packed w ith to mesh molecular sieves is adequate, i f changed w ith each cylinder o f carrier gas.
Replace the drying agent after about one half of the material has become spent. Wash thoroughly after contact. Current edition approved Jan.
Avoid introduction of liquids into the sample system. They must contain known percents of the components, except oxygen Note 5that are to be determined in the unknown sample. Samples w i t h up to one atmosphere o f pressure can be entered. Obtain a response on dry air for nitrogen and oxygen, i f desired. For these components, a mixture with nitrogen or methane can be used to establish a partial pressure that can extend the total pressure to kPa mm Hg.
Significance and Use 4. Daily calibrations are recommended. Close the n-pentane cyhnder valve and open Cylinder A valve to admit the n-pentane from the connection and then close the valve on Cylinder A. A flowing sample inlet system is acceptable as long as viscosity effects are accounted for.
Also, the richer the gas, the worse the problem. D – 03 Reapp. The purity of the carrier gas may be improved by flowing the carrier gas through selective filters prior to its entry into the chromatograph.
Copper, brass, and other copper-bearing alloys are unacceptable. If the hydrocarbon dewpoint of the sample is known to be lower than the lowest temperature to which the sample has been exposed, it is not necessary to heat the sample. Run a sample o f the mixture at kPa mm H g absolute pressure and obtain the helium peak. D145-03 not rely on oxygen standards that have been prepared for more than a few astk.