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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D – 03 Reapp. Die bond process intro A number in parentheses indicates the year of last reapproval. A superscript epsilon E indicates an editorial change since the last revision or reapproval. This test method may be abbreviated for the analysis of lean natural gases containing negligible amounts of hexanes and higher hydrocarbons, or for the determination of one or more components, as required.
The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 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. Summary of Test Method aztm. The composition of the sample is calculated by comparing either the peak heights, or the peak areas, or both, with the corresponding values obtained with the reference standard.
Significance and Use 4. The thermal conductivity detector must be sufficiently sensitive to produce a signal of at least 0. Although a strip-chart recorder is not required when using electronic integration, it is highly desirable for evaluation of instrument performance. The width of the chart shall be not less than mm.
Current edition approved Jan. Originally approved in Last prewous edition approved in as The oven temperature shall not exceed the recommended temperature limit for the materials in the column.
The detector temperature shall be equal to or greater than the maximum column temperature. The purity of the carrier gas may be improved by flowing the carrier gas through selective filters prior to its entry into the chromatograph.
The preferred material of construction x1945-03 stainless steel. Copper and copper-bearing alloys are unacceptable. Baseline tracking with tangent skim peak detection is recommended. The attenuator must be accurate to within 0. Copper, adtm, and other copper-bearing alloys are unacceptable. The fixed loop or section shall be so constructed that the total volume, including dead space, shall not normally exceed 0.
I f increased accuracy of the hexanes and heavier portions of the analysis is required, a larger sample size may be used see Test Method D A flowing sample inlet system is acceptable as long as viscosity effects are accounted for. NOTE 1 — T h e sample size limitation of 0.
Larger samples may be used to determine low-quantity components to increase measurement accuracy. A 5A column can be used if a pre-cut column is present to remove interfering hydrocarbons. If a recorder is used, the recorder pen must return to the baseline between each successive peak. The resolution R must be 1. Separation of carbon dioxide must be sufficient so that a 0.
The wstm should be completed within 40 min, including reversal of flow after n-pentane to yield a group response for hexanes and heavier components. In asstm apphcations, it is preferred to use front-end d1945-0 of the heavy ends. The operating conditions, including columns, are also typical and are subject to optimization by competent personnel.
The drier must remove moisture without removing selective components to be determined in the analysis. 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. The well type inherendy offers better precision and is preferred when calibrating w i t h pure components. Samples w i t h up to one atmosphere o f pressure can be entered.
W i t h either type manometer the m m scale can be read more accurately than the inch scale. Avoid contact with the skin as much as possible. Wash thoroughly after contact. Preparation of Apparatus 6. A smaller loop size should replace the fixed volume loop and 6. It is useful to construct a table noting the response factor deviation in changing concentration. See Table 2 and Table 3. Other natoral gas components do exhibit a significant compressibility at pressures less than atmospheric.
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. Procedure for Linearity Check: Evacuate the sample-entry system and observe the manometer for leaks. The sample-entry system must be awtm tight. Record the peak area of die pure component. Chromatographs are not truly linear over wide concentration ranges and linearity should be established over the range of wstm.
They must contain known percents of the components, except oxygen Note 5that are to be determined in the unknown sample. All components in the reference standard must be d194-03 in the vapor state at the time of use.
ASTM D – 03 Standard Test Method for Analysis of Natural Gas by Gas Chromatography
The concentration of a component in the reference standard gas should not be less than one half nor more than twice the concentration of the corresponding component in the test gas. Copper, vinyl, or rubber connections adtm not acceptable. Heated lines may be necessary for high hydrocarbon content samples. This small sample size is necessary to obtain a linear detector response for methane. SuiBcient accuracy can be obtained for the determination of all but the minor constituents by the use of this sample size.
Avoid introduction of liquids into the sample system. The amount of purging required must be awtm and verified for each instrument. The satnple loop pressure should be near atmospheric. Close the cylinder valve and allow the pressure of the sample in the loop or tube to stabilize. Then immediately inject the contents of the loop or mbe into the chromatographic asym to avoid infiltration of contaminants.
Warning—Some components, such as carbon dioxide, hydrogen sulfide, and hexanes and higher hydrocarbons, may be partially or completely removed by the water.
Close the valve to the vacuum source and carefully meter the fuel-gas sample from the sample f1945-03 until the sample loop is filled to the desired pressure, as indicated on the manometer see Fig.
Inject the sample into the chromatograph. Select a sample size in accordance with 8. Enter the sample, and backflush heavy components when appropriate.
Obtain a corresponding response on the reference standard. The sample size must not exceed 0. Enter the sample and obtain a response through methane Note 5. Likewise, obtain a response on the reference standard for nitrogen and methane. Obtain a response on dry air for nitrogen and oxygen, i f desired. The air must be either entered at an accurately measured reduced pressure, or from a helium-diluted mixture.
Diluted dry air is a suitable standard for oxygen and nitrogen see 8. Adjust the operating conditions and allow the chromatograph to stabilize. NOTE 6—Most modem chromatographs have valve ovens that can be temperature controlled.
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. Either the average of the two consecutive checks, or the latest check agreeing within the repeatability limits of the previous check on each component may be used as the reference standard for all subsequent runs until there is a change in instrument operating conditions.
Daily calibrations are recommended. The higher the temperature the shorter the equilibration time approximately 2 h for small sample containers of mL or less. This analysis method assumes field sampling methods have removed entrained liquids.
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.
40 CFR 600.011 – Incorporation by reference.
This pressure need not be measured precisely, as the concentration of nitrogen in the mixture thus prepared must be determined by comparison to nitrogen in the reference standard. The d1945–03 nitrogen is multiplied by 0.
Do not rely on oxygen standards that have been prepared for more than a few days. It is permissible to use a response factor for oxygen that is relative to a stable constituent. Enter a 1- to 5-mL sample and d1945–03 the response for helium, followed by hydrogen, which will be just ahead of oxygen Note 5. Obtain a corresponding response on a reference standard containing suitable concentrations of helium and hydrogen see Fig. The expressed numerical value of any component in the sample should not be presumed to be more accurate than the corresponding certified value of that component in the calibration standard.
A more accurate value for the molecular weight of Cand heavier can be d1945-003 as described in Annex A1. The measured area should be corrected by using the average molecular weights of the entire reverse-flow aetm for the value of A. The sum of the original values should not differ from Also measure the areas of both pentane peaks on the sample chromatogram, and adjust all measured areas to the same attenuation basis.
Enter a 1- to 5-mL sample into the column and reverse the carrier gas flow after n-pentane is separated. Obtain a corresponding chromatogram on the reference standard, which can be accomplished in about 5-min run time, as there is no need to reverse the flow on d19445-03 reference standard.