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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I f all columns are chosen to operate at the same temperature, then stabilization time between changing columns will be minimized.
Connect Cylinder A to a cylinder of pure n-pentane with a metal connection of calculated length to contain approximately the amount of n-pentane to be added. Measure areas of all peaks eluted after n-pentane. Transfer the methane to the L cylinder until the pressure equalizes. Record the peak area of die pure component. Maintain all samples above the hydrocarbon dew point.
Obtain a response on dry air for nitrogen and oxygen, i f desired. The reverse flow area, and the pentanes peaks used for comparison, should be measured by the same method.
This flow should quickly r e m m to the same flow rate and the baseline level out. 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 The width of the chart shall be not less than mm. 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.
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. Methane should be in a 1-L cyHnder at MPa atm pressure. A flowing sample inlet system is acceptable as long as viscosity effects are accounted for.
Ethane can be the reference component for carbon dioxide i f it elutes i n the same sequence as carbon dioxide. 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.
I f the dew point is unknown, heat above the sampling temperature. The attenuator must be accurate to within 0. 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. This information provides quality data and a basis for calculating physical properties such as molecular weight on these fractions. Concentration of these components has been observed to occur in a number of cases because of collection of heavier components in the sample loop during purging of the system.
On high sensitivity, this baseline may drift slightiy without harm and it need not frequently be moved back to zero. The sample-entry system must be vacuum tight. A level baseline should be quickly attained in either flow direction i f the column is clean.
A superscript epsilon E indicates an editorial change since the last revision or reapproval. Current edition approved Jan. Weigh Cylinder A after each addition to obtain the weight of the component added. This procedure will remove small amounts of hydrogen sulfide while having but minimal effect on the carbon dioxide in the sample.
Open the valve on the L cylinder, then open the valve on Cyhnder B, which w i l l result in the transfer of nearly all of the contents of Cyhnder B into the L cylinder.
Moisture on the column w i l l enlarge the reverse flow peak. For instance, propane can be the reference component for the butanes and pentanes i f propane is separated on the same column c1945-03 the same sequence as the butanes and pentanes. Enter a 1- to 5-mL sample and record the response for helium, followed by hydrogen, which will be just ahead of oxygen Note 5. Convert the weight percent to mole percent. Check this average by a second group o f tracings.
In multicolumn apphcations, it is preferred to use front-end backflush of the heavy ends.
Although a strip-chart recorder is not required when using electronic integration, it is highly desirable for evaluation of instrument performance. An accumulation of oily film in the sampling system greatly aggravates this problem. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
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.
A number in parentheses indicates the year of last reapproval. Enter the sample and obtain a response through methane Note 5. Periodically, check Cg and heavier repeatability of the apparatus by making several check runs on the same sample. A value of may be used for the molecular weight of the octanes and heavier reverse-flow peak.
Daily calibrations are recommended. The sum of the original values should not differ from Then immediately inject the contents of the loop or mbe into the chromatographic column to avoid infiltration of contaminants.
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 the reference standard.
Close the valve to the vacuum source and carefully meter the fuel-gas sample from the sample cylinder until the sample loop is filled to the desired pressure, as indicated on the manometer see Fig. A l l single-peak determinations and corresponding reference runs w i l l then be made in the same carrier gas flow direction. Connect Cylinder A to the evacuated L cylinder with as short a clean, small-diameter connector as possible. It is helpful to retain a sample containing some hexanes and heavier for periodic checking.
Significance and Use 4. Mount as required to dry the sample. The relationship is independent of temperature, sample size, and carrier gas flow rate. I f the reference standard should be exposed to lower temperatures, heat at the bottom for several hours before removing a sample.
It is useful to construct a table noting the response factor deviation in changing concentration.