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By Authority OfTHE UNITED STATES OF AMERICA

Legally Binding Document

By the Authority Vested By Part 5 of the United States Code 552(a) and

Part 1 of the Code of Regulations 51 the attached document has been dulyINCORPORATED BY REFERENCE and shall be considered legally

binding upon all citizens and residents of the United States of America.

HEED THIS NOTICE: Criminal penalties may apply for noncompliance.

Official Incorporator:

THE EXECUTIVEDIRECTOROFFICE OF THE FEDERAL REGISTER

WASHINGTON, D.C.

Document Name:

CFR Section(s):

Standards Body:

e

American Society for Testing and Materials

ASTM D1945: Standard Test Method for Analysis o

Natural Gas By Gas Chromatography

40 CFR 60.45(f)(5)(i)

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~ ~ l ~ Designation: D 1945- 96Standard Test Method forAnalysis of Natural Gas by Gas Chromatography1This standard is issued under the fixed designation D 1945; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of ast revision. A number in parentheses indicates the year of ast reapproval. Asuperscript epsilon ( ) indicates an editorial change since the last revision or reapproval.

1. Scope1.1 This test method covers the deterniination of thechemical composition of natural gases and similar gaseousmixtures within the range of composition shown in Table l.This test method may be abbreviated for the analysis of leannatural gases containing.negligible amounts of hexanes andhigher hydrocarbons; .or for the determination of one ormore components, as required. 1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informa

tion only.1.3 This standard does not purport to address al! of thesafety concerns, if any, .associated with its use. It is theresponsibility ofthe userofthis standard to establish appropriate safety and health practices and determine the app!icability o} regulatory limitations prior t use.2. Referenced Documents

2.1 ASTM Standards: .D 2597 Test Method for Analysis of Demethanized Hy. droarbon Liquid Mixtures Containing Nitrogen anQ.Carbon Dioxide by Gas Chrcimatography2 . . .D 3588 Practice for Calculating Heat Value ,. Compressibility Factor, and Relative Density (Specific Gravity) of Gaseous Fuels3 . . .E 260 Practice for Packed Coluim Gas Chromatography' 4

3; Summary of Test Method3.1- Compcinents in a representative sample are physicallyseparated by gas chromatography (GC) and compared tocalibration data obtained under identical Operating conditions from a reference standard mixture of known composition. The numerous heavy-end components of a sample canbe grouped into irregular peaks by reversing the direction ofthe carrier gas through the column at such time as to group .the heavy ends either as C5 an d heavier, C6 and heavier, cir

C7 and heavier. The composltion of the sample is calculatedby comparing either the peak heights, or the peak areas, orboth, with the corresponding values obtained with thereference standard.4. Significance and Use

4.1 This test method is of significance for providing data I This test method is under the jurisdiction of ASTM C o m m i t t ~ e D-3 "Gaseous Fuels and is the direct responsibility of Subcommittee D 03.07 onAnalysis of Chemical Composition of Gaseous Fuels.Curren! edition approved Nov. 10, 1996. Published January 1997. Originallypublished as D 1945-62 T. Last previous edition D 1945-91.2 Annual Book ofASTM Standards, Vol 05.02.3 Annual Book ofASTM Standards, Vol 05.05.4 Annual Book ofASTM Standards, Vo114.02.

for calculating. physical properties of the sample, such asheating value and relative density, or for monitoring theconcentrations of one or more of the compcinents in amixture.5. Apparatus5.1 Detector-The detector shall be a thermal-conductivity type, or its equivalent in sensitivity and stability. Ththermal conductivity detector must be sufficiently sensitiveto produce a signal of at least 0.5 mV for 1 mol % n-butane;in a 0.25-mL sample.5.2 Recording Instruments-Either strip-chart recordersor electronic integrators, or both, are used to display theseparated components. Although a strip-chart recorder is no trequired when using electronic integration, i t is highlydesirable for evaluation of instrument performance. . 5.2.1 The recorder shall be a strip-chart recorder wjth afull-range scale'of 5mv or less (1 :tll;Y preferred). The widtl:lof the chart shall be no t less than 150 nim. A ma;ximum penresponse time of 2 s (1 s preferred) anda minimum chartspeed oLIO mm/minshall be required. Faster speeds up to100 mm/min are desil:able if the chromatqgram is to beinterpreted using manual mthods to obtain areas.

5.2.2 Electronic or Computing Int"egrators--erof of separation and response e q u i v a l ~ n t to that for a recorder isrequired for displays other than by, h a r t :reco:rder. Baselinetracking with t a n g ~ n t skj.rh p ~ a k " d e t e c t i o ~ is r e q o ? I n i ~ n d , e d , . ,5.3 Attenuator-Ifthe h r o m a t o g r a ~ 18 tp b e m t e r p ~ e t e dusing manual methods,an attenuator must u ~ e d With th edetector output sign.l to m a i n ~ a i n ' in.ximuni p e a ~ s wlthinthe recorder chart range. The atten).lator. must by,ccurate tqwithin 0.5 % between the attenuator range steps. ,,5.4 Sample Inlet System:5.4.1 The sample inlet system shall be constructed ofmaterials that are inert and nonadsorptive with respect to thecomponents in the sample. The preferred material of construction is stainless steel. Copper, brass, and other copperbearing alloys are unacceptable. The sample inlet systemfrom the cylinder valve to the GC column inlet must bemaintained at a temperature constant to 1 c.5.4.2 Provision musibe niade to introduce into the carriergas ahead of the analyzing column a gas-phase sample that has been entrapped in a fixed volume loop or tubular, section. The fixed loop or section shall be so constructed thatthe total volume, incl\lding d ~ a d space, shall not normallyexceed 0.5 mL at 1 atm. Ifincreased ac

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~ t D 1945TABLE 1 Natural Gas Components and Range ofComposition Covered

ComponentHeliumHydrogenOxygenNitrogenCarbon dioxideMethaneEthaneHydrogen sulfidePro pan eisobutanen-ButaneneoPentaneisoPentanen-PentaneHexane isomersHeptanes plus

Mol%0.01 to 100.01 to 100.01 to 200.01 to 1000.01 to 200.01 to 1000.01 to 1000.3 to 300.01 to 1000.01 to 100.01 to 100.01 to 20.01 to 20.01 to 20.01 to 20.01 to 1

NOTE 1-The sample size limitation of0.5 mL or smaller is selectedof detector response, and efficiency of column

in order to increase measurement accuracy.5.4.3 An optional manifold arrangement for entering

in Fig. l.5.5 Column Temperature Control:5.5.1 Isothermal-When isothermal operation is utilized,at a temperature constant toduring the course of tlie sample run and corresponding

5.5 .2 Temperature Programming-Temperature program

in the column.5.6 Detector Temperature Control-Maintain the detectorat a temperature constant to 0.3c during the

of the sample ri.m and the corresponding referenc

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~ t D 1945

_J

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o 1945COLUMN-25% BMEE on Chromosorb P,7 meters @ 25CCARRIER GAS: He1ium@ 40 mL,/min.SAMPLE SIZE: 0.25 mL.

co0 \

o"'co o. ~:S: -....o (. )~ "'.)

18 16 14 12 8Minutes

6 ' 4 2

FIG. 4 Chromatogram of Natural Gas (BMEE Column) (See Annex A2)

COLUMN-: Chromo;orb PAW, 200/500,,, 10q :,::~CARRIER GAS : Helium @ 40 mL./min. f:'-!:i : , : : ~

~ J:I::SAMPLE SIZE: 0.25 mL E-!~ p., ~ ~:,:: ::r:: :,::~30 25 20 15 10 5 o

Minutes

o

FIG. 5 Chromatogram of Natural Gas (Silicone 200/500 Column) (See Annex A2)of pressure can be entered. With either type

mm scale can be read more accurately thanbe used handling mercuryof its toxic nature. Avoid contact with the skin aspossible. Wash thoroughly after contact.5.12 Vacuum Pump-Must have the capability of pro

of 1 mm of mercury absolute or less.54

6. Preparation of Apparatus6.1 Linearity Check-In order to establish linearity ofresponse for the thermal conductivity detector, it is necessaryto complete the following procedure:6.1.1 The major component of interest (methane fornatural gas) is charged to the chromatograph by way of thefixed-size sample loop at partial pressure increments of 13

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dt D 1945COLUMN: DIDP-3rrieter +DMS-6meter ~@ 35C. H:,::CARRIER GAS: Helium @ 75 mL./min. ;SAMPLE SIZE: 0.5 mL. z:,::z 8o p::

14 16 18 20

,")1

. (" .

ZN

' FIG. 7 Chromatogram of Natural Gas (Multi-Column Application) (Se Annex A2)kPa (lOO mm Hg) from 13 to 100 kPaOO to 760 inm Hg)or the prevailing atmospheric pressure. ' '6. [2 . The ntegrated peak responses for the area generatedat each of tle pressure increments are plotted verus theirpartial pressure (see Fig. 9). 6.1.3 The plotted results should yield a straight line. Aperfectly linear response wmild display a straight Ilne at ~ 4 ~

angle using the logarithmi valus. ., .6.1.4 Any cun'ed line indicates the f i ~ e d volm:he sample~ o o p is too large. A smaller loop size should teplace the fixedvolume loop and 6.1.1 through 6.1.4 should be repeated (seeFig. 9). . . . . '6.1.5 The li:O.earity over the range of interest must beknownfor each component.It is usefui.to constrU.cta table

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o 1945o2 meter X 3mm mol. sieve 13x @ 50 CArgon carrier@ 40 mL./min.Detector @ l O O n ~ .

5 4 3 2 1 oMinutes

FIG. 8 Separation of Helium and Hydrogennoting the response factor deviation in changing concentration. (See Table 2 and 3).6.1.6 lt should be noted that nitrogen, methane, andethane exhibit less than 1 % compressibility at atmosphericpressure. Other natural gas components do exhibit a significant compressibility at pressures less than atmospheric.

6.1. 7 Most components that have vapor pressures of lessthan 100 kPa (15 psia) cannot be used as a pure gas for alinearity study because they will not exhibit sufficient vaporpressure for a manometer reading to 100 kPa (760 mm Hg).For these components, a mixture with nitrogen or methanecan be used to establish a partial pressure that can extend thetotal pressure to 100 kPa (760 mm Hg). Using Table 4 forvapor pressures at 3sc (lOO.F), calculate the maximumpressure to which a given component can be blended withnitrogen as follows:

B = (100 X V)/iP = (i X M)/100

where: _B = blend pressure, max, kPa (mm Hg),V = vapor pressure, kPa (mm Hg),i =mol%P = partial pressure, kPa (mm Hg), andM = manometer pressure, kPa (mm Hg).6.2. Procedure for Linearity Check: .

(2)(3)

6.2.1 Con;1ect the pu:re-component source to the sampleen,try system. Evaouate the sample-entry system and observetbe manomter fqr I e ~ , ~ ; ~ s . (See Fig. 1 for a suggested manifoldarrangement.) The sample-entry system must be vacuum tight.6.2.2 Carefully open the needle valve to admit the purecomponent up to 13 kPa (100 mm Hg) of partial pressure.

6.2.3 Record the exaci partial pressure and actuate the56

sample valve to place the sample onto the column. Recordthe peak area of the pure componen .6.2.4 Repeat 6.2.3 for 26, 39, 52, 65, 78, and 91 kPa (200,300, 400, 500, 600, and 700 mm Hg) on the manometer,recording the peak area obtained for sample analysis at eachof these pressures.

6.2.5 Plot the area data (x axis) versus the partial pressures(y axis) on a linear graph as shown in Fig. 9.6.2.6 An alternative method is to obtain a blend of al! thecomponents and charge the sample loop at partial pressureover the range of interest. If a gas blender is available themixture can be diluted with methane thereby giving responsecurves for all the components.NOTE 5: Caution-If it is not possible to obtain information on thelinearity of the available gas chromatograph detector for aii of the testgas components, then as a minimum requirement the linearity datamust be obtained for any gas component that exceeds a concentration of5 mol %. Chromatographs are not truly linear over wide concentrationranges and linearity should be established o ver the range of interest.

7. Reference Standards7.1 Moisture-free gas mixtures of known composition arerequired for comparison with the test sample. They mustcontain known percents of the components, except oxygen(Note 6), that are to be determined in the unknown sample.All components in the reference standard must be homogenous in the vapor state at the time of use. The concentrationof a component in the reference standard gas should not beless than one half nor more than twice the concentration ofthe corresponding component in the test gas.NOJ:E 6-Unless the reference standard is stored in a container thathas been tested and proved for inertness, to oxygen, it is preferable to

calibrate for bxygen by an alternative method.

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~ f f i l 1 D 1945-

11

11 11' i 11 1 ' ;l i 1 1 1800 1 11 ,, 1 1 1 ~1 1 ii:11 11; i i 11 lill ! . i! 1i"l i700 ! i l [ll 1:! ! . i 111 i .,, 1 !: 1'1 1 t i i 1 1 1 11 1 1 ! : ! '1 ' !1 1 iil j 1 '1 :! il 11 i1:'i 1 '600! i ! i i 1 1 1 .1: !i! 1 1 1 ~ r ! 1 1'j 1 1 1: 1 11 1 1 i l: \: !1 [1 1 1 11 11:1: 1! 1 lfl 1: 1 1 1 l! . 1 11 ' ' ',i_1 500>J:EE '! l . ; i i 1 i 1' :! rr 111 : 11 '! : i ! ;: !1 ! 11. 1: i i.J . 1 l ' \ ' ,1 1! 1 1 .. ; i""'"' 400'! 1 ; ' i l: i i i i!' i1!!o..9!"i , !!! ::11! 1! Ir 1 !JI i.!!

o"'o< 300"j ! 1 1 1 1 ' l': ; 11 1i! 1 1 1i200!1 !1001

o 10,000

11 . 1:11 11

l.1 '11 '

30,QQO

V:fl: 1 ! ' i: !1 : 1' i :'1 i!_lil,,, 11; . Methane

i 1 1lt i' ' 111i; : ! 1

1 i111

1 1!1 1

sp,oooArea Count

, .11

70,000 90,000 10001 ' o'FIG. 9 Linearity of Detector Response

TABi.E 2 Linearity Evaluation of MethaneS/B diff = (low mole % :- high mole %)/low mole % x 100

B area S mole% S/B mole %farea S/B diff., % on lowvalue223119392 51 2.2858e-07242610272 56 2.3082e-07 ..:.o.98261785320 61 2.3302e-07 -0.95280494912 66. 2.3530e-07 -0.98299145504 71 2.3734e-07 -0.87317987328 76 2.3900e-07 . -0.70336489056 81 2.4072e-07 -0.72351120721 85 2.4208e-07 -0.57

7.2 Preparation-A reference sta11-dard may be preparedby blending pure components. Diluted dry air is a suitablestandard for oxygen and t t ~ o g e n (see 8.5.1 )._56 8. Procedure . .8.1 Instrument Preparation'-Place the proper column(s)in operation as needed for the desired ru n (as described ineither 8.4, 8.5, or 8.6). Adjust tlie operating conditions and

s A suitable reference standard is available from Phillips Petroleum Co., Borger,TX79007. ' : .. 6 A. ten-component reference standard traceable to the National Institute ofStandards and Technology (NIST) is a ~ a i l a b l e from Institute of Gas Techno!gy(IGT), 3424 S. State St., Chicago, IL 60616'.

57

TABLE 3 : i ~ ~ ~ t i y E v , a l u t i ~ n for N i t r o g ~ ~S/B diff ;.,. (low mole % :- high mole %)flow mole % ?< '100

B area58798362913706657452364 84953192111491232 .137268784 .162852288187232496

1'. 510.15:202530 .35

S/B mole %/area S/B diff., %on low ,.. yalue,1.7007e-:07 .1.71609-071.704se-o? 1.7657e-07. '.- .1..7939e-071.8212e-071.8422e-07. 1.8693e-07

-0.89.-1.43-1.44"-1.60.-1.53-1.15.:..1.48;

TABLE 4 Vapor Prssur at 38C (100F)AComponen!

NitrogenMethane Carbon dioxideEthaneHydrogen sulfidePropane lsobutanen-Butanelsopentanen-Pentanen-Hexanen-Heptane

kPa absoluta ' '>34 500'>34 500>5 520>5 5202 7201 300501356. 141

'10834.211.2

psia:>5 000>5 000'

>800>80039.5189.72.651.720.515.64.961.62

A The r:nost recnt d ~ t a for the vapor pressures listed are a ~ a i l a b l e from theThermodyramics Research Center, Texas A&M University System, CollegeStation, TX 77843.

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~ f f i ~ D .1945

8.1.1 For hexanes and higher, h ~ a t the sample loop.NOTE 7-Most modeni chromatographs have valve ovens that canis strongiy recom111eiJ.ded in a b s ~ ? n c e ofve ovens to mount the gas sampling valve in-the chromatograph ovend operate at the column temperature.8.1.2 After the n s t r u m e n t has apparently stabilized; make

uns on the reference standard to establish instrumentl..% amount present of each component. Either the a v e r a g ~the two consecutive checks, or the latest check agreeing% ofthe previous check on each component may beis a change in instru;nent operating conditions. Dailyare recommended. '8.2 Sample Preparation-Ifdesired, hydrogen sulfide may(see Annex A2.3).8.2.1 Preparation and lntroduction of Sm?Zple-Samples

l ~ b o r a t o r y at 20-50"F above theof the field sampling: The higher theof 300 mL or

e n t r ~ n ~ d liquids. If the hydrocarbonofthe sari:tple is.known to be lower than the lowesttb which the sample has been exposed, it is not8.2.2 Connections from: the sample container to theof the instrument shduld be made with stainless,,1lbieces of TFE-fluorocarbon. Copper,or rubber connections are not aqceptab!e. H e a ~ e d lines8.3 Sample Introduction-The size of the sample intro

to the chromatographic columns shall not exceed 0.5.size is necessary to obtain a lineardeterlnination of all but the minar constitbythe use ofthis sample size. When increased responserequir6d for the determination of components present in%, it is permissible to

and reference standard volumes not exceeding 5of liquids into the sample system.)8.3.1 Purging Method-Open th'e outlet valve' of theand sample loop or tube. The amount of purging

The sample loop pressure shoJ.Ild be near atmospheric.ve and allow the pressure of the sampleor tube to stabilize. Then immediately inject theof the loop or tube into the chromatographicavoid infiltration of contaminants.8.3.2 Water Displacemerlt::.._Ifthe sample was obtained by

and fill the sample loop or tube.NOTE 8: Caution-Some components, such as carbon dioxide, hy-

and hexanes and higher hydrocarbons, may be partiallyed by the water.8.3.3 Evacuation Method-Evacuate the charging system,lve on the sample cylinder, to less than 0.1 kPa ( 1mm Hg)

58

a b s o l ~ t e pressure. Clase the valveto the vacuum source andcarefully meter the fuel-gas sample ftoin the sample cylinder until .the sample loop is' filled to the desired pressure, asindicated on the manometer (see Fig. 1). Inject the sampleinto. the chromatograph. 8A Pattition Column Runfor Ethane and Heavier Hydro-,carbons and Carbon Dioxide - This run is made using eitherhelium or hydrogen as the carrier gas; if othyr than a thermalconductivity detector is used, select a suitable carrier gas forthat detector. Select a sample size in accordance with 8.1.Enter the sample, and backflush hea\Ty components whenappropriate. Obtain a crresponding response on the refer-ence standard. .8.4.1 Methane may also be determined on this column ifthe column will separate the methane from nitrogen andoxygn (such as with silicone 200/500 as shown in Fig. 5),and the sample size does not exceed 0.5 mL.8.5 Adsorption Column Run for Oxygen, Nitrogen, andMethane-Make this run using helium or hydrogen as thecarrier-gs. The sample size must not exceed 0.5 mL for thedetermination of methane. En er the sam)le and obtain a re-sponse through methane (Note 6). Likewise, obtain a re-sponse on the reference standard fot nitrogen and methane.ObtiB a response on dry air for nitrogen and oxygen, if desired. The air must be either entered at an accurately measured reduced pressure, or from a heliuril-diluted mixture.8.5.1 A mixture containing approximately 1 % of oxygencan be prepared by pressurizing a container of dry air atatmospheric pressure to 2 MPa (20 atm) with pure helium.This pressure need not be measured precisely, as the concentration of nitrogen in the mixture' thus: prepared must bedetermined by cm;nparison to nitrogen in the referencestandard. The percent nitrogen is multiplied by 0.268 toobtain the mole percent of oxygen, or by 0.280 to obtain themole percent total of oxygen and argon. Do not rely onoxygen standards that have been prepared for more than afew days. It is permissible to use a response factor for oxygenthat is relative to a stble constituent.8.6 Adsorption Column Runfor Helium and HydrogenMake this run using either nitrogen or argon as the carriergas. Enter a 1 to 5-mL ~ a m p l e and record the response forhelium, followed by hydrogen, which will be just ahead ofoxygen (Note 6). Obtain a corresponding response on areference standard containing suitable concentrations ofhelium and hydrogen (see Fig. 8).9. Calculation9.1 The number of significant digits r e t a i n e ~ for thequantitative value of each component shall be such t l ~ a taccuracy is neither sacrificed or exaggerated. The expressednumerical value of any component in the sample shouldinotbe presumed tq be .more a c c u ~ a t e than . t11e correspondingcertified value ofthat component jn the calibration standard.9.2 Exterrial Standard e t h o d ~ 9 2.1 Pentanes Lighter Components-Mesure theheight of each component peak for pentanes and lighter,convert to the same attenuation for corresponding components in the sample and reference standard, and calculate-theconcentration of each c o m p o n ~ h t in the s a . m p ~ e as follows:

C=Sx(A/B) (4)

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o 1945where:C = component concentration in the sample, mol %,A = peak height of component in the sample, mm,B = peak height of component in the standard, mm, andS = component concentration in the reference standard,

mol%.9 2.1.1 If air has been run at reduced pressure for oxygenor nitrogen calibration, or both, correct the equation forpressure as follows:

C =S X (AjE) X (Pa/Pb) (5)where:Pa = pressure at which air is run, and . .Pb = true barometric pressure during the run, with bothpressures being expressed in the same units.9.2.1.2 Use composition values of 78.1 % nitrogen and21.9 % oxygen for dry air, because argon elutes with oxygenon a molecular sieves column under the normal conditionsof this test method.9.2.2 Hexanes and Heavier Components-Measure theareas of the hexanes portian and the heptanes and heavierportian of the reverse-flow peak (see Annex Al, Fig. Al.l ,and Appendix X3.6). Also measure the areas ofboth pentanepeaks on the sample chromatogram, and a'djust all measuredareas to the same attenuation basis.9.2.3 Calculate corrected areas ofthe reverse flow peaks asfollows:

Corrected C6 area = 72/86 x measured C6 area (6)Corrected C7 and heavier area' = 72/A x measured C7 artd heavier area .(7)where A = average molecular weight ofthe C7 and h e ~ v i e rfraction. NOTE 9-The value of 98 is usually sufficiently accurate for use asthe C7 and heavier fractiii. average molecular weight; the small amountof C8 and heavier present is usually offset by the lighter methylcyclopentane and cyclohexane that occur in this fraciion. A moreacurate va:Jue for the ni.blectilar weight ofT 7 and heavier can beobtained as described in Annex AU.9 2.4 Calctilate the concentrOri of the two fractions inthe s ~ m p l e as follows: .,

:NJ;ol% c6 = (coqected c6 area)'. . . . X (mol %iC5 + nC5)/(iC5 +nC5 area). (8)Mol% C7+ = corrected C7 area)

X (mol % iC5 + nC5)/(iC5 + nC5 area). (9)

9 2.4.1 If the mole percent of iC5 + nC 5 has beendetermined by a separate run with a smaller sized sample,this value need not be redetermined.9.2.5 The entire reverse flow area may be calculated inthis manner as C6 and heavier, or as C5 and heavier shouldthe carrier gas reversa! be made after n-butane. The measured area should be corrected by using the average molecular weights of the entire reverse-flow components for thev ~ l l u e of A. The mole percent and area of the iC5 an d nC 5reverse flow peak of an identica'lly sized sample of referencestandard (free of C6 an d heavier) shall then be used forcalculating the final mole percent value.9.2.6 Normalize the mole percent values by multiplyingeach value by 100 and dividing by the su m of th e originalvalues. The sum ofthe original values should no t differ from100.0% by more than 1.0 %.9.2.7 See sample calculations in Appendix X2.10. Precision10.1 Precision-The precision of this test method, asdetermined by the statistical examination of theinterlaboratory test results, for gas samples of pipelinequality 38 MJ/m3 (1000 Btu/SCF) is as follows: 1O 1.1 Repeatability-The difference between two successive results obtained by the same operator with the same.apparatus under constant operating conditions oh identical

test materials should be considered suspect if they .differ bymore than the following a:mounts:

Component, 'mol %O o'O.l 0.1 to 1.01.0 to 5.05.0 to 10Over 10

Repeatability0.010.040.070.080.10

10.1.2 Reproducibility-The difference between two results obtained by different operators in different laboratori eson identical test ma'terials should be considered suspect ifthey differ by more tha:n the following amounts:

11. Keywords

Component; mol %Oto 0.10.1 to l.1.0 to 5.0. 5.0 to 10 .:, Over 10

,. J ",. '.

Reproducibility0.020.070.10'

'0.120.15

n .1 gas analysis; gas chrbinatography; natural gas com.:.position ANNEXES

(Mandatory Information)Al. SUPPLEMENTARY PROCEDURES

Al.l Amtlysis (or only Pn>pam; and Heavier .Components . ;A l. L1 This determination can be made in 10 to 15-minrun time: by using column conditicins to separate propane,isobutane,. n-butane, i s o p e n t ~ n e , n-pentane, hexanes andheptanes, and heavier, but disregarding separation on ethanea:nd lighter. ..A1.1.2 Use a 5-m bis-(2(2-methoxyethoxy) ethyl)ether(BMEE) columh at about 30C, or a suitable Jength of

59

.another partition column that will separate propane throughn-pentane in about 5 min. Entera 1 to 5-mL sample into thecolumn a11d reverse the carrier gas. flow after n-pentane isseparated. Obtain a corresponding chromatogram on thereference standard, which c,an be accomplished in about 5-min ru;Q. time, as there .is no need to reverse the. flow on therefei-ence standard. Make calculati6ns in the sam manner asf ~ H ; , t h e c o m p l e t analysismetho.d. . ' .

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D 1945

~ + ~:X: E-!J:;il ~ ~~ J:;il~ ~ ~E-! E-! J:i!E-i

~ z ~ ~:;il1 ~ ~ ~~ ....:~ ~ E-!~ ~ E-! ~ ( " ):X: ~ 1:X: :X: J:;il ('!('!J:;i!J:;il :::e: 1+ :::e: :::e: ("))~ o-:tr.l -:p::~ OE-il ~-! [ ; ~-

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LONG PARTITIONCOLUMN

o 1945

SHORT PARTITIONCOLUMN

(For Spplementary Use Only)) ABSORPTION COLUMNCARRIER GAS FROMSAMPLING VALVE TO COLUMN

CARRIER GASFROM COLUMNTO DETECTOR

FIG. A2.1 Column Arrangementhexanes and heavier components are to be determined, Fig.A2.1 shows an arrangement whereby columns can be quicklyand easily changed by the turn of a selector valve. Twocolumns are necessary to determine all of the componentscovered in this test method. However, short and longpartition cohimns provide the flexibility of three partition

column lengths, by using them either singly or in series. Theconnection between V1 and V2 in Fig. A2.1 should be asshort as possible (20 mm is practica!) to minimize dead spacebetween the columns:when used in series. If all9olumns ::1rechosen to opera e at the same temperature, then stabilizationtime between changing columns will beminimized.APPENDIXES

(Nonmandatory Information)Xl . REFERENCE STANDARD MIXTURE

Xl.l PreparationX1.1.1 Gas mixtures of the followirtg typical compositionswill suffice for use as reference standards for most analyticalrequirements (Note Xl.l):

Lean gas, mol Rich gas, molComi'onent %' %Helium 1.0 0.5Hydrogen , 3.0 . 0.5Nitrogen 4.0 0.5Methane (maximum) 85 74Ethane 6.0 1OCarbon dioxide ,1.0 LOPropane 4.0 7.0Isobutane 2.0 3.0n-Butane 2.0 3.0neopentane 0.5 1.0Isopentane . 0.5 .l.Qn-pentane 0.5 1.0Hexanes + 0.1 0.2NoTE XI.f - I f the mixture is stored under pressure, take care toensure that the partial pressure of any component does not exceed itsvapor pressure at the temperature and pressure whicp the sample istored and used. The Leap mixture has a cricondentherm at 60aF andhe Rk h mixture has a cricondentherm at 100F.

X 1.1.2 A useful method for preparation of a referenceis as follows: 5X l. L2.1, Obtain the following equipment and material:

61

Cylinder, 20-LPressure Cylinders, two 100-mL (A and B)Balance, 2000-g capacity, sensitivity of 10 mg. .Pure Components, methane through rz-pentane, carbondioxide. The pure components shoulci be 99+ % pvre.Methane should be in a 1-L cylinder at 10 MPa (100-atm)pressure. Run a chromatogram of each component to checkon its given compositiori.X1.1.2.2 Evacuate the 20-L cylinder for several hours.Evacuate 100-mL Cylinder A, and obtain its true weight.Connect Cylinder A to a cylinder of pure n-pentane with ametal connection Of calculated length to contain approximately the amount bf n-pentane to be added. Flush theconnection with the n"pentane by loosening the fittirig at thevalve on Cylinder A. Tighten the fitting. Close the n-pentanecylinder valve and open Cylirtder A val ve to admit then-pentane from the connection and then close the valve onCylinder A. Disconnect and weigh Cylinder A to obtain theweight of n-pentane added.X1.1.2.3 Similarly, add isopentan, n-butane, isobutane,pro pane, ethane, and .carbon di oxide, in 'that order, asdesired, in the reference standard. Weigh Cylinder A aftereach addition to obtain;the weight of the component added.Connect Cylinder A. to the evacuated20-L cylinder with as

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~ t D 1945

......1 1 BUTAHE9994.Hl

A 75891'7

R 6.11488EA 46693"1

31.4649

159383

8 .158 8.388 8.458 8 .688 8.'758 8 .988 1.888

Mole%FIG. X1.1 Example of Deriving a Relative Molar Response Factor

TABLE X1.1 Least Square Calculation for Slope of iso-Butanearea mole% 1y X XY. y2

984515 1 984515 9.693e+11900410 0.9 810369 8.107e+11758917 0.75 569187.75 5.670e+11611488 0.6 366892.8 3.739e+11466037 0.45 209716.65 2.172e+11314649 0.3 94394.7 9.900e+10159303 0.15 23895.45 2.538e+10

sum = 4195319 4.15 3058971.35 3.071452e +12slope = 'J:XYf'J:Y2 9.9594e-07

hort a clean, small-diameter connector s possible. Open thealve on the 20-L cylinder, then open the valve on CylinderThis will result in the transfer of nearly all of the contentsf Cylinder A into the 20-L cyli1;1der. Close the cylinderalves, disconnect, and weigh Cylinder A to determine the

of mixture that was not t r a n s f e r r ~ d to the 20-LXl.l.2.4 Evacuate and weigh 100-mL Cylinder B. ThenCylinder B with helium and hydrogen respectively to theressures required to provide the desired co:o.centrations of

re prepared, a1;1.d measured separately from the other comonents to prevent their pressures, while in the 100-mLylinder, from causing condensation of the higher hydrocarons.) Weigh Cylinder B after eaeh addition to obtain theeight of the component added. Connect Cylinder B to theort a clean, small-diameter connectorB, which will result in the transfer of

early all of. the contents of Cylinder B into the 20-L62

Cylinder Bto. obtain the weight of the mixture that was nottransferred to the 2 0 ~ L cylinder. ,Xl.l.2.5 Weigh a 1-L cylinder containing pure methaneat about 10-MPa (100-atm) pressure. Transfer the methaneto the 20-L cylinder until the pressure equalizes. Weigh the1-L cylinder to determine the weight ofmethane transferred.Xl.L2.6 Thoroughly mix the contents of the 20-L cylinder by heating at the bottom by a convenient means suchas hot water or a heat lamp, and leaving the cylinder in avertical position for at least 6 h.Xl.l.2.7 Use the weights and purities of all componentsadded to calculate the weight composition of the mixture.Convert the weight percent to mole percent.Xl.2 Calibration with Pure Components

X1.2.1 Use helium carrier gasto admita sample volumeof 0.25 to 0.5 mL into the adsorption column, providingmethane at 50 kPa (375 mm Hg) and nitrogen at 10 kPa (75mm Hg) absolute pressure. Run a sample of the stanqardmixture at 70 kPa (525 mm Hg) pressure, and obtain peaksfor methane and n.itrogen. '

NOTE Xl.2-Each run made throughout this procedure should berepea:d to ensure that peak heights are reproducible after correction forpressure differences to within 1 mm or 1 % ofthe mean value. All peaksshould be recorded at an instrument attenuation that gives the max-imum measurable peak height. 'Xl.2.2 Change the carrier gas to argon or nitrogen and,after the base line has stabilized, enter a sample of purehelium at 7 kPa (50 mm Hg) absolute pressure;recording thepeak at an attenuation that allows maximum peak height.Run a sample of the mixture at 70 kPa (525 mm Hg)absolute pressure, and obtain the helium pak.X 1.2.3 Switch to the partition column with' helium carriergas, and run the gas mixtureat 70 kPa (525 mm Hg) absolute

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.o 1945TABLE X1.2. Calculation of Response Factors Using Relative Molar Response Values

Comp.

NitrogenMethaneEthanePropaneCarbon Dioxideiso-Butanen-Butaneneopentaneiso-Pentanen-PentaneHexanes +

Mole% inReferenceStandardS

5.0882.158.754.02

Response ofR e f e r e n c ~ . .StandardB26858853664238463285243552767

Response FactorFrom ReferenceStandard

SfB,K1.8914E-62.2419E-61.3826E-61.1315E-6

Relativa MolarAResponse from

Slope/K1RMR 1

1.11607c20.72958ca0.69310ca0.68271ca0.63874ca0.60041ca0.54762ca

Response Factorof ReferencedComponents

(RMR1)x(K1

1.5429E-69.9594E-79.1142E-78.9776E-78.3994E-77.8953E-77.2012E-7

A The Relativa Molar Response is a constant that is calculated by dividing the slope of the referenced component by the component that is present in the referenceRMR104 = (slopeic4)/(Kc3 ) == 9.9594E-7 1.1315E-6 = 0.72958

Then admit samples of pure ethane and propane atO kPa (7 5 mm Hg) absolute pressure, and butanes,and carbon dioxide at 5 kPa (38 mm Hg) absolute

X1.2.4 Run the gas mixture at 70 kPa. (525 mm Hg)X1.2.5 Calculate the composition of the prepared gasure as follows:X1.2.5.1 Correct peak heights of all pure components and

in the blend to the same attenuaX1.2.5.2 Calculate the concentration of each componentfollows:

component concentration, mol%,= peak height of component in blend,= peak height of pure component, '= pressure at which blend is nm, kPa (mm Hg),= pressure at which component is run, kPa (nim Hg),d= volume fraction of pure componen .

NoTE X 1.3....,.. fj- = 1.000 if the calibration componenHs free ofX1.2.5.3 Normlize valuesto 100.0 %..3 Calibration using Relativ Molar Response Values

X1.3.1 Relative response ratios can be derived frmdata and used for calculating response factors. This

the need for amul ti-component standard for dailyThe testmethod can be used on any gas chro

or thermistor.. ' X1.3.2 Obtain a blend that brackets the expected concen

the instrument will be analyzing. The major compone) is used as. the .balance gas and,may fall belown. This component is present in theis ' a:ssured Jromtests.)(l.33 Inject the sample at reduced pressures using th ein Fig. 1 or using a mechanical gas )Jlender.Obtain

peak areas or height at 90 ,%, 75 %, 60 %, 45 %,63

30 %, and 15 %, ofabsolu te pressure. Fo r 100 kPa (760 mmHg) the pressures used are 90 kPa (684 mm Hg), 75 kPa (570mm Hg), 60 kPa (456 mm Hg), 45 Kp a (342 mm Hg), 30kPa (228 mm Hg), 15 kPa ( 114 mm Hg).X1.3.4 Plot the area or height (attenuated at the sameheight as the reference component) versus concentration andcalculate the slope of the line by the least squares method.Given the equation f the line as Y = a0 + a1X yvhere Yrepresents the area or height points and Xthe concentrationpoints. The line is assumed to intersect th rough the originand a0 =O. The slope a1 can be calculated by:

2;XYa = (2;Y)2. (Xl.l)

X1.3.5 Ratio the s.lopes ofthe referenced components (i )to the slopes of the reference compomints (r) present in thedaily calibration standard. This gives the Relative MolarResponse factor (RMR) for component (i). The referencecomponent must be present in the same instrumentrusequence (except Hexanes+) as the referenced components.For instance, propane can be the reference component forthe butanes andpentanes ifpropaneis separated on the samecolumn in the same sequence as the butanes and pentanes.Ethane can bethe reference component for carbon dioxide'ifit elutes in the saine sequence as carbon dioxide. Thehexanes + peak can be referenced to ptopane or calculated asmentioned in the body of the standard.X1.3.6 For daily calibration a four component standard isused containing nitrogen, methane,' ethane, and propane.The fewer components eliminates dew point problems,reactivity, is more accurate and can be blended at a higherpressure. The referenced coni.ponents' response factors arecalculated from the current reference factor and the RelativeMolar Response factor. Following is a description of thebasic calculations, an example of deriving a Relative MolarResponse factor (Fig; X1.1 ), an d a table showing howresponse factors are calculated (Table X1.2).

Mole%Response Factor (R) = - - - , (X1.2)Area. Mole %(i)/Area(i)Relat!ve Molar Response (RMR;) = . %. (X1.3): Mole o(r)/Area(r)

Rc4 = RMRc4 X Re, (Xl.4)

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~ ~ o 1945X1.3.7 Periodic checks ofthe RMR relationship is recommended. The relationship is independent of temperature,sample size, and carrier gas flow tate. If changes occur in

these operating conditions, all of the components will beaffected equally and the calculated response factors will shiftaccordingly. See Table Xl.l and Figs. Xl.l and Xl.2.X2. SAMPLE CALCULATIONS (SEE SECTION 9)

TABLE X2.1 Sample CalculationsMol% in Response of Reference Response Response for Sample,A PercentComponent Reference Normalizad, %Standard, S Standard, B Factor, SjB A C =(S X A)/B

Helium 0.50 41.1 0.0122 12.6 0.154 0.15Hydrogen 0.74 90.2 0.0082 1.5 0.012 0.0'1Oxygen 0.27 35.5 0.0076 2.1 0.016 0.02Nitrogen 4.89 77.8 0.0629 75.6 4.755 4.75Methane 70.27 76.4 0.9198 90.4 83.150 83.07Ethane 9.07 96.5 0.0940 79.0 7.426 7.42Carbon dioxide 0.98 57.5 0.0170 21.2 0.360 0.36Propane 6.65 55.2 0.1205 20.6 2.482 2.48/sobutane 2.88 73.2 0.0393 11.0 0.432 0.43n-Butane 2.87 60.3 0.0476 15.0 0.714 0.71neopentane 0.59 10.4 0.0567 0.1 0.006 0.01lsopentane 0.87 96.0 0.0091 24.0 0.218 0.22n-Pentane 0.86 86.8 0.0099 20.5 0.203 0.20Hexanes +0 72.1 8 0.166 0.17100.094% 100.00%

A The response for a

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D 1945will enlarge the reverse flow peak.X3.5.4 Be sure the column is clean by occasionally giving

of carrier gas in reverse flow direction.be quickly attained in either flowif the column is clean.X3.5.5 When the reverse flow valve is turned there is aof pressure conditions at the column ends thatgas flow. This flow should quickly return toflow rate and the base line level out. If it does not,gas system, faulty flow

of the column or

StandardX3.6.1 Maintain the reference standard at +15 oc or ais above the hydrocarbon dew point. lf thebe exposed to lower temperatures,

If in doubt' about the composition, check theAV

M e ~ s u r e m e n t s)(3.7.1 The base line and tops of peaks shol.lld be plainly

. Do not use a- . . . ' . . -

fixed zero line as the base line, but use the actual observedbase line. On high sensitivity, this base line may drift slightlywithout harm and it need not frequently be moved back tozero. A strip chart recorder with an offset zero is desirable.Th area of reverse flow peak may be measured by planimeter or geometric construction. The reverse flow area, andthe pentanes peaks used for comparison should be measuredby the same method. That is, use either geometric construction or planimeter, bu t do not intermix. When a planimeteris used, carefully make several tracings and use the average.Check this average by a seco11d group of tracings.X3.8 Miscellaneous

X3.8.1 Moisture in the carrier gas that would cause troubleon the .reverse flow may be safeguarded againstby:installinga cartridge of molecular sieves ahead of the i n ~ t r u m e n t .Usually 1 m of 6-mm tubing packed with .30 to 60-meshmolecular sieves is adequate, ifchanged with eac:h cylinder ofcarrier gas.X3.8.2 Check the carrier gas flow system periodically forleaks with soap or lealc detector. solution. ,X3.8.3 Use electrical contact cleaner 011 the a,ttenuator ifnoisy contacts are indicated. . . .X3.8.4 Peaks with .square tops with ornission . of smallpeaks can be caused by a sluggish recorder. If this conditioncannot be remedied by adjustment of the gain, check theelectronics in the recorder.

. The American Society for Testing and a t ~ r i a l s takes no position respectingthe validity of arl}'patent rights asserted in conne;tionwith any tem mentioned in this standard. Users of this starr:tard are express/y advised that determination of the validity of any such,: patent rigtits; and the risk of infringement of such rights, are entirely their own responsibility.

,,.

This standard is subject to revision at any time by the responsible technica/ committee and must be reviewed. every five years andif not revised, either reapproved or withdrawn . .Your conmems are invited either for revision of this standard or for additional stani:Jardsand should be addressed to ASTM Headquarters. Your comments wi/1 receive careful consideration at a meeting of the responsibfe'technica/ committee, which you may attend. lf you feel that your comments have not received a fair hearing you should make yciur views known'to the ASTM Committee on Standards, Barr Harbar Orive, West Conshotocken, PA 1942.8. !

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