1、Designation: D2427 06 (Reapproved 2011)Standard Test Method forDetermination of C2through C5Hydrocarbons in Gasolinesby Gas Chromatography1This standard is issued under the fixed designation D2427; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the two(C2) through five(C5-) carbon paraffins
3、 and mono-olefins ingasolines. The concentrations by volume or mass (weight) ofthe following components are generally reported:1.1.1 Ethylene plus ethane1.1.2 Propane1.1.3 Propylene1.1.4 Isobutane1.1.5 n-Butane1.1.6 Butene-1 plus isobutylene1.1.7 trans-Butene-21.1.8 cis-Butene-21.1.9 Isopentane1.1.1
4、0 3-Methylbutene-11.1.11 n-Pentane1.1.12 Pentene-11.1.13 2-Methylbutene-11.1.14 trans-Pentene-21.1.15 cis-Pentene-21.1.16 2-Methylbutene-21.2 This test method does not cover the determination ofcyclic olefins, diolefins, or acetylenes. These are usually minorcomponents in finished gasolines.1.3 Samp
5、les to be analyzed should not contain significantamounts of material boiling lower than ethylene.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4.1 ExceptionAlternative units, in common usage, arealso provided to improve
6、the clarity and aid the user of this testmethod.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of reg
7、ulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2001 Test Method for Depentanization of Gasoline andNaphthas3. Summary of Test Method3.1 The sample is injected into a gas-liquid partition col-umn. The components are separated as they pass through thecolumn with an inert
8、carrier gas and their presence in theeffluent is detected and recorded as a chromatogram. Materialscontaining components having more than five carbon atomscan either be backflushed from the system without measure-ment, or recorded as a broad peak by reversing the direction ofthe carrier gas through
9、the column at such time as to regroupthe higher-boiling portion (C6and heavier) of the sample. Ifbackflushing is used, the concentration of C2through C5hydrocarbons may be related to the whole sample by adding aknown quantity of low-boiling internal standard to the sampleprior to analysis. Alternati
10、vely, a known amount of sample canbe charged and compared to a standard sample run under thesame conditions. Sample composition is determined from thechromatogram by comparing peak areas with those obtainedusing known amounts of calibration standards or a syntheticblend.4. Significance and Use4.1 In
11、 hydrocarbon type analyses of gasolines, highly vola-tile fuels can need to be stabilized by depentanization (TestMethod D2001) prior to analysis. A knowledge of the compo-sition of light hydrocarbons in the overhead from the depen-tanization process is useful in converting analyses of thedepentaniz
12、ed fraction to a total sample basis.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0L on Gas Chromatography Methods.Current edition approved May 1, 2011. Published August 2011. Originallyapp
13、roved in 1965. Last previous edition approved in 2006 as D242706. DOI:10.1520/D2427-06R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Sum
14、mary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Apparatus5.1 ChromatographAny chromatograph having a thermo-stated oven and a detection system of adequate sensitivity maybe used. The detection system m
15、ust have sufficient sensitivityto produce a recorder deflection of at least 5 mm for 0.1 liquidvolume percent of pentene-1 in the sample or synthetic blendbeing analyzed.NOTE 1If the sensitivity of a given system is inadequate, it can beincreased by using a more sensitive recorder or detector, or by
16、 using moresample if the resolution is substantially unaffected.5.2 RecorderA 1 to 10-mV recorder with a full-scaleresponse time of 2 s or less and a noise level no greater than60.3 % of full scale.5.3 Columns:5.3.1 A description of columns and valving arrangementsthat meet the requirements of this
17、method are described inAnnex A1. Persons using other column materials must estab-lish that the column gives results that meet the precisionrequirements of Section 10.5.3.2 Analyzer ColumnThe column system used must becapable of resolving the individual C2to C5paraffins andolefins well enough so that
18、 the individual hydrocarbons listedin Section 1 may be reported. The resolution should be suchthat at the operating conditions selected, the distance from thebase line in the valley between two peaks representing com-pounds reported is not greater than 50 % of the height of thesmaller peak. If an in
19、ternal standard is used, it must becompletely resolved from the other components.5.3.3 Precut ColumnThis column must be capable ofseparating the C5and lighter olefins and paraffins from the C6and heavier olefins and paraffins. The resolution should be suchthat at the operating conditions selected, t
20、he distance from thebase line to the valley between 2-methylbutene-2 and 2,2-dimethylbutane is not greater than 50% of the height of thesmaller peak. If an internal standard is used, it must be elutedwith the C5and lighter materials.6. Reagents and Materials6.1 Compounds for calibration shall be of
21、a purity of notless than 99 mole %. Calibrants should include compounds1.1.5-1.1.16 as listed in Section 1. The concentration ofethylene, ethane, propylene, and propane is generally so low inmost samples that calibration with these materials is unneces-sary (WarningExtremely flammable gas under pres
22、sure.Extremely flammable liquids.) Commercially available certi-fied blends of light hydrocarbons may be used to establishcalibration data where their compositions are applicable. If aninternal standard is used to relate the concentration of lighthydrocarbons to the whole sample it must be included
23、as acalibrant.6.2 Carrier GasA carrier gas appropriate to the type ofdetector used should be employed. Helium or hydrogen can beused with thermal conductivity detector (WarningCompressed gas under high pressure.) (WarningHydrogenis extremely flammable under pressure.) Nitrogen or argon canbe used wi
24、th ionization or gas density detectors (WarningCompressed gas under high pressure).6.3 Liquid PhaseSee Annex A1.6.4 Solid Support, for use in packed column; usuallycrushed firebrick or diatomaceous earth. Mesh size should beappropriate to the system selected from the supplement.7. Preparation of App
25、aratus7.1 Column PreparationThe method used to prepare thecolumn is not critical as long as the finished column producesthe desired separation. Preparation of the packing is notdifficult once the support, partitioning liquid, and loading levelhave been determined. Some stationary phases are suscepti
26、bleto oxidation and must be protected from excessive exposure toair during the evaporation and drying steps. The followinggeneral directions have been found to produce columns ofacceptable characteristics:7.1.1 Weigh out the desired quantity of support, usuallytwice that required to fill the column.
27、7.1.2 Calculate and weigh out the required quantity ofpartitioning agent. Dissolve the partitioning agent in a volumeof chemically inert, low-boiling solvent equal to approximatelytwice the volume of support.7.1.3 Gradually add the support material to the solution withgentle stirring.7.1.4 Slowly ev
28、aporate the solvent while gently agitatingthe mixture until the packing is nearly dry and no free liquid isapparent.7.1.5 Spread the packing in thin layers on a nonabsorbentsurface and air or oven dry as required to remove all traces ofsolvent.7.1.6 Resieve the packing to remove fines and agglomerat
29、esproduced in the impregnation step.7.1.7 Fill the column tubing with packing by plugging oneend with a wad of glass wool and pouring the packing into theother end through a small funnel. Vibrate the tubing continu-ously over its entire length while filling. When the packingceases to flow, tap the c
30、olumn gently on the floor or bench topwhile vibrating is continued.Add packing as necessary until nofurther settling occurs during a 2-min period. Remove a smallamount of packing from the open end, plug with a wad of glasswool, and shape the column to fit the chromatograph.7.1.8 If multiple columns
31、are joined by tubing unions, thedead volume in the union should be filled with columnpacking.7.2 ChromatographMount the column in the chromato-graph and establish the operating conditions required to givethe desired separation (see Annex A1). Allow sufficient timefor the instrument to reach equilibr
32、ium as indicated by a stablerecorder base line. Control the oven temperature so that it isconstant to within 0.5C without thermostat cycling whichcauses an uneven base line. Set the carrier gas flow rate,measured with a soap film meter, so that it is constant to within1 mL/min of the selected value.
33、8. Procedure8.1 CalibrationDetermine the relative area response ofthe compounds to be reported by injecting known quantities ofthe pure compounds or by using synthetic blends of knowncomposition. For those compounds that are normally gases atroom temperature it is advantageous to use commerciallyava
34、ilable certified light hydrocarbon blends. Sample lightD2427 06 (2011)2hydrocarbon blends contained in pressure containers from theliquid phase (WarningExtremely flammable gas under pres-sure.) Blends of those hydrocarbons that are normally liquid atroom temperature are easily prepared by volume wit
35、h sufficientaccuracy to establish relative response factors (WarningExtremely flammable liquids.) If measurement of the C6andheavier material by reverse flow through the detector isintended, an average calibration factor for these heavy mate-rials must be determined. Gasolines that have been depenta
36、-nized by laboratory distillation may be used as calibrants forthis purpose (WarningExtremely flammable.) If use of aninternal standard is contemplated, the internal standard selectedshould be included in the calibration program.8.2 Analysis:8.2.1 Backflush MethodWhen the backflush technique isused,
37、 add a known quantity of internal standard equal to about5 % to the sample. The internal standard can be added on eithera weight or volume basis depending upon the method ofreporting. One method of adding the internal standard that hasbeen found convenient is given in Annex A1. Alternatively,quantit
38、ative results can be obtained by injecting repeatablequantities of the sample and of a known blend, and comparingthe peak areas obtained for the sample with those obtained forthe known concentration of components in the blend.8.2.1.1 Precut ColumnIf a precut column is used, adjustthe valving so that
39、 carrier gas is flowing in the normal directionthrough both the precut and analysis columns. Using a chilledsyringe, charge sufficient sample to ensure a minimum of 10 %recorder deflection for a 0.1 % sample concentration of2-methylbutene-2 at the most sensitive setting of the instru-ment. When all
40、of the C5and lighter hydrocarbons plus internalstandard, if used, have entered the analyzer column, positionthe valves so that backflushing of the precut column isinitiated. The time at which backflushing is commenced iscritical and may have to be determined by trial and error. Ifproperly done, it r
41、esults in the elimination of any interferencefrom low-boiling six-carbon paraffins and produces a chro-matogram that exhibits peaks for C2through C5paraffins andolefins only (Fig. 1). When the last compound has been eluted,remove the chromatogram and proceed as described in 9.1.1.8.2.1.2 Single Colu
42、mnIf a single column is used, it maybe backflushed if an appropriate valving system has beeninstalled. The operations described above are performed exceptthat backflushing is commenced only when all the C5andlighter hydrocarbons and internal standard have been eluted.The purpose of backflushing in t
43、his case is not to improve theseparation, but merely to shorten the total analysis time andavoid passage of higher boiling hydrocarbons through thedetector.8.2.2 Reverse Flow MethodIf reverse flow of the C6andheavier portion through the detector is employed, the additionof an internal standard is un
44、necessary if adequate calibrationhas been performed and the composition of the C6and heavierportion does not differ significantly from that of the depenta-nized gasolines used as calibrants. An internal standard can beused periodically to assure that analytical accuracy is main-tained (Note 2).Adjus
45、t the valving so that carrier gas is flowingthrough the instrument in the normal direction. Charge suffi-cient sample to ensure a minimum of 10 % recorder deflectionfor a 0.1 percent sample concentration of 2-methylbutene-2 atthe highest sensitivity. As soon as the last pentene peak(2-methylbutene-2
46、) has been eluted, position the valving sothat the carrier gas flow is reversed. After the flow hasstabilized, adjust the base line. Attenuate for the C6+ portionas necessary. The run is complete when the recorder returns tothe base line after elution of the C6portion. This part of theColumn:Precut:
47、 SF96-50 silicone fluidAnalyzer: tricresylphosphate plus DC 550 silicone fluid 4.5/1 by wt followed by ethylene glycol in series.FIG. 1 Typical Chromatogram of Light Components in a Catalytic GasolineD2427 06 (2011)3sample will generally emerge as one broad peak with onlyslight indications of any se
48、paration. Proceed as described in9.1.2.NOTE 2All reverse flow determinations, including the C6and heaviercalibration runs should be made in the same carrier gas flow direction. Allsingle-peak determinations and corresponding calibrations will then bemade in the opposite carrier gas flow direction. T
49、he column should be keptfree of high-boiling residues by periodically sweeping with carrier gas forseveral hours in the reverse direction. A level base line will quickly beattained in either flow direction when the column is clean and the systemis free of leaks.9. Calculation9.1 Calculate the percentage of the individual componentsusing the following procedure that applies and report to thenearest 0.1 %.9.1.1 Backflush MethodMeasure the areas of all of thepeaks representing compounds to be reported and that of theinternal standard. Adjust each component pea
