1、Designation: D 5134 98 (Reapproved 2008)1An American National StandardStandard Test Method forDetailed Analysis of Petroleum Naphthas through n-Nonaneby Capillary Gas Chromatography1This standard is issued under the fixed designation D 5134; the number immediately following the designation indicates
2、 the year oforiginal adoption or, in the case 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.1NOTEUpdated sole source of supply footnotes editorially in
3、 May 2008.INTRODUCTIONDespite the many advances in capillary gas chromatography instrumentation and the remarkableresolution achievable, it has proven difficult to standardize a test method for the analysis of a mixtureas complex as petroleum naphtha. Because of the proliferation of numerous, simila
4、r columns and theendless choices of phase thickness, column internal diameter, length, etc., as well as instrumentoperating parameters, many laboratories use similar but not identical methods for the capillary GCanalysis of petroleum naphthas. Even minute differences in column polarity or column ove
5、ntemperature, for example, can change resolution or elution order of components and make theiridentification an individual interpretive process rather than the desirable, objective application ofstandard retention data. To avoid this, stringent column specifications and temperature and flowcondition
6、s have been adopted in this test method to ensure consistent elution order and resolution andreproducible retention times. Strict adherence to the specified conditions is essential to the successfulapplication of this test method.1. Scope1.1 This test method covers the determination of hydrocar-bon
7、components of petroleum naphthas as enumerated in Table1. Components eluting after n-nonane (bp 150.8C) are deter-mined as a single group.1.2 This test method is applicable to olefin-free (0.015 C/gMinimum detectability 5 3 1012g carbon/secondLinearity 1076.2 Sample Introduction SystemManual or auto
8、matic liq-uid syringe sample injection to the splitting injector may beemployed. Devices capable of 0.2 L to 1.0 L injections aresuitable. It should be noted that inadequate splitter design orpoor injection technique, or both, can result in sample frac-tionation. Operating conditions which preclude
9、fractionationshould be determined in accordance with Section 11.6.3 Electronic Data Acquisition SystemAny data acquisi-tion and integration device used for quantitation of theseanalyses must meet or exceed these minimum requirements:6.3.1 Capacity for at least 250 peaks/analysis.6.3.2 Normalized are
10、a percent calculation with responsefactors.6.3.3 Identification of individual components by retentiontime.6.3.4 Noise and spike rejection capability.6.3.5 Sampling rates for fast (1 s) peaks.6.3.6 Positive and negative sloping baseline correction.6.3.7 Peak detection sensitivity for narrow and broad
11、 peaks.6.3.8 Perpendicular drop and tangent skimming as needed.6.4 Capillary ColumnThis test method utilizes a 50-m(0.21-mm inside diameter) fused silica capillary column withbonded (cross-linked) methyl silicone phase and a film thick-ness (df) of 0.5 m. Other columns with these nominaldimensions m
12、ay be suitable. However, all columns must meetthe criteria set out in Section 10 for efficiency, resolution, andpolarity.7. Reagents and Materials7.1 Carrier Gas, helium, 99.99 % pure. (WarningCompressed gas under high pressure.)7.2 Fuel Gas, hydrogen, 99.9 % pure. (WarningExtremely flammable gas un
13、der pressure.)7.3 Make-up Gas, helium or nitrogen, 99.99 % pure.(WarningCompressed gases under higher pressure.)7.4 n-Heptane, 99+ mol %. (WarningFlammable. Harm-ful if inhaled.)7.5 Methane(WarningExtremely flammable gas.)7.6 2-Methylheptane, 99+ mol %. (WarningFlammable.Harmful if inhaled.)7.7 4-Me
14、thylheptane, 99+ mol %. (WarningFlammable.Harmful if inhaled.)7.8 2-Methylpentane, 99+ mol %. (WarningExtremelyflammable. Harmful if inhaled.)7.9 n-Octane, 99+ mol %. (WarningFlammable. Harm-ful if inhaled.)7.10 Toluene, 99+ mol %. (WarningFlammable. Vaporharmful.)7.11 2,3,3-Trimethylpentane, 99+ mo
15、l %. (WarningExtremely flammable. Harmful if inhaled.)7.12 Column Evaluation Mixture, a qualitative syntheticmixture of pure liquid hydrocarbons with the following ap-proximate composition: 0.5 % toluene, 1 % n-heptane, 1 %2,3,3-trimethylpentane, 1 % 2-methylheptane, 1 %4-methylheptane, 1 % n-octane
16、 in 2-methylpentane solvent.7.13 Reference Alkylate,3actual refinery alkylation productused to prepare Fig. 1.(WarningExtremely flammable.Harmful if inhaled.)7.14 Reference Naphtha,3actual refinery stream used toprepare Fig. 2.(WarningExtremely flammable. Harmful ifinhaled.)7.15 Reference Reformate,
17、3actual refinery reformer prod-uct used to prepare Fig. 3.(WarningExtremely flammable.Harmful if inhaled.)8. Sampling8.1 Hydrocarbon liquids (including naphthas) with Reidvapor pressures of 110 kPa (16 psi) or less may be sampledeither into a floating piston cylinder or into an open container.8.1.1
18、Cylinder SamplingRefer to Test Method D 3700 forinstructions on transferring a representative sample of a hydro-carbon fluid from a source into a floating piston cylinder. Addinert gas to the ballast side of the floating piston cylinder toachieve a pressure of 350 kPa (45 psi) above the vapor pressu
19、reof the sample.8.1.2 Open Container SamplingRefer to Practice D 4057for instructions on manual sampling from bulk storage intoopen containers. Stopper container immediately after drawingsample.8.2 Preserve the sample by cooling to approximately 4Cand by maintaining that temperature until immediatel
20、y prior toanalysis.8.3 Transfer an aliquot of the cooled sample into a pre-cooled septum vial, then seal appropriately. Obtain the testspecimen for analysis directly from the sealed septum vial, foreither manual or automatic syringe injection.9. Preparation of Apparatus9.1 Install and condition colu
21、mn as per manufacturers orsuppliers instructions. After conditioning, attach column out-let to flame ionization detector inlet and check for leaksthroughout the system. If leaks are found, tighten or replacefittings before proceeding.9.2 Calibrate the gas chromatograph column oven tempera-ture senso
22、rs using an independent, electronic temperaturemeasuring device such as a thermocouple or platinum resis-tance temperature detector.9.2.1 Place the independent temperature measuring probe inthe oven in the region occupied by the column. Do not allowsensor to touch the walls of the oven.3The sole sou
23、rce of supply of these qualitative reference samples known to thecommittee at this time is Supelco, Inc., Bellefonte, PA. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of ther
24、esponsible technical committee,1which you may attend.D 5134 98 (2008)149.2.2 Set the oven temperature to 35C and allow oven toequilibrate for at least 15 min, then observe the temperaturereading.9.2.3 If the reading of the independent temperature sensor ismore than 0.5C different from 35C, follow ma
25、nufacturersinstructions to adjust calibration of GC oven temperature.NOTE 1Differences of as little as 1C can change the resolution oftwo closely eluting peaks (of dissimilar hydrocarbon types) enough toaffect integration and quantitation while 2 to 3C may cause those samepeaks to be unresolved or e
26、ven reverse their elution order.9.3 Adjust the operating conditions of the gas chromato-graph to conform to the list in Table 2. Turn on the detector,ignite flame, and allow the system to equilibrate.9.4 Set carrier gas flow rate such that the retention time oftoluene at 35C is 29.6 6 0.2 min.9.4.1
27、As a matter of practicality, it may be easier to first setan approximately correct flow rate, using methane gas injec-tions. To do this, adjust the carrier gas flow (or column headpressure) until the retention time of methane on the 50-mcolumn is 3.6 min.FIG. 1 Reference Alkylate ChromatogramD 5134
28、98 (2008)159.4.2 Make final adjustments to flow rate so that toluene isretained for the specified 29.6 6 0.2 min. As this specificationis critical to achieving reproducibility of retention times amongdifferent laboratories, care must be taken that the toluene doesnot overload the column and cause sk
29、ewed peaks with resultantshifts in peak apex position. Injection of a 1 % toluene solutionshould preclude this possibility.10. Column Evaluation10.1 In order to establish that a column will perform therequired separation, certain specifications must be met withrespect to efficiency, resolution, and
30、polarity. Determine thefollowing data for new columns. Check older columns on aperiodic basis to ensure that column deterioration has notoccurred.Acolumn which does not meet these specifications isunsuitable for use.10.2 Set oven temperature parameters for isothermal opera-tion. Under isothermal con
31、ditions at 35C, inject ;25 L ofmethane and record the retention time. Also at 35C, analyzethe column evaluation mixture described in 7.12. Record theretention times and the peak widths at half height of each of thecomponents.10.2.1 Calculate efficiency of the column using Eq 1. Thenumber of theoreti
32、cal plates (n) must be greater than 225 000.n 5 5.545 tR/Wh!2(1)FIG. 2 Reference Naphtha ChromatogramD 5134 98 (2008)16where:n = number of theoretical plates,tR= retention time of n-octane, andWh= peak width of n-octane at half height (in same unitas retention time).10.2.2 Calculate resolution (R) b
33、etween 2-methylheptaneand 4-methylheptane using Eq 2. R must be at least 1.35.R 52tRA!2 tRB!1.699 WhA!1 WhB!(2)FIG. 3 Reference Reformate ChromatogramD 5134 98 (2008)17where:R = resolution,tR(A)= retention time of 4-methylheptane,tR(B)= retention time of 2-methylheptane,Wh(A)= peak width at half-hei
34、ght of 4-methylheptane,andWh(B)= peak width at half-height of 2-methylheptane10.2.3 Determine relative polarity of the column using thedifference in Kovats Retention Indices (see Annex A1)oftoluene and 2,3,3-trimethylpentane. The relative polarity of thecolumn I(2.3,3-TMP)- I(Toluene)must be 0.4 6 0
35、.4 at 35C.NOTE 2This specification is critical. Seemingly slight differences inthe polarity have a significant effect on the relative order of elution ofcomponents, thus making peak identifications difficult.10.2.3.1 Kovats Retention Index is given by:IA5 700 1 100Flog t8RA!2 log t8RC7!log t8RC8!2 l
36、og t8RC7!G(3)where:IA= retention index of component eluting betweenn C7and n C8,t8R(A)= adjusted retention time of component,t8R(C7)= adjusted retention time of n-heptane, andt8R(C8)= adjusted retention time of n-octane.10.2.3.2 Adjusted retention time of a peak is determined bysubtracting the reten
37、tion time of an unretained substance(methane) from the retention time of the peak.10.2.3.3 If 2,3,3-trimethylpentane and toluene are not re-solved, run separate mixtures, each containing only one ofthese compounds along with n-C7and n-C8in 2-methylpentanesolvent.11. Split Injection Linearity11.1 The
38、 choice of split ratio used is dependent upon thesplit linearity characteristics of the particular injector and thesample capacity of the column. Overloading of the columnmay cause loss of resolution for some components and, sinceoverloaded peaks are skewed, variance in retention times. Thiscan lead
39、 to erroneous component identification. During columnevaluations and split linearity studies, watch for any skewedpeaks that may indicate overload. Note the component size andwhere possible, avoid conditions leading to this problemduring actual analyses.11.2 Splitting injector linearity should be es
40、tablished todetermine proper quantitative parameters and limits. Use astandard mixture of known weight percentages of 10 to 20 pure(99 + %) hydrocarbons, covering the boiling range of this testmethod. To prevent losses due to volatility, do not use anycompounds lighter than n-hexane.11.3 Inject and
41、integrate this standard under the followingconditions, using the operating conditions listed in Table 2.Split ratio may be determined by direct flow measurements orby calculation as shown in Annex A2. Faster temperatureprogramming may be used as long as the components areeluted as discrete peaks.Inj
42、ection Temperature: 200C. Split: 100:1 Sample: 0.2, 0.5, 1.0 LSplit: 200:1 Sample: 0.2, 0.5, 1.0 LInjection Temperature: 250C. Split: 100:1 Sample: 0.2, 0.5, 1.0 LSplit: 200:1 Sample: 0.2, 0.5, 1.0 L11.4 Calculate the concentration of each compound in themixture by area normalization with response f
43、actors. Use aresponse factor of 1.00 for all compounds except benzene(0.90) and toluene (0.95). Determine the relative error of thecalculated concentrations from the known concentrations.% relative error (4)5100 3 calculated concentration 2 known concentration!known concentration11.5 Use only those
44、combinations of conditions from 11.3which result in 3 % or less relative error. This is the splitterlinearity range.12. Procedure for Gas Chromatographic Analysis ofSample12.1 Set the instrument operating variables to within thelimits specified in Table 2. If necessary, change split ratio,sample siz
45、e, or injection port temperature, or combinationthereof, to ensure splitter linearity as determined in Section 11.12.2 Verify that the isothermal retention time of toluene (at35C) is 29.6 6 0.2 min as discussed in 9.4.12.3 Set the recorder or integration device, or both, foraccurate presentation of
46、the data. Set up instrument sensitivitysuch that any component of at least 0.05 % mass will bedetected, integrated, and reported.12.4 Inject 0.2 to 1.0 L of sample into the injection portand start the analysis. Sample size must be consistent with thesplitter linearity range as determined in Section
47、11. Obtain achromatogram and peak integration report.NOTE 3Petroleum naphtha samples may contain appreciable quanti-ties of highly volatile components. Samples should be chilled in theiroriginal container to 4C (39F) before opening for subsampling ortransfer (see Section 8).13. Calculation13.1 Ident
48、ify each peak by visually matching it with itscounterpart in the appropriate standard chromatogram, Fig. 1,TABLE 2 Operating ConditionsColumn Temperature ProgramInitial temperature: 35C 6 0.5CPre-injection equilibration time: 5 minInitial hold time: 30 minProgram rate: 2C/minFinal temperature: 200CF
49、inal hold time: 10 minInjectorTemperature: 200CSplit ratio: 200:1Sample size: 0.2 to 1.0 LDetectorType: flame ionizationTemperature: 250CFuel gas: hydrogen (;30 mL/min)Oxidizing gas: air (;250 mL/min)Make-up gas: nitrogen (;30 mL/min)Carrier GasType: heliumAverage linear velocity: ;23 cm/s 35C (see 9.4)D 5134 98 (2008)18Fig. 2,orFig. 3. Make allowances for differences in relativepeak sizes with different samples. Peaks eluting after n-nonaneare not identified individually.NOTE 4To aid the anal
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