1、Designation: D7900 13Designation: 601Standard Test Method forDetermination of Light Hydrocarbons in Stabilized CrudeOils by Gas Chromatography1,2This standard is issued under the fixed designation D7900; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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.1. Scope1.1 This test method specifies a method to determine theboiling range distribution of hyd
3、rocarbons in stabilized crudeoil up to and including n-nonane. A stabilized crude oil isdefined as having a Reid Vapor Pressure equivalent to or lessthan 82.7 kPa. The results of this test method can be combinedwith those from Test Method D7169 and IP 545 to give a fullboiling point distribution of
4、a crude oil. See Test MethodD7169 (IP 545) for merging of these results to give a full crudeanalysis.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are provided forinformation purposes only.1.3 This standard does not purport to address all of the
5、safety 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D323 Test Method for Vapor P
6、ressure of Petroleum Products(Reid Method)D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD5134 Test Method for Detailed Analysis of PetroleumNaphthas through n-Nonane by Capillary Gas Chroma-tographyD6729 T
7、est Method for Determination of Individual Com-ponents in Spark Ignition Engine Fuels by 100 MetreCapillary High Resolution Gas ChromatographyD6730 Test Method for Determination of Individual Com-ponents in Spark Ignition Engine Fuels by 100MetreCapillary (with Precolumn) High-Resolution Gas Chro-ma
8、tographyD6733 Test Method for Determination of Individual Com-ponents in Spark Ignition Engine Fuels by 50-MetreCapillary High Resolution Gas ChromatographyD7169 Test Method for Boiling Point Distribution ofSamples with Residues Such as Crude Oils and Atmo-spheric and Vacuum Residues by High Tempera
9、ture GasChromatographyE355 Practice for Gas Chromatography Terms and Relation-ships2.2 Energy Institute Standards:4IP 545 Crude Petroleum and Petroleum ProductsDetermination of Boiling Range Distribution of Crude OilIP 475 Manual SamplingIP 476 Automatic Pipeline Sampling2.3 ISO Standard:5ISO 4259 P
10、etroleum ProductsDetermination and Applica-tion of Precision Data in Relation to Methods of Test3. Terminology3.1 DefinitionsThis test method makes reference to manycommon gas chromatographic procedures, terms, and relation-ships. Detailed definitions can be found in Practice E355.4. Summary of Test
11、 Method4.1 An amount of internal standard is quantitatively addedto an aliquot of the stabilized crude oil. A portion of thismixture is injected into a pre-column in series via a splitter1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubrica
12、nts and is the direct responsibility ofSubcommittee D02.04.0L on Gas Chromatography Methods.Current edition approved Dec. 1, 2013. Published January 2014. DOI: 10.1520/D7900-13.2This standard has been developed through the cooperative effort betweenASTM and the Energy Institute, London. The IP and A
13、STM logos imply that theASTM and IP standards are technically equivalent, but their use does not imply thatboth standards are editorially identical.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandar
14、ds volume information, refer to the standards Document Summary page onthe ASTM website.4Information on Energy Institute Standards can be obtained from the EnergyInstitute at www.energyinst.org.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036,
15、 http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1with a capillary analytical column. When the n-nonane hasquantitatively passed to the analytical column, the pre-columnis back-flushed to vent the higher boiling comp
16、onents. Theindividual components are identified by comparison withreference chromatograms and a database of hydrocarbon com-pounds (see Appendix X1). The boiling point distribution up toand including n-nonane (n-C9) is calculated.5. Significance and Use5.1 Knowledge of the boiling point distribution
17、 of stabilizedcrude oils is important for the marketing, scheduling, andprocessing of crude oil in the petroleum industry. Test MethodD7169 and IP 545 purport to give such a distribution in crudeoils, but are susceptible to significant errors in the light endsportion of the distribution as well as i
18、n the mass recovery of thewhole crude oil due to the interference imposed by the diluentsolvent. This test method allows for more accurate determina-tion of the front end of the boiling point distribution curve, inaddition to providing important C1 to C9 (nonane) componentlevel information, and more
19、 accurate mass recovery at C9(nonane).6. Apparatus6.1 Gas Chromatograph, with the operational characteris-tics given in Table 1.6.2 InletA temperature programmable vaporizing (PVT)or split/splitless inlet.6.2.1 Carrier Gas Pneumatic ControlConstant carrier gaspressure or flow control is required.6.3
20、 ColumnA fused silica bonded polydimethylsiloxanecoated capillary column and pre-column are employed. SeeTable 1 for suggested columns. The analytical column shallelute hydrocarbons in a boiling point order. The eluate from theinjector passes through the pre-column before eluting onto theanalytical
21、column.6.4 Data SystemA computer based chromatography datasystem capable of accurately and repeatedly measuring theretention time and areas of eluting peaks. The system shall beable to acquire data at a rate adequate to accurately measure 10to 20 points around an individual peak. For the accelerated
22、methods (see Table 1), a sampling rate of at least 20 Hz isrecommended.6.5 Sample IntroductionSample introduction by means ofan automatic injection is highly recommended.6.6 Flame Ionization Detector (FID), with sufficient sensi-tivity to detect 0.01 % mass n-heptane with a signal to noise ofgreater
23、 than five. When operating at this sensitivity level,detector stability shall be such that a baseline drift of not morethan 1 % per hour is obtained. The detector shall be connectedto the column so as to avoid any cold spots. The detector shallbe capable of operating at a temperature equivalent to t
24、hemaximum column temperature used.6.7 Pre-Column Configurations:6.7.1 Heated Valve Switching Box ConfigurationFor theisothermal 1-m pre-column, a heated valve box is needed withits own temperature control. The box will contain an automatedsix-port valve, which is used to back-flush the pre-column. T
25、hesix-port valve should be made out of material that will not becorroded by the sample (some crude oils contain high amountsof sulfur components). The valve shall be situated in a heatedisothermal oven and be attached to the injector, pre-column,splitter, analytical column, and the detector without
26、any coldspots. An example configuration is given in Fig. X2.1 inAppendix X2. Alternatively, a Dean Switch type back-flush ofthe petroleum may also be employed in place of a rotary valve.6.7.2 Injection Port Back-Flush ConfigurationA tempera-ture programmable injection port capable of containing a 7.
27、5cm pre-column, and this injection port must be equipped witha back-flush option. This injector can be connected directly toTABLE 1 Typical Chromatographic ConditionsPre-column Pre-column Analytical AcceleratedA B AnalyticalColumn Lengthmetres 1.0 m 0.075 m 50 or 100 m 40 mColumn Internal Diametermm
28、 2 mm 2.5 mm 0.25 mm 0.10 mmPhase Loading 5 % 10 %Film Thickness 0.5 umInjection Volume 0.1 L 0.1 LInjector Split Ratio 100 : 1 600 : 1Injector Temperature 300C 100CPre-column Temperature 200C 100CInjector Prog. Rate C/min 50C/minFinal Injector Temperature 300CInitial Oven Temperature 35C 35CHold Ti
29、me 30 min 2.6 minOven Program Rate C/min 2C/min 50C/min 45C(hold time 3 min)5C/min 60C(hold time 3 min)9.5C/min Final Oven Temperature 200C (hold time 20 min) 200C (hold time 1 min)Flame Ionization Detector 300C 300CD7900 132the capillary column (Fig. X2.2, Appendix X2) or via a splitter(Fig. X2.3,
30、Appendix X2).6.8 Analytical Balance, capable of weighing with an accu-racy of 0.1 mg.7. Reagents and Materials7.1 Gas Chromatograph GasesAll of the following gasesshall have a purity of 99.995 % (V/V) or greater. (WarningGases are compressed. Some are flammable, and all gases areunder high pressure.
31、)NOTE 1These specifications can be obtained by proper use of filteringdevices and meeting the FID specifications in 6.6.7.1.1 Carrier GasHelium or hydrogen is required. Anyoxygen present shall be removed, for example, by a suitablechemical filter. If hydrogen is employed as a carrier gas, theuser is
32、 advised to follow all manufacturers safety guidelinesfor its use. (WarningHydrogen is an extremely flammablegas under high pressure.)7.1.2 Detector Combustion Gases, Air, Hydrogen, andMake-up Gas (Helium or Nitrogen). (WarningHydrogen isan extremely flammable gas under high pressure.) (WarningCompr
33、essed air is a gas under high pressure and supportscombustion.)7.2 Internal StandardThe internal standard shall havebaseline resolution from any adjacent eluting peaks. Hexene-1or 3,3dimethylbutene-1 (99 % pure) have been found to besuitable.7.3 Valve Timing Mixture/Splitter Linearity MixA quanti-ta
34、tive mixture of approximately 1 % mass of each normalalkane from pentane to decane in hexadecane (99+ % purity).Accurately record the mass (g) of each normal alkane as wellas the hexadecane solvent and calculate the actual mass percentof each alkane in the mixture.7.4 Viscosity Agent, Carbon disulfi
35、de, 99+ % pure,(WarningExtremely flammable and toxic liquid) is used asa viscosity reduction agent in the preparation of samples.8. Sampling8.1 Samples to be analyzed by this test method must beobtained using the procedures outlined in Practice D4057 orPractice D4177 (IP 475 and IP 476, respectively
36、).8.2 The test specimen to be analyzed must be homogeneousand free of dust or undissolved material.9. Preparation of Apparatus9.1 ChromatographPlace in service according to manu-facturers instructions. Typical operating conditions are givenin Table 1.9.2 Column PreparationCondition analytical column
37、s inaccordance with manufacturers instructions.9.3 System Performance Specification:9.3.1 SkewnessDetermine the skew of the n-hexane peakby measuring the width of the leading part of the peak at 5 %peak height (A) and the width of the following part of the peakat 5 % peak height (B). The ratio (B)/(
38、A) shall be not less than1 or more than 4 (see Fig. 1).9.3.2 Column ResolutionDetermine the resolution be-tween the internal standard and the nearest n-paraffin peak.R 5 2 3 t2 2 t1! 1.699w11 w2! (1)where:R = the column resolution,t1 = the retention time of the first peak (peak 1),t2 = the retention
39、 time of the second peak (peak 2),w1 = the peak width at half height of peak 1, andw2 = the peak width at half height of peak 2.For example, if Hexene-1 is used as the internal standard, theresolution is determined between Hexene-1 and n-hexane. Theresolution shall be at least 2.0.9.3.3 Detector Res
40、ponse Factor CalculationsCalculatethe flame ionization detector response factor relative tomethane, which is considered to have a response factor of unity(1), for each hydrocarbon group type of a particular carbonnumber using Eq 2.RRf 5 Caw3 Cn!1Haw3 Hn! 30.7487# Caw3 Cn! (2)where:FIG. 1 Calculation
41、 of Peak Skewness (See 9.3.1)FIG. 2 Determination of Resolution (See 9.3.2)D7900 133RRf = relative response factor for a hydrocarbon typegroup of a particular carbon number,Caw= atomic mass of carbon, 12.011,Cn= number of carbon atoms in the hydrocarbon typegroup, of a particular carbon number,Haw=
42、atomic mass of hydrogen, 1.008,Hn= number of hydrogen atoms in the hydrocarbon typegroup of a particular carbon number, and0.7487 = factor to normalize the result to a methane re-sponse of unity, (1).9.3.4 Determination of Back-Flush TimeWith the pre-column and analytical column in series, inject an
43、 aliquot of thepre-column switch test mixture (7.3) and determine the ratio ofthe alkanes.9.3.4.1 Non-Accelerated Analytical ColumnSet theswitching time to one minute and repeat the analysis. Increaseor decrease the valve time to ensure the complete recovery ofthe highest alkane required (for exampl
44、e, n-nonane) and partialrecovery of the next alkane (for example, decane). (Seeexample chromatogram (Fig. 3).)9.3.4.2 Accelerated Analytical ColumnSet the switchingtime to 30 s and repeat the analysis. Increase or decrease thevalve time to ensure the recovery of the highest alkane required(for examp
45、le, n-nonane) and partial recovery of the next alkane(for example, n-decane). (See example chromatogram (Fig. 3).)9.3.5 Split Injection LinearityFor systems utilizing splitinjection, injector linearity must be established to determineproper quantitative parameters and limits.9.3.5.1 Set the injector
46、 temperature and split ratio to theoperating values as indicated in Table 1 for split inlets.9.3.5.2 Inject 0.1 L of the splitter linearity mixture (7.3)into the system.9.3.5.3 Calculate the normalized area % of the n-C5 throughn-C9 paraffins using Eq 3:FIG. 3 Example Chromatogram Showing Elution on
47、 n-Nonane and n-Decane for Determining Back-Flush Time (See 9.3.4)D7900 134Corrected Normalized Area % Cn5100 3 Area Cn3 RRf Cn! TA# (3)where:Area Cn= integrated peak area of normal alkane Cn,RRf Cn= theoretical relative response factor for Cn(Eq 2),andTA = sum of RRf corrected peak areas from C5to
48、C9.9.3.5.4 The corrected normalized area percent of eachnormal alkane must agree within 10 % or better from theirgravimetric values after the back-flush time is optimized.Values outside of this range may indicate possible massdiscrimination, possibly due to liner issues, blockage of thesplit vent, a
49、n inlet leak, incorrect detector Air/H2 ratio,weathering of the gravimetric mixture, or premature back-flushtime. Correct any issues and perform the linearity check untilit passes the specification.10. Procedure10.1 Set the operating conditions of the gas chromatographas shown in Table 1.10.2 Obtain a representative sample following the guide-lines of Practice D4057 and any other applicable guidelines.Take precautions to minimize the loss of light ends fromvolatile samples.10.3 Sample PreparationWeigh t
