1、Designation: D 7423 09Standard Test Method forDetermination of Oxygenates in C2, C3, C4, and C5Hydrocarbon Matrices by Gas Chromatography and FlameIonization Detection1This standard is issued under the fixed designation D 7423; the number immediately following the designation indicates the year ofor
2、iginal 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.1. Scope1.1 This test method covers the gas chromatographic pro-cedure fo
3、r the quantitative determination of organic oxygenatesin C2, C3, C4, and C5 matrices by multidimensional gaschromatography and flame ionization detection. This testmethod is applicable when the hydrocarbon matrices have afinal boiling point not greater than 200C. Oxygenate com-pounds include, but ar
4、e not limited to, those listed in Table 1.The linear working range for oxygenates is 0.50 mg/kg to 100mg/kg.1.2 This test method is intended to determine the massconcentration of each oxygenate in the hydrocarbon matrix.Oxygenate compound identification is determined by referencestandards and column
5、 elution retention order.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 s
6、tandard 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:2D 1265 Practice for Sampling Liquefied Petroleum (LP)Gases, Manual MethodD 1835 Specification for Liquefied Petroleum (LP)
7、GasesD 4175 Terminology Relating to Petroleum, PetroleumProducts, and LubricantsD 6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD 6849 Practice for Storage and Use of Liquefied Petro-leum Gases (LPG) in Sam
8、ple Cylinders for LPG TestMethodsE 355 Practice for Gas Chromatography Terms and Rela-tionships3. Terminology3.1 Additional terminology related to the practice of gaschromatography can be found in Practice E 355.3.2 Definitions:3.2.1 liquefied petroleum gas (LPG), na mixture of nor-mally gaseous hyd
9、rocarbons, predominantly propane or bu-tane, or both, that has been liquefied by compression orcooling, or both, to facilitate storage, transport, and handling.D 41753.2.2 oxygenate, nan oxygen-containing ashless organiccompound, such as an alcohol or ether, which may be used asa fuel or fuel supple
10、ment. D 41753.3 Definitions of Terms Specific to This Standard:3.3.1 Deans switching methodrepresentative aliquot ofsample is injected on-column using a sample valve (or via a gaschromatograph split inlet). The sample passes onto a nonpolarcolumn, which elutes the lighter hydrocarbons in boiling poi
11、ntorder to the analytical column and backflushes the heavierhydrocarbons to vent. The oxygenate compounds elute fromthe analytical column and are detected via a flame ionizationdetector.3.3.2 Deans switching method direct injectgas chromato-graphic valve configuration equipped with a valve connected
12、directly to the precolumn. This technique is commonly used forthe determination of oxygenates in ethene and propene con-centrates. This configuration provides the lowest detectionlimits such as those commonly required for ethene and propeneconcentrates.3.3.3 Deans switching method equipped with a sp
13、lit inletgas chromatographic valve configuration equipped with a gaschromatograph split inlet for sample introduction into theprecolumn. This configuration is commonly used for thedetermination of oxygenates in C5 hydrocarbon mixtures. Thistechnique using this configuration might not provide thedete
14、ction limits noted in the scope of this test method. If lower1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.D0.04 on C4 Hydrocarbons.Current edition approved July 1, 2009. Published September 2
15、009.2For 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 Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO
16、Box C700, West Conshohocken, PA 19428-2959, United States.detection limits are required, then the user should considerusing the on-column valve direct injection technique.3.3.4 valve cut methodcommonly used for the determina-tion of oxygenates in C4 hydrocarbon mixtures. This techniqueusing a split
17、inlet might not provide the detection limits notedin the scope of this test method. If lower detection limits arerequired, then the user should consider using the on-columnvalve direct injection technique.3.3.5 valve cut method equipped with a split inletrepresentative aliquot of sample is injected
18、via a gas chromato-graph split inlet for sample introduction into the precolumn.The sample passes onto a nonpolar column, which elutes thelighter hydrocarbons in boiling point order to the analyticalcolumn and the heavier hydrocarbons to vent. The oxygenatecompounds elute from the analytical column
19、and are detectedvia a flame ionization detector.3.4 Acronyms:3.4.1 DIPEdiisopropylether.3.4.2 ETBEethyl tert-butylether.3.4.3 MEK2-butanone.3.4.4 MTBEmethyl tert-butylether.3.4.5 TAMEtert-amyl methylether.3.4.6 PLOTporous layer open tubular capillary column.3.4.7 WCOTwall coated open tubular capilla
20、ry column.4. Summary of Test Method4.1 This test method shall be configured using either theDeans switching method or the valve cut method. Eachmethod shall be configured using an on-column valve directinject technique or a gas chromatograph split inlet. Theon-column valve direct inject technique is
21、 configured byconnecting the head of the precolumn directly to the injectionvalve.4.2 The detector response and retention times for eachoxygenate peak in a calibration standard is measured and usedto externally calibrate the flame ionization detector response.The concentration of each oxygenate is c
22、alculated by theexternal standard technique. Calibration materials are listed inTable 1.5. Significance and Use5.1 The determination of oxygenates is important in themanufacture of ethene, propene, 1-3 butadiene, C4 hydrocar-bons, and C5 hydrocarbons. Alcohols, ethers, aldehydes, andketones are trac
23、e impurities in these hydrocarbons. Oxygenatesdecrease catalyst activity in downstream polymerization pro-cesses.6. Apparatus6.1 Gas ChromatographAny gas chromatographequipped with a flame ionization detector (FID) and havingsensitivity of 0.01 mg/kg. The gas chromatograph must becapable of linear t
24、emperature control from 50 to 320C for thecapillary column oven. The gas chromatograph must be ca-pable of controlling multiple valve events. Carrier gas flowcontrollers and or electronic pressure control modules shall becapable of precise control where the required flow rates are low(see Table 2).
25、Pressure control devices and gages shall becapable of precise control for the typical pressures required.The temperature program rate must repeat to within 0.1C andprovide retention time repeatability of 0.05 min throughout thetemperature program.6.2 Carrier Gas Preparation:6.2.1 Moisture present in
26、 the carrier gas causes chromato-graphic problems. The oxygenates column has very highretention. Due to this characteristic, moisture and trace impu-rities in the carrier gas are trapped at the beginning of thiscolumn. Therefore carrier gas filters or the use of any devicewhich can be used to elimin
27、ate trace levels of oxygen andwater are strongly recommended. Additionally, frequent recon-ditioning and longer than usual column condition times may benecessary to maintain the performance of this column for themost accurate results from this test method.6.2.2 Carrier Gas FiltersOxygen and molecula
28、r sievetype moisture filters.6.3 Columns:6.3.1 Nonpolar (Precolumn) ColumnThis column per-forms a pre-separation of the light hydrocarbon fraction up toTABLE 1 Oxygenates and Typical Retention TimesComponents Retention Time (min)Dimethyl ether 6.18Diethyl ether 8.44Acetaldehyde 8.89Ethyl tert-butyl
29、ether 10.66Methyl tert-butyl ether (MTBE) 10.92Diisopropyl ether 11.22Propionaldehyde (Propanal) 12.00Tertiary amyl methyl ether (TAME) 13.19Propyl ether 14.00Isobutylaldehyde 14.10Butylaldehyde 14.50Methanol 14.91Acetone 15.39Isovaleraldehyde 16.00Valeraldehyde 16.102-Butanone (MEK) 17.14Ethanol 17
30、.51N-propyl alcohol and isopropanol 19.20 (co-elution)Allyl Alcohol 20.00Isobutanol, Tert-butyl alcohol, Sec-Butanol 20.24 (co-elution)N-butanol 20.84D7423092and including TAME. Any column with equivalent or betterchromatographic efficiency and selectivity to that described in6.3.2 can be used.6.3.2
31、 WCOT Methyl Silicone Column, 25 m long by 0.53mm inside diameter fused silica WCOT column with a 1.0 mfilm thickness of crosslinked methyl siloxane. A column of thisdescription was used in the repeatability study referred to inSection 16.6.4 Polar (Analytical) ColumnThis column performs aseparation
32、 of the oxygenates from volatile hydrocarbons in thesame boiling point range. The oxygenates and remaininghydrocarbons are backflushed to vent through the nonpolarcolumn. Any column with equivalent or better chromato-graphic efficiency and selectivity to that described in 6.4.1 canbe used.6.4.1 Oxyg
33、enates PLOT column, 10 m long by 0.53 mminside diameter, with a stationary phase composed of a bariumsulfate adsorbent mixture, coated onto a fused silica column.Ata minimum the column should have sufficient retention formethanol that it elute after n-tridecane (RI 1300) and musthave sufficient effi
34、ciency and capacity to resolve the oxygen-ates listed in Table 1 to provide accurate quantitative resultsequivalent to those shown in Section 16. A column of thisdescription was used in the repeatability study referred to inSection 16.6.5 Sample Introduction:6.5.1 Switching ValveA valve with an oper
35、ating tempera-ture of 225C and operating pressure of 27.57 bar, to be locatedwithin a heated enclosure or in the main oven. The valve shallbe of low volume design and not contribute significantly tochromatographic deterioration.6.5.2 Liquid Sampling ValveA valve with an operatingtemperature of 75C a
36、nd operating pressure of 68.94 bar, to belocated outside of the oven and used in sampling propaneconcentrates, butane samples or other LPG samples. Therepeatability of this test is dependent upon a consistent cylinderpressure. It is strongly suggested that the use of a floatingpiston cylinder be use
37、d and that the sample be pressurized to13.78 bar above the vapor pressure of the sample prior tosampling.6.5.3 Low Pressure Liquid SamplingA valve syringeadapter may be used to sample low vapor pressure liquids suchas C5 concentrates.6.5.4 Low Pressure Gas Sampling ValveA valve with anoperating temp
38、erature of 225C and operating pressure of27.57 bar to be placed in a heated enclosure maintained atapproximately 150C and used to sample ethene vapor. Anexternal sample loop is installed on this valve. A 1000 Lsample loop has been used successfully. The sample loopsample size shall be sized experime
39、ntally to provide desireddetection limits. This valve must reproduce to within 5 percentrelative standard deviation on each component.6.5.5 Heated Valve EnclosureAny enclosure capable ofmaintaining the valve and sample loop at 150C.6.5.6 Connecting TeesAny tees that can provide an inertconnection.6.
40、5.7 TubingAny tubing capable of providing an inertconnection.6.5.8 Needle ValveMicrometering valve capable of lowflow control 2 to 90 mL/min.6.6 Data AcquisitionAny computerized data acquisitionsystem shall be used for peak area integration and graphicpresentation of the chromatogram. Alternatively
41、any integratorsystem can also be used for chromatographic peak areaintegration.7. Reagents and Materials7.1 Purity of ReagentsBefore preparing the calibrationstandards, determine the purity of the oxygenate stocks andmake corrections for the impurities found. Whenever possible,use stocks of 98% puri
42、ty or better. The calibration materials arelisted in Table 1.7.2 Calibration Standard MixtureAstandard mixture con-taining known concentrations of each oxygenate listed in TableTABLE 2 Chromatographic Operating ConditionsParameter Deans Switch (Fig. 1) Deans Switch (Fig. 2) Valve Cut (Fig. 3)Valve 1
43、C Ambient Ambient AmbientValve 1 Sample Size, L 2 2 2Valve 2C 150 150 150Valve 2 Sample Size, L - mL 500 2 500 2 500 2Injector, C Not Applicable 250 250Split Ratio Not Applicable 1:1 - xA1:1 - xABackflush, min 2.0 4.0 2.0 4.0 2.0 4.0Column Oven Standby, C 200 200 200Initial Column Oven, C 50 50 50In
44、itial Hold, min 5 5 5Rate, C/min 10 10 10Final Column Oven, C 240 240 220Final Hold, min 5 5 5Precolumn Flow, mL/min 5 5 5Analytical Column Flow, mL/min 7 7 7Needle Valve 1 Flow, mL/min 15 15 Not ApplicableNeedle Valve 2 Flow, mL/min 6 6 Not ApplicableDetector, C 300 300 300Detector RangeBBBASplit r
45、atio shall be experimentally determined using appropriate gravimetric standards to obtain the desired minimum detection requirements.BDetector RangeAdjust the detector range to a setting which shall provide sufficient voltage to assure the detection of small concentrations of each oxygenate butas to
46、 avoid detector signal saturation.D74230931 should be prepared gravimetrically. This mixture shall beused as an external calibration standard.7.3 Compressed HydrogenLess than 1 mg/kg hydrocar-bon impurities for FID fuel gas.7.4 Compressed HeliumGas purity 99.999 %. Note thathelium supplies often con
47、tain low level amounts of water.Water can dramatically deteriorate the performance of theanalytical column (oxygenates column). It is strongly recom-mended that the use of a molecular sieve or other suitable waterremoval system be implemented to eliminate the possibility ofcontaminating the analytic
48、al column with oxygen or water.7.5 Compressed AirZero grade (gas purity 99.999 %).7.6 Instrument AirCompressed air for pneumatic actua-tion of valves.8. Sampling8.1 Every effort should be made to ensure that the sample isrepresentative of the source from which it is taken. Follow therecommendations
49、of Practice D 1265, D 1835, D 6849 or theirequivalent, when obtaining and storing samples from bulkstorage or pipelines.9. Installation of Carrier Gas Filters9.1 The carrier gas shall require pretreatment with anoxygen and water removal system.9.2 On the gas chromatograph carrier gas supply line, installthe oxygen and water removal filters.Any filters, traps or gettertype device can be used to assure removal of both oxygen andwater from the carrier gas used for this gas chromatograph.10. Preparation of Apparatus a
