1、Designation: D7423 161Standard 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 D7423; the number immediately following the designation indicates the year ofori
2、ginal 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.1NOTETable 3 was corrected editorially in June 2016.1. Scope*1.1 This test
3、 method covers the gas chromatographic pro-cedure for 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 gre
4、ater than 200 C. Oxygenate com-pounds include, but are not limited to, those listed in Table 1.The linear working range for oxygenates is 0.50 mg kg to100 mg kg.1.2 This test method is intended to determine the massconcentration of each oxygenate in the hydrocarbon matrix.Oxygenate compound identifi
5、cation is determined by referencestandards and column 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 i
6、ts 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:2D1265 Practice for Sampling Liquefied Petroleum (LP)Gases, Manual Meth
7、odD1835 Specification for Liquefied Petroleum (LP) GasesD4175 Terminology Relating to Petroleum Products, LiquidFuels, and LubricantsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6300 Practice for Determi
8、nation of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6849 Practice for Storage and Use of Liquefied PetroleumGases (LPG) in Sample Cylinders for LPG Test MethodsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE355 Practice for Gas Chr
9、omatography Terms and Relation-ships3. Terminology3.1 Additional terminology related to the practice of gaschromatography can be found in Practice E355.3.2 Definitions:3.2.1 liquefied petroleum gas (LPG), na mixture of nor-mally gaseous hydrocarbons, predominantly propane orbutane, or both, that has
10、 been liquefied by compression orcooling, or both, to facilitate storage, transport, and handling.D41753.2.2 oxygenate, nan oxygen-containing ashless organiccompound, such as an alcohol or ether, which may be used asa fuel or fuel supplement. D41753.3 Definitions of Terms Specific to This Standard:3
11、.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 pointorder to the analytical column and backflushes the heavierhydr
12、ocarbons 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 connected1This test method is under the jurisdiction of ASTM Committee D0
13、2 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.D0.04 on C4 and C5 Hydrocarbons.Current edition approved Feb. 15, 2016. Published March 2016. Originallyapproved in 2009. Last pervious edition approved in 2014 as D7423 09 (2014).DOI: 10.1520/D7
14、423-16E01.2For 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.*A Summary of Changes section appears at the end of
15、 this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1directly to the precolumn. This technique is commonly used forthe determination of oxygenates in ethene and propene con-centrates. This configuration provides the lowest de
16、tectionlimits such as those commonly required for ethene and propeneconcentrates.3.3.3 Deans switching method equipped with a split inletgas chromatographic valve configuration equipped with a gaschromatograph split inlet for sample introduction into theprecolumn. This configuration is commonly used
17、 for thedetermination of oxygenates in C5 hydrocarbon mixtures. Thistechnique using this configuration might not provide thedetection limits noted in the scope of this test method. If lowerdetection limits are required, then the user should considerusing the on-column valve direct injection techniqu
18、e.3.3.4 valve cut methodcommonly used for the determina-tion of oxygenates in C4 hydrocarbon mixtures. This techniqueusing a split 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-col
19、umnvalve direct injection technique.3.3.5 valve cut method equipped with a split inletrepresentative aliquot of sample is injected 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
20、 point order to the analyticalcolumn and the heavier hydrocarbons to vent. The oxygenatecompounds elute from the analytical column 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-butylet
21、her.3.4.5 TAMEtert-amyl methylether.3.4.6 PLOTporous layer open tubular capillary column.3.4.7 WCOTwall coated open tubular capillary 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 configure
22、d using an on-column valve directinject technique or a gas chromatograph split inlet. Theon-column valve direct inject technique is 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 s
23、tandard is measured and usedto externally calibrate the flame ionization detector response.The concentration of each oxygenate is calculated by theexternal standard technique. Calibration materials are listed inTable 1.5. Significance and Use5.1 The determination of oxygenates is important in theman
24、ufacture of ethene, propene, 1-3 butadiene, C4hydrocarbons, and C5 hydrocarbons. Alcohols, ethers,aldehydes, and ketones are trace impurities in these hydrocar-bons. Oxygenates decrease catalyst activity in downstreampolymerization processes.6. Apparatus6.1 Gas ChromatographAny gas chromatographequi
25、pped with a flame ionization detector (FID) and havingsensitivity of 0.01 mg kg. The gas chromatograph must becapable of linear temperature control from 50 C to 320 C forthe capillary column oven. The gas chromatograph must becapable of controlling multiple valve events. Carrier gas flowcontrollers
26、and or electronic pressure control modules shall becapable of precise control where the required flow rates are low(see Table 2). Pressure control devices and gages shall becapable of precise control for the typical pressures required.The temperature program rate must repeat to within 0.1 C andprovi
27、de retention time repeatability of 0.05 min throughout thetemperature program.TABLE 1 Oxygenates and Typical Retention TimesComponents Retention Time (min)Dimethyl ether 6.18Diethyl ether 8.44Acetaldehyde 8.89Ethyl tert-butyl ether 10.66Methyl tert-butyl ether (MTBE) 10.92Diisopropyl ether 11.22Prop
28、ionaldehyde (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 17.51N-propyl alcohol and isopropanol 19.20 (co-elution)Allyl Alcohol 20.00I
29、sobutanol, Tert-butyl alcohol, Sec-Butanol 20.24 (co-elution)N-butanol 20.84D7423 16126.2 Carrier Gas Preparation:6.2.1 Moisture present in the carrier gas causes chromato-graphic problems. The oxygenates column has very highretention. Due to this characteristic, moisture and trace impu-rities in th
30、e carrier gas are trapped at the beginning of thiscolumn. Therefore carrier gas filters or the use of any devicewhich can be used to eliminate trace levels of oxygen andwater are strongly recommended. Additionally, frequent recon-ditioning and longer than usual column condition times may benecessary
31、 to maintain the performance of this column for themost accurate results from this test method.6.2.2 Carrier Gas FiltersOxygen and molecular sievetype moisture filters.6.3 Columns:6.3.1 Nonpolar (Precolumn) ColumnThis column per-forms a pre-separation of the light hydrocarbon fraction up toand inclu
32、ding TAME. Any column with equivalent or betterchromatographic efficiency and selectivity to that described in6.3.2 can be used.6.3.2 WCOT Methyl Silicone Column, 25 m long by0.53 mm inside diameter fused silica WCOT column with a1.0 m film thickness of crosslinked methyl siloxane. A col-umn of this
33、 description was used in the repeatability studyreferred to in Section 16.6.4 Polar (Analytical) ColumnThis column performs aseparation of the oxygenates from volatile hydrocarbons in thesame boiling point range. The oxygenates and remaininghydrocarbons are backflushed to vent through the nonpolarco
34、lumn. Any column with equivalent or better chromato-graphic efficiency and selectivity to that described in 6.4.1 canbe used.6.4.1 Oxygenates 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
35、 minimum the column should have sufficient retention formethanol that it elute after n-tridecane (RI 1300) and musthave sufficient efficiency 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 thisdes
36、cription was used in the repeatability study referred to inSection 16.6.5 Sample Introduction:6.5.1 Switching ValveA valve with an operating tempera-ture of 225 C and operating pressure of 27.57 bar, to belocated within a heated enclosure or in the main oven. Thevalve shall be of low volume design a
37、nd not contributesignificantly to chromatographic deterioration.6.5.2 Liquid Sampling ValveA valve with an operatingtemperature of 75 C and operating pressure of 68.94 bar, to belocated outside of the oven and used in sampling propaneconcentrates, butane samples or other LPG samples. Therepeatabilit
38、y of this test is dependent upon a consistent cylinderpressure. It is strongly suggested that the use of a floatingpiston cylinder be used 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 m
39、ay be used to sample low vapor pressure liquids suchas C5 concentrates.6.5.4 Low Pressure Gas Sampling ValveA valve with anoperating temperature of 225 C and operating pressure of27.57 bar to be placed in a heated enclosure maintained atapproximately 150 C and used to sample ethene vapor. Anexternal
40、 sample loop is installed on this valve. A 1000 Lsample loop has been used successfully. The sample loopsample size shall be sized experimentally to provide desireddetection limits. This valve must reproduce to within 5 percentrelative standard deviation on each component.6.5.5 Heated Valve Enclosur
41、eAny enclosure capable ofmaintaining the valve and sample loop at 150 C.6.5.6 Connecting TeesAny tees that can provide an inertconnection.6.5.7 TubingAny tubing capable of providing an inertconnection.TABLE 2 Chromatographic Operating ConditionsParameter Deans Switch (Fig. 1) Deans Switch (Fig. 2) V
42、alve Cut (Fig. 3)Valve 1C 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 C
43、olumn Oven, C 50 50 50Initial 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 300D
44、etector RangeBBBASplit ratio 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
45、 each oxygenate but asto avoid detector signal saturation.D7423 16136.5.8 Needle ValveMicrometering valve capable of lowflow control 2 mL min to 90 mL min.6.6 Data AcquisitionAny computerized data acquisitionsystem shall be used for peak area integration and graphicpresentation of the chromatogram.
46、Alternatively 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 stoc
47、ks of 98 % purity or better. The calibration materialsare listed in Table 1.7.2 Calibration Standard MixtureA standard mixture con-taining known concentrations of each oxygenate listed in Table1 should be prepared gravimetrically. This mixture shall beused as an external calibration standard.7.3 Com
48、pressed HydrogenLess than 1 mg kg hydrocar-bon impurities for FID fuel gas.7.4 Compressed HeliumGas purity 99.999 %. Note thathelium supplies often contain low level amounts of water.Water can dramatically deteriorate the performance of theanalytical column (oxygenates column). It is strongly recom-
49、mended that the use of a molecular sieve or other suitable waterremoval system be implemented to eliminate the possibility ofcontaminating the analytical 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 of Practice D1265, D1835, D6849 or theirequivalent,
