1、Designation: D 5441 98 (Reapproved 2008)1An American National StandardStandard Test Method forAnalysis of Methyl Tert-Butyl Ether (MTBE) by GasChromatography1This standard is issued under the fixed designation D 5441; the number immediately following the designation indicates the year oforiginal ado
2、ption 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 May 2008.1. Scope1.1 Th
3、is test method covers the determination of the purityof methyl tert-butyl ether (MTBE) by gas chromatography. Italso provides a procedure to measure impurities in MTBE suchas C4to C12olefins, methyl, isopropyl and tert-butyl alcohols,methyl sec-butyl and methyl tert-amyl ethers, acetone, andmethyl e
4、thyl ketone. Impurities are determined to a minimumconcentration of 0.02 mass %.1.2 This test method is not applicable to the determinationof MTBE in gasoline.1.3 Water cannot be determined by this test method andmust be measured by a procedure such as Test Method D 1364and the result used to normal
5、ize the chromatographic values.1.4 A majority of the impurities in MTBE is resolved by thetest method, however, some co-elution is encountered.1.5 This test method is inappropriate for impurities that boilat temperatures higher than 180C or for impurities that causepoor or no response in a flame ion
6、ization detector, such aswater.1.6 The values stated in SI (metric) units of measurementare preferred and used throughout the standard.Alternate units,in common usage, are also provided to improve clarity and aidthe user of this test method.1.7 This standard does not purport to address all of thesaf
7、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1364 Test Method fo
8、r Water in Volatile Solvents (KarlFischer Reagent Titration Method)D 3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4626 Pr
9、actice for Calculation of Gas ChromatographicResponse FactorsE 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid Chromatography3. Terminology3.1 DefinitionsThis test method makes reference to manycommon
10、 gas chromatographic procedures, terms, and relation-ships. Detailed definitions of these can be found in PracticesE 355 and E 594.3.2 Definitions of Terms Specific to This Standard:3.2.1 C4to C12olefinscommon olefin impurities inMTBE are unreacted feedstock and dimers or trimers of feedsuch as trim
11、ethylpentene or pentamethylheptene.4. Summary of Test Method4.1 A representative aliquot of the MTBE product sample isintroduced into a gas chromatograph equipped with a methylsilicone bonded phase fused silica open tubular column.Helium carrier gas transports the vaporized aliquot through thecolumn
12、 where the components are separated by the chromato-graphic process. Components are sensed by a flame ionizationdetector as they elute from the column.4.2 The detector signal is processed by an electronic dataacquisition system or integrating computer. Each eluting com-ponent is identified by compar
13、ing its retention time to thoseestablished by analyzing standards under identical conditions.4.3 The concentration of each component in mass percent isdetermined by normalization of the peak areas after each peakarea has been corrected by a detector response multiplication1This test method is under
14、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, 2008. Published September 2008. Originallyapproved in 1993. Last previous edition approved in 2003 as D 5
15、44198(2003)1.2For 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 D
16、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.factor. The detector response factors are determined by ana-lyzing prepared standards with concentrations similar to thoseencountered in the sample.5. Significance and Use5.1 The presence of impurities in MTBE product can have adelet
17、erious effect upon the value of MTBE as a gasolineadditive. Oxygenate and olefin contents are of primary con-cern. This test method provides a knowledge of the composi-tion of MTBE product. This is useful in the evaluation ofprocess operations control, in the valuation of the product, andfor regulat
18、ory purposes.5.2 Open tubular column gas chromatography with a flameionization detector, used by the test method, is a technique thatis sensitive to the contaminants commonly found in MTBE,and a technique that is widely used.6. Interferences6.1 Cyclopentane and 2,3-dimethylbutane have been ob-served
19、 to co-elute with MTBE. However, these are not com-monly found impurities in MTBE.7. Apparatus7.1 Gas ChromatographInstrumentation capable of oper-ating at the conditions listed in Table 1. A heated flashvaporizing injector designed to provide a linear sample splitinjection (that is, 200:1) is requi
20、red for proper sample intro-duction. Carrier gas controls must be of adequate precision toprovide reproducible column flows and split ratios in order tomaintain analytical integrity. Pressure control devices andgages must be designed to attain the linear velocity required inthe column used (for exam
21、ple, if a 150 m column is used, apressure of approximately 550 kPa (80 psig) is required). Ahydrogen flame ionization detector with associated gas controlsand electronics, designed for optimum response with opentubular columns, is required.7.2 Sample IntroductionManual or automatic liquid sy-ringe s
22、ample injection to the splitting injector is employed.Devices capable of 0.1 to 0.5 L injections are suitable. Itshould be noted that inadequate splitter design, or poorinjection technique, or both can result in poor resolution.Overloading of the column can also cause loss of resolution forsome comp
23、onents and, since overloaded peaks are skewed,variation in retention times. Watch for any skewed peaks thatindicate overloading during column evaluation. Observe thecomponent size and where possible, avoid conditions leadingto this problem during the analyses.7.3 Open Tubular Column3This test method
24、 utilizes afused silica open tubular column with non-polar methyl sili-cone bonded (cross-linked) phase internal coating such as oneof the following:Column length 50 m 100 m 150 mFilm thickness 0.5 m 0.5 m 1.0 mInternal diameter 0.20 mm 0.25 mm 0.25 mmOther columns with equal or greater resolving po
25、wer may beused. A minimum resolution between trans-2-pentene andtert-butanol, and between cis-2-pentene and tert-butanol of 1.3is required. The 150 m column is expected to decrease thelikelihood of coelution of impurities.7.4 Electronic Data Acquisition SystemAny data acquisi-tion and integration de
26、vice used for quantification of theseanalyses must meet or exceed these minimum requirements:7.4.1 Capacity for at least 50 peaks per analysis,7.4.2 Normalized area percent calculations with responsefactors,7.4.3 Identification of individual components based on re-tention time,7.4.4 Noise and spike
27、rejection capability,7.4.5 Sampling rate for fast ( tA12. Calibration and Standardization12.1 Component peaks from a sample analysis are identifiedby matching their retention time with the retention time ofreference compounds analyzed under identical conditions.Typical retention times of most common
28、 contaminants inMTBE products are listed in Table 2. Analyze mixturescontaining these compounds to verify their retention times.Mixtures used for determining retention times can be blendedfrom pure compounds or purchased.5,7Retention times of othersuspected contaminants can be established by analyzi
29、ng mix-tures containing these materials under identical conditions. Atypical chromatogram of a MTBE product sample, analyzed onthe 150 meter column, is shown in Fig. 1. The peaks areindexed to Table 2.12.2 Typical mass relative response factors are found inTable 2. These response factors must be ver
30、ified by analyzinga prepared standard5,7with concentrations similar to thoseencountered in a MTBE product sample and comparing themeasured results with the prepared composition. If the mea-sured composition does not agree with the prepared composi-tion, the response factors should be experimentally
31、determinedaccording to Practice D 4626 by measuring the responsefactors of certified blends that have been purchased or blendsprepared according to Practice D 4307.13. Procedure13.1 Set the instrument operating variables to the valuesspecified in Table 1 or to a temperature determined to besuitable
32、by the evaluation in Section 11.13.2 When the gas chromatograph has been inoperative formore than 24 h, raise the column temperature to the maximumtemperature used in the method and hold for 20 min to removecontaminants from the column. Lower the temperature to theinitial method temperature.13.3 Set
33、 the recorder or integration device, or both, foraccurate presentation of the data. Set instrumental sensitivitysuch that any component of at least 0.02 % mass will bedetected, integrated, and reported.TABLE 2 Typical Retention Times on Three Columns, Relative Mass Response FactorsAand DensitiesB,Cf
34、or Common MTBE ProductComponentsNo. ComponentRetention Time m, minTypical ResponseFactorDensity atapproximately 20Cg/mL50 100 1501 MethanolD3.72 7.84 12.89 3.20 0.79142 IsobutyleneE3.85 8.00 13.39 1.18 0.59423 Butane 3.92 8.08 13.59 1.17 0.57884 Trans-2-butene 3.99 8.16 13.77 1.13 0.60425 Cis-2-bute
35、ne 4.10 8.29 14.11 1.10 0.62136 3-methyl-1-butene 4.41 8.67 14.95 1.05 0.62727 Acetone 4.61 8.91 15.29 1.85 0.78998 Isopentane 4.66 8.93 15.51 1.04 0.62019 2-propanol 4.77 9.06 15.69 1.88 0.785510 1-pentene 4.82 9.15 15.95 1.05 0.640511 2-methyl-1-butene 4.95 9.31 16.15 1.00 0.650412 Pentane 5.00 9.
36、37 16.37 1.05 0.626213 Trans-2-pentene 5.12 9.49 16.61 1.05 0.648214 Tert-butanol 5.20 9.57 16.70 1.30 0.788715 Cis-2-pentene 5.26 9.67 16.94 1.05 0.655616 2-methyl-2-butene 5.37 9.78 17.13 1.00 0.662317 Cyclopentene 6.17 10.72 18.84 1.00 0.745718 Methyl tert-butyl ether 6.51 11.11 19.15 1.53 0.7405
37、19 2,3-dimethyl-1-butene 6.55 11.17 19.25 1.00 0.680320 4-methyl-cis-2-pentene 6.57 11.21 19.36 1.00 0.66921 2-methylpentane 6.63 11.28 19.39 1.00 0.653222 Methyl ethyl ketone 6.86 11.48 19.65 1.51 0.805423 3-methylpentane 7.09 11.80 20.17 1.00 0.664524 Sec-butyl methyl ether 7.22 11.93 20.23 1.53 0
38、.741525 Ethyl tert-butyl ether 8.54 13.36 21.85 1.50 0.751926 Tert-amyl methyl ether 11.93 16.27 25.19 1.41 0.770327 3,5-dimethyl-1-hexene 14.85 18.23 27.39 0.90 0.70828 2,4,4-trimethyl-1-pentene 15.03 18.40 27.65 0.90 0.71529 2,4,4-trimethyl-2-pentene 16.17 19.27 28.47 0.90 0.721830 3,4,4-trimethyl
39、-trans-2-pentene 17.86 20.86 30.19 0.90 0.73931 2,3,4-trimethyl-2-pentene 19.02 22.00 31.28 0.90 0.743432 4,4-dimethyl-2-neopentyl-1-pentene 26.26 30.67 41.33 0.90 0.75933 2,2,4,6,6-pentamethyl-3-heptene 26.46 30.92 41.64 0.90 0.759AResponse factors are relative to heptane = 1.00.BSee Driesbach.12CS
40、ee Weast.11DMethanol coelutes with isobutane on the 50 and 100 m columns but is separated on the 150 m column. Subambient temperature conditions will separate thesecompounds.EIsobutylene and 1-butene coelute on all three columns at the typical temperature conditions. These components are known to se
41、parate using subambienttemperature.D 5441 98 (2008)1413.4 Inject 0.1 to 0.5 L of sample into the injection portand start the analysis. Sample size must follow guidelinesdiscussed in 7.2. Obtain a chromatogram and peak integrationreport.14. Calculation14.1 Identify each peak by matching retention tim
42、es withknown reference standards or sample components as discussedin 12.1. If a computing integrator is used, examine the report toensure that peaks are properly identified and integrated. It isvery important that all oxygenate peaks be separated fromhydrocarbon peaks and correctly identified since
43、oxygenateshave very different response factors than hydrocarbons andnormalization is used for quantification.14.2 Obtain the integrated areas of each component peak.Multiply each area by its appropriate response factor asdetermined in 12.2 to obtain peak areas corrected for responsedifferences. Use
44、a response factor of 1.00 for unknowncontaminants.14.3 Obtain the concentration of water in the sample asdetermined by Test Method D 1364, or equivalent.14.4 Determine the mass % of each component using Eq 3:mass % component 5corrected peak area 3 100 2 % water!total corrected peak area(3)14.5 Repor
45、t the mass % of each component to two decimalplaces.14.6 If the volumetric concentration of each oxygenate isdesired, calculate the volumetric concentration of each oxy-genate using Eq 4 as follows:Vi5Wi3 DsDi(4)where:Vi= volume % of Component i,Wi= mass % of Component i from Eq 3,Di= density at 20C
46、 of Component i as found in Table 2,andDs= density at 20C of sample under study.14.7 Report the volume % of each component to twodecimal places.15. Precision and Bias1015.1 PrecisionThe precision of any individual measurement resulting from the application of this test method isexpected to be depend
47、ent upon several factors includingvolatility of the component, its concentration and the degree towhich it is resolved from other closely eluting components.Since it is not practical to determine the precision for measure-ment of every component separated by this method, Table 3lists repeatability a
48、nd reproducibility for selected representa-tive components.11,1215.1.1 RepeatabilityThe difference between successivetest results obtained by the same operator with the sameapparatus under constant operating conditions on identical testmaterials would, in the long run, in the normal and correctopera
49、tion of the method, exceed the values calculated from theequations listed in Table 3 only in one case in twenty. Table 4lists typical values for repeatability over the concentrationranges of interest calculated from the equations in Table 3.15.1.2 ReproducibilityThe difference between two singleand independent test results obtained by different operatorsworking in different laboratories on identical test materialswould, in the long run, in the normal and correct operation ofthe test method, exceed the values calculated from the equa-tions listed in Table 3 o
