1、Designation: D5441 98 (Reapproved 2017)Standard Test Method forAnalysis of Methyl Tert-Butyl Ether (MTBE) by GasChromatography1This standard is issued under the fixed designation D5441; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, 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 determination of the purityof methyl tert-butyl ether (MTBE) by gas chromat
3、ography. 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 ethyl ketone. Impurities are determined to a minimumconcentration of 0.02 mass %.1.2 This test method
4、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 D1364and the result used to normalize the chromatographic values.1.4 A majority of the impurities in MTBE is resolved by thetest method,
5、 however, some co-elution is encountered.1.5 This test method is inappropriate for impurities that boilat temperatures higher than 180 C or for impurities that causepoor or no response in a flame ionization detector, such aswater.1.6 The values stated in SI (metric) units of measurementare preferred
6、 and used throughout the standard.1.6.1 ExceptionAlternate units, in common usage, arealso provided to improve clarity and aid the user of this testmethod.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of
7、this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the D
8、ecision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1364 Test Method for Water in Volatile Solvents (KarlFischer Reagent Titratio
9、n Method)D3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4626 Practice for Calculation of Gas ChromatographicResponse FactorsE
10、355 Practice for Gas Chromatography Terms and Relation-shipsE594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid Chromatography3. Terminology3.1 DefinitionsThis test method makes reference to manycommon gas chromatographic procedures, terms, and relation-ships. Deta
11、iled definitions of these can be found in PracticesE355 and E594.3.2 Definitions of Terms Specific to This Standard:3.2.1 C4to C12olefinscommon olefin impurities in MTBEare unreacted feedstock and dimers or trimers of feed such astrimethylpentene or pentamethylheptene.4. Summary of Test Method4.1 A
12、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 where the components are separated by the chromato-graphic proces
13、s. Components are sensed by a flame ionizationdetector as they elute from the column.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.04.0L on Gas Chromatography Methods.Current ed
14、ition approved Oct. 1, 2017. Published November 2017. Originallyapproved in 1993. Last previous edition approved in 2013 as D544198(2013).DOI: 10.1520/D5441-98R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
15、 of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recogniz
16、ed principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14.2 The detector signal is processed by an electronic dataacquisiti
17、on system or integrating computer. Each eluting com-ponent is identified by comparing 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 h
18、as been corrected by a detector response multiplicationfactor. 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 adeleterious effec
19、t 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 regulatory purposes
20、.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 to co-elute
21、 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 required for prop
22、er 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 andgauges must be designed to attain the linear velocity requiredin the column used (for example, if a 1
23、50 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 sample injec
24、tion to the splitting injector is employed.Devices capable of 0.1 L 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 components an
25、d, 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 utilizes
26、 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 power may b
27、eused. 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 co-elution of impurities.7.4 Electronic Data Acquisition SystemAny data acquisi-tion and integration device use
28、d 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 rejectio
29、n 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 contami
30、nants 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.7,5Retention times of othersuspected contaminants can be established by analyzing mix-t
31、ures 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 verified by
32、 analyzinga prepared standard7,5with 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 preparedcomposition, the response factors should be experimentallydetermined
33、according to Practice D4626 by measuring theresponse factors of certified blends that have been purchased orblends prepared according to Practice D4307.13. Procedure13.1 Set the instrument operating variables to the valuesspecified in Table 1 or to a temperature determined to besuitable by the evalu
34、ation in Section 11.TABLE 2 Typical Retention Times on Three Columns, Relative Mass Response FactorsAand DensitiesB,Cfor Common MTBE ProductComponentsNo. ComponentRetention Time m, minTypical ResponseFactorDensity atapproximately20 C g mL50 100 1501 MethanolD3.72 7.84 12.89 3.20 0.79142 IsobutyleneE
35、3.85 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-butene 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 15.6
36、9 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 9.37 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.
37、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 0.740519 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
38、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 0.741525 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-trime
39、thyl-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-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
40、-pentamethyl-3-heptene 26.46 30.92 41.64 0.90 0.759AResponse factors are relative to heptane = 1.00.BSee Driesbach.12CSee Weast.11DMethanol coelutes with isobutane on the 50 m and 100 m columns but is separated on the 150 m column. Subambient temperature conditions will separate thesecompounds.EIsob
41、utylene and 1-butene co-elute on all three columns at the typical temperature conditions. These components are known to separate using subambient temperature.D5441 98 (2017)413.2 When the gas chromatograph has been inoperative formore than 24 h, raise the column temperature to the maximumtemperature
42、 used in the method and hold for 20 min to removecontaminants from the column. Lower the temperature to theinitial method temperature.13.3 Set the recorder or integration device, or both, foraccurate presentation of the data. Set instrumental sensitivitysuch that any component of at least 0.02 % mas
43、s will bedetected, integrated, and reported.13.4 Inject 0.1 L 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 times with
44、known 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 oxygena
45、teshave 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 a respo
46、nse factor of 1.00 for unknowncontaminants.14.3 Obtain the concentration of water in the sample asdetermined by Test Method D1364, 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 Report the ma
47、ss % 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 20 C of Com
48、ponent i as found in Table 2,andDs= density at 20 C 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 dependent up
49、on 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 and 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 t
