1、Designation: D 5441 98 (Reapproved 2003)e1An 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 ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEWarning notes were editorially moved into the standard text in August 2003.
3、1. Scope1.1 This 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, aceton
4、e, andmethyl ethyl 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
5、used to normalize 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
6、in a flame ionization 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 addres
7、s all of thesafety 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:D 1364
8、Test Method for Water in Volatile Solvents (KarlFischer Reagent Titration Method)2D 3700 Practice for Obtaining LPG Samples Using FloatingPiston Cylinder3D 4057 Practice for Manual Sampling of Petroleum andPetroleum Products3D 4307 Practice for Preparation of Liquid Blends for Use asAnalytical Stand
9、ards3D 4626 Practice for Calculation of Gas ChromatographicResponse Factors3E 355 Practice for Gas Chromatography Terms and Rela-tionships4E 594 Practice for Testing Flame Ionization Detectors Usedin Gas Chromatography43. Terminology3.1 Definitions:3.1.1 This test method makes reference to many comm
10、ongas chromatographic procedures, terms, and relationships.Detailed definitions of these can be found in Practices E 355and 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 trime
11、thylpentene 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 compari
13、ng its retention time to thoseestablished by analyzing standards under identical conditions.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04 on Hydrocarbon Analysis.Current edition approved Ma
14、y 10, 2003. Published August 2003. Originallyapproved in 1993. Last previous edition approved in 1998 as D 544198.2Annual Book of ASTM Standards, Vol 06.04.3Annual Book of ASTM Standards, Vol 05.02.4Annual Book of ASTM Standards, Vol 03.06.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
15、 C700, West Conshohocken, PA 19428-2959, United States.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 multiplicationfactor. The detector response factors are determined by ana-lyzin
16、g 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 effect upon the value of MTBE as a gasolineadditive. Oxygenate and olefin contents are of primary con-cern. This test method
17、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.5.2 Open tubular column gas chromatography with a flameionization detector, used by the test method, is a technique tha
18、tis 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 with MTBE. However, these are not com-monly found impurities in MTBE.7. Apparatus7.1 Gas ChromatographInstrumentation c
19、apable 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 proper sample intro-duction. Carrier gas controls must be of adequate precision toprovide reproducible column flows and spli
20、t ratios in order tomaintain analytical integrity. Pressure control devices andgages must be designed to attain the linear velocity required inthe column used (for example, if a 150 m column is used, apressure of approximately 550 kPa (80 psig) is required). Ahydrogen flame ionization detector with
21、associated gas controlsand electronics, designed for optimum response with opentubular columns, is required.7.2 Sample IntroductionManual or automatic liquid sy-ringe sample injection to the splitting injector is employed.Devices capable of 0.1 to 0.5 L injections are suitable. Itshould be noted tha
22、t 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 and, since overloaded peaks are skewed,variation in retention times. Watch for any skewed peaks thatindicate overloading duri
23、ng column evaluation. Observe thecomponent size and where possible, avoid conditions leadingto this problem during the analyses.7.3 Open Tubular ColumnThis test method utilizes afused silica open tubular column with non-polar methyl sili-cone bonded (cross-linked) phase internal coating such as oneo
24、f the following:5Column 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 beused. A minimum resolution between trans-2-pentene andtert-butanol, and between cis-2-pentene and tert-butanol of 1.3is re
25、quired. The 150 m column is expected to decrease thelikelihood of coelution of impurities.7.4 Electronic Data Acquisition SystemAny data acquisi-tion and integration device used for quantification of theseanalyses must meet or exceed these minimum requirements:7.4.1 Capacity for at least 50 peaks pe
26、r 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 rejection capability,7.4.5 Sampling rate for fast ( tA12. Calibration and Standardization12.1 Component peaks from a sample analysis
27、 are identifiedby matching their retention time with the retention time ofreference compounds analyzed under identical conditions.Typical retention times of most common contaminants inMTBE products are listed in Table 2. Analyze mixturescontaining these compounds to verify their retention times.Mixt
28、ures used for determining retention times can be blendedfrom pure compounds or purchased.8Retention times of othersuspected contaminants can be established by analyzing mix-tures containing these materials under identical conditions. Atypical chromatogram of a MTBE product sample, analyzed onthe 150
29、 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 analyzinga prepared standard8with concentrations similar to thoseencountered in a MTBE product sample and comparing themeasur
30、ed results with the prepared composition. If the mea-sured composition does not agree with the prepared composi-tion, the response factors should be experimentally determinedaccording to Practice D 4626 by measuring the responsefactors of certified blends that have been purchased or blendsprepared a
31、ccording 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 by the evaluation in Section 11.13.2 When the gas chromatograph has been inoperative formore than 24 h, raise the column temperature to
32、the maximumtemperature used in the method and hold for 20 min to removecontaminants from the column. Lower the temperature to theinitial method temperature.TABLE 2 Typical Retention Times on Three Columns, Relative Mass Response FactorsAand DensitiesB,Cfor Common MTBE ProductComponentsNo. ComponentR
33、etention 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-butene 4.10 8.29 14.11 1.10 0.62136 3-methyl-1-but
34、ene 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 9.37 16.37 1.05 0.626213 Trans-2-pentene 5.12 9.
35、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 0.740519 2,3-dimethyl-1-butene 6.55 11.17 19.25 1.00
36、 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 0.741525 Ethyl tert-butyl ether 8.54 13.36 21.8
37、5 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-trans-2-pentene 17.86 20.86 30.19 0.90 0.7393
38、1 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.13CSee Weast.12DMethanol coelutes with isobutane o
39、n 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 separate using subambienttemperature.D 5441 98 (
40、2003)e1413.3 Set the recorder or integration device, or both, foraccurate presentation of the data. Set instrumental sensitivitysuch that any component of at least 0.02 % mass will bedetected, integrated, and reported.13.4 Inject 0.1 to 0.5 L of sample into the injection portand start the analysis.
41、Sample size must follow guidelinesdiscussed in 7.2. Obtain a chromatogram and peak integrationreport.14. Calculation14.1 Identify each peak by matching retention times withknown reference standards or sample components as discussedin 12.1. If a computing integrator is used, examine the report toensu
42、re that peaks are properly identified and integrated. It isvery important that all oxygenate peaks be separated fromhydrocarbon peaks and correctly identified since oxygenateshave very different response factors than hydrocarbons andnormalization is used for quantification.14.2 Obtain the integrated
43、 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 response factor of 1.00 for unknowncontaminants.14.3 Obtain the concentration of water in the sample asdetermined by Test Method D 13
44、64, 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 mass % of each component to two decimalplaces.14.6 If the volumetric concentration of each oxygenate isdesired, calculate the vol
45、umetric 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 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 twodecima
46、l places.15. Precision and Bias1115.1 PrecisionThe precision of any individual measurement resulting from the application of this test method isexpected to be dependent upon several factors includingvolatility of the component, its concentration and the degree towhich it is resolved from other close
47、ly 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.12,1315.1.1 RepeatabilityThe difference between successivetest results obtai
48、ned by the same operator with the sameapparatus under constant operating conditions on identical testmaterials would, in the long run, in the normal and correctoperation of the method, exceed the values calculated from theequations listed in Table 3 only in one case in twenty. Table 4lists typical v
49、alues for repeatability over the concentrationranges of interest calculated from the equations in Table 3.11Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D02-1306.12Weast, R. C., Chemical Rubber Company Handbook of Chemistry andPhysics, CRC Press, Cleveland, OH, 1979.13Driesbach, R. R., “Physical Properties of Chemical Compounds,” Advances inChemistry Series No. 22, American Chemical Society, Washington, DC 1959.NOTENumbers correspond to components in Table 2.FIG. 1 Typical Chromatogram of a M
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