1、Designation: D5441 98 (Reapproved 2013)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 180C 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.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 thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to
7、 consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1364 Test Method for Water in Volatile Solvents (KarlFischer Reagent Titration Method)D3700 Practice for Obtaining LPG Sam
8、ples 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 FactorsE355 Practice for Gas Chromatography Terms and
9、 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. Detailed definitions of these can be found in Pra
10、cticesE355 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 representative aliquot of the MTBE product sa
11、mple 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 process. Components are sensed by a flame ionizatio
12、ndetector 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 comparing its retention time to thoseestablished by analyzing standards under identical conditions.4.3 The concentrat
13、ion 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 the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of
14、SubcommitteeD02.04.0L on Gas Chromatography Methods.Current edition approved May 1, 2013. Published August 2013. Originallyapproved in 1993. Last previous edition approved in 2008 as D544198(2008)1.DOI: 10.1520/D5441-98R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orconta
15、ct ASTM Customer Service at serviceastm.org. For Annual Book 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 States1factor. The detector res
16、ponse 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 effect upon the value of MTBE as a gasolineadditive. Oxygenate and olefin contents a
17、re 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.5.2 Open tubular column gas chromatography with a flameionization detector, us
18、ed 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 with MTBE. However, these are not com-monly found impurities in MTBE.7. Appara
19、tus7.1 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 proper sample intro-duction. Carrier gas controls must be of adequate precision top
20、rovide 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 example, if a 150 m column is used, apressure of approximately 550 kPa (80 psig) is required).
21、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 injection to the splitting injector is employed.Devices capable of 0.1 to 0.5 L injec
22、tions 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 and, since overloaded peaks are skewed,variation in retention times. Watch for any s
23、kewed 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 afused silica open tubular column with non-polar methyl sili-cone bonded (cross-l
24、inked) 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 beused. A minimum resolution between trans-2-pentene andtert-butanol, and between c
25、is-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 device used for quantification of theseanalyses must meet or exceed these minimum requirement
26、s: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 rejection capability,7.4.5 Sampling rate for fast ( tA12. Calibration and Standardization12
27、.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 contaminants inMTBE products are listed in Table 2. Analyze mixturescontaining these compo
28、unds 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-tures containing these materials under identical conditions. Atypical chromatogram o
29、f 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 analyzinga prepared standard7,5with concentrations similar to thoseencountered in
30、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 according to Practice D4626 by measuring theresponse factors of certified blends th
31、at 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 evaluation in Section 11.13.2 When the gas chromatograph has been inoperative formore th
32、an 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.TABLE 2 Typical Retention Times on Three Columns, Relative Mass Response FactorsAand DensitiesB,Cfor Co
33、mmon 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-butene 4.
34、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 9.37 16
35、.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 0.740519 2,
36、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 0.7415
37、25 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-tran
38、s-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.12CSee We
39、ast.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 separat
40、e using subambient temperature.D5441 98 (2013)413.3 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
41、 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 withknown reference standards or sample components as discussedin 12.1. If a computing integr
42、ator 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 oxygenateshave very different response factors than hydrocarbons andnormalization is used for qu
43、antification.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 response factor of 1.00 for unknowncontaminants.14.3 Obtain the concentration of water in the
44、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 mass % of each component to two decimalplaces.14.6 If the volumetric concentration of each
45、oxygenate isdesired, calculate the volumetric concentration of each oxy-genate using Eq 4 as follows:Vi5Wi3DsDi(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 vo
46、lume % 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 upon several factors includingvolatility of the component, its concentration and the degree to
47、which 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 310Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report R
48、R:D02-1306.NOTE 1Numbers correspond to components in Table 2.FIG. 1 Typical Chromatogram of a MTBE Sample Analyzed on the150 M ColumnTABLE 3 Repeatability and Reproducibility for Selected MTBE ComponentsComponentRange,Weight %Repeatability ReproducibilityMethanol 0.0113 to 0.3719 0.0181 * X0.250.099
49、4 * X0.25Isobutylene/1-butene 0.0168 to 0.1356 0.0998 (X + 0.0049) 0.3199 (X + 0.0049)Isopentane 0.0561 to 1.9290 0.0390 * X0.66670.1646 * X0.6667Trans-2-pentene 0.0128 to 0.5003 0.0084 * X0.00360.0630 * X0.2678Tert-butanol 0.4741 to 0.8763 0.016 0.132Cis-2-pentene 0.0970 to 0.5089 0.0401 * X0.50.1092 * X0.52-methyl-2-butene 0.0144 to 0.4391 0.0122 * X0.09940.0799 * X0.3818Methyl tert-butyl ether 93.23 to 97.87 0.0448 (X/100)180.2932 (X/100)18Sec-butyl methylether0.0200 to 0.4821 0.0065 * X0.01230.1606 * X0.4424Tert-amyl methylether0.4961 to 0.7072 0.019 0.124
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