1、Designation: D7754 111Standard Test Method forDetermination of Trace Oxygenates in Automotive Spark-Ignition Engine Fuel by Multidimensional GasChromatography1This standard is issued under the fixed designation D7754; 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.1NOTEResearch report information was added editorially to Section 14 in November 20
3、15.1. Scope1.1 This test method covers the determination of traceoxygenates in automotive spark-ignition engine fuel. Themethod used is a multidimensional gas chromatographicmethod using 1,2-dimethoxy ethane as the internal standard.The oxygenates that are analyzed are: methyl-tertiary butylether (M
4、TBE), ethyl-tertiary butyl ether (ETBE), diisopropylether (DIPE), methanol, tertiary-amyl methyl ether (TAME),n-propanol, i-propanol, n-butanol, i-butanol, tert-butyl alcohol,sec-butyl alcohol, and tert-pentanol. Ethanol is usually notmeasured as a trace oxygenate since ethanol can be used as themai
5、n oxygenate compound in finished automotive spark-ignition fuels such as reformulated automotive spark-ignitionfuels. The concentration range of the oxygenates covered in theILS study was from 10 g/Kg to 2000 g/Kg. In addition thismethod is also suitable for the measurement of the C5 isomericalcohol
6、s (2-methyl-1-butanol, 2-methyl-2-butanol) presentfrom the fermentation of ethanol.1.2 The ethanol blending concentration for which this testmethod applies ranges from 1 to 15% by volume. Higherconcentrations of ethanol coelute with methanol in the analyti-cal column. Lower levels of ethanol, simila
7、r to the otheroxygenate, can be calibrated and analyzed also. If higherethanol concentrations are expected, the window cutting tech-nique can be used to avoid ethanol from entering the analyticalcolumn and interfere with the determination of the otheroxygenates of interest. Refer to Appendix X1 for
8、details.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3.1 Alternate units, in common usage, are also provided toincrease clarity and aid the users of this test method.1.4 This standard does not purport to address all of
9、thesafety concerns, if any, associated with its 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:2D4057 Practice for Manual
10、 Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4815 Test Method for Determination of MTBE, ETBE,TAME, DIPE, tertiary-Amyl Alcohol and C1to C4Alco-hols in Gasoline by Gas ChromatographyD6304 Test Method for Determination of W
11、ater in Petro-leum Products, Lubricating Oils, and Additives by Cou-lometric Karl Fischer Titration3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 electronic pressure control, nelectronic pneumaticcontrol of carrier gas flows. Can be flow or pressure pro-grammed to speed up el
12、ution of components.3.1.2 flame ionization detector (FID), ndetector used toanalyze the components eluting from the column.3.1.3 fluidic switch, ndevice that reverses the directionalflow in a union T altering the pressure at the midpoint. In itssimplest design it is also known as a Dean Switch.3.1.4
13、 inlet, ncapillary split/splitless inlet system operatedin the split mode is recommended. Operate the inlet within itslinear range.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.
14、04.0L on Gas Chromatography Methods.Current edition approved Oct. 1, 2011. Published November 2011. DOI:10.1520/D7754-11E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
15、efer 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 States13.1.4.1 split ratio, n in capillary gas chromatography, theratio of the total flow of carrier gas to the sample inlet versu
16、sthe flow of the carrier gas to the capillary column is expressedby:Split ratio 5 S1C!/C (1)where:S = flow rate at the splitter vent, andC = flow rate at the column outlet.3.1.5 low volume connector, nspecial union for connect-ing two lengths of tubing 1.6-mm inside diameter and smaller.Sometimes th
17、is is referred to as zero dead volume union.3.1.6 multidimensional gas chromatography, ngas chro-matographic technique where using hardware (valves, pressureswitches, etc.) in which selected components from one column(primary column) are transferred to a secondary columndiffering in characteristics
18、(film thickness, polarity, capacity,etc.) from the first column.3.1.7 ppm, nparts per million, or micrograms per gram(mg/kg).3.1.8 WCOT column, nwall-coated open tubular, a type ofcapillary gas chromatographic column prepared by coating theinside of the capillary wall with a specified thin film ofst
19、ationary phase. The coatings used are either 100% polydim-ethyl siloxane or 5% phenyl-polydimethylsiloxane.3.1.8.1 apolar column, npolydimethylsiloxane nonpolarcolumn used as a pre-column.3.1.8.2 PLOT column-oxygen selective, nporous-layeropen tubular which is an oxygenate selective capillary gas-so
20、lid chromatographic column. It is used as an analyticalcolumn.4. Summary of Test Method4.1 An appropriate internal standard of a product that is notpresent in refinery streams, such as 1,2-dimethoxy ethane(1,2-DME), is added to the sample, which is then introducedinto a gas chromatograph equipped wi
21、th two columns and a4-port switching valve. The sample first passes onto an apolar(non-polar) polydimethylsiloxane WCOT column that per-forms a pre-separation of the trace oxygenates and elutesunwanted high boiling hydrocarbons to vent. The oxygenatesand the DME are transferred to the analytical oxy
22、gen selectivecolumn by the switching valve. While the oxygenates and theDME are eluting from the analytical column, the inlets carriergas is used to elute the hydrocarbons from the pre-column toyield a stable baseline for the next analysis. The auxiliarypressure controller is used to provide carrier
23、 gas to theanalytical column during the analysis.4.2 The eluted components Table 1 are detected by one ortwo flame ionization detectors. In the single detector Configu-ration A (Fig. 1), only the components eluting from theanalytical column are analyzed. In the two detector Configu-ration B (Fig. 2)
24、, detector one is used to monitor the apolarelution and aid in setting “heart-cut” times for specific oxy-genates while the second detector is used to monitor theanalytical column elution and also for the quantitation of theoxygenates. The second detector response is proportional to theoxygenates an
25、d DME components concentration. The signal isrecorded, the peak areas are measured, and the concentration ofeach oxygenate is calculated with reference to the internalstandard.4.3 Alternatively, a fluidic switching system, ConfigurationC(Figs. 3 and 4) may be used instead of valve switching. Inthis
26、system, the two columns are joined by a zero dead volume(ZDV) tee purged by an auxiliary carrier source. At injection,the auxiliary flow is low, and the inlet flow is sufficient so thatat the midpoint where the two columns join, the flow is therequired flow to transfer the oxygenates to the PLOT col
27、umn.Thus, there is forward flow through the pre-column and theanalytical column. Once the oxygenates have passed through tothe analytical column, the inlet flow is decreased and theauxiliary flow is increased, which results in backflushing thepre-column through the split vent of the front inlet whil
28、e theanalytical column continues the separation.5. Significance and Use5.1 The analysis of trace oxygenates in automotive spark-ignition engine fuel has become routine in certain areas toensure compliance whenever oxygenated fuels are used. Inaddition, test methods to measure trace levels of oxygena
29、tes inautomotive spark-ignition fuel are necessary to assess productquality.TABLE 1 Component List with Retention and Calibration Characteristics for WCOT/PLOT Column Set Using Conditions of Table 2AComponent RT (min) Mol Wt BP (C) Slope y-Int Corr. Coef.ETBE 12.7 102.2 70 to 72 1.919 -0.02 0.999MTB
30、E 12.8 88.2 55 to 56 1.689 0.01 0.999DIPE 12.9 102.2 68 to 69 2.124 -0.06 0.999TAME 13.6 102.2 85 to 86 2.023 -0.02 0.999Methanol 15.6 32.0 65 0.779 -0.09 0.997Ethanol 18.7 46.1 78 1.352 0.19 0.999iso-Propanol 22.2 60.1 81 to 83 1.504 -0.06 0.999n-Propanol 22.2 60.1 97 . . .t-Butanol 23.8 74.1 82 1.
31、951 -0.12 0.999s-Butanol 23.8 74.1 98 . . .iso-Butanol 23.8 74.1 117 . . .n-Butanol 24.4 74.1 118 1.906 -0.05 0.999tert-Pentanol 25.1 88.1 102 2.148 -0.04 0.9981,2-DME 26.0 90.1 85 . . .AFor coeluting compounds the response is assigned to the first peak listed. Values may be different for different
32、instruments.D7754 11126. Apparatus6.1 ChromatographA multidimensional gas chromato-graphic system, which is able to adequately resolve oxygenatesand an internal standard and to eliminate hydrocarbon, as wellas other interferences, is used for these analyses. The instru-ment is to be configured to op
33、erate using the approximateconditions listed in Table 2. The system requires a columnswitching mechanism equivalent to Fig. 1 or Fig. 2 if using avalve system. If using a fluidic system then the fluidic switchand auxiliary flow control are required as shown in Fig. 3 andFig. 4. Carrier gas flow cont
34、rollers (EPC) shall be capable ofprecise control where the flow rates are low. Pressure controlFIG. 1 Schematic of Chromatographic SystemConfiguration AFIG. 2 Schematic of Chromatographic SystemConfiguration BFIG. 3 Fluidic Switch SchematicOxygenate TransferD7754 1113devices and gages shall be capab
35、le of precise control for thetypical pressures required.6.1.1 DetectorTwo-flame ionization detectors are prefer-ably used (Configuration B), although the analysis can beperformed using only one detector (Configuration A and C).The system shall have sufficient sensitivity and stability toobtain a sig
36、nal-to-noise ratio of at least 5 to 1 fora1ppm(m/m) concentration of any oxygenate. In the fluidic systemonly one detector is used.6.1.2 Switching ValveA switching valve, to be locatedwithin the gas chromatographic column oven or separate oven,capable of performing the functions described in 9.2 and
37、illustrated in Fig. 1. The valve shall be of low volume designFIG. 4 Fluidic Switch SchematicPre-column BackflushTABLE 2 Chromatographic ConditionsConfiguration Switching Valve Fluidic SwitchCarrier Gas Helium HeliumInjection Volume 1.0 L 1.0 LInlet: Split/Splitless (Split mode) Split/Splitless (Spl
38、it mode)Temperature 250C 250CSplit Ratio 10:1 10:1PressureA7.5 psi, Constant Pressure 2.58 psi, Flow Program ModeColumns and FlowsPre-column 30 m by 0.53 mm by 5.0 m PDMS7.5 mL/min 60C15 m by 0.53 mm by 1.5 m 5% phenyl PDMSInitial Flow: 5.4 mL/min 60CHold for 1.5 minRamp: 90 mL/min to -5 mL/minHold
39、until end of runAnalytical Column 10 m by 0.53 mm by 10 m Oxygen Selective7.5 mL/min 60C10 m by 0.53 mm by 10 m Oxygen Selective7.0 mL/min constant flowOven:Initial Temperature 60C 60CInitial Hold 6.0min 6.0minRamp 1 10C/min 10C/minFinal Temperature 150C 150CFinal Hold 5.0 min 5.0 minRamp 2 10C/min
40、10C/minFinal Temperature 220C 220CFinal Hold 3.0 min 3.0 minTotal Time 30 min 30 minDetector: FID FIDTemperature 275C 275CHydrogen 40 mL/min 40 mL/minAir 450 mL/min 450 mL/minMake-up (N2) 10 mL/min 10 mL/minValve Temperature 150C N/AAuxiliary Pressure 10.6 psi 1.50 psiVent Restrictor 30 by116 by 0.0
41、10 in. SSt N/ADefault Valve Times (for complete analysis):Initial OFF N/A0.50 min ON N/A4.50 min OFF N/AAFor Configuration A valve timing determination, 9.2, set the inlet pressure to 5 psi.D7754 1114and not contribute significantly to chromatographic deteriora-tion. Alternatively a Deans switching
42、arrangement can also beused as shown in Figs. 3 and 4.6.1.2.1 A commercially available valve: 1.6-mm fittings,0.75 mm ports was used in the method development. Anequivalent valve may be used.6.1.2.2 Fluidic Switch, as an option to the two-positionSwitching Valve. See 4.3, Table 2, and Figs. 3 and 4
43、for adescription. Additional flow source is required as well ashardware, which is located in the oven for the columnconnection.6.1.2.3 Some gas chromatographs are equipped with anauxiliary oven, which can be used to contain the valve at anisothermal temperature. In such a configuration, the twocapil
44、lary columns are located in the main oven and connectedto the valve by using low dead volume and inert stainless steeltubing terminated in the GC oven.6.1.2.4 An automatic valve switching device is used toensure repeatable switching times. Such a device is synchro-nized with injection and data colle
45、ction times. For the pressureswitching approach, automatic precise and stable pressurecontrol shall be used. Fluidic systems require both a fluidicswitch and a programmable auxiliary pressure source tomaintain and program flows.6.1.3 Injection SystemThe chromatograph is to beequipped with a heated s
46、plitting-type inlet device containing areplaceable glass deactivated liner (single-taper style) withdeactivated glass wool at the bottom to retain non-vaporizedcomponents). Split injection is necessary to maintain the actualchromatographed sample size within the limits of column anddetector efficien
47、cy and linearity.6.1.3.1 A microliter automatic syringe injector is used forintroducing representative samples into the gas chromato-graphic inlet and for adequate repeatability.6.2 Data Acquisition System:6.2.1 ComputerA data acquisition system containing acomputer and data acquisition software is
48、required.6.2.2 IntegratorAlternatively, an integrator can be used tomeasure peak areas and to perform the analytical calculations.6.3 Column Class:6.3.1 Apolar (Non-polar) Pre-ColumnThis column per-forms a pre-separation of the oxygenates and internal standardfrom hydrocarbons in the same boiling po
49、int range. Unless aseparate auxiliary oven is provided for it, the apolar columnshall perform at the same temperature as the polar columndoes.6.3.1.1 WCOT Methyl Silicone Pre-Column30 m long by0.53 mm inside diameter fused silica column with a 5-m filmthickness of cross-linked polydimethylsiloxane. With fluidicswitch (Configuration C) a 30 m long by 0.53 mm with a 1.5m 5% phenyl polydimethyl siloxane is recommended.6.3.2 Polar Analytical ColumnAny column with equiva-lent or better chromatographic efficiency and s
