1、Designation: D7828 12Standard Test Method forDetermination of Residue Composition in LiquefiedPetroleum Gas (LPG) Using Automated Thermal Desorption/Gas Chromatography (ATD/GC)1This standard is issued under the fixed designation D7828; the number immediately following the designation indicates the y
2、ear oforiginal adoption 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.1. Scope1.1 This test method covers the determination of residue
3、inLPG by automated thermal desorption/gas chromatography(ATD/GC) using flame ionization detection (FID).1.2 The quantitation of residue covers a component boilingpoint range from 69C to 522C, equivalent to the boilingpoints of C6through C40n-paraffins.1.2.1 The boiling range covers possible LPG cont
4、aminantssuch as gasoline, diesel fuel, phthalates and compressor oil.Qualitative information on the nature of the residue can beobtained from this test method.1.2.2 Materials insoluble in LPG and components which donot elute from the gas chromatograph or which have noresponse in a flame ionization d
5、etector are not determined.1.2.3 The reporting limit (or limit of quantitation) for totalresidue is 6.7 g/g.1.2.4 The dynamic range of residue quantitation is 6.7 to3300 g/g.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.
6、4 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Doc
7、uments2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Petroleum (LP)Gases, Manual MethodD1835 Specification for Liquefied Petroleum (LP) GasesD2158 Test Method for Residues in Liquefied Petroleum(LP) GasesD3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD6299 Pract
8、ice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceE355 Practice for Gas Chromatography Terms and Relation-ships2.2 Environmental Protection Agency:3EPAMethodTO-17 Determination ofVolatile Organic Com-pounds in Ambient Ai
9、r using Active Sampling ontoSorbent Tubes3. Terminology3.1 Definitions:3.1.1 For the definitions of common chromatographic terms,refer to Practice E355.3.1.2 quality control sample, QC sample, nfor use inquality assurance program to determine and monitor theprecision and stability of a measurement s
10、ystem; a stable andhomogenous material having physical or chemical properties,or both, similar to those of typical samples tested by theanalytical measurement system. The material is properly storedto ensure sample integrity, and is available in sufficient quantityfor repeated long-term testing. D62
11、993.2 Definitions of Terms Specific to This Standard:3.2.1 residue, nsoluble contaminants in LPG with boilingpoints from 69C to 522C, covering the boiling point range ofC6to C40n-paraffins.3.2.2 sorbent tube, na tube that contains commerciallyavailable adsorbents whose composition is specific to ret
12、ain thecomponents of interest (residues).3.2.3 thermal desorber, na sample introduction techniqueused in gas chromatography in which residue adsorbed on anadsorbent material is desorbed into a gas chromatograph.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products an
13、d Lubricants and is the direct responsibility of SubcommitteeD02.H0 on Liquefied Petroleum Gas.Current edition approved Nov. 1, 2012. Published March 2013. DOI: 10.1520/D7828-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
14、For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from United States Environmental Protection Agency (EPA), ArielRios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, http:/www.epa.gov.Copyright ASTM International,
15、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3.1 DiscussionFigs. 1-3 illustrate the flow path andfunction of the thermal desorber used in this test method.3.2.4 thermal desorption, nthe process of using heat,temperature, gas flow and time to remove adsorbe
16、d compo-nents captured in a sorbent tube for introduction into a gaschromatograph for analysis.3.2.5 time group, nin gas chromatography, a set timewindow used in determining the response (area).3.2.5.1 DiscussionIn this test method, the time for re-sponse begins after the elution of pentane and stop
17、s after theelution of C40or of the heavier oil being used for this range,with the sum of the integrated peaks within this time providinga total area of the residue.3.3 Acronyms:3.3.1 ATDautomated thermal desorption3.3.2 ISinternal standard3.3.3 LPGliquefied petroleum gas4. Summary of Test Method4.1
18、Liquefied Petroleum Gas (LPG) is sampled by PracticeD1265 or Practice D3700.4.2 A single phase sample of LPG is then captured on afixed volume sample loop (Sampling Cell). The sample ismaintained within the sample loop at a pressure above itsbubble point as it is released directly onto the hydrocarb
19、on-selective absorbent tube material, thereby trapping the C6plushydrocarbons (residue). The C5minus components passthrough the sorbent(s). The loop weight containing the sampleprovides the sample mass.4.3 The sorbent tube is placed onto the thermal desorber,which desorbs the residue from the tube d
20、irectly onto theanalytical column of the gas chromatograph for separation andquantitation.4.4 The data handling system acquires the raw data from theflame ionization detector. The processing method, which con-tains the response factor (RF) and integration parameters fromstandards previously analyzed
21、, is applied to the sample, and themass of residue in the sample is calculated.5. Significance and Use5.1 Residue in LPG is a contaminant that can lead tooperational problems in some end use applications. Engines,micro-turbines, fuel cells and other equipment may be sensitiveto residue levels as low
22、 as 10 mg/kg.5.2 Contamination of LPG can occur during production,transport, delivery, storage and use. A qualitative indication ofthe contaminants can help track down the source of thecontamination from manufacture, through the distributionsystem, and to the end user.5.3 This test method is designe
23、d to provide a lower detec-tion limit, wider dynamic range, and better accuracy thangravimetric methods like Test Method D2158.5.4 This test method can be performed with little or nodischarge of LPG vapors, compared to Test Method D2158which requires evaporation of 100 mL of sample per test.5.5 Samp
24、ling for residue in LPG using sorbent tubes can beperformed in the field, and the sorbent tubes sent to alaboratory for analysis. This saves significant costs in shipping(weight of tube is approximately 10 grams), and is much saferand easier than transporting LPG cylinders.5.6 This test method deter
25、mines total residues from C6toC40, compared to a thermal gravimetric residue method such asTest Method D2158 which heat the residue to 38C, resultingin a lower recovery due to loss of lighter residue components.5.7 If there is a need to decrease the detection limit ofresidue or individual compounds
26、of interest below 10 g/g, theprocedures in this test method can be modified to achieve 50times enhanced detection limit, or 0.2 g/g.6. Apparatus6.1 Sampling ApparatusRefer to Appendix X1 for thetypical apparatus and configuration for sampling LPG ontosorbent tubes.FIG. 1 Sample Tube Desorption (Prim
27、ary Desorption)D7828 1226.2 Thermal Desorber:6.2.1 A thermal desorber is necessary to remove the residuefrom the sorbent tube and introduce it to a gas chromatograph.It shall be designed to hold the sorbent tubes described in 7.4,and be capable of the parameters of temperature and flow asdetailed in
28、 Table 1.6.2.2 Sorbent Tube Autosampler (Optional)An autosam-pler may be used, but is not required. The instrument used todesign this test method had a 50-tube automated sampler.6.2.3 Sample Re-collection (Optional)Most of the samplebeing analyzed may be re-collected via the split vent onto thesame
29、sorbent tube or onto a new sorbent tube. Samplere-collection allows re-analysis of the same sample if needed,and preservation of the sample if required for further analyticaltesting or legal retention, etc.6.2.4 Transfer line configuration to install the thermal des-orber to the GC or GC column is v
30、endor specific. Consult withthe manufacturer.6.2.5 Appendix X2 contains the apparatus required forspiking standards onto standard sorbent tubes.6.3 Gas Chromatograph (GC), configured with a split/splitless injector and a flame ionization detector that is capableof establishing the method parameters
31、as detailed in Table 2 isrequired.FIG. 2 Cold Trap Desorption (Secondary Desorption)FIG. 3 Valving and Connections in a Thermal DesorberTABLE 1 Thermal Desorber ParametersSorbent Tube Desorb for 18 min at 375C at 30 mL/minConcentrator Trap Trap Low 5C; Trap high 380C; Trap Hold 14 minPneumatics Inle
32、t split 50 mL/min; Outlet split 30 mL/min;analytical column flow 0.8 mL/minAmbient PurgeAPurge for 3 min at ambient temp at 50 mL/minTransfer LineB290CValve TempB260CGC Cycle Time 34 minAA purge is used to rid the tube of residual oxygen and C5minus prior to primarydesorption.BManufacturer specific
33、parameter. Refer to manufacturers guidelines for theseparameters.D7828 1236.4 Capillary Columnwith non-polar stationary phase. A100% dimethyl polysiloxane phase capillary column withdimensions 20 m 0.18 mm 0.2 m was found to besatisfactory. The column shall separate pentane from hexanewith a resolut
34、ion (R value) of 1.5 or greater.6.4.1 Residues in the diesel fuel and compressor oil boilingrange are summed, so detailed component speciation is unnec-essary. If speciation is desired, a high resolution column andoptimized GC oven parameters may be used.6.5 Balance, capable of weighing to 0.1mg.6.6
35、 Data Handling System (Computer), capable of perform-ing timed group integrations, multi-level first order calibrationsand using average response factors to calculate the amount ofresidue in a sample and provide results in a report.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemica
36、ls shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is pure enough to be u
37、sed without lesseningthe accuracy of the determination.7.2 Solvents and Standards(Warningmany of thesechemicals are flammable and the vapors are harmful. Properventilation, safety precautions and other personal protectiveequipment, such as safety glasses, should be used whenhandling. Benzene is an E
38、PA target carcinogen.)7.2.1 Benzene (only if the retention time is desired).7.2.2 Compressor Oil, residue range from approximatelyC18to C40(range will vary depending upon source).7.2.3 Diesel Fuel, residue range from approximately C8toC22(range will vary depending upon source).7.2.4 Dichloromethane,
39、 cleaning and flushing fluid. Analternative appropriate solvent may be used that will dissolveresidue to clean the cylinder and be volatile enough to allow itsevacuation from the cylinder. It is advisable not to use a solventthat would chromatographically elute in the quantitative timewindow specifi
40、ed in this test method (C6to C40) just in case theevacuation (or evaporation) of cleaning solvent is not com-plete. To provide method validity, methylene chloride was usedas a cleaning solvent.7.2.5 Heptane.7.2.6 Hexane.7.2.7 Iso-octane (2,2,4-trimethylpentane).7.2.8 Liquefied Petroleum Gas (LPG)LPG
41、 is a fire hazardand can cause freezer burns. Follow local safety protocolsregarding released ethane, propane and butane vapors fromLPG. Use safety precautions and suitable safety equipmentwhen handling LPG.7.2.9 Paraffn Standard, covering the range from C6to C40at 50 g/g in pentane (commercially av
42、ailable mixtures may beused).7.2.10 Pentane, high purity HPLC grade having non-detectable residue, as solvent for standards.7.2.11 Toluene.7.3 Instrument Gases:7.3.1 Carrier Gas, 99.999% Ultra High Purity Helium.7.3.2 Combustion Gases, 99.999% Ultra High Purity Hy-drogen and Dry Air (some gas chroma
43、tographs use a makeupgas for their flames. Follow vendors instructions).7.4 Sorbent TubesTubes that contain an adsorbent mate-rial designed to adsorb residues commonly found in LPG.57.4.1 Sorbent tubes are shipped and stored with brass endcaps isolating adsorbents from ambient air. EPAMethodTO-17man
44、dates a maximum holding time of 30 days after samplingonto tubes. Some studies indicate stability and accuracy ofcomponents in sorbent tubes to be six months. A maximumholding time of 30 days after LPG sampling is recommended.8. Calibration8.1 External standard calibration technique is used.8.2 Eith
45、er multi-level or single-level calibration may beappropriate.8.2.1 When the concentration range of the samples beinganalyzed is unknown, it is recommended to use a multi-levelcalibration that encompasses the varying concentrations of thesample. If a sample amount falls above this calibration range,d
46、ilution of the sample or a smaller volume with correctionfactor is required so that it falls within the calibration range. Ifa sample amount falls below the reporting limit, the sampleamount should be reported as below the reporting limit. It isnot accurate to provide a result for a sample that fall
47、s outsideof the calibration range of the test method.8.2.2 If the goal is to determine that the residue in thesample is below a maximum limit for residue, and not to reportthe exact amount of residue, a single-level calibration issufficient at that concentration.8.3 To cover the residue range, a com
48、ponent mixture(hexane, heptane, iso-octane, and toluene) is used for the lowerboiling point region (gasoline); diesel is used for the mid-rangeand compressor oil is used for the higher boiling point region.Since speciation is usually not required, a sum of the entire4Reagent Chemicals, American Chem
49、ical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5The sole source of supply of the sorbent tubes for this test method known to thecommittee at this time is Perkin Elmer, 710 BridgeportAvenue, Shelton, CT 06484,. If you are aw
