1、Designation: D7994 17Standard Test Method forTotal Fluorine, Chlorine, and Sulfur in Liquid Petroleum Gas(LPG) by Oxidative Pyrohydrolytic Combustion Followed byIon Chromatography Detection (Combustion IonChromatography-CIC)1This standard is issued under the fixed designation D7994; the number immed
2、iately following the designation indicates the year 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
3、test method covers the individual determination oftotal fluorine, chlorine, and sulfur in liquid petroleum gas(LPG), low molecular weight hydrocarbons, their mixtures,and dimethyl ether (DME) in the range of 1 mgkg to300 mgkg fluorine and sulfur and 5 mgkg to 300 mgkg forchlorine. This test method i
4、s applicable to products describedin Specifications D1835 and D7901 and it can be applicable toprocess streams with similar properties to LPG and othermaterials such as butylene, propylene, and olefins.1.2 This test method can also be applied to the measurementof the bromine and iodine in samples co
5、vered by the scope ofthis test method, but the precision and bias statement of thistest method is not applicable to these halides.1.3 This test method can be applied to sample concentra-tions outside the scope of this test method through adjustmentsof sample injection volume or number of injections
6、combusted(or both), adjustment of injection volume to the ionchromatograph, and adjustment of the final dilution volume ofthe absorbing solution prior to injection to the ion chromato-graph. The precision and scope of this test method is notapplicable to samples that are outside the scope of the met
7、hod.1.4 The values stated in SI units are to be regarded asstandard.1.4.1 ExceptionValues given in parentheses are for infor-mation only.1.5 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 e
8、stablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See Section 9.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principl
9、es 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:2D1193 Specification for Reagent WaterD1265 Practice for Sampling Liquefied Petroleum (LP)Gases, M
10、anual MethodD1835 Specification for Liquefied Petroleum (LP) GasesD3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD6849 Practice for Storage and Use of Liquefied PetroleumGases (LPG) in Sample Cylinders for LPG Test MethodsD7901 Specification for Dimethyl Ether for Fuel Pur
11、posesE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE288 Specification for Laboratory Glass Volumetric FlasksE969 Specification for Glass Volumetric (Transfer) Pipets2.2 OSHA Standards:329 CFR Part 1910.1000 Air Contaminants29 CFR Part 1910.1200 Haz
12、ard Communication3. Terminology3.1 Definitions:3.1.1 combustion ion chromatography (CIC), nan analyti-cal system consisting of oxidative pyrohydrolytic combustionfollowed by ion chromatographic detection.3.1.2 halogen (X), na generic term which includes theelements fluorine, chlorine, bromine, and i
13、odine.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.H0 on Liquefied Petroleum Gas.Current edition approved Jan. 1, 2017. Published April 2017. DOI: 10.1520/D7994-17.2For referen
14、ced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Occupational Safety and Health Administration (OSHA), 200
15、Constitution Ave., NW, Washington, DC 20210, http:/www.osha.gov.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 recognized principles on standardization estab
16、lished 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.13.1.3 hydrogen halide (HX), ninorganic compounds withthe formula HX where X is one of the halogens: fluor
17、ide,chloride, bromide, and iodide.3.1.3.1 DiscussionHydrogen halides are gases that dis-solve in water to give acids.3.1.4 nitrogen oxides (NOX), none or more of the follow-ing compounds: nitric oxide (NO), nitrogen dioxide (NO2).3.1.5 oxidative pyrohydrolytic combustion, na process inwhich a sample
18、 is burned in an oxygen-rich environment attemperatures greater than 900 C and in the presence of excesswater vapor not originating from the combustion of the sample.3.1.5.1 DiscussionIn oxidative pyrohydrolyticcombustion, the sample is converted into carbon dioxide,water, hydrogen halides (HX), and
19、 elemental oxides such asNOXand SOX.3.1.6 sulfur oxides (SOX), none or more of the followingchemical species: sulfur dioxide (SO2), sulfur trioxide (SO3),sulfate (SO42).3.2 Definitions of Terms Specific to This Standard:3.2.1 LPG calibration blank, nthe LPG (usually butane orpropane) used in the pre
20、paration of the LPG calibrationstandards (3.2.2).3.2.2 LPG calibration standard, na material, usually pre-pared in butane or propane, and subsequently used for calibra-tion the CIC System (3.1.1).3.2.3 LPG check standard, na reference material, usuallyprepared in butane or propane, which is used to
21、verifyinstrument calibration and performance of the CIC systemprior to sample analysis but is not used in the instrumentcalibration procedure.3.2.4 LPG QC sample, na pressurized sample previouslyanalyzed and used to verify instrument calibration and perfor-mance of the CIC system prior to sample ana
22、lysis.3.2.5 LPG system blank, nthe area of the anion(s) ofinterest of a combustion ion chromatography (CIC) analysis ofthe LPG calibration blank (3.2.1) used for preparation of theLPG calibration standards (3.2.2). The same combustionconditions, chromatography, time protocols, and injection vol-umes
23、 are used as for the analysis of a LPG sample.3.2.6 non-LPG liquid check standard, na liquid hydrocar-bon sample not in an LPG matrix that is used to troubleshootand check the performance of the CIC system (3.1.1) prior tosample analysis. (See Appendix X1 for preparation.)3.2.7 non-LPG liquid sample
24、, na hydrocarbon sample thatis in liquid phase at 15 C and atmospheric conditions.3.2.8 system blank, nthe area of the anion(s) of interest ofa combustion ion chromatography (CIC) analysis in which thesame combustion, chromatography, and time protocols areused as for a sample analysis, but without t
25、he combustion of anLPG sample, LPG calibration blank, or LPG calibrationstandard.3.3 Abbreviations:3.3.1 CICcombustion ion chromatography3.3.2 conc.concentration3.3.3 CRMcertified reference material3.3.4 DMEdimethyl ether3.3.5 HClhydrogen chloride3.3.6 HFhydrogen fluoride3.3.7 HXhydrogen halide3.3.8
26、 ICion chromatograph or ion chromatography3.3.9 MWmolecular weight3.3.10 LPGliquefied petroleum gas3.3.11 NOXnitrogen oxides (NO and NO2)3.3.12 NOnitric oxide3.3.13 NO2nitrogen dioxide3.3.14 PO43phosphate3.3.15 RSDrelative standard deviation3.3.16 SRMstandard reference material3.3.17 SOXsulfur oxide
27、s (SO, SO2,SO3,SO4,S2O3, andS2O7)3.3.18 SO2sulfur dioxide3.3.19 SO3sulfur trioxide3.3.20 SO42sulfate4. Summary of Test Method4.1 Using an LPG sampling device with a fixed volumeliquid injection loop, a pressurized sample is introduced at acontrolled rate into a high-temperature combustion tube where
28、the sample is combusted in an oxygen-rich pyrohydrolyticenvironment. The gaseous by-products of the combustedsample are trapped in a liquid absorption solution where thehydrogen halides (HX) formed during combustion disassociateinto their respective ions (X), while the sulfur oxides (SOX)formed are
29、further oxidized to SO42in the presence of anoxidizing agent. An aliquot of known volume of the absorbingsolution is then automatically injected into an ion chromato-graph (IC) by means of a sample injection valve. The halideand sulfate anions are separated by the anion separationcolumn of the IC. T
30、he conductivity of the eluent is reducedwith an anion suppression device prior to the ion chromato-graphs conductivity detector, where the anions of interest aremeasured. Quantification of the fluorine, chlorine, and sulfur inthe original combusted sample is achieved by first calibratingthe system w
31、ith a series of LPG calibration standards contain-ing known amounts of fluorine, chlorine, and sulfur and thenanalyzing unknown pressurized samples under the same con-ditions as the standards.5. Significance and Use5.1 The total fluorine, chlorine, and sulfur contained inLPG, similar low molecular w
32、eight hydrocarbons, and DMEcan be harmful to many catalytic chemical processes, lead tocorrosion, and contribute to pollutant emissions. While LPGspecifications limit sulfur, some specifications also containprecautionary statements about fluorine. Chlorine has beenknown to contaminate LPG with detri
33、mental consequences.This test method can be used to determine total fluorine (asfluoride), chlorine (as chloride), and sulfur (as sulfate ion) inD7994 172process streams, intermediate and finished LPG products,similar low molecular weight hydrocarbons, and DME (1.1).6. Interferences6.1 Substances th
34、at co-elute with the elements (anions) ofinterest will interfere. A high concentration of one or moreelements (anions) can interfere with other constituents if theirretention times are close enough to affect the resolution of theirpeaks. The potential for interference from specific elements(anions)
35、by means of co-elution is largely dependent on themanufacturer and type of anion separation column used in theion chromatograph.6.2 Improper sample containers that react with fluorine,chlorine, or reactive sulfur species can give erroneously lowresults (Section 10).7. Apparatus7.1 LPG Sampling Syste
36、m:7.1.1 LPG Sampling Device, capable of accurately deliver-ing under pressure a known volume or aliquot of pressurizedsample, typically in the range of 5 Lto 30 L. The system andsample injection loop is swept by inert carrier gas and shall becapable of allowing the quantitative delivery of a knownal
37、iquot of pressurized sample into the oxidation zone at acontrolled rate.7.2 Pyrohydrolytic Combustion Unit:7.2.1 Furnace, an electric furnace that can maintain aminimum temperature of 900 C.7.2.2 Gas Flow Control, the apparatus shall be equippedwith flow controllers capable of maintaining a constant
38、 flow ofoxygen and inert carrier gas (argon or helium).7.2.3 Humidifier Delivery System, capable of deliveringType 1 (or better) reagent water (8.2) to the combustion tube ata controlled rate sufficient to provide a pyrohydrolytic envi-ronment.7.2.4 Pyrohydrolytic Combustion Tube, made of quartz and
39、capable of withstanding temperatures up to 1100 C. Thecombustion tube shall be of ample volume and may includequartz wool (or other suitable medium) to provide sufficientmixing and surface area to ensure complete combustion of thesample.7.3 Gas Absorption Unit:7.3.1 Gas Absorption Unit, having an ab
40、sorption tube withsufficient capacity to hold a minimum of 5 mL which isautomatically filled with a known volume of absorption solu-tion by a built-in burette or other similar device. The gasabsorption unit is interfaced to the IC and injects an aliquot ofthe absorption solution into the IC after th
41、e sample is com-busted and the by-products of combustion are absorbed. Thegas absorption unit rinses the absorption tube and the transferlines from the combustion tube to the gas absorption unit withType I reagent water (8.2) or other appropriate absorptionsolution prior to sample combustion and aft
42、er the absorptionsolution is injected into the IC to minimize cross-contamination.7.4 Ion Chromatograph:7.4.1 Ion Chromatograph (IC), (see Note 1) an analyticalsystem with all required accessories including columns, sup-pressor and detector.NOTE 1Many different companies manufacture automatic ion ch
43、ro-matographs. Consult the specific manufacturers instruction manual fordetails regarding setup and operation.7.4.2 Injection System, capable of delivering a minimum of5 L to 200 L with a precision better than 1 % or asrecommended by the manufacturer for this determination. It isrecommended to use a
44、n IC chromatograph configured forpre-concentration or matrix elimination (7.4.5) for injectionvolumes greater than 500 L.7.4.3 Pumping System, capable of delivering mobile phaseflows between 0.2 mLmin and 2.5 mLmin with a precisionbetter than 2 % or as recommended for this determination bythe manufa
45、cturer.7.4.4 Continuous Eluent Generation (Optional), to auto-matically prepare and purify the eluent used in the ionchromatography. Electrolytic eluent generation and auto-buretpreparation of eluent via in-line dilution of a stock solutionhave been found satisfactory for this test method. Othercont
46、inuous eluent generation devices may be used if theprecision, bias, recovery, and accuracy of this test method aremet.7.4.5 Anion Pre-Concentration Column (Optional), used foranion pre-concentration and matrix elimination. Pre-concentration enables larger volumes of absorbing solution(1 mL to 3 mL)
47、to be analyzed without the associated waterdip. Matrix elimination refers to the elimination of anyunreacted hydrogen peroxide in the absorbing solution prior toinjection onto the guard and anion separator columns and couldpotentially interfere with the fluoride peak resolution.7.4.6 Guard Column, f
48、or protection of the analytical columnfrom strongly retained constituents. Improved separation isobtained with additional theoretical plates.7.4.7 Anion Separator Column, capable of producing satis-factory baseline separations of the anion peaks of interest asshown in Fig. 1.7.4.8 Anion Suppressor D
49、evice, reduces the backgroundconductivity of the eluent after separation by the anionseparator column. Both chemical and continuous electrolyticsuppressors have been found satisfactory for this test method.FIG. 1 Anion Peaks of InterestD7994 173Other anion suppressor devices may be used as long as theprecision and accuracy of the method are not degraded.7.4.9 Conductivity Detector, temperature controlled to60.01 C, capable of at least 0 Scm to 1000 Scm on alinear scale.7.4.10 Data Acquisition System, an integrator or
