1、Designation: D7328 17Standard Test Method forDetermination of Existent and Potential Inorganic Sulfateand Total Inorganic Chloride in Fuel Ethanol by IonChromatography Using Aqueous Sample Injection1This standard is issued under the fixed designation D7328; the number immediately following the desig
2、nation 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. Scope*1.1 This test method covers an ion
3、 chromatographic proce-dure for the determination of the existent inorganic andpotential sulfate and total inorganic chloride content in hydrousand anhydrous denatured ethanol to be used in motor fuelapplications. It is intended for the analysis of ethanol samplescontaining between 0.55 mg kg and 20
4、 mg kg of existentinorganic sulfate, 4.0 mg kg to 20 mg kg of potential inorganicsulfate, and 0.75 mg kg to 50 mg kg of total inorganic chlo-ride.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not pur
5、port 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Material Safety Data Sheets a
6、re available for reagents andmaterials. Review them for hazards prior to usage1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides an
7、d Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD4057 Practice for M
8、anual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD5827 Test Method for Analysis of Engine Coolant forChloride and Other Anions by Ion ChromatographyD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Te
9、chniques to Evaluate AnalyticalMeasurement System PerformanceD6792 Practice for Quality Management Systems in Petro-leum Products, Liquid Fuels, and Lubricants TestingLaboratoriesD7318 Test Method for Existent Inorganic Sulfate in Ethanolby Potentiometric TitrationD7319 Test Method for Determination
10、 of Existent and Po-tential Sulfate and Inorganic Chloride in Fuel Ethanol andButanol by Direct Injection Suppressed Ion Chromatog-raphy2.2 Other Standard:ISO/CEN15492 Ethanol as a Blending Component forPetrolDetermination of Inorganic ChlorideIon Chro-matographic Method33. Terminology3.1 Definition
11、s of Terms Specific to This Standard:3.1.1 existent inorganic sulfate, ninorganic sulfate speciesactually present in the sample at the time of analysis with nooxidation treatment.3.1.2 inorganic chloride, nchloride present as hydrochlo-ric acid, ionic salts of this acid, or mixtures of these.3.1.3 i
12、norganic sulfate, nsulfate species present as sulfu-ric acid, ionic salts of this acid, or mixtures of these.3.1.4 potential sulfate, ntotal inorganic sulfate speciespresent after the sample has been reacted with an oxidizingagent.1This test method is under the jurisdiction of ASTM Committee D02 onP
13、etroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Oct. 1, 2017. Published October 2017. Originallyapproved in 2007. Last previous edition approved in 2016 as D7328 16. DOI:10.1520/D7328-17.2For refere
14、nced 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 International Organization for Standardization (ISO), 1
15、rue deVaremb, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed
16、 in accordance with internationally recognized principles on standardization established 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.14. Summary of Test Meth
17、od4.1 For existent inorganic sulfate and chloride, a smallvolume of a sample is evaporated to dryness and reconstitutedto the initial sample volume with deionized water, and injectedinto an ion chromatograph consisting of appropriate ionexchange columns, suppressor and a conductivity detector. Forpo
18、tential sulfate, a small volume of a sample is evaporated todryness and reconstituted to the initial sample volume with0.90 % hydrogen peroxide solution in water, and injected intoan ion chromatograph. Ions are separated based on their affinityfor exchange sites of the resin with respect to the resi
19、ns affinityfor the eluent. The suppressor increases the sensitivity of themethod by both increasing the conductivity of the analytes anddecreasing the conductivity of the eluent. The suppressorconverts the eluent and the analytes to the correspondinghydrogen form acids. Anions in the aqueous sample
20、arequantified by integration of their responses compared with anexternal calibration curve, calculated as mg/L for each ion. Thecalibration standards are prepared from suitable salts dissolvedin water solutions. Existent or potential inorganic sulfate andchloride concentrations may be calculated as
21、mg/kg by mea-suring the density of the original sample.4.2 Similar methods for chloride and sulfate determinationscan be found in Test Method D5827 for engine coolant, and forethanol in ISO/CEN15492, Test Method D7319 by ion chro-matography with direct sample injection, and for sulfate onlyin Test M
22、ethod D7318 by potentiometric lead titration.5. Significance and Use5.1 Sulfates and chlorides may be found in filter pluggingdeposits and fuel injector deposits. The acceptability for use ofthe fuel components and the finished fuels depends on thesulfate and chloride content.5.2 Existent and potent
23、ial inorganic sulfate and total chlo-ride content, as measured by this test method, can be used asone measure of the acceptability of gasoline components forautomotive spark-ignition engine fuel use.6. Interferences6.1 Interferences can be caused by substances with similarion chromatographic retenti
24、on times, especially if they are inhigh concentration compared to the analyte of interest. Sampledilution or standard addition can be used to minimize orresolve most interference problems.6.2 A water dip (system void, negative peak as shown inFig. 1) may cause interference with some integrators. Usu
25、ally,for chloride and sulfate determinations, the water dip shouldnot be a problem since the chloride and sulfate peaks are farenough away from the water dip.6.3 Given the trace amounts of chloride and sulfate deter-mined by this method, interferences can be caused by contami-nation of glassware, el
26、uents, reagents, etc. Great care must betaken to ensure that contamination is kept at the lowest possiblelevels. The use of powder-free gloves is highly recommendedto prevent sample contamination.7. Apparatus7.1 Analytical Balance, at least 2000 g capacity, capable ofweighing accurately to 0.01 g.7.
27、1.1 Analytical Balance, at least 100 g capacity, capable ofweighing accurately to 0.0001 g.7.2 Drying Oven, controlled at 110 C 6 5 C for dryingsodium sulfate and sodium chloride.7.3 Desiccator, containing freshly activated silica gel (orequivalent desiccant) with moisture content indicator.7.4 Pipe
28、ttes or Volumetric Transferring Devices, Class Aglass pipettes or their equivalent of 2.0 cc capacity or auto-matic pipettes fitted with disposable polypropylene tips.FIG. 1 Typical Ion Chromatogram of a Solution Containing 1 mg/kg of Various Anions in WaterD7328 1727.4.1 Plastic Syringe, 10 cc disp
29、osable, optionally fittedwith a 0.2 m syringe filter (must be chloride and sulfate-free).7.5 Volumetric Flask, ClassAof 1 L capacity and ClassAof10 mL capacity.7.6 Ion Chromatograph, Analytical system with all requiredaccessories including syringes, columns, suppressor, gases, anddetector.7.6.1 Inje
30、ction System, capable of delivering 25 L with aprecision better than 1 %.7.6.2 Pumping System, capable of delivering mobile phaseflows between 0.5 mL min and 1.5 mL min with a precisionbetter than 5 %.7.6.3 Guard Column, for protection of the analytical columnfrom strongly retained constituents. Bet
31、ter separations areobtained with greater separating power.7.6.4 Anion Separator Column, capable of producing satis-factory analyte separation (see Fig. 1).7.6.5 Anion Suppressor Device, micro membrane suppres-sor or equivalent. A cation exchange column in the hydrogenform has been used successfully,
32、 but it will periodically need tobe regenerated as required. This is indicated by a highbackground conductivity and low analyte response.7.6.6 Conductivity Detector, low volume (2 L) and flow,temperature compensated, capable of at least 0 S cm to1000 S cm on a linear scale.7.6.7 Integrator or Chroma
33、tography Data System Software,capable of measuring peak areas and retention times, andcorrecting the data according to the baseline of the chromato-gram.7.7 Gloves, powder-free examination type.7.8 Hot Block, aluminum, capable of being heated to 65 Cwith suitable holes to hold 15 mL glass vials, wit
34、h a method offlowing nitrogen over inserted samples.7.9 Glass Vials, 15 mL with screw top.8. Reagents8.1 Purity of ReagentsReagent grade or higher puritychemicals shall be used for the preparation of all samples,standards, eluents, and regenerator solutions. Unless otherwiseindicated, it is intended
35、 that all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society, where such specifications areavailable.4Other grades may be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessenin
36、g the accuracy of the determi-nation.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water as definedby Type I in Specification D1193. For eluent preparation andhandling, comply with all ion chromatograph instrument andcolumn vendor requirements (
37、for example, filtering, degassing,etc.).8.3 Eluent Buffer SolutionThe eluent solution used de-pends on the systems or analytical columns that are used(contact instrument and column vendors). For the chromato-grams in Fig. 1, the following eluent buffer was used: Sodiumbicarbonate (NaHCO3) 1.7 mM and
38、 sodium carbonate(Na2CO3) 1.8 mM. Dissolve 2.8563 g 6 0.0005 g of NaHCO3and 3.8157 g 6 0.0005 g of Na2CO3in reagent water in a 1 LType A volumetric flask and dilute to volume. Dilute 100 mLof this concentrate to 2000 mL with reagent water for the finalworking eluent solution. Other volumes of stock
39、solution maybe prepared using appropriate ratios of reagents. Follow thespecific guidelines for this solution from the vendor of thecolumn being used. Alternatively, this solution can be pur-chased from a qualified vendor.8.4 Suppressor Solution for Membrane Suppressor, 0.025 Nsulfuric acid. Careful
40、ly add 13.7 mL of reagent grade sulfuricacid (relative density 1.84) to approximately 500 mL reagentwater in a 1 L volumetric flask. (Warning This will generatea very hot solution.Allow it to cool before diluting to 1000 mLvolume. Never add water to concentrated acid!) Dilute to1000 mL with reagent
41、water, and label this solution as 0.50 Nsulfuric acid. Dilute 100 mL of this concentrate to 2000 mLwith reagent water for the final working suppressor solution.Other volumes of stock solution may be prepared usingappropriate ratios of reagents. Follow the specific guidelinesfor this solution from th
42、e vendor of the column being used.8.5 Sodium Sulfate, anhydrous, reagent grade, 99 % mini-mum purity. (WarningDo not ingest; avoid unnecessaryexposure.)8.6 Sodium Chloride, ACS reagent grade, 99 % minimumpurity.8.7 Ethanol, denatured with methanol, formula 3A or his-tological grade ethanol, anhydrou
43、s, denatured with ethylacetate, methylisobutyl ketone and hydrocarbon naphtha.(WarningFlammable; toxic; may be harmful or fatal ifingested or inhaled; avoid skin contact.)8.8 Hydrogen Peroxide Solution, 30 %, commercially avail-able 30 % hydrogen peroxide solution.8.9 Nitrogen Gas, 99.99 mol % pure,
44、 free of hydrocarbons.9. Preparation of Standard Solutions9.1 Stock Solutions:9.1.1 Sulfate Stock Solution, approximately 2000 mg LToensure dryness, place anhydrous sodium sulfate (5 g) in adrying oven at 110 C for at least an hour, cool and store in adesiccator. Accurately weigh 2.96 g anhydrous so
45、dium sulfateto the nearest tenth of a milligram and transfer to a 1 Lvolumetric flask. Add Type II water to dissolve the sodiumsulfate and make to volume. Calculate the concentration ofsulfate in the solution according to Eq 1. Other volumes ofstock solution may be prepared using the appropriate rat
46、io ofreagents.stock sulfate mg/L! 5 gNa2SO4!0.6764!1000 mg/g!/1 L (1)4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemi
47、cals, BDH Ltd., Dorset, U.K., and the United States Pharmacopeia andNational Formulatory, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D7328 173where:gNa2SO4= weight in grams of Na2SO4dissolved in 1 L,and0.6764 = weight percent sulfate in Na2SO4.9.1.2 Chloride Stock Solution, approximate
48、ly2000 mg LTo ensure dryness, place sodium chloride (5 g) ina drying oven at 110 C for at least an hour, cool and store ina desiccator. Accurately weigh 3.30 g dried sodium chloride tothe nearest tenth of a milligram and transfer to a 1 L volumetricflask. Add Type II water to dissolve the sodium chl
49、oride andmake to volume. Calculate the concentration of chloride in thesolution according to Eq 2. Other volumes of stock solutionmay be prepared using the appropriate ratio of reagents.stock chloride mg/L! 5 g NaCl!0.6068!1000 mg/g!/1 L (2)where:g NaCl = weight in grams of NaCl dissolved in 1 L, and0.6068 = weight percent chloride in NaCl.9.2 Chloride and Sulfate Standards in WaterType II waterand sulfate and chloride stock solutions are added to a 1 Lglassvolumetric flask according to Table 1 to achieve the desireds
