1、Designation: D7328 11Standard 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 and 20 mg/kg
4、 of existent inorganicsulfate, 4.0 to 20 mg/kg of potential inorganic sulfate, and 0.75to 50 mg/kg of total inorganic chloride.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 purport to address all
5、 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. Material SafetyData Sheets are available for reagents and mater
6、ials. Reviewthem for hazards prior to usage.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 Manual Sampling of Petroleum andPetroleum ProductsD4177 Pr
7、actice 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 Techniques to Evaluate AnalyticalMeasurement System Perform
8、anceD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing LaboratoriesD7318 Test Method for Existent Inorganic Sulfate in Etha-nol by Potentiometric TitrationD7319 Test Method for Determination of Existent andPotential Sulfate and Inorganic Chloride in Fuel Ethanolby Direct I
9、njection Suppressed Ion Chromatography2.2 Other Standard:ISO/CEN15492 Ethanol as a Blending Component for Pet-rol Determination of Inorganic Chloride Ion Chro-matographic Method33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 existent inorganic sulfate, ninorganic sulfate spec
10、iesactually 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 inorganic sulfate, nsulfate species present as sulfu-ric acid, ionic salts of this acid, or mix
11、tures of these.3.1.4 potential sulfate, ntotal sulfur species present in thesample that can be oxidized to inorganic sulfate in the presenceof an oxidizing agent.4. Summary of Test Method4.1 For existent inorganic sulfate and chloride, a smallvolume of a sample is evaporated to dryness and reconstit
12、utedto the initial sample volume with deionized water, and injectedinto an ion chromatograph consisting of appropriate ionexchange columns, suppressor and a conductivity detector. Forpotential sulfate, a small volume of a sample is evaporated todryness and reconstituted to the initial sample volume
13、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 resins affinityfor the eluent. The suppressor increases the sensitivity of the1This test method is under the jurisdicti
14、on of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved July 1, 2011. Published August 2011. Originallyapproved in 2007. Last previous edition approved in 2007 as D7328071. DOI:10.1520/D7328-11
15、.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, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardizati
16、on (ISO), 1 rue deVaremb, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.method by both increasing
17、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 arequantified by integration of their responses compared with anexternal calibration curve, calculat
18、ed 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 mg/kg by mea-suring the density of the original sample.4.2 Similar methods for chloride and sulfate
19、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 Method D7318 by potentiometric lead titration.5. Significance and Use5.1 Sulfates and chlorides may b
20、e 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 potential inorganic sulfate and total chlo-ride content, as measured by this test method, can be used ason
21、e 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 retention times, especially if they are inhigh concentration compared to the analyte of interest. Sampledil
22、ution 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. Usually,for chloride and sulfate determinations, the water dip shouldnot be a problem since the chlorid
23、e 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, eluents, reagents, etc. Great care must betaken to ensure that contamination is kept at the lowest pos
24、siblelevels. 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.7.1.1 Analytical Balance, at least 100 g capacity, capable ofweighing accurately to 0.0001 g.7.2 Dryin
25、g Oven, controlled at 110 6 5C for dryingsodium sulfate and sodium chloride.7.3 Desiccator, containing freshly activated silica gel (orequivalent desiccant) with moisture content indicator.7.4 Pipettes or Volumetric Transferring Devices, Class Aglass pipettes or their equivalent of 2.0 cc capacity o
26、r auto-matic pipettes fitted with disposable polypropylene tips.7.4.1 Plastic Syringe, 10 cc disposable, 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 wi
27、th all requiredaccessories including syringes, columns, suppressor, gases, anddetector.7.6.1 Injection System, capable of delivering 25 L with aprecision better than 1 %.7.6.2 Pumping System, capable of delivering mobile phaseflows between 0.5 and 1.5 mL/min with a precision better than5%.7.6.3 Guar
28、d Column, for protection of the analytical columnfrom strongly retained constituents. Better separations areobtained with greater separating power.7.6.4 Anion Separator Column, capable of producing satis-factory analyte separation (see Fig. 1).FIG. 1 Typical Ion Chromatogram of a Solution Containing
29、 1 mg/kg of Various Anions in WaterD7328 1127.6.5 Anion Suppressor Device, micro membrane suppres-sor or equivalent. A cation exchange column in the hydrogenform has been used successfully, but it will periodically need tobe regenerated as required. This is indicated by a highbackground conductivity
30、 and low analyte response.7.6.6 Conductivity Detector, low volume (2 L) and flow,temperature compensated, capable of at least 0 to 1000 S/cmon a linear scale.7.6.7 Integrator or Chromatography Data System Software,capable of measuring peak areas and retention times, andcorrecting the data according
31、to the baseline of the chromato-gram.7.7 Gloves, powder-free examination type.7.8 Hot Block, aluminum, capable of being heated to 65Cwith suitable holes to hold 15 mL glass vials, with a method offlowing nitrogen over inserted samples.7.9 Glass Vials, 15 mL with screw top.8. Reagents8.1 Purity of Re
32、agentsReagent grade or higher puritychemicals shall be used for the preparation of all samples,standards, eluents, and regenerator solutions. Unless otherwiseindicated, it is intended that all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Socie
33、ty, 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 lessening the accuracy of the determi-nation.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be unders
34、tood to mean reagent water as definedby Type II in Specification D1193. For eluent preparation andhandling, comply with all ion chromatograph instrument andcolumn vendor requirements (for example, filtering, degassing,etc.).8.3 Eluent Buffer SolutionThe eluent solution used de-pends on the systems o
35、r 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 sodium carbonate(Na2CO3) 1.8 mM. Dissolve 2.8563 6 0.0005 g of NaHCO3and 3.8157 6 0.0005 g of Na2CO3in reagent wate
36、r 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 solution maybe prepared using appropriate ratios of reagents. Follow thespecific guidelines for this solution from the v
37、endor 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. Carefully add 13.7 mL of reagent grade sulfuricacid (relative density 1.84) to approximately 500 mL reagentwater in a 1-L volum
38、etric flask. (WarningThis will generatea very hot solution.Allow it to cool before diluting to 1000 mLvolume. Never add water to concentrated acid!) Dilute to 1000mL with reagent water, and label this solution as 0.50 Nsulfuric acid. Dilute 100 mL of this concentrate to 2000 mLwith reagent water for
39、 the final working suppressor solution.Other volumes of stock solution may be prepared usingappropriate ratios of reagents. Follow the specific guidelinesfor this solution from the vendor of the column being used.8.5 Sodium Sulfate, anhydrous, reagent grade, 99 % mini-mum purity. (WarningDo not inge
40、st; avoid unnecessaryexposure.)8.6 Sodium Chloride, ACS reagent grade, 99 % minimumpurity.8.7 Ethanol, denatured with methanol, formula 3A or his-tological grade ethanol, anhydrous, denatured with ethyl ac-etate, methylisobutyl ketone and hydrocarbon naphtha.(WarningFlammable; toxic; may be harmful
41、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, free of hydrocarbons.9. Preparation of Standard Solutions9.1 Stock Solutions:9.1.1 Sulfate Stock Solution, approximate
42、ly 2000 mg/LToensure dryness, place anhydrous sodium sulfate (5 g) in adrying oven at 110C for at least an hour, cool and store in adesiccator. Accurately weigh 2.96 g anhydrous sodium sulfateto the nearest tenth of a milligram and transfer toa1Lvolumetric flask. Add Type II water to dissolve the so
43、diumsulfate 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 ratio ofreagents.stock sulfate mg/L! 5 gNa2SO4! 0.6764! 1000 mg/g! /1L (1)where:gNa2SO4= weight in grams of Na2SO4dissolved in
44、 1 L,and0.6764 = weight percent sulfate in Na2SO4.9.1.2 Chloride Stock Solution, approximately 2000 mg/LTo ensure dryness, place sodium chloride (5 g) in a dryingoven at 110C for at least an hour, cool and store in adesiccator. Accurately weigh 3.30 g dried sodium chloride tothe nearest tenth of a m
45、illigram and transfer toa1Lvolumetricflask. Add Type II water to dissolve the sodium chloride 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 N
46、aCl! 0.6068! 1000 mg/g! /1L (2)where:g NaCl = weight in grams of NaCl dissolved in 1 L, and0.6068 = weight percent chloride in NaCl.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the Amer
47、ican Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Dorset, U.K., and the United States Pharmacopeia andNational Formulatory, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D7328 1139.2 Chloride and Sulfate Standards in WaterType II waterand sulfate and chloride
48、stock solutions are added toa1Lglassvolumetric flask according to Table 1 to achieve the desiredstandard. These standard solutions should be discarded andremade every month.9.2.1 Chloride and sulfate stock solutions from 9.1 areadded quantitatively into the flask, mixed quantitatively withType II wa
49、ter according to Table 1. Be very careful to measurethe exact volumes of the sulfate and chloride stock solutionsthat are added to the flask, and to fill the flask to 1.00 L withType II water. The sulfate and chloride concentrations of eachstandard are calculated according to Eq 3(a) and Eq 3(b).sulfate in standard mg/L!5Va 3 Ca / V a! (3)chloride in standard mg/L!5Vb 3 Cb / V b!where:Va = volume of sulfate stock solution (for example, Table1, Column 3), in mL,Ca = concentration of sulfate stock (Eq 1), in mg/L,Vb = volume of chloride stock
