1、Designation: D6810 07D6810 13Standard Test Method forMeasurement of Hindered Phenolic Antioxidant Content inNon-Zinc Turbine Oils by Linear Sweep Voltammetry1This standard is issued under the fixed designation D6810; the number immediately following the designation indicates the year oforiginal adop
2、tion 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 Scope*1.1 This test method covers the voltammetric determination of hindere
3、d phenol antioxidants in new or in-service non-zincturbine oils in concentrations from 0.0075 weight % up to concentrations found in new oils by measuring the amount of currentflow at a specified voltage in the produced voltammogram.1.2 The values stated in SI units are to be regarded as standard. N
4、o other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicabil
5、ity of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4378 Practice for In-Service Monitoring of Mineral Turbine Oils for Steam, Gas, and Combined Cycle Turbines
6、D6224 Practice for In-Service Monitoring of Lubricating Oil for Auxiliary Power Plant EquipmentD6447 Test Method for Hydroperoxide Number of Aviation Turbine Fuels by Voltammetric AnalysisD6971 Test Method for Measurement of Hindered Phenolic andAromaticAmineAntioxidant Content in Non-zinc Turbine O
7、ilsby Linear Sweep Voltammetry3. Summary of Test Method3.1 Ameasured quantity of sample is dispensed into a vial containing a measured quantity of alcohol-based electrolyte solutionand containing a layer of sand.When the vial is shaken, the hindered phenol antioxidants and other solution soluble oil
8、 componentspresent in the sample are extracted into the solution and the remaining droplets suspended in the solution are agglomerated by thesand. The sand/droplet suspension is allowed to settle out and the hindered phenol antioxidants dissolved in the solution arequantified by voltammetric analysi
9、s. The results are calculated and reported as weight percent of antioxidant or as millimoles(mmol) of antioxidant per litre of sample for prepared and fresh oils and as a percent remaining antioxidant for used oils.3.2 Voltammetric analysis is a technique that applies electro-analytic methods when a
10、 sample to be analyzed is mixed with anelectrolyte and a solvent and placed within an electrolytic cell. Data is obtained by measuring the current passing through the cellas a function of the potential applied, and test results are based upon current, voltage and time relationships at the cell elect
11、rodes.The cell consists of a fluid container into which is mounted a small, easily polarized working electrode, and a large nonpolarizablereference electrode. The reference electrode should be massive relative to the working electrode so that its behavior remainsessentially constant with the passage
12、 of small current; that is, it remains unpolarized during the analysis period. Additionalelectrodes, auxiliary electrodes, can be added to the electrode system to eliminate the effects of resistive drop for high resistancesolutions. In performing a voltammetric analysis, the potential across the ele
13、ctrodes is varied linearly with time, and the resultingcurrent is recorded as a function of the potential. As the increasing voltage is applied to the prepared sample within the cell, thevarious additive species under investigation within the oil are caused to electrochemically oxidize. The data rec
14、orded during this1 This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.09.0Con Oxidation of Turbine Oils.Current edition approved July 1, 2007May 1, 2013. Published August 2007May 2013. Originally
15、approved in 2002. Last previous edition approved in 20022007 asD6810-02.-07. DOI: 10.1520/D6810-07.10.1520/D6810-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to t
16、he standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes a
17、ccurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Har
18、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1oxidation reaction can then be used to determine the remaining useful life of the oil type.Atypical current-potential curve producedduring the practice of the voltammetric test can be seen by reference to Fig. 1. Initially, the
19、applied potential produces anelectrochemical reaction having a rate so slow that virtually no current flows through the cell.As the voltage is increased, as shownin Fig. 1, the electro-active species (for example, substituted phenols) begin to oxidize at the working electrode surface, producingan an
20、odic rise in the current. As the potential is further increased, the decrease in the electro-active species concentration at theelectrode surface and the exponential increase of the oxidation rate lead to a maximum in the current-potential curve shown in Fig.1.4. Significance and Use4.1 The quantita
21、tive determination of hindered phenol antioxidants in a new turbine oil measures the amount of this materialthat has been added to the oil as protection against oxidation. Beside phenols, turbine oils can be formulated with other antioxidantssuch as amines which can extend the oil life. In used oil,
22、 the determination measures the amount of original (phenolic) antioxidantremaining after oxidation have reduced its initial concentration. This test method is not designed or intended to detect all of theantioxidant intermediates formed during the thermal and oxidative stressing of the oils, which a
23、re recognized as having somecontribution to the remaining useful life of the used or in-service oil. Nor does it measure the overall stability of an oil, which isdetermined by the total contribution of all species present. Before making final judgment on the remaining useful life of the usedoil, whi
24、ch might result in the replacement of the oil reservoir, it is advised to perform additional analytical techniques (inaccordance with Practices D6224 and D4378), having the capability of measuring remaining oxidative life of the used oil.4.1.1 This test method is applicable to non-zinc turbine oils.
25、 These are refined mineral oils containing rust and oxidationinhibitors, but not antiwear additives. This test method has not yet been established with sufficient precision for antiwear oils.4.2 This test method is also suitable for manufacturing control and specification acceptance.4.3 When a volta
26、mmetric analysis is obtained for a turbine oil inhibited with a typical hindered phenol antioxidant, there is anincrease in the current of the produced voltammogram between 3-5 s (or 0.3 to 0.6 V applied voltage) (see Note 1) in the basictest solution (Fig. 1x-axis 1 second = 0.1 V). Hindered phenol
27、 antioxidants detected by voltammetric analysis include, but arenot limited to, 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butylphenol and 4,4-methylenebis(2,6-di-tert-butylphenol).NOTE 1Voltages listed with respect to reference electrode. The voltammograms shown in Figs. 1 and 2 were obtained wi
28、th a platinum referenceelectrode and a voltage scan rate of 0.1 V/s.NOTE 1x-axis = time (seconds) and y-axis is current (arbitrary units). Top line in Fig. 1 is voltammogram of a fresh R and containing 1 g of sand white quartz suitable for chromatography, within thesize range of 200 to 300 6 100 m.6
29、. Sampling6.1 Obtain the sample in accordance with Practice D4057.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the Americ
30、an Chemical Society, whereNOTE 1x-axis = time (seconds) and y-axis is current (arbitrary units). Top line in Fig. 2 is fresh oil, and lower line is used oil.FIG. 2 Amine and Hindered Phenols Peaks in the Basic Test Solution with Blank Response ZeroedD6810 133such specifications are available.3 Other
31、 grades may be used, provided it is first ascertained that the reagent is sufficiently pure topermit its use without lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise specified, references to water that conforms to Specification D1193, Type II.7.3 Analysis Materials:7.3
32、.1 Alcohol Test Solution (Basic Test Solution)Proprietary yellowYellow solution,4 ethanol solvent (1:10 distilledwater/ethanol solution)ethanol solution/distilled water) containing a dissolved base electrolyte. (WarningCorrosive, poison,flammable, skin irritant; harmful if inhaled.)7.3.2 Alcohol Cle
33、ansing Pads70 % isopropyl alcohol saturated cleansing pads.8. Procedure8.1 The voltammetric analyzer used in this test method gives linear results between 2 to 50 mmol for hindered phenols usingan oil sample size of 0.40 and 5.0 mLof the analysis solvent.The corresponding range of weight percents de
34、pends on the molecularweight of the hindered phenol and the density of the base oil. For instance, the weight % range of 0.044 to 1.1 is equal to 2 to50 mmol/L for a hindered phenol containing one hydroxyl group and with a molecular weight of 220 g/mol (2,6-di-tert-butyl-4-methylphenol) and an oil d
35、ensity of 1 g/mL. Below 2 mmol, the noise to signal ratio becomes large decreasing the accuracy ofthe measurements. For measurements below 2 mmol or for fresh oils with high noise to signal ratios, the sample size should beincreased to 0.60 mL and the volume of analysis solvent decreased to 3.0 mL.8
36、.2 General Voltammetric Test ProcedureThe test procedure for voltammetric analysis will consist of the blank reading(calibration), followed by a standard reading and finally the test sample (in-service oil) reading.8.2.1 Blank Reading(0 mmol/L = 0 weight %).8.2.1.1 DefinitionThe blank reading (volta
37、mmetric number) is a measurement of the analysis solution by itself. The blankmeasurement gives a reference number with no antioxidant present (the zero baseline).8.2.2 Standard Reading(30 to 150 mmol/Lweight % dependent on density of fresh oil and molecular weight of antioxidant).8.2.2.1 Definition
38、The standard reading is a measurement of a fresh, unused oil (containing phenolic antioxidant) mixed withan appropriate analysis solvent. This measurement gives you a voltammetric reading (standard reading) that indicates thevoltammetric response for the concentration hindered phenol antioxidant bei
39、ng analyzed for the oil being tested.8.2.3 Test Sample (In-Service Oil) Reading:8.2.3.1 DefinitionThe sample reading is a measurement of a fresh or in-service oil mixed with the same type of analysissolvent as the standard. This measurement will provide voltammetric readings that normally range betw
40、een the blank and standardmeasurements, and reflect the concentration of hindered phenol antioxidant present (fresh oil) or remaining (in-service oil) in theoil sample. Voltammetric readings for in-service oil will decrease as hindered phenol antioxidants are depleted.8.3 Voltammetric ReadingAfter t
41、he operator has selected the valleys before and after the antioxidant peaks (as shown in Fig.1), the software (R-DMS) will automatically identify and calculate the area above the baseline between the two valley indicators.This calculated area is then used for the test sample reading (in-service oil)
42、, which will be established by comparing the in-serviceoil area to its standard (see Fig. 3) and make remaining antioxidant calculations (see Section 9). If peak shifting is occurring, itis advised to repeat the voltammetric test after performing the cleaning of the electrode. If after this second t
43、est the peak shiftingremains persistent, it is advised to drag the valley indicators manually to their shifted locations.8.4 Calibration (Blank Reading) ProcedurePipette 5.0 mL of analysis solution into a 7mL vial or other suitable containercontaining 1 g of sand. Insert the electrode of the voltamm
44、etric analyzer into the analysis solution to wet the bottom surface ofthe electrode, remove, and rub dry the bottom electrode surface with a lintfree paper towel. Insert the electrode into the vial sothat the bottom of the electrode is submerged in the analysis solution without resting on the sand l
45、ayer on the bottom of the vial.Place the vial/probe upright into the rack or foam block for testing. Perform the voltammetric analysis (see 5.1). Record thevoltammetric reading in the voltage range of the phenols, 0.3 to 0.6 V (see Note 1) in basic solution and Fig. 1. Remove thecombination electrod
46、e from the blank solution and rub dry the bottom surface of the electrode with a lint free paper towel. Runat least two tests of the analysis solution to assure the electrode is clean and the minimal blank value has been obtained.8.4.1 Calibration FrequencyRecalibration with freshly prepared blank s
47、olution can be performed before each testing session,or with the use of a new batch of test solutions.8.5 Standard and In-Service Oil Sample Preparation Procedures:8.5.1 Preparing Solution StepRemove the seal and cap of the test solution vial. Pipette 5.0 mL of analysis solution into a7mL vial or ot
48、her suitable container containing 1 g of sand. Pipette 0.40 mL of the selected oil sample also into the 7mL vial.3 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Soc
49、iety, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.4 The sole source of supply of the apparatus known to the committee at this time is Fluitec International, Jersey City, NJ. If you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee,1 whichyou may attend.D6810
