1、Designation: D7922 14Standard Test Method forDetermination of Glycol for In-Service Engine Oils by GasChromatography1This standard is issued under the fixed designation D7922; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 glycolbased antifreeze for in-service engine oil by derivativeheadsp
3、ace/gas chromatography.1.2 Sample is derivatized in-situ directly in a headspacesampling vial prior to vapor phase extraction and injection intoa gas chromatograph.1.3 The chemistry of the derivatization is unique to thedetection of the molecules of ethylene glycol and 1,2-propylene glycol. 1,3-prop
4、ylene glycol could also be detectedbut is not used in any known anti-freeze at this time. Othercoolant analyses are beyond the scope of this test method.1.4 The derivatization process does not affect glycol break-down products such as glycolate and formate and hence thepresence of these compounds in
5、 the oil will not be quantified.1.5 The test method concentration range is from 50 g/g to1000 gg. Lower levels are possible by method modifications.Higher levels are possible through sample dilution.1.6 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement a
6、re included in thisstandard.1.7 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
7、prior to use.2. Referenced Documents2.1 ASTM Standards:2D4291 Test Method for Trace Ethylene Glycol in UsedEngine OilE355 Practice for Gas Chromatography Terms and Relation-shipsE594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid ChromatographyE1510 Practice for In
8、stalling Fused Silica Open TubularCapillary Columns in Gas Chromatographs3. Terminology3.1 Definitions:3.1.1 This test method makes reference to common gaschromatographic procedures, terms, and relationships. Detaileddefinitions of these can be found in Practices E355 and E594.3.1.2 antifreeze, nant
9、ifreeze is typically a dilution ofethylene glycol and possibly other glycols, and additives, inwater to act as a machine coolant. 1,2-propanediol is found insome antifreeze formulations.3.1.3 derivitization reagent, na saturated solution of phe-nylboronic acid (PBA) in solvent. Acetone and 2,2-dimet
10、hoxypropane have been used successfully. Gentle warm-ing at 50 C will hasten dissolution. Solution is stable for threemonths at room temperature if kept away from moisture.3.1.4 glycol, nthe amount, expressed as a percentage, ofglycol found in the in-service lubricating oil. The mostcommon glycol fo
11、rmulated into antifreeze is ethylene glycol(CAS# 107-21-1) with some antifreeze also containing 1,2-propanediol also known as propylene glycol (CAS# 57-55-6).Another glycol such as 1,3-propanediol (CAS# 504-63-2) isdetected by this test method but is not commonly used inantifreeze formulations.3.1.5
12、 glycols, nthe summed amount of individual glycolsfound in the in-service lubricating oil.3.1.6 in-service oil, nlubricating oil that is present in amachine that has been at operating temperature for at least 1 h.4. Summary of Test Method4.1 A representative aliquot of in-service engine oil isintrod
13、uced into a headspace sampling vial along with aderivatizing agent. The headspace vial is heated to volatilizethe derivatized glycol into the vapor phase. Using a smallaliquot of sample and derivatization reagent approaches a totalvaporization technique to minimize partition coefficient differ-ences
14、 in in-service oil samples. A representative aliquot of the1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.04.0L on Gas Chromatography Methods.Current edition approved July 15, 20
15、14. Published September 2014. DOI:10.1520/D7922-14.2For 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.Copyright
16、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1vapor sample is introduced to the gas chromatograph. Carriergas transports the vaporized aliquot through the dimethylpolysiloxane bonded phase capillary column where the glycolsare separated by th
17、e chromatographic process. The detectorsignal is processed by an electronic data acquisition system.The components are identified by comparing their retentiontimes to ones identified by analyzing standards under identicalconditions. The concentrations of all components are deter-mined by percent are
18、a by normalization of the peak areas.5. Significance and Use5.1 Some glycol/antifreeze dilution of in-service engine oilis normal under typical operating conditions. However, exces-sive glycol dilution can lead to decreased performance, prema-ture wear, or sudden engine failure. This test method pro
19、videsa means of quantifying the level of glycol based antifreezedilution, allowing the user to take necessary action.6. Interferences6.1 Glycols tend to be sticky molecules that can lead tosmall carryover into blank injections.6.2 PBA is slightly volatile and can reach the headspace(HS) injector hea
20、d and the transfer line. It is recommended toperiodically inspect a blank injection chromatogram for carryover caused by condensation of PBA in the headspace sam-pling head and/or transfer line. Several 10 L injections ofwater:methanol (50:50) through the headspace will consumeany residual derivatiz
21、ing reagent.6.3 The most common failure for this glycol method isimproperly agitated standards which allow settling of glycolsout of the oil base. Polar glycols do not stay in the non-polaroil. It is more correctly considered a suspension rather than asolution. Every oil, sample or standard, must be
22、 shaken brisklyfor 15 s to 20 s before sampling.6.4 Water/humidity reaching PBA will deactivate the PBAand inhibit derivatization of glycols. PBA will derivatize anyhydroxyl functional group. Store PBA in a desicator, never ina refrigerator.6.5 Buy PBAin small quantities to be replaced at six monthi
23、ntervals rather than larger, more cost effective quantities.6.6 Headspace carrier pressure must be higher than pressurein the heated vial to allow pressurization of the vial to aconstant pressure. This vial pressure is a function of whichsolvent is used and the thermostatting temperature of the vial
24、.A pressure of 276 kPa (40 psi) has been shown to besuccessful.6.7 Diesel fuel in the oil along with the glycols will be seenin the chromatogram. Oven conditions are chosen to minimizeco-elution of diesel peaks with the ethylene glycol. Othermedium petroleum distillates in the oil could interfere wi
25、th theethylene glycol peak but will be noticeable on the chromato-gram.6.8 Headspace vial crimp is extremely critical to completelyseal the vial.6.9 As an external standard method, measurement of oilvolume is critical and should be performed with a positivedisplacement pipette.6.10 Daily column bake
26、-out is recommended to get rid offuel and high molecular weight artifacts.6.11 Split injection has been shown to cause ethylene glycolcarryover in the injector. Therefore, direct column connectionbetween the headspace sampler and the analytical column isused.6.12 Some higher quality oils may have a
27、small quantity ofethylene glycol in the new, unused motor oil as part of the oilformulation. This concentration has been observed at about30 gg to 75 gg which is well under the level of interest of100 gg to 1000 gg. This ethylene glycol will typically boiloff in the heat of the engine. But a small l
28、evel of ethyleneglycol should not be considered as a definite coolant leakwithout considering the possibility of ethylene glycol in new orrecently topped off engine oil.7. Apparatus7.1 Gas Chromatograph (GC)The following gas chro-matographic system performance characteristics are required:7.2 Detect
29、orThis test method requires a flame ionizationdetector (FID). The detector must have sufficient sensitivity todetect 50 g/g ethylene glycol by area on the data acquisitiondevice under the conditions prescribed in this test method. Thedetector must meet or exceed the specifications as detailed inPrac
30、tice E594. The detector must be capable of operatingcontinuously at 250 C and connected to the column such thatno temperature zones below the column temperature (coldspots) exist.7.3 InjectorThe preferred injector is an automated head-space sampling device, with a direct connection of the head-space
31、 device to the analytical column without exposing thesample to a GC injector.7.4 Pneumatic ControllersThe headspace sampler and gaschromatograph must be capable of maintaining carrier gaspressure constant to 61 % for both the injector and thedetector. Most modern gas chromatographs can control carri
32、ergas in either pressure control mode or flow control mode. Thisanalysis uses isothermal oven temperature therefore constantflow control will not improve chromatographic throughput orefficiency. At isothermal oven temperatures, both pressure andflow will remain constant.7.5 Column ConditionsThis tes
33、t method utilizes a fusedsilica open tubular column with 5 % diphenyl and 95 %dimethyl polysiloxane crossbonded phase internal coatingoperating isothermally at 90 C to 140 C, depending on thecarrier gas used.7.5.1 Open tubular column with a cross bond 5 % diphenyl95 % dimethyl polysiloxane phase int
34、ernal coating, 15 m by0.32 mm I.D. with a 0.25 m film thickness. Never use a polarcolumn.7.6 Sample Introduction Devices:7.6.1 Headspace Automatic SamplerAn automatic sam-pling device for heating samples to transfer volatile compo-nents into the vapor phase and injecting a reproducible andrepresenta
35、tive aliquot of the vapor phase into the gas chro-matograph.D7922 1427.7 Electronic Data Acquisition SystemAny data acquisi-tion and integration device used for quantification of theseanalyses must meet or exceed these minimum requirements:7.7.1 Normalized percent calculations based on peak area orp
36、eak height.7.7.2 Ability to construct a first order linear regressioncalibration curve up to five levels of calibration.7.7.3 Identification of individual components based on re-tention time.7.7.4 Baseline corrections for positive or negative slopingbaseline.7.7.5 Ability to turn on and off integrat
37、ion.7.7.6 Ability to adjust integration stop and start of eachcomponent.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents o
38、f the American Chemical Society wheresuch specifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.1.1 Phenylboronic acid CAS# 98-80-6, 99+ percent pur
39、e.Used as a derivatizing reagent to convert ethylene glycol andother low molecular weight glycols to the phenylboronicderivative of the glycol.8.1.2 Ethylene glycol CAS# 107-21-1, 99+ percent pure.Used as a calibration standard for retention time and quantita-tive response by concentration.8.1.3 Pro
40、pylene glycol CAS# 57-55-6, 99+ percent pure.Also known as 1,2-propanediol. Used as a calibration standardfor retention time and quantitative response by concentration.8.1.4 1,3-propanediol CAS# 504-63-2, 99+ percent pure.Used as a calibration standard for retention time and quantita-tive response b
41、y concentration. Not essential in most antifreezeformulations. Used primarily to insure resolution of 1,2-propanediol from 1,3-propanediol.8.1.5 Acetone, CAS# 67-64-1, 99+ percent pure.(WarningExtremely flammable and toxic liquid.) One of thesolvents that can be used to dissolve the phenylboronic ac
42、id.8.1.6 2,2-dimethoxypropane CAS# 77-76-9, 99+ percentpure. (WarningExtremely flammable and toxic liquid.) Oneof the solvents that can be used to dissolve the phenylboronicacid.8.1.7 Derivitization Reagent SolutionPrepared by dissolv-ing dry phenylboronic acid into solvent such as acetone or2,2-dim
43、ethoxypropane. A high concentration or saturated so-lution is preferred. 0.5 g/mLphenylboronic acid in acetone willdissolve very slowly to overnight with agitation. A gentleheating to 50 C for 5 min will facilitate PBA into solution.Make enough volume for weekly use. Do not make largevolumes that wi
44、ll be deactivated by humidity.8.2 GasThe following compressed gases are utilized forthe operation of the gas chromatograph.8.2.1 Helium, 99.999 %. (WarningCompressed gas un-der high pressure.) This gas can be used as carrier gas. Ensuresufficient pressure for a constant carrier gas flow rate. Precis
45、ionis based on helium as the carrier gas; however, hydrogen andnitrogen have been successfully used as carrier gas.8.2.2 Hydrogen, 99.999 %. (WarningExtremely flam-mable compressed gas under high pressure.) This gas is used tosupply fuel to the flame ionization detector (FID) detector.Hydrogen is th
46、e preferred carrier. A hydrogen generator ispreferred to cylinders.8.2.3 Nitrogen, 99.999 %. (WarningCompressed gas un-der high pressure.) Used as an alternative carrier gas.8.2.4 Air(WarningCompressed gas under high pres-sure.) The gas is used to supply oxidant to the flame ionizationdetector (FID)
47、. A zero air generator is preferred.9. Preparation of Apparatus9.1 Gas Chromatograph Setup:9.1.1 Install the gas chromatograph and place into operationin accordance with the manufacturers instructions. Recom-mended operating conditions are listed in Section 7. Exampleconditions are listed in Appendi
48、x X1.9.1.2 Any injector may be used on the gas chromatograph asa firm mounting point for the automated headspace samplingdevice.9.2 Column ConditioningOpen tubular columns withcross-linked and bonded stationary phases containing 5 %diphenyl 95 % dimethyl polysiloxane are available from manymanufactu
49、rers and are usually pre-conditioned. Column con-ditioning is still recommended. The column can be conditionedvery rapidly and effectively using the following guidelinesoutlined in Practice E1510.9.3 System Performance Specification:9.3.1 Column ResolutionResolution between ethyleneglycol phenyl boronate and 1,2-propylene glycol phenyl boro-nate is required to differentiate glycols found in commonantifreeze formulations. A resolution of at least 2.0 is requiredwhere resolution is calculated by:R 5 2tr22 tr1!w11 w2! (1)where:R = resoluti
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