1、Designation: D5837 15Standard Test Method forFuranic Compounds in Electrical Insulating Liquids by High-Performance Liquid Chromatography (HPLC)1This standard is issued under the fixed designation D5837; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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 test method covers the determination in electricalinsulating liquids of products
3、 of the degradation of cellulosicmaterials such as paper, pressboard, and cotton materialstypically found as insulating materials in electrical equipment.These degradation products are substituted furan derivatives,commonly referred to as furanic compounds or furans. Thistest method allows either li
4、quid/liquid or solid phase extraction(SPE) of the furanic compounds from the sample matrixfollowed by analysis for specific furanic compounds by HPLCor direct injection for analysis of specific furanic compoundsby HPLC.1.2 The individual furanic compounds that may be identi-fied and quantified inclu
5、de the following:5-hydroxymethyl-2-furaldehydefurfuryl alcohol2-furaldehyde2-acetylfuran5-methyl-2-furaldehyde1.3 The direct injection method generally has a higher limitof detection, especially for furfuryl alcohol. Greater interfer-ence for furfuryl alcohol may be expected when using thedirect inj
6、ection method as opposed to extraction methods.1.4 This test method has been used to successfully test forfuranic compounds in mineral insulating oil, silicone fluid,high fire point electrical insulating oils of mineral origin,askarels, and perchloroethylene-based dielectric fluids.1.5 The values st
7、ated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 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 a
8、nd health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating LiquidsD3487 Specification for Mineral Insulating Oil Used inElectrical ApparatusD3612 Test Method for Analysis of
9、Gases Dissolved inElectrical Insulating Oil by Gas Chromatography2.2 International Electrotechnical Commission (IEC) Stan-dard:Method 1198 Furanic Compounds Analysis in Mineral OilInsulating Oil33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 adsorbent, nthe stationary phase i
10、n solid-phase ex-traction; silica is used as the adsorbent in this test method.3.1.2 extract, nthe liquid phase of a liquid/liquid extrac-tion containing the compound that has been extracted and thatwill be analyzed.3.1.3 liquid/liquid extraction, nthe preparative step ofextraction by mixing nonpola
11、r test specimen with polar solventto preferentially partition and concentrate polar compounds ofinterest from an insulating liquid test specimen.3.1.4 mobile phase, nthe carrier liquid phase in an HPLCanalytical system used to transfer the prepared test specimen toand through the analytical column a
12、nd detector; the composi-tion of the mobile phase affects elution time and separation ofanalytes.3.1.5 solid phase extraction (SPE), na preparative stepbased on column chromatography, where intermolecular inter-actions between adsorbent, solvent, and test specimen compo-nents are optimized to effect
13、 retention of analytes on asolid-phase extraction cartridge, followed by solvent elutionfrom the extraction cartridge.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-mittee D27.03 on Analytical Test
14、s.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1995. Last previous edition approved in 2012 as D5837 12. DOI:10.1520/D5837-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
15、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from IEC, IEC Central Office, 3 rue de Varembe, P.O. Box 131,CH-1211, Geneva 20, Switzerland.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194
16、28-2959. United States13.1.6 ultraviolet (UV), adjreferring to that region of theelectromagnetic spectrum including wavelengths from 10 to380 nm. The UV detectors of most HPLC systems operate inthe range of wavelengths from 190 to 380 nm.4. Summary of Test Method4.1 Furanic compounds in electrical i
17、nsulating liquids areextracted from a known volume of test specimen by means ofa liquid/liquid extraction or solid-phase extraction. A directinjection of the oil also may be used.4.2 A portion of the extract or an aliquot of the oil isintroduced into an HPLC system equipped with a suitableanalytical
18、 column and UV detector.4.3 Furanic compounds in the test specimen are identifiedand quantified by comparison to standards of known concen-tration.5. Significance and Use5.1 Furanic compounds are generated by the degradation ofcellulosic materials used in the solid insulation systems ofelectrical eq
19、uipment.5.2 Furanic compounds which are oil soluble to an appre-ciable degree will migrate into the insulating liquid.5.3 High concentrations or unusual increases in the concen-trations of furanic compounds in oil may indicate cellulosedegradation from aging or incipient fault conditions. Testingfor
20、 furanic compounds may be used to complement dissolvedgas in oil analysis as performed in accordance with TestMethod D3612.6. Interferences6.1 Materials used in the manufacture of the polypropylenetubes and polyethylene frits of some commercially preparedsolid-phase extraction columns may interfere
21、with the deter-mination of furanic compounds, such as furfuryl alcohol and5-hydroxymethyl-2-furaldehyde.6.2 The use of acetone in any preparative or analytical stepwill cause accelerated sample decay and may interfere with theaccurate determination of 5-hydroxymethyl-2- furaldehyde.6.3 The use of ce
22、llulosic filtering media may serve to adsorbfuranic compounds yielding erroneous or unreproducibleresults, or both.7. Apparatus7.1 High-Performance Liquid Chromatograph (HPLC)The required analytical apparatus, an HPLC, consists of aninjection device with sample loop, pumping system capable ofmixing
23、at least two solvents, reversed phase analytical column,UV detector or detectors with the ability to operate at aminimum of two wavelengths, and a data recording device orintegrator.7.2 It is recommended that a precolumn packed with thesame material as the analytical column be used to increasecolumn
24、 life and remove interferences.7.3 Helium sparging of the mobile-phase solvents is recom-mended in some cases and with some types of HPLC equip-ment to displace atmospheric gases dissolved in the mobile-phase solvents and to prevent the evolution of air bubbles.7.4 The analytical apparatus may be he
25、ated several degreesCelsius above ambient if necessary to reduce variance inanalytical results that may be caused by temperature fluctua-tions. Operation at ambient temperature or at a controlledtemperature of 30 to 40C has been found satisfactory by somelaboratories.7.5 The following range of HPLC
26、analytical conditions hasbeen found to be satisfactory for extracted test specimens(specific examples are given in the appendix):Injection Volume 15 to 30 LMobile Phase water/acetonitrile or water/methanol gradientFlow Rate 0.5 mL/min to 1.5 mL/minColumn Temperature ambient to 40CColumn 3.9 300 mm C
27、18 60 to 125A, 4 to 10 m or 4.1 150mm PRP-1 100 A, 5 to 10 mGradient see appendixNOTE 1Some laboratories have found it beneficial to filter all mobilephase solvents with a 0.45-m or smaller polytetrafluoroethylene or nylonfilter. Store water in containers shielded from light. Some laboratories use50
28、 mL of methanol added to 4 L of water to inhibit biological growth.7.6 The following HPLC analytical conditions have beenfound to be satisfactory for direct injection of the oil:Injection volume 20 to 30 LMobile phase acetonitrile/water gradientFlow rate, initial 0.51.0 mL/minColumn temperature ambi
29、ent to 30CColumn Waters Nova-Pak C18 Reversed Phased 300 3.9mm, 60A, 4 mGradient see Appendix7.7 For direct injection, a fixed wavelength between 274and 281 nm has been found to provide the best chromatographyfor all compounds of interest, except furfuryl alcohol, which isbest measured with a separa
30、te test using a wavelength between215 and 220 nm. Each furanic compound has a characteristicmaximum light absorbance occurring within the indicatedranges of wavelengths. Use of variable wavelength or diodearray detectors allows the selection of a specific wavelength foreach furanic compound. Each la
31、boratory shall select thespecific wavelength to yield maximum absorbance for eachcompound as follows:Furanic Compound nm5-hydroxymethyl-2-furaldehyde 280 to 282furfuryl alcohol 215 to 2202-furaldehyde 272 to 2802-acetyl furan 270 to 2805-methyl-2-furaldehyde 280 to 2927.8 After the last compound of
32、interest elutes through thecolumn, increase the acetonitrile or methanol to 100 % of themobile phase to remove all oil contamination remaining in theanalytical column.7.9 Readjust the solvent ratio of the mobile phase to theinitial conditions and allow 10 to 15 min for the column tocome to equilibri
33、um prior to the next injection.8. Reagents and Materials8.1 AcetonitrileHPLC grade.8.2 2-Acetylfuran99 % purity, CAS #1192-62-7.8.3 Electrical Insulating OilVirgin oil of mineral origin.D5837 1528.4 2-Furaldehyde99 % purity, CAS #98-01-1.8.5 Furfuryl Alcohol98 % purity, CAS #98-00-0.8.6 HexaneHPLC g
34、rade.8.7 5-Hydroxymethyl-2-Furaldehyde 99 % purity, CAS#67-47-0.8.8 MethanolHPLC grade.8.9 5-Methyl-2-furaldehyde98 % purity, CAS #620-02-0.8.10 Silica SPE ColumnSolid-phase extraction columnfilled with 500 mg of silica.8.11 TolueneHPLC grade.8.12 Vacuum ManifoldDevice to pull vacuum on solid-phase
35、extraction column in order to pass sample and eluentthrough SPE column.8.13 Volumetric Test TubeTest tube designed to volumetri-cally measure in 0.10-mL graduations.8.14 Vortex Mixer.8.15 WaterHPLC grade.9. Sampling9.1 Obtain test specimens (insulating fluid samples) inaccordance with the procedures
36、 for sampling in PracticesD923.10. Preparation of Extraction Standards in Solvent10.1 Prepare the extraction standards by dilution of aweighed standard compound to a standard volume or byvolumetric addition of a standard compound to a standardvolume in accordance with either of the procedures descri
37、bedin 10.1.1 or 10.1.2.10.1.1 Weight ProcedureWeigh out 0.100 g 6 5 % of eachof the five furanic compounds listed in this test method andrecord the weight to the nearest 0.1 mg. Dissolve weighedportions into 100 mL of acetonitrile or methanol. Take 1 mL ofthis solution and add to a clean 1-L volumet
38、ric flask. Add 199mLof either acetonitrile or methanol, using the same solvent aswas used earlier to dissolve the weighed portions of the furaniccompounds. Bring the solution in the volumetric flask to 1 Lwith water. Other ratios of solvent to water may be used suchas to match that of the initial mo
39、bile phase. This solution yieldsa concentration of about 1 mg/L (1000 g/L) of each of thefuranic compounds. Use the actual mass of each compound tocalculate the concentration. Store in a clean, dark plasticcontainer. Do not store in glass.10.1.2 Volumetric AdditionFuranic compounds that arenot liqui
40、d at ambient temperature should be heated to 35Cwhere all of the compounds are in a liquid state. Use a 1-Lsyringe to add the indicated volumes of furanic compounds to10 mLof acetonitrile or methanol. The volumes to be added areas follows:0.83 L 1 % of 5-hydroxymethyl-2-furaldehyde0.88 L 1 % of furf
41、uryl alcohol0.86 L 1 % of 2-furaldehyde0.91 L 1 % of 2-acetylfuran0.90 L 1 % of 5-methyl-2-furaldehyde10.1.2.1 These volumes represent a mass of 1000 g of eachof the five furanic compounds. Add 10 mL of acetonitrile ormethanol containing the dissolved volumes of furanic com-pounds to 190 mL of the s
42、ame solvent in a 1-L volumetricflask. Bring this solution to 1 L with water. Other ratios ofsolvent to water can be used such as to match that of the initialmobile phase. The resulting concentration is 1 mg/L (1000g/L) for each of the five furanic compounds. Store asindicated in 10.1.1.11. Preparati
43、on of Calibration Standards in Oil11.1 Prepare standards of furanic compounds in new dielec-tric liquid which has been tested and shown to have a flatbaseline for the range of retention times for the compounds ofinterest. Mineral oil shall otherwise conform to SpecificationD3487. Other dielectric li
44、quids should conform with applicableASTM specifications.NOTE 2The same type of dielectric liquid should be used for standardpreparation as the dielectric liquid found in the test specimen(s). This testmethod has been developed for mineral oil, but has been found to beapplicable to other dielectric f
45、luids.11.2 Volumetric Preparation:11.2.1 Use a graduated 1-Lsyringe to inject volumes of thefive furanic compounds as listed in 10.1.2 into 8 mL of toluene.Dissolve the compounds and add quantitatively to a 1-Lvolumetric flask. Make sure all compounds are thoroughlymixed.11.2.2 Dilute the 8 mL of to
46、luene containing furanic com-pounds to a total volume of 1 L with electrical insulating oil ofmineral origin. The solution yields a concentration of 1 mg/L(1000 g/L) of each of the five furanic compounds. Store asdescribed in 10.1.1.11.3 Gravimetric Preparation:11.3.1 Weigh out 0.100 g 6 5 % of each
47、 of the five furaniccompounds and record the weight to the nearest 0.1 mg.Dissolve the weighed portion in toluene and dilute volumetri-cally to 100 mL in toluene. Mix thoroughly so that all fivefuranic compounds are dissolved completely.11.3.2 Volumetrically dilute 1 mL of the toluene solutionfrom 1
48、1.3.1 to 1 L using electrical insulating oil of mineralorigin. This solution of furanic compounds in oil yields aconcentration of about 1 mg/L (1000 g/L) for each of thefuranic compounds. Use the actual mass of each compoundrecorded in 11.3.1 to calculate the exact concentration in theresulting solu
49、tion. Store as described in 10.1.1.12. Liquid/Liquid Extraction ProcedureMethod A12.1 Measure 1 to 2 mL of the extraction solvent (methanol,acetonitrile, or methanol/acetonitrile) into 10 mL of the testspecimen in a test tube and cap securely. Mix using a vortexmixer for 3 min for acetonitrile or acetonitrile/methanolextractions or for 1 to 5 min for methanol extractions. Otherratios of solvent to oil can be used as long as it is verified thatthe extraction efficiencies are unchanged.12.2 Allow the two phases to sep
