1、Designation: D 5837 99 (Reapproved 2005)Standard Test Method forFuranic Compounds in Electrical Insulating Liquids by High-Performance Liquid Chromatography (HPLC)1This standard is issued under the fixed designation D 5837; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination in electricalinsulatin
3、g liquids of products 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 me
4、thod allows either liquid/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
5、 and quantified include 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 whe
6、n using thedirect injection 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 flu
7、ids.1.5 The values stated 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
8、appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 923 Practices for Sampling Electrical Insulating LiquidsD 3487 Specification for Mineral Insulating Oil Used inElectrical ApparatusD 3612 Test
9、 Method for Analysis of Gases Dissolved inElectrical Insulating Oil by Gas ChromatographyD 3613 Practice for Sampling Insulating Liquids for GasAnalysis and Determination of Water Content2.2 International Electrotechnical Commission (IEC) Stan-dard:Method 1198 Furanic Compounds Analysis in Mineral O
10、ilInsulating Oil33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 adsorbent, nthe stationary phase in solid-phaseextraction; 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
11、 extracted and thatwill be analyzed.3.1.3 liquid/liquid extraction, nthe preparative step ofextraction by mixing nonpolar 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 li
12、quid phase in an HPLCanalytical system used to transfer the prepared test specimen toand through the analytical column and 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 chromatograp
13、hy, where intermolecular inter-actions between adsorbent, solvent, and test specimen compo-nents are optimized to effect retention of analytes on a1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mi
14、ttee D27.03 on Analytical Tests.Current edition approved Oct. 1, 2005. Published November 2005. Originallyapproved in 1995. Last previous edition approved in 1999 as D 5837 99e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
15、For Annual Book 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
16、ocken, PA 19428-2959, United States.solid-phase extraction cartridge, followed by solvent elutionfrom the extraction cartridge.3.1.6 ultraviolet (UV), adjreferring to that region of theelectromagnetic spectrum including wavelengths from 10 to380 nm. The UV detectors of most HPLC systems operate inth
17、e range of wavelengths from 190 to 380 nm.4. Summary of Test Method4.1 Furanic compounds in electrical insulating 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
18、the extract or an aliquot of the oil isintroduced into an HPLC system equipped with a suitableanalytical 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
19、generated by the degradation ofcellulosic materials used in the solid insulation systems ofelectrical equipment.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
20、 compounds in oil may indicate cellulosedegradation from aging or incipient fault conditions. Testingfor furanic compounds may be used to complement dissolvedgas in oil analysis as performed in accordance with TestMethod D 3612.6. Interferences6.1 Materials used in the manufacture of the polypropyle
21、netubes and polyethylene frits of some commercially preparedsolid-phase extraction columns may interfere 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 d
22、ecay and may interfere with theaccurate determination of 5-hydroxymethyl-2- furaldehyde.6.3 The use of cellulosic filtering media may serve to adsorbfuranic compounds yielding erroneous or unreproducible re-sults, or both.7. Apparatus7.1 High-Performance Liquid Chromatograph (HPLC)The required analy
23、tical apparatus, an HPLC, consists of aninjection device with sample loop, pumping system capable ofmixing 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 r
24、ecommended that a precolumn packed with thesame material as the analytical column be used to increasecolumn 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 t
25、he mobile-phase solvents and to prevent the evolution of air bubbles.7.4 The analytical apparatus may be heated 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 controll
26、edtemperature of 30 to 40C has been found satisfactory by somelaboratories.7.5 The following range of HPLC 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 wa
27、ter/methanol gradientFlow Rate 0.5 mL/min to 1.5 mL/minColumn Temperature ambient to 40CColumn 3.9 3 300 mm C18 60 to 125A, 4 to 10 m or 4.1 3 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
28、 polytetrafluoroethylene or nylonfilter. Store water in containers shielded from light. Some laboratories use50 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 v
29、olume 20 to 30 LMobile phase acetonitrile/water gradientFlow rate, initial 0.51.0 mL/minColumn temperature ambient to 30CColumn WatersT Nova-Pak C18 Reversed Phased 300 3 3.9mm, 60A, 4 mGradient see Appendix7.7 For direct injection, a fixed wavelength between 274and 281 nm has been found to provide
30、the best chromatographyfor all compounds of interest, except furfuryl alcohol, which isbest measured with a separate 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
31、wavelength or diodearray detectors allows the selection of a specific wavelength foreach furanic compound. Each laboratory shall select thespecific wavelength to yield maximum absorbance for eachcompound as follows:Furanic Compound nm5-hydroxymethyl-2-furaldehyde 280 to 282furfuryl alcohol 215 to 22
32、02-furaldehyde 272 to 2802-acetyl furan 270 to 2805-methyl-2-furaldehyde 280 to 2927.8 After the last compound of 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 so
33、lvent ratio of the mobile phase to theinitial conditions and allow 10 to 15 min for the column tocome to equilibrium 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.
34、8.4 2-Furaldehyde99 % purity, CAS #98-01-1.8.5 Furfuryl Alcohol99 % purity, CAS #98-00-0.D 5837 99 (2005)28.6 HexaneHPLC grade.8.7 5-Hydroxymethyl-2-Furaldehyde99 % purity, CAS#67-47-0.8.8 MethanolHPLC grade.8.9 5-Methyl-2-furaldehyde99 % purity, CAS #620-02-0.8.10 Silica SPE ColumnSolid-phase extra
35、ction columnfilled with 500 mg of silica.8.11 TolueneHPLC grade.8.12 Vacuum ManifoldDevice to pull vacuum on solid-phase extraction column in order to pass sample and eluentthrough SPE column.8.13 Volumetric Test TubeTest tube designed to volu-metrically measure in 0.10-mL graduations.8.14 Vortex Mi
36、xer.8.15 WaterHPLC grade.9. Sampling9.1 Obtain test specimens (insulating fluid samples) inaccordance with the procedures for sampling in PracticesD 923 or Practice D 3613.10. Preparation of Extraction Standards in Solvent10.1 Prepare the extraction standards by dilution of aweighed standard compoun
37、d to a standard volume or byvolumetric addition of a standard compound to a standardvolume in accordance with either of the procedures describedin 10.1.1 or 10.1.2.10.1.1 Weight ProcedureWeigh out 0.100 g 6 5% ofeach of the five furanic compounds listed in this test methodand record the weight to th
38、e 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 volumetric flask. Add 199mLof either acetonitrile or methanol, using the same solvent aswas used earlier to dissolve the weighed portions of the furaniccompounds. Brin
39、g 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 mobile 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
40、 concentration. Store in a clean, dark plasticcontainer. Do not store in glass.10.1.2 Volumetric AdditionFuranic compounds that arenot liquid 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 compo
41、unds to10 mLof acetonitrile or methanol. The volumes to be added areas follows:0.83 L 6 1 % of 5-hydroxymethyl-2-furaldehyde0.88 L 6 1 % of furfuryl alcohol0.86 L 6 1 % of 2-furaldehyde0.91 L 6 1 % of 2-acetylfuran0.90 L 6 1 % of 5-methyl-2-furaldehyde10.1.2.1 These volumes represent a mass of 1000
42、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 same 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
43、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. Preparation 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 flat
44、baseline for the range of retention times for the compounds ofinterest. Mineral oil shall otherwise conform to SpecificationD 3487. Other dielectric liquids should conform with appli-cable ASTM specifications.NOTE 2The same type of dielectric liquid should be used for standardpreparation as the diel
45、ectric liquid found in the test specimen(s). This testmethod has been developed for mineral oil, but has been found to beapplicable to other dielectric fluids.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
46、 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 toluene containing furanic com-pounds to a total volume of 1 L with electrical insulating oil ofmineral origin. The solution yields a concentration o
47、f 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 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
48、 mL in toluene. Mix thoroughly so that all fivefuranic compounds are dissolved completely.11.3.2 Volumetrically dilute 1 mL of the toluene solutionfrom 11.3.1 to 1 L using electrical insulating oil of mineralorigin. This solution of furanic compounds in oil yields aconcentration of about 1 mg/L (100
49、0 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 solution. 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 o
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