1、m 3404583 01iL0954 841 m EUROPEAN STANDARD EN 61198 NORME EUROPENNE EUROPISCHE NORM March 1994 GDC 621.315.615.2 : 610.1 : 543.8 Ikscriptors: Liquid electrical insulating materials, mineral oils, chemical analysis, determination, furfural, extraction methods, chromatography analysis, high performanc
2、e liquid, chromatography English version Mineral insulating oils - Methods for the determination of %furfural and related compounds (IEC 1198 : 1993) Huiles minrales isolantes Mthodes pour la dtermination du 2-furfural et ses drivs Verbindungen (CE1 1198 : 1993) Isolierle auf Minerallbasis Prfverfah
3、ren zur Bestimmung von Fur-fura1 und verwandten (IEC 1198 : 1993) This European Standard was approved by CENELEC on 1993-12-08. CENELEC members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national stand
4、ard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any othe
5、r language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany,
6、 Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secreta
7、riat: rue de Stassart 36, B-1050 Brussels O 1994 Copyright reserved to CENELEC members Ref. No. EN 61198 : 1994 E page 2 EN 61198 : i994 Foreword The text of document 10(C0)270, as prepared by EC chnical Committee 10: Fluids for electrotechnical applications, was submitted to the IEC-CENELEC paralle
8、l vote in October 1992. The reference document was approved by CENELEC as EN 61198 on 8 December 1993. The following dates were fixed: - latest date of publication of an identical national standard (dp) 1994- 12-0 1 - latest date of withdrawal of conflicting national standards (dw) 1994-12-01 340458
9、3 Ob30955 788 Annexes designated normative are part of the body of the standard. In this standard, annexes A and ZA are nomative. = 3404583 OLLO95b b/4 = Page 3 EN 61198 : 1994 CONTENTS INTRODUCTION Clause 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Scope Normative references . Sampling . Labelling of samples
10、. Apparatus . 5.1 General equipment . 5.2 Equipment for extraction by Method A . 5.3 Equipment for extraction by Method 6 . 5.4 High-performance liquid chromatograph (HPLC) Reagents Symbols and units . Analytes Operating procedure . 9.1 Extraction of the analytes . 9.2 Analysis of the extract Calibr
11、ation . 10.1 Standard solutions in oil 10.2 Standard solution in the chromatographic eluent . 10.3 Procedure Calculations Report Minimum level of detection . Precision 14.1 Repeatability . 14.2 Reproducibility Annex A . Checking extraction and recovery Figures . Annex ZA (normative) Other internatio
12、nal publications quoted in this standard with 4 5 5 5 5 5 5 6 6 6 6 6 7 7 7 8 8 9 9 9 10 10 10 11 11 11 12 13 the references of the relevant European publications . 17 Page 4 EN 61198 : 1994 INTRODUCTION 3404583 0330957 550 = The degradation of cellulosic materials constituting the solid insulation
13、of oil-filled electrical equipment leads to the formation of several compounds specific to cellulose decomposition, such as sugars and furan derivatives. The furan derivatives, of which a large proportion remains adsorbed on the paper, are nevertheless slightly soluble in oil. Their presence can be
14、used as a diagnostic tool to equipments in service and to supplement information from dissolved gas analysis. = 3404583 0110958 497 = Page 5 EN 61198 : 1994 MINERAL INSULATING OILS - METHODS FOR THE DETERMINATION OF 2-FURFURAL AND RELATED COMPOUNDS 1 scope This International Standard specifies test
15、methods for the analysis of 2-furfural and related furan compounds resulting from the degradation of cellulosic insulation and found in mineral insulating oil samples taken from electrical equipment. 2-furfural and related furan compounds dissolved in mineral oil are analysed by high performance liq
16、uid chromatography (HPLC). Prior to HPLC analysis, furan derivatives are extracted from the oil by use of a suitable extraction method such as liquid-liquid extraction (method A) or solid-phase separation on a silica cartridge (method 6). 2 Normative references The following normative documents cont
17、ain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication of this standard, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this International Standard
18、are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 475: 1974, Method of sampling liquid dielectrics IEC 567: 1992, Guide for the sampl
19、ing of gases and of oil from oil-filled electrical equipment and for the analysis of free and dissolved gases 3 Sampling Oil samples are collected in accordance with IEC 475 and IEC 567. Samples should be protected from direct light. 4 Labelling of samples Samples shall be labelled in accordance wit
20、h IEC 567. 5 Apparatus 5.1 General equipment: - laboratory glassware; - beakers or Erlenmeyer flasks; - volumetric flasks; - pipettes; - analytical balance (0,l mg). m 3404583 OLL0959 323 m Page 6 EN 61198 : 1994 5.2 Equipment for extraction by method A - 25 ml glass stoppered graduated cylinder; -
21、5 ml pipette; - mechanical shaker. 5.3 Equipment for extraction by method 5 - silica cartridges, containing about 1 g of silica with a particle size ranging from 15 pm to 1 O0 pm. Commercially available cartridges are suitable; - a vacuum device suitable to produce a slight vacuum (.e. filter pump o
22、r vacuum manifold), see figure 1 ; - a 10 ml luer lock syringe; - volumetric flasks, 2 ml. 5.4 High-performance liquid chromatograph (H PL C) A high-performance liquid chromatograph equipped with: - pumping system suitable for at least two solvents; - injection device capable of injecting 10 pI to 2
23、0 pI and suitable precision syringe (50 pl to 250 pl): - reversed phase column packed with octyl or octadecyl bonded silica; - pre-column packed with the same material as the analytical column (optional); - UV detector capable of recording UV spectra; a diode array UV detector is recom- mended; - da
24、ta acquisition system (recorder or integrator). 6 Reagents - HPLC grade acetonitrile; - HPLC grade methanol; - HPLC grade water; - HPLC grade acetic acid; - Analytical grade n-pentane; - Analytical grade analytes as listed in clause 8. 7 Symbols and units 5 Ri Detector response for each analyte in t
25、he calibration standards (the response may be expressed by peak area or peak height). Ri Detector response for each of the detected analytes. C: (mg -kgl) Concentration of each analyte in the calibration standards. Ci (mg-kg-) Concentration of each of the analytes in the mineral insulating oil sampl
26、e. Detector response factor for each of the analytes. D 3404583 0110760 045 D Page 7 EN 61198 : 1994 8 Analytes Analytical conditions shall be suitable for the determination of the following furan derivatives: - 5-hydroxy met hyl-2-f urfu ral (5 H M F) - 2-furfurylalcohol (2FOL) - 2-furfural (2FAL)
27、- 2-acetylfuran (2ACF) - 5-methyl-2-furfural (5MEF) For the purpose of this standard the determination of furoic acids is optional as it is often difficult to resolve them from other organic acids that may be present in aged mineral insulating oil samples. 9 Operating procedure 9.1 Extraction of the
28、 analytes 9.1.1 Method A: liquid-liquid extraction Extract approximately 20 ml of oil sample, wheighed to the nearest 0,l g, with 5 ml of acetonitrile, measured by a pipette, in a 25 ml stoppered cylinder, shaking the samples on a mechanical shaker for at least 2 min. Allow the samples to stand unti
29、l the solvent and oil layers separate completely. The extract can then be analysed as described in 9.2. NOTE - The time period necessary for phase separation tends to increase for oils with higher acid values. 9.1.2 Method B: solid-liquid extraction Weigh exactly 10 g f 0,l g of oil sample and disso
30、lve it in 10 ml analytical grade n-pentane. Rinse a new silica cartridge with 2 ml n-pentane and discard the eluate. While the silica is stili wet, immediately pass the sample solution through the cartridge under a slight vacuum at a maximum flow of 3 ml/min followed by 20 ml n-pentane. Discard all
31、eluates. Dry the cartridge by suction by maintaining the vacuum for at least 5 min. Release the vacuum and elute the retained material with the same eluent used in the first minutes of the chromatogram (see 9.2), using a 10 ml syringe as the dispenser. Collect the first two millilitres in a 2 ml vol
32、umetric flask. NOTE - Annex A describes a method to assess the efficiency of the silica cartridge. 3404583 OLLObL T81 Page 8 EN 61198 : 1994 9.2 Analysis of the extract 9.2.1 Adjust the liquid chromatograph in accordance with the manufacturers instructions and establish suitable operating conditions
33、. 9.2.2 The following set of conditions has been found satisfactory but some adjustments may be appropriate depending upon specific features of the instrumentation and local condit ions. - isocratic conditions; - eluent: water 60 % to 80 % in volume; - flow rate: 0,5 to 2,O ml/min. methanol or aceto
34、nitrile 20 % to 40 % in volume; NOTE - In some cases an elution gradient may be useful to improve the separation. Also the addition of a small amount of acetic acid (0.01 %) may improve the separation of the more polar compounds. 9.2.3 The UV detector shall monitor the following wavelengths: 220 nm
35、for 2-furfurylalcohol. 275 nm to 280 nm for all other compounds listed in clause 8. NOTE - Maximum light absorption occurs at approximately the following wavelengths: - 5-hydroxymethyl-2-furfural 280 nm - 2-furfurylalcohol 215 nm - 2-furfural 274 nm - 2-acetylfuran 272 nm - 5-methyl-2-furfural 288 n
36、m S lection of the above wavelengths will enh compounds. nc th sensitivity of th lysis for ecifi 9.2.4 When the chromatograph and detector are equilibrated inject an aliquot of the extract and record the detector response. Examples of typical chromatograms are shown in figure 2. 9.2.5 After elution
37、of the last peak of interest (5-methyl-2-furfural with specified columns) switch the mobile phase to 100 % methanol or acetonitrile and increase the flow rate until all oil residues have been flushed out of the column. 10 Calibration Standard solutions in oil are required to calibrate analyses of ex
38、tracts obtained from method A. Standard solutions either in oil or in chromatographic eluent may be used with extracts prepared in accordance with method B. W 3404583 OLL0762 918 Page 9 EN 61198 : 1994 1 O. 1 Standard solutions in oil 1 O. 1.1 - dissolve 0,025 g of each of the five compounds in 25 m
39、l toluene (concentration 1 O00 mgIl); - stock solutions shall be stored in a brown glass bottle and kept in the dark. They should be replaced at intervals of not more than three months. Preparation of stock solution 10.1.2 Preparation of standard solutions - dilute an aliquot of the toluene stock so
40、lution in a weighed amount of unused mineral insulating oil to prepare a standard solution of the desired concentration (Le. 0,5, 1 ,O, 5 or 10 mg/kg); - store in brown glass bottles and keep in the dark. NOTES 1 2 preferred. Select an appropriate mineral insulating oil which is free from species li
41、kely to interfere with the analytes. Standard solutions deteriorate rapidly if they are not properly stored. Freshly-prepared solutions are 10.2 Standard solution in the chromatographic eluent If method B is used, an alternative easier and faster calibration procedure may be used: - weigh 0,015 g of
42、 each of the five compounds; - dissolve them in 100 ml of the chromatographic eluent to obtain a stock solution of about 150 mg/l; - dilute the stock solution to obtain a standard solution of the desired concentration (i-e. 2,5, 5, 25 and 50 mg/l). NOTE - Due to the concentration factor introduced b
43、y this method, a standard solution of, for example, 5 mgll in methanoilwater is equivalent to a concentration of 1 mgkg in the oil. 10.3 Procedure Extract and analyse the standard solutions prepared in oil (10.1) following the procedures described in clause 9. Alternatively, analyse the standard sol
44、utions prepared in chromatographic eluent (1 0.2) following the procedure described in 9.2. Four standard solutions in the concentration range 0.5 to 10 mg/kg are recommended to obtain a calibration line which should normally be a straight line through the origin. Experience has indicated that for e
45、veryday routine work a single point calibration at 1 mg/kg in oil is satisfactory. NOTE - See note 2 of 10.1.2. Identify each peak in the chromatogram by its retention time and UV spectrum. For guidance, typical UV spectra are shown in figure 3 but their appearance may change slightly depending on t
46、he particular instruments. 3404583 OLL0963 854 Page 10 EN 61198 : 1994 Calculate the response factor Fi of each analyte as follows: for standard solutions in oil c: 5 =- Ri C; 5i 5 =- for standard solution in chromatographic eluent Where C: is the concentration of analyte i in the standard solution
47、mglkg (oil) s or mgll (chromatographic eluent). f?: is the response of the detector (peak area or peak height) of analyte i. 11 Calculations Identify each peak in the sample chromatogram from its retention time and UV spectrum. Measure the detector response (peak area or peak height) of each identif
48、ied peak and calculate the concentration in oil as follows: ci = 5 x Ri Where Ci is the concentration of analyte i in the oil (mg/kg oil) 6 is the response factor of analyte i R, is the detector response of the peak relative to analyte i 12 Report The report shall include the following items: - numb
49、er of this standard; - method of extraction and type of calibration used; - identification of the sample; - concentration of each analyte expressed in mg/kg to the nearest 0,Ol mg/kg. 13 Minimum level of detection Following the methods described in clause 9, the minimum concentration of the five analytes which can be determined in unused mineral oil shall be 0,05 mg/kg or lower. In considerably oxidized samples the presence of polar compounds having similar retention times to the analyes may cause uncertainties in establishing a proper baseline and then the abo
