BS-EN-61198-1994 IEC-61198-1993.pdf

BRITISH STANDARD BS EN 61198:1994 IEC 1198:1993 Mineral insulating oils Methods for the determination of 2-furfural and related compounds The European Standard EN 61198:1994 has the status of a British Standard UDC 621.315.615.2:610.1:543.8 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 61198:1994 This British Standard, having been prepared under the direction of the Cables and Insulation Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 June 1994 © BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference CIL/10 Draft for comment 92/03950 DC ISBN 0 580 23385 5 Cooperating organizations The European Committee for Electrotechnical Standardization (CENELEC), under whose supervision this European Standard was prepared, comprises the national committees of the following countries: AustriaItaly BelgiumLuxembourg DenmarkNetherlands FinlandNorway FrancePortugal GermanySpain GreeceSweden IcelandSwitzerland IrelandUnited Kingdom Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 61198:1994 © BSI 11-1999i Contents Page Cooperating organizationsInside front cover National forewordii Foreword2 Text of EN 611983 National annex NA (informative) Committees responsibleInside back cover National annex NB (informative) Cross-referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 61198:1994 ii © BSI 11-1999 National foreword This British Standard has been prepared under the direction of the Cables and Insulation Standards Policy Committee and is the English language version of EN 61198:1994 Mineral insulating oils Methods for the determination of 2-furfural and related compounds, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC 1198:1993 published by the International Electrotechnical Commission (IEC). WARNING. This British Standard calls for the use of substances and procedures that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 61198 March 1994 UDC 621.315.615.2:610.1:543.8 Descriptors: Liquid electrical insulating materials, mineral oils, chemical analysis, determination, furfural, extraction methods, chromatography analysis, high performance liquid, chromatography English version Mineral insulating oils Methods for the determination of 2-furfural and related compounds (IEC 1198:1993) Huiles minérales isolantes Méthodes pour la détermination du 2-furfural et ses dérivés (CEI 1198:1993) Isolieröle auf Mineralölbasis Prüfverfahren zur Bestimmung von Fur-fural und verwandten Verbindungen (IEC 1198:1993) This European Standard was approved by CENELEC on 1993-12-08. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard 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 other 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, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels © 1994 Copyright reserved to CENELEC members Ref. No. EN 61198:1994 E Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 61198:1994 © BSI 11-1999 2 Foreword The text of document 10(CO)270, as prepared by IEC Technical Committee 10: Fluids for electrotechnical applications, was submitted to the IEC-CENELEC parallel vote in October 1992. The reference document was approved by CENELEC as EN 61198 on 8 December 1993. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. In this standard, Annex A and Annex ZA are normative. Contents Page Foreword2 Introduction3 1Scope3 2Normative references3 3Sampling3 4Labelling of samples3 5Apparatus3 5.1 General equipment3 5.2 Equipment for extraction by Method A3 5.3 Equipment for extraction by Method B3 5.4 High-performance liquid chromatograph (HPLC)3 6Reagents3 7Symbols and units4 8Analytes4 9Operating procedure4 9.1 Extraction of the analytes4 9.2 Analysis of the extract4 10Calibration5 10.1 Standard solutions in oil5 10.2 Standard solution in the chromatographic eluent5 10.3 Procedure5 11Calculations5 12Report5 13Minimum level of detection6 14Precision6 14.1 Repeatability6 14.2 Reproducibility6 Annex A (normative) Checking extraction and recovery7 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications12 Figure 1 Example of suitable device for extraction with silica cartridge (method B)8 Figure 2 Examples of chromatograms recorded at two wavelengths (220 nm and 276 nm)9 Figure 3 UV spectra of the 2-furfural derivates11 latest date of publication of an identical national standard(dop) 1994-12-01 latest date of withdrawal of conflicting national standards(dow) 1994-12-01 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 61198:1994 © BSI 11-19993 Introduction The degradation of cellulosic materials constituting the solid insulation 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 used as a diagnostic tool to equipments in service and to supplement information from dissolved gas analysis. 1 Scope This International Standard specifies test 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 liquid 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 B). 2 Normative references The following normative documents contain 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 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 475:1974, Method of sampling liquid dielectrics. IEC 567:1992, Guide for the sampling of gases and of oil from off-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 with IEC 567. 5 Apparatus 5.1 General equipment: laboratory glassware; beakers or Erlenmeyer flasks; volumetric flasks; pipettes; analytical balance (0,1 mg). 5.2 Equipment for extraction by method A 25 ml glass stoppered graduated cylinder; 5 ml pipette; mechanical shaker. 5.3 Equipment for extraction by method B silica cartridges, containing about 1 g of silica with a particle size ranging from 15 4m to 100 4m. Commercially available cartridges are suitable; a vacuum device suitable to produce a slight vacuum (i.e. filter pump or vacuum manifold), see Figure 1; a 10 ml luer lock syringe; volumetric flasks, 2 ml. 5.4 High-performance liquid chromatograph (HPLC) A high-performance liquid chromatograph equipped with: pumping system suitable for at least two solvents; injection device capable of injecting 10 4l to 20 4l and suitable precision syringe (50 4l to 250 4l); 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 recommended; data 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. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 61198:1994 4 © BSI 11-1999 7 Symbols and units 8 Analytes Analytical conditions shall be suitable for the determination of the following furan derivatives: 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 analytes 9.1.1 Method A: liquid-liquid extraction Extract approximately 20 ml of oil sample, weighed to the nearest 0,1 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 until the solvent and oil layers separate completely. The extract can then be analysed as described in 9.2. NOTEThe 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 ± 0,1 g of oil sample and dissolve 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 still 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 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 volumetric flask. NOTEAnnex A describes a method to assess the efficiency of the silica cartridge. 9.2 Analysis of the extract 9.2.1 Adjust the liquid chromatograph in accordance with the manufacturers instructions and establish suitable operating conditions. 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 conditions. 9.2.3 The UV detector shall monitor the following wavelengths: 220 nm for 2-furfurylalcohol. 275 nm to 280 nm for all other compounds listed in clause 8. NOTEMaximum light absorption occurs at approximately the following wavelengths: Selection of the above wavelengths will enhance the sensitivity of the analysis for specific compounds. 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 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. FiDetector response factor for each of the analytes. Detector response for each analyte in the calibration standards (the response may be expressed by peak area or peak height). RiDetector response for each of the detected analytes. (mg·kg1) Concentration of each analyte in the calibration standards. Ci(mg·kg1) Concentration of each of the analytes in the mineral insulating oil sample. 5-hydroxymethyl-2-furfural(5HMF) 2-furfurylalcohol(2FOL) 2-furfural(2FAL) 2-acetylfuran(2ACF) 5-methyl-2-furfural(5MEF) Ri s Ci s isocratic conditions; eluent:water 60 % to 80 % in volume; methanol or acetonitrile 20 % to 40 % in volume; flow rate: 0,5 to 2,0 ml/min. NOTEIn 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. 5-hydroxymethyl-2-furfural280 nm 2-furfurylalcohol215 nm 2-furfural274 nm 2-acetylfuran272 nm 5-methyl-2-furfural288 nm Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 15:02:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 61198:1994 © BSI 11-19995 10 Calibration Standard solutions in oil are required to calibrate analyses of extracts obtained from method A. Standard solutions either in oil or in chromatographic eluent may be used with extracts prepared in accordance with method B. 10.1 Standard solutions in oil 10.1.1 Preparation of stock solution dissolve 0,025 g of each of the five compounds in 25 ml toluene (concentration 1 000 mg/l); 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. 10.1.2 Preparation of standard solutions di