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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 1785 : 1997 The Eur
2、opean Standard EN 1785 : 1996 has the status of a British Standard ICS 67.040 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Foodstuffs Detection of irradiated food containing fat Gas chromatographic/mass spectrometric analysis of 2-alkylcyclobutanones Licensed Copy: sheffiel
3、dun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 1785 : 1997 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on
4、15 June 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference AW/-/3 Draft for comment 95/500043 DC ISBN 0 580 27441 1 Amendments issued since publication Amd. No.DateText affected Committees responsible for this British Standard The preparation of this
5、British Standard was entrusted to Technical Panel AW/-/3, Food analysis Horizontal methods, upon which the following bodies were represented: Association of Public Analysts Food and Drink Federation Institute of Food Science and Technology Laboratory of the Government Chemist Ministry of Agriculture
6、, Fisheries and Food Royal Society of Chemistry Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 1785 : 1997 BSI 1997i Contents Page Committees responsibleInside front cover National forewordii Foreword2 Text of EN 17853 Licensed Copy:
7、sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 1997 BS EN 1785 : 1997 National foreword This British Standard has been prepared under the direction of Technical Panel AW/-/3 and is the English language version of EN 1785 : 1996 Foodstuffs Detection
8、 of irradiated food containing fat Gas chromatographic-mass spectrometric analysis of 2-alkylcyclobutanones, published by the European Committee for Standardization (CEN). EN 1785 was produced as a result of international discussions in which the United Kingdom took an active part. Cross-references
9、Publication referred toCorresponding British Standard EN ISO 3696 : 1995BS EN ISO 3696 : 1995 Water for analytical laboratory use. Specification and test methods Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a f
10、ront 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. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CEN European Committee for Standardization Comite Europe en de Normal
11、isation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1996 Copyright reserved to CEN members Ref. No. EN 1785 : 1996 E EUROPEAN STANDARDEN 1785 NORME EUROPE ENNE EUROPA ISCHE NORM December 1996 ICS 67.020 Descriptors: Foodstuffs, irradiated foodstuffs, i
12、onizing radiation, food analysis, detection of irradiation treatment, fat containing foodstuffs, gas chromotography, mass spectrometry English version Foodstuffs Detection of irradiated food containing fat Gas chromatographic / Mass spectrometric analysis of 2-alkylcyclobutanones Produits alimentair
13、es De tection daliments ionise s contenant des lipides Analyse par chromotographie en phase gazeuse / Spectrome trie de masse des 2-alkylcyclobutanones Lebensmittel Nachweis von bestrahlten fetthaltigen Lebensmitteln Gaschromatographisch / massenspektrometrische Untersuchung auf 2-Alkylcyclobutanone
14、 This European Standard was approved by CEN on 1996-12-05. CEN 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 referen
15、ces concerning such national standards may be obtained on application to the Central Secretariat or to any CEN 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 CEN member into
16、 its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Swi
17、tzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 2 EN 1785 : 1996 BSI 1997 Foreword This European Standard has been prepared by CEN/TC 275, Foodanalysis Horizontal methods, of which the Secretariat is held by
18、 DIN. This European Standard was elaborated on the basis of a protocol developed following a concerted action supported by the Commission of European Union (XII C.5). Experts and laboratories from EU and EFTA countries contributed jointly to the development of this protocol. This European Standard s
19、hall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 1997, and conflicting national standards shall be withdrawn at the latest by June 1997. According to the CEN/CENELEC Internal Regulations, the national standards organ
20、izations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword2 1Scope3 2Norm
21、ative references3 3Principle3 4Reagents3 5Apparatus3 6Sampling technique4 7Procedure4 8Evaluation5 9Limitations5 10Validation6 11Test report6 Annexes A(informative) Figures7 B(informative) Bibliography11 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Cop
22、y, (c) BSI Page 3 EN 1785 : 1996 BSI 1997 1) n-Hexane was the solvent used to validate the method. However, n-pentane may be used on health grounds, provided it can be shown to lead to the same result. 2)Information on reference standards is available from national standardization organizations. 3)
23、Florisilis a suitable product available commercially. This information is given for the convenience of users of this standard and does not constitute an endorsement by CEN of this product. 1 Scope This European Standard specifies a method for the identification of irradiation treatment of food conta
24、ining fat. It is based on the mass spectrometric (MS) detection of radiation-induced 2-alkylcyclobutanones after gas chromatographic (GC) separation 1 to 3. The method has been successfully tested in inter-laboratory tests on raw chicken, pork, and liquid whole egg, 4 to 6. 2 Normative references Th
25、is European Standard incorporates by dated or undated references, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publ
26、ications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN ISO 3696 : 1995Water for analytical laboratory use Specification and test methods (ISO 3696 : 1987) 3 Principle During
27、irradiation the acyl-oxygen bond in triglycerides is cleaved, and this reaction results in the formation of 2-alkylcyclobutanones containing the same number of carbon atoms as the parent fatty acid, with the alkyl group located in ring position 2. Thus, if the fatty acid composition is known, the 2-
28、alkylcyclobutanones formed can be predicted. The 2-alkylcyclobutanones which were analysed in inter-laboratory studies were 2-dodecylcyclobutanone (DCB) and 2-tetradecylcyclobutanone (TCB), which are formed from palmitic and stearic acid, respectively, during irradiation. To date, there is no eviden
29、ce that the 2-alkylcyclobutanones can be detected in unirradiated foods 4, 7 to 11. The 2-alkylcyclobutanones are extracted using n-hexane or n-pentane along with the fat. The extract is then fractionated using adsorption chromatography prior to separation using gas chromatography and detection with
30、 a mass spectrometer. The 2-alkylcyclobutanones may alternatively be detected using liquid chromatography (LC)-GC-MS coupling 12. 4 Reagents 4.1 General During analysis use only reagents of recognized analytical grade, the purity of which has to be tested regularly by analysis of reagent blank sampl
31、es. Use only water in accordance with at least grade 3 of ISO 3696. 4.2 n-Hexane1). 4.3 Sodium sulfate, anhydrous. 4.4 Diethyl ether. 4.5 Stock standard solutions, n-hexane or isooctane may be used to prepare solutions of 2-cyclohexylcyclohexanone (5 mg/ml), 2-dodecylcyclobutanone2)and 2-tetradecylc
32、yclobutanone2)(100 mg/ml). Store at 220 C. 4.6 Working standard solutions, n-hexane or isooctane may be used to prepare solutions of 2-cyclohexylcyclohexanone (0,5 mg/ml) (internal standard), 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone (10 mg/ml). Store at 220 C. 4.7 Florisil3),150 mm to 25
33、0 mm (60 mesh to 100 mesh), pesticide residue analysis grade. Before use, activate the adsorbent by heating at 550 C for at least 5 h or overnight. Cool in a desiccator. Keep well sealed after cooling. Prepare deactivated Florisilby adding 20 parts of water to 100 parts of adsorbent (m/m). Approxima
34、tely 30 g of activated Florisilis required to prepare sufficient deactivated adsorbent for each column. Ensure that the deactivated Florisilcontains no lumps and that the powder flows freely. Leave to equilibrate overnight. Use within 1 week. 4.8 Nitrogen, for concentrating solutions. 4.9 Helium, as
35、 carrier gas. 5 Apparatus Usual laboratory apparatus, and in particular the following. 5.1 Electric blender. 5.2 Soxhlet apparatus, with suitable flask of 250 ml and extractor of 100 ml. 5.3 Cellulose extraction thimbles, e.g. of length 80 mm to 100 mm, with internal diameter 30 mm. Extraction with
36、n-hexane prior to use may be necessary. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 17 08:44:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 4 EN 1785 : 1996 BSI 1997 5.4 Cotton wool, non-absorbent, washed in n-hexane prior to use. 5.5 Electric heating mantle or water bath. 5.6 Chromatogr
37、aphic tube, made of glass, having a length of 300 mm and with an internal diameter of 20 mm, fitted with a frit, a polytetrafluoroethylene (PTFE) stopcock and a ground glass joint at the top. 5.7 Separating funnel or dropping funnel, e.g. of 250 ml, with a ground glass joint. 5.8 Rotary evaporator.
38、5.9 Apparatus for concentration of solutions, under nitrogen. 5.10 Gas chromatograph (GC) glass vials. 5.11 Gas chromatograph (GC), linked to a mass spectrometer (MS). 5.12 Capillary column, with suitable performance characteristics (see annex A). 6 Sampling technique When taking samples, give prefe
39、rence to those parts of the food which have a high fat content, e.g. chicken skin. Keep the sample in a sealable glass vessel or in fat-free metal foil. 7 Procedure 7.1 Sample preparation Coarsely chop the samples of food and homogenize in an electric blender (5.1). For liquid whole egg, ensure that
40、 the sample is thoroughly mixed prior to sampling. 7.2 Fat extraction Weigh 20 g of anhydrous sodium sulfate (4.3) and 20 g of well mixed homogenized sample into an extraction thimble (5.3), mix, and plug with cotton wool (5.4). Extra sodium sulfate may be used if necessary. It is recommended that l
41、iquid egg is dried at 100 C for 12 h prior to extraction. A thin film of egg partially dried (2 h at 100 C) has given comparable results. Alternative drying procedures, e.g. freeze drying, may be used provided recovery of 2-alkylcyclobutanones is checked (see 7.6). Pour 100 ml of n-hexane (4.2) into
42、 a 250 ml flask (5.2) and place extractor on top. Place extraction thimble in the extractor and add 40 ml of n-hexane. Place the flask on the heating mantle (5.5) and condenser on top of the extractor. Reflux and extract gently for 6 h. The solvent should siphon over four times in approximately 1 h.
43、 Remove the flask from the heat, and dispose of the thimble and the n-hexane in the extractor. Transfer the solvent from the flask to the 100 ml stoppered cylinder and adjust the volume to 100 ml with more solvent. Add 5 g to 10 g of anhydrous sodium sulfate, stopper, mix, and leave overnight. NOTE.
44、 Alternative fat extraction procedures may be used if they can be shown to lead to the same results. 7.3 Determination of lipid content Dry duplicate flasks for at least 4 h or overnight at 100 C. Cool and weigh. Pipette an aliquot of lipid extract into each flask and rotary evaporate to dryness. Dr
45、y for at least 4 h or overnight at 100 C and reweigh. Alternatively, to provide a more rapid measurement of lipid content, pipette an aliquot of lipid extract into a glass vial, of which the weight has been determined. Evaporate the solvent under a stream of nitrogen. Reweigh. Repeat the process unt
46、il the weight is constant. Calculate the volume of extract required to provide approximately 200 mg of lipid. Record the exact weight of lipid applied to the column. 7.4 Florisilcolumn chromatography Prepare a Florisilcolumn (20 cm to 21 cm) using a chromatographic tube (5.6), deactivated Florisil(4
47、.7) and n-hexane (4.2). Allow the n-hexane level to drop to just above the top of the Florisil. Take a volume of the extract which provides approximately 200 mg of lipid and concentrate if necessary. The final volume should not exceed 5 ml. Apply the lipid extract, rinse the flask with approximately
48、 5 ml of n-hexane and apply to the column. Allow the n-hexane level to drop to just above the top of the Florisiland add 5 ml to 10 ml of n-hexane. Place the remaining n-hexane (150 ml in total) in the separating funnel (5.7) on top of the column, elute at 2 ml/min to 5 ml/min, and collect the eluen
49、t in a suitable 250 ml flask. When the funnel is empty (take care that the column does not run dry), change the collection flasks and elute with 150 ml of 1 % diethyl ether (4.4) in n-hexane. Rotary evaporate the 1 % diethyl ether fraction at 40 C, using minimum vacuum, to 5 ml to 10 ml, and transfer to a test tube. Concentrate to dryness under a stream of nitrogen at 40 C, ensuring that the sample is not left under nitrogen flow once it is dry. Resuspend in 200 ml of a solution of 2-cyclohexylcyclohexanone (4