《BS-EN-12014-7-1998.pdf》由会员分享,可在线阅读,更多相关《BS-EN-12014-7-1998.pdf(14页珍藏版)》请在三一文库上搜索。
1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 12014-7:1998 The Eu
2、ropean Standard EN 12014-7:1998 has the status of a British Standard ICS 67.080.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Foodstuffs Determination of nitrate and/or nitrite content Part 7: Continuous flow method for the determination of nitrate content of vegetables a
3、nd vegetable products after cadmium reduction Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 16:07:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 12014-7:1998 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Committee, was publ
4、ished under the authority of the Standards Committee and comes into effect on 15 December 1998 BSI 1998 ISBN 0 580 30044 7 Amendments issued since publication Amd. No.DateText affected National foreword This British Standard is the English language version of EN 12014-7:1998. The UK participation in
5、 its preparation was entrusted to Technical Committee AW/-/3, Food analysis Horizontal methods, which has the responsibility to: aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests
6、 informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred
7、to in this document may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or by using the Find facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract.
8、 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, the EN title page, pages 2 to 10 an inside back cove
9、r and a back cover. Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 16:07:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CEN European Committee for Standardization Comite Europe en de Normalisation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998
10、 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref. No. EN 12014-7:1998 E EUROPEAN STANDARDEN 12014-7 NORME EUROPE ENNE EUROPA ISCHE NORM June 1998 ICS 67.080.20 Descriptors: food products, vegetables, analysis methods, chemical analysis, det
11、ermination of content, nitrates, nitrites English version Foodstuffs Determination of nitrate and/or nitrite content Part 7: Continuous flow method for the determination of nitrate content of vegetables and vegetable products after cadmium reduction Produits alimentaires De termination de la teneur
12、en nitrates et/ou en nitrites Part 7: De termination de la teneur en nitrates par flux continu dans les le gumes et les produits a base de le gumes, apre s re duction au cadmium Lebensmittel Bestimmung des Nitrat- und/oder Nitritgehaltes Teil 7: Kontinuierliches Durchfluverfahren zur Bestimmung des
13、Nitratgehaltes in Gemu se und Gemu seerzeugnissen nach Cadmiumreduktion This European Standard was approved by CEN on 13 May 1998. 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 stand
14、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 CEN member. This European Standard exists in three official versions (English, French, German). A version in any other la
15、nguage made by translation under the responsibility of a CEN member into 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, Czech Republic, Denmark, Finland, France, Germany, Greece
16、, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 16:07:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 2 EN 12014-7:1998 BSI 1998 Foreword This European Standard has been pre
17、pared by Technical Committee CEN/TC 275, Food analysis Horizontal methods, the Secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 1998, and conflicting n
18、ational standards shall be withdrawn at the latest by December 1998. This series, Foodstuffs Determination of nitrates and/or nitrate content, consists of the following parts: Part 1: General considerations; Part 2: HPLC/IC method for the determination of nitrate content of vegetables and vegetable
19、products; Part 3: Spectrometric determination of nitrate and nitrite content of meat products after enzymatic reduction of nitrate to nitrite; Part 4: Ion-exchange chromatographic (IC) method for the determination of nitrate and nitrite content of meat products; Part 5: Enzymatic determination of ni
20、trate content of vegetable-containing food for babies and infants; Part 7: Continuous flow method for the determination of nitrate content of vegetables and vegetable products after cadmium reduction. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the foll
21、owing countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword2 1Scope3 2Normativ
22、e References3 3Principle3 4Reagents3 5Apparatus and equipment4 6Procedure4 7Calculation6 8Precision6 9Test Report6 Annex A (informative) Preparation of activated cadmium columns7 Annex B (informative) Figure8 Annex C (informative) Precision data9 Annex D (informative) Bibliography10 Annex E (informa
23、tive) Nitrite analysis10 Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 16:07:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 3 EN 12014-7:1998 BSI 1998 1)cis the substance concentration. 2)w is the mass fraction. 3)Polyethyleneglycol-mono p-(1,1,3,3-tetramethylbutyl)-phenyl-ether is comm
24、ercially available as Triton X 100 (pro analyse). This information is given for the convenience of users of this European Standard and does not constitute an endorsement by CEN of this product. 4)r is the mass concentration. 1 Scope This European Standard specifies a continuous flow method (CF-metho
25、d) for the determination of nitrate content of vegetables and vegetable products having a nitrate content of 900 mg/kg to 5 200 mg/kg (calculated as nitrate ion). NOTEExperiences have shown that the method may also be applied for vegetables and vegetable products having a nitrate content of greater
26、than 50 mg/kg (calculated as nitrate ion). 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated ref
27、erences, subsequent amendments to or revisions of any of these publications 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 12014-1, Foodstuffs Determination of nitrate and/or
28、nitrite content Part 1: General considerations. EN ISO 3696, Water for analytical laboratory use Specification and test methods. (ISO 3693:1987) 3 Principle Test portions are extracted with water and filtered. The filtrate is transferred to the dializer of the continuous flow (CF) system 1. An aliqu
29、ot portion of the nitrate ions diffuses in the dializing unit with a hydrophilic membrane into a slightly alkaline buffer solution in which the nitrates are reduced to nitrite by metallic cadmium. The nitrite ions react with sulfanilamide and N-1-naphthylethylenediamine to give a reddish-purple azo
30、dye. The absorbance of this dye is determined spectrometrically at a wavelength between 520 nm and 540 nm, preferably at its maximum. NOTEThe CF method is an automated version of the manual procedure for nitrate determinations in leafy vegetables as prescribed by the Official Dutch Food Act 2. With
31、the automated method the cadmium reductor may be used for a longer period of time without any appreciable loss of its reducing capacity. Also ready-made cadmium columns from commercial suppliers are available, minimizing the main objection of working with this toxic element. 4 Reagents All reagents
32、and materials used shall be of recognized analytical grade and water shall be of at least grade 1 according to EN ISO 3696. Consult safety data sheets or labels for additional information on toxicity, flammability and explosivity of chemicals used. When preparing solutions, the purities of the reage
33、nts available shall be taken into account. 4.1 Cadmium column, activated, ready-to-use, as commercially available. CAUTION Cadmium is extremely toxic for humans and the environment; take effective precautions before handling and disposing this compound. Cadmium columns may also be prepared in the la
34、boratory according to the description given in the annex A. 4.2 Hydrochloric acid, concentrated, r20(HCl) = 1,18 g/l. 4.3 Hydrochloric acid, c(HCl) = 4 mol/l1), dilute 320 ml of hydrochloric acid (4.2) to 1 l with water. 4.4 Hydrochloric acid, c(HCl) = 0,1 mol/l. 4.5 Ammonia, w(NH3) = 25 %2). 4.6 Am
35、monia, w(NH3) = 5 %. 4.7 Ammonium chloride, NH4Cl. 4.8 Wetting agent, e.g. polyethyleneglycol-mono p-(1,1,3,3-tetramethylbutyl)-phenyl-ether3)or polyethylene glycol ether. 4.9 Wetting agent solution. Dissolve 25 g of wetting agent (4.8) into 75 ml of methanol and then add 150 ml of water. 4.10 Phosp
36、horic acid, w(H3PO4) = 85 %. 4.11 Sulfanilamide, (NH2C6H4SO2NH2). 4.12 N-(1-naphthyl)ethylenediamine dihydrochloride (C10H7NHCH2CH2NH22 HCl). 4.13 Ethylenediamine tetracetic (EDTA) acid disodium salt dihydrate, (CH2N(CH2COOH) (CH2COONa)22 H2O). 4.14 Copper sulfate solution, r(CuSO45 H2O) = 2 g/100 m
37、l)4). Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 16:07:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 4 EN 12014-7:1998 BSI 1998 4.15 Extracting buffer, pH 9,6 to 9,7. Add 50 ml of hydrochloric acid (4.2) to approximately 600 ml water and mix. Add 75 ml of ammonia (4.5), dilute to 1
38、l with water and mix. Adjust to a pH of 9,6 to 9,7 with either hydrochloric acid (4.3 or 4.4) or ammonia (4.5 or 4.6). 4.16 Buffer solution continuous flow. Dissolve 25 g of ammonium chloride (4.7) in 1 l of water. Add about 5 ml of wetting agent solution (4.9) and adjust to a pH of 9,0 with ammonia
39、 (4.5 or 4.6). 4.17 Diluting solution continuous flow. Add about 5 ml of 10 % wetting agent solution (4.9) to 1 l of water. 4.18 Colour reagent continuous flow. Add 50 ml of phosphoric acid (4.10) and 5 g of sulfanilamide (4.11) to 250 ml of water. Dissolve completely and heat if necessary. Add 0,25
40、 g of N-(1-naphthyl)ethylenediamine dihydrochloride (4.12) and dilute to 500 ml with water. Store at 4 8C in a well-stoppered bottle in the dark. This solution may be kept for up to 2 weeks but it should preferably be prepared daily. 4.19 Nitrate stock solution, r(NO ) = 2 g/l. 3 2 Dissolve 0,815 g
41、of dry potassium nitrate in water and dilute with water to 250 ml in a volumetric flask. Mix well. This stock solution is stable for at least 2 months if stored at 4 8C. 4.20Nitratestandardsolutions,r(NO ) = 50 mg/l, 3 2 100 mg/l, 200 mg/l, 300 mg/l, 400 mg/l, 500 mg/l and 600 mg/l. Pipette 2,5 ml,
42、5 ml, 10 ml, 15 ml, 20 ml,25 ml and 30 ml of the nitrate stock solution (4.19) in seven subsequent 100 ml volumetric flasks. Dilute to the mark with water. Mix well. Prepare these standard solutions on the day of use. 4.21 Nitrite stock solution, r(NO ) 1 g/l. 2 2 Sodium nitrite is a hygroscopic sub
43、stance. Dissolve 0,150 g of dry sodium nitrite in water and dilute to 100 ml in a volumetric flask. Mix well. This stock solution is stable for at least 2 weeks if stored at 4 8C. 4.22 Reducing capacity control solutions, r(NO ) 2 2 = 100 mg/l, 200 mg/l and 300 mg/l. Pipette 5 ml, 10 ml and 15 ml of
44、 the nitrite stock solution (4.21) in three subsequent 50 ml volumetric flasks. Dilute to the mark with water. Mix well. Prepare these control solutions on the day of use. 4.23 Conditioner solution, r(NO ) = 10 mg/l. 3 2 Dilute 5 ml of the nitrate stock solution (4.19) to 1 l with water. Mix well. P
45、repare on the day of use. 4.24 EDTA solution, r(EDTA) = 34 g/l. Dissolve 3,4 g of the disodium dihydrate salt of EDTA (4.13) in 100 ml of water. 4.25 Regeneration solution. Add about 5 ml of EDTA solution (4.24) and 2 ml of HCl solution (4.4) to 100 ml of water. 4.26 Hypochlorite solution, w(HOCl) =
46、 0,5 %. Prepare by diluting a commercially available 5 % solution. 5 Apparatus and equipment Usual laboratory apparatus and, in particular, the following. 5.1 Laboratory cutter. 5.2 Balance or gravimetric dilutor. 5.3 Homogenizer. 5.4 Continuous flow system, consisting of sampler, tubing pump, nitra
47、te CF manifold with dialyzer, cadmium reductor, colorimeter with flowcell, filter with a wavelength of between 520 nm and 540 nm and evaluation unit (see Figure B.1). 6 Procedure 6.1 Sample preparation Store samples at a temperature of at least 218 C. Homogenize frozen vegetable samples in a cutter
48、(5.1). Keep homogenized samples and vegetable juices at a temperature of at least 218 C until just before extraction. NOTEStorage at 218 8C before homogenization is required to assure cell-breakage and complete extraction. A ruggedness study showed that extraction at room temperature is then suffici
49、ent. 6.2 Sample extraction Weigh 40,0 g of frozen and homogenized sample into a 600 ml beaker. By means of a balance or gravimetric diluter (5.2), add 35,0 g of extraction buffer (4.15) to prevent conversion of nitrate into nitrite (see note), and 325,0 g of water. Homogenize (5.3) for at least 1 min, and filter sample through fluted filter paper. Analyse the extract after filtration on the same day. Proceed as described in 6.6. NOTEAddition of extraction buffer is only needed in case nitrite is to be
链接地址:https://www.31doc.com/p-3738230.html