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00373250 PDF BRITISH STANDARD BS EN 26777 1993 BS 6068 2 16 1984 ISO 6777 1984 Incorporating Amendment No 1Water quality — Determination of nitrite — Molecular absorption spectrometric method The Euro[.]
BRITISH STANDARD Water quality — Determination of nitrite — Molecular absorption spectrometric method BS EN 26777:1993 BS 6068-2.16: 1984 ISO 6777:1984 Incorporating Amendment No The European Standard EN 26777:1993 has the status of a British Standard Confirmed July 2008 UDC 628.1/.3:620.1:543.3:546.173 BS EN 26777:1993 This British Standard, having been prepared under the direction of the Environment and Pollution Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 December 1984 © BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment 83/50175 DC ISBN 580 14203 Amendments issued since publication Amd No Date of issue Comments 7429 May 1993 Indicated by a sideline in the margin BS EN 26777:1993 Contents National foreword Foreword Scope Field of application Principle Reagents Apparatus Sampling and samples Procedure Expression of results Special cases 10 Notes on procedure 11 Test report Annex Effect of other substances on the result Table Table Table © BSI 10-1999 Page ii 3 3 4 5 5 i BS EN 26777:1993 National foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identical with ISO 6777:1984 “Water quality — Determination of nitrite — Molecular absorption spectrometric method” The International Standard was prepared by subcommittee 2, Physical, chemical and biochemical methods, of Technical Committee 147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in which the UK participated In 1993 the European Committee for Standardization (CEN) accepted ISO 6777:1984 as European Standard EN 26777:1993 As a consequence of implementing the European Standard this British Standard is renumbered as BS EN 26777 and any reference to BS 6068-2.16 should be read as a reference to BS EN 26777 This British Standard is being published in a series of Parts subdivided into Sections that will generally correspond to particular International Standards Sections are being, or will be, published in Parts to which, together with Part 0, are as follows — Part 0: Introduction; — Part 1: Glossary; — Part 2: Physical, chemical and biochemical methods; — Part 3: Radiological methods; — Part 4: Microbiological methods; — Part 5: Biological methods; — Part 6: Sampling Terminology and conventions The text of the International Standard has been approved as suitable for publication as a British Standard without deviation Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following The comma has been used as a decimal marker In British Standards it is current practice to use a full point on the baseline as the decimal marker Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard” It is current practice in British Standards for the symbol “L” to be used for litre rather than “l” and for the term “sulphur” to be used rather than “sulfur” 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 to 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 ii © BSI 10-1999 EUROPEAN STANDARD EN 26777:1993 NORME EUROPÉENNE January 1993 EUROPÄISCHE NORM UDC 628.1/.3:620.1:543.3:546.173 Descriptors: Water, quality, water testing, chemical analysis, determination of content, nitrites, molecular absorption spectrophotometry English version Water quality — Determination of nitrite — Molecular absorption spectrometric method (ISO 6777:1984) Qualité de l’eau — Dosage des nitrites — Méthode par spectrométrie d’absorption moléculaire (ISO 6777:1984) Wasserbeschaffenheit — Bestimmung von Nitrit — Spektrometrisches Verfahren (ISO 6777:1984) This European Standard was approved by CEN on 1993-01-20 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 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 language 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, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1993 Copyright reserved to CEN members Ref No EN 26777:1993 E EN 26777:1993 Foreword This European Standard is the endorsement of ISO 6777 Endorsement of ISO 6777 was recommended by Technical Committee CEN/TC 230 “Water analysis” under whose competence this European Standard will henceforth fall 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 July 1993, and conflicting national standards shall be withdrawn at the latest by July 1993 The Standard was approved and in accordance with the CEN/CENELEC Internal Regulations, 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, United Kingdom © BSI 10-1999 EN 26777:1993 Scope This International Standard specifies a molecular absorption spectrometric method for the determination of nitrite in potable, raw and waste water Field of application 2.1 Range A nitrite nitrogen concentration, ÕN, of up to 0,25 mg/l can be determined when using the maximum volume (40 ml) of test portion 2.2 Limit of detection1) When using cells of optical path length 40 mm and a test portion of 40 ml, the limit of detection has been determined to lie within the range ÕN = 0,001 to 0,002 mg/l 2.3 Sensitivity1) Using a 40 ml test portion and a cell of optical path length 40 mm, ÕN = 0,062 mg/l gives an absorbance of about 0,66 units Using a 40 ml test portion and a cell of optical path length 10 mm, ÕN = 0,25 mg/l gives an absorbance of about 0,67 units 2.4 Interferences If the alkalinity of the sample is high, some interference may be encountered (see clause 9) A range of substances often encountered in water samples has been tested for possible interference Full details are given in the Annex Of the substances tested, only chloramine, chlorine, thiosulfate sodium polyphosphate and iron(III) interfere significantly Principle Reaction of nitrite in the test portion with 4-aminobenzene sulfonamide reagent in the presence of orthophosphoric acid at pH 1,9 to form a diazonium salt which forms a pink-coloured dye with N-(1-naphthyl)-l,2-diaminoethane dihydrochloride (added with the 4-aminobenzene sulfonamide reagent) Measurement of the absorbance at 540 mm Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity 4.1 Orthophosphoric acid, 15 mol/l solution, (Õ = 1,70 g/ml) 1) Information © BSI 10-1999 4.2 Orthophosphoric acid, approximately 1,5 mol/l solution Add, by means of a pipette, 25 ml of the orthophosphoric acid (4.1) to 150 ± 25 ml of water Mix and cool to room temperature Transfer the solution to a 250 ml one-mark volumetric flask and dilute to the mark with water Store in an amber glass bottle The solution is stable for at least months 4.3 Colour reagent WARNING — This reagent is hazardous Skin contact or ingestion of it or its ingredients must be avoided Dissolve 40,0 ± 0,5 g of 4-aminobenzene sulfonamide (NH2C6H4SO2NH2) in a mixture of 100 ± ml of the orthophosphoric acid (4.1) and 500 ± 50 ml of water in a beaker Dissolve 2,00 ± 0,02 g of N-(1-naphthyl)-l,2-diaminoethane dihydrochloride (C10H7-NH-CH2-CH2-NH2.2HCl) in the resulting solution Transfer to a 1000 ml one-mark volumetric flask and dilute to the mark with water Mix well Store in an amber glass bottle The solution is stable for month if stored at to °C 4.4 Nitrite, standard solution, ÕN = 100 mg/l Dissolve 0,492 ± 0,000 g of sodium nitrite (dried at 105 °C for at least h) in about 750 ml of water Transfer quantitatively to a 000 ml one-mark volumetric flask and dilute to the mark with water Store in a stoppered amber glass bottle at to °C This solution is stable for at least month (See clause 10.) 4.5 Nitrite, standard solution, ÕN = 1,00 mg/l Transfer, by means of a pipette, 10 ml of the standard nitrite solution (4.4) to a 000 ml one-mark volumetric flask and dilute to the mark with water Prepare this solution each day as required, and discard after use Apparatus All glassware shall be carefully cleaned using approximately mol/l hydrochloric acid and then rinsed thoroughly with water Ordinary laboratory apparatus, and Spectrometer, suitable for measurements at a wavelength of 540 nm, together with cells of optical path length between 10 and 50 mm derived from a United Kingdom interlaboratory trial involving five participants EN 26777:1993 Sampling and samples Laboratory samples should be collected in glass bottles and should be analysed as soon as possible within 24 h of collection Storage of the samples at to °C may preserve many types of sample, but this should be verified Procedure 7.1 Test portion The maximum volume of test portion is 40 ml This is suitable for the determination of nitrite concentrations of up to ÕN = 0,25 mg/l Smaller test portions may be used as appropriate in order to accommodate much higher nitrite concentrations If the laboratory sample contains suspended matter, this should be allowed to settle, or the sample should be filtered through a glass fibre paper before taking the test portion 7.2 Determination Transfer, by means of a pipette, the selected volume of test portion to a 50 ml one-mark volumetric flask, and, if necessary, dilute to 40 ± ml with water NOTE It is always essential to adjust the volume to 40 ± ml to ensure that the correct pH is obtained (after addition of the reagent) for the reaction Add, by means of a pipette, 1,0 ml of the colour reagent (4.3) Mix immediately by swirling and dilute to the mark with water Mix and allow to stand The pH at this stage should be 1,9 ± 0,1 (See clause 9.) At least 20 after addition of the reagent, measure the absorbance of the solution at the wavelength of maximum absorbance, approximately 540 nm, in a cell of suitable optical path length, using water as the reference liquid NOTE The wavelength of maximum absorbance should be checked when this method is first used, and should be used in all subsequent determinations 7.3 Correction for colour If the colour of the test portion is such that it may interfere with the measurement of absorbance, treat a duplicate test portion as described in 7.2, but replacing the colour reagent (4.3) with 1,0 ml of the orthophosphoric acid solution (4.2) 7.4 Blank test Carry out a blank test by proceeding as described in 7.2, but replacing the test portion with 40 ± ml of water 7.5 Preparation of the calibration graph Place, by means of a burette, into a series of nine 50 ml one-mark volumetric flasks, the volumes of the standard nitrite solution (4.5) shown in Table Dilute the contents of each flask with water to give a volume of 40 ± ml and proceed as described in 7.2, from the second paragraph to the end, using cells of optical path length specified in Table Subtract the absorbance of the zero term from the absorbances obtained for the other standard solutions and plot a graph of absorbance against the mass of nitrite, as nitrogen, for each optical path length The graph should be linear and should pass through the origin Expression of results 8.1 Method of calculation The corrected absorbance, Ar, of the test solution is given by the equation Ar = As – Ab or, if correction for colour was made, by means of the equation Ar = As – Ab – Ac where As is the absorbance, as measured, of the test solution; Ab is the absorbance of the blank test solution; Ac is the absorbance of the solution prepared for the correction for colour NOTE It is essential that the values of As, Ab and Ac are measured in cells of the same optical path length for a particular sample From the corrected absorbance Ar, determine from the calibration graph (7.5), for the appropriate optical path length of the cell, the corresponding mass of nitrite, as nitrogen, in micrograms The nitrite content, expressed in milligrams of nitrogen per litre, is given by the formula mN -V where mN is the mass, in micrograms, of nitrite nitrogen corresponding to the corrected absorbance (Ar); V is the volume, in millilitres, of the test portion The result may be expressed as the mass concentration of nitrogen, ÕN, or nitrite, ÕNO – , in milligrams per litre, or as the amount of substance concentration of nitrite ion, c( NO– ), in micromoles per litre The appropriate conversion factors are given in Table © BSI 10-1999 EN 26777:1993 10 Notes on procedure Table Volume of standard nitrite solution (4.5) Mass of nitrite nitrogen, mN ml 0,00 0,50 1,00 1,50 2,00 2,50 5,00 7,50 10,00 a Optical path length of cell mm 4g 0,00 0,50 1,00 1,50 2,00 2,50 5,00 7,50 10,00 As standard nitrite solutions may become unstable, the concentration of the standard nitrite solution (4.4) used may be checked by the following method: Place by means of a pipette, 50 ml of potassium permanganate standard volumetric solution, c(1/5 KMnO4) = 0,01 mol/l, in a 250 ml conical flask Add 10 ± ml of 2,5 mol/l sulfuric acid solution and mix thoroughly Fill a 50 ml burette with the standard nitrite solution (4.4) and arrange the apparatus so that the tip of the burette dips below the surface of the acid permanganate solution in the flask Titrate to a colourless end-point As the end-point approaches, warm the solution to about 40 °C and continue the titration slowly until the colour of the permanganate is just discharged Note the volume of standard nitrite solution used in the titration 50 ml of a potassium permanganate standard volumetric solution, c(1/5 KMnO4) = 0,01 mol/l, is equivalent to 3,502 mg of nitrogen Thus, for the standard nitrite solution (4.4), the volume used in the titration should be 35,02 ml The standard nitrite solution is only suitable if the volume used in the titration lies within the range 35,02 ± 0,40 ml 10 and 40a 40 10 and 40 40 40 10 and 40 10 10 10 50 mm cells may also be used Table ÕN mg/l ÕN = mg/l Õ NO – = mg/l c( NO2– ) = 4mol/l 0,304 0,014 Õ NO – mg/l 3,29 0,046 c( NO2– ) 4mol/l 71,4 21,7 Example: A nitrogen concentration of mg/l corresponds to a nitrite concentration of 3,29 mg/l 11 Test report 8.2 Precision The test report shall include the following information: a) a reference to this International Standard; b) all details required for the complete identification of the sample; Special cases c) details concerning the storage of the laboratory If the alkalinity of the sample is high, such that the sample before analysis; pH is not 1,9 ± 0,1 after treating test portion and d) a statement of the repeatability achieved by diluting to 40 ml, additional orthophosphoric acid the laboratory when using this method; solution (4.2) should be added before dilution, so e) the results and the method of expression used; that the specified pH is attained The method will, f) details of any deviation from the procedure however, tolerate a hydrogen carbonate alkalinity of specified in this International Standard or any at least 300 mg/l in a test portion of 40 ml without other circumstances that may have influenced deviation from the specified pH the result Table a Repeatability and reproducibility standard deviations have been determined as indicated in Table Sample Nitrite content, Volume of test ÕN portion mg/l Standard solution Standard solution Standard solution Standard solution Sewage effluent Sea water River water 0,000 0,040 0,40 1,60 1,01 0,20 0,30 ml 40 40 40 5 40 25 mm 40 40 10 10 10 10 10 a Information derived from a United Kingdom interlaboratory trial involving b The highest and lowest values from the interlaboratory exercise All values © BSI 10-1999 Standard deviationb (mg/l) Optical path length of cell Repeatability 0,000 0,000 0,001 0,002 0,002 0,000 0,000 to 0,000 to 0,000 to 0,005 to 0,026 to 0,020 to 0,002 to 0,011 Reproducibility — 0,000 0,003 0,007 0,004 0,001 0,002 to 0,001 to 0,009 to 0,040 to 0,021 to 0,004 to 0,012 five participants have 14 degrees of freedom EN 26777:1993 Annex Effect of other substances on the result Substance Salt used Magnesium Acetate Potassium Mass of substancea 4g Effectb upon the determination of mN = 4g mN = 1,00 4g mN = 10,0 4g 000 0,00 0,00 – 0,07 Chloride 100 0,00 0,00 – 0,07 Potassium Chloride 000 0,00 – 0,03 – 0,13 Sodium Chloride 100 0,00 0,00 – 0,02 Sodium Chloride 000 0,00 – 0,01 – 0,13 Hydrogen carbonate Sodium 0,00 + 0,03 + 0,01 Hydrogen carbonate Sodium 0,00 + 0,03 + 0,06 Nitrate Potassium 000 (N) 0,00 0,00 – 0,06 Ammonium Chloride 100 (N) 0,00 – 0,01 – 0,03 Cadmium Chloride 100 0,00 – 0,03 – 0,03 Zinc Acetate 100 0,00 – 0,04 0,00 Manganese Chloride 100 0,00 + 0,04 – 0,03 Iron(III) Chloride 10 0,00 + 0,04 – 0,03 Iron(III) Chloride 100 0,00 – 0,06 – 0,51 Copper Acetate 100 – 0,06 – 0,06 – 0,07 Aluminium Sulfate 100 0,00 0,00 – 0,03 Silicate Sodium 100 (SiO2) 0,00 0,00 — Urea — 100 100 ( HCO–3 ) 200 ( HCO–3 ) 0,00 + 0,04 – 0,09 100 ( S O23 ) – 000 ( S O 23 ) 0,00 – 0,03 – 0,82 0,00 0,00 0,77 – Thiosulfate Sodium Thiosulfate Sodium Chlorine — (Cl2) 0,00 – 0,22 – 0,25 Chlorine — 20 (Cl2) – 0,01 – 1,01 – 2,81 Chloramine — (Cl2) — – 0,06 – 0,07 Chloramine — 20 (Cl2) – 0,01 – 0,30 – 2,78 100 0,00 0,00 – 0,01 Sodium polyphosphate (hexametaphosphate) 50 0,00 – 0,03 – 0,82 Sodium polyphosphate (hexametaphosphate) 500 0,00 – 0,80 – 8,10 Hydroxylammonium chloride a Mass of substance present in the test portion The mass is given as the element or compound, except where otherwise indicated in brackets b The maximum effects, assuming no interference, are as follows: 0,00 ± 0,02 4g; 1,00 ± 0,08 4g; 10,00 ± 0,14 4g (95 % confidence limit) © BSI 10-1999 blank BS EN 26777:1993 BS 6068-2.16: 1984 ISO 6777:1984 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 020 8996 9000 Fax: 020 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services Tel: 020 8996 9001 Fax: 020 8996 7001 In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service Various BSI electronic information services are also available which give details on all its products and services Contact the Information Centre Tel: 020 8996 7111 Fax: 020 8996 7048 Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards For details of these and other benefits contact Membership Administration Tel: 020 8996 7002 Fax: 020 8996 7001 Copyright Copyright subsists in all BSI publications BSI also holds the copyright, in the UK, of the publications of the international standardization bodies Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior written permission from BSI This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained BSI 389 Chiswick High Road London W4 4AL If permission is granted, the terms may include royalty payments or a licensing agreement Details and advice can be obtained from the Copyright Manager Tel: 020 8996 7070