1、BRITISH STANDARD BS EN 26777:1993 BS 6068-2.16: 1984 ISO 6777:1984 Incorporating Amendment No. 1 Water quality Determination of nitrite Molecular absorption spectrometric method The European Standard EN 26777:1993 has the status of a British Standard UDC 628.1/.3:620.1:543.3:546.173BSEN26777:1993 Th
2、is British Standard, having been prepared under the directionof the Environment andPollution Standards Committee, was published underthe authority of the BoardofBSI and comes intoeffecton 31December 1984 BSI 10-1999 The following BSI references relate to the work on this standard: Committee referenc
3、e EPC/44 Draft for comment 83/50175 DC ISBN 0 580 14203 5 Amendments issued since publication Amd. No. Date of issue Comments 7429 May 1993 Indicated by a sideline in the marginBSEN26777:1993 BSI 10-1999 i Contents Page National foreword ii Foreword 2 1 Scope 3 2 Field of application 3 3 Principle 3
4、 4 Reagents 3 5 Apparatus 3 6 Sampling and samples 4 7 Procedure 4 8 Expression of results 4 9 Special cases 5 10 Notes on procedure 5 11 Test report 5 Annex Effect of other substances on the result 6 Table 1 5 Table 2 5 Table 3 5BSEN26777:1993 ii BSI 10-1999 National foreword This Section of this B
5、ritish Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identical with ISO6777:1984 “Water quality Determination of nitrite Molecular absorption spectrometric method”. The International Standard was prepared by subcommittee2, Physical, ch
6、emical and biochemical methods, of Technical Committee147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in which the UK participated. In1993 the European Committee for Standardization (CEN) accepted ISO6777:1984 as European Standard EN26777:199
7、3. As a consequence of implementing the European Standard this British Standard is renumbered as BSEN26777 and any reference to BS6068-2.16 should be read as a reference to BS EN26777. This British Standard is being published in a series of Parts subdivided into Sections that will generally correspo
8、nd to particular International Standards. Sections are being, or will be, published in Parts1 to6 which, together with Part0, are as follows. Part0: Introduction; Part1: Glossary; Part2: Physical, chemical and biochemical methods; Part3: Radiological methods; Part4: Microbiological methods; Part5: B
9、iological methods; Part6: 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
10、 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 Stan
11、dard”. 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
12、 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, theEN title page, pages2 to6 and a back cover. This standard has been updated (
13、see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN26777:1993 January1993 UDC628.1/.3:620.1:543.3:546.173 Descriptors: Water, quality, water testing, chemical analys
14、is, determination of content, nitrites, molecular absorption spectrophotometry English version Water quality Determination of nitrite Molecular absorption spectrometric method (ISO6777:1984) Qualit de leau Dosage des nitrites Mthode par spectromtrie dabsorption molculaire (ISO6777:1984) Wasserbescha
15、ffenheit Bestimmung von Nitrit Spektrometrisches Verfahren (ISO6777:1984) This European Standard was approved by CEN on1993-01-20. 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 stand
16、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
17、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, Denmark, Finland, France, Germany, Greece, Iceland, Irela
18、nd, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1993 Copyright reserved to CEN member
19、s Ref. No. EN26777:1993 EEN26777:1993 BSI 10-1999 2 Foreword This European Standard is the endorsement of ISO6777. Endorsement of ISO6777 was recommended by Technical Committee CEN/TC230 “Water analysis” under whose competence this European Standard will henceforth fall. This European Standard shall
20、 be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by July1993, and conflicting national standards shall be withdrawn at the latest by July1993. The Standard was approved and in accordance with the CEN/CENELEC Internal Regulations
21、, 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.EN26777:1993 BSI 10-1999 3 1 Scope This International S
22、tandard specifies a molecular absorption spectrometric method for the determination of nitrite in potable, raw and waste water. 2 Field of application 2.1 Range A nitrite nitrogen concentration, N , of up to0,25mg/l can be determined when using the maximum volume (40ml) of test portion. 2.2 Limit of
23、 detection 1) When using cells of optical path length40 mm andatest portion of40 ml, the limit of detection hasbeen determined to lie within the range N= 0,001 to0,002 mg/l. 2.3 Sensitivity 1) Using a40ml test portion and a cell of optical path length40mm, N= 0,062 mg/l gives an absorbance of about0
24、,66 units. Using a40ml test portion and a cell of optical path length10mm, N= 0,25 mg/l gives an absorbance of about0,67 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
25、 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. 3 Principle Reaction of nitrite in the test portion with4-aminobenzene sulfonamide reagent in the
26、presence of orthophosphoric acid at pH1,9 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 at540mm. 4 Reagents During the analysis, use only reagents of re
27、cognized analytical grade and only distilled water or water of equivalent purity. 4.1 Orthophosphoric acid, 15 mol/l solution, ( =1,70g/ml). 4.2 Orthophosphoric acid, approximately1,5 mol/l solution. Add, by means of a pipette, 25 ml of the orthophosphoric acid (4.1) to150 25 ml of water. Mix and co
28、ol to room temperature. Transfer the solution to a250ml one-mark volumetric flask and dilute to the mark with water. Store in an amber glass bottle. The solution is stable for at least6 months. 4.3 Colour reagent WARNING This reagent is hazardous. Skin contact or ingestion of it or its ingredients m
29、ust be avoided. Dissolve40,0 0,5 g of4-aminobenzene sulfonamide (NH 2 C 6 H 4 SO 2 NH 2 ) in a mixture of100 1 ml of the orthophosphoric acid (4.1) and500 50 ml of water in a beaker. Dissolve2,00 0,02 g of N-(1-naphthyl)-l,2-diaminoethane dihydrochloride (C 10 H 7 -NH-CH 2 -CH 2 -NH 2 .2HCl) in the
30、resulting solution. Transfer to a1000ml one-mark volumetric flask and dilute to the mark with water. Mix well. Store in an amber glass bottle. The solution is stable for1 month if stored at2 to5 C. 4.4 Nitrite, standard solution, N = 100 mg/l. Dissolve0,492 2 0,000 2 g of sodium nitrite (dried at105
31、 C for at least2 h) in about750 ml of water. Transfer quantitatively to a1000 ml one-mark volumetric flask and dilute to the mark with water. Store in a stoppered amber glass bottle at2 to5 C. This solution is stable for at least1 month. (Seeclause 10.) 4.5 Nitrite, standard solution, N= 1,00 mg/l.
32、Transfer, by means of a pipette, 10ml of the standard nitrite solution (4.4) to a1000 ml one-mark volumetric flask and dilute to the mark with water. Prepare this solution each day as required, and discard after use. 5 Apparatus All glassware shall be carefully cleaned using approximately2 mol/l hyd
33、rochloric acid and then rinsed thoroughly with water. Ordinary laboratory apparatus, and Spectrometer, suitable for measurements at a wavelength of540 nm, together with cells of optical path length between10 and50 mm. 1) Information derived from a United Kingdom interlaboratory trial involving five
34、participants.EN26777:1993 4 BSI 10-1999 6 Sampling and samples Laboratory samples should be collected in glass bottles and should be analysed as soon as possible within24 h of collection. Storage of the samples at2 to5 C may preserve many types of sample, but this should be verified. 7 Procedure 7.1
35、 Test portion The maximum volume of test portion is40 ml. This is suitable for the determination of nitrite concentrations of up to N= 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 m
36、atter, 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 a50 ml one-mark volumetric flask, and, if necessary, dilute to40 2 ml with w
37、ater. NOTEIt is always essential to adjust the volume to40 2 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
38、stand. The pH at this stage should be1,9 0,1. (Seeclause 9.) At least20 min after addition of the reagent, measure the absorbance of the solution at the wavelength of maximum absorbance, approximately540 nm, in a cell of suitable optical path length, using water as the reference liquid. NOTEThe wave
39、length 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 describe
40、d in 7.2, but replacing the colour reagent (4.3) with1,0 ml of the orthophosphoric acid solution (4.2). 7.4 Blank test Carry out a blank test by proceeding as described in7.2, but replacing the test portion with40 2 ml of water. 7.5 Preparation of the calibration graph Place, by means of a burette,
41、into a series of nine50ml one-mark volumetric flasks, the volumes of the standard nitrite solution (4.5) shown in Table 1. Dilute the contents of each flask with water to give a volume of40 2 ml and proceed as described in7.2, from the second paragraph to the end, using cells of optical path length
42、specified in Table 1. 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. 8 Expres
43、sion of results 8.1 Method of calculation The corrected absorbance, A r , of the test solution is given by the equation A r= A s A b or, if correction for colour was made, by means of the equation A r = A s A b A c where NOTEIt is essential that the values of A s , A band A care measured in cells of
44、 the same optical path length for a particular sample. From the corrected absorbance A r , 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 n
45、itrogen per litre, is given by the formula where m Nis the mass, in micrograms, of nitrite nitrogen corresponding to the corrected absorbance (A r ); V is the volume, in millilitres, of the test portion. The result may be expressed as the mass concentration of nitrogen, N , or nitrite, , in milligra
46、ms per litre, or as the amount of substance concentration of nitrite ion, c(), in micromoles per litre. The appropriate conversion factors are given in Table 2. A s is the absorbance, as measured, of the test solution; A b is the absorbance of the blank test solution; A c is the absorbance of the so
47、lution prepared for the correction for colour. m N V - NO 2 NO 2EN26777:1993 BSI 10-1999 5 Table 1 Table 2 Example: A nitrogen concentration of1 mg/l corresponds to a nitrite concentration of3,29 mg/l. 8.2 Precision Repeatability and reproducibility standard deviations have been determined as indica
48、ted in Table 3. 9 Special cases If the alkalinity of the sample is high, such that the pH is not1,9 0,1 after treating test portion and diluting to40 ml, additional orthophosphoric acid solution (4.2) should be added before dilution, so that the specified pH is attained. The method will, however, to
49、lerate a hydrogen carbonate alkalinity of at least300 mg/l in a test portion of40ml without deviation from the specified pH. 10 Notes on procedure 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(1/5KMnO 4 ) = 0,01 mol/l, in a250ml conical flask. Add10 1 ml of2,5 mol/l sulfur
