EN 26777-1993 en Water Quality - Determination of Nitrite - Molecular Absorption Spectrometric Method《水质 亚硝酸盐的测定 分子吸收光谱测定法》.pdf

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1、CEN ENr2b777 93 = 3404589 0047358 BOT EuRopEANmm NORME EUROPENNE EuROPISCE NOFW EN26777: 1993 January 1993 LJDC 628.U.3 : 620.1 : 543.3 : 546.173 Descriptors: Water, quaiity, water testing, chemical analysis, determination of content, nitrites, molecular absorption spectrophotometry English version

2、W 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 B

3、ritish Standard. It is current practice in British Standards for the symbol L to be used for litre rather than I and for the term sulphur to be used rather than sulfur. Compliance with a British Standard does not of itself confer immunity from legal obligations. 1 Scope CEN ENWb777 93 3404589 00471b

4、2 230 BS 6068 : Section 2.16 : 1984 3 Principle Reaction of nitrite in the test portion with 4aminobenzene 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-(l-naphthvl)-l ,2-diaminoethane dihydrochloride This Intern

5、ational Standard specifies a molecular absorption spectrometric method for the determination of in potable, raw and waste water. ,I 2 Field of application 2.1 Range A nitrite nitrogen concentration, N, of up to 0.25 mg/l can be determined when using the maximum volume (40 mi) of test portion. 2.2 Li

6、mit of detection 1) When using cells of optical path length 40 mm and a test por- tion of 40 ml, the limit of detection has been determined to lie within the range N = 0.001 to 0,002 mg/l. 2.3 Sensitivity 1) Using a 40 ml test portion and a cell of optical path length 40mm. N = 0,062 mg/l gives an a

7、bsorbance of about 0.66 units. Using a 40 ml test portion and a cell of optical path length 10 mm, Q = 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 f substances often encount

8、ered 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(llli interfere significantly. (added with the- Caminobenzene suifonamide reagent). Measurement of the

9、absorbance at 540 nm. 4 Reagents During the analysis, use only reagents of recognized analflical grade and only distilled water or water of equivalent purity. 4.1 (e = 1,7g/mli. Orthophosphoric acid, 15 mol/l solution, 4.2 tion. Add, by means of a pipette, 25 mi of the orthophosphork acid (4.1) to 1

10、50 I 2!i 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. Orthophosphoric acid, approximately 1.5 mol/l colu- Store in an amber glass bottle. The solution is stable for at least 6 months. 4.3 Colour reagent.

11、 WARNING - This reagent is hazardous. Skin contact or ingestion of it or its ingredients must be avoided. Dissolve 40.0 I 0,5 g of Caminobenzene sulfonamide (NH2GH,S02NH2) in a mixture of 100 I 1 ml of the or- thophosphoric acid (4.1 i and 500 I 50 ml of water in a beaker. Dissolve 2.00 f 0.02 g of

12、IV-( -naphthyl)-l,2-diaminoethane dihydrochloride (ClOHTNH-CH2-CH2-NH2.2HCI) in the resulting solution. Transfer to a 1 o00 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 1 month if stored at 2 to 5 OC. 1) Informat

13、ion derived from a United Kingdom interlaboratory trial involving five participants. 3 CEN ENWb777 93 m 3404589 0047Lb3 177 m BS 6068 : Section 2.16 : 1984 4.4 Nitrite, standard solution, N = 100 mg/l. Dissolve 0.492 2 f 0,OOO 2 g of sodium nitrite (dried at 105 OC for at least 2 h) in about 750 mi

14、of water. Transfer quantitatively to a 1 OOO ml one-mark volumetric flask and dilute to the mark with water. Store in a stoppered amber glass bottle at 2 to 5 OC. This solu- tion is stable for at least 1 month. (See clause 10.) Add, by means of a pipette, 1 ,O ml of the colour reagent (4.3). Mix imm

15、ediately by swirling and dilute to the mark with water. Mix and allow to stand. The pH at this stage should be 1,9 k 0.1. (See clause 9.) At least 20 min after addition of the reagent, measure the ab- sorbance of the solution at the wavelength of maximum absor- bance, approximately 540 nm, in a cell

16、 of suitable optical path length, using water as the reference liquid. 4.5 Nitrite, standard solution, eN = 1.00 mg/l. NOTE - The wavelength of maximum absorbance should be checked when this method is first used, and should be used in all subsequent determinations. Transfer, by means of a pipette, 1

17、0 ml of the standard nitrite solution (4.4) to a 1 O00 ml one-mark volumetric flask and dilute to the mark with water. 7.3 Correction for colour prepare this soution each day as required, and discard after If the ColOur Of the teCt mion is such that it IIWy interfere With use. the measurement of abs

18、orbance, treat a duplicate test portion as described in 7.2, but replacing the colour reagent (4.3) with 1 ,O ml of the orthophosphoric acid solution (4.2). 5 Apparatus 7.4 Blank test All glassware shall be carefully cleaned using approximately 2 mol/l hydrochloric acid and then rinsed thoroughly wi

19、th water. Carry Out a blank test bV Proceeding as described in 7.2, but replacing the test portion with 40 f 2 ml of water. Ordinary laboratory apparatus, and 7.5 Preparation of the calibration graph Spectrometer, suitable for measurements at a wavelength of 540 nm, together with cells of optical pa

20、th length between 10 and 50 mm. Place, bY means Of a burette. into a series of nine 50 ml one- mark VOUmetflC flasks, the Volumes Of the standard nitrite Solu- tion (4.5) shown in table 1. Dilute the contents of each flask with water to give a volume of 40 f 2 mi and proceed as described in 7.2, fro

21、m the second paragraph to the end, using cells of optical path length 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 6 Sampling and samples

22、 Laboratory samples should be collected in glass bottles and should be analysed as soon as possible within 24 h of collec- tion. Storage of the samples at 2 to 5 OC may preserve many types of sample, but this should be verified. D 7 Procedure optical path length. The graph should be linear and shoul

23、d pass through the origin. 7.1 Test portion 8 Expression of results 8.1 Method of calculation The maximum volume of test portion is 40 ml. This is suitable for the determination of nitrite concentrations of up to eN = q/* portions may be used as ap propriate in order to accommodate much higher nitri

24、te concen- trations. If the laboratory sample contains suspended matter, The corrected absorbance, A, of the test solution is given by the equation A, = A, - Ab this should be allowed to settle or the sample should be filtered through a glass fibre paper before taking the test portion. or, if correc

25、tion for colour was made, by means of the equation 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 i 2 ml with water. NOTE - it is always essential to adjust the volume to 40 I 2 ml to en- su

26、re that the correct pH is obtained (after addition of the reagent) for the reaction. rection for colour. where A, is the absorbance, as measured, of the test solution; A, is the absorbance of the blank test solution; A, is the absorbance of the solution prepared for the cor- 4 - CEN ENx26777 93 3404

27、589 0047364 003 Volume of standard nitrite solution (4.51 ml 0.00 O. 50 1 a00 1,s 2.00 5.00 7.50 10.00 2.50 NOTE - It is essential that the values of A, A, and A, are measured in cells of the same optical path length for a particular sample. Mass of nitrite nitrogen. m, Optical path length of cell c

28、is mm 0.00 10 and 40. 0.50 40 1 .o0 10 and 40 1,50 40 200 40 5.00 10 7.50 10 10,00 10 2.50 10 anci 40 From the corrected absorbance A, determine from the calibra- tion graph (7.5). for the appropriate optical path length of the cell, the corresponding mass of nitrite, as nitrogen, in micrograms. The

29、 nitrite content, expressed in milligram of nitrogen per litre. is given by the formula where mN is the mass, in micrograms. of nitrite nitrogen cor- responding to the corrected absorbance (A,); V is the volume, in millilitres, of the test portion. The result may be expressed as the mass concentrati

30、on of nitrogen, Q, or nitrite, N% in milligrams per litre, or as the BS 6068 : Section 2.16 : 1984 amount of substance concentration of nitrite ion, dNO;), in micromoles per litre. The appropriate conversion factors are given in table 2. Table 2 I N QN$ dNOJ QN$ = 1 mg/l 0,304 21.7 0,014 0.M CINO;)

31、= 1 pmolll Exampie: A nitrogen concentration of 1 mgfl corresponds to a nitrite concentration of 3.29 mgil. 8.2 Precision Repeatability and reproducibility standard deviations have been detmined as indicated in table 3. CEN ENWb777 93 3404589 0047Lb5 T4T = BS 6068 : Section 2.16 : 1984 0.20 0.30 Tab

32、le 3* 40 25 Sample . Standard solution Standard solution Standard solution Standard solution Sewage effluent Sea water River water Nitrite content, Volume of QN I test portion Q 0.40 1 .a 1 ,o1 I 5 5 Optical path length of cell mm 40 40 10 10 10 10 10 Standard deviation (mglll Repeatability 0,ooO 1

33、to 0,ooO 3 0,ooO 2 to 0,ooO 8 0.001 1 to 0.005 4 0.002 to 0,026 0.002 to 0,020 0,ooD 3 to 0,002 6 0,ooO 8 to 0,011 6 Information derived from a United Kingdom interlaboratory trial involving five participants. * The highest and lowest values from the interlaboratory exercise. All values have 14 degr

34、ees of freedom. 9 Special cases If the alkalinity of the sample is high, such that the pH is not 1,9 f O, 1 after treating test portion and diluting to 40 ml, addi- tional orthophosphoric acid solution (4.2) should be added before dilution, so that the specified pH is attained. The method will, howe

35、ver, tolerate a hydrogen carbonate alkalinity of at least 300 mg/l in a test portion of 40 ml without deviation from the specified pH. 10 Notes on procedure As standard nitrite solutions may become unstable, the con- centration of the standard nitrite solution (4.41 used may be checked by the follow

36、ing method : Place by means of a pipette, 50 ml of potassium permanganate standard volumetric solution, c(1/5 KMn04) = 0,Ol mol/l, in a 250 ml conical flask. Add 10 f 1 ml of 2.5 ml/l sulfuric acid solution and mix thoroughly. Fill a 50 ml burette with the stan- dard nitrite solution (4.4) and arran

37、ge the apparatus so that the tip of the burette dips Mow the surface of the acid per- manganate solution in the flask. Titrate to a colourless end- point. As the end-point approaches, warm the solution to about 40 OC and continue the titration slowly until the colour of the permanganate is just disc

38、harged. Note the volume of stan- dard nitrite sdution used in the titration. Reproducibility - 0,ooO 2 to 0.001 8 0.003 to 0,009 0,007 to 0.040 0.004 to 0.021 0.001 to 0.004 0,002 to 0,012 50 ml of a potassium permanganate standard volumetric solu- tion, dl/5 KMn04i = 0.01 mol/l, is equivalent to 3,

39、502 mg of nitrogen. Thus, for the standard nitrite solution (4.41, the vdume 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 f 0.40 ml. 11 Test report The test report shall include the following

40、information: a) a reference to this International Standard; bi all details required for the complete identification of the sample; ci details concerning aie storage of the laboratory sample before analysis; d) a statement of the repeatability achieved by the laboratory when using this method; e) the

41、 results and the method of expression used; f) details of any deviation from the procedure specified in this International Standard or any other circumstances that may have influenced the result. 6 - . CEN ENa26777 93 m 3404589 0047366 98b m BS 6068 : Section 2.16 : 1984 4 I Substance Annex Effect o

42、f other substances on the result Magnesium Potassium Potassium Sodium Sodium Hydrogen carbonate Hydrogen carbonate Nitrate Ammonium Cadmium Zinc Manganese Iron(ll1) Iron(lll) Copper Aluminium Silicate Urea Thiosulfate Thiosulfate Chlorine Chlorine Chloramine Chloramine Salt used Acetate Chloride Chl

43、oride Chloride Chloride Sodium Sodium Potassium Chloride Chloride Acetate Chloride Chloride Chloride Acetate Sulfate Sodium - Sodium Sodium - - - - Hydroxylammonium chloride Sodium polyphosphate (hexametaphosphate) Sodium polyphosphate (hexametaphosphate) Mass of substance cis loo0 100 loo0 100 loo0

44、 6 100 (HC0.J 12 200 (HC0.J 1 o00 (NI 100 (NI 100 100 100 10 100 100 100 100 isi0,i 100 100 (s2q 1 o00 (s03 0.00 - 0.22 - 1.01 -0.06 - 0.30 0.00 - 0.03 - 0.80 mN = 10.0 ci9 - 0,07 - 0.07 -0.13 - 0,02 -0.13 + 0.01 + 0.06 - 0.06 - 0,03 - 0.03 0.00 - 0.03 - 0,03 - 0.51 - 0.07 - 0.03 - - 0.09 - 0.82 - 0

45、.77 - 0,25 - 2.81 - 0.07 -2.78 - 0.01 - 0.82 -8.10 * Mass of substance present in the test portion. The mass is given as the dement or compound, except where otherwise indicated in brackets. The maximum effects, assuming no interference, are as follows: 0.00 f 0.02 pg; 1.00 I 0.08 pg; 10.00 f 0.14 pg I95 % confidence limit). 7