1、BRITISH STANDARD BS6068-2.11: 1984 ISO7150-1: 1984 Water quality Part2: Physical, chemical and biochemical methods Section2.11 Determination of ammonium: manual spectrometric method ISO title: Water quality Determination of ammonium Manual spectrometric method UDC 556:614.777:628.1/.3:663.63:543.42.
2、062:546.171.1BS6068-2.11:1984 This British Standard, having been prepared under the directionof the Environment andPollution Standards Committee, was published underthe authority of the BoardofBSI and comes into effect on 31 December 1984 BSI 06-1999 The following BSI references relate to the work o
3、n this standard: Committee reference EPC/44 Draft for comment 83/51031 DC ISBN 0 580 14157 8 Amendments issued since publication Amd. No. Date of issue CommentsBS6068-2.11:1984 BSI 06-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents
4、1 5 Apparatus 2 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 3 9 Interferences 4 10 Special cases 4 11 Notes on procedure 4 12 Test report 5 Annex A The effect of other substances on N 6 Annex B Typical absorbance values for blank and standard solutions 6 Table 1 Volumes of standar
5、d solution for use in the calibration series 3 Table 2 Conversion table 3 Table 3 Repeatability and reproducibility standard deviations 4 Publication referred to Inside back coverBS6068-2.11:1984 ii BSI 06-1999 National foreword This Section of BS6068, which has been prepared under the direction of
6、the Environment and Pollution Standards Committee, is identical in technical content and in presentation with ISO7150 Water quality Determination of ammonium Part1:1984 Manual spectrometric method. The international standard was prepared by Subcommittee2, Physical, chemical and biochemical methods,
7、of Technical Committee147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in which the UKparticipated. BS6068 is being published in a series of Parts subdivided into Sections that will generally correspond to particular international standards. S
8、ections are being, or will be, published in Parts1 to6, which, together with Part0, are listed below. 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: Samplin
9、g. 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 followin
10、g. 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. Where the words “International Standard” appear, referring to this standard, they should be read as “Section of BS6068”. It is current practice in Br
11、itish Standards for the symbol “L” to be used for litre rather than “l” and for the term “sulphur” to be used rather than “sulfur”. Textual error. When adopting the text of this international standard, the textual error given below was discovered. It has been marked in the text and has been reported
12、 to ISO in a proposal to amend the text of the international standard. In Table 3, for “well-water”, the repeatability should be0.002 to0.007. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct appli
13、cation. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International standard Corresponding British Standard ISO5664-1984 BS6068 Water quality Section2.7:1984 Determination of ammonium: distillation and titration method (Identical) Summa
14、ry of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1to6, an inside back cover and 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 cove
15、r.BS6068-2.11:1984 BSI 06-1999 1 1 Scope and field of application 1.1 Substance determined This part of ISO7150 specifies a manual spectrometric method for the determination of ammonium in water. NOTEAn automated spectrometric method for the determination of ammonium will form the subject of ISO7150
16、/2. 1.2 Type of sample The method is applicable to the analysis of potable water, and most raw and waste waters. Application to excessively coloured or saline waters shall be preceded by distillation (see clause10). For interferences, see clause9. 1.3 Range An ammonium nitrogen concentration, A Nof
17、up to1mg/l, using the maximum test portion of40ml, can be determined. Much higher concentrations can be determined by taking smaller test portions. 1.4 Limit of detection 1) When using cells of optical path length40mm and a40ml test portion, the limit of detection lies within the range A N =0,003 to
18、0,008mg/l. 1.5 Sensitivity 1) Using a40ml test portion and a cell of optical path length40mm, A N =0,200mg/l gives an absorbance of about0,69units. Using a40ml test portion and a cell of optical path length10mm, A N =0,750mg/l gives an absorbance of about0,65units. 2 Reference ISO5664, Water quality
19、 Determination of ammonium Distillation and titration method. 3 Principle Spectrometric measurement at about655nm of the blue compound formed by reaction of ammonium with salicylate and hypochlorite ions in the presence of sodium nitrosopenta-cyanoferrate(III) (sodium nitroprusside). Hypochlorite io
20、ns are generated in situ by the alkaline hydrolysis of N, N-dichloro-1,3,5-triazine-2,4,6 (1H,3H,5H)-trione, sodium salt (sodium dichloroisocyanurate). Reaction of the chloramine with sodium salicylate takes place at pH12,6 in the presence of sodium nitroprusside. Any chloramines present in the samp
21、le are quantitatively determined as a consequence. Sodium citrate is incorporated in the reagent to mask interference from cations, notably calcium and magnesium. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only water prepared as described in4.1. 4.1 Water, a
22、mmonium-free, prepared by one of the following methods. 4.1.1 Ion exchange method Pass distilled water through a column of strongly acidic cation exchange resin (in the hydrogen form) and collect the eluate in a glass bottle provided with a well-fitting glass stopper. Add about10g of the same resin
23、to each litre of collected eluate for storage purposes. 4.1.2 Distillation method Add0,10 0,01ml of sulfuric acid (A=1,84g/ml) to1000 10ml of distilled water and redistil in an all glass apparatus. Discard the first50ml of distillate, and then collect the distillate in a glass bottle provided with a
24、 well-fitting glass stopper. Add about10g of strongly acidic cation exchange resin (in the hydrogen form) to each litre of collected distillate. 4.2 Colour reagent Dissolve1301g of sodium salicylate (C 7 H 6 O 3 Na) and1301g of trisodium citrate dihydrate (C 6 H 5 O 7 Na 3 2H 2 O) in water(4.1) in a
25、1000ml one-mark volumetric flask. Add sufficient water to give a total liquid volume of about950ml and then add0,9700,005g of sodium nitrosopentacyanoferrate(III) dihydrate sodium nitroprusside, Fe(CN) 5 NONa 2 2H 2 O. Dissolve the solid and then dilute to the mark with water. Stored in an amber gla
26、ss bottle, this reagent is stable for at least2weeks. 1) Data from a United Kingdom interlaboratory exercise involving five participants.BS6068-2.11:1984 2 BSI 06-1999 4.3 Sodium dichloroisocyanurate, solution. Dissolve32,00,1g of sodium hydroxide in50050ml of water(4.1). Cool the solution to room t
27、emperature and add2,000,02g sodium dichloroisocyanurate dihydrate (C 3 N 3 O 3 Cl 2 Na.2H 2 O) to the solution. Dissolve the solid and transfer the solution quantitatively to a1000ml one-mark volumetric flask. Dilute to the mark with water. Stored in an amber glass bottle, this reagent is stable for
28、 at least2weeks. 4.4 Ammonium nitrogen, standard solution, A N =1000mg/l. Dissolve3,8190,004g of ammonium chloride (dried at105C for at least2h) in about800ml of water(4.1) in a1000ml one-mark volumetric flask. Dilute to the mark with water. 1ml of this standard solution contains1mg of ammonium nitr
29、ogen. Stored in a stoppered glass bottle, this solution is stable for at least1month. 4.5 Ammonium nitrogen, standard solution, A N =100mg/l. Pipette100ml of ammonium nitrogen standard solution (4.4) into a1000ml one-mark volumetric flask. Dilute to the mark with water. 1ml of this standard solution
30、 contains0,1mg of ammonium nitrogen. Stored in a stoppered glass bottle, this solution is stable for1week. 4.6 Ammonium nitrogen, standard solution, A N =1mg/l. Pipette1ml of ammonium nitrogen standard solution (4.5) into a100ml one-mark volumetric flask. Dilute to the mark with water. 1ml of this s
31、tandard solution contains14g of ammonium nitrogen. Prepare this solution immediately before use. 4.7 Cleaning solution. Dissolve1002g of potassium hydroxide in1002ml of water. Cool the solution and add90050ml of95% (V/V) ethanol. Store the solution in a polyethylene bottle. 5 Apparatus Ordinary labo
32、ratory apparatus and 5.1 Spectrometer, capable of operating at a wavelength of655nm with cells of optical path length between10 and50mm. 5.2 Water-bath or incubator, capable of being maintained at251 C. NOTE ON CLEANING OF GLASSWARE All glassware shall be carefully cleaned using the cleaning solutio
33、n(4.7) followed by thorough rinsing with water(4.1). 6 Sampling and samples Laboratory samples shall be collected in polyethylene or glass bottles. They should be analysed as quickly as possible, or else stored at between2 and5C until analysed. Acidification with sulfuric acid to pH 2 may also be us
34、ed as an aid to preservation, provided that possible contamination of the acidified sample by absorption of any atmospheric ammonia is avoided. 7 Procedure 7.1 Test portion The maximum test portion volume is40ml, which can be used for the determination of ammonium nitrogen concentrations up to A N =
35、1mg/l. Smaller test portions may be used as appropriate in order to accommodate much higher ammonium nitrogen concentrations. Laboratory samples containing suspended matter should be allowed to settle, or filtered by gravity through a pre-rinsed glass fibre paper before taking the test portion. Alte
36、rnatively, prior distillation of the sample may be used (see clause10). 7.2 Preparation of test solution Pipette the test portion (7.1) into a50ml one-mark volumetric flask, and, if necessary, dilute to401ml with water(4.1). 7.3 Determination 7.3.1 Formation of the absorbing compound Add4,000,05ml o
37、f colour reagent(4.2) and mix well. Then add4,000,05ml of sodium dichloroisocyanurate solution(4.3) and mix well. NOTEAfter this addition the pH of the solution should be12,6 0,1. Extremes of acidity or alkalinity in the sample may cause deviation. Dilute to the mark with water(4.1). Shake the flask
38、 thoroughly and place it in the water-bath(5.2) maintained at251C. NOTEOther water-bath temperatures may be used, but all determinations and calibrations should be carried out at the same temperature (within1K). 7.3.2 Spectrometric measurements After at least60min, remove the flask from the water-ba
39、th and measure the absorbance of the solution at the wavelength of maximum absorbance, approximately655nm, in a cell of suitable path length against water(4.1) in the reference cell. NOTEThe wavelength of maximum absorbance should be checked when this method is first used, and should be used in all
40、subsequent determinations.BS6068-2.11:1984 BSI 06-1999 3 7.4 Blank test Proceed as described in7.2 and7.3, but using401ml of water(4.1) in place of the test portion. 7.5 Calibration 7.5.1 Preparation of the set of calibration solutions To a series of nine50ml one-mark volumetric flasks add, by means
41、 of a burette, the volumes of ammonium nitrogen standard solution(4.6) shown in Table 1. Add water(4.1) to give a volume of401ml if necessary. 7.5.2 Formation of the absorbing compound See7.3.1. 7.5.3 Spectrometric measurements Proceed according to7.3.2 using the cell path length(s) specified in Tab
42、le 1 for absorbance measurements. Table 1 Volumes of standard solution for use in the calibration series 7.5.4 Plotting the calibration graph Subtract the absorbance of the zero member from the absorbances obtained from the other calibration solutions. Plot a graph of absorbance against mass of ammo
43、nium nitrogen, m N , for each cell path length. This graph should be linear and should pass through the origin. 8 Expression of results 8.1 Method of calculation The absorbance due to ammonium in the test portion, A r , is given by the equation A r = A s A b NOTEA sand A bmust be measured in cells o
44、f the same path length for a particular sample. The ammonium nitrogen content, A N , in milligrams per litre, is given by the formula See Table 2 for conversion of A Nto ammonia and ammonium concentrations. Table 2 Conversion table Example: An ammonium ion concentration, of 1mg/l corresponds to a ni
45、trogen concentration of0,777mg/l. 8.2 Precision Repeatability and reproducibility standard deviations have been determined as shown in Table 3. Volume of standard solution(4.6) Mass of ammonium nitrogen, m N Cell path length ml 4g mm 0,00 a 2,00 4,00 6,00 8,00 10,00 20,00 30,00 40,00 0 2 4 6 8 10 20
46、 30 40 10 and40 b 40 40 40 40 10 10 10 10 a The zero member. b 50 mm path length cells may be used. where A s is the absorbance of the test solution(7.3.2); A b is the absorbance of the blank test solution(7.4). where m N is the mass, in micrograms, of ammonium nitrogen, determined from A rand the c
47、alibration graph(7.5.4) for the appropriate cell path length; V is the test portion volume, in millilitres. A N c( ) mg/l mg/l mg/l 4mol/l A N=1mg/l =1mg/l =1mg/l c() =14mol 1 0,823 0,777 0,014 1,216 1 0,944 0,017 1,288 1,059 1 0,018 71,4 58,7 55,4 1 mN V - A NH 3 A NH + 4 NH + 4 A NH 3 A NH + 4 NH
48、+ 4 A NH + 4BS6068-2.11:1984 4 BSI 06-1999 9 Interferences A range of substances often encountered in water samples has been tested for possible interference with this method. Full details are given in Annex A. The only serious interferences which have been encountered are those from aniline and eth
49、anolamine, and represent the interference to be expected from primary amines in general. However, such substances are seldom encountered at appreciable concentrations in water samples. Extremes of acidity or alkalinity will interfere with the formation of the absorbing compound, as will the presence of any substance causing reduction of hypochlorite ions, although these circumstances are unlikely to arise in most water samples. The procedure referred to in clause10 should be adopted in such ci
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