1、BRITISH STANDARD BS 6068-2.7: 1984 ISO 5664:1984 Water quality Part 2: Physical, chemical and biochemical methods Section 2.7 Determination of ammonium: distillation and titration method ISO title: Water quality Determination of ammonium Distillation and titration method UDC 556:614.777:628.1/.3:663
2、63:543.24:546.171.1BS6068-2.7:1984 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 10-1999 The following BSI references relate to the
3、work on this standard: Committee reference EPC/44 Draft for comment 83/50174 DC ISBN 0 580 14197 7 Amendments issued since publication Amd. No. Date of issue CommentsBS6068-2.7:1984 BSI 10-1999 i Contents Page National foreword ii 1 Scope 1 2 Field of application 1 3 Principle 1 4 Reagents 1 5 Appar
4、atus 2 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 2 9 Test report 3 Table 1 2 Table 2 3 Table 3 3BS6068-2.7:1984 ii BSI 10-1999 National foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committe
5、e, is identical with ISO5664:1984 “Water quality Determination of ammonium Distillation and titration method”. The International Standard was prepared by subcommittee2, Physical, chemical and biochemical methods, of Technical Committee147, Water quality, of the International Organization for Standar
6、dization (ISO) as a result of discussion in which the UK participated. 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 1 to 6 which, togethe
7、r with Part0, 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 h
8、as 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
9、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
10、 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 fro
11、m legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to3 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 fr
12、ont cover.BS6068-2.7:1984 BSI 10-1999 1 1 Scope This International Standard specifies a distillation and titration method for the determination of ammonium in raw, potable and waste water. 2 Field of application 2.1 Range An ammonium nitrogen content of up to10mg in the test portion may be determine
13、d. Using a10ml test portion, this corresponds to a sample concentration of up to A P N= 1000mg/l. 2.2 Limit of detection A practically determined (4degrees of freedom) limit of detection, using a250ml test portion, is cvA N= 0,2mg/l. 2.3 Sensitivity Using a100ml test portion1,0ml of0,02mol/l hydroch
14、loric acid is equivalent to A N= 2,8mg/l. 2.4 Interferences The main possible interference arises from urea which, under the conditions specified, will distil as ammonia thus causing high results. Interference will also arise from volatile amines which will distil and react with the acid during the
15、titration, thus causing high results. Chloramines present in chlorinated water samples will be determined in this manner. 3 Principle Adjustment of the pH of a test portion to within the range6,0to7,4. Addition of magnesium oxide to produce mildly alkaline conditions, distillation of the liberated a
16、mmonia and collection in a receiving flask containing boric acid solution. Titration of the ammonium in the distillate with standard volumetric acid solution using boric acid/indicator solution. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only water prepared
17、as described in 4.1. 4.1 Water, ammonium-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
18、 Add about10g of the same resin to each litre of eluate for storage purposes. 4.1.2 Distillation method Add0,10 0,01ml of sulfuric acid solution(A = 1,84g/ml) to 1000 10ml of distilled water and redistil in an all glass apparatus. Discard the first50ml of distillate, and then collect the distillate
19、 in a glass bottle provided with a well-fitting glass stopper. Add about10g of strongly acidic, cation exchange resin (in the hydrogen form), to each litre of collected distillate. 4.2 Hydrochloric acid, A = 1,18g/ml. 4.3 Hydrochloric acid, standard volumetric solution, c(HCl) = 0,10mol/l. Prepare t
20、his solution by diluting the hydrochloric acid (4.2). Standardize it by normal analytical procedures. Alternatively, commercial solutions of guaranteed concentration may be used. 4.4 Hydrochloric acid, standard volumetric solution, c(HCl) = 0,02mol/l. Prepare this solution by diluting the hydrochlor
21、ic acid (4.2). Standardize it by normal analytical procedures. Alternatively, commercial solutions of guaranteed concentration, or a diluted solution of the standard volumetric hydrochloric acid (4.3), may be used. 4.5 Boric acid/indicator, solution. 4.5.1 Dissolve0,5 0,1g of water-soluble methyl re
22、d in about800ml of water and dilute to1litre. 4.5.2 Dissolve1,5 0,1g of methylene blue in about800ml of water and dilute to1litre. 4.5.3 Dissolve20 1g of boric acid (H 3 BO 3 ) in warm water. Cool to room temperature. Add10 0,5ml of the methyl red indicator solution(4.5.1) and2,0 0,1ml of the methyl
23、ene blue solution (4.5.2) and dilute to1litre. 4.6 Bromothymol blue, 0,5g/l indicator solution. Dissolve0,5 0,02g of bromothymol blue in water and dilute to 1litre. 4.7 Hydrochloric acid, 1% (V/V) solution. Dilute10 1ml of the hydrochloric acid (4.2) to1litre with water. 4.8 Sodium hydroxide solutio
24、n, 1 mol/l Dissolve40 2g of sodium hydroxide in about500ml of water. Cool to room temperature and dilute to 1 litre. 4.9 Light magnesium oxide, carbonate-free. Heat the magnesium oxide at500 C to remove carbonate. 4.10 Anti-bumping granules 4.11 Anti-foaming agent, for example paraffin wax chips.BS6
25、068-2.7:1984 2 BSI 10-1999 5 Apparatus Ordinary laboratory apparatus, and Distillation apparatus, incorporating a distillation flask of capacity800 to1000ml attached to an anti-splash head and a vertical condenser arranged so that the outlet can be immersed in absorbent solution. NOTE ON PRELIMINARY
26、 CLEANING OF THE DISTILLATION APPARATUS Carry out this procedure whenever the apparatus has been out of use for more than a few days. Place about350ml of the ammonium-free water(4.1) in the distillation flask. Add a few anti-bumping granules (4.10), assemble the apparatus, and distil until at least1
27、00ml of the water has been collected. Discard the distillate and the residue in the distillation flask. 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 between 2and5 C until analysed. Aci
28、dification with sulfuric acid to pH2may also be used 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 Selection of volume of test portion If the approximate ammonium content of the sample is k
29、nown, select the volume of the test portion according to Table 1. Table 1 7.2 Determination 7.2.1 Transfer50 5ml of the boric acid/indicator solution (4.5) into the receiving flask of the distillation apparatus. Ensure that the delivery tip of the condenser is below the surface of the boric acid sol
30、ution. Measure the selected volume of test portion (see 7.1) into the distillation flask. NOTEIf chlorine is present in the test portion, a few small crystals of sodium thiosulfate should be added in order to remove it. Add a few drops of the bromothymol blue indicator solution (4.6) and, if necessa
31、ry, adjust the pH to within the range6,0 (indicator yellow) to7,4 (indicator blue) using the sodium hydroxide solution(4.8) or the hydrochloric acid (4.7), as appropriate. Then make up the total volume in distillation flask to about 350ml with the ammonium-free water(4.1). Add to the distillation fl
32、ask0,25 0,05g of the light magnesium oxide (4.9) and a few anti-bumping granules (4.10). The addition of anti-foaming agent(4.11) may be necessary with some waste water samples. Immediately attach the distillation flask to the apparatus. 7.2.2 Heat the distillation flask so that distillate collects
33、at a rate of about10ml/min. Stop the distillation when about200ml have been collected. 7.2.3 Titrate the distillate to the purple end-point using the standard volumetric hydrochloric acid(4.4) and record the volume used. NOTE 1The standard volumetric hydrochloric acid (4.3) may be used for titration
34、 of distillates from samples having high ammonium contents. NOTE 2Ammonia can be titrated as it distils into the receiving flask. If protracted collection of ammonia is thus revealed, it may indicate the presence of interfering substances which are undergoing slow hydrolysis to yield ammonia. 7.3 Bl
35、ank test Carry out a blank test by proceeding as described in7.2, but replacing the test portion with about250ml of the ammonium-free water (4.1). 8 Expression of results 8.1 Method of calculation The ammonium nitrogen concentration, A N , expressed in milligrams per litre, is given by the equation
36、where V 0 is the volume, in millilitres, of the test portion (see 7.1); V 1 is the volume, in millilitres, of the standard volumetric hydrochloric acid used for titration; V 2 is the volume, in millilitres, of the standard volumetric hydrochloric acid used for the titration in the blank test (see7.3
37、); c is the exact concentration, in moles per litre, of the hydrochloric acid used for the titration; 14,01is the atomic mass, in grams per mole, of nitrogen. Ammoniumconcentration, A N Volume of the test portion a mg/l ml up to 10 10 to20 20 to50 50 to 100 250 100 50 25 a When using the standard vo
38、lumetric hydrochloric acid (4.3) for the titration. N V 1 V 2 V 0 -c 1401 , 1 000 =BS6068-2.7:1984 BSI 10-1999 3 The result may be expressed as the mass concentration of nitrogen, A N , ammonia, , or ammonium ion, , in milligrams per litre, or as the amount of substance concentration of ammonium ion
39、 in micromoles per litre. The appropriate conversion factors are given in Table 2. Table 2 Example: An ammonium ion concentration, of 1 mg/l corresponds to a nitrogen concentration of0,777mg/l. 8.2 Reproducibility Reproducibility standard deviations have been determined as indicated in Table 3. 9 T
40、est report The test report shall include the following information: a) reference to this International Standard; b) all details required for the complete identification of the sample; c) details concerning the storage and preservation of the laboratory sample before analysis; d) a statement of the r
41、epeatability achieved by the laboratory when using this method; e) the result and the method of expression used; f) details of any deviation from the procedure specified in this International Standard or any other circumstance that may have influenced the result. Table 3 a A N mg/l mg/l mg/l 4mol/l
42、A N= 1 mg/l 1 1,216 1,288 71,4 = 1 mg/l 0,823 1 1,059 58,7 = 1 mg/l 0,777 0,944 1 55,4 = 1 4mol/l 0,014 0,017 0,018 1 NH 3 NH + 4 c(NH + 4) NH 3 NH + 4 c(NH + 4) NH 3 NH + 4 c(NH + 4) NH + 4 Sample Ammonium content, A N Volume of test portion Standard deviation Degrees of freedom mg/l ml mg/l Standa
43、rd solution 4,0 250 0,23 10 Standard solution 40 250 0,56 11 Settled sewage 35 100 0,70 16 Sewage effluent 1,8 25 0,16 11 a Information from the United Kingdom.BS 6068-2.7: 1984 ISO 5664:1984 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body
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