BS-6068-2.33-1987 ISO-7150-2-1986.pdf

BRITISH STANDARD BS 6068-2.33: 1987 ISO 7150-2: 1986 Water quality Part 2: Physical, chemical and biochemical methods Section 2.33 Method for the determination of ammonium: automated spectrometric method ISO title: Water quality Determination of ammonium Part 2: Automated spectrometric method UDC 556.11 + 614.777 + 628/.1/.3 + 663.63 53/54:543.373.5 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 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 30 November 1987 © BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment 85/54468 DC ISBN 0 580 16261 3 Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 © BSI 11-1999i Contents Page National forewordii 1Scope and field of application1 2Reference1 3Principle1 4Reagents1 5Apparatus2 6Sampling and samples3 7Procedure3 8Expression of results4 9Interferences4 10Notes on procedure4 11Special cases5 12Test report5 Annex The effect of other substances on ÔN8 Figure 16 Figure 27 Table 1 Order of loading of the turntable3 Table 2 Volumes of standard solution for use in the preparation of the calibration solutions4 Table 3 Conversion table4 Table 4 Reproducibility standard deviations5 Table 5 The effect of other substances on ÔN8 Publication referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 ii © BSI 11-1999 National foreword This Section of BS 6068, which has been prepared under the direction of the Environment and Pollution Standards Committee is identical with ISO 7150-2:1986 “Water quality Determination of ammonium Part 2: Automated 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) with the active participation and approval of the UK. BS 6068 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, together with Part 0, 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: 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 “part of ISO 7150” appear, referring to this standard, they should be read as “Section of BS 6068”. In British Standards it is current practice to use the symbol “L” for litre (and in its submultiples) rather than “l”, and to use the spelling “sulphur”, etc., instead of “sulfur”, etc. Textual errors. When adopting the text of the International Standard, the following textual errors were discovered. They have been marked in the text and have been reported to ISO in a proposal to amend the text of the International Standard. In clause 6, line 4, “may also be used” should be read as “shall also be permissible”. In 10.2, paragraph 3, lines 4 and 5, “controlled standard solution lie” should be read as “control standard solution lies”. Additional information. Clause 4.5.2 and the last sentence in clause 7.4 would normally be included in a British Standard as notes as they are given for guidance only. Cross-references International StandardCorresponding British Standard ISO 5664:1984BS 6068 Water quality BS 6068-2.7:1984 Determination of ammonium: distillation and titration method (Identical) Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 © BSI 11-1999iii The tests described in this British Standard should only be carried out in laboratories with suitable facilities and by suitably qualified persons with an appropriate level of chemical expertise and knowledge of the necessary safety precautions. Standard chemical procedures should be followed throughout. 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 to iv, pages 1 to 8, an inside back cover 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. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 © BSI 11-19991 1 Scope and field of application 1.1 Substance determined This part of ISO 7150 specifies an automated spectrometric method for the determination of ammonium in water. NOTEFor a manual spectrometric method for the determination of ammonium, see ISO 7150-1. 1.2 Type of sample The method is applicable to the analysis of raw, potable and most waste waters. Application to excessively coloured or saline waters shall be preceded by distillation (see clause 11). For interferences, see clause 9. 1.3 Range An ammonium nitrogen concentration, ÕN, of up to 50 mg/l can be determined using dialysis, or up to 0,5 mg/l without dialysis (see clause 5). 1.4 Limit of detection1) With dialysis, the limit of detection is ÕN . 0,03 mg/l. Without dialysis it is ÕN . 0,01 mg/l. 2 Reference ISO 5664, Water quality Determination of ammonium Distillation and titration method. 3 Principle Spectrometric measurement at about 650 nm of the blue compound formed by reaction of ammonium with salicylate and hypochlorite ions in the presence of sodium nitrosopentacyanoferrate(III) (sodium nitroprusside). Hypochlorite ions are generated by the alkaline hydrolysis of 1,3-dichloro-5-sodio-1,3,5-triazinanetrione (sodium dichloroisocyanurate). Reaction of the resulting chloroamine with sodium salicylate takes place at pH 12,6 in the presence of nitroprusside. Any chloroamines present in the sample are quantitatively determined as a consequence. Sodium citrate is added to mask interference from cations, notably calcium and magnesium. All reactions are carried out automatically using continuous flow techniques.2) The absorbance of the coloured compound is measured in a flow-through spectrometer. Two distinct analytical manifold configurations are specified. One incorporates a dialyser block and is suitable for the determination of ammonium nitrogen concentrations up to 50 mg/l. The other omits the dialyser and is suitable for the determination of low level ammonium nitrogen concentrations up to 0,5 mg/l. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only water prepared 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. Add about 10 g of the same resin to each litre of collected eluate for storage purposes. 4.1.2 Distillation method Add 0,10 ± 0,01 ml of sulfuric acid (Õ = 1,84 g/ml) to 1 000 ± 10 ml of distilled water and redistil in an all glass apparatus. Discard the first 50 ml of distillate, and then collect the distillate in a glass bottle provided with a well-fitting glass stopper. Add about 10 g of strongly acidic cation exchange resin (in the hydrogen form) to each litre of collected distillate. 4.2 Citrate reagent 4.2.1 Preparation Dissolve 40,0 ± 0,5 g of trisodium citrate dihydrate (C6H5O7Na3·2H2O) in about 950 ml of water (4.1) in a 1 litre measuring cylinder. Dilute to 1 litre with water (4.1). Store the solution in a glass or plastics bottle. This reagent is stable for at least 3 weeks. 4.2.2 Wetting agent (optional) The inclusion of a wetting agent in this reagent in order to promote smooth flow in the system is optional. If used, the wetting agent shall be a proprietary detergent of the alkyl benzenesulfonate type and shall be added to give a concentration of 1 ml/l. 1) Limit of detection calculated from 3 , where is an estimate, with at least 9 degrees of freedom, of the within-batch standard deviation of blank solution responses. Information from the United Kingdom. 2) HMSO. Methods for Examination of Waters and Associated materials: Air Segmented Continuous Flow Automatic Analysis in the Laboratory. London, Her Majestys Stationery Office, 1979. swsw Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 2 © BSI 11-1999 4.3 Salicylate reagent Dissolve 34,0 ± 0,5 g of sodium salicylate (C7H5O3Na) in water (4.1) in a 1 000 ml one-mark volumetric flask. Then add 0,400 ± 0,005 g of sodium nitrosopentacyanoferrate(III) dihydrate sodium nitroprusside, Fe(CN)5NONa2·2H2O. Dissolve the solid and then make up to the mark with water (4.1). Stored in an amber glass bottle, this reagent is stable for at least 2 weeks. 4.4 Sodium dichloroisocyanurate, solution. Dissolve 10,0 ± 0,1 g of sodium hydroxide in 500 ± 50 ml of water (4.1). Cool the solution to room temperature and then add 0,80 ± 0,02 g of sodium dichloroisocyanurate dihydrate (C3N3O3Cl2Na·2H2O) to the solution. Dissolve the solid and transfer the solution quantitatively to a 1 000 ml one-mark volumetric flask. Make up to the mark with water (4.1) and mix well. Stored in an amber glass bottle at 4 °C, this reagent is stable for at least 2 weeks. 4.5 Salicylate/citrate mixed reagent (for use in the determination of ammonium nitrogen concentrations up to 0,5 mg/l). 4.5.1 Preparation Dissolve 34,0 ± 0,1 g of sodium salicylate (C7H5O3Na) and 40,0 ± 0,5 g of trisodium citrate dihydrate (C6H5O7Na3·2H2O) in about 950 ml of water (4.1) in a 1 000 ml one-mark volumetric flask. Then add 0,400 ± 0,005 g of sodium nitrosopentacyanoferrate(III) dihydrate sodium nitroprusside, Fe(CN)5NONa2·2H2O. Dissolve the solid and then make up to the mark with water (4.1). Stored in an amber glass bottle, this reagent is stable for at least 2 weeks. 4.5.2 Wetting agent (optional) A wetting agent (see 4.2.2) may be incorporated in this reagent. 4.6 Ammonium nitrogen, standard solution, ÕN= 1 000 mg/l. Dissolve 3,819 ± 0,004 g of ammonium chloride (dried at 105 °C for at least 2 h) in about 800 ml of water (4.1) in a 1 000 ml one-mark volumetric flask. Make up to the mark with water (4.1). 1 ml of this standard solution contains 1 mg of ammonium nitrogen. Stored in a stoppered glass bottle, this solution is stable for at least 1 month. 4.7 Ammonium nitrogen, standard solution, ÕN= 20 mg/l. Pipette 10 ml of the ammonium nitrogen standard solution (4.6) into a 500 ml one-mark volumetric flask. Make up to the mark with water. 1 ml of this standard solution contains 0,02 mg of ammonium nitrogen. Stored in a stoppered amber glass bottle and kept at 2 to 5 °C, this solution is stable for 1 week. 5 Apparatus Apparatus for this continuous flow method consists basically of the following. 5.1 Sample presentation unit (sampler) 5.2 Multichannel peristaltic pump 5.3 Analytical cartridge (manifold), including pump tubes, mixing coils and dialyser unit. The design of the manifold depends on the intended range of application. Figure 1 shows that for the determination of ammonium nitrogen concentrations up to 50 mg/l. Figure 2 shows the manifold for the determination of ammonium nitrogen concentrations up to 0,5 mg/l. This is essentially a modification of Figure 1 and permits greater sensitivity due to the larger sample flow rate. It is the preferred configuration for the analysis of potable waters. For the analysis of low levels of ammonium the design of both systems can be improved by drawing air used for segmentation through dilute hydrochloric acid in order to scrub any atmospheric ammonia. Errors from the same source can also be reduced by capping the sample cups, once filled with samples, with thin aluminium foil which will be pierced as the sampling probe descends. The manifold system shown in Figure 2 is unsuitable for samples with a high suspended solids content unless the solids are first removed by settlement, centrifuging or filtration. Ensure that no ammonium is added or lost by any method of removal adopted. Alternatively, give consideration to using distillation (see clause 11). 5.4 Spectrometer capable of measuring absorbance at 650 nm, incorporating a flow cell with an optical path length of at least 15 mm. 5.5 Recorder Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:29:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.33:1987 © BSI 11-19993 6 Sampling and samples Laboratory samples shall be collected in polyethylene or glass bottles. They shall be analysed as quickly as possible, or else stored at between 2 and 5 °C until analysed. Acidification with sulfuric acid to pH 2 may also be used3) 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 Starting operation Connect the system as shown in Figure 1 or Figure 2 depending on the intended range of application. Follow the equipment manufacturers general operating instructions where appropriate. With the sample probe at rest in the blank water contained in the wash receptacle, place all the reagent lines in their respective reagents, start the pump and switch on the spectrometer and recorder. Allow the system to equilibrate for at least 20 min and during this period check that the bubble pattern and hydraulic behaviour of the system is satisfactory. If not, eliminate difficulties before proceeding. 7.2 Initial sensitivity setting When an acceptably smooth baseline trace is given on the recorder, adjust the baseline response to about 5 % of full scale with the zero control and then transfer the sample probe into the ÕN, max calibration solutio