1、BRITISH STANDARD BS 6068-2.48: 1995 ISO 10359-2: 1994 Water quality Part 2: Physical, chemical and biochemical methods Section 2.48 Determination of inorganically bound total fluoride after digestion and distillationBS6068-2.48:1995 This British Standard, having been prepared under the direction of
2、the Health and Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 April 1995 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment 92/58404 DC ISBN 0 580 23959 4 Committee
3、s responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee EPC/44, Water quality, upon which the following bodies were represented: Association of Consulting Scientists British Association for Chemical Specialists British Gas plc Chemical In
4、dustries Association Convention of Scottish Local Authorities Department of the Environment (Water Directorate) Department of the Environment for Northern Ireland Department of Trade and Industry (Laboratory of the Government Chemist) Electricity Association Industrial Water Society Institute of Gas
5、 Engineers Institution of Water Officers Institution of Water and Environmental Management National Rivers Authority Royal Institute of Public Health and Hygiene Royal Society of Chemistry Scottish Association of Directors of Water and Sewerage Services Soap and Detergent Industry Association Water
6、Companies Association Water Research Centre Water Services Association of England and Wales The following bodies were also represented in the drafting of the standard, through subcommittees and panels: The Association of the Laboratory Supply Industry British Agrochemicals Association Ltd. British C
7、eramic Research British Soft Drinks Association Ltd. GAMBICA (BEAMA) Ltd. Society of Chemical Industry Swimming Pool and Allied Trades Association Ltd. Amendments issued since publication Amd. No. Date CommentsBS6068-2.48:1995 BSI 07-1999 i Contents Page Committees responsible Inside front cover Nat
8、ional foreword ii Introduction 1 1 Scope 1 2 Normative reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Sampling and samples 2 7 Procedure 2 8 Calculation 5 9 Precision 5 10 Test report 5 Annex A (informative) Bibliography 6 Figure 1 Example of a distillation apparatus 3 Table 1 Preparation of
9、 reference solutions 4 Table 2 Precision data 5 List of references Inside back coverBS6068-2.48:1995 ii BSI 07-1999 National foreword This Section of BS 6068 has been prepared by Technical Committee EPC/44, and is identical with ISO 10359-2:1994 Water quality Determination of fluoride Part 2: Determ
10、ination of inorganically bound total fluoride after digestion and distillation. The international standard was prepared by 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 publis
11、hed 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 7, which, together with Part 0, are listed below. Part 0: Introduction; Part 1: Glossary; Part 2: Physical, chemical and bio
12、chemical methods; Part 3: Radiological methods; Part 4: Microbiological methods; Part 5: Biological methods; Part 6: Sampling; Part 7: Precision and accuracy; NOTEThe tests described in this Section of BS 6068 should only be carried out by suitably qualified persons with an appropriate level of biol
13、ogical expertise. 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 con
14、fer immunity from legal obligations. Cross-reference International standard Corresponding British Standard ISO 5667-3:1994 BS 6068 Water quality Section 6.3:1986 Guidance on the preservation and handling of samples a a In preparation. The 1986 edition was identical with ISO 5667-3:1985. Summary of p
15、ages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, 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
16、.ISO10359-2:1994(E) BSI 07-1999 1 Introduction Fluoride ions occur in almost all ground and surface waters. Their concentration depends primarily on the hydrogeological conditions and is generally below 1mg/l. Certain industrial waste waters may also contain fluoride ions in higher concentrations. T
17、he fluoride concentration is also dependant on the type and concentration of cations present at the same time in water, such as Ca 2+ , Mg 2+ , Al 3+or Fe 3+ , which may form sparingly soluble compounds with fluoride ions or complexes of low dissociation grade. In addition, stable boron-fluoride com
18、plexes exist. Several different methods are available for determining fluoride and the choice of method depends on the type of problem posed as follows. a) Direct measurement using fluoride ion selective electrodes. This method is suitable for the determination of fluoride in drinking and surface wa
19、ter. It is included in ISO 10359-1. b) Determination of inorganically bound total fluoride using decomposition, distillation and potentiometric measurement. This method is included in this part of ISO 10359. 1 Scope 1.1 Field of application This part of ISO 10359 specifies a method for the determina
20、tion of inorganically bound total fluoride. The method is applicable to waste waters which are highly contaminated inorganically, with a fluoride ion concentration of morethan0,2mg/l. 1.2 Interferences Interferences caused by certain cations (seeintroduction) or boron, which may occur in the determi
21、nation of fluoride, need to be eliminated by distillation. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this part of ISO10359. At the time of publication, the edition indicated was valid. All standards are subject to
22、 revision, and parties to agreements based on this part of ISO10359 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 5667-3:1994, Water quality
23、Sampling Part3: Guidance on the preservation and handling of samples. 3 Principle Evaporation of the water sample to dryness in an alkaline medium. Fusing of the residue with sodium hydroxide. Separation of the fluoride by steam distillation in the presence of a phosphoric acid/sulfuric acid mixture
24、. Determination of the fluoride concentration in the distillate by means of a fluoride ionselective electrode(seeISO10359-1). 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Hydrochloric acid (HCl), =1,12g/m
25、l. 4.2 Phosphoric acid (H 3 PO 4 ), =1,71g/ml. 4.3 Sulfuric acid (H 2 SO 4 ), =1,64g/ml; 72,5%(V/V). 4.4 Sodium hydroxide (NaOH), solid. 4.5 Sodium hydroxide solution c(NaOH)=5mol/l. Dissolve cautiously 100g 0,5g of sodium hydroxide in water, cool and dilute to500ml. 4.6 Methyl red solution Dissolve
26、 0,2g of the sodium salt of methyl red (C 15 H 14 N 3 NaO 2 ) in100ml of ethanol. 4.7 Total ionic strength adjustment buffer (TISAB). Add58g of sodium chloride (NaCl) and57ml of glacial acetic acid (CH 3 COOH)=1,05g/ml to500ml of water in a1litre beaker. Stir until dissolved. Add150ml of the sodium
27、hydroxide solution(4.5) and4g of CDTA (trans-1,2-diaminocyclohexane-N,N,N,N- tetraacetic acid). Continue stirring until all the solids have dissolved and adjust the solution topH5,2 with sodium hydroxide solution using a pH-meter. Transfer to a1000ml one-mark volumetric flask, make up to the mark wi
28、th water and mix. The solution is stable for about6months, but do not use it if a precipitate forms. NOTE 1This solution is commercially available. 4.8 Fluoride, stock solution, =1000mg/l. Dry a portion of sodium fluoride (NaF) at150 C for4h and cool in a desiccator. Dissolve2,210g 0,001g of the dri
29、ed material in water contained in a1000ml one-mark volumetric flask. Make up to the mark with water and mix. Store the solution in a screw-capped polyethylene container. 4.8.1 Fluoride, working standard solutionI, =10mg/l.ISO10359-2:1994(E) 2 BSI 07-1999 Pipette10ml of the fluoride stock solution(4.
30、8) into a1000ml one-mark volumetric flask. Make up to the mark with water and mix. 4.8.2 Fluoride, working standard solutionII, =5mg/l. Pipette5ml of the stock solution(4.8) into a1000ml one-mark volumetric flask and make up to the mark with water. 4.8.3 Fluoride, working standard solutionIII, =1mg/
31、l. Pipette100ml of the working standard solutionI(4.8.1) into a1000ml one-mark volumetric flask and make up to the mark with water. 4.8.4 Fluoride, working standard solutionIV, =0,5mg/l. Pipette100ml of the working standard solutionII(4.8.2) into a1000ml one-mark volumetric flask and make up to the
32、mark with water. 4.8.5 Fluoride, working standard solutionV, =0,2mg/l. Pipette20ml of the working standard solutionI(4.8.1) into a1000ml one-mark volumetric flask and make up to the mark with water. All standard solutions are stored in plastics bottles and are usable for1month. 5 Apparatus Usual lab
33、oratory apparatus and 5.1 Meter, a millivoltmeter with an impedance of not lessthan10 12 7, capable of resolving potential differences of0,1mV or better. 5.2 Fluoride ion-selective electrode, which shall give stable readings. The e.m.f.response, using standard solutions, shall not be lessthan55mV pe
34、r decade change in fluoride concentration at25 C. 5.3 Reference electrode, either a calomel electrode, filled with saturated potassium chloride (KCl) solution, or a silver/silver chloride electrode shall be used. NOTE 2Single junction, sleeve type electrodes which reduce the liquid-liquid junction p
35、otential are preferable. 5.4 Measuring cells, of capacity100ml, made of polypropylene and fitted with a thermostatted jacket. 5.5 Water bath, capable of supplying water to the jacket of the measuring cell(5.4) at a temperature of25 C 0,2 C. 5.6 Magnetic stirrer, with a PTFE-coated stirring bar (PTFE
36、=polytetrafluoroethylene). 5.7 Polyethylene beaker, of capacity100ml. 5.8 Nickel dishes, of a suitable size up to a capacity of700ml. 5.9 Crucibles, of60ml nominal capacity, made of glazed porcelain or nickel. 5.10 Distillation apparatus, (for example as shown inFigure 1) made of borosilicate glass,
37、 suitable for steam distillation, consisting of a steam generating device, a250ml distillation flask, provided with a thermometer pocket with a14/23 standard joint accomodating a distillation head provided with a splash head and dropping funnel and a coiled coolant tube condenser (with a jacket leng
38、th of atleast30cm). The thermometer has a14/23 standard joint and shall be suitable for a temperature range upto200 C. 5.11 Heating device for the distillation flask, preferably an appropriately dimensioned heating jacket. 5.12 Round-bottomed flasks, of capacities500mland1000ml. 5.13 Volumetric flas
39、ks, of capacities100ml,250mland500ml. 5.14 One-mark bulb pipettes, of capacities10ml,20ml,25mland50ml. 5.15 Pipettes 5.16 Narrow-mouthed reagent bottles, of capacity500ml, made of brown glass. 6 Sampling and samples Samples shall be taken in polyethylene bottles which have been washed thoroughly and
40、 rinsed with fluoride-free water. No preservative is normally necessary but perform the analysis as soon as possible, preferably within3days. For further information on sample preservation seeISO5667-3. 7 Procedure 7.1 Evaporation and decomposition Transfer500ml of the water sample, which has been h
41、omogenized by shaking to a nickel dish(5.8). The fluoride concentration shall be between0,2mg/land2000 mg/l. For higher fluoride concentrations, take a suitably smaller volume. Adjust the pH of the water sample to11to12 by adding sodium hydroxide solution(4.5) and concentrate by evaporation to a vol
42、ume of approximately30ml. Transfer to a crucible(5.9) and carefully evaporate to dryness, avoiding overheating or splashing.ISO10359-2:1994(E) BSI 07-1999 3 Cover the residue with2g of sodium hydroxide(4.4). Heat the contents of the crucible to400Cto500 C (dull red heat) and wait for10min. Cool and
43、dissolve the melt in a small volume of water. 7.2 Distillation Transfer the dissolved melt(see7.1) to a distillation flask(see5.10), ensuring that the total volume does not exceed50ml. Connect the flask to the rest of the distillation apparatus(5.10). Using the dropping funnel, carefully add60ml of
44、sulfuric acid(4.3) and then10ml of phosphoric acid(4.2). Place a500ml volumetric flask containing20ml of sodium hydroxide solution(4.5) under the condenser outlet. Submerge the outlet tube of the condenser in the solution. Switch on the steam generator and the heating jacket(5.11) for the distillati
45、on flask. When the contents of the flask begin to boil, introduce steam. Continue heating until the contents of the distillation flask reach a temperature of155 C. Regulate the heating to keep this temperature approximately constant. Adjust the steam supply for a distillation rate of approximately10
46、ml/min. NOTE 3For larger series of analyses, it is advisable to replace the thermometer by a contact thermometer and to control the heating using a relay. Stop the distillation when the amount of distillate is approximately450ml. Rinse the condenser outlet tube inside and outside with a small volume
47、 of water. Neutralize the contents of the volumetric flask against methyl red(4.6) and make up to the mark with water. Figure 1 Example of a distillation apparatusISO10359-2:1994(E) 4 BSI 07-1999 NOTE 4Any interference caused by the distillation apparatus, which could lead to excessive fluoride conc
48、entrations after the distillation, can be eliminated by a blank distillation before carrying out the next determination. 7.3 Preparation for measurement Since the electrode characteristics of a fluoride ionselective electrode(5.2) generally vary in the course of time, check the calibration curve on
49、the day of use(see7.4). To improve the electrode response, condition the electrode prior to measurement in the following way. Prior to measurement, immerse the electrode for1h in the cell(5.4) which contains the reference solution5 (seeTable 1). After rinsing with the first solution to be measured, the electrode is ready for use. 7.4 Calibration Establish a calibration function using the five reference solutions in the corresponding concentration range. For the range0,2mg/lto10mg/l, proceed as follows: pipette25,0ml
