1、BRITISH STANDARD BS 6068-2.49: 1995 ISO10566: 1994 Water quality Part 2: Physical, chemical and biochemical methods Section 2.49 Determination of aluminium Spectrometric method using pyrocatechol violetBS6068-2.49:1995 This British Standard, having been prepared under the direction of the Health and
2、 Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 July 1995 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44/2 Draft for comment 92/54727 DC ISBN 0 580 24389 3 Committees responsible
3、 for this British Standard The preparation of this British Standard was entrusted by Technical Committee EPC/44, Water quality, to Subcommittee EPC/44/2, Physical, chemical and biochemical methods, upon which the following bodies were represented: The Association of the Laboratory Supply Industry Br
4、itish Agrochemicals Association Ltd. British Ceramic Research British Gas plc British Soft Drinks Association Ltd. Chemical Industries Association Convention of Scottish Local Authorities Department of the Environment (Water Directorate) Department of Trade and Industry (Laboratory of the Government
5、 Chemist) GAMBICA (BEAMA) Ltd. Industrial Water Society Institution of Water and Environmental Management National Rivers Authority Royal Society of Chemistry Soap and Detergent Industry Association Society of Chemical Industry Swimming Pool and Allied Trades Association Ltd. Water Companies Associa
6、tion Water Research Centre Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBS6068-2.49:1995 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative reference 1 3 Principl
7、e 1 4 Reagents 1 5 Apparatus 2 6 Sampling and samples 2 7 Interferences 3 8 Procedure 3 9 Calculation and expression of results 4 10 Precision data 4 11 Test report 4BS6068-2.49:1995 ii BSI 07-1999 National foreword This Section of BS6068 has been prepared by Subcommittee EPC/44/2 and is identical w
8、ith ISO10566:1994 Water quality Determination of aluminium Spectrometric method using pyrocatechol violet. It supersedes BS2690-106:1979 which is withdrawn. The international standard was prepared by ISO Technical Committee 147, Water quality, with the active participation and approval of the UK. BS
9、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 7, which, together with Part 0, are listed below. Part 0: Introduction; Part 1: Glossary; Part 2: Physic
10、al, chemical and biochemical 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 BS6068 should be carried out by suitably qualified persons with an appropriate
11、 level of chemical 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 o
12、f itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the a
13、mendment table on theinside front cover.ISO10566:1994(E) BSI 07-1999 1 Introduction Aluminium occurs in a variety of types of compounds in nature, and can be found in acid, neutral and alkaline solutions. It can also form colloidal polymeric solutions and gels, as well as flocculant precipitates, al
14、l based on aquated positive ions or hydroxylated aluminates. In addition, it can form complexes with organic acids and with ions such as fluoride, chloride and sulfate, most but not all of which are soluble. Aluminium can also form lattice compounds with oxygen (and hydroxyl species), silicon, and s
15、ome metals. Although insoluble, some of these compounds, notably the clays, micas and zeolites, can be found as fine suspended particles in rivers. Although they contain aluminium, these insoluble lattice compounds are not usually considered as aluminium compounds in the context of the water cycle.
16、The method described in this International Standard is restricted to the determination of the aquated cations and other forms of aluminium readily converted to that cationic form by acidification. The pretreatment with nitric acids is identical to that described in other International Standards usin
17、g spectrometric methods with an electrothermal atomization or inductively coupled plasma procedure (methods of preparation). 1 Scope 1.1 Type of sample The method is applicable to the analysis of potable waters, ground waters, and lightly polluted surface and sea waters. 1.2 Substance determined The
18、 method determines filterable (dissolved) and acid-soluble aluminium. 1.3 Range The method includes low range determination up to 100 4g/l Al with 50mm cells and high range determination up to 500 4g/l Al with 10mm cells. The effective range depends on the sensitivity of the spectrometer and can be
19、extended upwards by taking smaller test portions. 1.4 Limit of detection The limit of detection is 2 4g/l when cells of optical path length 50mm and a 25 ml test portion are used. 1.5 Sensitivity An aluminium concentration of 100 4g/l gives an absorbance of about 0,20 0,05 optical absorption units,
20、using a 25ml test portion and cells of optical path length 10mm. 1.6 Precision If not specified, the precision of volumes and masses mentioned in this International Standard is 1% of the value. 2 Normative reference The following standard contains provisions which, through reference in this text, co
21、nstitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of
22、the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 5667-3:1994, Water quality Sampling Part 3: Guidance on the preservation and handling of samples. 3 Principle For dissolved aluminium, the sample is filtered through membrane filte
23、rs with 0,454m pore size and then acidified with nitric acid to obtain a pH of 1,2 to 1,5. For acid-soluble aluminium, the untreated sample is acidified with nitric acid to obtain a pH of 1,2 to 1,5, kept for at least 1h at room temperature to dissolve the aluminium and then filtered. Aluminium is r
24、eacted with pyrocatechol violet at a pH of 5,9 0,1 followed by spectrometric measurement of the resulting coloured complex at a wavelength of 580nm (the blue colour is visible only at high aluminium concentrations). NOTE 1For other kinds of determination, e.g. digestions, the sample is pretreated ac
25、cordingly, using nitric acid at a pH of 1,2 to 1,5 in the final sample. 4 Reagents Use only reagents of recognized analytical grade. Ensure that the aluminium content is negligible compared with the smallest concentration to be determined in the samples. All reagent solutions shall be free of suspen
26、ded particles (dust) which can interfere with spectrometry. If necessary, filter through a membrane filter of pore size 0,45 4m. Solutions shall be stored in closed plastics laboratory bottles at room temperature, preferably not exposed to bright light. 4.1 Nitric acid (HNO 3 ), = 1,40 g/ml, 65% (V/
27、V). 4.2 Distilled or deionized water which is free from aluminium, i.e. aluminium content below 1 4g/l or below 1% of the range of determination.ISO10566:1994(E) 2 BSI 07-1999 4.3 Acidified water Add 4,0 ml of nitric acid (4.1) to 1000ml of water(4.2). 4.4 Mixed reagent Add 1,0ml of nitric acid (4.1
28、) to approximately 70ml of water (4.2) in a 200ml plastics laboratory beaker (5.3). To this solution, add 25,0g of magnesium sulfate heptahydrate MgSO 4 7H 2 O, 5,0 g of ascorbic acid (C 6 H 8 O 6 ), 0,25 g of 1,10-phenanthroline monohydrate C 12 H 8 N 2 H 2 O and 5,0ml of aluminium standard solutio
29、n (4.8). Transfer to a 100ml one-mark volumetric flask and make up to the mark with water. This solution is stable for one month. NOTE 2Accurate addition of the aluminium standard solution is essential in order to allow a linear calibration at low concentrations. 4.5 Pyrocatechol violet solution Car
30、efully dissolve 0,050g of pyrocatechol violet (C 19 H 14 O 7 S) 3,3, 4-trihydroxyfuchsine-2 -sulfonic acid in approximately 20ml of water. Transfer to a 100ml one-mark volumetric flask and make up to the mark with water (4.2). This solution is stable for one month. NOTE 3As pyrocatechol violet is a
31、dye which may vary with brand and batch, applicability should be checked with every new batch. As a guideline, a standard solution of 1004g/l Al should produce spectral absorption of about 0,20cm 1 0,05 cm 1using this method. 4.6 Hexamine buffer solution Dissolve 210g hexamethylene-tetramine (C 6 H
32、12 N 4 ) in approximately 200ml of water (4.2). Transfer the solution to a 500ml one-mark volumetric flask and make up to the mark with water. This solution is stable for at least 2 months. NOTE 4This solution is close to saturation. It should be kept above 15 C to prevent crystallization. Some bran
33、ds of hexamine contain dust particles, in which case the buffer should be filtered after preparation. 4.7 Aluminium stock solution, 1000mg/l. Weigh 100mg of aluminium foil to a precision of 0,5mg. Dissolve the aluminium in a 100ml one-mark volumetric flask, using 1ml of nitric acid(4.1) and a few mi
34、llilitres of water (4.2). When dissolution is complete, make up to the mark with water. NOTE 5Commercially available aluminium standard solutions may be used. The solution is stable at room temperature, unless no loss from evaporation occurs. 4.8 Aluminium standard solution, 10mg/l. Pipette 1,00ml o
35、f aluminium stock solution (4.7) into a 100ml one-mark volumetric flask and make up to the mark with acidified water (4.3). 4.9 Sodium hydrogen carbonate, 2,0mol/l solution. Dissolve 85g of sodium hydrogen carbonate (NaHCO 3 ) in about 400ml of water. Transfer the solution to a 500ml one-mark volume
36、tric flask and make up to the mark with water (4.2). NOTE 6This reagent is used to raise the pH of the sample when it is below 1,2 (e.g. from digestion). Sodium hydroxide (NaOH) is not recommended because even analytical grades may contain aluminium, while sodium hydrogen carbonate is extremely low
37、in aluminium, particularly the pharmaceutical grades. 5 Apparatus Ordinary laboratory equipment and 5.1 Spectrometer, capable of operating at a wavelength of 580nm and equipped with cells of optical path length 10mm and 50mm. Other cell path lengths may be used with appropriate calibration ranges. N
38、OTE 7The sensitivity and precision of this method also depends on the performance of the spectrometer. 5.2 Filtration device, fitted with membrane filters with an average pore size of 0,454m. 5.3 Plastics laboratory beakers, e.g. of capacity 100ml, 200ml or 500ml. 5.4 One-mark volumetric plastics fl
39、asks, e.g. of capacity 100ml, 200ml or 500ml. 5.5 Capped sample bottles, e.g. of capacity 100 ml or 500 ml, made of plastics laboratory ware. Soak new plastics laboratory ware in 10% (V/V) nitric acid nitric acid (4.1) diluted 1:10 with water (4.2), rinse and store overnight in acidified water (4.3)
40、. Check suitability by running test samples with stored water; the aluminium content should be below 24g/l. Reserve the plastics ware and optical cells, if possible, solely for aluminium determinations. Remove all residual aluminium from previous determinations by cleaning all plastics ware and opti
41、cal cells by filling with, or soaking in, acidified water (4.3) overnight. Do not use detergent or chromic acid. 5.6 pH-metre 5.7 Microlitre pipettes, with disposable tips. 6 Sampling and samples See ISO5667-3. Collect samples in polyethylene bottles. Clean the sample bottles and filtration device a
42、ccording to the procedure described in clause 5. 6.1 Filtrable aluminium Immediately after sampling, filter the sample through a membrane filter (5.2). Acidify the filtrate by adding 0,30ml of nitric acid (4.1) per 100ml of sample.ISO10566:1994(E) BSI 07-1999 3 6.2 Acid-soluble aluminium Add 0,30ml
43、of nitric acid (4.1) per 100ml of sample. The pH shall be 1,2 to 1,5, if not, add more acid. Store for at least 1h at room temperature and filter the sample through a membrane filter (5.2). For special purposes other pretreatment procedures may be used (seeclause 7). NOTE 8Failure of proper acidific
44、ation of the sample leads to incorrect results because the pH during reaction and measurement is not buffered to the correct value. If the pH of the sample solution is too low, it may be increased by addition of the sodium hydrogen carbonate solution (4.9). 7 Interferences The most important interfe
45、rence with micro-determinations of aluminium is the release of aluminium from the surface of the vessels used for sampling and handling. In particular, aluminium is easily leached from most items of glassware. Thus, glassware shall not be used for aluminium determinations in the range below 50 4g/l
46、Al. It is strongly recommended to use only plastics laboratory ware pretreated as described in clause 5. Fluoride ions form stable complexes with aluminium, thus preventing the formation of the aluminium-pyrocatechol violet complex. The resulting negative bias interferes especially at low aluminium
47、concentrations. This effect is almost totally eliminated by the addition of magnesium ions (see4.4) which form relatively strong complexes with fluoride. Iron forms a coloured complex with pyrocatechol violet. Interference effects caused by iron are minimized by reduction to the ferrous state follow
48、ed by complexing with 1,10-phenanthroline. This iron complex gives rise to a very small absorbance at 580nm. 1,0mg/l of iron is equivalent to 0,054g/l of aluminium. Coloured compounds, inorganic as well as organic, that give an absorbance at 580nm generally interfere with this determination, when ab
49、sorbance exceeds 0,050cm 1 . An oxidative digestion can destroy the coloured species and allow proper determination. Humic substances and other organic compounds with complexing properties can interfere. Interference is evident when addition of aluminium to the sample gives a smaller increase in absorbance than expected for that additional amount. This kind of interference is eliminated by digestion with H 2 O 2and HNO 3 . 8 Procedure Depending on the cell path length and sensitivity of the spectrometer, the procedure compr
