1、BRITISH STANDARD BS 7755-3.6: 1995 ISO 11263: 1994 Soil quality Part 3: Chemical methods Section 3.6: Determination of phosphorus Spectrometric determination of phosphorus soluble in sodium hydrogen carbonate solutionBS7755-3.6:1995 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/48/3 Draft for comment 93/505280 DC ISBN 0 580 24130 0 Commit
3、tees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee EPC/48, Soil quality, to Subcommittee EPC/48/3, Chemical methods, upon which the following bodies were represented: Association of Consulting Scientists Association of Public Anal
4、ysts British Ceramic Research Ltd. British Gas plc British Society of Soil Science Department of the Environment (Drinking Water Inspectorate) Department of Trade and Industry (Laboratory of the Government Chemist) National Rivers Authority Royal Society of Chemistry Society of Chemical Industry Soi
5、l Survey and Land Research Centre Water Research Centre Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBS7755-3.6:1995 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative reference
6、s 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Procedure 2 7 Repeatability 3 8 Test report 3 Annex A (informative) Bibliography 4 Table 1 Standard stock solutions and concentrations of phosphorus 2 Table 2 Repeatability 3 List of references Inside back coverBS7755-3.6:1995 ii BSI 07-1999 National fo
7、reword This Section of BS 7755 has been prepared by Subcommittee EPC/48/3. It is identical with ISO 11263:1994 Soil quality Determination of phosphorus Spectrometric determination of phosphorus soluble in sodium hydrogen carbonate solution, published by the International Organization for Standardiza
8、tion (ISO). ISO11263 was prepared by Subcommittee3, Chemical methods, of Technical Committee ISO/TC 190, Soil quality, with the active participation and approval of the UK. BS7755 is being published in a series of Parts subdivided into Sections and Subsections that will generally correspond to parti
9、cular international standards. Other Parts of BS7755 are, or will be, as follows. Part 1: Terminology and classification; Part 2: Sampling; Part 3: Chemical methods; Part 4: Biological methods; Part 5: Physical methods. Textual error. When adopting the text of the international standard, the followi
10、ng textual error was discovered. It has been marked in the text and has been reported to ISO in a proposal to amend the text of the international standard. In 6.4.1, line2, “for 30min” should read “within 30min.” Additional information In 4.1.3, it is important that low phosphorus activated charcoal
11、 is used as charcoal derived from bone contains large quantities of phosphorus and is unsuitable for use in this method. In 6.5, if the absorbance is greater than that of the highest standard solution, then the solution needs diluting accordingly thereby necessitating the use of the dilution factor
12、d in the calculation. 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. Cross-references In
13、ternational standard British Standard ISO 3696:1987 BS 3978:1987 Specification for water for laboratory use (Identical) BS 7755 Soil quality ISO 11464:1994 Section 3.5:1995 Pretreatment of samples for physico-chemical analyses (Identical) ISO 11465:1993 Section 3.1:1994 Determination of dry matter a
14、nd water content on a mass basis by a gravimetric method (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments inc
15、orporated. This will be indicated in the amendment table on theinside front cover.ISO11263:1994(E) BSI 07-1999 1 1 Scope This International Standard specifies an extraction method and analytical conditions to determine the content of soil phosphorus soluble in sodium hydrogen carbonate solution. Aft
16、er the extraction step, two different methods of colour development are possible. Subclause 4.2 specifies colour development at room temperature. Subclause 4.3 specifies colour development after heating to a high temperature. This International Standard is applicable to all types of soils. 2 Normati
17、ve references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Internat
18、ional Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 3696:1987, Water for analytical laboratory use Specification and test methods.
19、 ISO 11464:1994, Soil quality Pretreatment of samples for physico-chemical analyses. ISO 11465:1993, Soil quality Determination of dry matter and water content on a mass basis Gravimetric method. 3 Principle A soil, pretreated according to ISO11464, is treated with a 0,5mol/l sodium hydrogen carbona
20、te solution at pH8,50 to reduce the concentration of calcium, aluminium and iron(III) ions by precipitation of calcium carbonate and aluminium and iron(III) hydroxides and to release phosphate ions into solution. The clear extract is analysed for phosphorus by a spectrometric method involving the fo
21、rmation of an antimony-phosphate-molybdate complex (at room temperature, 4.2) or a phosphate-molybdate complex (at a high temperature, 4.3) both reduced with ascorbic acid to form a deep-coloured, blue complex. 4 Reagents All reagents shall be of recognized analytical grade. Use water complying with
22、 grade2of ISO3696. 4.1 Reagents used in both colour developments 4.1.1 Sodium hydroxide solution, c(NaOH) = 1mol/l. Dissolve 40,0g 0,4g of sodium hydroxide (NaOH) pellets in water. Cool and dilute to 1000ml with water. Store in an inert and hermetically sealed bottle. 4.1.2 Extracting solution Disso
23、lve 42,0g 0,1g of sodium hydrogen carbonate (NaHCO 3 ) in 800ml of water. Adjust the pH to 8,50 0,02 with sodium hydroxide solution(4.1.1).Transfer the solution into a1000ml volumetric flask and make up to the mark with water. NOTE 1This reagent shall be used within 4h of preparation. 4.1.3 Carbon,
24、activated, allowing the absorbance of the blank, A B , to be less than 0,015. Otherwise prepare carbon as follows. Weigh 100g 1g of carbon in a 1000ml beaker and add 400ml of extracting solution (4.1.2). Stir on a magnetic stirrer for 2h. Filter on phosphorus-free paper and repeat the washing, using
25、 the same volume of extracting solution. Filter again and wash the carbon with water until the pH of the washings is 7,0 0,1. Dry the carbon at 105 C 2 C. 4.1.4 Sulfuric acid, = 1,84g/ml. 4.1.5 Sulfuric acid, dilute, c(H 2 SO 4 ) = 5mol/l. Pour 400ml 10ml of water into a 1000ml beaker. Cautiously ad
26、d 278ml 5ml of sulfuric acid (4.1.4) while stirring continuously. Cool to 20 C 5 C and make up to the mark with water. 4.1.6 Sulfomolybdic reagent Pour about 400ml of water into a 1000ml beaker. Cautiously add 278ml 5ml of sulfuric acid (4.1.4) while stirring continuously. Cool to 50 C. Then add 49,
27、08g 0,01g of ammonium heptamolybdate tetrahydrate (NH 4 ) 6 Mo 7 O 24 4H 2 O and stir until dissolved. Cool to 20 C 5 C and make up to the mark with water. NOTE 2If stored in an amber glass bottle, this reagent is stable for many years. 4.1.7 Orthophosphate standard stock solution, containing 450mg/
28、l of phosphorus. Weigh 1,976g 0,001g of potassium dihydrogen phosphate (KH 2 PO 4 ), dried in an oven for 2h at105 C 1 C, into a 1000ml volumetric flask. Dissolve and make up to the mark with water. NOTE 3If stored at 4 C, this solution is stable for 3months.ISO11263:1994(E) 2 BSI 07-1999 4.1.8 Stan
29、dard solutions Pipette volumes (as shown in Table 1) of the standard stock solution (4.1.7) into a set of flasks of 1000ml nominal volume. Make up to volume with the extracting solution (4.1.2). These solutions are stable for 1month. Table 1 Standard stock solutions and concentrations of phosphorus
30、4.2 Reagents used for colour development at room temperature 4.2.1 Sodium thiosulfate solution, 12g/l. Dissolve 1,20g 0,01g of sodium thiosulfate pentahydrate (Na 2 S 2 O 3 5H 2 O) in 100ml of water. Add 50mg 1mg of sodium carbonate (Na 2 CO 3 ) as a preservative. This solution shall be freshly prep
31、ared before use. 4.2.2 Sodium metabisulfite solution, 200g/l. Dissolve 20,0g 0,1g of sodium metabisulfite (Na 2 S 2 O 5 ) in 100ml of water. This solution shall be freshly prepared before use. WARNING Sodium metabisulfite produces gas that is dangerous when inhaled. 4.2.3 Potassium antimony(III) oxi
32、de tartrate solution, 0,5g/l. Dissolve 0,500g 0,01g of potassium antimony(III) oxide tartrate hemihydrate K(SbO)C 4 H 4 O 6 0,5H 2 O in 1000ml of water. WARNING Antimony compounds are highly toxic. 4.2.4 Colour reagent Dissolve 1,00g 0,01g of ascorbic acid (C 6 H 8 O 6 ) in 525ml of water. Then add
33、10ml of dilute sulfomolybdic reagent (4.1.6), 15ml of dilute sulfuric acid (4.1.5), and 50ml of potassium antimony(III) oxide tartrate solution (4.2.3). Mix well. The volume obtained is approximately 600ml. This reagent must be used within 30min of preparation. 4.3 Reagents used for colour developme
34、nt at high temperatures 4.3.1 Colour reagent Dissolve 1,00g 0,01g of ascorbic acid (C 6 H 8 O 6 ) and 50mg 0,5mg of sodium thiosulfate pentahydrate (Na 2 S 2 O 3 5H 2 O) in 720ml of water. Then add 15ml of sulfomolybdic reagent (4.1.6), and 65ml of dilute sulfuric acid (4.1.5). Mix well. The volume
35、obtained is approximately 800ml. This reagent must be used within 30min of preparation. 5 Apparatus Usual laboratory equipment and 5.1 Apparatus used in both colour developments 5.1.1 Analytical balance, with a readability of 0,001g. 5.1.2 Shaker (to prevent settling of the soil in the extracting so
36、lution). 5.1.3 pH-meter, with a readability of 0,01pH units. 5.1.4 Spectrometer, capable of measuring the absorbance in wavelengths up to 900nm and accepting optical cells of path length 10mm (readability of 0,001units of absorbance). 5.1.5 Optical cells, of path length 10mm. 5.2 Apparatus used in t
37、he colour development at high temperatures 5.2.1 Vortex stirrer 5.2.2 Water bath 6 Procedure 6.1 Determination of dry mass Pretreat the soil sample according to ISO11464. Determine the dry mass of the pretreated sample according to ISO11465. 6.2 Extraction Weigh 5,00g 0,01g of pretreated soil into a
38、 250ml flask. Add 1,0g of activated carbon (4.1.3) and 100ml 0,5ml of extracting solution (4.1.2). Stopper the flask and place it immediately on the shaker (5.1.2). Shake for exactly 30min at 20 C 1 C (shaking has to prevent settling of the soil in the extracting solution). Within 1min after shaking
39、 has ended, filter immediately into a dry vessel using a phosphorus-free paper. Prepare a blank by following the above procedure and excluding soil. Standard stock solution ml Concentration of phosphorus mg/l 0,000 0,000 1,000 0,45 5,00 2,25 10,00 4,50 20,00 9,00ISO11263:1994(E) BSI 07-1999 3 6.3 Co
40、lour development 6.3.1 Colour development at room temperature Into a set of 50ml volumetric flasks, transfer 5,00ml of either a blank solution prepared according to6.2, or a soil extract prepared according to6.2, or standard solutions according to 4.1.8. Then carefully add 0,5ml of dilute sulfuric a
41、cid(4.1.5) to each unstoppered flask and gently swirl to liberate the carbon dioxide. Add 4,0ml of sodium metabisulfite solution (4.2.2) and 6,0ml of sodium thiosulfate solution (4.2.1). Stopper the flask immediately. Mix well and wait for 30min. Then add 30,0ml of colour reagent(4.2.4), make up to
42、the mark with water, stopper the flask and mix well. Wait for 60min to allow the colour to develop. 6.3.2 Colour development at high temperatures Into a set of tubes, transfer 2,00ml of either a blank solution prepared according to 6.2, or a soil extract prepared according to 6.2, or standard soluti
43、ons according to 4.1.8. Then add 8,0ml of colour reagent (4.3.1) to each tube and mix well. Wait for 60min. Place the tubes in the water bath (5.2.2) at 90 C for 10min to allow the colour to develop. Cool the tubes to 20 C and mix using a vortex stirrer (5.2.1). 6.4 Spectrometric measurement Measure
44、ment shall be carried out within the linear part of the calibration curve. 6.4.1 Spectrometric measurement after colour development at room temperature Measure the absorbance of each solution against water at 880nm using optical cells (5.1.5) for 30min 1)after colour development. Record the values.
45、NOTE 4A wavelength of 710nm can be used if a loss of sensitivity can be accepted and after checking linearity and freedom from bias error. 6.4.2 Spectrometric measurement after colour development at high temperatures Measure the absorbance of each solution against water at 825nm using optical cells
46、(5.1.5). Record the values. 6.5 Calculation The content of phosphorus soluble in sodium hydrogen carbonate, in milligrams per kilogram of dried soil, is calculated using the following equation where 7 Repeatability The repeatability of the determination of phosphorus soluble in sodium hydrogen carbo
47、nate solution carried out following colour development at room temperature, or colour development after heating to a high temperature, shall satisfy the conditions given in Table 2. Table 2 Repeatability 8 Test report The test report shall contain the following information: a) a reference to this In
48、ternational Standard; b) a reference to the method used; c) all information necessary for complete identification of the sample; d) the results of the determination in whole numbers, in milligrams of phosphorus per kilogram, calculated on the basis of oven-dried soil; e) any details of operations ri
49、ot specified in this International Standard or which are regarded as optional, as well as any other factor which may have affected the results. 1) See national foreword for details of textual error. P is the phosphorus concentration, in milligrams per litre, in the chosen standard solution (see Table 1); A ES is the absorbance of the soil extract; A B is the absorbance of the blank; A S is the absorbance of the chosen standard solutio
