1、BRITISH STANDARD BS 6068-2.40: 1991 ISO 9390:1990 Water quality Part 2: Physical, chemical and biochemical methods Section 2.40 Method for the determination of borate by spectrometry using azomethine-HBS6068-2.40:1991 This British Standard, having been prepared under the directionof the Environment
2、andPollution Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 28 June1991 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment 88/52170 DC ISBN 0 580 19665 8 Committees
3、responsible for this British Standard The preparation of this British Standard was entrusted by the Environment and Pollution Standards Policy Committee (EPC/-) to Technical Committee EPC/44, upon which the following bodies were represented: Association of Consulting Scientists British Association f
4、or Chemical Specialists British Gas plc Chemical Industries Association Department of the Environment for Northern Ireland Department of the Environment (Water Directorate) Department of Trade and Industry (Laboratory of the Government Chemist) Electricity Supply Industry in England and Wales Indust
5、ry Water Society Institute of Petroleum Institution of Gas Engineers 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
6、 Industry Association Water Companies Association Water Research Centre Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBS6068-2.40:1991 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 No
7、rmative reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 3 9 Test report 3 Table 1 Precision data 4 Publication(s) referred to Inside back coverBS6068-2.40:1991 ii BSI 07-1999 National foreword This Section of BS6068, which has been
8、prepared under the direction of the Environment and Pollution Standards Policy Committee, is identical with ISO9390:1990 “Water quality Determination of borate Spectrometric method using azomethine-H”, published by the International Organization for Standardization (ISO). The international standard
9、was prepared by subcommittee2, Physical, chemical and biochemical methods, of ISO Technical Committee147, Water quality, with the active participation and approval of the UK. NOTEThe tests described in this Section of BS6068 should only be carried out in laboratories with suitable facilities and by
10、suitably qualified persons with an appropriate level of chemical expertise. Standard chemical procedures should be followed throughout. BS6068 is being published in a series of Parts subdivided into Sections that will generally correspond to particular international standards. Sections are being, or
11、 will be, published in Parts1 to7, which together with Part0, 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; Part 7: Precision a
12、nd accuracy. 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. In4.1, line4, “L + ascorbic acid” should be
13、read as “L (+) ascorbic acid”. In4.2, at the end of line3, insert “(produced by carefully mixing together20ml of sulfuric acid ( =1.84g/ml) and80ml of distilled water)” after “( =1.21g/ml)”. In line6, (C 10 H 14 N 2 Na 2 O 8 H 2 O) should be read as “(C 10 H 14 N 2 Na 2 O 8 H 2 O)”. In the title of7
14、.4.3, “facteur” should be read as “factor”. In Table 1, the numerical values for “ r ” and “ R ” should be transposed, and in column10 delete “mgl” and insert “mg/l”. Additional information. It is recommended that the pH value of the resulting solution from4.2 is checked before the solution is used.
15、 In7.2, line4, “per10mm” means per10mm of cell path length. In8.1, definition of A 0 , it is the absorbance of the blank using the same optical cell path length as for the sample. In Table 1, the standard deviations are based on the mean values. Cross-reference International standard Corresponding B
16、ritish Standard ISO 5667-3:1985 BS6068 Water quality Section 6.3:1986 Guidance on the preservation and handling of samples (Identical)BS6068-2.40:1991 BSI 07-1999 iii The international standard has an introduction which is as follows. “The natural borate content of ground water and surface water is
17、small. The borate content of surface water can be significantly increased due to waste water discharges, because borate compounds are ingredients of domestic washing agents.” A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are res
18、ponsible 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, pages1to4, an inside back cover and a back cover. This standard has been
19、 updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankISO9390:1990(E) BSI 07-1999 1 1 Scope 1.1 Application range This International Standard specifies a spectrometric method for the determination of bo
20、rate in water. The method is applicable to the determination of borate in concentrations between0,01mg and1mg of boron per litre. The working range may be extended by dilution. This method is applicable to potable water, and to ground, surface and saline waters that are not heavily polluted. 1.2 Int
21、erferences Interferences are unlikely when analysing drinking water. Mg, Zn, Ca, Na, K, phosphate, sulfate, and nitrate are known not to interfere. Mn, Zr, Cr, Ti, Cu, V, Al, Be, and Fe may cause high results. Interference by the presence of colouration, humic acid, and/or undissolved substances may
22、 be removed by suitable procedures (e.g.destruction of the colour, filtration through a column filled with activated carbon). 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of p
23、ublication, 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 the standard indicated below. Members of IEC and ISO maintain regist
24、ers of currently valid International Standards. ISO5667-3:1985, Water quality Sampling Part3: Guidance on the preservation and handling of samples. 3 Principle Reaction of azomethine-H, which is the condensation product of H-acid (8-amino-naphth-1-ol-3,6-disulfonic acid) and salicylaldehyde, with di
25、ssolved forms of borate at a pH of about6. Formation of a yellow complex that is measured spectrometrically at the absorption maximum in the range of410nm to420nm (seealso7.1). 4 Reagents Use only reagents of recognized analytical grade and only distilled water or water of equivalent purity stored i
26、n polyethylene bottles. 4.1 Azomethine-H, solution Dissolve1,0g of azomethine-H sodium salt 8-N-(2-hydroxybenzylidene)-amino-naphth-1-ol- 3,6-disulfonic acid 1)(C 17 H 12 NNaO 8 S 2 ) and3,0g of L+ ascorbic acid (C 6 H 8 O 6 ) in water and dilute to100ml in a one-mark volumetric flask. The solution
27、is stable for up to a week when stored in a polyethylene bottle at a temperature of between4C and6C. 4.2 Buffer solution, pH = 5,9 Mix250g of ammonium acetate (CH 3 COONH 4 ),250ml of water,80ml of sulfuric acid (H 2 SO 4 ) ( =1,21g/ml),5ml of phosphoric acid (H 2 PO 4 ) ( =1,71g/ml),1,0g of citric
28、acid (C 6 H 8 O 7 H 2 O) and1,0g of disodiumethylenediamine-tetraacetic acid-dihydrate (C 10 H 14 N 2 Na 2 O 8 H 2 O) by stirring and gentle heating. 4.3 Reagent solution Mix equal volumes of reagents4.1 and4.2. Prepare this solution on the day of use and store in a polyethylene bottle. 4.4 Borate,
29、stock solution corresponding to1,0g of Bper litre. Dissolve5,719g of boric acid (H 3 BO 3 ) in1000ml of water. Store in a polyethylene bottle. 1ml of this stock solution contains1,0mg of borate, expressed as B. 4.5 Boron, standard solution1 corresponding to10,0mg of B per litre. Dilute10ml of borate
30、 stock solution(4.4) to1000ml with water. 1ml of this standard solution contains10,04g of borate, expressed as B. 4.6 Boron, standard solution2 corresponding to1,0mg of B per litre. Dilute10ml of borate standard solution(4.5) to100ml with water. 1ml of this standard solution contains1,04g of borate,
31、 expressed as B. 4.7 Calcium hydroxide Ca(OH) 2 1) IUPAC name.ISO9390:1990(E) 2 BSI 07-1999 5 Apparatus Ordinary laboratory apparatus made of polypropylene, polyethylene or polytetrafluoroethylene, where applicable, and Spectrometer, for use in the wavelength range of410nm to420nm, with cells of an
32、optical path length between10mm and50mm. 6 Sampling and samples Samples for the determination of borate shall not be taken using borosilicate glass containers. The samples shall be preserved according to ISO5667-3. 7 Procedure 7.1 Determination Transfer25,0ml of the sample, or a smaller amount of th
33、e sample diluted to25ml with distilled water, into a100ml polyethylene flask. Add10ml of azomethine-H reagent(4.1). Mix and allow to stand in the dark for2h at20C 1C, then measure the absorbance at the absorption maximum in the range of410nm to420nm against distilled water in a cell of optical pathl
34、ength10mm, using the spectrometer set up according to the manufacturers instructions and after setting the zero with distilled water in the cell. Alternatively use a cell of50mm optical pathlength for low boron concentrations of up to about0,2mg of boron per litre. Check the wavelength of the absorp
35、tion maximum whenever a new batch of this reagent is used. NOTE 1The reaction time may be shortened by keeping the treated sample at a temperature of30C. In this case, the sample, the blank and the calibration samples should be treated accordingly, because the intensity of colour is temperature depe
36、ndent. 7.2 Blank test Carry out a blank test by treating25ml of water as described in7.1. Ensure that the blank value is in the range of0,1 absorption units to0,17 absorption units per10mm; if the absorption is higher then check the reagents and the distilled water for their borate content. NOTE 2Th
37、e following procedure may be used to check the quality of reagents and the distilled water. Measure into three separate borate-free beakers (preferably polytetrafluorethylene)25ml,100ml and250ml aliquots of the distilled water. Make each slightly alkaline by the addition of the same small (e.g.200mg
38、) amount of calcium hydroxide(4.7) to each. Evaporate the100ml and250ml aliquots to a volume of just less than25ml and adjust their volumes to precisely25ml by the addition of a little extra distilled water, as necessary. Carry out the procedure given in7.1 on these aliquots. Carry out a blank deter
39、mination with each of the aliquots. If borate is present in the distilled water, the borate found increases in proportion to the volume of the aliquot taken. Erratic results indicate external borate contamination. Relatively high but constant results indicate impure reagents. 7.3 Prevention of conta
40、mination As borate is widespread in the environment, significant contamination may occur during trace determinations. The following sources of contamination, and remedies, should be considered. Laboratory glassware is usually made from borosilicate glass. Special borate-free thermally resistant glas
41、s is obtainable, but for routine purposes, old borosilicate glass, well rinsed in hydrochloric acid, may be used for acidic solutions, but should never be used for neutral or alkaline solutions, or for prolonged storage at any pH value. (Borosilicate glassware previously used with alkaline solutions
42、 shall not be used without very thorough acid rinsing.) Polyethylene flasks and plastics pipettes are preferable. Detergents and soaps used for glassware and labcoats should be borate free, and the use of towels and tissues for drying shall be avoided. Toiletries, talcum powder and cosmetics used by
43、 technicians often contain borate and should be avoided or removed, especially prior to undertaking accurate low-level determinations. Water and reagents may contain borate and blanks should be carried out at least in duplicate and should agree. 7.4 Calibration 7.4.1 0,00 mg/l to 0,20 mg/l of boron
44、calibration graph To a series of six25ml one mark plastics flasks add respectively0ml,1ml,2ml,3ml,4ml and5ml of boron standard solution2(4.6), dilute to the mark with distilled water and mix. This gives concentrations of 0 mg; 0,04mg; 0,08mg; 0,12mg; 0,16mg and0,20mg of boron per litre respectively.
45、 Analyze each standard solution as described in7.1, measuring the absorbance values in a50mm optical path length cell compared against distilled water. Prepare a calibration graph by plotting the absorbance values against the known concentrations in milligrams of boron per litre for each standard.IS
46、O9390:1990(E) BSI 07-1999 3 7.4.2 0,00 mg/l to 1,00 mg/l of boron calibration graph Repeat the above calibration, using0ml,5ml,10ml, 15ml, 20 ml and25ml of boron standard solution2(4.6) respectively to give concentrations of0mg;0,2mg;0,4mg;0,6mg;0,8mg and1,0mg of boron per litre respectively. Analyz
47、e each standard solution as described in7.1 but this time measuring the absorbance values using a10mm optical path length cell compared against distilled water. Prepare a separate calibration graph. 7.4.3 Calculation of facteur R 2) It is essential that a linear calibration graph be achieved in both
48、 cases; if not then check the solutions and repeat the calibration. Calculate the reciprocal value for the slope, factor R, for each graph. 8 Expression of results 8.1 Calculation Calculate the borate content, in milligrams of boron per litre, from the formula where 8.2 Precision An interlaboratory
49、trial, carried out in Germany, F.R., delivered the values for boron given in Table 1. 9 Test report The test report shall include the following information: a) a reference to this International Standard; b) all information necessary for the complete identification of the sample; c) the results and the method of expression used; d) details of the removal of interferences, where applicable; e) details of any operations not included in this International Standard, or regarded as optional, together with any other circumstances
