BS EN 1233-1997 Water quality - Determination of chromium - Atomic absorption spectrometric methods《水质 铬测定 原子吸收光谱测定法》.pdf

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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 1233 : 1997 BS 6068

2、 : Section 2.38 : 1997 The European Standard EN 1233 : 1996 has the status of a British Standard ICS 13.060.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Water quality Determination of chromium Atomic absorption spectrometric methodsBS EN 1233 : 1997 This British Standard

3、, having been prepared under the direction of the Health and Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 January 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference EH/3/2 Draft for com

4、ment 93/508225 DC ISBN 0 580 26789 X Amendments issued since publication Amd. No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee EH/3, Water quality, to Subcommittee EH/3/2, Physical, chemical and bioc

5、hemical methods, upon which the following bodies were represented: British 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 Direct

6、orate) Environment agency GAMBICA (BEAMA Ltd.) Industrial Water Society Laboratory of the Government Chemist Royal Society of Chemistry Soap and Detergent Industry Association Society of Chemical Industry Swimming Pool and Allied Trades Association Ltd. Water Companies Association Water Research Cen

7、tre Water Services Association of England and WalesBS EN 1233 : 1997 BSI 1997 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Method Introduction 3 1 Scope 3 2 Normative references 3 3 Determination of chromium by flame atomic absorption spectrometry 3 4 Det

8、ermination of chromium by electrothermal atomization atomic absorption spectrometry 6 Annex A (informative) Information on pretreatment and digestion of sludge and sediment samples 8 Tables 1 Precision data for clause 3 5 2 Interfering ions 5 3 Precision data for clause 4 7ii BSI 1997 BS EN 1233 : 1

9、997 National foreword This British Standard has been prepared by Technical Committee EH/3 and is the English language version of EN 1233 Water quality Determination of chromium Atomic absorption spectrometric methods, published by the European Committee for Standardization (CEN). It supersedes BS 60

10、68 : Section 2.38 : 1990, which is withdrawn. NOTE. The tests described in this British Standard should only be carried out by suitably qualified persons with an appropriate level of chemical expertise. Standard chemical procedures should be followed throughout. Cross-references Publication referred

11、 to Corresponding British Standard BS 6068 Water quality Part 6 Sampling EN 25667-2 : 1993 Section 6.2 : 1991 Guidance on sampling techniques ISO 5667-3 : 1994 Section 6.3 : 1996 Guidance on the preservation and handling of samples Compliance with a British Standard does not of itself confer immunit

12、y from legal obligations.CEN European Committee for Standardization Comite Europe en de Normalisation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1996 All rights of reproduction and communication in any form and by any means reserved in all countries t

13、o CEN and its members Ref. No. EN 1233 : 1996 E EUROPEAN STANDARD EN 1233 NORME EUROPE ENNE EUROPA ISCHE NORM July 1996 ICS 13.060.40 Descriptors: water, quality, chemical analysis, determination of content, chromium, atomic absorption spectrometry English version Water quality Determination of chro

14、mium Atomic absorption spectrometric methods Qualite de leau Dosage du chrome Me thodes par spectrome trie dabsorption atomique Wasserbeschaffenheit Bestimmung von Chrom Verfahren mittels Atomabsorptionsspektrometrie This European Standard was approved by CEN on 1996-05-16. CEN members are bound to

15、comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central

16、 Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the

17、 official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.Page 2 EN 1233 : 1996 BSI 1997 Foreword This European St

18、andard has been prepared by the Technical Committee CEN/TC 230, Water analysis, the Secretariat of which is held by DIN. Annex A is informative. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by Jan

19、uary 1997, and conflicting national standards shall be withdrawn at the latest by January 1997. In accordance with the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland,

20、France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. On the elaboration of this European Standard, the revision of the International Standard ISO 9174 has been started simultaneously with the intention to harmoniz

21、e both standards.Page 3 EN 1233 : 1996 BSI 1997 Introduction Chromium occurs in water in the oxidation states III and VI. The two methods described determine chromium in both oxidation states, either as acid soluble chromium or as water soluble chromium, depending on the sample pretreatment. The met

22、hod chosen depends on the concentration of chromium in the water to be examined. Some information is given in an informative annex on pretreatment and digestion of chromium from sludges and sediments. 1 Scope This European Standard specifies two methods for the determination of chromium in water by

23、atomic absorption spectrometry. The two methods are covered in separate clauses as follows: clause 3: Determination of chromium by flame atomic absorption spectrometry; clause 4: Determination of chromium by electrothermal atomization atomic absorption spectrometry. Clause 3 is applicable to the ana

24、lysis of water and waste water when the concentration range is between 0,5 mg/l and 20 mg/l of chromium. When the concentration is below 0,5 mg/l, the determination can be carried out after carefully evaporating an acidified sample to small volume, taking care to avoid the formation of a precipitate

25、. WARNING: The use of evaporation will increase the effect of interfering substances and therefore for concentrations below 0,1 mg/l the method in clause 4 is given. Clause 4 is applicable to the analysis of water and waste water when the concentration range is between 5mg/l and 100mg/l of chromium

26、by injecting a sample volume of 20ml. It is applicable to the determination of higher concentrations by using a smaller sample volume. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at

27、 the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of

28、the publication referred to applies. EN 25667-2 : 1993 Water quality Sampling Part 2: Guidance on sampling techniques (ISO 5667-2 : 1991) EN ISO 5667-3 : 1995 Water quality Sampling Part 3: Guidance on the preservation and handling of samples (ISO 5667-3 : 1994) 3 Determination of chromium by flame

29、atomic absorption spectrometry 3.1 Principle The method is based on the atomic absorption spectrometric measurement of the chromium content of the acidified sample in a nitrous oxide/acetylene flame. Measurement at a wavelength of 357,9 nm. Addition of lanthanum salt to reduce matrix interferences i

30、s necessary. 3.2 Reagents 3.2.1 General All reagents shall be of recognized analytical grade. Use deionized water or water distilled from an all glass apparatus. The water used for blank tests and for preparing reagents and standard solutions shall have a chromium content that is negligible compared

31、 with the smallest concentrations to be determined in the samples. 3.2.2 Hydrochloric acid, HCl, r 1,18 g/ml. 3.2.3 Nitric acid, HNO 3 , r 1,42 g/ml. 3.2.4 Nitric acid, c(HNO 3 ) = 1,5 mol/l. Introduce about 500 ml of water into a 1000 ml volumetric flask, add 100 ml of nitric acid (see 3.2.3) and d

32、ilute to the mark with water. 3.2.5 Hydrogen peroxide,H 2 O 2 ,30 % (m/m) solution. 3.2.6 Lanthanum chloride, (LaCl 3 ), solution with r(La) = 20 g/l. Dissolve 23,5 g of lanthanum oxide La 2 O 3 , in 200 ml of hydrochloric acid (see 3.2.2), dilute to 1000 ml with water and mix. Appropriate precautio

33、ns shall be observed when preparing this solution because the reaction of La 2 O 3 with hydrochloric acid is strongly exothermic. 3.2.7 Chromium solutions 3.2.7.1 Chromium, stock solution, with r(Cr) = 1,000 g/l. Dry a portion of potassium dichromate (K 2 Cr 2 O 7 ) at 105 C 2 C for about 2 h. Cool

34、and dissolve 2,825 g 0,001 g of the dried potassium dichromate in water. Add 5 ml 1 ml of nitric acid (see 3.2.3) and dilute to 1000 ml with water in a volumetric flask. 1 ml of this stock solution contains 1,00 mg of chromium. Store this solution in either polyethene or borosilicate glass container

35、s at room temperature. The solution is stable at room temperature for about 1 year if it is stored in the dark and at a pH between 1 and 2. NOTE. Chromium stock solutions are commercially available.Page 4 EN 1233 : 1996 BSI 1997 3.2.7.2 Chromium, standard solution with r(Cr) = 50 mg/l. Introduce 50,

36、00 ml 0,01 ml of the chromium stock solution (see 3.2.7.1) into a 1000 ml volumetric flask. Add 1 ml of nitric acid (see 3.2.3), make up to the mark with water and mix. This solution is stable for at least 1 month. 3.3 Apparatus 3.3.1 Atomic absorption spectrometer, equipped with a chromium hollow c

37、athode lamp and a nitrous oxide/acetylene burner, and operated in accordance with the manufacturers instructions. It is essential that the manufacturers safety recommendations are strictly observed when using the nitrous oxide/acetylene flame. 3.3.2 Glassware Before use, carefully soak all glassware

38、 for about 24 h in nitric acid (see 3.2.4), then rinse thoroughly with water. If low concentrations are expected (for example in ground water), the glassware should be kept under nitric acid (see 3.2.4) until use. Do not use glassware which has been cleaned with chromic acid. 3.3.3 Membrane filters,

39、 of nominal pore diameter 0,45mm, washed thoroughly with nitric acid (see 3.2.4) and rinsed with water (see 3.2.1). 3.4 Sampling and preparation of test portions 3.4.1 General Collect and preserve samples according to EN 25667-2 and EN ISO 5667-3. See also annex A. Collect samples in high density po

40、lyethene or borosilicate glass containers which have been previously cleaned with nitric acid (see 3.2.4) and then rinsed with water (see 3.2.1). 3.4.2 Acid soluble chromium Treat the samples by addition of sufficient nitric acid (see 3.2.3), immediately after collection, to adjust the pH to between

41、 1 and 2. To 90 ml of the acidified sample, or another suitable aliquot in accordance with the expected concentration, add 1 ml of hydrogen peroxide (see 3.2.5) and 2 ml of nitric acid (see 3.2.3). Boil and evaporate to a volume of approximately 50 ml. The sample shall not be reduced to dryness. In

42、the case of samples with low chromium concentrations this digestion method should be carried out in an autoclave or a microwave oven. It is important to follow the manufacturers instructions. Add 10 ml of nitric acid (see 3.2.3) to the evaporated solution. Transfer the solution to a 100 ml volumetri

43、c flask. Add 10 ml of lanthanum chloride solution (see 3.2.6) into the flask, dilute to the mark with water and mix. 3.4.3 Water soluble chromium Filter the sample through a membrane filter (see 3.3.3), as soon as possible after collection, and acidify the filtrate immediately with nitric acid (see

44、3.2.3)t o give a pH between 1 and 2. Add 10 ml of lanthanum chloride solution (see 3.2.6) to a 100 ml volumetric flask and make up to the mark with the acidified filtrate, or use another suitable aliquot in accordance with the expected concentration, and mix. 3.5 Procedure 3.5.1 Blank test Carry out

45、 a blank test in parallel with the determination by the same procedure and using the same quantities of all the reagents as in the sampling and determination, but replacing the test portion by water. 3.5.2 Preparation of the calibration solutions Before each set of determinations, prepare from the c

46、hromium standard solution (see 3.2.7.2) at least five calibration solutions covering the range of concentrations to be determined; for example: pipette 1,0 ml, 2,5 ml, 5,0 ml, 10,0 ml and 20,0 ml of chromium standard solution (see 3.2.7.2) into a series of 100 ml volumetric flasks. Add to each flask

47、 depending on the pretreatment (see 3.4.2 and 3.4.3) 10 ml or 2 ml of nitric acid (see 3.2.3) respectively and 10 ml of lanthanum chloride solution (see 3.2.6), dilute to the mark with water and mix. These solutions correspond to chromium concentrations of 0,50 mg/l, 1,25 mg/l, 2,50 mg/l, 5,00 mg/l

48、and 10,0 mg/l respectively. Proceed accordingly for other concentration ranges of interest. 3.5.3 Calibration Set up the instrument in accordance with the manufacturers instructions (at wavelength l = 357,9 nm) using a nitrous oxide/acetylene flame. Aspirate a calibration solution (see 3.5.2) and op

49、timize the aspiration, the burner height and the flame conditions. Adjust the response of the instrument to zero absorbance with water. In turn, aspirate the set of calibration solutions (see 3.5.2) and the blank solution (see 3.5.1). Plot a graph having the chromium concentrations of the calibration solutions in milligrams per litre as abscissa and the corresponding absorbance values as ordinate. Alternatively, data processing facilities can be used to equate the concentration against the absorbance. 3.5.4 Test