《ISO-9174-1998.pdf》由会员分享，可在线阅读，更多相关《ISO-9174-1998.pdf（16页珍藏版）》请在三一文库上搜索。
1、A Reference number ISO 9174:1998(E) INTERNATIONAL STANDARD ISO 9174 Second edition 1998-07-15 Water quality Determination of chromium Atomic absorption spectrometric methods Qualit de leau Dosage du chrome Mthodes par spectromtrie dabsorption atomique Copyright International Organization for Standar
2、dization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9174:1998(E) ISO 1998 All rights reserved. Unless otherwise specified, no part of this publ
3、ication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 CH-1211 Genve 20 Switzerland Internetisoiso.ch Printed i
4、n Switzerland ii ContentsPage 1Scope 1 2Normative references .1 3Determination of chromium by flame atomic absorption spectrometry1 4Determination of chromium by electrothermal atomization atomic absorption spectrometry 5 Annex A (informative) Pretreatment and digestion of sludge and sediment sample
5、s8 Annex B (informative) Precision data.9 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- ISOIS
6、O 9174:1998(E) iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a su
7、bject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission
8、(IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International S
9、tandards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. International Standard ISO 9174 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical, biochemical methods. This second edition cancels and replaces the first edi
10、tion (ISO 9174:1990), which has been technically revised. Annexes A and B of this International Standard are for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007
11、 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9174:1998(E) ISO iv Introduction Chromium occurs in water in the oxidation states III and VI. The two methods described in this International Standard determine chromium in both oxidation states, either as acid-s
12、oluble chromium or as water-soluble chromium, depending on the sample pretreatment. The method chosen depends on the concentration of chromium in the water to be examined. Annex A provides information on pretreatment and digestion of chromium from sludges and sediments. Copyright International Organ
13、ization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISOISO 9174:1998(E) 1 Water quality Determination of
14、chromium Atomic absorption spectrometric methods 1 Scope This International Standard specifies two methods for the determination of chromium in water by atomic absorption spectrometry. The two methods are covered in separate clauses as follows: Clause 3: Determination of chromium by flame atomic abs
15、orption spectrometry; Clause 4: Determination of chromium by electrothermal atomization atomic absorption spectrometry. Clause 3 is applicable to the analysis 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,
16、the determination can be carried out after carefully evaporating an acidified sample to small volume, taking care to avoid the formation of a precipitate. NOTE The use of evaporation will increase the effect of interfering substances and therefore for concentrations below 0,1 mg/l the method in clau
17、se 4 is given. Clause 4 is applicable to the analysis of water and waste water when the concentration range is between 5 mg/l and 100 mg/l of chromium by injecting a sample volume of 20 ml. It is applicable to the determination of higher concentrations by using a smaller sample volume. 2 Normative r
18、eferences The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on
19、 this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently
20、 valid International Standards. ISO 5667-2 : 1991, Water quality Sampling Part 2: Guidance on sampling techniques. ISO 5667-3 : 1994, Water quality Sampling Part 3: Guidance on the preservation and handling of samples. 3 Determination of chromium by flame atomic absorption spectrometry 3.1 Principle
21、 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 is necessary. 3.2 Reagents All reagents shall
22、 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 with the smallest concentrations to be determined in the
23、samples. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9174:1998(E) ISO 2 3.2.1 Hydrochlo
24、ric acid, HCl, r 1,18 g/ml. 3.2.2 Nitric acid, HNO3, r 1,42 g/ml. 3.2.3 Nitric acid, c(HNO3) = 1,5 mol/l. Introduce about 500 ml of water into a 1 000 ml volumetric flask, add 100 ml of nitric acid (see 3.2.2) and dilute to the mark with water. 3.2.4 Hydrogen peroxide, H2O2, 30 % mass fraction solut
25、ion. 3.2.5 Lanthanum chloride, (LaCl3), solution with r (La) = 20 g/l. Dissolve 23,5 g of lanthanum oxide La2O3 in 200 ml of hydrochloric acid (see 3.2.1), dilute to 1 000 ml with water and mix. WARNING: Observe appropriate precautions. The reaction of La2O3 with hydrochloric acid is strongly exo- t
26、hermic. 3.2.6 Chromium solutions. 3.2.6.1 Chromium, stock solution, with r(Cr) = 1,000 g/l. Dry a portion of potassium dichromate (K2Cr2O7) at 105 C 2 C for about 2 h. Cool and dissolve 2,825 g 0,001 g of the dried potassium dichromate in water. Add 5 ml 1 ml of nitric acid (see 3.2.2) and dilute to
27、 1 000 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 containers at room temperature. The solution is stable at room temperature for about year if it is stored in the dark and at a pH betwe
28、en 1 and 2. NOTE Chromium stock solutions are commercially available. 3.2.6.2 Chromium, standard solution, with r(Cr) = 50 mg/l. Introduce 50,00 ml 0,01 ml of the chromium stock solution (see 3.2.6.1) into a 1 000 ml volumetric flask. Add 1 ml of nitric acid (see 3.2.2), make up to the mark with wat
29、er 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 cathode lamp and a nitrous oxide/acetylene burner, and operated in accordance with the manufacturers instructions. It is essential that the manufacturers safe
30、ty recommendations are strictly observed when using the nitrous oxide/acetylene flame. 3.3.2 Glassware. Before use carefully soak all glassware for about 24 h in nitric acid (see 3.2.3), then rinse thoroughly with water. If low concentrations are expected (for example in ground water), the glassware
31、 should be kept under nitric acid (see 3.2.3) until use. Do not use glassware which has been cleaned with chromic acid. 3.3.3 Membrane filters, of nominal pore diameter 0,45 mm, washed thoroughly with nitric acid (see 3.2.3) and rinsed with water (see 3.2). Copyright International Organization for S
32、tandardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO ISO 9174:1998(E) 3 3.4 Sampling and preparation of test portions 3.4.1 General Collec
33、t and preserve samples in accordance with ISO 5667-2 and ISO 5667-3. See also annex A. Collect samples in high density polyethene or borosilicate glass containers which have been previously cleaned with nitric acid (see 3.2.3) and then rinsed with water (see 3.2). 3.4.2 Acid-soluble chromium Treat t
34、he samples by addition of sufficient nitric acid (see 3.2.2), immediately after collection, to adjust the pH to between 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 3.2.4) and 2 ml of nitric a
35、cid (see 3.2.2). Boil and evaporate to a volume of approximately 50 ml. The sample shall not be reduced to dryness. In 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 in
36、structions. Add 10 ml of nitric acid (see 3.2.2) to the evaporated solution. Transfer the solution to a 100 ml volumetric flask. Add 10 ml of lanthanum chloride solution (see 3.2.5) into the flask, dilute to the mark with water and mix. 3.4.3 Water-soluble chromium Filter the sample through a membra
37、ne filter (see 3.3.3), as soon as possible after collection, and acidify the filtrate immediately with nitric acid (see 3.2.2) to give a pH between 1 and 2. Add 10 ml of lanthanum chloride solution (see 3.2.5) to a 100 ml volumetric flask and make up to the mark with the acidified filtrate, or use a
38、nother suitable aliquot in accordance with the expected concentration, and mix. 3.5 Procedure 3.5.1 Blank test Carry out 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 tes
39、t portion by water. 3.5.2 Preparation of the calibration solutions Before each set of determinations, prepare from the chromium standard solution (see 3.2.6.2) 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
40、 ml and 20,0 ml of chromium standard solution (see 3.2.6.2) into a series of 100 ml volumetric flasks. Add to each flask depending on the pretreatment (see 3.4.2 and 3.4.3) 10 ml or 2 ml of nitric acid (see 3.2.2) respectively and 10 ml of lanthanum chloride solution (see 3.2.5), dilute to the mark
41、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 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 instruction
42、s (at wavelength l = 357,9 nm) using a nitrous oxide/acetylene flame. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:41:28 MDTNo reproduction or networking permitted without
43、license from IHS -,-,- ISO 9174:1998(E) ISO 4 Aspirate a calibration solution (see 3.5.2) and optimize 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 t
44、he 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 absorba
45、nce. 3.5.4 Test portion measurement Aspirate the prepared test portion (see 3.4.2 or 3.4.3) into the flame and measure the absorbance for chromium. After each measurement aspirate water and readjust the zero, if necessary. 3.6 Expression of results By reference to the calibration graph obtained (see
46、 3.5.3) or data-processing facilities used, determine the concentration of chromium corresponding to the absorbances of the test portion (see 3.5.4) and of the blank solution (see 3.5.1). Calculate the concentration of chromium of the sample using the equation: () r = AAV Vb ssow p where: ris the ch
47、romium concentration of the sample, in milligrams per litre; Asis the absorbance of the test portion; Asois the absorbance of the blank; Vpis the volume of the acidified sample in accordance with 3.4.2 or 3.4.3, in millilitres; bis the sensitivity (slope of the calibration graph), in litres per mill
48、igram; Vwis the volume of the test portion in accordance with 3.4.2 or 3.4.3, in millilitres. Precision data for this method are given in Table B.1. 3.7 Interferences The following ions have been tested and shown not to cause interference below the concentration given in Table 1. This information was taken from practical tests carried out in a working group in 1984. Table 1 Interfering ions IonConcentration mg/l IonConcentration mg/l Sulfate10 000Iron500 Chloride12 000Nickel100 Sodium9 000Copper1