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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 6920 : Section 2.6 : 1
2、996 ICS 13.060.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water Part 2. Methods of test Section 2.6 The extraction of met
3、als Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI This British Standard, 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
4、 15 December 1996 BSI 1996 First published May 1988 Second edition June 1990 Third edition December 1996 The following BSI references relate to the work on this standard: Committee reference EH/3/7 Draft for comment 95/521401 DC ISBN 0 580 26291 X BS 6920 : Section 2.6 : 1996 Amendments issued since
5、 publication Amd. No.DateText 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/3/7, Effects of materials on water quality, upon which the following bodies were represented:
6、Association of Manufacturers of Domestic Electrical Appliances Automatic Vending Association of Britain British Adhesives and Sealants Association British Bathroom Council British Cement Association British Iron and Steel Producers Association British Malleable Tube Fittings Association British Non-
7、ferrous Metals Federation British Plastics Federation British Plumbing Fittings Manufacturers Association British Rubber Manufacturers Association Limited British Valve and Actuator Manufacturers Association British Water Cadmium Association Department of the Environment (Drinking Water Inspectorate
8、) Department of the Environment for Northern Ireland Department of Trade and Industry (Laboratory of the Government Chemist) Ductile Iron Producers Association Galvanizers Association Institute of Plumbing Lead Development Association Pipeline Industries Guild Pipeline Protection Association Scottis
9、h Association of Directors of Water and Sewerage Services UK Water Byelaws Scheme Water Research Centre Water Services Association of England and Wales Zinc Development Association Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6920 : Se
10、ction 2.6 : 1996 BSI 1996i Contents Page Committees responsibleInside front cover Forewordii Method Introduction1 1Scope1 2References1 3Principle1 4Reagents1 5Apparatus1 6Test samples1 7Test procedure2 8Determination of extracted metals2 9Expression of results3 10Test report3 List of referencesInsid
11、e back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 1996 BS 6920 : Section 2.6 : 1996 Foreword This Section of BS 6920 has been prepared by Subcommittee EH/3/7 under the direction of the Health and Environment Sector Board. T
12、his Section of BS 6920 supersedes BS 6920 : Section 2.6 : 1990, which is withdrawn. This edition introduces technical changes but it does not reflect a full review or revision of the standard, which will be undertaken in due course. Changes introduced include refinement, on the basis of experience,
13、of the reporting requirements, modification to the order of the extraction temperature and sequence to assist laboratories undertaking this test, and clarification of the test method validation data required. BS 6920 is published in several Parts, namely Part 1 Specification, Part 2 Methods of test
14、and Part 3 High temperature tests. Part 2 is further subdivided into a number of Sections and Subsections as follows: Section 2.1Samples for testing Section 2.2Taste of water Subsection 2.2.1General method of test Subsection 2.2.2Method of testing tastes imparted to water by hoses Subsection 2.2.3Me
15、thod of testing tastes imparted to water by hoses for conveying water for food and drink preparation Section 2.3Appearance of water Section 2.4Growth of aquatic micro-organisms Section 2.5The extraction of substances that may be of concern to public health Section 2.6The extraction of metals Complia
16、nce with a British Standard does not of itself confer immunity from legal obligations. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19961 BS 6920 : Section 2.6 : 1996 Method Introduction In the development of this test, much considera
17、tion was given to the composition of the water used to extract the metals. The composition and character of drinking water varies widely from region to region and there can be considerable changes according to season. No evidence was found to show that any particular water was more effective than di
18、stilled or deionized water in the leaching of metals from organic materials. It was therefore decided that distilled or deionized water was the most convenient for the wide range of products to be tested. 1 Scope This Section of BS 6920 specifies the test procedure for assessing the leachability of
19、metals from non-metallic products when used in contact with water intended for human consumption. NOTE 1. In view of the type of product tested and the amounts of additives present, a limiting level of solubility in the extract water (saturation) is unlikely to be attained. NOTE 2. The limit of dete
20、ction and sensitivity of the method vary according to the particular metal being analysed (see clause 8). 2 References 2.1 Normative references This Section of BS 6920 incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropri
21、ate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this Section of BS 6920 only when incorporated in the reference by amendment or rev
22、ision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Section of BS 6920 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this
23、standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Principle Samples of a product are immersed in water for a period of 24 h; this constitutes the first extract. The same samples are immersed in test water for a further six sequential extraction peri
24、ods, including one 72 h period and concluding with a 24 h period, using fresh test water for each period. Metals are determined on the final extracts. 4 Reagents 4.1 Test water, consisting of distilled or deionized water conforming to grade 3 of BS EN ISO 3696. 4.2 Nitric acid, concentrated (70 % by
25、 mass) analytical reagent grade, suitable for use in atomic absorption spectrophotometry. 4.3 Nitric acid, 10 % by volume, prepared by diluting 100 ml of the nitric acid (4.2) to 1 l with test water (4.1). CAUTION. Add the acid to the water carefully and with gentle stirring. 5 Apparatus 5.1 General
26、. Soak new glass and polyethylene ware for 2 days in nitric acid (4.3) and subsequently thoroughly rinse with test water (4.1). NOTE. Cleanliness is essential in the determination of trace metals. 5.2 Test containers, consisting of borosilicate glass beakers calibrated for a capacity in accordance w
27、ith 5.1.2 of BS 6920 : Section 2.1 : 1996 with borosilicate glass covers. The containers shall be of a size that will allow the test sample to be placed in the container in such a way as to minimize contact between the surface of the sample and the sides and bottom of the container. Before use, wash
28、 the beakers using a biodegradable laboratory detergent, rinse with the nitric acid solution (4.3) and finally with test water (4.1). 5.3 Bottles, made of polyethylene (or other suitable material known not to affect adversely the analytical results), and of a size to hold the extract prepared as des
29、cribed in either 7.2 or 7.4 as appropriate. For mercury analysis, polyethylene is an unsuitable material and bottles shall be made of glass or polyethylene terephthalate (PET) and shall contain, as a preservative, acidified potassium dichromate. NOTE. 0.05 % by mass potassium dichromate in 1 % by vo
30、lume nitric acid is suitable for preservation purposes. Prewash the bottles by the procedure described in 5.2. 6 Test samples 6.1 General requirements The samples shall conform to all the pertinent requirements given in BS 6920 : Section 2.1. 6.2 Sample cleaning On the same day as testing is to star
31、t, rinse the sample, contained in a suitably sized beaker, in flowing tap water for 30 min to remove loose particulate matter and dust. Finally rinse three times with fresh portions of the test water (4.1). Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled
32、Copy, (c) BSI 2 BSI 1996 BS 6920 : Section 2.6 : 1996 6.3 Number of tests Prepare duplicate samples (6.1) of each product being tested and carry out the extraction procedure given in clause 7 on each sample. If either sample exceeds the concentration limits specified in clause 8 of BS 6920 : Part 1
33、: 1996, repeat the extractions using a further three fresh samples. 7 Test procedure 7.1 First extraction Immediately after cleaning (see 6.2), place each sample in a separate clean container (5.2). Add to the container a measured volume of test water (4.1) sufficient to reach the calibration mark g
34、iven in 5.1.2 of BS 6920 : Section 2.1 : 1996 and record the volume of water added. If the density of the sample is less than that of water, ensure the sample is kept totally submerged in the test water for the duration of the test by using glass-encapsulated weights. Seal each container with the gl
35、ass cover. Store each container at a temperature of (232) C for (241) h. Remove the sample and transfer all but 50 ml of the extract into a sample bottle (5.3). To the remaining 50 ml of extract, add nitric acid (4.2) in the ratio of 5 ml of nitric acid to every 1000 ml of total extract. Rinse the c
36、ontainer with the acidified residual to remove any metals adsorbed onto the surface of the glass and finally add this rinse to the bulk of the extract in the sample bottle. Retain the acidified extract and determine the metals as described in clause 8. If the results from both of the extracts do not
37、 exceed the concentration limits specified in clause 8 of BS 6920 : Part 1 : 1996, then these first extracts are defined as the final extracts. In these circumstances, do not carry out further extractions. If this is not appropriate, then carry out the further extractions (7.2). 7.2 Repeat extractio
38、ns Wash the container carefully to remove all traces of nitric acid and then rinse it in test water (4.1). Replace the sample. Repeat the extraction procedure using the same volume of fresh test water in the same containers for a further six sequential periods, including one 72 h period and concludi
39、ng with a 24 h period, discarding extracts and acidified washings each time. 7.3 Final extract Remove the sample and transfer all but 50 ml of the extract into a sample bottle (5.3). To the remaining 50 ml of extract, add nitric acid (4.2) in the ratio of 5 ml of nitric acid to every 1 000 ml of tot
40、al extract. Rinse the container with the acidified residual to remove any metals adsorbed onto the surface of the glass and finally add this rinse to the bulk of the extract in the sample bottle. Retain the acidified final extract and determine the metals as described in clause 8. 7.4 Blank tests Ca
41、rry out a blank extraction procedure (reagent blank) following the procedure described in 7.1 and 7.3 but omitting the sample. A blank test is carried out to provide information on the effect of the container or possible ingress of contaminants from external sources. If any of the blank results are
42、greater than one tenth of the maximum admissible concentration (MAC) for the metals being determined, take steps to eliminate the source of contamination and repeat the whole test of the product. If a sample applied to a metal fitting is being tested, then test an identical cleaned metal fitting but
43、 without the product under test, as a metal fitting blank test. Carry out on this metal fitting all the procedures given in 7.1 to 7.3, and also carry out a reagent blank test. 8 Determination of extracted metals 8.1 Analytical methods Determine the metals listed in table 1 of BS 6920 : Part 1 : 199
44、6 in the final extracts (see 7.1 or 7.3 as appropriate). Choose the analytical method such that the total error of an analytical result does not exceed either 10 % of the relevant value given in the table or 20 % of the result, whichever is the greater. The requirements for the random and systematic
45、 errors are that they each shall not exceed one half of the tolerable total error as defined in this paragraph. NOTE 1. For an introduction to the concepts of random, systematic and total error in water analysis, the following publications may be consulted: a) HMSO. General Principles of Sampling an
46、d Accuracy of Results in the series Methods for the Examination of Waters and Associated Materials 1; b) Water Research Centre. A Manual on Analytical Quality Control for the Water Industry 2. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:30:47 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
47、BSI 19963 BS 6920 : Section 2.6 : 1996 For the determination of metals, where possible use a method given in BS 6068 : Part 2 that meets these criteria. For determinations of those metals not covered in BS 6068 : Part 2, use a method meeting these criteria from Methods for the Examination of Waters
48、and Associated Materials 3. NOTE 2. In determining the extracted metals content, dilutions of the extract may be made in order to bring the metal concentrations within the range of the particular analytical technique. Any dilution should be taken into account when calculating the original concentrat
49、ion of the metal in the extract. 8.2 Validation Control data are required from reagent blanks, duplicates and spikes to provide information on background contamination, and on analytical precision and accuracy of the methods used during analysis of each batch of extracts. The concentrations chosen for spikes shall be representative of the concentrations encountered in the test samples. 9 Expression of results Record the concentration of each metal determined in the final extracts (in mg/l), applying a correction factor for the volume of acid added to the final extrac
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