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1、BRITISH STANDARD BS 5666-7: 1991 Methods of analysis of Wood preservatives and treated timber Part 7: Quantitative analysis of preservatives containing bis(tri-n-butyltin)oxide: determination of total tin NOTEIt is essential that this Part is read in conjunction with Part 1 “Guide to sampling and pr
2、eparation of wood preservatives and treated timber”. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5666-7:1991 This British Standard, having been prepared under the direction of the Wood Preservation Standards Policy Committee, was publ
3、ished under the authority of the Board of BSI and comes into effect on 31 January 1991 BSI 11-1999 First published January 1980 Second edition January 1991 The following BSI references relate to the work on this standard: Committee reference WPC/11 Draft for comment 89/50549 DC ISBN 0 580 18591 5 Co
4、mmittees responsible for this British Standard The preparation of this British Standard was entrusted by the Wood Preservation Standards Policy Committee (WPC/-) to Technical Committee WPC/11, upon which the following bodies were represented: Association of Consulting Scientists British Drier Manufa
5、cturers Association British Wood Preserving and Damp-proofing Association Department of the Environment (Building Research Establishment) Ministry of Defence Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncon
6、trolled Copy, (c) BSI BS 5666-7:1991 BSI 11-1999i Contents Page Committees responsibleInside front cover Forewordii 0Introduction1 1Scope1 2Method 1. Atomic absorption spectrometric method1 3Method 2. Colorimetric method4 4Test report6 Publication(s) referred toInside back cover Licensed Copy: sheff
7、ieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5666-7:1991 ii BSI 11-1999 Foreword This Part of BS 5666 has been prepared under the direction of the Wood Preservation Standards Policy Committee. This Part of BS 5666 was first published in 1980. This edition
8、 introduces technical changes but it does not reflect a full review or revision of this Part of the standard, which will be undertaken in due course. BS 5666-7:1980 is withdrawn. CAUTION. Attention is drawn to the Health and Safety at Work etc. Act 1974, and the need for ensuring that the methods of
9、 test specified in this standard are carried out with suitable precautions. The procedures described in this standard method are intended to be carried out by qualified chemists or other suitably trained and/or supervised personnel. Normal safety precautions should be observed throughout the use of
10、the methods. Attention is drawn to the general safety precautions mentioned in clause 3 of BS 5666-1:1987. 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 St
11、andard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorp
12、orated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5666-7:1991 BSI 11-19991 0 Introduction Wood preservative solutions containing bis(tri-n-butyltin)oxide are u
13、sually formulated with technical grade material containing at least 95 % bis(tri-n-butyltin)oxide, e.g. material complying with the requirements of BS 4630. It is known that this compound can be degraded to give dibutyltin and monobutyltin compounds that will result in a decrease in fungistatic acti
14、vity. It may, therefore, be necessary to determine the organotins present, but in many cases the determination of the total tin content gives adequate information. A further Part of this standard will be published dealing with the determination of the different organotins. 1 Scope This Part of this
15、British Standard details procedures for the determination of the total tin content present in solutions and in treated wood containing bis(tri-n-butyltin)oxide. The methods have been found suitable for the determination of tin in the presence of the following: copper naphthenate; dieldrin (HEOD); -h
16、exachlorocyclohexane (-HCH, lindane); pentachlorophenyl laurate; pentachlorophenol and other chlorophenols; 2-phenylphenol; zinc naphthenate; water-repellent waxes and resins. It is assumed that all the tin determined by these methods has been derived from bis(tri-n-butyltin)oxide and hence the tin
17、contents are expressed in terms of bis(tri-n-butyltin)oxide. With aged samples of treated wood, it is occasionally difficult to acid extract all the tin, particularly if iron or some other cations are present. The method described in 2.4.4 has been shown to ensure that, in all cases, the proportion
18、of tin not extracted is unlikely to affect the validity of the determination. The wet ashing technique used in the colorimetric method (see clause 3) ensures that tin in all types of samples is brought into solution. The recommendations made as to the size of sample to be taken for the analysis of p
19、reservative solutions assume that the bis(tri-n-butyltin)oxide content is about 1 % by mass. For samples of other compositions, adjustments may have to be made in the quantity taken for analysis. It is difficult to make recommendations as to the mass of the wood sample to be analysed since the predo
20、minant factor is the quantity of preservative within the wood rather than the mass of the wood itself. It may be necessary to make some adjustment to the values quoted in the standard, either to the mass of the treated wood sample taken for analysis or to the level of dilution of the tin solution re
21、sulting from extraction. Furthermore, it should be noted that the range of concentrations suggested for the calibration solutions used in these methods may have to be adjusted to suit the sensitivity of the instruments being used. Two methods are described, the first involving atomic absorption spec
22、trometry and the second colorimetry. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Method 1. Atomic absorption spectrometric method 2.1 Principle The tin contents of suitably diluted preservative solutions or wood samples quantitatively extrac
23、ted with hydrochloric acid in ethanol are analysed using atomic absorption spectrometry. In this method, any variation in response due to the presence of other butyltin compounds is considered to be within the limits of experimental error of the procedure1) 2). It has been found with some atomic abs
24、orption spectrometers that the presence of easily ionized metals in the solution, e.g. the alkali metals, enhance the tin absorbance signal. Of these metals, lithium was found to have the greatest effect, and hence lithium is added to all test and calibration solutions. The presence of lithium also
25、minimizes differences in the responses of other organotins. 1) The responses of monobutyltin and dibutyltin compounds differ slightly from that of tributyltin compounds. With equivalent tin contents, dibutyltin compounds give an absorbance signal of 3 % to 5 % more than tributylin compounds. As the
26、dibutyltin contents of fresh solutions or recently treated wood are low, this difference is unlikely to be significant. 2) For reference, see “The determination of bis(tri-n-butyltin)oxide and di-n-butyltin oxide in preserved softwood by atomic absorption spectrometry and polarography” Williams, A.I
27、., Analyst, 1973, 98, 233. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5666-7:1991 2 BSI 11-1999 2.2 Reagents Reagents shall be of recognized analytical reagent grade. Ethanol (C2H5OH), 99 % (V/V) complying with BS 507 or 99 % (V/V) i
28、ndustrial methylated spirits complying with BS 3591 shall be used to make up the reagents where ethanol is specified. NOTEThe use of industrial methylated spirits is governed by the Methylated Spirits Regulations 1987 (SI 1987, No. 2009). It is not permissible to use duty-free ethanol received under
29、 the provisions of the Alcoholic Liquor Duties Act 1979, Section 10, for purposes for which industrial methylated spirit is an acceptable alternative to ethanol. 2.2.1 Hydrochloric acid solution A, c (HCl) about 21 g/L. Quantitatively transfer 25.0 mL of concentrated hydrochloric acid solution (20=
30、1.18 g/mL) into a 500 mL one-mark volumetric flask and make up to the mark with ethanol. 2.2.2 Hydrochloric acid solution B, c (HCl) about 2.1 g/L. Quantitatively transfer 100.0 mL of the hydrochloric acid solution A (2.2.1) into a 1 000 mL one-mark volumetric flask and make up to the mark with etha
31、nol. 2.2.3 Lithium chloride solution (1 mL = 5 000 g of lithium). Dissolve 15.30 g of anhydrous lithium chloride (LiCl) in 350 mL of ethanol. Transfer quantitatively to a 500 mL one-mark volumetric flask, add 50.0 mL of the hydrochloric acid solution A (2.2.1) and make up to the mark with ethanol. 2
32、.2.4 Standard bis(tri-n-butyltin)oxide solution. (1 mL = 200 g of bis(tri-n-butyltin)oxide) (C4H9)3Sn2O. Dissolve 0.1000 g of pure bis(tri-n-butyltin)oxide3) in 100 mL of ethanol. Transfer quantitatively to a 500 mL one-mark volumetric flask, add 50.0 mL of the hydrochloric acid solution A (2.2.1) a
33、nd make up to the mark with ethanol. CAUTION. Bis(tri-n-butyltin)oxide is toxic; it is essential that care is taken in handling it. 2.3 Apparatus 2.3.1 Volumetric glassware, complying with the requirements for class A quality in accordance with BS 700-2 (type 2), BS 846, BS 1583 or BS 1792, as appro
34、priate. 2.3.2 Atomic absorption spectrometer, together with a suitable source of the resonance radiation for tin, e.g. a hollow-cathode lamp. 2.4 Procedure 2.4.1 Instrument settings and operation The instrument settings and operating conditions for the determination of tin shall be as recommended by
35、 the manufacturer of the spectrometer. NOTE 1The solvent, ethanol, will contribute to the fuel in the flame and hence the acetylene flow given for aqueous solutions should be reduced. In order to minimize interference effects from neighbouring resonance lines of copper and zinc, the band pass accept
36、ed by the monochromator should be as small as possible, bearing in mind that the additional amplification required for low light levels could result in an unacceptable noise level. NOTE 2The tin absorbance signal is enhanced by the presence of easily ionized metals (e.g. the alkali metals) in the so
37、lution. Of these metals, lithium has been found to have the greatest effect and hence lithium chloride is added to all test and calibration solutions. The addition of lithium chloride however will necessitate frequent cleaning of the burner head either by scraping or by flushing through with water a
38、nd ethanol. The preferred fuel and oxidant are acetylene and nitrous oxide respectively, because interference effects are minimized and the sensitivity is improved. CAUTION. It is essential that the flow rates of the gases exceed the flame velocity, otherwise a flashback will occur with consequent e
39、xplosion. It is essential that the operator follow the instructions given for the instrument. 2.4.2 Preparation of calibration solutions Into a series of 100 mL one-mark volumetric flasks transfer 0, 1.0, 2.0, 3.0, 5.0, 10.0, 15.0, 20.0, 25.0 and 50.0 mL of the bis(tri-n-butyltin)oxide standard solu
40、tion (2.2.4), add 20.0 mL of the lithium chloride solution (2.2.3) and dilute to the mark with the hydrochloric acid solution B (2.2.2). This will provide solutions containing 0, 2, 4, 6, 10, 20, 30, 40, 50 and 100 g/mL respectively of bis(tri-n-butyltin)oxide. 2.4.3 Analysis of preservative solutio
41、ns Weigh out accurately 0.4000 g 4) of the preservative into a tared 100 mL one-mark volumetric flask. Add 20.0 mL of the lithium chloride solution (2.2.3) and dilute to the mark with the hydrochloric acid solution B (2.2.2). 3) Bis(tri-n-butyltin)oxide readily absorbs carbon dioxide from the atmosp
42、here; precautions should be taken to prevent this during storage. 4) See clause 1. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:54:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5666-7:1991 BSI 11-19993 Using the operating conditions suitable for the instrument being used, aspirate su
43、ccessively the hydrochloric acid solution B (2.2.2) to obtain the blank absorbance and a suitable range of calibration solutions, aspirating the hydrochloric acid solution B (2.2.2) between each calibration solution. Then aspirate the test solution(s) and check the calibration solutions after the la
44、st solution has been run. NOTEIf a number of samples are to be analysed, it may be advisable to check the instrument stability by bracketing each test solution with appropriate standard solutions. Plot a calibration graph of the concentration of bis(tri-n-butyltin)oxide in g/mL against absorbance. D
45、etermine the bis(tri-n-butyltin)oxide content of the sample solution by comparing the absorbance reading with the calibration graph and express the result in g/mL of bis(tri-n-butyltin)oxide in the test solution. 2.4.4 Analysis of treated wood 2.4.4.1 Preparation of timber sample for analysis Prepar
46、e the sample for analysis by converting the treated timber into a form suitable for extraction (i.e. shavings or sawdust) as described in clause 5 of BS 5666-1:1987. Divide the prepared sample into two portions each of about 0.5 g. Determine the moisture content on one portion according to the proce
47、dure described in clause 6 of BS 5666-1:1987. Reserve the other portion for analysis (2.4.4.2). 2.4.4.2 Extraction and preparation of test solution Weigh about 0.5 g of the prepared test sample (2.4.4.1) to the nearest 0.01 g into a suitable flask. Add 25.0 mL of the hydrochloric acid solution B (2.
48、2.2) and fit a reflux condenser to the flask. Reflux for 10 min and allow to cool. Filter the flask contents through a filter paper5) into a 50 mL one-mark volumetric flask, wash the contents of the flask into the paper with the hydrochloric acid solution B (2.2.2), wash the paper and contents with
49、this acid and dilute to the mark with these washings. Transfer 2.00 mL of the lithium chloride solution (2.2.3) into a 10 mL one-mark volumetric flask, make up to the mark with the extract solution and mix. 2.4.4.3 Measurement Using the operating conditions recommended for the instrument being used, aspirate successively the hydrochloric acid solution B (2.2.2) to obtain the blank absorbance and a suitable range of calibration solutions, aspirating the hydrochloric acid solution B (2.2.2) between each calibration solution. Then aspirate the test solution(s) and check t