DD-257-1-2003.pdf

DRAFT FOR DEVELOPMENT DD 257-1:2003 Methods of analysis of wood preservatives and treated timber Part 1: Quantitative analysis of wood preservative solutions and treated timber containing boron compounds Determination of total boron ICS 71.040.40; 71.100.50; 79.040 ? Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 This Draft for Development was published under the authority of the Standards Policy and Strategy Committee on 31 July 2003 © BSI 31 July 2003 The following BSI reference relates to the work on this Draft for Development: Committee reference B/515/2 ISBN 9 580 42014 0 Committees responsible for this Draft for Development The preparation of this Draft for Development was entrusted by Technical Committee B/515, Wood preservatives, to Subcommittee B/515/2, Specifications and chemical testing of wood preservatives, upon which the following bodies were represented: Association of Consulting Scientists British Wood Preserving and Damp-proofing Association Chemical Industries Association Creosote Council Department of Trade and Industry represented by the Building Research Establishment Timber Trade Federation Co-opted members Amendments issued since publication Amd. No. DateComments Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 © BSI 31 July 2003 i Contents Page Committees responsibleInside front cover Forewordii Introduction1 1Scope1 2Normative references1 3Terms and definitions2 4Method 1 Titrimetric method2 5Method 2 Colorimetric method5 6Test report10 Annex A (informative) Method of preparation of azomethine H11 Bibliography13 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 ii© BSI 31 July 2003 Foreword This part of DD 257 has been prepared by Subcommittee B/515/2, under the direction of Technical Committee B/515. DD 257 gives a variety of methods of analysis of wood preservatives and treated timber: DD 257-1 describes a titrimetric method and a colorimetric method for the determination of boron compounds as boric acid in preservative solutions (both aqueous solutions and solutions in hydrocarbon solvents) and in treated timber; DD 257-2 describes a polarographic method and a thin-layer chromatographic method for the determination of tributyltin, dibutyltin and monobutyltin compounds present in wood preservative solutions and in treated timber; DD 257-3 describes a high performance liquid chromatographic method and a gas chromatographic method for the separation and determination of the cis and trans isomers of permethrin in organic solvent-based solutions of wood preservatives; DD 257-4 describes a high performance liquid chromatographic method and a gas chromatographic method for the separation and determination of the cis and trans isomers of cypermethrin in organic solvent-based wood preservative solutions; DD 257-5 describes gas chromatographic methods for the qualitative identification of carboxylic acids in wood preservative solutions containing zinc and copper carboxylates. WARNING. This part of DD 257 calls for the use of substances and/or procedures that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. Attention is drawn to the Health and Safety at Work etc. Act 1974 1 and the Control of Substances Hazardous to Health Regulations 1994 (as amended) 2, and to the need for ensuring that the method of test specified in this standard is carried out with suitable precautions. See safety precautions mentioned in BS 5666-1:1987, Clause 3. It has been assumed in the preparation of this part of DD 257 that the execution of its provisions will be entrusted to appropriately qualified and experienced people, for whose use it has been produced. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature because there is at present insufficient experience in the use of the test method. It should be applied on this provisional basis, so that information and experience of its practical application can be obtained. In particular, information on precision (repeatability and reproducibility) is sought. A review of this Draft for Development will be carried out not later than 2 years after its publication. Notification of the start of the review period, with a request for the submission of comments from users of this Draft for Development, will be made in an announcement in the appropriate issue of Update Standards. According to the replies received, the responsible BSI Committee will judge whether the Draft for Development can be converted into a British Standard or what other action should be taken. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 © BSI 31 July 2003 iii Observations which it is felt should receive attention before the official call for comments will be welcomed. These should be sent to the Secretary of BSI Technical Committee B/515 at British Standards House, 389 Chiswick High Road, London, W4 4AL. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 13 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 © BSI 31 July 2003 1 Introduction This part of DD 257 describes two methods for the determination of boron compounds as boric acid in preservative solutions and in treated timber: a) titrimetric method; and b) colorimetric method. The titrimetric method is suitable for those concentrations of boron compounds, principally sodium borates, in aqueous solution used in the treatment of timber where the boron compounds are the principal preservative component. It is also suitable for the analysis of timber that has been treated with such solutions. Other wood preservative components are unlikely to be associated with these treatments but it is not known whether such components would interfere with the method if they were present. For the colorimetric procedure, two methods of sample preparation are given. The acid extraction procedure is suitable for preservative solutions and treated timber containing copper and chromium compounds in addition to boron compounds. This extraction procedure enables an analyst to determine the copper and chromium contents of the solution or treated timber according to BS 5666-3, as the extraction procedures are identical. If other components are present or the composition of the preservative solution or treatment of the timber is not known, the dry ashing procedure is preferred unless it can be shown that the other components do not interfere with the acid extraction procedure. In timber treated with very low loadings of boron compounds, where little or no dilution of the acid extract is required, it is necessary to consider the possibility of interference from wood extractives. In such cases the dry ashing procedure is recommended. It is customary in wood preservation to express the amounts of boron compounds as boric acid equivalents (see 3.1) and this convention is followed in this part of DD 257. The timber sample for analysis may be in the form of sawdust, wood flour or thin sections. 1 Scope This part of DD 257 describes two methods (titrimetric and colorimetric) for the determination of boron compounds as boric acid in preservative solutions and in treated timber. NOTEThe titrimetric procedure is not suitable for preservative solutions in which boron compounds are not the principal preservative component, nor is it suitable for preservative solutions in hydrocarbon solvents or for treated timber treated with these preservative solutions (see Introduction). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 245, Specification for mineral solvents (white spirit and related hydrocarbon solvents) for paints and other purposes. BS 572, Specification for interchangeable conical ground glass joints. BS 700-2:1982, Graduated pipettes Part 2: Specification for pipettes for which no waiting time is specified. BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 3145, Specification for laboratory pH meters. BS 5666-1:1987, Methods of analysis of wood preservatives and treated timber Part 1: Guide to sampling and preparation of wood preservatives and treated timber for analysis. BS 5666-3:1991, Methods of analysis of wood preservatives and treated timber Part 3: Quantitative analysis of preservatives and treated timber containing copper/chromium/arsenic formulations. BS EN ISO 1042, Laboratory glassware One-mark volumetric flasks. BS EN ISO 3696, Water for analytical laboratory use Specification and test methods. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 2© BSI 31 July 2003 3 Terms and definitions For the purposes of this part of DD 257, the following terms and definitions apply. 3.1 boric acid equivalent amount of boron present in solution, or in treated timber, expressed in terms of the equivalent amount of boric acid NOTEFor example, disodium octaborate tetrahydrate contains approximately 120 % boric acid equivalent. 4 Method 1 Titrimetric method 4.1 Principle Boron compounds are quantitatively extracted from treated timber with a known volume of hydrochloric acid solution by boiling under reflux. An aliquot of the resulting solution is adjusted potentiometrically to pH 6.30 with sodium hydroxide solution. Mannitol is then added, and the acidity produced by the reaction of boric acid with mannitol is determined by titration with sodium hydroxide solution back to pH 6.30. Aqueous preservative solutions are diluted with hydrochloric acid solution and the boric acid content is determined by titration as described above. 4.2 Reagents and materials 4.2.1 General Except where otherwise specified, all reagents shall be of recognized analytical grade and water conforming to BS EN ISO 3696:1995, grade 3 and free from carbon dioxide shall be used throughout. NOTEFreshly deionized water is suitable but, should there be doubt about the quality of water, a stream of nitrogen (4.2.2.1) should be passed through the water for 20 min to remove any carbon dioxide in solution: a volume of up to 10 l can be treated in this way. 4.2.2 Reagents 4.2.2.1 Nitrogen (N2), free from carbon dioxide (CO2). 4.2.2.2 Boric acid (H3BO3). Dissolve 60 g of boric acid in 200 ml of water by heating with stirring, until dissolved. Allow to cool to room temperature and filter off the boric acid crystals. Air dry at a temperature not exceeding 30 °C to constant mass and store in a tightly capped bottle. NOTEThis recrystallization procedure ensures stoichiometry as boric acid can lose combined water to form the metaboric acid (HBO2). 4.2.2.3 Hydrochloric acid, c(HCl) = 0.1 mol/l approximately. Dilute 10 ml of concentrated hydrochloric acid 425 g/l (20 = 1.18 g/ml), to 1 l with water. 4.2.2.4 Diethyl ether (C2H5)2O. 4.2.2.5 Sodium hydroxide solution, c(NaOH) = 0.5 mol/l approximately. Dissolve 10 g of sodium hydroxide in 500 ml of water. NOTEThis reagent does not need to be free from carbonate. 4.2.2.6 Mannitol CH2(OH).(CH.OH)4.CH2OH. Dissolve (10.0 ± 0.1) g of mannitol in 100 ml of carbon-dioxide-free water (see 4.2.1) and titrate with the 0.1 M sodium hydroxide solution (4.2.3.1) to a pH of (6.30 ± 0.01). If more than 0.05 ml of sodium hydroxide solution is required, subtract the titre of this blank titration from the titres obtained in the subsequent methods. NOTEIt is unusual for analytical reagent grade mannitol to require more than 0.05 ml of 0.01 M NaOH to give a pH of 6.30 under these conditions. If a larger volume is required the presence of carbon dioxide in the water can be indicated (see Note to 4.2.1). Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 05:35:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI DD 257-1:2003 © BSI 31 July 2003 3 4.2.3 Standard solution 4.2.3.1 0.1 M sodium hydroxide solution, c(NaOH) = 0.1 mol/l, free from carbonate. Standardize the sodium hydroxide solution against the recrystallized boric acid (4.2.2.2) as detailed below. NOTE 1The preparation of carbonate free sodium hydroxide solution is not straightforward and it is recommended that a commercial preparation be obtained. CAUTIONIt is essential that this solution is stored and used so that carbon dioxide is not absorbed. Accurately weigh, to the nearest 0.0002 g, approximately 0.1 g quantities of the boric acid (4.2.2.2) into 250 ml beakers and add 100 ml of the hydrochloric acid (4.2.2.3) to each beaker. Record the mass of the boric acid taken as m. Carry out at least three standardizations, with the results agreeing within 0.05 ml. For each solution, place the beaker on the magnetic stirrer (4.3.1), add a stirring bar, switch on the stirrer to mix the contents of the beaker and immerse the electrode(s) of the pH meter (4.3.2) in the solution. By means of a dropping pipette add approximately 1 ml of the diethyl ether (4.2.2.4) and, via a dip tube, pass a slow continuous stream of the nitrogen (4.2.2.1) through the solution throughout the titration. NOTE 2The passage of nitrogen in the presence of diethyl ether removes and maintains a carbon dioxide free solution. Any carbon dioxide present would otherwise be titratable leading to errors. Adjust the pH of the solution to within the range of 4 to 5 by addition of the 0.5 M sodium hydroxide solution (4.2.2.5). Carefully adjust the pH to (6.30 ± 0.01) by addition of the 0.1 M sodium hydroxide solution (4.2.3.1) from the burette (4.3.3) until the pH remains constant for at least 2 min. Record the buret