1、BRITISH STANDARD BS7755-3.9: 1995 ISO11466: 1995 Soil quality Part 3: Chemical methods Section 3.9 Extraction of trace elements soluble in aqua regiaBS7755-3.9:1995 This British Standard, having been prepared under the directionof the Health and Environment Sector Board, waspublished under the autho
2、rityof the Standards Boardand comes into effect on 15 October1995 BSI 04-1999 The following BSI references relate to the work on this standard: Committee reference EH/4/3 Draft for comment92/59281DC ISBN 0 580 24695 7 Committees responsible for this British Standard The preparation of this British S
3、tandard was entrusted by Technical Committee EH/4, Soil quality, to Subcommittee EH/4/3, Chemical methods, upon which the following bodies were represented: Association of Consulting Scientists Association of Public Analysts British Ceramic Research Ltd. British Gas plc British Society of Soil Scien
4、ce Department of the Environment (Drinking Water Inspectorate) Department of Trade and Industry (Laboratory of the Government Chemist) National Rivers Authority Royal Society of Chemistry Society of Chemical Industry Soft Survey and Land Research Centre Water Research Centre Water Services Associati
5、on of England and Wales Amendments issued since publication Amd. No. Date CommentsBS7755-3.9:1995 BSI 04-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Preparation of laboratory sample
6、3 7 Procedure 3 8 Test report 3 Annex A (informative) Bibliography 5 Figure 1 Reaction vessel, reflux condenser and absorption vessel (assembled) 2 Figure 2 Example of an absorption vessel 4 List of references Inside back coverBS7755-3.9:1995 ii BSI 04-1999 National foreword This Section of BS7755 h
7、as been prepared by Subcommittee EH/4/3 and is identical with ISO11466:1995 Soil quality Extraction of trace elements soluble in aqua regia, published by the International Organization for Standardization (ISO). ISO11466 was prepared by Subcommittee3, Chemical methods, of Technical Committee ISO/TC1
8、90, Soil quality, with the active participation and approval of the UK. BS7755 is being published in a series of Parts subdivided into Sections and Subsections that will generally correspond to particular international standards. Other Parts of BS7755 are, or will be, as follows. Part 1: Terminology
9、 and classification; Part 2: Sampling; Part 3: Chemical methods; Part 4: Biological methods; Part 5: Physical methods. 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
10、a British Standard does not of itself confer immunity from legal obligations. Cross-references International standard Corresponding British Standard ISO3696:1987 BS3978:1987 Specification for water for laboratory use (Identical) BS7755 Soil quality ISO10694:1995 Section3.8:1995 Determination of orga
11、nic and total carbon after dry combustion (elementary analysis) (Identical) ISO11464:1994 Section3.5:1995 Pretreatment of samples for physico-chemical analyses (Identical) ISO11465:1993 Section3.1:1994 Determination of dry matter and water content on a mass basis by a gravimetric method (Identical)
12、Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside f
13、ront cover.ISO11466:1995(E) BSI 04-1999 1 WARNING Digestions with hydrochloric and nitric acid are potentially hazardous and safety glasses or goggles must be used. The digestion should be carried out in a well-ventilated fume cupboard with the reflux digestion on a temperature-controlled heating ap
14、paratus. It is essential to add antibumping granules (or roughened glass beads) both to the blank and the samples to prevent bumping and loss of solution. It is important to maintain gentle reflux, both of the blank and the test samples, to avoid temperature fluctuations which could cause local supe
15、rheating. 1 Scope This International Standard specifies a method for the extraction, with aqua regia, of trace elements from soils and similar materials, prepared according to ISO11464, and containing less than about20 % (m/m) organic carbon according to ISO10694. Materials containing more than abou
16、t20 % (m/m) organic carbon will require treatment with additional nitric acid (see note8). The resulting solution is suitable for the determination of trace elements using appropriate atomic spectrometric techniques. With high solute concentrations in extract solutions, spectral interferences and ba
17、ckground enhancement should be expected. NOTE 1Aqua regia will not totally dissolve most soils and similar materials, and the efficiency of extraction for particular elements differs from element to element. Such efficiency might also differ for the same element in different matrices. Users of this
18、International Standard should carry out a programme of analysis using reference materials to assure themselves that the method given here is appropriate for their needs. Elements extractable in aqua regia cannot, therefore, be decribed as “totals”; conversely they cannot be regarded as the “bio-avai
19、lable” fraction, as the extraction procedure is too vigorous to represent any biological process. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions in
20、dicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
21、International Standards. ISO3696:1987, Water for analytical laboratory use Specification and test methods. ISO10694:1995, Soil quality Determination of organic and total carbon after dry combustion (elementary analysis). ISO11464:1994, Soil quality Pretreatment of samples for physico-chemical analys
22、es. ISO11465:1993, Soil quality Determination of dry matter and water content on a mass basis Gravimetric method. 3 Principle The dried sample (see note2) is extracted with a hydrochloric/nitric acid mixture by standing for16h at room temperature, followed by boiling under reflux for2h. The extract
23、is then clarified and made up to volume with nitric acid. The trace metal content of the extract can be determined in accordance with 1 in Annex A. NOTE 2The soil should be prepared in accordance with ISO11464. It is common to grind 2mm soil to 1504m prior to aqua regia digestion. Such grinding is d
24、esigned to a) give a more homogeneous sample from which a subsample is taken; b) increase the efficiency of acid attack by increasing the surface area of the particles. For some soils, experience has shown that there is little difference between the results before and after such grinding (see2 in An
25、nex A). However, it is difficult to predict, with certainty, which soils will behave in this way. This is particularly important when considering soils containing relatively small amounts of potentially toxic elements, compared with materials which are geogenically enriched, or those considerably af
26、fected by anthropogenic activities. In both cases the amounts of such elements can be very large. The problem is exacerbated in materials with a wide range of particle size, especially if the element of interest is concentrated in one single size fraction, compared with soils of narrow particle size
27、 range. Users should also be aware that relatively little is known about the behaviour of these trace elements, under aqua regia extraction, in highly weathered soils such as oxisols and ultisols (see3 in Annex A). Therefore, the user should verify that the use of ground or unground soil yields resu
28、lts suitable for the purpose of the investigation. Whether ground or unground soil has been used shall be stated in the test report. 4 Reagents 4.1 General The reagents used shall meet the purity requirements of the subsequent analysis. Their purity shall be verified by performing a blank test. 4.2
29、Water The water used shall comply with grade2 of ISO3696, or better. NOTE 3Deionized water may be used, providing that it meets the requirements given above. It is recommended that the same batch of water is used throughout a given batch of determinations and that blank determinations are carried ou
30、t. 4.3 Hydrochloric acid, c(HCl) =12,0mol/l, 1,19g/ml. 4.4 Nitric acid, c(HNO 3 ) =15,8 mol/l, 1,42g/ml. 4.5 Nitric acid, c(HNO 3 ) =0,5mol/l. Dilute32ml of nitric acid(4.4) with water(4.2) to1litre.ISO11466:1995(E) 2 BSI 04-1999 5 Apparatus Clean all the glassware by carefully immersing in warm nit
31、ric acid(4.5) for a minimum of6h and then rinse with water(4.2). 5.1 Grinding mill, capable of grinding dried soils, sludges and sediments to a size less than1504m without contamination by the elements to be determined (see note2). NOTE 4A mill causing little or no contamination is essential, as is
32、adequate cleaning between samples to eliminate memory effects. Both agate and zirconium oxide mills have been found suitable. 5.2 Test sieve, of aperture size0,150mm, e.g.test sieve with gauze cloth preferably made from plastics materials, e.g.nylon. 5.3 Desiccator, of nominal volume2litres. 5.4 Rea
33、ction vessel, of nominal volume250ml (seeFigure 1). 5.5 Reflux condenser, straight-through type, with conical ground-glass joints (seeFigure 1). NOTE 5Water-cooled condensers with a minimum effective length of at least200mm have been found suitable. The effective length is the internal surface which
34、 is in contact with the cooling water. The overall external length of such condensers is usually at least365mm. 5.6 Absorption vessel, non-return type (e.g.as shown inFigure 2). NOTE 6The absorption vessel is only necessary when mercury is to be determined. Figure 1 Reaction vessel, reflux condenser
35、 and absorption vessel (assembled)ISO11466:1995(E) BSI 04-1999 3 5.7 Roughened glass beads, diameter2mm to3mm (or anti-bumping granules). 5.8 Temperature-controlled heating apparatus, capable of heating the contents of the reaction vessel to reflux temperature. 5.9 Funnel, of diameter approximately1
36、10cm. 5.10 Volumetric flask, of nominal capacity110ml. 5.11 Filter papers, cellulose-based ashless types, with a medium pore size of approximately84m and a diameter of150mm. 6 Preparation of laboratory sample Pretreat a representative portion of the air-dried sample according to ISO11464, or mill an
37、d sieve through the1504m sieve(5.2), if specified, to give a subsample of approximately20g. Use a portion of this subsample to determine the water content in accordance with ISO11465. 7 Procedure Weigh approximately3g, to the nearest0,001g, of the subsample into the250ml reaction vessel(5.4). Moiste
38、n with about0,5ml to1,0ml of water(4.2) and add, while mixing,21ml of hydrochloric acid(4.3) followed by7ml of nitric acid(4.4), drop by drop if necessary, to reduce foaming. Add15ml of nitric acid(4.5) to the absorption vessel(5.6). Connect the absorption vessel and condenser(5.5) to the reaction v
39、essel, and allow to stand for16h at room temperature to allow for slow oxidation of the organic matter in the soil. NOTE 7It is common practice to add the hydrochloric acid directly to the reaction vessel and sample, followed by the nitric acid, and to assume that the aqua regia forms in the reactio
40、n vessel. However, problems have been encountered with materials rich in carbonates, where a substantial proportion of the hydrochloric acid has been consumed before the nitric acid can be added. Under such circumstances, the correct formation of aquaregia is doubtful. NOTE 8The amount of aqua regia
41、 is sufficient only for oxidation of about0,5g of organic carbon. If there is any doubt about the amount of carbon present, carry out a determination according to ISO10694. If there is more than0,5g of organic carbon in the3g subsample, proceed as follows. Allow the first reaction with the aqua regi
42、a to subside. Then add an extra1ml of nitric acid(4.4) only to every0,1g of organic carbon above0,5g. Do not add more than10ml of nitric acid at any time, and allow any reaction to subside before proceeding further. Raise the temperature of the reaction mixture slowly until reflux conditions are rea
43、ched and maintain for2h, ensuring that the condensation zone is lower than 1/3 of the height of the condenser, then allow to cool. Add the contents of the absorption vessel to the reaction vessel, via the condenser, rinsing both the absorption vessel and condenser with a further10ml of nitric acid(4
44、.5). Allow the reaction vessel to stand so that most of any insoluble residue settles out of suspension. Decant the relatively sediment-free supernatant carefully onto a filter paper(5.11), collecting the filtrate in a100ml volumetric flask. Allow all the initial filtrate to pass through the filter
45、paper, then wash the insoluble residue onto the filter paper with a minimum of nitric acid(4.5). Collect this filtrate with the first. NOTE 9The amount of nitric acid(4.5) used depends on the quantity of residue, but more than10ml is rarely necessary. The extract thus prepared is ready for the deter
46、mination of trace elements, by an appropriate method, e.g.in accordance with1 in Annex A. NOTE 10The flask containing the extract could require the addition of releasing agents, depending on the element(s), of interest, and the spectroscopic method chosen. The flask should not, therefore, be filled
47、to the mark at this stage, until the further steps in the analysis have been decided upon. 8 Test report The test report can be prepared separately or in conjunction with the test report of the subsequent analytical method. The test report shall include the following information: a) a reference to t
48、his International Standard; b) a complete identification of the sample; c) a statement whether ground or unground soil has been used; d) any details not specified in this International Standard, or which are optional, as well as any other factor which may have affected the results.ISO11466:1995(E) 4
49、 BSI 04-1999 Figure 2 Example of an absorption vesselISO11466:1995(E) BSI 04-1999 5 Annex A (informative) Bibliography 1 ISO11047:, Soil quality Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc Flame and electrothermal atomic absorption spectrometric methods 1) . 2 HOUBA, J.V.G., CHARDON, W.J. and ROELSE, K. Influence of grinding of soil on apparent chemical composition(1993). Commun. Soil Sci. Plant Anal. 24 (13and14), pp.1591-1602. 3 Soil Survey Staff(1975), Soil taxonomy: a basi
