1、 Reference number ISO 20279:2005(E) ISO 2005INTERNATIONAL STANDARD ISO 20279 First edition 2005-07-01 Soil quality Extraction of thallium and determination by electrothermal atomic absorption spectrometry Qualit du sol Extraction du thallium et dosage par spectromtrie dabsorption atomique lectrother
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5、ess given below. ISO 2005 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs
6、 member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2005 All rights reservedISO 20279:2005(E) ISO 2005 All rights reserved iii Content
7、s Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Principle. 1 4 Reagents 2 5 Apparatus 3 6 Procedure 4 6.1 Test portion . 4 6.2 Blank test solution 4 6.3 Preparation of calibration solutions for thallium 4 6.4 Calibration and determination, electrothermal atomic absorption spectrometry (E
8、TAAS) 4 6.5 Direct measurement of calibration and test solutions, ETAAS . 5 7 Plotting the graph . 5 8 Calculation. 6 8.2 Calculation according to the method of standard additions 6 8.3 Expression of results . 6 9 Interferences . 6 10 Precision 7 11 Test report . 7 Bibliography . 8 ISO 20279:2005(E)
9、 iv ISO 2005 All rights reservedForeword 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 inter
10、ested in a subject 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
11、 Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the te
12、chnical 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. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IS
13、O shall not be held responsible for identifying any or all such patent rights. ISO 20279 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical methods and soil characteristics. INTERNATIONAL STANDARD ISO 20279:2005(E) ISO 2005 All rights reserved 1 Soil quality Ex
14、traction of thallium and determination by electrothermal atomic absorption spectrometry WARNING Thallium solutions are highly toxic. Appropriate measures shall be taken to avoid ingestion. Care should be taken in the disposal of these solutions. Certain procedures, reagents and apparatus used in thi
15、s International Standard pose potential hazards, especially in connection with concentrated acids, toxic solutions of thallium, and high- pressure gases. Users should ensure that they are familiar with the safety procedures necessary in such situations, and with any legal requirements (including was
16、te disposal). If in any doubt, seek advice from the competent authorities. 1 Scope This International Standard specifies methods for extraction of thallium from soil by nitric acid and hydrogen peroxide and its determination in the extract by electrothermal atomic absorption spectrometry (ETAAS). NO
17、TE The relevant working range of this method is approximately from 0,05 mg/kg to 100 mg/kg. 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 editi
18、on of the referenced document (including any amendments) applies. ISO 3696:1987, Water for analytical laboratory use Specification and test methods ISO 11464:1994, Soil quality Pretreatment of samples for physico-chemical analyses ISO 11465:1993, Soil quality Determination of dry matter and water co
19、ntent on a mass basis Gravimetric method ASTM E11:2004, Standard Specification for Wire Cloth and Sieves for Testing Purposes 3 Principle Thallium is extracted from soil by a mixture of nitric acid and hydrogen peroxide, and determined in solution by electrothermal atomic absorption spectrometry, in
20、 which discrete volumes of sample solution are dispensed into a graphite tube. By increasing the temperature of this tube step by step, the processes of drying, thermal decomposition of the matrix and thermal dissociation into free atoms occur. The resulting absorption signal should (under optimum c
21、onditions) be a sharp symmetrical peak with a height proportional to the element concentration in solution. See Table 1. Table 1 Measurement wavelength for thallium Element Wavelength nm Spectral bandwidth nm Measurement method Thallium 276,8 0,2 ETAAS ISO 20279:2005(E) 2 ISO 2005 All rights reserve
22、dNOTE Thallium contents in non-polluted soils are low. Therefore, a highly sensitive analytical method like ETAAS is necessary for the determination of trace concentrations. Unfortunately, severe interferences in aqua regia extracts of soils are observed using ETAAS for thallium determination. Due t
23、o a high chloride concentration in aqua regia extracts, thallium will be volatilised and lost during the pretreatment step. Therefore, in this International Standard, a mixture of nitric acid and hydrogen peroxide will be used for the extraction of thallium from soil. Aqua regia can be used with app
24、roximately the same extraction efficiency to extract thallium from soil. However, for the determination of the element in the extract solution, other analytical methods, like inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS),
25、shall be used. 4 Reagents All reagents shall be of recognised analytical grade. 4.1 Water, demineralised or distilled, from an all-glass apparatus, conforming to Grade 2 of ISO 3696. The water used for blank determinations, and for preparing reagents and standard solutions, shall have element concen
26、trations that are negligible compared with the lowest concentration to be determined in the sample solutions. 4.2 Nitric acid, w(HNO 3 ) = 65 %; 1,40 g/ml. The same batch of nitric acid shall be used throughout the procedure. 4.3 Nitric acid, c(HNO 3 ) = 0,5 mol/l. Add 32 ml of nitric acid (4.2) to
27、500 ml of water in a 1 000 ml volumetric flask, fill to the mark with water and mix well. 4.4 Hydrochloric acid, w(HCl) = 37 %; 1,185 g/ml. The same batch of hydrochloric acid shall be used throughout the procedure. 4.5 Hydrogen peroxide, w(H 2 O 2 ) = 30 %. The same batch of hydrogen peroxide solut
28、ion shall be used throughout the procedure. 4.6 Palladium/magnesium nitrate modifier solution. Dissolve 0,3 g of palladium nitrate Pd(NO 3 ) 2 and 0,36 g of magnesium nitrate Mg(NO 3 ) 2 6 H 2 O in a 100 ml volumetric flask, fill to the mark with 0,5 mol/l nitric acid (4.3) and mix. Alternatively, p
29、repare the palladium/magnesium nitrate modifier solution as follows. Dissolve 0,14 g of palladium powder in a 250 ml beaker with 3,5 ml of nitric acid (4.2), add 10 l of hydrochloric acid (4.4), evaporate the solution to near dryness on a water bath or hot-plate, then add 0,36 g of magnesium nitrate
30、 Mg(NO 3 ) 2 6 H 2 O. Dissolve this solid residue in 50 ml of nitric acid (4.3), transfer the solution into a 100 ml volumetric flask, fill to the mark with nitric acid (4.3) and mix. 10 l of this solution are equal to 14 g of Pd and 36 g of Mg(NO 3 ) 2 . 4.7 Preparation of stock and standard soluti
31、ons of individual elements. Two sources of stock solutions are available: commercially available stock solutions; stock solutions prepared in the laboratory from pure elements or stoichiometrically defined salts or oxides. ISO 20279:2005(E) ISO 2005 All rights reserved 3 NOTE Commercially available
32、stock solutions have the advantage that they remove the need to handle toxic metals, especially thallium, directly. However, special care needs to be taken to ensure that these solutions are supplied with a certified composition from a reputable source and are checked on a regular basis. 4.8 Thalliu
33、m stock solution, corresponding to (Tl) = 1 000 mg/l. 4.9 Thallium standard solution, corresponding to (Tl) = 100 mg/l. Pipette 50,00 ml of the thallium stock solution (4.8) into a 500 ml volumetric flask, add 5 ml of nitric acid (4.2), fill to the mark with water and mix well. 4.10 Thallium standar
34、d solution, corresponding to (Tl) = 1 mg/l. Pipette 1,00 ml of the thallium standard solution (4.9) into a 100 ml volumetric flask, add 2 ml of nitric acid (4.2), fill to the mark with water and mix well. Prepare this solution on the day of use. 4.11 Blank calibration solution. Dilute 5 ml of nitric
35、 acid (4.2) in a 100 ml volumetric flask and fill to the mark with water. Cleaning of glassware: All glassware used in the determination of small amounts of this element shall be cleaned carefully before use, e.g. by immersion in aqueous nitric acid solution, w(HNO 3 ) = 5 %, for a minimum of 6 h, f
36、ollowed by rinsing with water before use. The nitric acid shall be replaced each week. It can be helpful to keep a separate set of glassware exclusively for these determinations. 5 Apparatus Usual laboratory apparatus and the following. 5.1 Grinding device, capable of grinding dried soils to 150 m p
37、article size without element contamination. 5.2 Test sieve, in accordance with ASTM E11, with an aperture of 150 m (100 mesh). 5.3 Drying oven and desiccator, for the determination of dry matter in accordance with ISO 11465. 5.4 Nitric acid/hydrogen peroxide extraction device. Temperature-controlled
38、 heating apparatus, and a 250 ml round-bottomed flask with reflux condenser, straight- through type, and a non-return-type absorption vessel filled with 10 ml of nitric acid (4.3), capable of heating the nitric acid/hydrogen peroxide mixture to reflux temperature. The use of an absorption vessel is
39、recommended, due to vigorous reaction of reagents with samples having a high organic-matter content. Alternatively, a pressure digestion system (up to 50 bar) with sample vessels made of PTFE-TFM, PFA, quartz or another suitable material, and thermal heating equipment or a microwave oven may be used
40、. 5.5 Filter papers, cellulose-based ashless types for quantitative work, with a medium open texture and with a diameter of approximately 100 mm to 150 mm. Alternatively, use a membrane filtration equipment with cellulose-based membrane filters of approximately 8 m pore size. 5.6 Atomic absorption s
41、pectrometer, equipped with an electrothermal atomiser, an automated sample introduction system, a thallium hollow cathode lamp or electrodeless discharge lamp operated at a current recommended by the lamp and instrument manufacturer, an automatic background correction device (preferably Zeeman backg
42、round correction) and a computerised readout. ISO 20279:2005(E) 4 ISO 2005 All rights reserved6 Procedure 6.1 Test portion 6.1.1 General Grind a representative portion of air-dried sample (prepared in accordance with ISO 11464) until it passes entirely through the 150 m aperture sieve (5.2), so as t
43、o obtain a subsample of approximately 20 g. Use a separate portion of the subsample to determine the water content in accordance with ISO 11465. 6.1.2 Nitric acid/hydrogen peroxide extraction for thallium Reflux technique Weigh (1,000 0,001) g of this ground subsample into a round-bottomed flask, an
44、d add 5 ml of nitric acid (4.2). Add 10 ml of nitric acid (4.3) to the absorption vessel. Connect the cooling system with the trap, and allow to react for 16 h at room temperature. Then add 10 ml of hydrogen peroxide (4.5) to the round-bottomed flask. Raise the temperature slowly to reflux condition
45、s and maintain for 4 h, 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 the condenser with a further 10 ml of nitric a
46、cid (4.3). Allow the reaction vessel to stand so that most of any insoluble residue settles out of suspension. Decant the sediment-free supernatant carefully onto a filter paper (5.5), and collect the filtrate in a 100 ml volumetric flask. Wash the residue carefully with a minimum of nitric acid (4.
47、3) and add the washings to the volumetric flask. Fill to the mark with water and mix well. 6.1.3 Nitric acid/hydrogen peroxide extraction for thallium Pressurized digestion technique Weigh (0,500 0,001) g of this ground subsample into the pressure vessel (5.4). Add 5 ml of nitric acid (4.2) and 2,5
48、ml of hydrogen peroxide (4.5), wait until any vigorous gaseous emission ends and then close the vessel. Raise the temperature to 160 C and hold for 3 h. Cool the digestion vessel to room temperature, rinse with nitric acid (4.3) and filter the suspension through a paper filter or membrane filter (5.
49、5) into a 50 ml volumetric flask. Wash the residue carefully with a minimum of nitric acid (4.3) and add the washings to the volumetric flask. Fill to the mark with water and mix well. 6.2 Blank test solution Carry out a blank test at the same time as the determination and following the same procedure, using the same quantities of all the reagents for the determination, but omitting the test portion. 6.3 Preparation of calibration solutions for thallium The standard solutions shall be pre
