1、BRITISH STANDARDBS EN ISO 16720:2007Soil quality Pretreatment of samples by freeze-drying for subsequent analysisICS 13.080.20g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60
2、g53g44g42g43g55g3g47g36g58BS EN ISO 16720:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2008 BSI 2008ISBN 978 0 580 62743 9National forewordThis British Standard is the UK implementation of EN ISO 16720:2007. It is identical wi
3、th ISO 16720:2005. The UK participation in its preparation was entrusted to Technical Committee EH/5, Sludge characterization.BSI, as a member of CEN, is obliged to publish EN ISO 16720 as a British Standard. However, attention is drawn to the fact that during the transposition of ISO 16720 (a soil
4、standard) into this European Standard, the UK committee voted against its approval as a European Standard because its performance has not been assessed for sludges. The effect of freeze-drying on the analysis of sludges was not considered, and the reproducibility of the results between laboratories
5、has not been subjected to the rigour of the Business Plan objective of CEN/TC 308.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its c
6、orrect application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 16720March 2007ICS 13.080.20English VersionSoil quality - Pretreatment of samples by fr
7、eeze-drying forsubsequent analysis (ISO 16720:2005)Qualit du sol - Prtraitement des chantillons parlyophilisation pour analyse subsquente (ISO 16720:2005)Bodenbeschaffenheit - Vorbehandlung von Proben durchGefriertrocknung fr die anschlieende Analyse (ISO16720:2005)This European Standard was approve
8、d by CEN on 25 February 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalsta
9、ndards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified t
10、o the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Neth
11、erlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in
12、 any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 16720:2007: EEN ISO 16720:2007 (E) Foreword The text of ISO 16720:2005 has been prepared by Technical Committee ISO/TC 190 “Soil quality” of the International Organization for Standardization (ISO) and has been tak
13、en over as EN ISO 16720:2007 by Technical Committee CEN/TC 308 “Characterization of sludges“, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2
14、007, and conflicting national standards shall be withdrawn at the latest by September 2007. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Repu
15、blic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of ISO 16720:2005 has been
16、approved by CEN as EN ISO 16720:2007 without any modifications. BS EN ISO 16720:2007ISO 16720:2005(E) iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is norm
17、ally carried out through ISO technical committees. Each member body interested 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 t
18、he work. ISO collaborates closely with the International Electrotechnical 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
19、 International Standards. Draft International Standards adopted by the technical 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
20、 of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 16720 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical methods and soil characteristics. BS EN ISO 1672
21、0:2007blank1Soil quality Pretreatment of samples by freeze-drying for subsequent analysis 1 Scope This International Standard specifies a method for pretreatment of soil samples by freeze-drying for subsequent analysis. This International Standard is applicable to soil samples for subsequent determi
22、nation of elements or organic compounds recognized as non-volatile under freeze-drying conditions. Generally, this International Standard can also be applied to samples from sludges and sediments. This method is also applicable as a first step for the determination of dry matter (or water) content,
23、for instance in the case of samples with high water content. 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 (
24、including any amendments) applies. ISO 11464, Soil quality Pretreatment of samples for physico-chemical analyses ISO 11465, Soil quality Determination of dry matter and water content on a mass basis Gravimetric method 3 Principle and general requirements Before freeze-drying, samples shall be cooled
25、 below their eutectic points. These are rarely known, but freezing the samples below 40 C is usually sufficient. During freeze-drying, water is removed from the sample under vacuum conditions by direct conversion from ice to vapour (sublimation) which is collected in a condenser where it releases it
26、s heat energy and turns again into ice. Generally a temperature below 50 C inside the condenser is suitable for usual applications. Sublimation requires heat in order to take place within an acceptable range of time. When the frozen sample containers are connected to an external inlet manifold (see
27、5.1.2), heat energy is supplied by the laboratory atmosphere. In case of a drying chamber equipped with temperature-controlled carriers (see 5.1.1), this energy is provided by heating the carriers. Vacuum conditions shall allow the generation of vapour pressure difference needed for sublimation and
28、the continuous evacuation of water vapour from the sample. Throughout the drying process, the pressure inside the apparatus and the temperature of the sample(s) shall be such as to avoid sample thawing and loss of any compound of interest. This last point may be difficult to achieve due to the large
29、 range of possible energy levels of the bonds between compounds of interest and the solid phase. For compounds known as non-volatile, a final temperature of the sample between 20 C to 25 C is suitable. Other final temperatures may be needed for compounds recognized as more volatile. In all cases, th
30、e final step shall be as short as possible. BS EN ISO 16720:2007ISO 16720:2005(E) 2 A sample in thin layer form is required for suitable freeze-drying. Whatever the kind of sample container, the thickness of the sample should not exceed 2 cm. If the representative amount exceeds a thickness of 2 cm,
31、 multiple drying may be applied. The quantity of sample treated depends on the representativeness, the dry matter content and the number of subsequent determinations. Sample containers for freeze-drying are selected accordingly. NOTE Soil samples often need to be dried before analysis. In the case o
32、f very humid or clayey soils, the technique of freeze-drying compared with air or oven drying at temperatures 40 C in accordance with ISO 11465 has the advantage of a quicker drying process and provision of a dried sample that can be reduced in size more easily. 4 Interferences Substances may volati
33、lize during freeze-drying and may partly be released to the ice condensate or be found in the gas released to the vacuum pump. If compounds lost due to valatilization are amongst those included in the list of parameters to be determined subsequently, analysis results are then directly affected. In c
34、ontrast, mass losses only affect the dry matter content and this effect is generally negligible. NOTE For example, ammonia nitrogen is lost during freeze-drying of sludges, the intensity of loss depending on the dry matter content. Therefore determination of ammonia nitrogen content should be avoide
35、d after freeze-drying, at least for liquid sludges, but in such a case the dry matter content is not significantly affected. In the final step of freeze-drying, samples become pulverulent and turbulences induced by the vacuum pump may carry away smaller solid particles. Samples can be protected by m
36、eans of a wire mesh. Achieving total dryness is difficult and may consume too much time, especially when several samples are treated at the same time. In these case, a level of dryness should be achieved which merely allows the samples to be handled, ground and homogenized, and residual water conten
37、t determined afterwards on a sub-sample. If not free, water may interact more or less strongly with the solid phase, leading to residual water contents depending on the selected drying method. For a standard determination of dry matter or water content, drying at 105 C in accordance with ISO 11465,
38、is required after freeze-drying. 5 Apparatus 5.1 Freeze-drying apparatus, composed of a drying device (5.1.1 or 5.1.2) connected to a condensing chamber (condenser), a vacuum system, a cooling system and the appropriate controls. 5.1.1 Thermally isolated drying chamber equipped with temperature cont
39、rolled carriers. The temperature of the samples, measured by inserted probes, is controlled by heating or cooling the carriers during freeze-drying. Generally, samples can be frozen on the carriers prior to freeze-drying. 5.1.2 External inlet manifold to which the frozen sample containers (generally
40、 flasks, but a few apparatus allow the use of trays instead of flasks) are connected. Heat energy is supplied by exchange with the laboratory atmosphere. 5.2 Suitable sample containers for freeze-drying, trays or flasks, forms and sizes are depending on the type of apparatus selected or available an
41、d on the quantities of sample treated. 5.3 Freezer for pre-cooling of samples, if possible with contact freezing facilities, minimum temperature 35 C, explosion-protected. Instructions of the manufacturer shall be followed. BS EN ISO 16720:2007ISO 16720:2005(E) 35.4 Pre-cooling equipment with a rota
42、ting system and a cooling bath containing ethanol at 40 C. Instructions of the manufacturer shall be followed. 5.5 Suitable storage containers for freeze-dried material, e.g. brown glass bottles. 6 Procedure 6.1 Pre-cooling of samples Transfer a representative amount of the sample into a suitable co
43、ntainer (5.2). The thickness of the layer in the plate should not exceed 2 cm. Multiple drying is allowed if the thickness of the representative amount exceeds 2 cm. NOTE Layers with thickness 2 cm accelerate the freezing and drying process. Transfer the container with the sample into the freezer (5
44、.3) or drying chamber (5.1.1), taking care to obtain a horizontal alignment. If necessary, stick a temperature probe into the sample (see 5.1.1). Follow the instructions of the manufacturer of the freeze-drying device. For apparatus operating with flasks (5.1.2), the thickness of the layer on the fl
45、ask wall shall be as thin as possible. Use of a rotating system (5.4) is recommended. If determination of dry matter content is required, weigh the empty container and record the mass (m1). Then weigh the container with the sample and record the mass (m2) (see 6.5). 6.2 Freeze-drying When using devi
46、ce 5.1.1, allow the drying chamber to cool (if not already achieved with pre-cooling). Pre-cool the condenser in accordance with instructions of the manufacturer. When using device 5.1.1, place the tray(s) with the frozen sample(s) on the carrier(s) of the drying chamber. If necessary connect the te
47、mperature probe(s). Close the chamber door tightly. Start the heating and temperature regulation of the carriers in accordance with the instructions of the manufacturer, so that the sample will not thaw. When using device 5.1.2, connect the flask(s) to the inlet manifold. Start the vacuum pump and w
48、ait until the vacuum is stable and the pressure is between 37 Pa and 63 Pa, so that the sample(s) will not thaw. NOTE A pressure of 37 Pa equals an ice temperature of approximately 30 C. A pressure of 63 Pa equals an ice temperature of approx. 25 C. 6.3 End of drying process The detection of the end
49、 of the drying process is crucial. The treatment of several different samples in a single batch increases the difficulty. The end of the process can be observed using the following parameters: specific instructions of the manufacturer; pressure rise is minimal, or no further change in pressure occurs; NOTE Compared to the empty system, the pressure does not increase when all the ice has been sublimed. final temperature of the condenser approaches its minimum value and remains constant (within 2 h, for example); temperature of the dried product
