1、October 2010 Translation by DIN-Sprachendienst.English price group 14No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).IC
2、S 13.040.30!$kUX“1725053www.din.deDDIN ISO 15767Workplace atmospheres Controlling and characterizing uncertainty in weighing collectedaerosols (ISO 15767:2009)English translation of DIN ISO 15767:2010-10Arbeitsplatzatmosphre Kontrolle und Charakterisierung der Unsicherheit beim Wgen von gesammeltenA
3、erosolen (ISO 15767:2009)Englische bersetzung von DIN ISO 15767:2010-10Air des lieux de travail Contrle et caractrisation de lincertitude de pese des arosols collects(ISO 15767:2009)Traduction anglaise de DIN ISO 15767:2010-10SupersedesDIN ISO 15767:2004-02www.beuth.deDocument comprises pagesIn case
4、 of doubt, the German-language original shall be considered authoritative.2710.10 DIN ISO 15767:2010-10 A comma is used as the decimal marker. Contents Page National foreword .3 National Annex NA (informative) Bibliography.3 Introduction .41 Scope 5 2 Terms and definitions5 3 Weight instability Caus
5、es and minimization 7 3.1 General7 3.2 Moisture sorption.7 3.3 Electrostatic effects.8 3.4 Effects of volatile compounds (other than water) 8 3.5 Handling damage.8 3.6 Buoyancy changes 8 4 Correcting for weight instability by use of blanks .9 4.1 General9 4.2 Minimum number of blanks 9 4.3 Weighing
6、times and sequence .9 4.4 Conditioning times 9 4.5 Storage stability .9 5 Transport of collection substrates with collected aerosol samples to laboratory .10 5.1 General10 5.2 Recommended packaging 10 6 Weighing equipment and procedure .10 6.1 The balance 10 6.2 Recommended environmental controls 11
7、 6.3 Other equipment requirements 11 6.4 Procedure .11 7 Recommendations for the reporting of measured mass relative to LOD and LOQ12 8 Estimation of the uncertainty of the analytical procedure of weighing aerosol collection substrates.12 8.1 Introduction12 8.2 Within-laboratory estimated standard d
8、eviation swobtained over an extended period.13 9 Measures to assure the validity of previously determined measurement uncertainty.13 9.1 Continued determination of within-laboratory reproducibility .13 9.2 Participation in laboratory performance proficiency testing 13 9.3 Laboratory self-check on we
9、ighing uncertainty.13 Annex A (normative) Uncertainty component in weighing collected aerosol.14 Annex B (informative) Interpretation of LOD and LOQ18 Annex C (informative) Method evaluation example .20 Annex D (normative) Test of transportation integrity21 Annex E (informative) Check on weighing un
10、certainty .22 Annex F (informative) Balance uncertainty.23 Bibliography 25 2 DIN ISO 15767:2010-10 National foreword This standard has been prepared by Technical Committee ISO/TC 146 “Air quality” (Secretariat: DIN, Germany), Subcommittee SC 2 “Workplace atmospheres” (Secretariat: ANSI, USA). The re
11、sponsible German body involved in its preparation was the Normenausschuss Sicherheitstechnische Grundstze (Safety Design Principles Standards Committee), Working Committee NA 095-03-01-01 AK Staub. The text of ISO 15767:2009 has been adopted in its entirety. Attention is drawn to the possibility tha
12、t some of the elements of this document may be the subject of patent rights. DIN shall not be held responsible for identifying any or all such patent rights. The DIN Standard corresponding to the International Standard referred to in this document is as follows: ISO 7708 DIN ISO 7708 DIN EN 481, Wor
13、kplaces atmospheres Size fraction definitions for measurement of airborne particles may also be used as an alternative to the present standard. Amendments This standard differs from DIN ISO 15767:2004-02 as follows: a) the title of the standard has been changed and Clause 2 “Normative references” ha
14、s been deleted; b) in Clause 2 “Terms and definitions” of the German version, the original English terms have been added; c) Clause 8 “Estimation of the uncertainty of the analytical procedure of weighing aerosol collection substrates” has been added; d) Clause 9 “Measures to assure the validity of
15、previously determined measurement uncertainty” has been added; e) Annex A “Uncertainty component in weighing collected aerosol” has been revised; f) Annex E “Check on weighing uncertainty” and Annex F “Balance uncertainty” (both informative) have been added; g) the standard has been editorially revi
16、sed. Previous editions DIN ISO 15767: 2004-02 National Annex NA (informative) Bibliography DIN ISO 7708, Air quality Particle size fraction definitions for health-related sampling 3 Introduction Assessment of airborne aerosol hazards in occupational settings entails sampling onto a collection substr
17、ate, followed by analysis of the collected material. The weight of the collection substrate is generally many times (10 to 20, or more) larger than the aerosol sample. Weighing the aerosol sample is therefore actually the differential weighing of the substrate, where the aerosol sample is essentiall
18、y a disturbance of the substrate. The result is generally an estimated concentration of a hazardous material in the air. The uncertainty in such estimates depends on several factors, one of which relates to the specific type of analysis employed. This International Standard deals with a specific typ
19、e of analysis which finds the most general application in the sampling of aerosols, namely the weighing of sampled material. Gravimetric analysis, though apparently simple, is subject to uncertainty arising from instability in the mass of the sampling medium and other elements which must be weighed.
20、 An example is provided by aerosol samplers designed to collect particles so as to agree with the inhalable aerosol sampling convention. For some sampler types, the filter and cassette are weighed together to make estimates. Therefore, uncertainty may result if the cassette, for example, absorbs or
21、loses water between the weighings required for a concentration estimation. This International Standard describes such uncertainty and provides solutions for minimization. Workplace atmospheres Controlling and characterizing uncertainty in weighing collected aerosols 4 DIN ISO 15767:2010-10 1 Scope T
22、his International Standard provides recommendations for controlling the analytical uncertainty associated with aerosol collection medium instability, where collection medium or collection substrate includes any article used to collect particles (e.g. filter or foam material) as well as those support
23、ing elements which must be analysed by weighing. This International Standard is applicable to results compiled both from the literature and, if necessary and feasible, through laboratory experiment. Expected uncertainty associated with given aerosol capture methods is quantified where possible. Reco
24、mmendations as to materials to be used are given. Means of minimizing uncertainty arising from instability are provided. Recommendations for the weighing procedure are given. A procedure for estimating weighing uncertainty is described. Finally, recommendations are given for the reporting of measure
25、d mass, including an uncertainty component and limits of detection and quantification. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 aerosol sample aerosol particles collected onto the collection substrate or sampling cassette 2.2 collectio
26、n substrate aerosol sampling filter, foam, impaction plate or other deposition plate designed for subsequent analysis, with whatever mounting, e.g. a sampling cassette, if used, analysed (weighed) as a single item together with the collected aerosol sample, if present NOTE As an example of the conve
27、rse, the 25 mm or 37 mm plastic filter holder often used for “total dust” sampling in either its closed-face or open-face version is not part of the collection substrate in the definition above, since it is not weighed. 2.3 substrate holder cassette primarily designed to hold a collection substrate
28、(of any kind) and for which only the deposit on the collection substrate is analysed (weighed) 2.4 filter holder substrate holder designed to hold a filter and for which only the filter deposit is analysed (weighed) 2.5 sampling cassette collection substrate together with whatever mounting that is u
29、sed and analysed (weighed) as a single unit 5 DIN ISO 15767:2010-10 2.6 equilibration time time constant dependent on the type of collection substrate and characterizing an approximately exponentially damped approach of the mass of an aerosol collection medium to a constant value NOTE 1 The constant
30、 can be defined as the mean difference of the mass from equilibrium per mean rate of mass loss or gain, averaging over any time interval. NOTE 2 There may be important instances in which several independent time constants are required to describe the approach to equilibrium. NOTE 3 Equilibration tim
31、es range from seconds to weeks. 2.7 field blank blank collection substrate that undergoes the same handling as the collection substrate plus aerosol sample, including conditioning and loading into the samplers or transport containers, as well as transportation between the lab and sampling site, but
32、without being exposed to sampling 2.8 lab blank blank collection substrate that never leaves the laboratory, but undergoes the same handling as the collection substrate plus aerosol sample, including conditioning and loading into the samplers or transport containers 2.9 blank collection substrate co
33、llection medium or substrate taken from the same batch as the sampling medium, but unexposed to sampling 2.10 limit of detection LOD three times the estimated standard deviation of the mass of the aerosol sample, accounting for the double weighing (exposed vs. unexposed) and for the uncertainty asso
34、ciated with any correction blanks used NOTE The value of LOD, as defined here, does not take into account sources of variability beyond weighing. 2.11 false positive rate fraction of incorrect assertions of the presence of an aerosol sample on a substrate NOTE Annex B describes how to estimate, on t
35、he basis of the method evaluation, the false positive rate in such assertions. 2.12 limit of quantification LOQ ten times the estimated standard deviation of the mass of the aerosol sample NOTE The value of LOQ can be used as a threshold value to assure accurate measurement of a substance. For detai
36、ls, see Annex B. 2.13 uncertainty component uwestimated standard deviation of the mass of the aerosol sample NOTE See Annex A and ISO/IEC Guide 98-3 for details. 6 DIN ISO 15767:2010-10 3 Weight instability Causes and minimization 3.1 General Weight instability of collection substrates can be attrib
37、uted to several causes (see References 1 to 14). The following subclauses address the more important of these. 3.2 Moisture sorption 3.2.1 Moisture sorption is the most common cause of weight instability. Water can be directly collected by the filter or foam or other collection substrate material th
38、at is weighed. Water sorption by any part of the sampling system which is weighed must be suspected as well. For example, the sampling cassette itself, if weighed, can be the cause of significant uncertainty1. 3.2.2 The effects of water sorption can be reduced by using non-sorptive materials. Howeve
39、r, there may exist specific sampling needs for which a hydrophobic material is not feasible. Table 1 presents a list of common aerosol collection substrates with different water sorption features. Table 1 Water sorption characteristics of some aerosol sampling media Water sorption Collection substra
40、te or cassette type Very low Low High Very high Cellulose fibre filter * Glass fibre filter * Quartz fibre filter * Cellulose ester membrane filter * Polytetrafluoroethylene filter * PVC membrane filter * Polycarbonate filter * Silver membrane filter * Polyurethane foam * Greased Mylar impaction col
41、lection substrate * Greased aluminium foil impaction collection substrate * Carbon-filled resin * Aluminium cassette * Stainless steel cassette * NOTE 1 References 2 to 4 provide further details. Also, Reference 5 reports that filters of evidently the same material, but originating from different ma
42、nufacturers, can have widely differing variabilities. NOTE 2 There is generally a trade-off between hydrophobicity and conductivity in many materials 9. Therefore, one must be aware of the possibility of creating sampling problems when reducing hygroscopicity. NOTE 3 Pre-treatments of collection sub
43、strates, such as greasing, can also affect water sorption. 7 DIN ISO 15767:2010-10 3.3 Electrostatic effects Electrostatic effects are a common source of weighing problems. These effects can usually be minimized by discharging the collection substrate through the use of a plasma ion source or a radi
44、oactive source immediately before weighing or during weighing. Using conductive materials may reduce such problems. (See also Reference 7.) 3.4 Effects of volatile compounds (other than water) 3.4.1 Volatile compounds can be present in unused collection media3, or can be adsorbed onto media during s
45、ampling. 3.4.2 Desorption of volatiles from unused media can be controlled, for example, by heating or oxygen plasma treatment prior to conditioning and weighing. Alternatively, losses may be compensated by the use of blanks (see Clause 4). 3.4.3 When volatile materials collected during sampling con
46、stitute part of the intended aerosol sample, standardized written procedures are required to ensure that any losses are minimized or at least controlled, for example by conditioning under tightly specified conditions. 3.4.4 When volatile materials collected during sampling are not part of the intend
47、ed aerosol sample, it may be difficult to eliminate them if weighing is the only form of analysis. Non-sorptive media should preferably be used. 3.5 Handling damage 3.5.1 If friable collection substrates such as quartz filters are used, procedures are needed to control mechanical damage. 3.5.2 The a
48、ir-sampling equipment should be designed so that the collection substrate is not damaged during assembly and disassembly. 3.5.3 Flat-tipped forceps are recommended for handling filters. Non-oxidizing metal tins may be used to weigh delicate collection substrates without direct handling. 3.5.4 Parts
49、to be weighed shall not be touched with the hands, unless gloved. 3.5.5 Gloves, if used, shall leave no residue on what is weighed. 3.5.6 Handling shall take place in a clean environment, to avoid contamination. 3.6 Buoyancy changes Corrections for air buoyancy8, equal to the density of air multiplied by the air volume displaced, are not necessary for small objects, such as a 37 mm diameter membrane filter. However, there may exist circumstances (e.g. if an entire sampling cassette was weighed without the use of correcting blanks) i
