1、Designation: E 544 99 (Reapproved 2004)Standard Practices forReferencing Suprathreshold Odor Intensity1This standard is issued under the fixed designation E 544; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These practices are designed to outline a preferredmeans for referencing the odor intensities of a material in thesuprathresho
3、ld region.1.2 The general objective is to reference the odor intensityrather than other odor properties of a sample.1.3 These practices are designed to reference the odorintensity on the ASTM Odor Intensity Referencing Scale ofany odorous material. This is done by a comparison of the odorintensity o
4、f the sample to the odor intensities of a series ofconcentrations of the reference odorant, which is 1-butanol(n-butanol).1.4 The method by which the reference odorant vapors areto be presented for evaluation by the panelists is specified. Themanner by which the test sample is presented will depend
5、onthe nature of the sample, and is not defined herein.1.5 Test sample presentation should be consistent with goodstandard practice (1)2and should be explicitly documented inthe test report.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
6、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See Annex A1 forspecific safety data.2. Referenced Documents2.1 ASTM Standards:3D 1292 Test Method for Odor in Water3. Termin
7、ology3.1 ASTM odor intensity referencing scaleseries of1-butanol dilutions used to establish which concentrationexhibits an odor intensity matching that of the sample.3.2 concentrationseries of concentrations of 1-butanol inodorless air, nitrogen, or the water diluent, made to specificreference dilu
8、tions which serve as the reference scale, volumebasis, of 1-butanol diluted air or in water. In the latter case, thetemperature of the solution during the test should be reported.3.3 dynamic scalereference scale in which vapor dilutionsare prepared by continuous mixing of vapors of 1-butanol withan
9、odorless gas, such as air, to yield constant dilutions of vaporin the gas.3.4 panelistsindividuals who compare the odor intensityof the sample to the reference scale. These individuals shouldbe able to do this with a consistency described in 5.5.3.5 perceived (sensory) odor intensityintensity of an
10、odorsensation which is independent of the knowledge of theodorant concentration.3.6 samplematerial in any form exhibiting an odor thatneeds to be measured.3.7 static scalereference scale in which dilutions of1-butanol in water are prepared in flasks and presented for odorintensity comparison from th
11、e flasks.3.8 suprathreshold odor intensityperceived (sensory) in-tensity of the odor in that intensity region in which the odor isclearly experienced.4. Summary of Practice4.1 The reference odorant used to generate an odor intensityscale is 1-butanol (n-butanol). The reasons for its selection aresum
12、marized in Appendix X1. A geometric progression scalewith a ratio of 2 is recommended, that is, a scale in which eachreference dilution differs in its 1-butanol concentration fromthe preceding dilution by a factor of 2.4.2 Two procedures, A and B, are described in theserecommended practices. They di
13、ffer in the method by whichthe diluted 1-butanol vapors are prepared.NOTE 1The relationships between the odor intensity of 1-butanolconcentrations in air and in water have not been evaluated. Translation ofProcedure B data to the numerical values of Procedure A is not possibleat this time.4.2.1 In P
14、rocedure A, hereafter referred to as the dynamicscale method, a dynamic-dilution apparatus is used. This isequipped with a series of sniffing ports from which constantconcentrations of 1-butanol emerge at constant volumetric flowrates in air.1These practices are under the jurisdiction ofASTM Committ
15、ee E18 on SensoryEvaluation of Materials and Products and are the direct responsibility of Subcom-mittee E18.04 on Fundamentals of Sensory.Current edition approved Dec. 1, 2004. Published December 2004. Originallyapproved in 1975. Last previous edition approved in 1999 as E 544 99.2The boldface numb
16、ers in parentheses refer to the list of references at the end ofthese recommended practices.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document S
17、ummary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2.2 In Procedure B, hereafter referred to as the static-scalemethod, a series of Erlenmeyer flasks containing knownconcentrations of 1-butanol in water
18、is used.4.3 The odor of the sample is matched, ignoring differencesin odor quality, against the odor intensity reference scale of1-butanol by a panel yielding at least eight independentjudgments. Panelists report that point in the reference scalewhich, in their opinion, matches the odor intensity of
19、 theunknown.4.4 The independent judgments of the panelists are aver-aged geometrically (see 7.4) with respect to the 1-butanolconcentrations of the indicated matching points. Results arereported as an odor intensity, in parts per million, of 1-butanolin air (ProcedureA) or water (Procedure B) on the
20、ASTM OdorIntensity Referencing Scale. When water is used as a diluent,the temperature of the reference scale solutions during the testmust be reported.4.5 The odor intensity equivalent values which are obtainedmay then be used to compare the relative intensities of samplegroups. These values are ref
21、erence values and are not related tothe odor intensities by a simple proportionality coefficient (see8.2).5. Procedure ADynamic-Scale Method5.1 Reagents:5.1.1 1-butanol (n-butanol), the reference odorant, withrequired purity 99+ mol % by gas chromatography. Also shallbe free of strong odorous impuri
22、ties.5.1.2 DiluentNonodorous room or cylinder air.5.2 Preparation of Dynamic Scale:5.2.1 Prepare the 1-butanol airflow mixtures in an olfacto-meter apparatus as follows: Pass air over an expanded surfaceof 1-butanol in order to produce a saturated vapor at a knownambient temperature. Temperatures sh
23、ould be ambient in orderto avoid condensation in the airflow lines. Air becomessaturated (98+ %) at flow rates up to 60 mL/min when passedover a surface of 1-butanol that is 120 mm long by 10 mm widein a 13-mm inside diameter glass tube which is held in ahorizontal position. Saturated vapor prepared
24、 by bubbling airthrough 1-butanol is less desirable since the bubbles burst atthe surface and produce droplets. In such methods of vaporgeneration, glass wool filter, operating at the same temperatureas the 1-butanol liquid sample, must be used to remove thedroplets. Obtain concentrations of vapor b
25、elow saturation bydiluting the saturated vapor with additional volumes of air.5.2.2 If air, such as pumped ambient air which containswater vapor is used, replace the 1-butanol in the saturation tubeevery 2 to 3 h; otherwise it will become diluted by theabsorption of water which will lower the vapor
26、pressure of1-butanol, and will result in a lower odorant concentration atthe sniffing ports.5.2.3 An adequate concentration range for most applicationsis between 5 and 2000 ppm of 1-butanol in air. Above 2000ppm, the odor intensity is too strong for accurate judgment.Below 5 ppm, the odor is too clo
27、se to the threshold limit forpanelists to make accurate judgments.5.2.4 The temperature of 1-butanol in the saturation tubeshould be noted at the start and kept constant during the test. Itshould be within the range of comfortable room temperatures.5.2.5 The rate of dynamic delivery of air carrying
28、diluted1-butanol vapor from sniffing ports should be 160 6 20mL/min from a port with a cross-section of 400 to 500 mm2,resulting in a nominal linear flow rate of 300 mm/min. A ratethat is too slow allows the stimulus to be diluted withincreasing amounts of room air. A rate that is too fast creates a
29、mechanical sensation in the nose which complicates the odorintensity judgment.5.2.6 An example of a dynamic dilution apparatus, called adynamic olfactometer, is diagrammed in Fig. X1.1 and itsoperation is explained, in Appendix X4.5.3 Reference Concentrations:5.3.1 This practice is intended to estab
30、lish, on a continuousppm 1-butanol scale, that ppm value which best corresponds inits odor intensity to the odor intensity of the sample. Since sucha scale is technically difficult, the one designed consists of aseries of discrete concentration points at sniffing ports continu-ously delivering known
31、 concentrations of 1-butanol vapor inair.5.3.2 A geometric progression scale of concentrations isused, in which each reference port differs in its 1-butanolconcentration from the preceding port by a factor of 2. It wouldhave been desirable to select and always use the same ppmvalues for the same por
32、ts, however, this would require verycomplex flow adjustment systems. Although the ppm valuesdelivered by the scale ports change with temperature, theyremain in the same ratio to each other, and thus still permit theintensity equivalence point to be easily found.5.3.3 The scale points are arranged sy
33、stematically, in theorder of increasing concentrations, and are numbered inascending integers, from 1 for the lowest concentration of1-butanol.5.3.4 The matching points normally used are the scalepoints, or positions between the scale points, but can also bethose points beyond either end of the scal
34、e.5.4 Test RoomThe test room must be well-ventilated,essentially odor-free, and comfortable. In order to avoid bias,waiting panelists should not observe or learn the judgments ofthe panelist currently matching the odor intensity of the sampleto the scale (1, 2).5.5 Odor Panel:5.5.1 NumberThe number
35、of panelists should be eight ormore, to permit elementary statistical tests on their judgments.A smaller number of panelists may be used with replicatejudgments to increase the total to eight or more. It is importantwhen obtaining replicate data that all bias is removed. Precau-tions such as separat
36、e sessions and recoding are recommended(1).5.5.2 SelectionSpecial training is not needed but precau-tions must be taken in the selection of the panelists (3). Anindividual with insufficient sensitivity to detect the odor of 10ppm of 1-butanol in air should not be a panelist. Also, someindividuals ha
37、ve been observed to experience difficulty inmatching odor intensities. Prospective panelists can bescreened by having them repeatedly match the odor intensity ofa known concentration of 1-butanol vapor to the 1-butanolreference scale. Those whose standard deviation in repeatedE 544 99 (2004)2testing
38、 exceeds 1.5 scale steps should not be used in the panel.Periodic retesting of panelists may be advisable.5.6 Judgment Procedure:5.6.1 Panelists are instructed on the nature of the 1-butanolodor intensity reference scale. They are told that the ports arenumbered beginning with No. 1, which represent
39、s the weakestodor and that the odors increase systematically in intensity withincreasing port identification numbers.5.6.2 Panelists are instructed to smell the unknown sampleand then to smell the scale, beginning with its weakest end, andmatch the unknown to the scale, ignoring differences in theod
40、or quality. They are permitted to check and recheck theunknown against the scale any number of times and should notbe hurried or biased by others in any manner.5.6.3 Panelists are advised that they may report one of thescale points as the best match, or else may report that the bestmatch occurs betw
41、een two adjacent points, for example, theunknown is stronger than scale point No. 7, but weaker thanscale point No. 8.5.6.4 Panelists should be advised that the odor may also beweaker than the weakest point of the scale, or stronger than thestrongest point of the scale.5.6.5 When his judgment is wit
42、hin scale limits, the panelistshould make sure that the selected position is a good match,that is, that the next lower concentration of 1-butanol indeedsmells weaker than the unknown, and that the next higherconcentration indeed smells stronger.5.6.6 Panelists report the matching point in terms of t
43、he portidentification number. When the best match is a positionbetween the scale points, such as between port Nos. 7 and 8,the half-number, 7.5, is used.5.6.7 During repeated smelling of one or more samples orscale points, olfactory adaptation (fatigue) occurs, renderingthe sense of smell less sensi
44、tive. However, the relative positionof the unknown with respect to the scale is not undulyinfluenced unless the rates of adaptation to 1-butanol and to thesample are very different. The adaptation rate to 1-butanol hasbeen reported to be average when compared to other odorants(4). Therefore, the com
45、plication that may result from differ-ences in the adaptation rate to the unknown and to 1-butanol isminimized by selecting 1-butanol as the reference odorant.5.6.8 Because of the olfactory adaptation discussed in 5.6.7,a panelist may find that after judging at higher odor intensitypoints on the sca
46、le, he may have difficulty in detecting odor atthe lowest points of the scale. A rest of 2 to 5 min will usuallycorrect this effect.5.6.9 Panelists may differ in the amount of time required torender a judgment. The panelist should be allowed to proceedat a rate comfortable to him.As many as six test
47、 stimuli can behandled by a panel of nine in a 1-h session.6. Procedure BStatic-Scale Method6.1 The reference odorant is 1-butanol, (see 5.1.1). Thediluent is distilled water that is odor-free.NOTE 2If diluent other than water is used, equivalent ppm (vol/vol)values will not exhibit matching odor in
48、tensities because of differences inmolecular weights, densities, and the activity coefficients of 1-butanol indifferent solvents. Use of other solvents is therefore not recommended.6.2 Follow the procedures outlined in Section 5, except for5.2.6.3 Preparation of Static Scale:6.3.1 Prepare solutions
49、of 1-butanol in water, using pipetsand volumetric flasks, following the usual laboratory proce-dures for solution preparation.6.3.2 ProcedurePlace the reference sniffing solutions intostandard 500-mL wide-mouth, conical Erlenmeyer flasks (seeTest Method D 1292). The volume of solution should be 200mL and should be replaced by new solutions after a maximumperiod of 2 h. Between sniffings, cover the top of each flaskwith aluminum foil in order to assure equilibration between thesolution and the air head-space above it. The flasks should begently shaken by each panelist
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