1、Designation: D2929 89 (Reapproved 2011)Standard Test Method forSulfur Content of Cellulosic Materials by X-RayFluorescence1This standard is issued under the fixed designation D2929; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers determination of sulfur contentof cellulosic materials by X-ray fluorescence.1.2 Us
3、ing appropriate standards, the range of the procedureis from approximately 10 ppm to 20 % sulfur.1.3 This test method is proposed specifically as an alterna-tive to Test Methods D871, sections on Significance and Use,Apparatus, Reagents, Procedure and Calculation of HydroxylContent, and Test Methods
4、 D817, sections on Summary of TestMethod, Significance and Use, Apparatus, Reagents, andProcedure of Hydroxyl Content. As applied to cellulose estersit measures the combined sulfur and sulfur in the accompany-ing inorganic salts.1.4 To determine combined sulfur, the sample, whensoluble, must first b
5、e reprecipitated into dilute acid to removethe noncombined sulfur compounds.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with it
6、s use. It is 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. For a specifichazard statement, see 7.2.1.2. Referenced Documents2.1 ASTM Standards:2D817 Test Methods of Testing
7、 CelluloseAcetate Propionateand Cellulose Acetate ButyrateD871 Test Methods of Testing Cellulose Acetate3. Summary of Test Method3.1 The sulfur content of cellulose, cellulose modification,or cellulose derivative is determined by measuring the intensityof the secondary sulfur Ka X rays emitted on ir
8、radiation of thesample with primary X rays of higher energy from an X-raytube with a target of tungsten or chromium. The sulfur Karadiation is diffracted with a suitable analyzing crystal anddetected with a flow-proportional counter. The entire path ofthe secondary radiation is purged with hydrogen
9、or helium, orevacuated to a pressure of 0.5 mm Hg or less. The intensity ofthe sulfur Ka rays, as established by a standard counting periodand corrected for background radiation, is then converted topercent sulfur from calibration data.34. Significance and Use4.1 This procedure provides a method for
10、 determiningsulfur content in cellulosic materials by nondestructive means.Sulfur may be in the form of sulfate esters that may contributeto thermal instability. Sulfur can also be present as salts thatcan cause haze in solutions.5. Apparatus5.1 Wiley Mill, equipped with 60-mesh screen.5.2 Sample Mo
11、ldChrome steel die of a size depending onthe sample holder to be used.5.3 Laboratory Press, capable of exerting at least 5000 psi.5.4 X-Ray Spectrograph, with following equipment: tung-sten or chromium target X-ray tube; hydrogen or heliumpurging system or vacuum system to reach 0.5 mm Hg (or less,i
12、f desired); 20-mil Soller slits; flow-proportional counter with90 % argon-10 % methane gas mixture; and NaCl, ethylenedi-amine dextro tartrate (EDT), or pentaerythritol (PET) analyz-ing crystal.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials,
13、 and Applications and is the direct responsibility ofSubcommittee D01.36 on Cellulose and Cellulose Derivatives.Current edition approved June 1, 2011. Published June 2011. Originallyapproved in 1970. Last previous edition approved in 2006 as D2929 89 (2006).DOI: 10.1520/D2929-89R11.2For referenced A
14、STM 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 Summary page onthe ASTM website.3This test method is compiled from four techniques, by incorporating certainfe
15、atures of each, as follows: “Sulfur in Cellulose Esters by X-ray EmissionSpectroscopy,” Eastman Kodak Co.; “Sulfur in Cellulose Acetate by X-rayFluorescence,” Tennessee Eastman Co.; “X-ray Fluorescence Analysis of ModifiedCottons” by Tripp, Piccolo, Mitcham and OConnor. Textile Research Journal,Vol3
16、4, 1964, p. 773, and FMC Corp., American Viscose Div. information furnished byL. H. Phifer and W. B. Swann.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 1Radiation from a chromium target tube appears to be moreeffective than r
17、adiation from a tungsten target tube for exciting sulfur Ka.This may be because a larger part of the “white” radiation of thechromium tube is at the longer wavelength region of the spectrum, orbecause of the use of thinner windows in the chromium tube. However,either the chromium or the tungsten tar
18、get tube is suitable for sulfuranalysis. If a pulse height analyzer is available as a part of the X-rayinstrumentation, its use is very helpful in reducing background radiation.Use of a pulse height analyzer is mandatory for the determination of sulfurbelow 100 to 200 ppm level.6. Reagents6.1 Ethyl
19、Cellulose Phthalate.6.2 Microcrystalline Cellulose.6.3 Cystine, NIST primary standard No. 143B.7. Procedure7.1 Instrument Standardization Pellet Intimately mixethyl cellulose phthalate, microcrystalline cellulose, or otherselected matrix with finely divided cystine in a weight ratio ofapproximately
20、4:1. Press a portion into a pellet in the samplemold for 30 s using a pressure of 5000 lb on the mold. Makesure that the thickness of the sample pellet is 1.6 mm (116 in.)or greater.7.2 Standardization of Instrument:NOTE 2Basic standardization techniques and operating parametersvary from instrument
21、to instrument. The manufacturers literature and theanalysts knowledge of the performance characteristics of the equipmentshould be used as a guide in performing this function.7.2.1 Place a standardization pellet in the sample holder andcenter it so that it covers the entire window of the holder.Evac
22、uate the X-ray path to a pressure of 0.5 mm Hg (or less,if desired) or flush the path with hydrogen or helium. Set thegas flow of the proportional counter as suggested by themanufacturer. (WarningX rays are very hazardous. Do notturn the equipment on until the instruction manual has beenread and und
23、erstood.)7.2.2 Set the goniometer of the X-ray spectrograph at theappropriate sulfur Ka angle. Turn the X-ray tube on, using themanufacturers recommended voltage and current. Selection ofthe operating voltage and current of the X-ray tube is governedby the type of tube used. Take care not to exceed
24、the ratedpower output (in watts) of the X-ray tube. Make a plot of thesulfur X-ray intensity versus applied voltage to the detector.Make sure that the voltage chosen is approximately midway onthe plateau.7.2.3 If a pulse height analyzer is being used, a commonway to arrive at the proper settings is
25、to set the gain of thelinear amplifier at approximately half of its maximum. Selectthe detector voltage about midway on the plateau. Set theminimum pulse rejection voltage at about 5 V and the DE atabout 10 V. Observe the intensity without the pulse heightanalyzer on. With the pulse height analyzer
26、on, change eitherthe amplifier gain control or the detector voltage until as nearas possible the same intensity as without the analyzer isobtained. Then increase or decrease the DE control just until amaximum intensity is reached.7.3 Calibration for Measurement of Sulfur:7.3.1 Select five or more re
27、presentative cellulosic sampleswhose sulfur contents, as determined by chemical analysisaccording to Test Methods D817 or D871, completely coverthe required range. Since X-ray fluorescence intensities arefunctions of concentrations per unit volume, prepare standardsused to establish the calibration
28、curve in a matrix as nearlyidentical to that of the sample as possible. Distribute thesulfur-containing component very uniformly in the matrix. Thephysical form of the matrix (powder, flake, pellet, or sheet) isa significant variable. For accurate work it may be necessary tohave separate calibration
29、s for each form of sample.7.3.1.1 As a calibration standard for cellulose, microcrys-talline cellulose containing intimately mixed known amountsof cystine may be used.Achemical analysis of the standards isgenerally not necessary.7.3.2 Prepare the samples for analysis according to 7.4 and7.5.7.3.3 Me
30、asure the intensities of the sulfur Ka X rays of thestandard samples according to 7.6.7.3.4 Prepare a calibration curve relating sulfur Ka X-rayintensity expressed as net counts per second to percent sulfur.7.4 Treatment of Sample Prior to Analysis:7.4.1 To analyze for total sulfur content, no treat
31、ment isrequired prior to analysis. If the sample has a high absorbingcoating (for example, saran, PVC, etc.) remove them or astandard containing a matrix of those materials in equivalentconcentrations must be prepared.7.4.2 When analyzing for combined sulfur content, as in acellulose ester, remove t
32、he uncombined sulfur as follows:7.4.2.1 Dissolve 25 g of sample in approximately 300 mLofacetone, depending on the viscosity. If the sample is of too highacetyl content to be directly soluble in acetone, cool in a dry icecabinet overnight, then allow to come to room temperaturewhile tumbling or stir
33、ring.7.4.2.2 Filter the solution, if necessary, through felt or acoarse sintered-glass crucible.7.4.2.3 Precipitate with rapid stirring into a beaker or pailcontaining 2 to 3 L of acetic acid-water (1:49).7.4.2.4 Filter through a cloth bag or a Bchner funnel andgive two 15-min washes with water usin
34、g mechanical agita-tion.Alittle Na2CO3may be added to the last wash to stabilizesamples of high sulfur content.7.4.2.5 Filter and dry overnight at 60C.7.5 Preparation of Specimen for Analysis:7.5.1 Grind the sample in a Wiley Mill to pass a 60-meshscreen. Mold a quantity of the sample for 30 s with
35、a gagepressure to 5000 lb on the mold. Use sufficient sample to obtaina disk at least 1.6-mm (116-in.) thick.7.5.2 Film specimens can be run directly (without grinding)by using a multiplicity of sheet thicknesses, provided that thespecimen contains no air trapped between the successivelayers. If fil
36、m specimens are coated with a high absorbingcoating (for example, saran, PVC, or aluminum), these must beremoved if the specimens are to be analyzed as multiplethicknesses. Similarly, a closely wrapped specimen of continu-ous filament yarn can also be tested directly.7.6 Measurement of Intensity of
37、Sulfur Ka X rays:7.6.1 Place the specimen in the sample holder of the X-rayspectrograph and center so that it covers the entire sample-holder window.D2929 89 (2011)27.6.2 Evacuate the X-ray path to a pressure of 0.5 mm Hg orless or flush the path with hydrogen or helium.7.6.3 Record the X-ray count
38、for a standard time period atthe sulfur Ka angle.7.6.4 Repeat the count on the opposite side of the specimenpellet if homogeneity is questioned.7.6.5 If a sulfur-free specimen is available, record thebackground count. This is unnecessary if the standards ma-trixes are identical to the samples.NOTE 3
39、A background count is desirable at all concentration levels. Itis mandatory for measurement of sulfur concentrations under 100 ppm.NOTE 4An indication of the precision of this test method is given bythe standard counting error, which is:sc5 =NT1 = NB(1)where:sc= standard counting error of NT NB,NT=
40、counts accumulated at sulfur Ka angle during counting inter-val Dt, andNB= counts accumulated at background during same countinginterval Dt.This error level calculation should be used as a guide to counting time.8. Calculation8.1 Convert the standard time count values of the specimenand the backgrou
41、nd to counts per second.8.2 If the background is measured subtract the backgroundcount rate from the count rate of the specimen pellet to obtainthe net count rate of the specimen.8.3 Convert the net count rate of the specimen to percentsulfur by using the calibration curve.9. Precision and Bias9.1 T
42、he precision of measurement, or standard deviation, s,is calculated by normal statistical methods as follows.s5(x 2 x!2n 2 1(2)where:x = measured value,x = mean value of n measurements, andn = number of measurements.9.1.1 The practical significance of s is that 68 % of allresults should be within 61
43、s of the mean, 95 % with 62s and99.7 % within 63s.9.1.2 Since random processes are involved in x-ray analysis,precision can also be determined from the fact that standarddeviation is equal to the square root of the number of counts,N, collected.sN 5 =N (3)9.1.3 It may be more relevant to express pre
44、cision in termsof the coefficient of variation, Ewhich is the standard deviationas a percent of the number of counts as follows:E 5= NN3 100 5100=N(4)9.2 Bias has not been evaluated for this test method.10. Keywords10.1 cellulose esters; combined sulfur; salts; pulse heightanalyzerASTM International
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48、t the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D2929 89 (2011)3
