1、Designation: D7536 16Standard Test Method forChlorine in Aromatics by Monochromatic WavelengthDispersive X-ray Fluorescence Spectrometry1This standard is issued under the fixed designation D7536; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the 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 the determination of chlorine bymonochromatic, wavelength-dispersive
3、X-ray fluorescence(MWDXRF) spectrometry in aromatic hydrocarbons, theirderivatives, and related chemicals.1.2 This test method is applicable to samples with chlorineconcentrations from 0.66 mg/kg to 10.07 mg/kg. Higherchlorine concentrations can be determined by quantitativelydiluting the sample wit
4、h a suitable solvent. In an interlabora-tory study, the limit of detection was determined to be 0.18mg/kg.1.3 In determining the conformance of the test results usingthis method to applicable specifications, results shall berounded off in accordance with the rounding-off method ofPractice E29.1.4 Th
5、e values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pria
6、te safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardinformation, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D3437 Practice for Sampling and Handling Liquid CyclicProductsD4790 Terminology of Aromatic Hydrocarbons an
7、d RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Pr
8、ecision of a Test Method2.2 Other Documents:3OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.12003. Terminology3.1 See Terminology D4790 for definitions of terms used inthis test method.4. Summary of Test Method4.1 A monochromatic X-ray beam with a wavelength suit-able to excite the K-shell el
9、ectrons of chlorine is focused ontoa test specimen contained in a sample cell (see Fig. 1). Thefluorescent K radiation at 0.473 nm (4.73) emitted bychlorine is collected by a fixed monochromator (analyzer). Theintensity (counts per second) of the chlorine X-rays is mea-sured using a suitable detecto
10、r and converted to the concen-tration of chlorine (mg/kg) in a test specimen using a calibra-tion equation. Excitation by monochromatic X-rays reducesbackground, simplifies matrix correction and increases thesignal/background ratio compared to polychromatic excitationused in conventional WDXRF techn
11、iques.45. Significance and Use5.1 This test method provides for the precise measurementof the chlorine content of aromatics with minimal samplepreparation and analyst involvement. The typical time for eachanalysis is five or ten minutes.5.2 Knowledge of the chlorine content of aromatics isimportant
12、for process control as well as the prediction and1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved June 1, 2016. Published July 2016.
13、 Originally approvedin 2009. Last previous edition approved in 2009 as D7356 09. DOI: 10.1520/D7536-16.2For 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
14、 Document Summary page onthe ASTM website.3Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.4Bertin, E. P., Principles and Practices of X-ray Spectrometric Analysis, PlenumPress, New York
15、, 1975, pp. 115-118.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1control of operational problems such as unit corrosion andcatalyst poisoning, and in the blending of products to com-modity specifications.5.3 Various federal, state,
16、 and local agencies regulate thechlorine content of some petroleum products, including aro-matics. Unbiased and precise determination of chlorine inaromatics is critical to compliance with regulatory standards.5.4 When the elemental composition of the samples differsignificantly from the calibration
17、 standards used to prepare thecalibration curve, the cautions and recommendation in Section6 should be carefully observed.6. Interferences6.1 Differences between the elemental composition of testsamples and the calibration standards can result in biasedchlorine determinations. For aromatics within t
18、he scope of thistest method, matrix correction can be avoided with a properchoice of calibrants. To minimize any bias in the results, usecalibration standards prepared from chlorine-free base materi-als of the same or similar elemental composition as the testsamples.7. Apparatus7.1 Monochromatic Wav
19、elength Dispersive X-ray Fluores-cence (MWDXRF) Spectrometer5, equipped for X-ray detec-tion at 0.473 nm (4.73). Any spectrometer of this type can beused if it includes the following features, and the precision oftest results are in accordance with the values described inSection 16.7.1.1 X-ray Sourc
20、e, capable of producing X-rays to excitechlorine. X-ray tubes capable of producing Rh L,PdL,AgL,TiK,ScK, and Cr K radiation are recommended forthis purpose.7.1.2 Incident-beam Monochromator, capable of focusingand selecting a single wavelength of characteristic X-rays fromthe source onto the specime
21、n.7.1.3 Optical Path, designed to minimize the absorptionalong the path of the excitation and fluorescent beams using avacuum or a helium atmosphere. The calibration and testmeasurements must be done with identical optical paths,including vacuum or helium pressure.7.1.4 Monochromator, suitable for d
22、ispersing chlorine KX-rays.7.1.5 Detector, designed for efficient detection of chlorineK X-rays.7.1.6 Single-Channel Analyzer, an energy discriminator tomonitor only chlorine radiation.7.2 Removable Sample Cell, any specimen holder compat-ible with the geometry of the MWDXRF spectrometer anddesigned
23、 to use X-ray transparent film (see 7.3) to hold a liquidspecimen with a minimum depth of 3 mm. The sample cellmust not leak when fitted with X-ray transparent film. Adisposable cell is recommended.7.3 X-ray Transparent Film, for containing and supportingthe test specimen in the sample cell (see 7.2
24、) while providinga low-absorption window for X-rays to pass to and from thesample. Any film resistant to chemical attack by the sample,free of chlorine, and X-ray transparent may be used.7.4 Analytical balance capable of reading to 0.0001 g.8. Reagents and Materials8.1 Purity of ReagentsReagent grad
25、e chemicals shall beused in all tests. Unless otherwise indicated, it is intended that5The sole source of supply of the apparatus known to the committee at this timeis X-Ray Optical Systems, Inc., 15 Tech Valley Drive, East Greenbush, NY, 12061.If you are aware of alternative suppliers, please provi
26、de this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.FIG. 1 Schematic of the MWDXRF AnalyzerD7536 162all reagents conform to the specifications of the Committee onAnalytical Re
27、agents of the American Chemical Society wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Calibration-Check Samples, for verifying t
28、he accuracyof a calibration. The check samples must have known chlorinecontent and not be used in determining the calibration curve. Astandard from the same reliable and consistent source ofcalibration standards used to determine the calibration curve isconvenient to check the calibration.8.3 2-Prop
29、anol, minimum 99 % purity, for cleaning ofanalyzer parts in the sample chamber that may becomecontaminated with spilled samples and other contaminants.8.4 1,2,4-Trichlorobenzene, a high-purity liquid (minimum99 % purity) with a certified chlorine concentration. Use thecertified chlorine concentratio
30、n when calculating the exactconcentrations of chlorine in calibration standards.8.5 Quality-Control Samples, for use in establishing andmonitoring the stability and precision of an analytical measure-ment system (see Section 17). Use homogeneous materials,similar to samples of interest and available
31、 in sufficientquantity to be analyzed regularly for a long period of time.NOTE 1Verification of system control through the use of QC samplesand control charting is highly recommended.NOTE 2Suitable QC samples can be prepared by combining retains oftypical samples.8.6 Xylene, use a high purity p-xyle
32、ne HPLC grade andaccount for its chlorine content when calculating the chlorineconcentration of the calibration standards.8.7 Drift-Monitor Sample (optional), to determine and cor-rect instrument drift over time (see 12.4, 13.2, and 14.2).Various forms of stable chlorine-containing materials aresuit
33、able drift-correction samples, for example, liquidpetroleum, solid, and pressed powder. The count rate displayedby the monitor sample, in combination with a convenient counttime (T), shall be sufficient to give a relative standard deviation(RSD) of 1 % (see Appendix X1).NOTE 3Calibration standards m
34、ay be used as drift-monitor samples.NOTE 4Because it is desirable to discard test specimens after eachdetermination, a lower cost material is suggested for daily use. Any stablematerial can be used for daily monitoring of drift.NOTE 5The effect of drift correction on the precision and bias of thiste
35、st method has not been studied.9. Hazards9.1 WarningExposure to excessive quantities of X-rayradiation is injurious to health. The operator needs to takeappropriate actions to avoid exposing any part of his/her body,not only to primary X-rays, but also to secondary or scatteredradiation that might b
36、e present. The X-ray spectrometer shouldbe operated in accordance with the regulations governing theuse of ionizing radiation.9.2 Consult current OSHA regulations, suppliers SafetyData Sheets and local regulations for all materials used in thistest method.10. Sampling and Handling10.1 Sample the mat
37、erial in accordance with PracticeD3437.10.2 For each sample, an unused piece of X-ray transparentfilm is required for the sample cell. Avoid touching the insideof the sample cell, any portion of the film exposed to the liquidor the X-ray beam, and also avoid touching the instrumentwindow. Oil from f
38、ingerprints and wrinkles can generate errorsin the analysis of chlorine. Therefore, make sure the film is tautand clean to ensure reliable results. It is recommended to usecanned air to ensure the film and sample cup is dust free priorto assembling sample cell. Use calibration-check samples (see8.2)
39、 to verify calibration integrity if the type and thickness ofthe window film is changed. After the sample cell is filled,provide a vent above the sample to prevent bowing of the filmby accumulating vapors. When reusable sample cells are used,thoroughly clean and dry cells before each use. Disposable
40、sample cells shall not be reused.10.3 Because impurities and thickness variations can occurin commercially available transparent films and vary from lotto lot, use calibration-check samples (see 8.2) to verifycalibration integrity after starting each new batch of film.11. Preparation of Apparatus11.
41、1 Analyzer PreparationEnsure that the MWDXRFanalyzer has been installed and put into operation in accor-dance with manufacturers instructions. Allow sufficient timefor instrument electronics to stabilize. Perform any instrumentcheckout procedures required. When possible, the instrumentshould be run
42、continuously to maintain optimum stability.11.1.1 Use the count time (T) recommended by the instru-ment manufacturer for the lowest chlorine concentration ex-pected. The typical time for each measurement is five or tenminutes.11.1.2 Alternatively, determine T expected for a desiredcount precision by
43、 following the procedure in Appendix X1.11.2 Minimizing Analyzer ContaminationAnalyzer con-tamination may lead to falsely high measurement results. Tominimize analyzer contamination, perform the following stepsat least once each day the analyzer is in use.11.2.1 Clean the portion of the lid that is
44、in contact with thetop of the sample cell with 2-propanol. Additionally, clean thelid after measurement of a sample containing greater than 50mg/kg chlorine and prior to the measurement of samplecontaining less than 1 mg/kg chlorine. Residue from higherconcentration samples may contaminate subsequen
45、t low con-centration measurements. Wipe up any visible sample residueafter sample measurement.11.2.2 Clean the primary window with 2-propanol soakedfoam tipped or cotton swab. Shake excess alcohol from swabprior to using it for cleaning, as excess alcohol on the swab6Reagent Chemicals, American Chem
46、ical Society Specifications, AmericanChemical Society, Washington, D. C. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BD Ltd., Pole, Dourest, U. K., and the United States Pharmacopoeiaand National Formulary, U. S
47、. Pharmaceutical Convention, Inc. (SUPT.),Rockville, MD.D7536 163may leave a residue on the primary window when it dries. I isrecommended to use canned air to blow the window dry. Foranalyzers with disposable primary windows, change the win-dow instead of cleaning it.11.2.3 Clean the sample basket w
48、ith 2-propanol.Additionally, clean the sample basket any time the sample cellleaks in the measurement chamber.11.2.4 If the analyzer is equipped with a secondary window,change the film. It is recommended to use canned air to ensurethe film is dust free prior to reassembling the secondarywindow. Peri
49、odically inspect the secondary window andchange if wrinkled, dirty, torn, or if there is a sample cell leakin the measurement chamber. Additionally, change the second-ary window after measurement of a sample containing greaterthan 50 mg/kg chlorine prior to the measurement of samplescontaining less than 1 mg/kg chlorine. Residue vapors fromhigher concentration samples may be absorbed by the film andcontaminate subsequent low concentration measurements.12. Calibration12.1 Stock SolutionPrepare a 1000 mg/kg chlorine inp-xylene stock solution by weighing appro
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