1、Designation: D 7536 09Standard Test Method forChlorine in Aromatics by Monochromatic WavelengthDispersive X-ray Fluorescence Spectrometry1This standard is issued under the fixed designation D 7536; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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-dispersiv
3、e X-ray fluorescence(MWDXRF) spectrometry in aromatic hydrocarbons, theirderivatives, and related chemicals.1.2 This test method is applicable to samples with chlorineconcentrations from 0.5 mg/kg to 15 mg/kg. Higher chlorineconcentrations can be determined by quantitatively diluting thesample with
4、a suitable solvent. In a preliminary robustnessstudy, the limit of detection was estimated to be 0.06 mg/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
5、The 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-pr
6、iate 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:2D 3437 Practice for Sampling and Handling Liquid CyclicProductsD 4790 Terminology of Aromatic Hydrocarbon
7、s and Re-lated ChemicalsD 6809 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 Specifications2.2 Other Documents:3OSHA Regulations, 29 CFR paragraphs 1910.100
8、0 and1910.12003. Terminology3.1 See Terminology D 4790 for definitions of terms usedin this test method.4. Summary of Test Method4.1 A monochromatic X-ray beam with a wavelength suit-able to excite the K-shell electrons of chlorine is focused ontoa test specimen contained in a sample cell (see Fig.
9、1). Thefluorescent Ka 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 detector and converted to the concen-tration of chlorine (mg/kg) in a test specimen using a ca
10、libra-tion equation. Excitation by monochromatic X-rays reducesbackground, simplifies matrix correction and increases thesignal/background ratio compared to polychromatic excitationused in conventional WDXRF techniques.45. Significance and Use5.1 This test method provides for the precise measurement
11、of 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 for process control as well as the prediction andcontrol of operational problems such a
12、s unit corrosion andcatalyst poisoning, and in the blending of products to com-modity specifications.5.3 Various federal, state, and local agencies regulate thechlorine content of some petroleum products, including aro-matics. Unbiased and precise determination of chlorine inaromatics is critical to
13、 compliance with regulatory standards.5.4 When the elemental composition of the samples differsignificantly from the calibration standards used to prepare the1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibili
14、ty ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved Sept. 1, 2009. Published September 2009.2For 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 t
15、he standards 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,Plenum Pre
16、ss, New York, 1975, pp. 115-118.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.calibration curve, the cautions and recommendation in Section6 should be carefully observed.6. Interferences6.1 Differences between the elemental composi
17、tion of testsamples and the calibration standards can result in biasedchlorine determinations. For aromatics within the 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-f
18、ree base materi-als of the same or similar elemental composition as the testsamples.7. Apparatus7.1 Monochromatic Wavelength 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
19、features, and the precision oftest results are in accordance with the values described inSection 16.7.1.1 X-ray Source, capable of producing X-rays to excitechlorine. X-ray tubes capable of producing Rh La,PdLa,AgLa,TiKa,ScKa, and Cr Ka radiation are recommended forthis purpose.7.1.2 Incident-beam M
20、onochromator, capable of focusingand selecting a single wavelength of characteristic X-rays fromthe source onto the specimen.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 testmea
21、surements must be done with identical optical paths,including vacuum or helium pressure.7.1.4 Monochromator, suitable for dispersing chlorine KaX-rays.7.1.5 Detector, designed for efficient detection of chlorineKa X-rays.7.1.6 Single-Channel Analyzer, an energy discriminator tomonitor only chlorine
22、radiation.7.2 Removable Sample Cell, any specimen holder compat-ible with the geometry of the MWDXRF spectrometer anddesigned 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. Adisposab
23、le cell is recommended.7.3 X-ray Transparent Film, for containing and supportingthe test specimen in the sample cell (see 7.2) 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
24、may be used.7.4 Analytical balance capable of reading to 0.0001 g.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the
25、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 the accuracyof
26、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.5The sole source of supp
27、ly 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 provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ame
28、eting of the responsible technical committee,1which you may attend.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, D. C. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Annular Standards for LaboratoryChem
29、icals, BD Ltd., Pole, Dourest, U. K., and the United States Pharmacopoeiaand National Formulary, U. S. Pharmaceutical Convention, Inc. (SUPT.), Rock-ville, MD.FIG. 1 Schematic of the MWDXRF AnalyzerD75360928.3 2,3,4-Trichlorophenol, a high-purity liquid (minimum99 % purity) with a certified chlorine
30、 concentration. Use thecertified chlorine concentration when calculating the exactconcentrations of chlorine in calibration standards.78.4 Quality-Control Samples, for use in establishing andmonitoring the stability and precision of an analytical measure-ment system (see Section 17). Use homogeneous
31、 materials,similar to samples of interest and available 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
32、 oftypical samples.8.5 Xylene, use a high purity p-xylene HPLC grade andaccount for its chlorine content when calculating the chlorineconcentration of the calibration standards.8.6 Drift-Monitor Sample (optional), to determine and cor-rect instrument drift over time (see 12.4, 13.2, and 14.2).Variou
33、s forms of stable chlorine-containing materials aresuitable drift-correction samples, for example, liquid petro-leum, solid, and pressed powder. The count rate displayed bythe monitor sample, in combination with a convenient counttime (T), shall be sufficient to give a relative standard deviation(RS
34、D) of 1 % (see Appendix X1).NOTE 3Calibration standards may 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 effec
35、t of drift correction on the precision and bias of thistest 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,
36、 but also to secondary or scatteredradiation that might be present. The X-ray spectrometer shouldbe operated in accordance with the regulations governing theuse of ionizing radiation.9.2 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets and local regulations for all materials us
37、edin this test method.10. Sampling and Handling10.1 Sample the material in accordance with PracticeD 3437.10.2 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
38、-ray beam, and also avoid touching the instrumentwindow. Oil from fingerprints and wrinkles can generate errorsin the analysis of chlorine. Therefore, make sure the film is tautand clean to ensure reliable results. Use calibration-checksamples (see 8.2) to verify calibration integrity if the type an
39、dthickness of the window film is changed. After the sample cellis filled, provide a vent above the sample to prevent bowing ofthe film by accumulating vapors. When reusable sample cellsare used, thoroughly clean and dry cells before each use.Disposable sample cells shall not be reused.10.3 Because i
40、mpurities 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 Apparatus11.1 Analyzer PreparationEnsure that the MWDXRFana
41、lyzer 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 continuously to maintain optimum stability.11.1
42、.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 following the procedure in Appendix X1.12. Cal
43、ibration12.1 Stock SolutionPrepare a 1000 mg/kg chlorine inp-xylene stock solution by weighing approximately 0.16 g of2,3,4-trichlorophenol to the nearest 0.0001 g into a 100 mLvolumetric flask. Dilute to the mark with chlorine freep-xylene. Calculate the actual concentration of the stocksolution by
44、 using the equation:mg/kg chlorine 5 weight of trichlorophenol in g 3 0.53873 1 000 000! / 86.1 (1)where:0.5387 = % chloride in trichlorophenol / 100 and86.1 = weight of 100 mL of p-xlyene (density = 0.861g/mL).NOTE 6Alternate stock solutions may be prepared as long as theconcentration is accurately
45、 calculated.12.2 Prepare a minimum of 4 calibration standards byquantitatively diluting the stock solution with chlorine-freep-xylene. For example, 1 mL of the stock solution prepared in12.1 diluted to 100 mL with p-xylene in a 100 mL volumetricflask will give a calibration standard of 10.0 mg/kg ch
46、lorine.Following instrument manufacturers instructions and the in-structions in 13.3, measure the chlorine fluorescence intensity(total chlorine count rate) for each of the calibration standards.Convert total counts to count rate (RS) in counts per second bydividing total counts by the count time (T
47、) using units ofseconds (see 11.1.1 and 11.1.2).NOTE 7Alternately, commercially available calibration standards maybe used provided their use does not lessen the accuracy of the determi-nation.12.3 Construct a linear calibration model by either:12.3.1 Using the software supplied by the instrument ma
48、nu-facturer, or12.3.2 Do a linear regression of the calibration measure-ments. The linear equation:RS5 Y 1 E 3 S! (2)7Possible source for 99 % purity 2,3,4 trichlorophenol is Sigma-Aldrich.D7536093describes the regression where:RS= measured total count rate (counts per second) of thechlorine fluores
49、cence from 12.2,Y = y-intercept of the calibration curve (counts per sec-ond),E = slope of the calibration curve (counts kg s-1mg-1),andS = chlorine concentration (mg/kg).12.4 When using drift correction, measure the total countsof chlorine fluorescence from the drift-monitor sample duringthe calibration procedure. Determine RSby dividing the totalcounts by T. The factor, RS, determined on the drift-monitorsample at the time of calibration, is factor “A” in Eq 3 in 14.1.12.5 Immediately after analyzing the calibration standards,determine the chlorine concentration
