ASTM D7536-09
(Test Method)Standard Test Method for Chlorine in Aromatics by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry
Standard Test Method for Chlorine in Aromatics by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry
SIGNIFICANCE AND USE
This test method provides for the precise measurement of the chlorine content of aromatics with minimal sample preparation and analyst involvement. The typical time for each analysis is five or ten minutes.
Knowledge of the chlorine content of aromatics is important for process control as well as the prediction and control of operational problems such as unit corrosion and catalyst poisoning, and in the blending of products to commodity specifications.
Various federal, state, and local agencies regulate the chlorine content of some petroleum products, including aromatics. Unbiased and precise determination of chlorine in aromatics is critical to compliance with regulatory standards.
When the elemental composition of the samples differ significantly from the calibration standards used to prepare the calibration curve, the cautions and recommendation in Section 6 should be carefully observed.
SCOPE
1.1 This test method covers the determination of chlorine by monochromatic, wavelength-dispersive X-ray fluorescence (MWDXRF) spectrometry in aromatic hydrocarbons, their derivatives, and related chemicals.
1.2 This test method is applicable to samples with chlorine concentrations from 0.5 mg/kg to 15 mg/kg. Higher chlorine concentrations can be determined by quantitatively diluting the sample with a suitable solvent. In a preliminary robustness study, the limit of detection was estimated to be 0.06 mg/kg.
1.3 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off in accordance with the rounding-off method of Practice E 29.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard information, see Section 9.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7536 − 09
StandardTest Method for
Chlorine in Aromatics by Monochromatic Wavelength
Dispersive X-ray Fluorescence Spectrometry
This standard is issued under the fixed designation D7536; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications
1.1 Thistestmethodcoversthedeterminationofchlorineby
monochromatic, wavelength-dispersive X-ray fluorescence 2.2 Other Documents:
(MWDXRF) spectrometry in aromatic hydrocarbons, their OSHA Regulations, 29 CFR paragraphs 1910.1000 and
derivatives, and related chemicals. 1910.1200
1.2 This test method is applicable to samples with chlorine
3. Terminology
concentrations from 0.5 mg/kg to 15 mg/kg. Higher chlorine
concentrationscanbedeterminedbyquantitativelydilutingthe
3.1 See Terminology D4790 for definitions of terms used in
sample with a suitable solvent. In a preliminary robustness
this test method.
study, the limit of detection was estimated to be 0.06 mg/kg.
4. Summary of Test Method
1.3 In determining the conformance of the test results using
this method to applicable specifications, results shall be
4.1 A monochromatic X-ray beam with a wavelength suit-
rounded off in accordance with the rounding-off method of
able to excite the K-shell electrons of chlorine is focused onto
Practice E29.
a test specimen contained in a sample cell (see Fig. 1). The
1.4 The values stated in SI units are to be regarded as fluorescent Kα radiation at 0.473 nm (4.73Å) emitted by
standard. No other units of measurement are included in this chlorine is collected by a fixed monochromator (analyzer).The
standard. intensity (counts per second) of the chlorine X-rays is mea-
sured using a suitable detector and converted to the concen-
1.5 This standard does not purport to address all of the
tration of chlorine (mg/kg) in a test specimen using a calibra-
safety concerns, if any, associated with its use. It is the
tion equation. Excitation by monochromatic X-rays reduces
responsibility of the user of this standard to establish appro-
background, simplifies matrix correction and increases the
priate safety and health practices and determine the applica-
signal/background ratio compared to polychromatic excitation
bility of regulatory limitations prior to use.For specific hazard
used in conventional WDXRF techniques.
information, see Section 9.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 This test method provides for the precise measurement
D3437 Practice for Sampling and Handling Liquid Cyclic
of the chlorine content of aromatics with minimal sample
Products
preparation and analyst involvement.The typical time for each
D4790 Terminology ofAromatic Hydrocarbons and Related
analysis is five or ten minutes.
Chemicals
5.2 Knowledge of the chlorine content of aromatics is
D6809 Guide for Quality Control and Quality Assurance
important for process control as well as the prediction and
Procedures for Aromatic Hydrocarbons and Related Ma-
control of operational problems such as unit corrosion and
terials
catalyst poisoning, and in the blending of products to com-
modity specifications.
This test method is under the jurisdiction of ASTM Committee D16 on
Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of
Subcommittee D16.04 on Instrumental Analysis.
Current edition approved Sept. 1, 2009. Published September 2009. DOI:
10.1520/D7536-09. AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.access.gpo.gov.
Standards volume information, refer to the standard‘s Document Summary page on Bertin, E. P., Principles and Practices of X-ray Spectrometric Analysis, Plenum
the ASTM website. Press, New York, 1975, pp. 115-118.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7536 − 09
FIG. 1 Schematic of the MWDXRF Analyzer
5.3 Various federal, state, and local agencies regulate the 7.1.3 Optical Path, designed to minimize the absorption
chlorine content of some petroleum products, including aro- along the path of the excitation and fluorescent beams using a
matics. Unbiased and precise determination of chlorine in vacuum or a helium atmosphere. The calibration and test
aromatics is critical to compliance with regulatory standards. measurements must be done with identical optical paths,
including vacuum or helium pressure.
5.4 When the elemental composition of the samples differ
7.1.4 Monochromator, suitable for dispersing chlorine Kα
significantly from the calibration standards used to prepare the
X-rays.
calibration curve, the cautions and recommendation in Section
7.1.5 Detector, designed for efficient detection of chlorine
6 should be carefully observed.
Kα X-rays.
6. Interferences
7.1.6 Single-Channel Analyzer, an energy discriminator to
monitor only chlorine radiation.
6.1 Differences between the elemental composition of test
samples and the calibration standards can result in biased
7.2 Removable Sample Cell, any specimen holder compat-
chlorine determinations. For aromatics within the scope of this
ible with the geometry of the MWDXRF spectrometer and
test method, matrix correction can be avoided with a proper
designedtouseX-raytransparentfilm(see7.3)toholdaliquid
choice of calibrants. To minimize any bias in the results, use
specimen with a minimum depth of 3 mm. The sample cell
calibration standards prepared from chlorine-free base materi-
must not leak when fitted with X-ray transparent film. A
als of the same or similar elemental composition as the test
disposable cell is recommended.
samples.
7.3 X-ray Transparent Film, for containing and supporting
the test specimen in the sample cell (see 7.2) while providing
7. Apparatus
a low-absorption window for X-rays to pass to and from the
7.1 Monochromatic Wavelength Dispersive X-ray Fluores-
sample. Any film resistant to chemical attack by the sample,
cence (MWDXRF) Spectrometer , equipped for X-ray detec-
free of chlorine, and X-ray transparent may be used.
tion at 0.473 nm (4.73Å).Any spectrometer of this type can be
used if it includes the following features, and the precision of 7.4 Analytical balance capable of reading to 0.0001 g.
test results are in accordance with the values described in
Section 16. 8. Reagents and Materials
7.1.1 X-ray Source, capable of producing X-rays to excite
8.1 Purity of Reagents—Reagent grade chemicals shall be
chlorine. X-ray tubes capable of producing Rh Lα,PdLα,Ag
used in all tests. Unless otherwise indicated, it is intended that
Lα,TiKα,ScKα, and Cr Kα radiation are recommended for
all reagents conform to the specifications of the Committee on
this purpose.
Analytical Reagents of the American Chemical Society where
7.1.2 Incident-beam Monochromator, capable of focusing
such specifications are available. Other grades may be used,
andselectingasinglewavelengthofcharacteristicX-raysfrom
the source onto the specimen.
Reagent Chemicals, American Chemical Society Specifications, American
The sole source of supply of the apparatus known to the committee at this time Chemical Society, Washington, D. C. For suggestions on the testing of reagents not
is X-Ray Optical Systems, Inc., 15 Tech Valley Drive, East Greenbush, NY, 12061. listed by the American Chemical Society, see Analar Standards for Laboratory
If you are aware of alternative suppliers, please provide this information to ASTM Chemicals, BD Ltd., Pole, Dourest, U. K., and the United States Pharmacopoeia
International Headquarters. Your comments will receive careful consideration at a and National Formulary, U. S. Pharmaceutical Convention, Inc. (SUPT.),
meeting of the responsible technical committee, which you may attend. Rockville, MD.
D7536 − 09
provided it is first ascertained that the reagent is of sufficiently 10.2 For each sample, an unused piece of X-ray transparent
high purity to permit its use without lessening the accuracy of film is required for the sample cell. Avoid touching the inside
the determination. of the sample cell, any portion of the film exposed to the liquid
or the X-ray beam, and also avoid touching the instrument
8.2 Calibration-Check Samples, for verifying the accuracy
window. Oil from fingerprints and wrinkles can generate errors
of a calibration. The check samples must have known chlorine
intheanalysisofchlorine.Therefore,makesurethefilmistaut
content and not be used in determining the calibration curve.A
and clean to ensure reliable results. Use calibration-check
standard from the same reliable and consistent source of
samples (see 8.2) to verify calibration integrity if the type and
calibration standards used to determine the calibration curve is
thickness of the window film is changed.After the sample cell
convenient to check the calibration.
is filled, provide a vent above the sample to prevent bowing of
8.3 2,3,4-Trichlorophenol, a high-purity liquid (minimum
the film by accumulating vapors. When reusable sample cells
99 % purity) with a certified chlorine concentration. Use the
are used, thoroughly clean and dry cells before each use.
certified chlorine concentration when calculating the exact
Disposable sample cells shall not be reused.
concentrations of chlorine in calibration standards.
10.3 Because impurities and thickness variations can occur
8.4 Quality-Control Samples, for use in establishing and
in commercially available transparent films and vary from lot
monitoringthestabilityandprecisionofananalyticalmeasure-
to lot, use calibration-check samples (see 8.2) to verify
ment system (see Section 17). Use homogeneous materials,
calibration integrity after starting each new batch of film.
similar to samples of interest and available in sufficient
quantity to be analyzed regularly for a long period of time.
11. Preparation of Apparatus
NOTE 1—Verification of system control through the use of QC samples
and control charting is highly recommended.
11.1 Analyzer Preparation—Ensure that the MWDXRF
NOTE 2—Suitable QC samples can be prepared by combining retains of
analyzer has been installed and put into operation in accor-
typical samples.
dance with manufacturer’s instructions. Allow sufficient time
8.5 Xylene, use a high purity p-xylene HPLC grade and
for instrument electronics to stabilize. Perform any instrument
account for its chlorine content when calculating the chlorine
checkout procedures required. When possible, the instrument
concentration of the calibration standards.
should be run continuously to maintain optimum stability.
11.1.1 Use the count time (T) recommended by the instru-
8.6 Drift-Monitor Sample (optional), to determine and cor-
ment manufacturer for the lowest chlorine concentration ex-
rect instrument drift over time (see 12.4, 13.2, and 14.2).
pected. The typical time for each measurement is five or ten
Various forms of stable chlorine-containing materials are
minutes.
suitable drift-correction samples, for example, liquid
petroleum, solid, and pressed powder.The count rate displayed 11.1.2 Alternatively, determine T expected for a desired
bythemonitorsample,incombinationwithaconvenientcount count precision by following the procedure in Appendix X1.
time(T),shallbesufficienttogivearelativestandarddeviation
(RSD) of <1 % (see Appendix X1). 12. Calibration
NOTE 3—Calibration standards may be used as drift-monitor samples.
12.1 Stock Solution—Prepare a 1000 mg/kg chlorine in
NOTE 4—Because it is desirable to discard test specimens after each
p-xylene stock solution by weighing approximately 0.16 g of
determination, a lower cost material is suggested for daily use.Any stable
material can be used for daily monitoring of drift.
2,3,4-trichlorophenol to the nearest 0.0001 g into a 100 mL
NOTE 5—The effect of drift correction on the precision and bias of this
volumetric flask. Dilute to the mark with chlorine free
test method has not been studied.
p-xylene. Calculate the actual concentration of the stock
solution by using the equation:
9. Hazards
mg/kg chlorine 5 weight of trichlorophenol in g 30.5387
~
9.1 Warning—Exposure to excessive quantities of X-ray
31 000000!/86.1 (1)
radiation is injurious to health. The operator needs to take
appropriate actions to avoid exposing any part of his/her body,
where:
not only to primary X-rays, but also to secondary or scattered
0.5387 = % chloride in trichlorophenol / 100 and
radiation that might be present.The X-ray spectrometer should
86.1 = weight of 100 mL of p-xlyene (density = 0.861
be operated in accordance with the regulations governing the
g/mL).
use of ionizing radiation.
NOTE 6—Alternate stock solutions may be prepared as long as the
concentration is accurately calculated.
9.2 Consult current OSHA regulations, suppliers’ Material
Safety Data Sheets and local regulations for all materials used
12.2 Prepare a minimum of 4 calibration standards by
in this test method.
quantitatively diluting the stock solution with chlorine-free
p-xylene. For example, 1 mL of the stock solution prepared in
10. Sampling and Handling
12.1 diluted to 100 mL with p-xylene in a 100 mL volumetric
10.1 Sample the material in accordance with Practice flask will give a calibration standard of 10.0 mg/kg chlorine.
D3437. Following instrument manufacturer’s instructions and the in-
structions in 13.3, measure the chlorine fluorescence intensity
(total chlorine count rate) for each of the calibration standards.
Possible source for 99 % purity 2,3,4 trichlorophenol is Sigma-Aldrich. Convert total counts to count rate (R ) in counts per second by
S
D7536 − 09
dividing total counts by the count time (T) using units of 13.1.4 Perform the analysis of the specimen promptly after
seconds (see 11.1.1 and 11.1.2). preparing the specimen. Do not let the specimen remain in the
sample cell any longer than necessary before collecting the
NOTE7—Alternately,commerciallyavailablecalibrationstandardsmay
be used provided their use does not lessen the accuracy of the determi-
data.
nation.
13.2 Whenusingdriftcorrection,priortoanalyzingsamples
12.3 Construct a linear calibration model by either:
on a given day, analyze the drift-monitor sample measured at
the time of calibration. Divid
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.