ASTM C791-19

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C791 − 19
Standard Test Methods for
Chemical, Mass Spectrometric, and Spectrochemical
Analysis of Nuclear-Grade Boron Carbide
This standard is issued under the fixed designation C791; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover procedures for the chemical,
mass spectrometric, and spectrochemical analysis of nuclear- C750Specification for Nuclear-Grade Boron Carbide Pow-
der
grade boron carbide powder and pellets to determine compli-
ance with specifications. C751SpecificationforNuclear-GradeBoronCarbidePellets
C859Terminology Relating to Nuclear Materials
1.2 The values stated in SI units are to be regarded as the
C1128Guide for Preparation of Working Reference Materi-
standard. The values given in parentheses are for information
als for Use in Analysis of Nuclear Fuel Cycle Materials
only.
D1193Specification for Reagent Water
1.3 Theanalyticalproceduresappearinthefollowingorder:
E969Specification for Glass Volumetric (Transfer) Pipets
Sections
3. Terminology
Total Carbon by Combustion in an Inductive Furnace and 8–17
Infrared Measurement
3.1 Definitions—For definitions of terms relating to nuclear
Total Boron by Titrimetry and ICP OES 18–28
Isotopic Composition by Mass Spectrometry 29–33 materials, refer to Terminology C859.
Pyrohydrolysis 34–41
3.2 Definitions of Terms Specific to This Standard:
Chloride by Constant-Current Coulometry 42–50
Chloride and Fluoride by Ion-Selective Electrode 51–59
3.2.1 analyte—the constituent determined by a chemical
Water by Constant-Voltage Coulometry and Weight Loss on 60–63
measurement process.
Drying
Metallic Impurities by DCArc OES and wet chemical meth- 64 and 65
3.2.2 analytical or emission line—the particular wavelength
ods
of electromagnetic radiation used in determining the presence
Soluble Boron by Titrimetry and ICP OES 66–80
or concentration of an element.
Free Carbon by a Coulometric Method 81–90
1.4 This standard does not purport to address all of the 3.2.3 background—spectral intensity that would be mea-
safety concerns, if any, associated with its use. It is the
suredatthewavelengthoftheemissionlineiftheemissionand
responsibility of the user of this standard to establish appro- overlapping lines were not present.
priate safety, health, and environmental practices and deter-
3.2.4 calibration—the act, process, or result of establishing
mine the applicability of regulatory limitations prior to use.
the relationship between the response of an instrument and the
1.5 This international standard was developed in accor-
amount of analyte present.
dance with internationally recognized principles on standard-
3.2.5 calibration function—the graphical or mathematical
ization established in the Decision on Principles for the
representation of the relationship between the response of an
Development of International Standards, Guides and Recom-
instrument and the concentration or mass of the analyte.
mendations issued by the World Trade Organization Technical
3.2.6 calibration samples or solutions—samples or solu-
Barriers to Trade (TBT) Committee.
tions with known analyte contents or analyte concentrations,
respectively, to establish the relationship between the response
of an instrument and the amount of analyte.
These test methods are under the jurisdiction of ASTM Committee C26 on
Nuclear Fuel Cycle and are the direct responsibility of Subcommittee C26.03 on
Neutron Absorber Materials Specifications. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2019. Published March 2019. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1975. Last previous edition approved in 2012 as C791–12. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0791-19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C791 − 19
3.2.7 certified reference material (CRM)—a reference or not a given material meets the specifications for these items
material, accompanied by a certificate, one or more of whose as described in Specifications C750 and C751.
property values are certified by a procedure which establishes 4.1.1 An assay is performed to determine whether the
traceability to an accurate realization of the unit in which the material has the specified boron and carbon content.
property values are expressed, and for which each certified 4.1.2 Determinationoftheisotopiccontentoftheboronand
value is accompanied by an uncertainty at a stated level of thefreecarboncontentismadetoestablishwhetherthecontent
confidence. is in compliance with the purchaser’s specifications.
4.1.3 Impurity content is determined to ensure that the
3.2.8 DCArc OES—optical emission spectrometry (OES)
maximum concentration limit of certain impurities (chloride,
with direct current arc (DCArc) as excitation source.
fluoride, water, metallic impurities, soluble boron) is not
3.2.9 drift correction—the process of adjusting for a shift of
exceeded.
an instrument calibration.
5. Reagents
3.2.10 ICP MS—mass spectrometry (MS) with inductively
coupled plasma (ICP) as ionization source.
5.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
3.2.11 ICPOES—opticalemissionspectrometry(OES)with
all reagents shall conform to the specifications of the Commit-
inductively coupled plasma (ICP) as excitation source.
tee onAnalytical Reagents of theAmerican Chemical Society,
3.2.12 interlaboratory study (ILS)—a study undertaken to
where such specifications are available. Other grades may be
demonstrate the precision and bias of a test method.
used, provided it is first ascertained that the reagent is of
3.2.13 internal standard—a material present in or added to
sufficiently high purity to permit its use without lessening the
test samples that serves as an intensity reference for spectral
accuracy of the determination.
measurements.
5.2 Purity of Water—Unless otherwise indicated, references
3.2.14 matrix—all components of a material except the
towatershallbeunderstoodtomeanreagentwaterconforming
analyte.
to Specification D1193.
3.2.15 matrix matching—adjustment of the composition of
6. Safety Precautions
calibration samples or solutions to match the composition of
the matrix. 6.1 Many laboratories have established safety regulations
governing the use of hazardous chemicals and equipment. The
3.2.16 method—instructions used to produce a numerical
users of these methods should be familiar with such safety
result, which are detailed in a document referred to as “the
practices.
method.”
3.2.17 nebulizer—a device for converting a sample solution 7. Sampling
into a gas-liquid aerosol for ICP OES.
7.1 Criteria for sampling this material are given in Specifi-
3.2.18 optical emission spectrometry (OES)—pertaining to
cations C750 and C751.
emission spectrometry in the ultraviolet, visible, or infrared
TOTAL CARBON BY COMBUSTION IN AN
wavelength regions of the electromagnetic spectrum.
INDUCTIVE FURNACE AND INFRARED
3.2.19 repeatability, S —the standard deviation of results
r
MEASUREMENT
collected using the same method on the same material in the
same laboratory on different days.
8. Scope
3.2.20 reproducibility, S —the standard deviation of results
8.1 This method covers the determination of total carbon in
R
obtained on the same material using the same method in
nuclear-grade boron carbide in either powder or pellet form.
different laboratories.
9. Summary of Test Method
3.2.21 sample—a portion of a material selected and pro-
9.1 The sample and added combustion accelerators
cessed to render its composition representative of the compo-
(mostly tungsten-and iron-granules) are heated in an inductive
sition of the whole.
furnace under oxygen atmosphere.The high-frequency field of
3.2.22 sensitivity—the change of instrument response with
thefurnacecoupleswithelectricallyconductivecomponentsof
change in analyte concentration.
sample and combustion accelerators. The sample is heated to
3.2.23 standardization—the experimental establishment of
temperatures not lower than 1400°C and the total carbon
the concentration of a reagent solution.
content of the sample is released as carbon dioxide and,
partially, as carbon monoxide. The reaction gas is passed
3.2.24 TIMS—thermal ionization mass spectrometry.
through a gas-treatment train to ensure that any carbon
4. Significance and Use
Reagent Chemicals, American Chemical Society Specifications, American
4.1 Boron carbide is used as a control material in nuclear
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
reactors. In order to be suitable for this purpose, the material
listed by the American Chemical Society, see Analar Standards for Laboratory
must meet certain criteria for assay, isotopic composition, and
Chemicals,BDHLtd.,Poole,Dorset,U.K.andtheUnitedStatesPharmacopeiaand
impuritycontent.Thesemethodsaredesignedtoshowwhether NationalFormulary,U.S.PharmacopeialConvention,Inc.(USPC),Rockville,MD.
C791 − 19
monoxideformedisconvertedtocarbondioxideandtoremove at (110 6 5)°C to constant weight.The sample is cooled down
dust and moisture. The reaction gas is then transferred to the to ambient temperature in a desiccator and stored therein.
infrared absorption cell of the analyzer.The molecular absorp-
NOTE 3—Drying for2his normally sufficient.
tion of carbon dioxide is measured by using a narrow-band
13.2 Thesamplematerialmusthaveaparticlesizeof ≤150
optical filter which is translucent for the wavelength of the
µm (No. 100 sieve). Inhomogeneous sample material has to be
characteristic infrared absorption of carbon dioxide. The mass
homogenized.Standardapparatusandproceduresforcrushing,
fraction of carbon dioxide in the reaction gas is proportional to
milling and homogenization may be used provided that no
area of the transient absorption signal. The mass fraction of
contamination occurs which lessens the accuracy of the deter-
carbon in the sample is calculated by using a calibration
mination.
functionestablishedbysuitablecalibrationstandardsmeasured
under comparable conditions.
14. Calibration
10. Interferences
14.1 The calibration has to be performed daily according
10.1 At the specification limits usually established for to the manufacturer’s instructions. It has to be ensured that the
mass of carbon in the calibration sample (12.1.3) and test
nuclear-grade boron carbide, interferences are insignificant.
sample are within the same order of magnitude.
11. Apparatus
NOTE 4—This is achieved by choosing a suitable calibration sub-
11.1 Commonly used laboratory equipment and special
stance and adapted weights.
equipment according to the following:
14.2 The calibration has to be done according to Section
11.1.1 Carbonanalyzer,withinductionfurnaceandinfrared
15.
absorption cell, suitable to correctly determine the mass
fraction of carbon within the concentration range given by
15. Procedure
boron carbide.
15.1 Preparation of Analysis—Ceramic crucibles (11.1.3)
NOTE 1—The correctness of the analysis result can be proved by using
and crucible lids (11.1.4) have to be cleaned prior to use by
matrix analogous reference materials or by comparing with an indepen-
firing in a muffle furnace at 1200°C for 1 h. After that, they
dent alternative test method.
have to be stored in a desiccator.
11.1.2 Analytical balance, capable of reading to the near-
15.2 DeterminationofBlankValue(MethodBlank)—The
est 0.01 mg.
same procedure according to 15.4 has to be applied, however
11.1.3 Ceramic crucible, for example, mullite or alumina.
without addition of boron carbide.At least three blanks should
11.1.4 Crucible lid with hole, for example, mullite or
be determined at least once in each 8-h shift in which total
alumina.
carbon analyses are made.
12. Reagents
15.3 Conditioning of Carbon Analyzer—Prior to making
12.1 Reagents of known analytical grade shall be used, the initial analysis, condition the carbon analyzer by perform-
provided it is first ascertained that the reagent is of sufficiently ingatleasttwoanalysisruns.Thesameprocedureaccordingto
high purity to permit its use without lessening the accuracy of section 15.4 has to be applied, however only adding a small
the determination. amount of boron carbide (that is, a spatula-tip of boron
12.1.1 Tungsten granules. carbide).
15.4 Determination of Carbon Content—A sub-sample of
NOTE 2—Depending on the particle size of the material the decompo-
sitionofthesampleinthefurnacemaybeimprovedbypartiallyreplacing 20 to 30 mg of boron carbide powder prepared in accordance
tungstengranulesbytingranules.Tungsten/tin-mixturesarecommercially
to Section 12 is weighed to the nearest 0.01mg into the
available.
ceramic crucibles (11.1.3) cleaned according to section 15.1.
12.1.2 Iron granules.
NOTE 5—Using modern carbon analysis devices with an automated
12.1.3 Calibrationandcontrolsamples,withdefinedcarbon
calculation of the mass fraction of carbon in the sub sample the sample
content, preferably certified reference materials with composi-
mass has to be entered using the internal or external keyboard. Using
tion and carbon content similar to the analyzed material. Also
carbonanalysisdeviceswhichmeasuretheabsolutemassofcarbonofthe
sample the sample mass has to be noted for later calculations.
suitable are primary substances preferably carbonates (for
example,calciumcarbonate,CaCO ).Whencertifiedreference
The sample in the crucible is covered with approximately
materials are not available, consider Guide C1128 for prepa-
0.9 g and 1.8 g of iron and tungsten granules (12.1.1 and
ration of working reference materials.
12.1.2), respectively. For mixing, the crucible has to be shaken
12.1.4 Oxygen, purity ≥ 99.998% v/v.
carefully. Afterwards, the crucible is closed with the lid
12.1.5 Pneumatic gas, for example, nitrogen, purity
(11.1.4), placed into the induction furnace and the combus-
≥99.9% v⁄v.
tion cycle is started. Using modern carbon analysis devices the
carbon content is calculated and displayed on the internal or
13. Sampling and Sample Preparation
external screen or printed out.
13.1 Sampling has to be performed in a way that the To ensure correctness of results and to detect measurement
sample to be analyzed is representative for the total amount of drift a control sample (12.1.3) shall be measured within and at
material.Inanunknowndryingstatethesamplehastobedried the end of the measurement series.
C791 − 19
Each sample has to be analyzed at least two times. If the
m = absolute mass of carbon in the blank sample, mg,
blank
singlevaluesofthedouble-testaredeviatingmorethanagiven
and
degree, depending on the repeatability of the method, then the
m = sample mass, mg
s
analysis has to be repeated according to Section 15.If NOTE 6—Most state of the art analyzers automatically calculate the
mass fraction of carbon for each measurement after input of blank values
necessary, the sample has to be homogenized according to
and sample masses.
Section 13.
17. Precision and Bias (1)
16. Calculation
NOTE7—PleaseseeRef (2)forallprecisionandbiasstatements,except
16.1 The carbon content w(C ) of the sample has to be
total those denoted by Ref (3).
calculated under consideration of sample mass and blank
17.1 Within the frame of the certification of the boron
values. The carbon content as mean of the single values of the
carbide powder European reference material ERM-ED102,
multiple determinations shall be expressed in mass fractions in
the following precision and bias data were obtained applying
% and rounded off in accordance to the uncertainty of
the described total carbon method. (See table below.)
measurement.
Calculate the mass fraction of carbon as follows:
The boldface numbers in parentheses refer to the list of references appended to
m 2 m 3100
~ !
c blank these methods.
w C 5 (1)
~ !
total 5
m ERM-ED102 is a trade name of products supplied by BAM Federal Institute
s
for Materials Research and Testing, Berlin, Germany. This information is given for
where:
the convenience of users of this ASTM Standard and does not constitute an
endorsement byASTM of the products named. Equivalent products may be used if
m = absolute mass of carbon in the sample, mg,
c
they can be shown to lead to the same results.
Element Total Carbon ERM-ED102, Bias of mean of total
Method certified value carbon method to
Mean, Repeatability S , Reproducibility Mean, Uncertainty, certified value,
r
% % S , % % % (relative)
R
%
C 21.06 0.07 0.25 21.01 0.28 +0.24
TOTAL BORON BY TITRIMETRY AND ICP OES ferences) and non spectral interferences are critical. Non-
spectral interferences are caused primarily by different chemi-
18. Scope
cal composition of calibration solution and sample solution,
resulting in an alteration of nebulization and excitation prop-
18.1 This method covers the determination of total boron
erties. Also, memory-effects can play a role. The best way to
in samples of boron carbide powder and pellets by titrimetry
minimize non-spectral interferences is the use of calibration
and ICP OES.
samples with the same composition of matrix, ideally certified
19. Summary of Method
reference materials.
19.1 Powdered boron carbide is mixed with alkaline re-
21. Apparatus
agents and this mixture is fused to decompose the boron
carbide.The melt is dissolved in diluted hydrochloric acid and
21.1 Commonly used laboratory equipment and special
heated or purged with nitrogen to remove carbon dioxide. The
equipment according to the following:
boron as boric acid is titrated with standardized sodium
21.1.1 Balance, analytical, capable of reading to the near-
hydroxide solution, using the mannitoboric acid procedure (3),
est 0.01 mg.
(4), and (5).Alternatively, the boron in the samples solution is
21.1.2 Burner, Bunsen type.
measured using ICP OES.
21.1.3 Hand torch, with gas-cartridge.
NOTE 8—Sodium carbonate or a mixture of sodium carbonate and
21.1.4 Filter Paper, open-textured, very rapid filtering, for
potassium carbonate (1:1) is normally used as alkaline reagent to
coarse and gelatinous precipitates.
decompose the boron carbide.
21.1.5 Muffle Furnace, with temperature programmer and
20. Interferences
controllable to 620°C between 700°C and 900°C.
20.1 Titrimetry—Metallic impurities in high concentrations 21.1.6 pH Meter.
may distort the inflection points of the titration and should be
21.1.7 PlatinumCrucible,30-mL,standardformwithclose-
precipitated from the sample solution using barium carbonate.
fitting cover.
NodistortionwasfoundforconcentrationsofAl<0.2%,Fe<
21.1.8 Glassvolumetricpipet,50mL,ClassA,accordingto
2%, Ti < 1%. Interferences by dissolved CO shall be
2 Specification E969.
removed by heating the sample solution or by purging the
21.1.9 Titration system, consisting of:
sample solution with nitrogen.
(1)pH-electrode
20.2 ICP OES—Interference effects depend primarily upon (2)dosage apparatus for liquids with a resolution of 10 µL
theresolvingpowerofthespectrometerandtheselectionofthe (3)stirrer
analytical lines. In practice, line interferences (spectral inter- (4)unit for recording the titration curve
C791 − 19
21.1.10 Sequential or Simultaneous Optical Emission Spec- 25. Procedure
trometer with Inductively Coupled Plasma, suited to measure
25.1 Preparation of Analysis—A sub-sample of 100 mg of
in a wavelength region of 180 nm to 400 nm, preferably with
boron carbide powder prepared in accordance to Section 24 is
freely definable background measuring points.
weighed to the nearest 0.01 mg into the platinum crucible and
mixed with approximately3gNa CO /K CO using a mi-
2 3 2 3
22. Reagents
crospatula. The mixture is covered with approximately 2 g
22.1 Water complying Grade II of Specification D1193 Na CO /K CO and the platinum lid is placed on the crucible.
2 3 2 3
Continue with fusion procedures 25.2 or 25.3.
andreagentsofknownanalyticalgradeshallbeused,provided
it is first ascertained that the reagent is of sufficiently high
NOTE 10—Instead of sodium/potassium carbonate mixture, sodium
purity to permit its use without lessening the accuracy of the
carbonate can also be used for boron carbide decomposition.
determination. Store reagents in plastic containers.
25.2 Muffle furnace/Bunsen burner fusion procedure:
22.1.1 Barium Carbonate, BaCO .
25.2.1 Using Na CO /K CO —Put the crucible in the
2 3 2 3
22.1.2 Hydrochloric Acid, HCl, concentrated (sp gr 1.19),
muffle furnace. Heat the furnace to 750°C in 2 h and hold this
c(HCl) approximately 10 mol/L.
temperature for 4 h. Remove the crucible and let it cool to
22.1.3 HydrochloricAcid,HCl,1:1,c(HCl)approximately5
room temperature.
mol/L.
25.2.2 Using Na CO —Put the crucible in the muffle fur-
2 3
22.1.4 Mannitol, C H O , or Mannitol Solution, with a
6 14 6
nace. Heat the furnace to 600°C in 1 h and then to 750°C in 1
concentration of 100 g/L.
h and then to 900°C in 1.5 h. Hold this temperature for 0.5 h.
22.1.5 pH Buffer Solutions, for example, with a pH of 4.0,
Remove the crucible and let it cool to room temperature.
7.0, 9.0.
25.2.3 Add 20 mg to 30 mg of KNO and heat the closed
22.1.6 PrimarySubstancesforDeterminationofMolarityof
crucible with a full Bunsen flame until a clear melt is obtained
NaOH Solution, for example, potassiumhydrogenphthalate,
(approximately 2 min). Simultaneously heat the upper part of
C H KO , or boric acid, H BO , (NBS SRM 951 or its
8 5 4 3 3
crucible and lid with the full flame of a hand torch.Allow the
replacement).
melt to cool down to room temperature. If a clear melt is not
22.1.7 Potassium Nitrate, KNO .
obtained, repeat procedure 25.2.3. Continue with 25.4.
22.1.8 Sodium Carbonate, Na CO , dried at 200°C for 1 h.
2 3
25.3 Bunsen Burner Fusion Procedure—If this fusion tech-
22.1.9 Sodium/Potassium Carbonate Mixture, Na CO /
2 3
nique is used, KNO is not needed. Place a lid on the crucible
K CO 1:1 m/m, dried at 200°C for 1 h.
2 3
and heat with a low flame of a Bunsen burner for 15 min.
22.1.10 Sodium Hydroxide Solution, NaOH, c(NaOH) = 0.1
Continueheatingforanother75minwhilegraduallyincreasing
mol/L. This solution must be carbonate-free.
the temperature of the flame until the mixture is completely
22.1.11 Sodium Hydroxide Solution, NaOH, with a concen-
molten. Continue heating with a full Bunsen flame until
tration of 200 g/L.
decomposition of the boron carbide is completed. Most
22.1.12 Nitrogen, purity ≥ 99.99% v/v.
samples require heating with a full Bunsen flame for about 20
min for complete decomposition. Simultaneously heat the
23. Precautions
upper part of crucible and lid with the full flame of a hand
23.1 Consideration should be given to boron contamina-
torch. Allow the melt to cool to room temperature. Continue
tion that can come from reagents, glassware, and perhaps from
with 25.4.
other sources. If care is used in procuring reagents and if
NOTE 11—Procedure 25.3 works with both Na CO /K CO and
2 3 2 3
low-boron glassware is used, boron contamination should be
Na CO .
2 3
negligible. The periodic determination of a blank to check for
If fusion procedures 25.2 and 25.3 are applied to very fine
boron contamination is advisable, particularly whenever a new
grained (sub-micron) boron carbide powders lower results for
bottle of any reagent is used.
total boron may be obtained. If this is the case, instead of
procedures 25.2 and 25.3 the following modified Bunsen
24. Sampling and Sample Preparation
burner procedure has to be applied:
24.1 Sampling has to be performed in a way that the
Use Na CO /K CO for sample decomposition. Heat the
2 3 2 3
sample to be analyzed is representative for the total amount of
mixtureintheplatinumcruciblecarefullywithalowflamejust
material.Inanunknowndryingstatethesamplehastobedried
above the melting point of Na CO /K CO and hold this
2 3 2 3
at (110 6 5)°C to constant weight.The sample is cooled down
temperature until, after a few minutes, a clear melt is obtained.
to ambient temperature in a desiccator and stored therein.
Continue with section 25.4.
NOTE 9—Drying for2his normally sufficient.
25.4 Dissolution Procedure—Place crucible and lid in a
The sample material must have a particle size of ≤150 µm beaker. Add 50 mL of hydrochloric acid (22.1.3). Swirl the
(No. 100 sieve). Inhomogeneous sample material has to be beaker carefully to ensure that the whole surface of crucible
homogenized.Standardapparatusandproceduresforcrushing, and lid is wetted. To accelerate the leaching procedure the
milling and homogenization may be used provided that no solution may be gently heated. To avoid losses of boric acid,
contamination occurs which lessens the accuracy of the deter- the beaker must be covered with a watch-glass.After the melt
mination. is completely dissolved, rinse the watch-glass with water into
C791 − 19
thebeaker.Removecrucibleandlidfromthebeaker;rinseboth then the analysis has to be repeated according to Sections 25
carefully with water, adding the rinses to the beaker. Transfer and 26. If necessary, the sample has to be homogenized
the solution in the beaker to a 250 mL volumetric flask and according to Section 24. The method blank has to be deter-
rinse the beaker thoroughly with water into the volumetric minedapplyingthesameprocedureasdescribedinSections25
flask.Afterthis,thevolumetricflaskisfilleduptovolumewith and 26 (without and with barium carbonate precipitation),
water. This solution is used for titrimetric (Section 26) deter- however, without addition of boron carbide. If a measurable
mination of boron or, if metallic impurities in high concentra- methodblankisdetectedthesinglevalueshavetobecorrected
tions are present in the solution (Section 20), for barium by the method blank.
carbonate precipitation (25.5). The solution can directly be
26.3 Example of Boron Titration via Mannitoboric Acid:
used for ICP OES determination of boron (Section 27).
(See Fig. 1.)
25.5 Barium Carbonate Separation—Pipet a 50 mL aliquot 26.3.1 The titration curve on the left shows the
(21.1.8)ofthesamplesolutionobtainedbyprocedure25.4into pretitration, starting at pH 2.75. The first inflection point is at
a beaker. To ensure reproducible starting conditions and to pH 5.76. The titration is continued to pH 8.50. After that,
reducetheconsumptionofbariumcarbonatethesolutioninthe mannitolisadded.AfterwaitinguntilthepHhasstabilized(pH
beaker is neutralized with NaOH solution (22.1.11) using a pH 5.65)themain-titrationisstarted.Thesecondinflectionpointis
meter. Add 1.5 mL of hydrochloric acid (22.1.2). Stir the at pH 8.45. The consumption of 0.1 mol/LNaOH between the
solution and add barium carbonate until an excess of barium two inflection points corresponds to the mass of boric acid,
carbonate is visible. Cover the beaker with a watch-glass and respectively boron.
bring to a boil for 5 min. Let the precipitate digest for 30 min
26.4 Calibration:
at 50°C to 60°C (for example, using a sand-bath). Allow the
26.4.1 Before a measurement series the pH calibration of
suspension to cool down to room temperature. Rinse the
the titration system has to be performed according to the
watch-glasswithwaterintothebeaker.Separatetheprecipitate
manufacturer’s instructions using pH buffer solutions (22.1.5).
by filtration through an open-textured filter paper and collect
For the NaOH solution used for titration the correct molarity
the filtrate in a beaker. Rinse the filter paper and precipitate
has to be determined. For this purpose, preferably solutions of
thoroughly four to six times with water and collect the rinses
primary substances, for example, potassiumhydrogenphthalate
with the filtrate. Set the pH to 2.5 to 3 with hydrochloric acid
orboricacid(22.1.6),mustbetitratedwiththeNaOHsolution.
(22.1.3) and bring to a boil for 2 min (or purge with nitrogen
The method for total boron determination can be checked
for 10 min) to remove CO . Continue with section 26.2.
through analysis of certified boron carbide reference materials.
The bias to the certified boron content can be used to derive a
26. Titrimetric Determination of Boron
method correction factor which improves the accuracy of total
26.1 Preparation of Analysis: boron determination.
26.1.1 Pipet a 50 mL aliquot (21.1.8) of the sample
NOTE 13—See Annex A1 for commercial reference materials.
solution obtained by procedure 25.4 into a beaker. Fill up with
26.5 Calculation:
water to a volume of approximately 200 mL. Set the pH to 2.5
26.5.1 The total boron content w(B ) of the sample has
total
to 3 with hydrochloric acid (22.1.3) and bring to a boil for 2
to be calculated under consideration of sample mass and blank
min (or purge with nitrogen for 10 min) to remove CO .
values.Theboroncontentasmeanoftheblankcorrectedsingle
26.2 Titration:
values of the multiple determinations shall be expressed in
26.2.1 Usingthetitration-system,thesolutionistitratedto
mass fractions in % and rounded off in accordance to the
the first inflection point with 0.1 mol/LNaOH (22.1.10). Then
uncertainty of measurement.
35 mLof a mannitol-solution (22.1.4) or 4 g of solid mannitol
Calculate the mass fraction of boron as follows:
isaddedandfinallytitratedwith0.1mol/LNaOHtothesecond
V 3F 3V 3q 3100
NaOH S
inflectionpoint.Theconsumptionof0.1mol/LNaOHbetween
w B 5 (2)
~ !
total
V 3m
A E
the two inflection points corresponds to the mass of boric acid,
M
respectively boron (titration example see 26.3). To avoid
meas
F 5 (3)
interferences by CO the sample solution must be purged with M
nom
where:
nitrogen during titration.
NOTE 12—If the inflection point on the titration curve is distorted or
if there are multiple inflections that are severe enough to prevent a clear
V = consumption of 0.1 mol/L NaOH, mL,
NaOH
determination of the end point, carbonate or hydrolyzable metals are
V = volume of sample solution, mL,
S
probably present. The best procedure at this point is to start the analysis
V = volume of titrated aliquot, mL,
A
over with a new sample. The titrated solution can be salvaged, however,
F = titration correction factor for NaOH,
by adjusting the pH to 3.0 with dilute acid and then following the barium
M = measured molarity of NaOH used for titration,
meas
carbonate separation procedure (25.5). Once mannitol has been added at
mol/L,
26.2, the titrated solution can not be salvaged and a new sample must be
started. M = nominal molarity of NaOH used for titration,
nom
mol/L,
26.2.2 Each sample has to be analyzed at least two times.
q = titrimetric factor (see Note 14), and
If the single values of the double-test are deviating more than
m = sample mass, mg
E
a given degree, depending on the repeatability of the method,
C791 − 19
NOTE14—q=1.0811mgboronpermL0.1mol/LNaOHsolution,for
10 11
a natural B/ B isotopic ratio.
26.6 Precision and Bias—Within the frame of the certifi-
cation of the boron carbide powder European reference mate-
rial ERM-ED102, the following precision and bias data were
obtained applying the described titrimetric total boron method.
(See table below.)
Element Titrimetric total Boron Method ERM-ED102, Bias of mean of
certified value titrimetric total boron
Mean, Repeatability S , Reproducibility S , Mean, Uncertainty, method to certified value,
r R
% % % % % % (relative)
B 78.42 0.13 0.34 78.47 0.31 -0.06
NOTE 15—Calibration with more than two points is also possible.
27. ICP OES
Knownfromexperiencethis,however,leadsonlytoaminorimprovement
27.1 General Comments—The sample solution obtained in
of accuracy. For multi-point calibrations the zero-point should also not be
25.4 is analyzed for boron using ICP OES. The analysis of included in the calibration function.
sample solutions by ICP OES is well known and comprehen-
Calibration and control solutions shall be prepared using
sivelydescribedinnumerousstandardtestmethods.Therefore,
boron standard solutions (for example, 1000 mg/L), boric acid
a detailed description of the procedure for the analysis of the
or by decomposition of boron carbide certified reference
sample solution by ICP OES is not part of this standard test
materials. If boron solution or boric acid is used matrix-
method.Onlyinformationspecifictothedeterminationoftotal
matching with the solution described in 27.4 is required.
boron is given. A precise determination of main components
with ICPOES is challenging but possible. However, in routine NOTE 16—Assuming a total boron content around 78% m/m, prepara-
tion of the sample solution according to 27.2 and the use of a 1000 mg/L
analysis a lower precision compared to the titrimetric method
boron standard solution it is recommended to prepare the following
can be expected.
calibration and control solutions:
27.2 Preparation of Sample Solution—Assuming a total Calibration solution – low: pipet 10 mLof solution 27.4 and 1.0 mLof
boron standard solution into a 100 mL volumetric flask and fill up to
boron content of 78% m⁄m the sample solution obtained in
volume. Resulting boron concentration: 10 mg/L.
25.4 has a boron concentration of approximately 310 mg/L. In
Calibration solution – high: pipet 10 mLof solution 27.4 and 3.5 mL
addition, it has a quite high salt concentration of 20 g/L
of boron standard solution into a 100 mL volumetric flask and fill up to
Na CO /K CO or Na CO , respectively. It is therefore rec-
volume. Resulting boron concentration: 35 mg/L.
2 3 2 3 2 3
ommendedtodilutethesamplesolution,preferablybyafactor Control solution: pipet 10 mL of solution 27.4 and 3 mL of boron
standard solution into a 100 mL volumetric flask and fill up to volume.
often.Pipet10mLofthesolutionobtainedin25.4ina100mL
Resulting boron concentration: 30 mg/L.
volumetric flask. Fill up to volume with water.This solution is
then analyzed by ICP OES. 27.6 Procedure—The sample solution obtained in 27.2 is
used for measurement. To detect a measurement drift the
27.3 Recommended Wavelength—Recommended boron
controlsolutionhastobemeasuredwithinandattheendofthe
emission lines are: 182.591 nm, 208.959 nm, 249.677 nm,
measurement series. To improve the precision each sample
249.773 nm.
solution has to be measured repeatedly.
27.4 Matrix Solution—For preparation of calibration and
control solutions, the following matrix solution must be used: NOTE 17—For example: each sample solution of the measurement
series is measured with three replicates and the measurement series is
Weigh5gofNa CO /K CO or Na CO (depending on the
2 3 2 3 2 3
repeated three times.
matrix of solution 25.4) into a 250 mL volumetric flask. Add
NOTE 18—The precision can be improved if the measurement is
approximately 100 mL of water and 50 mL of hydrochloric
carried out using an internal standard.
acid (22.1.3) and wait until the carbonate has dissolved. Degas
Each sample has to be analyzed at least two times. If the
the solution in an ultrasonic bath and fill up to volume with
singlevaluesofthedouble-testaredeviatingmorethanagiven
water.
degree, depending on the repeatability of the method, then the
27.5 Calibration—Calibration of the ICP OES has to be
analysis has to be repeated according to Sections 25 and 27.If
performed before a measurement series according to the
necessary, the sample has to be homogenized according to
manufacturer’s instructions. To achieve a high precision of the
Section 24. The method blank has to be determined applying
measurementa2-pointcalibrationwithoutzero-pointhastobe
the same procedures as described in Sections 25 and 27,
applied (so called “bracket calibration”). Normally, the boron
however, without addition of boron carbide. If a measurable
concentrations of the calibration solutions are selected in a
methodblankisdetected,thesinglevalueshavetobecorrected
manner that one is above, but nearby, and the second one is
by the method blank.
belowtheexpectedboronconcentrationofthesamplesolution.
To control the calibration a control solution with a boron 27.7 Calculation—The total boron content w(B ) of the
total
concentration between both standard solutions is required.The sample has to be calculated under consideration of sample
controlsolutionisalsousedtodetectmeasurementdriftduring mass, dilution factor and blank values. The boron content as
a measurement series. mean of the blank corrected single values of the multiple
C791 − 19
determinations shall be expressed in mass fractions in % and
f = dilution factor (see 27.2), and
rounded off in accordance to the uncertainty of measurement.
m = sample mass, mg
E
Calculate the mass fraction of boron as follows:
28. Precision and Bias
C 3f 3V
M S
w B 5 (4)
~ !
total
10 3m
E
28.1 Within the frame of the certification of the boron
where: carbide powder European reference material ERM-ED102, the
following precision and bias data were obtained applying the
C = measured boron concentration in sample solution
M
described ICP OES total boron Method. (See table below.)
(27.2), corrected by blank value, mg/L,
V = volume of solution after sample decomposition (25.4),
S
mL,
Element ICP OES total Boron Method ERM-ED102, Bias of mean of ICP OES
certified value total boron method to
Mean, Repeatability S , Reproducibility S , Mean, Uncertainty, certified value,
r R
% % % % % % (relative)
B 78.70 0.61 0.63 78.47 0.31 +0.29
ISOTOPIC COMPOSITION BY MASS 32.1.1.1 Source,thermalionizationusingsinglefilaments.A
SPECTROMETRY vacuum lock is recommended to maintain source vacuum,
which increases sample throughput.
32.1.1.2 Analyzer,withavacuumsystemcapableofproduc-
29. Scope
ing a resolving power of at least 400 and an abundance
29.1 This method covers the determination of the isotopic
sensitivity at mass 100 of at least 20000. Resolving power is
composition of boron in nuclear-grade boron carbide, in
definedasM/∆M,where ∆Misthewidth,inatomicmassunits,
powder and pellet form, containing natural to highly enriched
ofapeakatmassMat5%ofitsheight.Abundancesensitivity
boron.
is defined as the ratio of total ion current at mass M to its
contribution at mass M-1.
30. Summary of Method
32.1.1.3 Detector, Faraday Cup, Electron Multiplier, or
30.1 Boronisotopicratiosaremeasuredinboroncarbideby Scintillator Photomultiplier—Data acquisition can be accom-
thermal ionization mass spectrometry (TIMS) without prior plished by a potentiometric recorder or a pulse counting
chemical separation of boron. Boron is converted to sodium system.
boratebyfusionoftheboroncarbidewithsodiumhydroxideor 32.1.2 Mass Spectrometer Accessories—The following
sodiumcarbonatedirectlyonthetantalumfilamentofthemass items are required:
spectrometer. The loaded filament is transferred to the mass 32.1.2.1 Filaments, tantalum ribbon, nominally 0.25 m
spectrometer where boron isotopic ratios are measured using (0.001 in). thick, 0.75 mm (0.030 in.) wide, with optional
+
the Na BO ion. When mixing the boron carbide and sodium V-groove.Filamentsshouldbepreparedandstoredinamanner
2 2
hydroxide or sodium carbonate, a Na to B ratio of 1:1 is to minimize contamination, and they should be cleaned before
maintained, which gives a stable ion emission within a few use.
minutes after operational vacuum is attained. There is no 32.1.2.2 Forming Jig, used to form filaments into the
apparent bias caused by selective volatilization of B (6), (7), configuration required by the mass spectrometer used and to
(8), (9), (10), (11).
hold the filaments in place for welding.
32.1.2.3 Spot Welder, used to weld the filament ribbons to
As an alternative method, the boron isotopic ratios are
the support posts. Welds should be made carefully to ensure
measured in boron carbide by ICP-MS.
good electrical contact, which is necessary for beam stability.
32.1.2.4 Sample-Loading Unit, used to heat filaments to at
31. Interferences
least 800°C. A system permitting an electrical current to pass
31.1 Impurity elements, at the specification limits usually
through the filament is required.
established for nuclear-grade boron carbide, do not interfere.
32.1.3 Mixer Mill.
Strontium is a potential interference and it is an impurity 7
32.1.4 PlasticPipet,5-µL,withachangeableplasticbarrel.
element in the tantalum filament material. At the temperature
Use a pipet tip only once and then discard it.
used to ionize sodium borate, however, the strontium impurity
32.1.5 Plastic Vial and Ball—12.7-mm (0.5-in.) outside
in the filament does not volatilize to cause a high bias at mass
diameterby25.4-mm(1-in.)longvialand9.52-mm(0.375-in.)
88. This potential interference does not occur in ICP-MS.
diameter ball.
32.2 Reagents:
32. Isotopic Composition by TIMS
32.1 Apparatus:
A Spex Industries mixer mill, Model 5100, has been used for this method.
32.1.1 Mass Spectrometer—Commercial instruments are
AKimble automatic pipet, No. 56300, with disposable polypropylene tips has
available that meet or exceed the following requirements: been used for this method.
C791 − 19
32.2.1 Acetone. 32.5.2.9 Transfer about 5 µL of the slurry to a filament.
32.2.2 Water, complying Grade II of Specification D1193. Proceed to 32.5.2.10 for the fusion.
32.5.2.10 Heatthefilamentgraduallyjusttothepointwhere
32.2.3 Isopropyl Alcohol.
the filament glows brightly.
32.2.4 Sodium Carbonate (Na CO ) Solution, 0.14 M.
2 3
32.2.5 Sodium Hydroxide (NaOH)—Pulverize in stainless
NOTE 20—The bright glow is caused by the exothermic reaction of
steel containers with stainless steel balls in a mixer mill and
tantalum with NaOH or Na CO . The fusion produces sodium borate and
2 3
the melt tightly adheres to the filament.
store in a desiccator.
32.2.6 Toluene.
32.5.3 Mass Spectrometric Measurement:
32.5.3.1 Insert the filament assembly into the mass spec-
32.3 Precautions—Consideration should be given to boron
trometer.
contamination from reagents and other sources. Sources of
−7
32.5.3.2 Evacuate the system to about 66 µPa (5×10
natural boron contamination can be checked by using NBS
torr).
B-enriched boric acid (SRM 952 or alternate) as an internal
32.5.3.3 Heat the sample by passing an electrical current
standard (8).
+
through the filament until a stable beam of Na BO ions is
2 2
32.4 Calibration—Periodicattentionshouldbegiventobias
obtained.
and linearity and to counting dead time when an ion-counting
32.5.3.4 Scan the spectrum repeatedly in both directions
technique is used. These factors should be determined when
over the mass range desired until at least nine spectra have
the mass spectrometer is first used and they should be checked
been obtained.
whenever a calibration result is obtained that significantly
32.6 Calculation—Determine the boron isotopic composi-
deviates from the accepted value. These factors should also be
tion from the mass spectra recorded. Calculate the 89 to 88
checked at intervals of not greater than three months.
peak height ratio from the average peak heights. Subtract
32.5 Procedure:
0.00078tocorrectfor O.Thencorrecttheratioformassbias.
32.5.1 Filament Cleaning—Filament assemblies are made
32.7 Precision and Accuracy:
in accordance with a procedure that is appropriate for the mass
32.7.1 Precision—For the B-10 isotope, the relative stan-
spectrometer used.
dard deviation is 0.22atom % at a concentration in the boron
32.5.1.1 Clean the filament assembly by sequentially dip-
of 20 atom percent.
ping it in toluene, isopropyl alcohol, and water.
32.7.2 Bias—The average percent recovery obtained from
32.5.1.2 Rinse the assembly twice with acetone.
10 analyses of boron carbide control standards over a two-year
32.5.1.3 Dry the assembly under a heat lamp.
period was 100.1%. Those standards were prepared and
32.5.2 Filament Loading—Steps 32.5.2.1 – 32.5.2.5 are
certified by LASL (2).
instructions for fusing the sample with NaOH and 32.5.2.6 –
32.5.2.9areinstructionsforanalternativefusionwithNa CO . 33. Isotopic Composition by ICP MS
2 3
32.5.2.1 Weigh 25 6 2 mg of sample in powder form and
33.1 General Comments—The determination of isotopic
transfer it to a plastic vial.To obtain a representative sample if
ratios by ICP-MS is nowadays a well known state-of-the-art
the original sample is in powdere
...