ASTM D4517-04(2009)
(Test Method)Standard Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectroscopy
Standard Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectroscopy
SIGNIFICANCE AND USE
Control of silica in boiler feedwater and boiler water is necessary to minimize the formation of scale-forming silicates that decrease heat transfer in the boiler. Volatilization and carryover of silica with the steam may cause hard, glassy siliceous deposits to form on turbine blades that reduce turbine efficiency.
Colloidal silica that is not removed by boiler water pretreatment processes may be solubilized in the boiler and thus contribute to the dissolved silica concentration in the boiler. Both dissolved and total silica are of interest.
SCOPE
1.1 This test method covers the determination of total silica in water.
1.2 This test method is applicable in the range from 25 to 250 μg/L of silica as SiO2. Higher concentrations may be determined by decreasing the aliquot volume (see Note 6). Concentration range should not be extended by dilution.
1.3 This test method determines total silica, and does not distinguish between soluble and insoluble forms.
1.4 This test method was tested on reagent water only. It is the user's responsibility to assure the validity of the test method for waters of other matrices.
1.5 This standard does not purport to address 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.
General Information
Relations
Buy Standard
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D4517 − 04(Reapproved 2009)
Standard Test Method for
Low-Level Total Silica in High-Purity Water by Flameless
Atomic Absorption Spectroscopy
This standard is issued under the fixed designation D4517; 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 D3919 Practice for Measuring Trace Elements in Water by
Graphite Furnace Atomic Absorption Spectrophotometry
1.1 This test method covers the determination of total silica
D4453 Practice for Handling of High Purity Water Samples
in water.
D5810 Guide for Spiking into Aqueous Samples
1.2 This test method is applicable in the range from 25 to
D5847 Practice for Writing Quality Control Specifications
250 µg/L of silica as SiO . Higher concentrations may be
for Standard Test Methods for Water Analysis
determined by decreasing the aliquot volume (see Note 6).
Concentration range should not be extended by dilution. 3. Terminology
1.3 This test method determines total silica, and does not 3.1 Definitions—For definitions of terms used in this test
method, refer to Terminology D1129.
distinguish between soluble and insoluble forms.
1.4 This test method was tested on reagent water only. It is
4. Summary of Test Method
the user’s responsibility to assure the validity of the test
4.1 Total silica is determined using an atomic absorption
method for waters of other matrices.
spectrophotometer in conjunction with a graphite furnace. A
1.5 This standard does not purport to address the safety
sample is placed in a graphite tube, evaporated to dryness,
concerns, if any, associated with its use. It is the responsibility
charred, and atomized. Since the graphite furnace uses the
of the user of this standard to establish appropriate safety and
sample much more efficiently than flame atomization, the
health practices and determine the applicability of regulatory
detection of low concentrations of elements in small sample
limitations prior to use.
volumes is possible. Finally, the absorption signal during
atomization is recorded and compared to standards. A general
2. Referenced Documents
guide for the application of the graphite furnace is given in
2.1 ASTM Standards:
Practice D3919. Pretreatment of the graphite tube may be used
D859 Test Method for Silica in Water
toenhancethesensitivityandrepeatability,orboth,ofthetest.
D1066 Practice for Sampling Steam
4.2 Total silica is determined using a freshly ultrasonically
D1129 Terminology Relating to Water
treated and shaken aliquot of sample.
D1192 Guide for Equipment for Sampling Water and Steam
4.3 This test method determines low-level total silica in
in Closed Conduits (Withdrawn 2003)
high purity water. Refer to Test Method D859, Method B, for
D1193 Specification for Reagent Water
determination of molybdate-reactive silica.
D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
5. Significance and Use
D3370 Practices for Sampling Water from Closed Conduits
5.1 Control of silica in boiler feedwater and boiler water is
necessary to minimize the formation of scale-forming silicates
This test method is under the jurisdiction of ASTM Committee D19 on Water
that decrease heat transfer in the boiler. Volatilization and
and is the direct responsibility of Subcommittee D19.03 on Sampling Water and
carryover of silica with the steam may cause hard, glassy
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use,
siliceous deposits to form on turbine blades that reduce turbine
On-Line Water Analysis, and Surveillance of Water.
Current edition approved Oct. 1, 2009. Published November 2009. Originally
efficiency.
approved in 1985. Last previous edition approved in 2004 as D4517 – 04. DOI:
5.2 Colloidal silica that is not removed by boiler water
10.1520/D4517-04R09.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
pretreatment processes may be solubilized in the boiler and
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Rawa, JudithA. and Earl L. Henn, “Determination of Trace Silica in Industrial
The last approved version of this historical standard is referenced on Process Waters by Flameless Atomic Absorption Spectrometry,” Analytical
www.astm.org. Chemistry, Vol 51, March 1979.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4517 − 04 (2009)
thus contribute to the dissolved silica concentration in the 7.5 Pipets:
boiler. Both dissolved and total silica are of interest. 7.5.1 Microlitre, with disposable, polypropylene tips. Sizes
may range from 1 to 1000 µL, as required.
6. Interferences 7.5.2 Millilitre, 50.0 mL.
7.6 Data System—Fast transient signal data are collected
6.1 For a complete discussion of general interferences with
furnace procedures, the analyst is referred to Practice D3919. and processed using an internal microprocessor or external
desktop computer systems. Data can be stored on disks,
6.2 Relatively pure waters such as demineralizer effluent,
transmitted to central servers, or printed in hard copy. Data
condensate, or high-pressure boiler feedwater are of sufficient
may be evaluated and processed using the instrument’s dedi-
purity to minimize potential interferences such as sodium,
cated systems to determine analyte concentrations. Users of
orthophosphate, or sulfate.
thispracticemayuseastripchartrecordertoobtainsampleand
6.3 Graphite tube pretreatment with the calcium/lanthanum
calibration data, if desired.
reagent has been found to improve the silica response with
7.7 Ultrasonic Cleaner, operable at >20 KHz.
some graphite tube materials or designs. Since response
7.8 Flasks, volumetric, 100 and 1000-mL polyethylene.
problems may include memory effects as well as poor sensi-
tivity, the following procedure must be used to determine
8. Reagents and Materials
whether pretreatment is needed.
6.3.1 Following instrument set-up and blank determination
8.1 Purity of Reagents—Reagent grade chemicals shall be
as described in 10.1-10.3, inject 10 to 12 replicates of a
used in all tests. Unless otherwise indicated, it is intended that
standard containing 100 to 150 µg/L of SiO . Treat the tube in
all reagents shall conform to the specifications of the Commit-
accordance with 6.4, and repeat. Note whether the response of
tee on Analytical Reagents of the American Chemical Society
the two sets is constant, indicating no memory effect, or
where such specifications are available. Other grades may be
whether the first set shows increasing response. Note also
used, provided it is first ascertained that the reagent is of
whether the response of the second set is greater than that of
sufficiently high purity to permit its use without lessening the
the first. If either sensitivity of repeatability is improved, tube
accuracy of the determination.
pretreatment is recommended.
8.2 Purity of Water—All references to reagent water in this
6.4 Pretreatment may be accomplished as follows:
methodshallbeunderstoodtoconformtoSpecificationD1193,
6.4.1 Inject into the furnace the diluted calcium/lanthanum
for reagent water Type II. In addition, the reagent water shall
reagent using the maximum aliquot recommended by the
be made silica-free and determined as such in accordance with
manufacturer of the tube, and start the atomization program.
this method. The collecting apparatus and storage containers
Repeat three times, or more if necessary. Run blank atomiza-
for the reagent water must be made of suitable materials that
tion cycles until the furnace blank is constant.
will not contaminate the reagent water with silica (see Section
6.4.2 Proceed to calibrate the furnace and analyze samples
9).
in accordance with Sections 10 and 11. The absorbance
NOTE 4—Silica-free water may be prepared by distillation, demineral-
enhancement may deteriorate after numerous injections, in
ization, and passage through a 0.22 µm filter. Total removal of colloidal
which case retreatment will be required. Refer to Practice
silica may be done by treating the above water with hydrofluoric acid,
D3919.
letting it stand for 24 h, and then processing it through strong base
ion-exchange resin in the hydroxide form.
7. Apparatus
8.3 Calcium/Lanthanum Reagent—Wet 2.90 g of lanthanum
oxide (La O 99.99 % pure) with about 50 mL of water in a
7.1 Atomic Absorption Spectrophotometer , for use at 251.6 2 3
100mLvolumetricflask.Carefullyadd5.5mLofconcentrated
nm.
nitric acid (HNO sp gr 1.42) and swirl to dissolve.Add 0.100
NOTE 1—Awavelength other than 251.6 nm may be used if it has been
g of calcium oxide (CaO) and swirl to dissolve. Dilute to
determined to be equally suitable.
volume with water. This solution contains 100 mg/L CaO and
NOTE 2—The manufacturer’s instructions should be followed for all
2500 mg/L La. Dilute 1:100 for injection. The diluted reagent
instrument parameters.
is needed only for pretreatment of the graphite tube as
7.2 Silicon Light Source, silicon hollow cathode lamp.
described in 6.4.
7.3 Graphite Furnace, capable of reaching temperatures
8.4 SilicaStockSolution(1mL = 1mgSiO )—Dissolve4.7
sufficient to atomize the element of interest. Atomization
g of sodium metasilicate (Na SiO ·9H O) and dilute to 1 L
2 3 2
temperature must be reached as rapidly as possible for maxi-
with water. Determine the silica concentration of this solution
mum sensitivity.
in accordance with Test Method D859, Method A.
NOTE 3—Special furnace accessories are commercially available to
provide a means of accelerating atomization temperature.
7.4 Graphite Tubes, compatible with furnace device. Stan-
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
dard graphite tubes are preferred, particularly when tube
listed by the American Chemical Society, see Analar Standards for Laboratory
pretreatment is practiced. Pyrolytic graphite tubes may be used
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
if it has been determined by the analyst that the precision, bias,
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
and sensitivity of the determination are not compromised. MD.
D4517 − 04 (2009)
8.5 Silica Working Solution (1 mL = 0.05 mg SiO )—Dilute 10.5 Inject a measured aliquot of the 100 µg/L of SiO
2 2
50.0 mLof the silica stock solution (see 8.4) to 1 Lwith water standard solution (see 10.1) into the furnace, and initiate the
inavolumetricflask.Theconcentrationofthisdilutedstandard present atomization program. Repeat this analysis until the
is calculated after confirming the concentration of the stock response reproduces within 10 %.
solution.
10.6 Determine the acceptability of the water by injecting a
8.6 Argon, standard, welder’s grade, commercially avail- measured aliquot of the “0” standard solution into the furnace
able. and initiating the preset atomization program. Repeat this
analysis until the response reproduces within 10 %.
9. Sampling
10.7 Inject a measured aliquot of each of the remaining
9.1 Collect the sample in accordance with the applicable
standard solutions as described in 10.5.
ASTM standards: Practice D1066, Specification D1192, and
10.8 Prepare a calibration curve by plotting absorbance or
Practices D3370.
peak height versus concentration as micrograms per litre of
9.2 Since silica is such a ubiquitous material, meticulous
SiO on linear paper if direct readout in terms of concentration
sample collection, handling, and injection into the furnace are
is not possible with the instrument.
necessary to avoid contamination.
11. Procedure
9.2.1 Collect samples only in plastic or TFE-fluorocarbon
containers. Polystyrene, polypropylene, linear polyethylene,
11.1 Rinse the microlitre pipet with water and inject an
and TFE-fluorocarbon have been found to be generally suit-
aliquot of water to test pipet and furnace cleanliness before
able,buttestsshouldbeconductedonsamplecontainersbefore
sample analysis.After samples containing a high concentration
use to determine their suitability.
of silica are analyzed, additional atomization cycles may be
9.2.2 Sample containers must be ultrasonically cleaned
needed to reduce the furnace blank to prior level.
before use. Fill the sample containers with water and immerse
11.2 Ultrasonicate for at least 1 min and then vigorously
in an operating ultrasonic cleaner for at least 1 min. Remove,
shake sample. Immediately withdraw an aliquot (refer to 10.3
shake vigorously, and drain.Additional cycles of cleaning may
and Note 6) with the microlitre pipet. Do not touch pipet tip to
be found necessary.
any object.
9.2.3 Before actual sample collection, rinse sample con-
11.3 Analyze sample as described in 10.2-10.4.
tainer with the sample it is to contain three times with vigorous
shaking, then fill. Do not allow any object to touch the inside
NOTE 8—If the total silica concentration of the sample is below the
of the bottle or cap.
detection limit with the normal maximum injection volume for the
instrument used, multiple injections may be used as follows. Inject an
aliquot, start program. Stop at completion of drying step. Repeat as
10. Calibration
required. Allow program to run to completion when enough sample has
10.1 Prepare standards for test calibration containing about
been injected. Both precision and bias will decrease when this technique
0, 50, 100, 150, and 250 µg/L of SiO by diluting 0, 100, 200, is used.
300, and 500 µLof the silica working solution (see 8.4)to100
12. Calculation
mL with water in separate volumetric flasks.
12.1 Sample concentration is read directly from calibration
NOTE 5—The exact concentration of the prepared silica standards is
curve prepared in 10.8. If multiple injections are used as
determined from the result obtained by the gravimetric standardization of
discussed in Note 8, divide the result by the number of
the stock solution in 8.4.
injections.
10.2 Zero the instrument without making an injection or
initiating an atomization program. 13. Precision and Bias
10.3 Set the atomization program (drying, charring, atom-
13.1 The single-operator and overall precision of this test
izing) according to the manufacturer’s instructions. method within its designated range for ten operators in six
differentlaboratoriesat251.6nmmaybeexpresseda
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
An American National Standard Designation: D4517 – 04 (Reapproved 2009)
Designation:D 4517 – 85 (Reapproved 1999)
Standard Test Method for
Low-Level Total Silica in High-Purity Water by Flameless
Atomic Absorption Spectroscopy
This standard is issued under the fixed designation D4517; 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
1.1 This test method covers the determination of total silica in water.
1.2 This test method is applicable in the range from 25 to 250 µg/Lof silica as SiO . Higher concentrations may be determined
by decreasing the aliquot volume (see Note 6). Concentration range should not be extended by dilution.
1.3 This test method determines total silica, and does not distinguish between soluble and insoluble forms.
1.4 This test method was tested on reagent water only. It is the user’s responsibility to assure the validity of the test method for
waters of other matrices.
1.5 This standard does not purport to address 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.
2. Referenced Documents
2.1 ASTM Standards:
D859 Test Method for Silica in Water
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1192 SpecificationGuide for Equipment for Sampling Water and Steam in Closed Conduits
D1193 Specification for Reagent Water Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Closed Conduits
D3919 Practice for Measuring Trace Elements in Water by Graphite Furnace Atomic Absorption Spectrophotometry
D4453Practice for Handling of Ultra-Pure Water Samples 4453 Practice for Handling of Ultra-Pure Water Samples
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
3. Terminology
3.1 Definitions: —ForFor definitions of terms used in this test method, refer to Terminology D 1129D1129.
4. Summary of Test Method
4.1 Total silica is determined using an atomic absorption spectrophotometer in conjunction with a graphite furnace. A sample
is placed in a graphite tube, evaporated to dryness, charred, and atomized. Since the graphite furnace uses the sample much more
efficiently than flame atomization, the detection of low concentrations of elements in small sample volumes is possible. Finally,
the absorption signal during atomization is recorded and compared to standards.Ageneral guide for the application of the graphite
furnace is given in Practice D 3919D3919. Pretreatment of the graphite tube may be used to enhance the sensitivity and
repeatability, or both, of the test.
This test method is under the jurisdiction ofASTM Committee D-19 D19 on Water and is the direct responsibility of Subcommittee D19.03 on Sampling of Water and
Water-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.
Current edition approved Aug. 30, 1985. Published October 1985.on Sampling Water and Water-Formed Deposits, Analysis of Water for Power Generation and Process
Use, On-Line Water Analysis, and Surveillance of Water.
Current edition approved Oct. 1, 2009. Published November 2009. Originally approved in 1985. Last previous edition approved in 2004 as D4517 – 04. DOI:
10.1520/D4517-04R09.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 11.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Rawa, Judith A. and Earl L. Henn, “Determination of Trace Silica in Industrial Process Waters by Flameless Atomic Absorption Spectrometry,” Analytical Chemistry,
Vol 51, March 1979.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4517–04 (2009)
4.2 Total silica is determined using a freshly ultrasonically treated and shaken aliquot of sample.
4.3 This test method determines low-level total silica in high purity water. Refer to Test Method D 859D859, Method B, for
determination of molybdate-reactive silica.
5. Significance and Use
5.1 Control of silica in boiler feedwater and boiler water is necessary to minimize the formation of scale-forming silicates
whichthat decrease heat transfer in the boiler.Volatilization and carryover of silica with the steam may cause hard, glassy siliceous
deposits to form on turbine blades whichthat reduce turbine efficiency.
5.2 Colloidal silica whichthat is not removed by boiler water pretreatment processes may be solubilized in the boiler and thus
contribute to the dissolved silica concentration in the boiler. Both dissolved and total silica are of interest.
6. Interferences
6.1 Foracompletediscussionofgeneralinterferenceswithfurnaceprocedures,theanalystisreferredtoPracticeD3919D3919.
6.2 Relatively pure waters such as demineralizer effluent, condensate, or high-pressure boiler feedwater are of sufficient purity
to minimize potential interferences such as sodium, orthophosphate, or sulfate.
6.3 Graphite tube pretreatment with the calcium/lanthanum reagent has been found to improve the silica response with some
graphite tube materials or designs. Since response problems may include memory effects as well as poor sensitivity, the following
procedure must be used to determine whether pretreatment is needed.
6.3.1 Following instrument set-up and blank determination as described in 10.1-10.3, inject 10 to 12 replicates of a standard
containing 100 to 150 µg/L of SiO . Treat the tube in accordance with 6.4, and repeat. Note whether the response of the two sets
is constant, indicating no memory effect, or whether the first set shows increasing response. Note also whether the response of the
second set is greater than that of the first. If either sensitivity of repeatability is improved, tube pretreatment is recommended.
6.4 Pretreatment may be accomplished as follows:
6.4.1 Inject into the furnace the diluted calcium/lanthanum reagent using the maximum aliquot recommended by the
manufacturerofthetube,andstarttheatomizationprogram.Repeatthreetimes,ormoreifnecessary.Runblankatomizationcycles
until the furnace blank is constant.
6.4.2 ProceedtocalibratethefurnaceandanalyzesamplesinaccordancewithSections10and11.Theabsorbanceenhancement
may deteriorate after numerous injections, in which case retreatment will be required. Refer to Practice D 3919D3919.
7. Apparatus
7.1 Atomic Absorption Spectrophotometer , for use at 251.6 nm.
NOTE 1—A wavelength other than 251.6 nm may be used if it has been determined to be equally suitable.
NOTE 2—The manufacturer’s instructions should be followed for all instrument parameters.
7.2 Silicon Light Source, silicon hollow cathode lamp.
7.3 Graphite Furnace, capable of reaching temperatures sufficient to atomize the element of interest.Atomization temperature
must be reached as rapidly as possible for maximum sensitivity.
NOTE 3—Special furnace accessories are commercially available to provide a means of accelerating atomization temperature.
7.4 Graphite Tubes, compatible with furnace device. Standard graphite tubes are preferred, particularly when tube pretreatment
is practiced. Pyrolytic graphite tubes may be used if it has been determined by the analyst that the precision, bias, and sensitivity
of the determination are not compromised.
7.5 Pipets:
7.5.1 Microlitre, with disposable, polypropylene tips. Sizes may range from 1 to 1000 µL, as required.
7.5.2 Millilitre, 50.0 mL.
7.6 Strip Chart Recorder—A recorder is strongly recommended so that there will be a permanent record of analysis and any
instrument problems can be easily recognized (such as drift, incomplete atomization, changes in sensitivity, etc.). A fast recorder
response (0.2 s or less for full scale deflection) is recommended to ensure accuracy. Electronic peak measuring devices may be
usediftheirresponsetimeissufficientlyfast.DataSystem—Fasttransientsignaldataarecollectedandprocessedusinganinternal
microprocessororexternaldesktopcomputersystems.Datacanbestoredondisks,transmittedtocentralservers,orprintedinhard
copy. Data may be evaluated and processed using the instrument’s dedicated systems to determine analyte concentrations. Users
of this practice may use a strip chart recorder to obtain sample and calibration data, if desired.
7.7 Ultrasonic Cleaner, operable at >20 KHz.
7.8 Flasks, volumetric, 100 and 1000-mL polyethylene.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where
D4517–04 (2009)
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
8.2 Purity of Water— All references to reagent water in this method shall be understood to conform to Specification D
1193D1193,forreagentwaterTypeII.Inaddition,thereagentwatershallbemadesilica-freeanddeterminedassuchinaccordance
with this method. The collecting apparatus and storage containers for the reagent water must be made of suitable materials that
will not contaminate the reagent water with silica (see Section 9).
NOTE 4—Silica-freewatermaybepreparedbydistillation,demineralization,andpassagethrougha0.22µmfilter.Totalremovalofcolloidalsilicamay
be done by treating the above water with hydrofluoric acid, letting it stand for 24 h, and then processing it through strong base ion-exchange resin in the
hydroxide form.
8.3 Calcium/Lanthanum Reagent—Wet 2.90 g of lanthanum oxide (La O 99.99 % pure) with about 50 mL of water in a 100
2 3
mL volumetric flask. Carefully add 5.5 mL of concentrated nitric acid (HNO sp gr 1.42) and swirl to dissolve. Add 0.100 g of
calcium oxide (CaO) and swirl to dissolve. Dilute to volume with water.This solution contains 100 mg/LCaO and 2500 mg/LLa.
Dilute 1:100 for injection. The diluted reagent is needed only for pretreatment of the graphite tube as described in 6.4.
8.4 Silica Stock Solution (1 mL = 1 mg SiO )— Dissolve 4.7 g of sodium metasilicate (Na SiO ·9H O) and dilute to 1 L with
2 2 3 2
water. Determine the silica concentration of this solution in accordance with Test Method D 859D859, Method A.
8.5 Silica Working Solution (1 mL = 0.05 mg SiO )—Dilute 50.0 mL of the silica stock solution (see 8.4) to 1 L with water in
a volumetric flask.The concentration of this diluted standard is calculated after confirming the concentration of the stock solution.
8.6 Argon, standard, welder’s grade, commercially available.
9. Sampling
9.1 Collect the sample in accordance with the applicableASTM standards: Practice D 1066D1066, Specification D 1192D1192,
and Practices D 3370D3370.
9.2 Since silica is such a ubiquitous material, meticulous sample collection, handling, and injection into the furnace are
necessary to avoid contamination.
9.2.1 Collect samples only in plastic or TFE-fluorocarbon containers. Polystyrene, polypropylene, linear polyethylene, and
TFE-fluorocarbon have been found to be generally suitable, but tests should be conducted on sample containers before use to
determine their suitability.
9.2.2 Sample containers must be ultrasonically cleaned before use. Fill the sample containers with water and immerse in an
operating ultrasonic cleaner for at least 1 min. Remove, shake vigorously, and drain.Additional cycles of cleaning may be found
necessary.
9.2.3 Before actual sample collection, rinse sample container with the sample it is to contain three times with vigorous shaking,
then fill. Do not allow any object to touch the inside of the bottle or cap.
10. Calibration
10.1 Prepare standards for test calibration containing about 0, 50, 100, 150, and 250 µg/Lof SiO by diluting 0, 100, 200, 300,
and 500 µL of the silica working solution (see 8.4) to 100 mL with water in separate volumetric flasks.
NOTE 5—Theexactconcentrationofthepreparedsilicastandardsisdeterminedfromtheresultobtainedbythegravimetricstandardizationofthestock
solution in 8.4.
10.2 Zero the instrument without making an injection or initiating an atomization program.
10.3 Set the atomization program (drying, charring, atomizing) according to the manufacturer’s instructions.
NOTE 6—While sample size and furnace programming vary among instruments, the following analytical conditions have generally been found to be
suitable. It is up to the analyst to optimize analytical conditions for the instrument used.
Aliquot—An aliquot size of 10 to 100 µL, depending on tube size and concentration of sample. The same aliquot size must be used for all standard,
sample, and blank injections.
Function Temperature, °C Time, s
Dry 100 1 s/µL
Char 1000 30
Atomize 2800 7
10.4 Determine the furnace blank by initiating the atomization program without making an injection. Repeat until the furnace
blank reproduces within 10 %.
NOTE 7—Determination of the furnace blank is a mechanism for evaluating the acceptability of the graphite tube for silica determination.
10.5 Inject a measured aliquot of the 100 µg/L of SiO standard solution (see 10.1) into the furnace, and initiate the present
atomization program. Repeat this analysis until the response reproduces within 10 %.
Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
D4517–04 (2009)
10.6 Determine the acceptability of the water by injecting a measured aliquot of the “0” standard solution into the furnace and
initiating the preset atom
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.