ASTM D7184-15(2019)e1
(Test Method)Standard Test Method for Ultra Low Nitrogen in Aromatic Hydrocarbons by Oxidative Combustion and Reduced Pressure Chemiluminescence Detection
Standard Test Method for Ultra Low Nitrogen in Aromatic Hydrocarbons by Oxidative Combustion and Reduced Pressure Chemiluminescence Detection
SIGNIFICANCE AND USE
5.1 This test method is useful to detect and quantify nitrogen-containing compounds at a concentration of 0.1 to 1.2 mg N/kg in light aromatic hydrocarbons used or produced in manufacturing process. These nitrogen-containing compounds are undesirable in finished aromatic products and may be used in setting specification for determining the total nitrogen content in aromatic hydrocarbons.
5.2 This test method requires the use of reduced pressure at the detector. Loss of vacuum or pressure fluctuations impact the sensitivity of the detector and the ability to determine nitrogen concentrations less than 1 mg N/kg.
SCOPE
1.1 This test method covers the determination of total nitrogen in aromatic hydrocarbons, such as benzene, toluene, and xylene.
1.2 This test method is applicable for samples containing nitrogen from 0.1 to 1.2 mg N/kg. For higher nitrogen concentrations refer to Test Method D4629. With careful analytical technique, this method can be used to successfully analyze concentrations below the current scope (see Appendix X1).
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 E29.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.
1.6 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.
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´1
Designation: D7184 − 15 (Reapproved 2019)
Standard Test Method for
Ultra Low Nitrogen in Aromatic Hydrocarbons by Oxidative
Combustion and Reduced Pressure Chemiluminescence
Detection
This standard is issued under the fixed designation D7184; 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.
ε NOTE—Editorial changes were made throughout in June 2019.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the determination of total
D3437 Practice for Sampling and Handling Liquid Cyclic
nitrogen in aromatic hydrocarbons, such as benzene, toluene,
Products
and xylene.
D4629 Test Method for Trace Nitrogen in Liquid Hydrocar-
1.2 This test method is applicable for samples containing
bons by Syringe/Inlet Oxidative Combustion and Chemi-
nitrogen from 0.1 to 1.2 mg N/kg. For higher nitrogen
luminescence Detection
concentrations refer to Test Method D4629. With careful
D6809 Guide for Quality Control and Quality Assurance
analytical technique, this method can be used to successfully
Procedures for Aromatic Hydrocarbons and Related Ma-
analyze concentrations below the current scope (see Appendix terials
X1). E29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications
1.3 In determining the conformance of the test results using
E691 Practice for Conducting an Interlaboratory Study to
this method to applicable specifications; results shall be
Determine the Precision of a Test Method
rounded off in accordance with the rounding-off method of
2.2 Other Documents:
Practice E29.
OSHA Regulations, 29 CFR paragraphs 1910. 1000 and
1910.1200
1.4 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Definitions:
1.5 This standard does not purport to address all of the
3.1.1 oxidative pyrolysis, n—a process in which a sample
safety concerns, if any associated with its use. It is the
undergoes combustion in an oxygen rich environment at
responsibility of the user of this standard to establish appro-
temperatures greater than 900°C.
priate safety, health, and environmental practices and deter-
3.1.2 pyrolytic decomposition, n—combusting a compound
mine the applicability of regulatory limitations prior to use.
to decompose it to carbon dioxide, water and elemental oxides.
For specific hazard statements, see Section 9.
3.1.3 reduced pressure chemiluminescence, n—a chemical
1.6 This international standard was developed in accor-
reaction at pressure less than 760 mm mercury (Hg) in which
dance with internationally recognized principles on standard-
light is emitted.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4. Summary of Test Method
mendations issued by the World Trade Organization Technical
4.1 A specimen is introduced into a carrier gas stream, at a
Barriers to Trade (TBT) Committee.
controlled rate, and incorporated into a high temperature
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D16 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsi- Standards volume information, refer to the standard’s Document Summary page on
bility of Subcommittee D16.04 on Instrumental Analysis. the ASTM website.
Current edition approved June 1, 2019. Published June 2019. Originally AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
approved in 2007. Last previous edition approved in 2015 as D7184 – 15. DOI: 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
10.1520/D7184-15R19E01. www.access.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D7184 − 15 (2019)
furnace (900 to 1150°C) where an excess of oxygen is added. 7.6 Liquid Auto-Sampler—Capable of injecting 5 to 250 µL
Pyrolysis converts hydrocarbons in the specimen to carbon of sample or as recommended by instrument manufacturer.
dioxide and water. Organic nitrogen and inorganic nitrogen
7.7 Boat Inlet System (Optional)—If the instrument is
compounds, present in the specimen, are converted to nitric
equipped with a boat inlet system, care must be taken to ensure
oxide (NO). Nitric oxide reacts with ozone in the detector
the boat is sufficiently cooled between analyses to prevent the
producing nitrogen dioxide molecules in an excited state. As
sample from vaporizing as it is injected into the boat. The
the excited nitrogen dioxide molecules relax to ground state,
sample should start vaporizing as it enters the furnace. It is
light is emitted.This light is detected by a photomultiplier tube
critical that the sample vaporize at a constant and reproducible
or by a photodiode with the resulting signal proportional to the
rate.
concentration of nitrogen in the sample. Operating the detector
7.8 Automatic Boat Drive System—If the instrument is
at a reduced pressure lowers the probability of the excited
equipped with a boat inlet system, the boat should be intro-
nitrogen dioxide molecule colliding with other molecules
duced into the furnace at a controlled rate.
before it undergoes chemiluminescence. Thus, reduced pres-
sure provides improved sensitivity and lower noise. 7.9 Membrane Dryer—Removes moisture of combustion
before the detector.
5. Significance and Use
8. Reagents
5.1 This test method is useful to detect and quantify
8.1 Purity of Reagents—Reagent grade chemicals shall be
nitrogen-containing compounds at a concentration of 0.1 to 1.2
used in all tests. It is intended that all reagents shall conform to
mg N/kg in light aromatic hydrocarbons used or produced in
the specifications of the Committee on Analytical Reagents of
manufacturing process. These nitrogen-containing compounds
the American Chemical Society, where such specifications are
are undesirable in finished aromatic products and may be used
available, unless otherwise indicated. Other grades may be
in setting specification for determining the total nitrogen
used, provided it is first ascertained that the reagent is of
content in aromatic hydrocarbons.
sufficiently high purity to permit its use without lessening the
5.2 This test method requires the use of reduced pressure at
accuracy of the determination.
the detector. Loss of vacuum or pressure fluctuations impact
8.2 Inert Gas—Either argon (Ar) or helium (He) may be
the sensitivity of the detector and the ability to determine
used. The purity shall be no less than 99.99 mol %.
nitrogen concentrations less than 1 mg N/kg.
8.3 Oxygen Gas—The purity shall be no less than 99.99
mol %.
6. Interferences
8.4 Solvent—The solvent of choice should be capable of
6.1 Chlorides,bromides,andiodidescaninterfereifanyone
dissolving the nitrogen sample. The solvent of choice should
or all of these elements are present in a sample in concentra-
have a boiling point similar to the sample being analyzed. The
tions greater than 10 % by total weight of halogen in the
solvent should contain less than 0.05 mg N/L. The blank value
sample.
must be determined for each new bottle of solvent. Suggested
6.2 Moisture in the sample produced during the combustion
possibilities include, but not limited to methanol, iso-octane
step can interfere if not removed prior to the gas entering the
and p-xylene.
detector cell.
NOTE 1—A quick screening can be conducted by injecting the solvent
and sample once or twice and comparing relative area counts.
7. Apparatus
8.5 Nitrogen Stock Solution, approximately 1000 mg N/L—
7.1 Pyrolysis Furnace—Afurnace capable of maintaining a
Prepare a stock solution by weighing, to the nearest 0.1 mg
temperaturesufficienttovolatilizeandpyrolysethesampleand
approximately 0.57 g of pyridine into a 100 ml volumetric
oxidize organically bound nitrogen to NO.The actual tempera-
flask. Dilute to the mark with solvent. Calculate the actual
ture should be recommended by the specific instrument manu-
concentration of nitrogen using Eq 1. This standard may also
facturer.
be purchased.
7.2 Quartz Pyrolysis Tube—Capable of withstanding 900 to 6
Wt. of pyridine in grams 3 .1771 3 10
~ ! ~ ! ~ !
mgN/L 5 (1)
1200°C.
100 ml of solvent
7.3 Chemiluminescence Detector—Capable of operation at
where:
reduced pressure (less than 760 mm mercury) and able to
% nitrogen in pyridine = 17.71
measure light emitted from the reaction between NO and
8.6 Nitrogen Working Standard Solution—Calculatethecor-
ozone.
rect concentration obtained from the nitrogen stock solution
7.4 Microliter Syringe—5 to 250 µL or as recommended by
instrument manufacturer.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. for suggestions on the testing of reagents not
7.5 Constant Rate Injector System—If the sample is to be
listed by the American Chemical Society, see Analar Standards for Laboratory
introduced into the pyrolysis furnace via syringe, use a
Chemicals, BDH Ltd. Poole Dorset, U.K., and the United States Pharmacopeia and
constant rate injector or a liquid introduction module or as
National Formulary, U.S. Pharamacopeial Convention, Inc. (USPC) Rockville,
recommended by instrument manufacturer. MD.
´1
D7184 − 15 (2019)
prepared in 8.5 and prepare the working standards by diluting 11.3 Adjust gas flows and pyrolysis temperatures to the
the stock solution with the solvent. Prepare approximately 10.0 operating conditions as recommended by the instrument manu-
mg N/L standard by accurately pipeting 1.0 mL of the stock facturer.
solution into a 100 ml volumetric flask and dilute to mark with
11.4 The actual operation of injecting a sample will vary
solvent. This Standard is further diluted to 0.05, 0.10, 0.5 and
depending upon the instrument manufacturer and type of inlet
1.0 mg N/L by accurately pipeting 0.5, 1.0, 5 and 10.0 mL of
system used (see 7.5 – 7.8).
standardintofourseparate100mLvolumetricflasksanddilute
to the mark with solvent. The working standards will be
12. Calibration and Standardization
approximately blank, 0.05, 0.1, 0.5, and 1.0 mg N/L. Calculate
12.1 Prepare the working calibration standards using the
the correct concentrations using the calculation:
stock solution as described in 8.5 and 8.6.
mg N/L 5 ~mg N/L in working standard! 3 ~ml pipeted!/~100 ml!(2)
12.2 Before injecting a standard or blank, refer to the
or
procedures (Section 13), to ensure proper technique for either
mg N/Kg 5 ~mg N/L in working standard!
the direct injection system or the boat inlet system.
3 ml pipeted / 100 ml * Density of solution g/ml (3)
~ ! ~ ! ~ !
12.3 A calibration based on the four gravimetrically pre-
Alternate volumes of solutions may be prepared so long as
pared standards works well within the limited scope of this
the preparation meets the concentration specified.
procedure. This type of calibration can be used to quantitate
nitrogen at the 0.1 to 1.2 mg N/kg concentration range.
NOTE 2—Working standards should be prepared on a regular basis
depending upon the frequency of use and age. The stock solution can be
12.4 Run a calibration program for linear regression in
retained, if refrigerated, for up to three months. Do not refrigerate stock
accordance with the instrument manufacturer’s recommenda-
solutionifpreparedinbenzeneasthebenzenewillfreezeandcauseerratic
tions.The correlation coefficient should be a minimum of 0.99.
results.
12.5 Inject each standard and blank at least 3 times.
8.7 Cupric Oxide (CuO or Platinum (Pt)—May be used as
an oxidation catalyst in the combustion tube, as recommended
NOTE 3—The calibration corrects for residual nitrogen content of the
by the instrument manufacturer.
solvent used to make the standards (often greater than 0.05 mg N/L) by
generating the regression line as a standard addition to the solvent blank.
8.8 Quartz Wool—May be needed if recommended by the
The slope generated is used to create a calibration line starting at the
instrument manufacturer.
origin, that is, zero signal for nitrogen.
9. Hazards
13. Procedure
9.1 Consult current OSHA regulations, chemical suppliers’
13.1 Sample size from 5 to 250 µL is acceptable.
Safety Data Sheets, and local regulations for all material used
13.2 When using a constant rate injector always flush the
in this test method.
syringeseveraltimeswiththematerialtobeinjectedtoprevent
9.2 High temperature is employed in this test method.
contamination. Do not return the first few flushes back into the
Extreme care should be exercised when using flammable
specimen bottle.
materials near the pyrolysis furnace.
13.3 If using an auto-sampler, set the program to the
9.3 Ozone can be hazardous so use of a good vented room
instrument manufacturer’s recommendations.
is necessary.
NOTE 4—Follow instrument manufacturer’s recommendations for
sample size.
10. Sample Handling
13.4 Set the automatic boat control to the instrument manu-
10.1 Collect the sample in accordance with Practice D3437.
facturer’s recommendations. Cycle the empty boat in and out
10.2 To preserve sample integrity and prevent the loss of
of the combustion furnace to remove any residual contamina-
volatile components, which may be in some samples, do not
tion until you see a minimum peak on your baseline as a result
expose samples to the atmosphere any longer than necessary.
of the cycling of the empty boat.
Analyze specimen as soon as possible after transferring from
13.5 Fill the auto-sampler vials with the samples and place
the sample container to prevent loss of nitrogen or contamina-
the vials into the rack.
tion.
13.6 Using a constant rate injector, fill the syringe past the
10.3 Since this procedure is intended for trace level
desiredvolumetobeinjected,(thatis,ifyouaregoingtoinject
analysis, care must be taken to ensure that the sample
50 µL fill the syringe to 60 µL and then back to 50 µL), taking
container, and working standards containers are clean and do
care not to pull air bubbles into the syringe with the sample.
not contaminate the sample.
With the syringe needle pointed up, push the plunger to the
desired volume, tap the last drop off the needle point, and pull
11. Instrument Assembly and Preparation
the plunger back until air can be seen in the syringe barrel.
11.1 Setup the instrument in accordance with the instrument
NOTE 5—The inherent accuracy of this technique is dependent upon the
man
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM 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.
´1
Designation: D7184 − 15 D7184 − 15 (Reapproved 2019)
Standard Test Method for
Ultra Low Nitrogen in Aromatic Hydrocarbons by Oxidative
Combustion and Reduced Pressure Chemiluminescence
Detection
This standard is issued under the fixed designation D7184; 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.
ε NOTE—Editorial changes were made throughout in June 2019.
1. Scope*Scope
1.1 This test method covers the determination of total nitrogen in aromatic hydrocarbons, such as benzene, toluene, and xylene.
1.2 This test method is applicable for samples containing nitrogen from 0.1 to 1.2 mg N/kg. For higher nitrogen concentrations
refer to Test Method D4629. With careful analytical technique, this method can be used to successfully analyze concentrations
below the current scope (see Appendix X1).
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 E29.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
D3437 Practice for Sampling and Handling Liquid Cyclic Products
D4629 Test Method for Trace Nitrogen in Liquid Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence
Detection
D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 Other Documents:
OSHA Regulations, 29 CFR paragraphs 1910. 1000 and 1910.1200
3. Terminology
3.1 Definitions:
3.1.1 oxidative pyrolysis, n—a process in which a sample undergoes combustion in an oxygen rich environment at temperatures
greater than 900°C.
3.1.2 pyrolytic decomposition, n—combusting a compound to decompose it to carbon dioxide, water and elemental oxides.
This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons Aromatic, Industrial, Specialty and Related Chemicals and is the direct
responsibility of Subcommittee D16.04 on Instrumental Analysis.
Current edition approved June 1, 2015June 1, 2019. Published June 2015June 2019. Originally approved in 2007. Last previous edition approved in 20132015 as
D7184D7184 – 15. – 13. DOI: 10.1520/D7184-15.10.1520/D7184-15R19E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D7184 − 15 (2019)
3.1.3 reduced pressure chemiluminescence, n—a chemical reaction at pressure less than 760 mm mercury (Hg) in which light
is emitted.
4. Summary of Test Method
4.1 A specimen is introduced into a carrier gas stream, at a controlled rate, and incorporated into a high temperature furnace
(900 to 1150°C) where an excess of oxygen is added. Pyrolysis converts hydrocarbons in the specimen to carbon dioxide and water.
Organic nitrogen and inorganic nitrogen compounds, present in the specimen, are converted to nitric oxide (NO). Nitric oxide
reacts with ozone in the detector producing nitrogen dioxide molecules in an excited state. As the excited nitrogen dioxide
molecules relax to ground state, light is emitted. This light is detected by a photomultiplier tube or by a photodiode with the
resulting signal proportional to the concentration of nitrogen in the sample. Operating the detector at a reduced pressure lowers
the probability of the excited nitrogen dioxide molecule colliding with other molecules before it undergoes chemiluminescence.
Thus, reduced pressure provides improved sensitivity and lower noise.
5. Significance and Use
5.1 This test method is useful to detect and quantify nitrogen-containing compounds at a concentration of 0.1 to 1.2 mg N/kg
in light aromatic hydrocarbons used or produced in manufacturing process. These nitrogen-containing compounds are undesirable
in finished aromatic products and may be used in setting specification for determining the total nitrogen content in aromatic
hydrocarbons.
5.2 This test method requires the use of reduced pressure at the detector. Loss of vacuum or pressure fluctuations impact the
sensitivity of the detector and the ability to determine nitrogen concentrations less than 1 mg N/kg.
6. Interferences
6.1 Chlorides, bromides, and iodides can interfere if any one or all of these elements are present in a sample in concentrations
greater than 10 % by total weight of halogen in the sample.
6.2 Moisture in the sample produced during the combustion step can interfere if not removed prior to the gas entering the
detector cell.
7. Apparatus
7.1 Pyrolysis Furnace—A furnace capable of maintaining a temperature sufficient to volatilize and pyrolyse the sample and
oxidize organically bound nitrogen to NO. The actual temperature should be recommended by the specific instrument
manufacturer.
7.2 Quartz Pyrolysis Tube—Capable of withstanding 900 to 1200°C.
7.3 Chemiluminescence Detector—Capable of operation at reduced pressure (less than 760 mm mercury) and able to measure
light emitted from the reaction between NO and ozone.
7.4 Microliter Syringe—5 to 250 μL or as recommended by instrument manufacturer.
7.5 Constant Rate Injector System—If the sample is to be introduced into the pyrolysis furnace via syringe, use a constant rate
injector or a liquid introduction module or as recommended by instrument manufacturer.
7.6 Liquid Auto-Sampler—Capable of injecting 5 to 250 μL of sample or as recommended by instrument manufacturer.
7.7 Boat Inlet System (Optional)—If the instrument is equipped with a boat inlet system, care must be taken to ensure the boat
is sufficiently cooled between analyses to prevent the sample from vaporizing as it is injected into the boat. The sample should start
vaporizing as it enters the furnace. It is critical that the sample vaporize at a constant and reproducible rate.
7.8 Automatic Boat Drive System—If the instrument is equipped with a boat inlet system, the boat should be introduced into
the furnace at a controlled rate.
7.9 Membrane Dryer—Removes moisture of combustion before the detector.
8. Reagents
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. It is intended that all reagents shall conform to the
specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available,
unless otherwise indicated. 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.
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. Pharamacopeial Convention, Inc. (USPC) Rockville, MD.
´1
D7184 − 15 (2019)
8.2 Inert Gas—Either argon (Ar) or helium (He) may be used. The purity shall be no less than 99.99 mol %.
8.3 Oxygen Gas—The purity shall be no less than 99.99 mol %.
8.4 Solvent—The solvent of choice should be capable of dissolving the nitrogen sample. The solvent of choice should have a
boiling point similar to the sample being analyzed. The solvent should contain less than 0.05 mg N/L. The blank value must be
determined for each new bottle of solvent. Suggested possibilities include, but not limited to methanol, iso-octane and p-xylene.
NOTE 1—A quick screening can be conducted by injecting the solvent and sample once or twice and comparing relative area counts.
8.5 Nitrogen Stock Solution, approximately 1000 mg N/L—Prepare a stock solution by weighing, to the nearest 0.1 mg
approximately 0.57 g of pyridine into a 100 ml volumetric flask. Dilute to the mark with solvent. Calculate the actual concentration
of nitrogen using Eq 1. This standard may also be purchased.
Wt. of pyridine in grams 3 .1771 3 10
~ ! ~ ! ~ !
mg N/L5 (1)
100 ml of solvent
where:
% nitrogen in pyridine = 17.71
8.6 Nitrogen Working Standard Solution—Calculate the correct concentration obtained from the nitrogen stock solution
prepared in 8.5 and prepare the working standards by diluting the stock solution with the solvent. Prepare approximately 10.0 mg
N/L standard by accurately pipeting 1.0 mL of the stock solution into a 100 ml volumetric flask and dilute to mark with solvent.
This Standard is further diluted to 0.05, 0.10, 0.5 and 1.0 mg N/L by accurately pipeting 0.5, 1.0, 5 and 10.0 mL of standard into
four separate 100 mL volumetric flasks and dilute to the mark with solvent. The working standards will be approximately blank,
0.05, 0.1, 0.5, and 1.0 mg N/L. Calculate the correct concentrations using the calculation:
mg N/L 5 ~mg N/L in working standard! 3~ml pipeted!/~100 ml! (2)
or
mg N/Kg 5 mg N/L in working standard 3 ml pipeted / 100 ml * Density of solution g/ml (3)
~ ! ~ ! ~ ! ~ !
Alternate volumes of solutions may be prepared so long as the preparation meets the concentration specified.
NOTE 2—Working standards should be prepared on a regular basis depending upon the frequency of use and age. The stock solution can be retained,
if refrigerated, for up to three months. Do not refrigerate stock solution if prepared in benzene as the benzene will freeze and cause erratic results.
8.7 Cupric Oxide (CuO or Platinum (Pt)—May be used as an oxidation catalyst in the combustion tube, as recommended by
the instrument manufacturer.
8.8 Quartz Wool—May be needed if recommended by the instrument manufacturer.
9. Hazards
9.1 Consult current OSHA regulations, chemical suppliers’ Safety Data Sheets, and local regulations for all material used in this
test method.
9.2 High temperature is employed in this test method. Extreme care should be exercised when using flammable materials near
the pyrolysis furnace.
9.3 Ozone can be hazardous so use of a good vented room is necessary.
10. Sample Handling
10.1 Collect the sample in accordance with Practice D3437.
10.2 To preserve sample integrity and prevent the loss of volatile components, which may be in some samples, do not expose
samples to the atmosphere any longer than necessary. Analyze specimen as soon as possible after transferring from the sample
container to prevent loss of nitrogen or contamination.
10.3 Since this procedure is intended for trace level analysis, care must be taken to ensure that the sample container, and
working standards containers are clean and do not contaminate the sample.
11. Instrument Assembly and Preparation
11.1 Setup the instrument in accordance with the instrument manufacturer’s instructions.
11.2 Set instrument parameters in accordance with instrument manufacturer’s recommendations.
11.3 Adjust gas flows and pyrolysis temperatures to the operating conditions as recommended by the instrument manufacturer.
11.4 The actual operation of injecting a sample will vary depending upon the instrument manufacturer and type of inlet system
used (see 7.5 – 7.8).
´1
D7184 − 15 (2019)
12. Calibration and Standardization
12.1 Prepare the working calibration standards using the stock solution as described in 8.5 and 8.6.
12.2 Before injecting a standard or blank, refer to the procedures (Section 13), to ensure proper technique for either the direct
injection system or the boat inlet system.
12.3 A calibration based on the four gravimetrically prepared standards works well within the limited scope of this procedure.
This type of calibration can be used to quantitate nitrogen at the 0.1 to 1.2 mg N/kg concentration range.
12.4 Run a calibration program for linear regression in accordance with the instrument manufacturer’s recommendations. The
correlation coefficient should be a minimum of 0.99.
12.5 Inject each standard and blank at least 3 times.
NOTE 3—The calibration corrects for residual nitrogen content of the solvent used to make the standards (often greater than 0.05 mg N/L) by generating
the regression line as a standard addition to the solvent blank. The slope generated is used to create a calibration line starting at the origin, that is, zero
signal for nitrogen.
13. Procedure
13.1 Sample size from 5 to 250 μL is acceptable.
13.2 When using a constant rate injector always flush the syringe several times with the material to be injected to prevent
contamination. Do not return the first few flushes back into the specimen bottle.
13.3 If using an auto-samplerauto-sampler, set the program to the instrument manufacturer’s recommendations.
NOTE 4—Follow instrument manufacturer’s recommendations for sample size.
13.4 Set the automatic boat control to the instrument manufacturer’s recommendations. Cycle the empty boat in and out of the
combustion furnace to remove any residual contamina
...
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