ASTM D4629-17

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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
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Designation: D4629 − 12 (Reapproved 2017) D4629 − 17
Designation: 379/88
Standard Test Method for
Trace Nitrogen in Liquid Petroleum Hydrocarbons by
Syringe/Inlet Oxidative Combustion and Chemiluminescence
Detection
This standard is issued under the fixed designation D4629; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers the determination of the trace total nitrogen naturally found in liquid hydrocarbons boiling in the
range from approximately 50 °C to 400 °C, with viscosities between approximately 0.2 cSt and 10 cSt (mm /s) at room
temperature. This test method is applicable to naphthas, distillates, and oils containing 0.3 mg ⁄kg to 100 mg ⁄kg total nitrogen. For
liquid hydrocarbons containing more than 100 mg ⁄kg total nitrogen, Test Method D5762 can be more appropriate. This test method
has been successfully applied, during interlaboratory studies, to sample types outside the range of the scope by dilution of the
sample in an appropriate solvent to bring the total nitrogen concentration and viscosity to within the range covered by the test
method. However, it is the responsibility of the analyst to verify the solubility of the sample in the solvent and that direct
introduction of the diluted sample by syringe into the furnace does not cause low results due to pyrolysis of the sample or solvent
in the syringe needle.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. See 6.2, 6.4, 6.5, 6.9, and Section 7.
1.4 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:
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D5762 Test Method for Nitrogen in Liquid Hydrocarbons, Petroleum and Petroleum Products by Boat-Inlet Chemiluminescence
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
3. Summary of Test Method
3.1 The sample of liquid petroleum hydrocarbon is introduced either by syringe or boat inlet system, into a stream of inert gas
(helium or argon). The sample is vaporized and carried to a high temperature zone where oxygen is introduced and organically
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.03 on Elemental Analysis.
Current edition approved July 1, 2017Dec. 15, 2017. Published July 2017February 2018. Originally approved in 1986. Last previous edition approved in 20122017 as
D4629 – 12.D4629 – 12 (2017). DOI: 10.1520/D4629-12R17.10.1520/D4629-17.
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.
*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
D4629 − 17
bound nitrogen is converted to nitric oxide (NO). The NO contacts ozone, and is converted to excited nitrogen dioxide (NO ). The
light emitted as the excited NO decays is detected by a photomultiplier tube and the resulting signal is a measure of the nitrogen
contained in the sample.
4. Significance and Use
4.1 Some process catalysts used in petroleum and chemical refining may be poisoned when even trace amounts of nitrogenous
materials are contained in the feedstocks. This test method can be used to determine bound nitrogen in process feeds and may also
be used to control nitrogen compounds in finished products.
5. Apparatus
5.1 Furnace, electric, held at a temperature sufficient to volatilize and pyrolyze all of the sample and oxidize the organically
bound nitrogen to NO. Furnace temperature(s) shall be as recommended by the manufacturer (typically around 1000 °C).
5.2 Combustion Tube, fabricated to meet the instrument manufacturer’s specifications.
5.3 Drier Tube—The reaction products include water vapor that must be eliminated prior to measurement by the detector. This
can be accomplished with a magnesium perchlorate Mg(ClO ) scrubber or a membrane drying tube (permeation drier), or by
4 2
whatever other means the instrument manufacturer specifies as appropriate for the instrument being used.
5.4 Chemiluminescent Detector, capable of measuring light emitted from the reaction between NO and ozone.
5.5 Totalizer, having variable attenuation, and capable of measuring, amplifying, and integrating the current from the
chemiluminescent detector. A built in microprocessor or attached computer system may perform these functions.
5.6 Micro-litre Syringe, of 5 μL, 10 μL, 25 μL, 50 μL, or 250 μL capacity capable of accurately delivering micro-litre quantities
is required. The needle should be long enough to reach the hottest portion of the inlet section of the furnace when injecting the
sample. The syringe may be part of an automatic sampling and injection device used with the instrument.
5.7 Strip Chart Recorder (Optional).
5.8 Sample Inlet System—One of the following must be used:
5.8.1 Manually Operated Syringe.
5.8.2 Syringe, with a constant rate injector system, capable of delivering a sample at a precisely controlled rate.
5.8.3 Boat Inlet System, to facilitate analysis of samples that would react with the syringe or syringe needle. The pyrolysis tube
for boat inlet use may require specific construction to permit insertion of a boat fully into the inlet section of the furnace. The boat
inlet system external to the furnace may be cooled to a temperature below room temperature to aid in dissipating the heat from
the boat when it is removed from the furnace. Cooling the boat inlet system may also reduce the chances of the sample combusting
in the boat before introduction into the furnace and may be necessary when running volatile samples such as naphtha using a boat
inlet system.
5.9 Quartz Insert Tube (Optional),may be packed with cupric oxide (CuO) or other oxidation catalyst as recommended by the
instrument manufacturer, to aid in completing oxidation. This is inserted into the exit end of the pyrolysis tube.
5.10 Vacuum System (Optional),The chemiluminescence detector may be equipped with a vacuum system to maintain the
reaction cell at reduced pressure (typically 20 mm to 25 mm Hg). This can improve the signal to noise ratio of the detector.
5.11 Analytical Balance (Optional),with a precision of 60.01 mg.
6. Reagents
6.1 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
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.
6.2 Magnesium Perchlorate Mg(ClO ) , for drying products of combustion (if permeation drier is not used.) (Warning—Strong
4 2
oxidizer, irritant.)
6.3 Inert Gas, argon or helium, ultra-high purity grade (UHP).
6.4 Oxygen, (99.8 % or better, 99.996 % is recommended). (Warning—Vigorously accelerates combustion.)
6.5 Solvents, for diluting and matrix matching such as, toluene, isooctane, xylene, acetone, cetane. (Other solvents similar to
those occurring in samples to be analyzed are also acceptable). Solvents should contain less than 0.1 μg N/mL. (Warning—
Flammable solvents.)
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. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D4629 − 17
6.6 Nitrogen Stock Solution, 1000 μg N/mL,Prepare a stock solution by accurately weighing approximately 1.195 g of carbazole
or 0.565 g of pyridine to the nearest milligram, into a tared 100 mL volumetric flask (see 6.6.1). Fifteen millilitres of acetone may
then be added when using carbazole to help dissolve it. Dilute to volume with the selected solvent. Calculate the exact
concentration of the stock solution based on the actual mass of pyridine or carbazole used and corrected for any known purity
factors for the specific lot of pyridine or carbazole. This stock may be further diluted to desired nitrogen concentrations.
6.6.1 Calibration standards from commercial sources may be used if they conform to the requirements of the test method.
NOTE 1—Pyridine should be used with low boiling solvents (<220 °C).
NOTE 2—Carbazole should be used with high boiling solvents (>220 °C).
NOTE 3—Working standards should be remixed on a regular basis depending upon frequency of use and age. Typically, standards have a useful life
of about 3 months, and should be refrigerated when not being used.
6.7 Cupric Oxide Wire, as recommended by instrument manufacturer.
6.8 Quartz Wool (optional), or other suitable absorbent material that is stable and capable of withstanding temperatures inside
the furnace (Note 4).
NOTE 4—Materials meeting the requirements in 6.8 are recommended to be used in sample boats to provide a more uniform injection of the sample
into the boat by wicking any remaining drops of the sample from the tip of the syringe needle prior to introduction of the sample into the furnace. Consult
instrument manufacturer recommendations for further guidance.
6.9 Pyridine. (Warning—Flammable, irritant.)
6.10 Carbazole.
7. Hazards
7.1 High temperature is employed in this test method. Exercise care when using flammable materials near the pyrolysis furnace.
8. Sampling
8.1 To preserve volatile components, which may be in some samples, do not uncover samples any longer than necessary.
Analyze samples as soon as possible after taking from the bulk supplies to prevent loss of nitrogen or contamination due to
exposure or contact with sample container.
9. Assembly Apparatus
9.1 Assemble apparatus in accordance with manufacturer’s instructions.
9.2 Adjust the gas flows and the pyrolysis temperature as recommended by the instrument manufacturer.
10. Calibration and Standardization
10.1 Prepare a series of calibration standards from the stock solution (see 6.6) covering the range of operation and consisting
of nitrogen type and matrix similar to samples to be analyzed. There shall be a minimum of two calibration standards in addition
to the solvent blank, used to generate the calibration curve.
10.2 Determine the volume or mass of the material to be analyzed by using one of the volumetric or gravimetric methods
described below.
10.2.1 Volumetric measurement of the in
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