ASTM D4629-02(2007)
(Test Method)Standard Test Method for Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection
Standard Test Method for Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection
SIGNIFICANCE AND USE
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.
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 to 400°C, with viscosities between approximately 0.2 and 10 cSt (mm2/s) at room temperature. This test method is applicable to naphthas, distillates, and oils containing 0.3 to 100 mg/kg total nitrogen. For liquid hydrocarbons containing more than 100 mg/kg total nitrogen, Test Method D 5762 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.
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.
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An American National Standard
Designation:D4629–02 (Reapproved 2007)
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 D 4629; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 1298 Test Method for Density, Relative Density (Specific
Gravity), or API Gravity of Crude Petroleum and Liquid
1.1 This test method covers the determination of the trace
Petroleum Products by Hydrometer Method
total nitrogen naturally found in liquid hydrocarbons boiling in
D 4052 Test Method for Density and Relative Density of
the range from approximately 50 to 400°C, with viscosities
Liquids by Digital Density Meter
between approximately 0.2 and 10 cSt (mm /s) at room
D 5762 Test Method for Nitrogen in Petroleum and Petro-
temperature. This test method is applicable to naphthas, distil-
leum Products by Boat-Inlet Chemiluminescence
lates, and oils containing 0.3 to 100 mg/kg total nitrogen. For
D 6299 Practice for Applying Statistical Quality Assurance
liquid hydrocarbons containing more than 100 mg/kg total
Techniques to Evaluate Analytical Measurement System
nitrogen, Test Method D 5762 can be more appropriate. This
Performance
test method has been successfully applied, during interlabora-
tory studies, to sample types outside the range of the scope by
3. Summary of Test Method
dilution of the sample in an appropriate solvent to bring the
3.1 The sample of liquid petroleum hydrocarbon is intro-
total nitrogen concentration and viscosity to within the range
duced either by syringe or boat inlet system, into a stream of
covered by the test method. However, it is the responsibility of
inert gas (helium or argon). The sample is vaporized and
the analyst to verify the solubility of the sample in the solvent
carried to a high temperature zone where oxygen is introduced
and that direct introduction of the diluted sample by syringe
and organically bound nitrogen is converted to nitric oxide
into the furnace does not cause low results due to pyrolysis of
(NO). The NO contacts ozone, and is converted to excited
the sample or solvent in the syringe needle.
nitrogen oxide (NO ). The light emitted as the excited NO
2 2
1.2 The values stated in SI units are to be regarded as
decays is detected by a photomultiplier tube and the resulting
standard.
signal is a measure of the nitrogen contained in the sample.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Some process catalysts used in petroleum and chemical
priate safety and health practices and determine the applica-
refining may be poisoned when even trace amounts of nitrog-
bility of regulatory limitations prior to use. See 6.2, 6.4, 6.5,
enous materials are contained in the feedstocks. This test
6.9, and Section 7.
method can be used to determine bound nitrogen in process
2. Referenced Documents feeds and may also be used to control nitrogen compounds in
2 finished products.
2.1 ASTM Standards:
5. Apparatus
This test method is under the jurisdiction of ASTM Committee D02 on
5.1 Furnace, electric, held at a temperature sufficient to
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
volatilize and pyrolyze all of the sample and oxidize the
D02.03 on Elemental Analysis.
organically bound nitrogen to NO. Furnace temperature(s)
CurrenteditionapprovedMay1,2007.PublishedJuly2007.Originallyapproved
in 1986. Last previous edition approved in 2002 as D 4629–02. shall be as recommended by the manufacturer (typically
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
around 1000°C).
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.2 Combustion Tube, fabricated to meet the instrument
Standards volume information, refer to the standard’s Document Summary page on
manufacturer’s specifications.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4629–02 (2007)
5.3 Drier Tube—The reaction products include water vapor where such specifications are available. Other grades may be
that must be eliminated prior to measurement by the detector. used, provided it is first ascertained that the reagent is of
This can be accomplished with a magnesium perchlorate sufficiently high purity to permit its use without lessening the
Mg(ClO ) scrubber or a membrane drying tube (permeation accuracy of the determination.
4 2
drier),orbywhateverothermeanstheinstrumentmanufacturer
6.2 Magnesium Perchlorate Mg(ClO ) ,fordryingproducts
4 2
specifies as appropriate for the instrument being used.
of combustion (if permeation drier is not used.) (Warning—
5.4 Chemiluminescent Detector, capable of measuring light
Strong oxidizer, irritant.)
emitted from the reaction between NO and ozone.
6.3 Inert Gas, argon or helium, ultra-high purity grade
5.5 Totalizer, having variable attenuation, and capable of
(UHP).
measuring, amplifying, and integrating the current from the
6.4 Oxygen, (99.8 % or better, 99.996 % is recommended).
chemiluminescent detector. A built in microprocessor or at-
(Warning—Vigorously accelerates combustion.)
tached computer system may perform these functions.
6.5 Solvents, for diluting and matrix matching such as,
5.6 Micro-litre Syringe, of 5, 10, 25, 50, or 250 µLcapacity
toluene, isooctane, xylene, acetone, cetane. (Other solvents
capable of accurately delivering micro-litre quantities is re-
similar to those occurring in samples to be analyzed are also
quired. The needle should be long enough to reach the hottest
acceptable). Solvents should contain less than 0.1 µg N/mL.
portion of the inlet section of the furnace when injecting the
(Warning—Flammable solvents.)
sample.The syringe may be part of an automatic sampling and
6.6 Nitrogen Stock Solution, 1000 µg N/mL, Prepare a stock
injection device used with the instrument.
solution by accurately weighing approximately 1.195 g of
5.7 Strip Chart Recorder (Optional).
carbazole or 0.565 g of pyridine to the nearest milligram, into
5.8 Sample Inlet System—One of the following must be
a tared 100-mL volumetric flask. Fifteen millilitres of acetone
used:
may then be added when using carbazole to help dissolve it.
5.8.1 Manually Operated Syringe.
Dilute to volume with the selected solvent. Calculate the exact
5.8.2 Syringe, with a constant rate injector system, capable
concentration of the stock solution based on the actual mass of
of delivering a sample at a precisely controlled rate.
pyridine or carbazole used and corrected for any known purity
5.8.3 Boat Inlet System, to facilitate analysis of samples that
factors for the specific lot of pyridine or carbazole. This stock
would react with the syringe or syringe needle. The pyrolysis
may be further diluted to desired nitrogen concentrations.
tube for boat inlet use may require specific construction to
permit insertion of a boat fully into the inlet section of the
NOTE 1—Pyridine should be used with low boiling solvents (<220°C).
furnace. The boat inlet system external to the furnace may be
NOTE 2—Carbazole should be used with high boiling solvents
cooled to a temperature below room temperature to aid in (>220°C).
dissipating the heat from the boat when it is removed from the NOTE 3—Working standards should be remixed on a regular basis
depending upon frequency of use and age. Typically, standards have a
furnace. Cooling the boat inlet system may also reduce the
useful life of about 3 months, and should be refrigerated when not being
chances of the sample combusting in the boat before introduc-
used.
tion into the furnace and may be necessary when running
volatile samples such as naphtha using a boat inlet system.
6.7 Cupric Oxide Wire, as recommended by instrument
5.9 Quartz Insert Tube (Optional), may be packed with
manufacturer.
cupric oxide (CuO) or other oxidation catalyst as recom-
6.8 Quartz Wool.
mended by the instrument manufacturer, to aid in completing
6.9 Pyridine.(Warning—Flammable, irritant.)
oxidation. This is inserted into the exit end of the pyrolysis
6.10 Carbazole.
tube.
5.10 Vacuum System (Optional), The chemiluminescence
7. Hazards
detector may be equipped with a vacuum system to maintain
7.1 High temperature is employed in this test method.
the reaction cell at reduced pressure (typically 20 to 25 mm
Exercise care when using flammable materials near the pyroly-
Hg). This can improve the signal to noise ratio of the detector.
sis furnace.
5.11 Analytical Balance (Optional), with a precision of
60.01 mg.
8. Sampling
6. Reagents
8.1 To preserve volatile components, which may be in some
6.1 Purity of Reagents—Reagent grade chemicals shall be
samples, do not uncover samples any longer than necessary.
used in all tests. Unless otherwise indicated, it is intended that
Analyze samples as soon as possible after taking from the bulk
all reagents shall conform to the specifications of the Commit-
supplies to prevent loss of nitrogen or contamination due to
teeonAnalyticalReagentsoftheAmericanChemicalSociety,
exposure or contact with sample container.
9. Assembly Apparatus
Reagent Chemicals, American Chemical Society Specifications , American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not 9.1 Assemble apparatus in accordance with manufacturer’s
listed by the American Chemical Society, see Analar Standards for Laboratory
instructions.
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
9.2 Adjust the gas flows and the pyrolysis temperature as
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. recommended by the instrument manufacturer.
D4629–02 (2007)
10. Calibration and Standardization 10.5 Calibration curves shall be generated in one of the
following manners depending on the capability of the instru-
10.1 Prepare a series of calibration standards from the stock
mentation used.
solution (see 6.6) covering the range of operation and consist-
10.5.1 For systems that use a microprocessor or computer
ing of nitrogen type and matrix similar to samples to be
system for data collection and calibration curve generation, the
analyzed. There shall be a minimum of two calibration
calibration curve shall be based on the linear regression of a
standards in addition to the solvent blank, used to generate the
minimum of three repeat measurements of each calibration
calibration curve.
standard.
10.2 Determine the volume or mass of the material to be
10.5.2 For those detectors not equipped with a micropro-
analyzed by using one of the volumetric or gravimetric
cessor or computer system for generating a calibration curve,
methods described below.
constructastandardcurveasfollows.Repeatthedetermination
10.2.1 Volumetric measurement of the injected material is
of each calibration standard and the blank three times to
obtained by filling the syringe to the 80 % level, retracting the
determine the average net response for each. Construct a curve
plunger so that the lower liquid meniscus falls on the 10 %
plotofdetectorresponse(integrationcounts)versusnanograms
scale mark, and recording the volume of liquid in the syringe.
of nitrogen injected and apply the best straight line fit through
After the material has been injected, again retract the plunger
the plotted data.
so that the lower liquid meniscus falls on the 10 % scale mark
10.6 The response curve should be linear with a minimum
and record the volume of liquid in the syringe. The difference
R of 0.999. The intercept should not be forced through zero.
between the two volume readings is the volume of material
The calibration curve shall be checked each day that the
injected. instrument is used (see Section 13).
10.2.2 Alternatively, an automatic sampling and injection
11. Procedure
device may be used to volumetrically inject a reproducible
11.1 Obtain a test specimen using the procedure in Section
volume of the material into the furnace.
8.The nitrogen concentration in the test specimen must be less
10.2.3 Gravimetric measurement of the injected material is
than the concentration of the highest standard used in the
obtained by weighing the syringe before and after injection to
calibration. Injection volumes ranging from 3 to 100 µL are
determine the amount of material injected. This procedure
acceptabledependingontheinstrumentbeingused.Thesizeof
provides greater precision than the volumetric procedure,
the injected sample shall be similar to the size of the injected
provided a balance with a precision of at least 60.01 mg is
standards used for calibration.
used.
11.2 Flush a clean microlitre syringe several times with the
10.3 To introduce the sample into the furnace, insert the
sample to be determined, and introduce it into the furnace
syringeneedlethroughtheinletseptumuptothesyringebarrel
using the procedure outlines in 10.2-10.4 (depending on
and inject the sample or standard at a uniform rate as specified
whether a boat inlet system is being used). For samples with
bytheinstrumentmanufacturer(typically0.2to1.0µL/s).Rate
total nitrogen concentration in the range 1 to 100 mg/kg,
of injection is dependent on such factors as viscosity, hydro-
sample sizes injected are typically up to 10 µL. For samples
carbon type, and nitrogen concentration. Each user must adopt
with total nitrogen concentration less than 1 mg/kg, injected
a method whereby a consistent and uniform injection rate is
sample size can be up to 100 µL. Follow the instrument
ensured. An automatic sampling and injection device may be
manufacturer’s recommendation on sample size based on type
used to introduce the material at a reproducible rate. If an
of sample and level of nitrogen present.
automatic sampling and injection device is not being used,
11.3 To obtain one result, measure each test specimen a
determine the quantity of material injected using either 10.2.1
minimum of three times and calculate the average detector
(volumetric injection procedure) or 10.2.3 (gravimetric injec-
response.
tion procedure).
12. Calculation
NOTE 4—For the most consistent injection rate and best analytical
12.1 For samples introduced volumetrically (10.2
...
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