1、Designation: D4629 17Designation: 379/88Standard Test Method forTrace Nitrogen in Liquid Hydrocarbons by Syringe/InletOxidative Combustion and Chemiluminescence Detection1This standard is issued under the fixed designation D4629; the number immediately following the designation indicates the year of
2、original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Departm
3、ent of Defense.1. Scope*1.1 This test method covers the determination of the tracetotal nitrogen naturally found in liquid hydrocarbons boiling inthe range from approximately 50 C to 400 C, with viscositiesbetween approximately 0.2 cSt and 10 cSt (mm2/s) at roomtemperature. This test method is appli
4、cable to naphthas,distillates, and oils containing 0.3 mg kg to 100 mg kg totalnitrogen. For liquid hydrocarbons containing more than100 mg kg total nitrogen, Test Method D5762 can be moreappropriate. This test method has been successfully applied,during interlaboratory studies, to sample types outs
5、ide therange of the scope by dilution of the sample in an appropriatesolvent to bring the total nitrogen concentration and viscosityto within the range covered by the test method. However, it isthe responsibility of the analyst to verify the solubility of thesample in the solvent and that direct int
6、roduction of the dilutedsample by syringe into the furnace does not cause low resultsdue to pyrolysis of the sample or solvent in the syringe needle.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not
7、purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See 6.2, 6.4, 6.5,6.9, and Section 7.1.4
8、This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Tra
9、de (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1298 Test Method for Density, Relative Density, or APIGravity of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer MethodD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD5762
10、Test Method for Nitrogen in Liquid Hydrocarbons,Petroleum and Petroleum Products by Boat-Inlet Chemi-luminescenceD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3. Summary of Test Method3.1 The sample of liq
11、uid petroleum hydrocarbon is intro-duced either by syringe or boat inlet system, into a stream ofinert gas (helium or argon). The sample is vaporized andcarried to a high temperature zone where oxygen is introducedand organically bound nitrogen is converted to nitric oxide(NO). The NO contacts ozone
12、, and is converted to excitednitrogen dioxide (NO2). The light emitted as the excited NO2decays is detected by a photomultiplier tube and the resultingsignal is a measure of the nitrogen contained in the sample.4. Significance and Use4.1 Some process catalysts used in petroleum and chemicalrefining
13、may be poisoned when even trace amounts of nitrog-enous materials are contained in the feedstocks. This testmethod can be used to determine bound nitrogen in processfeeds and may also be used to control nitrogen compounds infinished products.1This test method is under the jurisdiction of ASTM Commit
14、tee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Dec. 15, 2017. Published February 2018. Originallyapproved in 1986. Last previous edition approved in 2017 as D4629 12 (2017).DOI: 10.1520/
15、D4629-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of
16、this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelop
17、ment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Apparatus5.1 Furnace, electric, held at a temperature sufficient tovolatilize and pyrolyze all of the sample and oxidize theorganically bound nitrogen to
18、 NO. Furnace temperature(s)shall be as recommended by the manufacturer (typicallyaround 1000 C).5.2 Combustion Tube, fabricated to meet the instrumentmanufacturers specifications.5.3 Drier TubeThe reaction products include water vaporthat must be eliminated prior to measurement by the detector.This
19、can be accomplished with a magnesium perchlorateMg(ClO4)2scrubber or a membrane drying tube (permeationdrier), or by whatever other means the instrument manufacturerspecifies as appropriate for the instrument being used.5.4 Chemiluminescent Detector, capable of measuring lightemitted from the reacti
20、on between NO and ozone.5.5 Totalizer, having variable attenuation, and capable ofmeasuring, amplifying, and integrating the current from thechemiluminescent detector. A built in microprocessor or at-tached computer system may perform these functions.5.6 Micro-litre Syringe, of 5 L, 10 L, 25 L, 50 L
21、, or250 L capacity capable of accurately delivering micro-litrequantities is required. The needle should be long enough toreach the hottest portion of the inlet section of the furnacewhen injecting the sample. The syringe may be part of anautomatic sampling and injection device used with the instru-
22、ment.5.7 Strip Chart Recorder (Optional).5.8 Sample Inlet SystemOne of the following must beused:5.8.1 Manually Operated Syringe.5.8.2 Syringe, with a constant rate injector system, capableof delivering a sample at a precisely controlled rate.5.8.3 Boat Inlet System, to facilitate analysis of sample
23、s thatwould react with the syringe or syringe needle. The pyrolysistube for boat inlet use may require specific construction topermit insertion of a boat fully into the inlet section of thefurnace. The boat inlet system external to the furnace may becooled to a temperature below room temperature to
24、aid indissipating the heat from the boat when it is removed from thefurnace. Cooling the boat inlet system may also reduce thechances of the sample combusting in the boat before introduc-tion into the furnace and may be necessary when runningvolatile samples such as naphtha using a boat inlet system
25、.5.9 Quartz Insert Tube (Optional), may be packed withcupric oxide (CuO) or other oxidation catalyst as recom-mended by the instrument manufacturer, to aid in completingoxidation. This is inserted into the exit end of the pyrolysistube.5.10 Vacuum System (Optional), The chemiluminescencedetector may
26、 be equipped with a vacuum system to maintainthe reaction cell at reduced pressure (typically 20 mm to25 mm Hg). This can improve the signal to noise ratio of thedetector.5.11 Analytical Balance (Optional), with a precision of60.01 mg.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall be
27、used in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society,3where such specifications are available. Other grades may beused, provided it is first ascertained that the reag
28、ent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Magnesium Perchlorate Mg(ClO4)2, for drying productsof combustion (if permeation drier is not used.) (WarningStrong oxidizer, irritant.)6.3 Inert Gas, argon or helium, ultra-high purity grade(U
29、HP).6.4 Oxygen, (99.8 % or better, 99.996 % is recommended).(WarningVigorously accelerates combustion.)6.5 Solvents, for diluting and matrix matching such as,toluene, isooctane, xylene, acetone, cetane. (Other solventssimilar to those occurring in samples to be analyzed are alsoacceptable). Solvents
30、 should contain less than 0.1 g N/mL.(WarningFlammable solvents.)6.6 Nitrogen Stock Solution, 1000 g N/mL, Prepare a stocksolution by accurately weighing approximately 1.195 g ofcarbazole or 0.565 g of pyridine to the nearest milligram, intoa tared 100 mL volumetric flask (see 6.6.1). Fifteen millil
31、itresof acetone may then be added when using carbazole to helpdissolve it. Dilute to volume with the selected solvent. Calcu-late the exact concentration of the stock solution based on theactual mass of pyridine or carbazole used and corrected for anyknown purity factors for the specific lot of pyri
32、dine orcarbazole. This stock may be further diluted to desired nitrogenconcentrations.6.6.1 Calibration standards from commercial sources maybe used if they conform to the requirements of the test method.NOTE 1Pyridine should be used with low boiling solvents (220 C).NOTE 3Working standards should b
33、e remixed on a regular basisdepending upon frequency of use and age. Typically, standards have auseful life of about 3 months, and should be refrigerated when not beingused.6.7 Cupric Oxide Wire, as recommended by instrumentmanufacturer.6.8 Quartz Wool (optional), or other suitable absorbentmaterial
34、 that is stable and capable of withstanding temperaturesinside the furnace (Note 4).NOTE 4Materials meeting the requirements in 6.8 are recommendedto be used in sample boats to provide a more uniform injection of the3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Soci
35、ety, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.
36、D4629 172sample into the boat by wicking any remaining drops of the sample fromthe tip of the syringe needle prior to introduction of the sample into thefurnace. Consult instrument manufacturer recommendations for furtherguidance.6.9 Pyridine. (WarningFlammable, irritant.)6.10 Carbazole.7. Hazards7.
37、1 High temperature is employed in this test method.Exercise care when using flammable materials near the pyroly-sis furnace.8. Sampling8.1 To preserve volatile components, which may be in somesamples, do not uncover samples any longer than necessary.Analyze samples as soon as possible after taking f
38、rom the bulksupplies to prevent loss of nitrogen or contamination due toexposure or contact with sample container.9. Assembly Apparatus9.1 Assemble apparatus in accordance with manufacturersinstructions.9.2 Adjust the gas flows and the pyrolysis temperature asrecommended by the instrument manufactur
39、er.10. Calibration and Standardization10.1 Prepare a series of calibration standards from the stocksolution (see 6.6) covering the range of operation and consist-ing of nitrogen type and matrix similar to samples to beanalyzed. There shall be a minimum of two calibrationstandards in addition to the
40、solvent blank, used to generate thecalibration curve.10.2 Determine the volume or mass of the material to beanalyzed by using one of the volumetric or gravimetricmethods described below.10.2.1 Volumetric measurement of the injected material isobtained by filling the syringe to the 80 % level, retrac
41、ting theplunger so that the lower liquid meniscus falls on the 10 %scale mark, and recording the volume of liquid in the syringe.After the material has been injected, again retract the plungerso that the lower liquid meniscus falls on the 10 % scale markand record the volume of liquid in the syringe
42、. The differencebetween the two volume readings is the volume of materialinjected.10.2.2 Alternatively, an automatic sampling and injectiondevice may be used to volumetrically inject a reproduciblevolume of the material into the furnace.10.2.3 Gravimetric measurement of the injected material isobtai
43、ned by weighing the syringe before and after injection todetermine the amount of material injected. This procedureprovides greater precision than the volumetric procedure,provided a balance with a precision of at least 60.01 mg isused.10.3 To introduce the sample into the furnace, insert thesyringe
44、needle through the inlet septum up to the syringe barreland inject the sample or standard at a uniform rate as specifiedby the instrument manufacturer (typically 0.2 L s to1.0 L s). Rate of injection is dependent on such factors asviscosity, hydrocarbon type, and nitrogen concentration. Eachuser mus
45、t adopt a method whereby a consistent and uniforminjection rate is ensured. An automatic sampling and injectiondevice may be used to introduce the material at a reproduciblerate. If an automatic sampling and injection device is not beingused, determine the quantity of material injected using either1
46、0.2.1 (volumetric injection procedure) or 10.2.3 (gravimetricinjection procedure).NOTE 5For the most consistent injection rate and best analyticalresults, a constant rate injection unit or automatic sampling and injectiondevice may be helpful. Coke formation at the outlet of the combustiontube may i
47、ndicate too rapid of an injection rate. Consult manufacturer forrecommendations.NOTE 6With direct injection below 5 mg kg of nitrogen, the needleseptum blank may become increasingly important. Error due to this can beavoided by inserting the syringe needle into the hot inlet and allowing theneedle-s
48、eptum blank to dissipate before injecting the sample.10.4 If a boat inlet system is used, then the material to beanalyzed is injected into a quartz boat using one of theprocedures described in 10.2.1, 10.2.2,or10.2.3 and the quartzboat is moved into the hot portion of the combustion tube.Refer to th
49、e manufacturers instructions for selecting the rate ofboat movement into the furnace and boat residence time in thehot portion of the combustion tube.10.5 Calibration curves shall be generated in one of thefollowing manners depending on the capability of the instru-mentation used.10.5.1 For systems that use a microprocessor or computersystem for data collection and calibration curve generation, thecalibration curve shall be based on the linear regression of aminimum of three repeat measurements of each calibrationstandard.10.5.2 For those detectors
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