1、Designation: D 4629 08Designation: 379/88An American National StandardStandard Test Method forTrace Nitrogen in Liquid Petroleum Hydrocarbons bySyringe/Inlet Oxidative Combustion and ChemiluminescenceDetection1This standard is issued under the fixed designation D 4629; the number immediately followi
2、ng the designation indicates the year oforiginal 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
3、 for use by agencies of the Department 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 to 400C, with viscositiesbetween approximately 0.2 and 10 cSt (mm2/s) at roomtemperatur
4、e. This test method is applicable to naphthas, distil-lates, and oils containing 0.3 to 100 mg/kg total nitrogen. Forliquid hydrocarbons containing more than 100 mg/kg totalnitrogen, Test Method D 5762 can be more appropriate. Thistest method has been successfully applied, during interlabora-tory st
5、udies, to sample types outside the range of the scope bydilution of the sample in an appropriate solvent to bring thetotal nitrogen concentration and viscosity to within the rangecovered by the test method. However, it is the responsibility ofthe analyst to verify the solubility of the sample in the
6、 solventand that direct introduction of the diluted sample by syringeinto the furnace does not cause low results due to pyrolysis ofthe 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.
7、1.3 This standard does not 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,
8、6.5,6.9, and Section 7.2. Referenced Documents2.1 ASTM Standards:2D 1298 Test Method for Density, Relative Density (SpecificGravity), or API Gravity of Crude Petroleum and LiquidPetroleum Products by Hydrometer MethodD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density Me
9、terD 5762 Test Method for Nitrogen in Petroleum and Petro-leum Products by Boat-Inlet ChemiluminescenceD 6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3. Summary of Test Method3.1 The sample of liquid petro
10、leum 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, and is
11、converted to excitednitrogen oxide (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 may be pois
12、oned when even trace amounts of nitrog-enous materials are contained in the feedstocks. This test1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved
13、 July 1, 2008. Published August 2008. Originallyapproved in 1986. Last previous edition approved in 2007 as D 462902(2007).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, re
14、fer to the standards Document Summary page onthe ASTM website.1*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.method can be used to determine bound nitrogen in process
15、feeds and may also be used to control nitrogen compounds infinished products.5. Apparatus5.1 Furnace, electric, held at a temperature sufficient tovolatilize and pyrolyze all of the sample and oxidize theorganically bound nitrogen to NO. Furnace temperature(s)shall be as recommended by the manufactu
16、rer (typicallyaround 1000C).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 can be accomplished with a magnesium perchlorateMg(ClO4)2scrubber or
17、 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 reaction between NO and ozone.5.5 Totalizer, having variable attenuation,
18、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, 10, 25, 50, or 250 L capacitycapable of accurately delivering micro-litre quantities i
19、s re-quired. The needle should be long enough to reach the hottestportion of the inlet section of the furnace when injecting thesample. The syringe may be part of an automatic sampling andinjection device used with the instrument.5.7 Strip Chart Recorder (Optional).5.8 Sample Inlet SystemOne of the
20、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 samples thatwould react with the syringe or syringe needle. The pyrolysistube for
21、 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 aid indissipating the heat from the boat when it is removed from thefurnace
22、. 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.5.9 Quartz Insert Tube (Optional), may be packed withcupric oxide (CuO) or
23、 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 be equipped with a vacuum system to maintainthe reaction cell at reduced p
24、ressure (typically 20 to 25 mmHg). This can improve the signal to noise ratio of the detector.5.11 Analytical Balance (Optional), with a precision of60.01 mg.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagent
25、s 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 reagent is ofsufficiently high purity to permit its use without lessening theaccu
26、racy 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(UHP).6.4 Oxygen, (99.8 % or better, 99.996 % is recommended).(WarningVigorousl
27、y 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 should contain less than 0.1 g N/mL.(WarningFlammable solvents.)6.6 Nitrogen
28、 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. Fifteen millilitres of acetonemay then be added when using carbazole to help dissolve it.Dilute to volu
29、me with the selected solvent. Calculate the exactconcentration of the stock solution based on the actual mass ofpyridine or carbazole used and corrected for any known purityfactors for the specific lot of pyridine or carbazole. This stockmay be further diluted to desired nitrogen concentrations.NOTE
30、 1Pyridine should be used with low boiling solvents (220C).NOTE 3Working standards should be 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 recommende
31、d by instrumentmanufacturer.6.8 Quartz Wool (optional), or other suitable absorbentmaterial 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
32、 of thesample 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.3Reagent Chemic
33、als, American Chemical Society Specifications , AmericanChemical Society, 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
34、 Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D46290827. Hazards7.1 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 unc
35、over samples any longer than necessary.Analyze samples as soon as possible after taking from 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 Adju
36、st the gas flows and the pyrolysis temperature asrecommended by the instrument manufacturer.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 sample
37、s to beanalyzed. There shall be a minimum of two calibrationstandards in addition to the 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 measure
38、ment of the injected material isobtained by filling the syringe to the 80 % level, retracting 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 l
39、iquid meniscus falls on the 10 % scale markand record the volume of liquid in the syringe. 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
40、material into the furnace.10.2.3 Gravimetric measurement of the injected material isobtained 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 a
41、t least 60.01 mg isused.10.3 To introduce the sample into the furnace, insert thesyringe 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 to 1.0 L/s). Rateof injection is dependent on
42、 such factors as viscosity, hydro-carbon type, and nitrogen concentration. Each user must adopta method whereby a consistent and uniform injection rate isensured. An automatic sampling and injection device may beused to introduce the material at a reproducible rate. If anautomatic sampling and injec
43、tion device is not being used,determine the quantity of material injected using either 10.2.1(volumetric injection procedure) or 10.2.3 (gravimetric injec-tion procedure).NOTE 5For the most consistent injection rate and best analyticalresults, a constant rate injection unit or automatic sampling and
44、 injectiondevice may be helpful. Coke formation at the outlet of the combustiontube may indicate 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
45、can beavoided by inserting the syringe needle into the hot inlet and allowing theneedle-septum 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,or1
46、0.2.3 and the quartzboat is moved into the hot portion of the combustion tube.Refer to the 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 thefollo
47、wing 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 cal
48、ibrationstandard.10.5.2 For those detectors not equipped with a micropro-cessor or computer system for generating a calibration curve,construct a standard curve as follows. Repeat the determinationof each calibration standard and the blank three times todetermine the average net response for each. C
49、onstruct a curveplot of detector response (integration counts) versus nanogramsof nitrogen injected and apply the best straight line fit throughthe plotted data.10.6 The response curve should be linear with a minimumR2of 0.999. The intercept should not be forced through zero.The calibration curve shall be checked each day that theinstrument is used (see Section 13).11. Procedure11.1 Obtain a test specimen using the procedure in Section8. The nitrogen concentration in the test specimen must be lessthan the concentration of the highest standard used in thecalibrati
