ASTM_D_2425_-_21.pdf

Designation:D242521Standard Test Method forHydrocarbon Types in Middle Distillates by MassSpectrometry1This standard is issued under the fixed designation D2425;the number immediately following 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.1.Scope*1.1 This test method covers an analytical scheme using themass spectrometer to determine the hydrocarbon types presentin conventional and synthesized hydrocarbons that have aboiling range of 160 C to 343 C(320 F to 650 F),5%to95%by volume as determined by Test Method D86.Sampleswith average carbon number value of paraffins between C12and C16and containing paraffins from C10and C18can beanalyzed.Eleven hydrocarbon types are determined.Theseinclude:paraffins,noncondensed cycloparaffins,condenseddicycloparaffins,condensed tricycloparaffins,alkylbenzenes,indans or tetralins,or both,CnH2n-10(indenes,etc.),naphthalenes,CnH2n-14(acenaphthenes,etc.),CnH2n-16(acenaphthylenes,etc.),and tricyclic aromatics.NOTE1This test method was developed on Consolidated Electrody-namics Corporation Type 103 Mass Spectrometers.Operating parametersfor users with a Quadrupole Mass Spectrometer are provided.1.2 This test method is intended for use with full boilingrange products that contain no significant olefin content.Biodiesel(FAME components)could interfere with theseparation of the sample and the characteristic mass fragmentsof FAME compounds are not defined in the procedure.Hydrocarbons containing tertiary carbon fragments,some-times found in synthetic aviation fuels,will interfere with thecharacteristic mass fragments of paraffins and result in a false,elevated cycloparaffin content.NOTE2“No significant olefin content”for this method means 0.25)they willinterfere with the spectral peaks used for the hydrocarbon-typecalculation.7.Sample Separation7.1 Sample is to be separated into saturate and aromaticfractions.Liquid chromatography procedures based on TestMethods D2549,D1319,and D6379 have been used.NOTE3Test Method D2549 is presently applicable only to sampleshaving 5%points of 232 C(450 F)or greater.Guidance on using TestMethods D1319 and D6379 is provided in the Annexes.PROCEDURE AMAGNETIC SECTOR SPECTROMETER8.Apparatus8.1 Mass SpectrometerThe suitability of the mass spec-trometer to be used with this method of analysis shall beproven by performance tests described herein.8.2 Sample Inlet SystemAny inlet system permitting theintroduction of the sample without loss,contamination,orchange in composition.To fulfill these requirements it will benecessary to maintain the system at an elevated temperature inthe range of 125 C to 325 C and to provide an appropriatesampling device.8.3 Microburet or Constant-Volume Pipet.9.Calibration9.1 Calibration coefficients are attached which can be useddirectly provided:9.1.1 Repeller settings are adjusted to maximize the m/e+226 ion of n-hexadecane.9.1.2 Amagnetic field is used that will permit scanning fromm/e+40 to 292.9.1.3 An ionization voltage of 70 eV and ionizing currentsin the range 10 A to 70 A are used.NOTE4The calibration coefficients were obtained for ion sourceconditions such that the 67/71 ratio for n-hexadecane was 0.26/1.Thecooperative study of this test method indicated an acceptable range for this ratio between 0.2/1 to 0.30/1.10.Performance Test10.1 Generally,mass spectrometers are in continuous op-eration and should require no additional preparation beforeanalyzing samples.If the spectrometer has been turned on onlyrecently,it will be necessary to check its operation in accor-dance with this method and instructions of the manufacturer toensure stability before proceeding.10.2 Mass Spectral BackgroundSamples in the carbonnumber range C10to C18should pump out so that less thanD2425 2120.1%of the two largest peaks remain.For example,back-ground peaks from a saturate fraction at m/e+69 and 71 shouldbe reduced to less than 0.1%of the corresponding peaks in themixture spectrum after a normal pump out time of 2 min to5 min.11.Mass Spectrometric Procedure11.1 Obtaining the Mass Spectrum for Each Chromato-graphic FractionUsing a microburet or constant-volumepipet,introduce sufficient sample through the inlet sample togive a pressure of 2 Pa to 4 Pa(15 mtorr to 30 mtorr)in theinlet reservoir.(WarningHydrocarbon samples of this boil-ing range are combustible.)Record the mass spectrum of thesample from m/e+40 to 292 using the instrument conditionsoutlined in 9.1.1 9.1.3.PROCEDURE BQUADRUPOLE SPECTROMETER12.Apparatus12.1 Mass SpectrometerMass spectrometers providedwith a quadrupole as ion separator and use electron impact at70 ev have been used.12.2 Sample Inlet SystemAny inlet system permitting theintroduction of the sample without loss,contamination,orchange in composition.Separation of components is notrequired.12.2.1 For sample