# ASTM D2425-17

Designation: D2425 − 17Standard 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 virgin middle distillates 204 °C to 343 °C (400 °F to 650 °F)boiling range, 5 % to 95 % by volume as determined by TestMethod D86. Samples with average carbon number value ofparaffins between C12and C16and containing paraffins fromC10and C18can be analyzed. Eleven hydrocarbon types aredetermined. These include: paraffins, noncondensedcycloparaffins, condensed dicycloparaffins, condensedtricycloparaffins, alkylbenzenes, indans or tetralins, or both,CnH2n-10(indenes, etc.), naphthalenes, CnH2n-14(acenaphthenes, etc.),CnH2n-16(acenaphthylenes, etc.), and tricyclic aromatics.NOTE 1—This test method was developed on Consolidated Electrody-namics Corporation Type 103 Mass Spectrometers.1.2 The values stated in SI units are to be regarded as thestandard.1.2.1 Exception—The inch-pound units given in parenthesesare for information only.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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.For a specific warning statement, see 10.1.1.4 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 Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D86 Test Method for Distillation of Petroleum Products andLiquid Fuels at Atmospheric PressureD2549 Test Method for Separation of Representative Aro-matics and Nonaromatics Fractions of High-Boiling Oilsby Elution Chromatography3. Terminology3.1 The summation of characteristic mass fragments aredefined as follows:∑71 (paraffins) = total peak height of m/e+71 + 85.∑67 (mono or noncondensed polycycloparaffins, orboth) = total peak height of m/e+67+68+69+81+82+83+96+97.∑123 (condensed dicycloparaffins) = total peak height ofm/e+123 + 124 + 137 + 138 + ··· etc. up to 249 + 250.∑149 (condensed tricycloparaffins) = total peak height ofm/e+149 + 150 + 163 + 164 + ··· etc. up to 247 + 248.∑91 (alkyl benzenes) = total peak height of m/e+91 + 92 + 105 + 106 + ··· etc. up to 175 + 176.∑103 (indans or tetralins, or both) = total peak height ofm/e+103 + 104 + 117 + 118 + ··· etc. up to 187 + 188.∑115 (indenes or CnH2n-10, or both) = total peak height ofm/e+115 + 116 + 129 + 130 + ··· etc. up to 185 + 186.128 (naphthalene) = total peak height of m/e+128.∑141 (naphthalenes) = total peak height of m/e+141 + 142 + 155 + 156 + ··· etc. up to 239 + 240.∑153 (acenaphthenes or CnH2n-14, or both) = total peakheight of m/e+153 + 154 + 167 + 168 + ··· etc. up to251 + 252.∑151 (acenaphthylenes or CnH2n-16, or both) = total peakheight of m/e+151 + 152 + 165 + 166 + ··· etc. up to249 + 250.∑177 (tricyclic aromatics) = total peak height of m/e+177 + 178 + 191 + 192 + ··· etc. up to 247 + 248.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility ofSubcommittee D02.04.0M on Mass Spectroscopy.Current edition approved Oct. 1, 2017. Published November 2017. Originallyapproved in 1965. Last previous edition approved in 2009 as D2425 – 04 (2009).DOI: 10.1520/D2425-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of 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 theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14. Summary of Test Method4.1 Samples are separated into saturate and aromatic frac-tions by Test Method D2549, and each fraction is analyzed bymass spectrometry. The analysis is based on the summation ofcharacteristic mass fragments to determine the concentration ofhydrocarbon types. The average carbon numbers of the hydro-carbon types are estimated from spectral data. Calculations aremade from calibration data dependent upon the average carbonnumber of the hydrocarbon types. The results of each fractionare mathematically combined according to their mass fractionsas determined by the separation procedure. Results are ex-pressed in mass percent.NOTE 2—Test Method D2549 is presently applicable only to sampleshaving 5 % points of 232 °C (450 °F) or greater.5. Significance and Use5.1 Aknowledge of the hydrocarbon composition of processstreams and petroleum products boiling within the range of400 °F to 650 °F (204 °C to 343 °C) is useful in following theeffect of changes in process variables, diagnosing the source ofplant upsets, and in evaluating the effect of changes incomposition on product performance properties.6. Interferences6.1 Nonhydrocarbon types, such as sulfur and nitrogen-containing compounds, are not included in the matrices for thistest method. If these nonhydrocarbon types are present to anylarge extent, (for example, mass percent sulfur 0.25) they willinterfere with the spectral peaks used for the hydrocarbon-typecalculation.7. Apparatus7.1 Mass Spectrometer—The suitability of the mass spec-trometer to be used with this method of analysis shall beproven by performance tests described herein.7.2 Sample Inlet System—Any 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.7.3 Microburet or Constant-Volume Pipet.8. Calibration8.1 Calibration coefficients are attached which can be useddirectly provided:8.1.1 Repeller settings are adjusted to maximize the m/e+226 ion of n-hexadecane.8.1.2 Amagnetic field is used that will permit scanning fromm/e+40 to 292.8.1.3 An ionization voltage of 70 eV and ionizing currentsin the range 10 µA to 70 µA are used.NOTE 3—The 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.NOTE 4—Users of instruments other than Consolidated Electrodynam-ics Corporation Type 103 Mass Spectrometers may have to develop theirown operating parameters and calibration data.9. Performance Test9.1 Generally, mass spectrometers are in continuous opera-tion 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.9.2 Mass Spectral Background—Samples in the carbonnumber range C10to C18should pump out so that less than0.1 % 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 to 5min.10. Mass Spectrometric Procedure10.1 Obtaining the Mass Spectrum for Each Chromato-graphic Fraction—Using 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. (Warning—Hydrocarbon 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 8.1.1 – 8.1.3.11. Calculations and Report11.1 Aromatic Fraction—Read peak heights from the recordmass spectrum corresponding to m/e+ratios of 67 to 69, 71, 81to 83, 85, 91, 92, 96, 97, 103 to 106, 115 to 120, 128 to 134,141 to 148, 151 to 162, 165 to 198, 203 to 212, 217 to 226, 231to 240, 245, 246, 247 to 252.Find:(71 5 71185 (1)(67 5 67168169181182183196197 (2)TABLE 1 Parent Ion Isotope Factors and Mole SensitivitiesCarbon No. m/eIsotopeFactor, K1MoleSensitivity, K2Alkylbenzenes10 134 0.1101 8511 148 0.1212 6312 162 0.1323 6013 176 0.1434 5714 190 0.1545 5415 204 0.1656 5116 218 0.1767 4817 232 0.1878 4518 246 0.1989 42L1L2Naphthalenes11 142 0.1201 19412 156 0.1314 16613 170 0.1425 15014 184 0.1536 15015 198 0.1647 15016 212 0.1758 15017 226 0.1871 15018 240 0.1982 150D2425 − 172(91 5( N50N56@~91114N!1~92114N!# (3)(103 5( N50N56@~103114N!1~104114N!# (4)(115 5( N50N55@~115114N!1~116114N!# (5)(141 5( N50N57@~141114N!1~142114N!# (6)(153 5( N50N57@~153114N!1~154114N!# (7)(151 5( N50N57@~151114N!1~152114N!# (8)(177 5( N50N55@~177114N!1~178114N!# (9)11.2 Calculate the mole fraction at each carbon number ofthe alkylbenzenes for n =10ton = 18 as follows:µn5@Pm2 Pm21~K1!#/K2(10)where:µn= mole fraction of each alkylbenzene as representedby n which indicates the number of carbons in eachmolecular species.m = molecular weight of the alkylbenzene beingcalculated,m−1 = molecular weight minus 1,P = polyisotopic mixture peak at m, m −1,K1= isotopic correction factor (see Table 1), andK2= mole sensitivity for n (see Table 1).NOTE 5—This step of calculation assumes no mass spectral patterncontributions from other hydrocarbon types to the parent and parent-1peaks of the alkylbenzenes. Selection of the lowest carbon number 10 isbased upon the fact that C9alkylbenzenes boil below 204°C (400°F) andtheir concentration can be considered negligible.11.3 Find the average carbon number of the alkylbenzenes,A, in the aromatic fraction as follows:A 5~(n510n518n 3 µn!/~(n510n518µn!(11)11.4 Calculate the mole fraction at each carbon number ofthe naphthalenes for n =11ton = 18 as follows:xn5@Pm2 Pm21~L1!#/L2(12)where:xn= mole fraction of each naphthalene as represented byn which indicates the number of carbons in eachmolecular species,m = molecular weight of the naphthalenes beingcalculated,m−1 = molecular weight minus 1,P = polyisotopic mixture peak at m, m −1,L1= isotopic correction factor (see Table 1), andL2= mole sensitivity for n (see Table 1).NOTE 6—This step of calculation assumes no mass spectral patterncontributions to the parent and parent-1 peaks of the naphthalenes. Theconcentration of naphthalene itself at a molecular weight of 128 shall bedetermined separately from the polyisotopic peak at m/e+128 in thematrix calculation. The average carbon number for the naphthalenes shallbe calculated from carbon number 11 (molecular weight 142) to 18(molecular weight 240).11.5 Find the average carbon number of the naphthalenes,B, in the aromatic fraction as follows:B 5~(n511n518nxn!/~(n511n518xn!(13)11.6 Selection of pattern and sensitivity data for matrixcarbon number of the types present. The average carbonnumber of the paraffins and cycloparaffins (∑71 and ∑67,respectively) are related to the calculated average carbon of thealkylbenzenes (11.3), as shown in Table 2. Both ∑71 and ∑67are included in the aromatic fraction matrix to check onpossible overlap in the separation. The other types present,represented by ∑’s 103, 115, 153, and 151, are usuallyrelatively low in concentration so that their parent ions areaffected by other types present. The calculation of their averagecarbon number is not straight forward. Therefore, their averagecarbon numbers are estimated by inspection of the aromaticspectrum. Generally, their average carbon numbers may betaken to be equivalent to that of the naphthalenes, or to theclosest whole number thereof, as calculated in 11.5. Theaverage carbon number of tricyclic aromatics ∑177 has to be atleast C14and in full boiling range middle distillates C14may beused to represent the ∑177 types carbon number. From thecalculated and estimated average carbon numbers of thehydrocarbon types, a matrix for the aromatic fraction is set upusing the calibration data given in Table 3.Asample matrix forthe aromatic fraction is shown in Table 4. The matrix calcula-tions consist in solving a set of simultaneous linear equations.The pattern coefficients are listed in Table 3. The constants arethe ∑ values determined from the mass spectrum. Secondapproximation solutions are of sufficient accuracy. If manyanalyses are performed using the same type of a matrix, thematrix may be inverted for simpler, more rapid desk calcula-tion. Matrices may also be programmed for automatic com-puter operations. The results of matrix calculations are con-verted to mass fractions by dividing by mass sensitivity. Themass fractions are normalized to the mass percent of thearomatic fraction, as determined by the separation procedure.11.7 Saturate Fraction—Read peak at heights from therecord of the mass spectrum corresponding to m/e+ratios of 67to 69, 71, 81 to 83, 85, 91, 92, 96, 97, 105, 106, 119, 120, 123,124, 133, 134, 137, 138, 147 to 152, 161 to 166, 175 to 180,191 to 194, 205 to 208, 219 to 222, 233 to 236, 247 to 250.Find:(71 5 71185 (14)(67 5 67168169181182183196197 (15)(123 5( N50N59@~123114N!1~124114N!# (16)(149 5( N50N57@~149114N!1~150114N!# (17)(91 5( N50N56@~91114N!1~92114N!# (18)11.8 Selection of the pattern and sensitivity data for matrixcalculation is dependent upon the average carbon number ofthe types present. The average carbon number of the paraffinsand cycloparaffin types (∑’s 71, 69, 123, and 149), are relatedTABLE 2 Relationship Between Average Carbon Numbers ofAlkylbenzenes, Paraffins, and CycloparaffinsAlkylbenzenes Paraffin and CycloparaffinAverage Carbon No. Average Carbon No.10 1111 1212 1313 15 (14.5)14 16 (15.5)D2425 − 173to the calculated average carbon number of the alkylbenzenesof the aromatic fraction (11.3), as shown in Table 2. The ∑91is included in the saturate fraction as a check on the efficiencyof the separation procedure. The pattern and sensitivity data forthe ∑91 are based on the calculated or estimated averagecarbon number from the mass spectra of the aromatic fraction(see 11.3). From the determined average carbon numbers of thehydrocarb