1、AMERICAN NATIONAL ANSl/ASTM D 2567-68(Reapproved 1978)STANDARD Standard Method for MOLECULAR DISTRIBUTION ANALYSIS FOR MONOALKYLBENZENES BY MASS SPECTROMETRY 1 This Standard is issued under the fixed designation D 2567;the n-umber immediately following the designation indicates the year of original
2、adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapprovaL 1.Scope I.I This method2 is intended for applica-tion to detergent alkylate systems that have a typical aromatics content of 99 percent or more and that have a carbon number ra
3、nge of C12 to C,z.The method is applicable to other systems of monoalkylbenzenes if it is known that other molecular species that contribute to the CnHn-?and C,.H,._.peaks are not present.The method has been cooperatively tested over a monoalkylbenzene carbon number range of C 12 to C2,.2.Summary of
4、 Method 2.1 Samples are analyzed by mass spec-trometry using peak intensities of the C,.H 2n-1 and C,.H2,._8 series between m/e(mass number)161 and 162 and m/e 581 and 582.Calculations are made from calibration data given for each of the various individual m/es.Results are normalized to a total alky
5、lben-zene content of 100 percent and are expressed in liquid volume percent.3.Definitions and Symbols 3.1 K Correction Factors-The factor includes correction for heavy,isotopic abun-dances of carbon and hydrogen plus a calibra-tion value based upon C,.H,_7 peaks.Sepa-rate numerical values are given
6、for each carbon number.3.2 Intensity Factor-The intensity factor,I1,is the reciprocal of relative total ionization sensitivities.3.3 Parent or Molecular Ion Peak,P.3.4 Parent or Molecular Ion Peak Less One Mass Unit,P-I.4.Apparatus 4.1 Mass Spectrometer-Any mass spec-trometer capable of performance
7、described both herein and in ASTM Recommended Practice E 137,for Evaluation of Mass Spec-trometers for Use in Chemical Analysis.4.2 Sample Inlet System-Any inlet system operated at an elevated temperature(300 to 350 C)permitting the introduction of the sample without loss,contamination,or change in
8、composition.4.3 Microburet or Constant-Volume Pipet.5.Procedure 5.1 Use a single magnetic field to permit a scan over the mass range of 161 to 582.S.2 Use an ionization voltage of 70 eV and a measured ionizing current in the range from 10 to SO A.S.3 Background-Samples should pump out so that peaks
9、remaining are less than 0.l percent of those on the previous _spectrum.5.4 Generally,mass spectrometers are in continuous operation and should require no additional preparation prior to loading sam-ples.If the mass spectrometer has to be turned on,it will be necessary to check its operation accordin
10、g to the manufacturers This method is under the jurisdiction of ASTM Com-mittee 0-2 on Petroleum Products and Lubricants.Current edition effective Sept.L3,1968.Originally is-sued 1966.Replaces D 2567-66 T.In!968,this method was adopted as standard without revision.Boyer.E.W.,Ford,H.T.,and Hamming,M.
11、C.Rearrangement Technique for Analysis of Alkylbenzencs by Mass Spectrometry.Analytical Chemistry,A NCH A Vl 35.1963,p.1168.Annual Book of ASTM Standards,Part 42.488-NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)
12、for the latest information.instructions to ensure operational stability.The mass spectrometer should then meet the requirements given in 5.1 through 5.3.5.5 Obtaining the Mass Spectrum-Intro-duce sufficient sample by means of a micro-buret or constant-volume pipet and then scan and record a spectrum
13、 of usable intensities over the mass range of the sample.A volume of approximately l l is frequently satisfac-tory.6.Calculations 6.1 Read the peaks in the CnH2._7 and C,H2,_8 series starting with m/e 161 and 162.6.2 Correct intensities of C.H-peaks using correction values K given in Table 3 of the
14、supplement for corresponding intensi-ties of C.H2,_1 peaks,that is,C.H2._6-(C,H2n-1 x K)=corrected C,H2n-6.3 Multiply corrected C,H2-intensities derived in accordance with 6.2 by corre-sponding intensity factors(11)given in Table Al.6.4 Numerical values derived in accordance with 6.3 shall be normal
15、ized to a total alkyl-benzene content of I 00 percent.Results shatl be expressed as volume percentages.7.Precisioa 7.1 The following criteria should be used for judging the acceptability of results for D 2567 monoalkylbenzenes of the composition indi-cated(95 percent confidence):7.1.1 Repeatability-
16、Duplicate results by the same laboratory should be considered suspect if the two results differ by more than the amounts shown in Table I.The data given in Table I are illustrative in that the statistical data are based only on alkyl carbon numbers C 10 through C is for one typical sample of the ten cooperatively tested.Only seven companies out of ten re ported duplicate data.Carbon numbers below C10 and above C16 were purposely omitted because of the injection of bias due to the rounding off of
