1、Designation: D 5739 06Standard Practice forOil Spill Source Identification by Gas Chromatography andPositive Ion Electron Impact Low Resolution MassSpectrometry1This standard is issued under the fixed designation D 5739; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the use of gas chromatography andmass spectrom
3、etry to analyze and compare petroleum oil spillsand suspected sources.1.2 The probable source for a spill can be ascertained by theexamination of certain unique compound classes that alsodemonstrate the most weathering stability. To a greater orlesser degree, certain chemical classes can be anticipa
4、ted tochemically alter in proportion to the weathering exposure timeand severity, and subsequent analytical changes can be pre-dicted. This practice recommends various classes to be ana-lyzed and also provides a guide to expected weatheringinduced analytical changes.1.3 This practice is applicable f
5、or moderately to severelydegraded petroleum oils in the distillate range from dieselthrough Bunker C; it is also applicable for all crude oils withcomparable distillation ranges. This practice may have limitedapplicability for some kerosenes, but it is not useful forgasolines.1.4 The values stated i
6、n SI units are to be regarded as thestandard.1.5 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 regula
7、tory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 3325 Practice for Preservation of Waterborne OilSamplesD 3326 Practice for Preparation of Samples for Identifica-tion of Waterborne OilsD 3328 Test Methods for Comparison of Waterborne Petr
8、o-leum Oils by Gas ChromatographyD 3414 Test Method for Comparison of Waterborne Petro-leum Oils by Infrared SpectroscopyD 3415 Practice for Identification of Waterborne OilsD 3650 Test Method for Comparison of Waterborne Petro-leum Oils By Fluorescence AnalysisE 355 Practice for Gas Chromatography
9、Terms and Rela-tionships3. Summary of Practice3.1 The recommended chromatography column is a capil-lary directly interfaced to the mass spectrometer (either qua-drupole or magnetic).3.2 The low-resolution mass spectrometer is operated in thepositive ion electron impact mode, 70 eV nominal.3.3 Mass s
10、pectral data are acquired, stored, and processedwith the aid of commercially available computer-based datasystems.4. Significance and Use4.1 This practice is useful for assessing the source for an oilspill. Other less complex analytical procedures (Test MethodsD 3328, D 3414, D 3650, and D 5037) may
11、 provide all of thenecessary information for ascertaining an oil spill source;however, the use of a more complex analytical strategy may benecessary in certain difficult cases, particularly for significantlyweathered oils. This practice provides the user with a means tothis end.4.1.1 This practice p
12、resumes that a “screening” of possiblesuspect sources has already occurred using less intensivetechniques. As a result, this practice focuses directly on thegeneration of data using preselected targeted compoundclasses. These targets are both petrogenic and pyrogenic andcan constitute both major and
13、 minor fractions of petroleumoils; they were chosen in order to develop a practice that is1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.06 on Methods for Analysis forOrganic Substances in Water.Current edition approved Aug
14、. 15, 2006. Published August 2006. Originallyapproved in 1995. Last previous edition approved in 2000 as D 5739 00.2For 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 t
15、he standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.universally applicable to petroleum oil identification in generaland is also easy to handle and apply. This practice canaccommodate
16、 light oils and cracked products (exclusive ofgasoline) on the one hand, as well as residual oils on the other.4.1.2 This practice provides analytical characterizations ofpetroleum oils for comparison purposes. Certain classes ofsource-specific chemical compounds are targeted in this quali-tative co
17、mparison; these target compounds are both uniquedescriptors of an oil and chemically resistant to environmentaldegradation. Spilled oil can be assessed in this way as beingsimilar or different from potential source samples by the directvisual comparison of specific extracted ion chromatograms(EICs).
18、 In addition, other, more weathering-sensitive chemicalcompound classes can also be examined in order to crudelyassess the degree of weathering undergone by an oil spillsample.4.2 This practice simply provides a means of makingqualitative comparisons between petroleum samples; quantita-tion of the v
19、arious chemical components is not addressed.5. Apparatus5.1 Gas Chromatograph Interfaced to a Mass Spectrometer,with a 70-eV electron impact ionization source. The systemshall include a computer for the control of data acquisition andreduction.5.2 Capillary Column, with a high-resolution, 30 m by0.2
20、5-mm or 0.32-mm inside diameter (0.25-m df) (such as J however, theresulting mass spectra may be distorted significantly so that MS computer searchroutines for the identification of unknowns by comparison to conventionallyacquired mass spectral libraries may be impaired significantly.BAdjust the ent
21、rance lens voltage.CAdjust the ion focus voltage.7.2.2 Retune every 12 h of mass spectrometer operation.7.3 Resolution CheckUnder the instrumental conditionslisted (7.1), pristane and phytane usually display 80 % orgreater resolution from C17and C18, respectively. If theresolution is less than 50 %,
22、 take corrective action such asreplacement of the injector liner and seals and removal of thefront of the analytical column. Report the degree of resolutionin Section 10. Refer to Practice E 355 for calculation ofresolution values.7.4 Mass Discrimination Check:7.4.1 Use the gas chromatographic instr
23、umental parametersenumerated in 8.3.1; operate the mass spectrometer, but in thelinear scan mode from m/e 45 to 360 in 1 s.7.4.2 Inject a 1-L solution of naphthalene, fluoranthene,and benzo (g,h,i) perylene in equal concentrations (from 50 to150 ng/L) in cyclohexane.7.4.3 Integrate the total ion chr
24、omatogram (TIC).7.4.4 Calculate the following ratios:(1) Area of naphthalene to area of fluoranthene, and(2) Area of benzo (g,h,i) perylene to area of fluoranthene.7.4.5 The ratio of (1) must be less than or equal to 2, and theratio of (2) must be greater than or equal to 0.2. Report thisvalue in Se
25、ction 10.7.4.6 A high molecular weight response can sometimes beimproved by changing the penetration of the chromatographiccolumn into the injector body or using silanized glass wool orquartz as injector packing material, or both. Electronic flowcontrol (instead of constant column head pressure) has
26、 recentlybecome available for Capillary GC. It can be used to provide ahigh molecular weight response by increased flow duringsplitless injection.7.5 Retention Time CheckThe absolute retention times forthe mass discrimination check compounds (7.4.2) must berecorded. The batch-to-batch retention time
27、 reproducibility canbe documented in this way. Report these retention times inSection 10.8. Procedure8.1 Refer to Terminology D 1129 for terms relating to waterand Practice D 3415 for identification of waterborne oils. Referto Practice D 3325 for the preservation of oil samples andPractice D 3326 fo
28、r preparation of the neat oil sample. (Prac-tice D 3326 includes Procedure F for recovering oil from thinfilms on water and Procedure G for recovering oil from sandand debris.) It is the responsibility of the user to validate thismethod for use with these types of matrices since oil recoveredfrom th
29、em may contain contamination derived from the sub-strate material.8.2 Sample PreparationWeigh 100 to 200 mg of oil intoa screw-cap glass vial, and add 10 mL cyclohexane. Sonicationmay be necessary, as well as centrifugation, to remove particu-lates if the sample does not dissolve completely.8.3 Inst
30、rumental Parameters:8.3.1 Gas ChromatographUse the following parameters:1-L splitless injection for 45 s; an initial column temperatureof 55C for 2 min; a temperature ramp at 6C/min to 270C; atemperature ramp of 3C/min to 300C; a final columntemperature of 300C for 17 min; an injection temperature o
31、f290C; and a mass spectrometer (MS) interface temperature of300C. A total run time of approximately 65 min will beachieved using these parameters.8.3.2 Mass Spectrometer Data Acquisition ParametersOperate the mass spectrometer in selected ion monitoring(SIM) for the 24 ions listed in Table 2. Since
32、all of the ions willbe scanned every second, the dwell time for each is 70 ms.Allow a solvent delay time of 4 min before the start of MSscanning.NOTE 1It is recognized that the different monitored classes ofanalytes elute only in certain regions of the chromatogram; consequently,not all ions need be
33、 monitored continuously. However, no effort has beenmade to segment the chromatogram by using different SIM masses atdifferent times for the sake of maintaining simplicity. It is also recognizedthat the signal-to-noise ratio is improved by an increase in the dwell time;however, this improvement is d
34、irectly proportional to the square root ofthe proportional dwell time increase. A signal-to-noise ratio increase ofonly two would thus result from a four-fold increase in the dwell (from 70to 280 ms). This increased dwell time would permit only 3 ions/s to bemonitored. Nevertheless, the experienced
35、analyst who is working with awell-characterized oil source, such as monitoring degradation over time,may choose to monitor fewer ions in order to maximize the signal-to-noiseratios and consequently improve the sensitivity for a subset of the ionslisted in the table. Similarly, users of certain older
36、 model mass spectrom-eters may also choose to modify SIM acquisition by monitoring fewer ionssimultaneously in order to offset lowered MS sensitivity.8.4 Sample Analysis Batching RequirementsEvery timethe mass spectrometer is used, bracket all samples by aTABLE 2 SIM Acquisitionm/e Dwell/ms Elution
37、range/min85 70 4 to 60113 70 4 to 60156 70 4 to 60166 70 4 to 60170 70 4 to 60177 70 4 to 60178 70 4 to 60183 70 4 to 60184 70 4 to 60191 70 4 to 60192 70 4 to 60198 70 4 to 60202 70 4 to 60205 70 4 to 60206 70 4 to 60208 70 4 to 60212 70 4 to 60216 70 4 to 60217 70 4 to 60218 70 4 to 60220 70 4 to
38、60226 70 4 to 60231 70 4 to 60234 70 4 to 60D 5739 063duplicate analysis, and specifically prepare an oil sample induplicate (8.2). Also, the first and last samples to be analyzedmust be these duplicates. Generate the resulting EICs inaccordance with 9.1.1, and compare them visually in accor-dance w
39、ith 9.1.2; any variations observed will serve to definethe analytical error for the entire batch.9. Interpretation9.1 Evaluation of EICs:9.1.1 Data PresentationEICs will be generated for eachoil sample. These EICs are as follows: (1)C2through C4homologs of naphthalene, (2) dibenzothiophene and its C
40、1C3homologs, (3) anthracene and phenanthrene and their C1C3homologs, (4) triterpanes, (5) steranes, and (6) alkanes, (7)benzonaphthothiophene, (8) tri-aromatic steranes, (9) hopanes,(10) pyrene/fluoranthene, (11) fluorene and (12) bicyclonaph-thalenes. The EICs and their approximate time intervals a
41、resummarized in Table 1. The method can be extended to includeother suitable ions, if necessary. (With this in mind, the usermay desire to include naphthalene and C1naphthalene ho-mologs for light, minimally weathered spills or chrysene andits C1to C2homologous series for heavily weathered residualo
42、ils, or both.9.1.2 Direct Visual Comparison of EICsThe EICs foreach suspect source oil will be compared to the appropriateEICs of the spilled oil; evaluation of the patterns (EICs) will beperformed as a peak-to-peak comparison simply by placing theEICs one over the other. Since the y axis will be no
43、rmalized at100 %, automatically, the EICs from identical oils will haveidentical plots (although not necessarily identical scale, whichis dependent on the absolute weight of the injected sample),and they will therefore overlay each other completely (withinthe confines of analytical error defined in
44、8.4). This uniformpresentation of the EICs makes visual comparison by overlaya straightforward procedure, regardless of differences in injec-tion amounts.9.1.3 Weathering Stability:9.1.3.1 The more highly alkylated homologs are preferredfor characterization purposes over the unsubstituted parentcomp
45、ound, or even its monomethylated forms, since bothsolubility in water and biodegradation are related inversely tothe degree of alkylation.9.1.3.2 In similar fashion, biodegradation and water solu-bility are also related inversely to the number of fused rings.Dibenzothiophene and anthracene/phenanthr
46、ene are thereforeinherently more resistant than naphthalenes.9.1.3.3 Steranes and triterpanes are relatively water in-soluble and are extraordinarily resistant to biodegradation.9.1.3.4 The most stable EICs should be examined first,progressing toward the less stable ones. This order from moreweather
47、ing stable to less weathering stable is shown in Fig. 1.9.1.4 Susceptibility of the Various Compound Classes toWeathering ExposureIt may be best to first examine thehighest molecular weight homologous series with the greatestdegree of substitution, since weathering results in progressivelosses great
48、est for the lowest molecular weight homologousseries with the least degree of substitution, progressing towardthe highest molecular weight series with the greatest degree ofsubstitution. In those cases in which weathering has notprogressed sufficiently to eradicate an entire substituted seriescomple
49、tely, the remnants will continue to reflect the originalratios of the unweathered oil. The EICs for a weathered oilversus its unweathered source will thus remain qualitatively thesame, that is, the EICs will not change.NOTE 2A signal-to-noise ratio of 3:1 is used to ascertain the remnantpresence of a peak for those weathered oil EICs displaying drastic loss. Itmay be helpful to auto-range sections of such an EIC in order to examinesuch a low-level signal in greater detail. This same procedure may be usedto step around a dominant peak in an EIC in order to au
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