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zation at 266 nm, for example, may be an effective approach to selective detection of aromatic compounds. Allowing experiments analogous to those performed by photoionization mass spectrometry to be carried out in a simple way, MPI may increase the versatility of FTMS as an all-purpose mass spectrometer. Certainly FTMS has some attractive features when compared to TOF in an analytical MPI experiment. As a high-performance, pulsed mass spectrometer which is especially compatible with various light sources, the FTMS will enhance the marriage of optical and mass spectroscopy. Subsequent to the submission of this manuscript a report by McIver et al. has appeared also describing the detection of ions produced by MPI using FTMS (42).
LITERATURE CITED (1) Johnson, P. M. Acc. Chem. Res. 1980, 73,20-26. (2) Zandee, L.; Bernstein, R. B. J. Chem. Phys. 1979, 70,2574-2575. (3) Zandee, L.; Bernstein, R. B. J. Chem. Phys. 1979, 77,1359. (4) Cooper, C. D.; Williamson, A. D.; Mliler, J. C.; Compton, R. N. J. Chem. Phys. 1980, 73,1527-1537. (5) Llchtin. D. A.; Datta-Ghosh, S.; Newton, K. R.; Bernstein, R. 8. Chem. Phys. Left. 1980, 75,214-219. (6) Reiiiv, J. P.: KomDa. K. L. J. Chem. Phvs. 1980. 73. 5468-5476. Carney, T.; Baer, T. J. Chem. Phys. 1961, 75,477-478. Lubman, D. M.; Naaman, R.; Zare, R. N. J. Chem. Phys., 1980, 72,
3034-3040. Seaver, M.; Hudgens, J. W.; Decorpo, J. J. Int. J . Mass Spectrom. Ion. Phys. 1980, 3 4 , 159-173. Lubman, D. M.; Kronick, M. N. Anal. Chem. 1982, 54,660-665. Rider, D. M.; Durant, J.; Anderson, S.; Zare, R. N. Presented at the 30th Annual Conference on Mass Spectrometry and Allied Toplcs, Honolulu, HI, June 6-11, 1982. Harrlson, W. W.; Rider, D. M.: Zare, R. N. Presented at the 30th Annual Conference on Mass Spectrometry and Allled Topics, Honolulu, HI, June 6-11, 1982. Hudgens, J. W.; Dulgan, M. T.; DiGiuseppe, T. G.; Wyatt, J. R. Presented at the 30th Annual Conference on Mass Spectrometry and Allied Topics, Honolulu, HI, June 6-11, 1982. Dunbar, R. C. "Gas Phase Ion Chemistry"; Bowers, M. T., Ed.; Academic Press: New York, 1979;Vol. 2. Cody, R. B.; Burnier, R. C.; Reents, W. D., Jr.; Carlin, T. J.; McCrery, D. A.; Lengel, R. K.; Freiser, B. S. Int. J. Mass. Spectrom. Ion Phys. 1980, 33,37-43. Comlsarow, M. B. Adv. Mass Spectrom. 1980, 8 , 1698-1706. Wilkins, C. L.; Gross, M. L. Anal. Chem. 1981, 53, 166lA-1676A. Burnier, R. C.; Byrd, G. D.; Freiser, B. S. Anal. Chem. 1980, 52,
1641-1650. Carlin, T. J.; Wise, M. B.; Freiser, B. S. Inorg. Chem. 1981, 20,
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(21) Jacobson, D. 8.; Byrd, G. D.; Freiser, B. S. J. Am. Chem. SOC.1982, 704, 2320-2321. (22) McCrew. D. A.; Ledford, E. B., Jr.: Gross, M. L. Anal. Chem. 1982. 54, 1435-1437. (23) Comisarow, M. B. Inf. J. Mass Spectrom. Ion Phys. 1981, 37, 251-257. - . - ..
(24) Cassady, C. J.; Freiser, B. S. Presented at the 29th Annual Confer-
ence on Mass Spectrometry and Allled Topics, Minneapolis, MN, May
24-29, 1982. (25) Cody, R. B.; Burnler, R. C.; Freiser, B. S. Anal. Chem. 1982, 54, 96-101. (26) Cody, R. B.; Freiser, B. S. Int. J. Mass Spectrom. Ion Phys. 1982, 4 7 , 199-204. (27) Comisarow, M. B.; Marshall, A. G. J. Chem. Phys. 1975, 62,293. (28) White, R. L.; Ledford, E. B., Jr.: Ghaderi, S.; Wilkins, C. L.; Gross, M. L. Anal. Chem. 1980, 52, 1527-1529. (29) Cody, R. 8.; Frelser, B. S. Anal. Chem. 1982, 54, 1431-1433. (30) Fehnel, E. A.; Carmack. M. J. Am. Chem. SOC. 1949, 77,85-93. (31) Freidel, R. A.; Orchln, M. "UV Spectra of Aromatic Compounds": Wiley: New York, 1951. (32) Rosenstock, H. M.; Draxl, K.; Steiner, B. W.; Herron, J. T.; J. Phys. Chem. Ref. Data, Suppl. 1977, 6 , No. I.
(33) Carlin, T. J.; Freiser, B. S. Anal. Chem. l98S, 55,571-574. (34) Whlte, R. L.; Wilkins, C. L. Anal. Chem. 1982, 54,2211-2215. (35) Mcluckey, S.A.; Sallans, L.; Cody, R. B.; Burnier, R. C.; Verma, S.; Freiser, B.
S.;Cooks, R. G.
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44. 215-229. (36) Leutwyler, S.;Even, U.; Jortner, J. Chem. Phys. Lett. 1980, 74, 11-14. (37) Gerrity, D. P.; Rothberg, L. J.; Vaida, V. Chem. Phys. Lett. 1980, 74, 1-5. (38) Duncan, M. A.; Dietz, T. 0.; Smalley, R. E. Chem. Phys. 1979, 4 4 , 415-419. (39) Halle, L. F.; Armentrout, P. B.; Beauchamp, J. L. J. Am. Chem. SOC. 1981, 703, 962-963. (40) Ledford, E. B., Jr.; White, R. L.; Ghaderi, S.; Wiikins, C. L.; Gross, M. L. Anal. Chem. 1981, 52,2450-2451. (41) White, R. L.; Wilkins, C. L. Anal. Chem. 1982, 54,2443-2447. (42) Irion, M. P.; Bowers, W. D.; Hunter, R. L.; Rowland, F. S.; McIver, R. T., Jr. Chem. Phys. Lett. 1982, 93, 375-379.
Timothy J. Carlin Ben S. Freiser* Department of Chemistry Purdue University West Lafayette, Indiana 47907 RECEIVED for review November 5,1982. Accepted February 1, 1983. Support for this research was provided by the Department of Energy (DE-AC02-80ER10689) and the National Science Foundation (CHE-80026585),which provided funds to purchase the FTMS.
Identification of Geochemical Polycyclic Aromatic Hydrocarbons from Terpenes by High-Resolution Shpol'skii Effect Fluorescence Spectrometry Sir: In this paper, we demonstrate that high-resolution spectrofluorimetry (HRF) at 4.2 K in n-alkane matrices can be used to identify polycyclic aromatic hydrocarbons (PAH) derived from triterpene, which occur in the organic matter of marine and terrestrial sediments. The chrys-a (see the structure on Figure 1A) is indeed an interesting case since this molecule has bulky substituents and certainly cannot fit in the crystal lattice of n-alkane in the same way as triphenylene or coronene itself (I). We present results obtained on a synthetic sample (2)of chrys-a that show unambiguously the existence of a quasi-linear fluorescence spectrum with conventional excitation (Figure 1A). The presence of the ethylcyclopenteno part of the chrys-a molecule apparently does not hinder the inclusion at low concentration (Le., C < lo4 M) of the solute in the n-heptane crystal in sites
that are sufficiently homogeneous to give rise to high-resolution spectra. It should be mentioned that another large compound with unusual structure such as hexahydrohexahelicene, a nonplanar composite molecule, was also shown to give a Shpol'skii effect (3). In three marine sediments from the Sea of Oman (South Arabia), the series of chrysene derivatives was extracted from the total aromatic fraction by HPLC on psilica-NH2 stationary phase with n-heptane as an eluant ( 4 ) . Figure 1B shows that chrys-a can be easily identified in the sediment extract. This is, to our knowledge, the first identification by HRF of such a highly alkylated PAH. This result clearly opens a new field since it shows that such molecules, which occur widely in sediments and petroleums, can be introduced in
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dominate in this pentacyclic chrysene series. The quantification of such compounds can be done in an absolute way by the method of constant additives, with an internal standard, allowing the determination of absolute quantities of the order of a nanogram. This HRF is now being developed by us (M.E.) on other series of biogeochemical markers in complement with GC/MS investigations, especially in the case of the elucidation of complex mixtures of isomers.
AUTHENTIC M O L F C U L E OF CHRYS-a
ACKNOWLEDGMENT We thank d. Joussot-Dubien for comments and careful examination of the manuscript. ' 7 Registry No. Chrys-a, 59279-20-8.
W A V E L E N G T H (nm)
r-
> -
B
in
LITERATURE CITED
I-
I C H R Y S - a FROM 5OUTH A R A B I A 5 E A W
0
2
p-365
370
375
380
385
W A V E L E N G T H (nm)
Flgure 1. (A) Filrorescence spectrum in n-heptane at 4 K of an M. Excltation authentic molecule of chrysene-a (Chrys-a). C = was at 276.5 nm. (B) Fluorescence spectrum in n-heptane at 4 K of the tetraaromatic fraction, obtained by HPLC,from a marine sediment (Sea of Oman, South Arabia). Excitation was at 276.5 nm.
n-alkane crystals, even though sterical hindrance is not very favorable to insertion. In fact, what is occurring could most likely be related to the findings of Rima et al. (5) in the case of PAH such as phenanthrene whose molecules do not fit in the crystal lattice of a n-alkane. In that case, the authors assume that a t low concentration and under the condition of fast freezing a new type of inclusion of guest molecules is formed in the alkane matrix (5). The technical aspects of the methodology, which includes a home made spectrofluorimeter working with a liquid helium cryostat, have been reported elsewhere (4-6).The HPLC is straightforward and has been described ( 4 ) . The marine sediments were cored from surface sediments during the Orgon IV cruise at several water depths varying between 200 and 4000 m in an area where the organic matter is mainly of authochthonous origin (7). This origin would explain the predominance of chrys-a, a biogeochemical marker formed by the aromatization of hopanoid triterpenes occurring in procaryotes (bacteria and blue-green algae), which appears to
(1) Pltts, W. M.; Merle, A. M.; El-Sayed, M. A. Chem. Phys. 1979, 3 6 , 437-446. (2) Greiner, A.; Spyckerelle, C.; Albrecht, P. Tetrahedron 1976, 32, 257-260. (3) Palewska, K.; Ruziewlcz, 2 . Chem. Phys. Lett. 1979, 64, 378-382. (4) Ewald, M.; Moinet, A.; Bellocq, J.; Wehrung, P.; Albrecht, P. In "Gochimie Organique des Skiiments, Marins Profonds"; Orgon IV, Golfe d'Aden, Mer d'oman, Ed. CNRS: Paris, 1981; pp 405-414. (5) Rima, J.; Lamotte, M.; Joussot-Dubien, J. Anal. Chem. 1982, 52, 2093-2095. (6) Ewald, M.; Lamotte, M.; Redero, F.; Tissier, M. J.; Albrecht, P. Adv. Org. Geochem. 1980, 12, 275-279. (7) Caratini, C ; Beliet, J.; Tlssot, C. In "GOochimie Organique des Skilments Marlns Profonds"; Orgon I V , Goife d'Aden, Mer d'Oman, Ed. CNRS, Parls, 1981; pp 265-307.
Marc Ewald* Groupe d'Oc6anographie Physico-Chimique de 1'ERA No. 167 Laboratoire de Chimie Physique A Universit6 de Bordeaux I 33405 Talence Cedex, France
ERA CNRS No. 278-Laboratoire et Chimie Marines Universit6 Pierre et Marie Curie 75230 Paris Cedex 05, France
Alain Moinet Alain Saliot de Physique
Pierre Albrecht LA 31-Laboratoire d'Etudes des Substances Naturelles Institut de Chimie, Universit6 de Strasbourg 67008 Strasbourg Cedex, France RECEIVED for review November 1, 1982. Accepted January 26, 1983. We are indebted for partial financial support to Centre de GBochimie Marine who sponsors ORGON cruises on N/O J. Charcot, allowing new experiments on sediment cores.
Electron Pulse Shape in Laser-Enhanced Ionization Spectrometry Sir: Recently, the optogalvanic effect first observed by Penning (I)has provided, in conjunction with the development of dye lasers, a new detection tool which avoids most of the optical difficulties usually encountered in fluorescence and emission spectrometry. Flame optogalvanic spectrometry or laser-enhancedionization (LEI) spectrometry has already been demonstrated (2-5) to be a very powerful technique in the trace analysis field. Different theoretical aspects of optogalvanic signals in flames (photoexcitation,charge production,
and current detection) have been investigated in recent papers (3, 5-8). In a conventional air-acetylene flame with low concentration of Na (100 ppb) and a two-step laser excitation, we have observed the temporal shapes of the LEI signal, using a fast current detector. These studies have been made by varying two parameters: the high dc voltage and the position in the flame of the two laser beams. Analysis and interprlatation of the profiles observed for the first time without significant electronic distortion for short (6 ns) laser pulses are
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