not be determined in their presence. This problem may be largely avoided by hydrogenation of the olefins as described by Giger and Blumer (11).The interference by biogenic olefins is much less severe for Fraction 3 which contains the phenanthrenes, fluorenes, biphenyls, and dibenzothiophenes of petroleum. Although these latter compounds are good indicators of petroleum, they are present only a t relatively low levels. Further insight into the complexity of petroleum is provided by the work of Coleman and co-workers (12). Because of the above limitations, the procedure described here, like previously reported methods, is not suitable for determining ambient levels of petroleum components in base-line samples from relatively pristine areas. However, the procedure is very useful in determining levels of petroleum in animals exposed to oil a t toxic ievels in the laboratory or exposed to petroleum in the field a t levels significantly above the levels in relatively pristine areas. For example, mussels collected from Coal Oil Point, a natural oil seep area near Santa Barbara, Calif., contain very significant amounts of weathered petroleum detectable by this procedure. We have used the overall extraction-gas chromatographic procedure on several hundred tissue samples including mussels, lobsters, clams, oysters, fish, shrimp, abalone, crabs, starfish, sea urchins, and bloodworms and found it to be quite convenient. Mass spectrometry was useful for the further characterization of representative samples.
ACKNOWLEDGMENT Mass spectrometric analyses were performed by R. Foltz and P. Clarke.
LITERATURE CITED (1) D. B. Boylan and E. W. Tripp, Nature (London),230, 44 (1971). (2) J. W. Anderson, J. M. Neff, E. A. Cox, H. E. Tatem. and G. M. Hightower, Mar. Biol., 27, 75 (1974). (3) R. C. Clark, Jr., and M . Blumer, Limnol. Oceanogr., 12, 79 (1967). (4) M. Blumer, G. Souza, and J. Sass, Mar. Biol., 5 , 195 (1970). (5) R. C. Clark, Jr., and J. S.Finley, Proceedings of Joint Conference on Prevention and Control of Oil Spills, March 13-15, 1973, p 161. (6) J. W. Blaylock, P. W. O'Keefe, J. N. Roehm, and R . E. Wilding, Ref. 5, p 173. (7) M. S.E. Munson and F. H. Field, J. Am. Chem. SOC.,89, 1047 (1967). (8) M. Blumer and D. W. Thomas, Science, 148, 370 (1965). (9) M. Blumer, R. R . L. Guillard, and T. Chase, Mar. Biol., 8, 183 (1971). (10) F. H. Field, J. Am. Chem. SOC.,90, 5649 (1968). (11) W. Giger and M. Blumer, Anal. Chem., 46, 1663 (1974). (12) H. J. Coleman, J. E. Dooley, D. E. Hirsch, and C. J. Thompson, Anal. Chem., 45, 1724 (1973).
RECEIVEDfor review January 15, 1975. Accepted December 1, 1975. This work was supported by the American Petroleum Institute under Contract No. OS-20-G. Tissue samples were submitted by Jack Anderson of Texas A&M University under API Contract No. OS-20-C and Dale Straughan of the University of Southern California under API Contract No. OS-20-D.
Pyridine Catalyzed Reaction of N-Nitrosodi methylamine with Heptaf Iuorobutyr ic Anhydride Terry A. Gough," Martin A. Pringuer, Keith Sugden, and Kenneth S. Webb Laboratory of the Government Chemist, Cornwall House, Stamford Street, London SE 1 9N0, England
Colin F. Simpson University of Sussex, Brighton BN 1 9QJ, Sussex, England
The pyridine catalyzed reaction of N-nitrosodimethylamine with heptafluorobutyric anhydride has been studied and the products have been separated by gas chromatography. The constituents of the reaction mixture were identified by combined gas chromatography and mass spectrometry, and a volatile N-nitrosodimethylamine derivative was detected. Electron impact mass spectra indicated a molecular weight of 268 and high resolution measurements gave an empirical formula of C6H3N202F7.Supporting evidence was obtained from field desorption spectra and a microwave plasma detector. The structure of this compound was deduced from the mass spectral evidence, supported by nuclear magnetic resonance spectrometry. The compound has a retention index of 790 at 135 O C on a silicone (OV1) stationary phase in contrast to a value of 1335 for the derivative previously reported.
T h e preparation of derivatives which can be separated by gas chromatography and detected by electron capture is frequently employed for detecting trace constituents. The use of heptafluorobutyric anhydride (HFBA) to form elec-
tron capturing derivatives of volatile N-nitrosamines has been described previously ( 1 ) . The nature of a series of dialkyl and heterocyclic nitrosamine derivatives has been studied by gas-liquid chromatography and mass spectrometry (2). In this earlier work, it was reported that two HFBA-nitrosodimethylamine derivatives were formed, with Kovats retention indices of 790 and 1335, on a silicone (OV1) stationary phase. Only the derivative having the longer retention time was examined and a proposed structure presented. The aim of this further work is to study the nature of the other reaction product and confirm t h a t it is also derived from the reaction between N-nitrosodimethylamine and HFBA.
EXPERIMENTAL Apparatus. A Pye 104 chromatograph was fitted with a 6 m X 4 mm i.d. glass column containing 5% Carbowax 20M on 80-100 mesh Chromosorb G acid washed and DCMS treated. Detection was by flame ionization and microwave plasma (Applied Research Laboratories Ltd, Model 850).Electron impact spectra and accurate mass measurements were obtained using a n AEI Model MS 902 double focusing mass spectrometer interfaced to the chromatograph via a silicone membrane separator. Field desorption spectra were obtained on a Varian MAT CH5 mass spectrometer using ANALYTICAL CHEMISTRY, VOL. 48, NO. 3, MARCH 1976
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