Environ. Sci. Technol. 2006, 40, 2493
Comment on “Biodegradation of r-Pinene in Model Biofilms in Biofilters” During the course of experiments aimed at determining “transport and reaction rates of hydrophobic pollutants in model biofilms”, Miller and Allen found a degradation product of R-pinene, which they characterized as cis-2,8p-menthadien-1-ol (1). This identification was based on the
electron impact mass spectrum of this degradation product. The full mass spectrum was shown in their Figure 10 and is reproduced here (see Figure 1A). This mass spectrum is almost certainly not that of cis-2,8-p-menthadien-1-ol (see Figure 1B). Clearly, the ions at m/z 79, 109, and 137 are not abundant in the spectrum reported by Miller and Allen, and the relative intensities of m/z 91, 119, and 134 do not agree either. The unknown compound is not trans-2,8-p-menthadien-1-ol either, which has an electron impact mass spectrum that is almost identical to that of its cis isomer (2). A search of the NIST mass spectral database (2) indicates that the compound found by Miller and Allen could well be 2,6-dimethyl-1,3,5,7-octatetraene, which is also known as cosmen or cosmene. This is a terpene with a composition of C10H14, and it has been found in various essential oils along with R-pinene (3-5). The mass spectra of cosmene and the unknown found by Miller and Allen compare very favorably; compare Figure 1A and C. Without gas chromatographic retention information, it is not possible to confirm that the unknown compound is, in fact, cosmene, but this seems to be a more likely assignment than the one made by Miller and Allen.
Literature Cited (1) Miller, M. J.; Allen, D. G. Biodegradation of R-pinene in model biofilms in biofilters. Environ. Sci. Technol. 2005, 39, 58565863. (2) National Institute of Standards and Technology. NIST Standard Reference Database 1A, Mass Spectral Search Program, Version 1.5; NIST: Gaithersburg, MD, 1996. (3) Ozel, M. Z.; Gogus, F.; Hamilton, J. F.; Lewis, A. C. The essential oil of Pistacia vera L. at various temperatures of direct thermal desorption using comprehensive gas chromatography coupled with time-of-flight mass spectrometry. Chromatographia 2004, 60, 79-83. (4) Flamini, G.; Cioni, P. L.; Morelli, I. Differences in the fragrances of pollen and different Floral parts of male and female flowers of Laurus nobilis. J. Agric. Food Chem. 2002, 50, 4647-4652. (5) Veriotti, T.; Sacks, R. High-speed GC and GC/time-of-flight MS of lemon and lime oil samples. Anal. Chem. 2001, 73, 43954402.
FIGURE 1. (A) Mass spectrum of a degradation product of r-pinene as reported by Miller and Allen (re-plotted from ref 1); (B) mass spectrum of cis-2,8-p-menthadien-1-ol from the NIST reference database (2); (C) mass spectrum of 2,6-dimethyl-1,3,5,7-octatetraene, which is also known as cosmen or cosmene, from the NIST reference database (2). All of these mass spectra were obtained in the electron impact mode.
10.1021/es052497o CCC: $33.50 Published on Web 02/17/2006
2006 American Chemical Society
Ronald A. Hites School of Public and Environmental Affairs Indiana University Bloomington Indiana 47405 ES052497O
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