Compound-specific stable carbon isotope ratios of phenols and nitrophenols derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide

We developed an analytical method for measuring compound-specific stable carbon isotope ratios (delta C-13) of phenols and nitrophenols in filter samples of particulate organic matter. The method was tested on 13 phenols derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), together with four nonphenolic compounds. The data obtained by our method required two specific corrections for the determination of valid delta C-13 values: (1) for nitro compounds, the routine correction with use of m/z 46 for the contribution of (COO)-C-12-O-17-O-16 molecules) to m/z 45 was modified due to impact of NO2 on the m/z 46 trace, and (2) for the derivatized phenols, measured delta C-13 values were corrected for the shift in delta C-13 due to the addition of carbon atoms from the BSTFA moiety. Analysis of standard-spiked filters showed that overall there was a small compound-dependent bias in the delta C-13 values: the average bias +/- the standard error of the mean of -0.21 +/- 0.1% for the standard compounds tested, except 3-methylcatechol, methylhydroquinone, 4-methyl-2-nitrophenol, and 2,6-dimethyl-4-nitrophenol, whereas the average biases +/- the standard errors of the mean for those were +1.2 +/- 0.3 parts per thousand, +1.2 +/- 0.2 parts per thousand, -1.2 +/- 0.2 parts per thousand, and -1.4 +/- 0.5 parts per thousand, respectively, when the injected mass of a derivatized compound exceeded 15 ngC. In situations where such small biases and uncertainties are acceptable, the method described here could be used to obtain valuable information about delta C-13 values. We also analyzed a real filter sample to demonstrate the practical applicability of the method. (C) 2013 Elsevier B.V. All rights reserved.