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

Abstract We developed an analytical method for measuring compound-specific stable carbon isotope ratios (δ 13 C) 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 δ 13 C values: (1) for nitro compounds, the routine correction with use of m / z 46 for the contribution of 12 C 17 O 16 O molecules) to m / z 45 was modified due to impact of NO 2 on the m / z 46 trace, and (2) for the derivatized phenols, measured δ 13 C values were corrected for the shift in δ 13 C 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 δ 13 C 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‰, +1.2 ± 0.2‰, −1.2 ± 0.2‰, and −1.4 ± 0.5‰, 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 δ 13 C values. We also analyzed a real filter sample to demonstrate the practical applicability of the method.