Stable chlorine isotope analysis of chlorinated acetic acids using gas chromatography/quadrupole mass spectrometry.

Rationale The environmental occurrence of chlorinated acetic acids (CAAs) has been extensively studied, but the sources and transport are still not yet fully understood. A promising approach for source apportionment and process studies is the isotopic characterization of target compounds. We present the first on-line stable chlorine isotope analysis of CAAs by use of gas chromatography/quadrupole mass spectrometry (GC/qMS). Methods Following approved procedures for concentration analysis, CAAs extracted into MTBE were methylated to GC-amenable methyl esters (mCAAs). These mCAAs were then analyzed by GC/qMS for their stable chlorine isotope composition using a sample/standard-bracketing approach (CAA standards in the range δ37Cl −6.3 to −0.2 ‰, Standard Mean Ocean Chloride). Results Cross-calibration of the herein presented method with off-line reference methods (thermal ionization and continuous-flow GC isotope ratio mass spectrometry; TI-MS and CF-GC/IRMS, respectively) shows good agreement between the methods (regression slope for GC/qMS vs reference method data sets: 0.92 ± 0.29). Sample amounts as small as 10 pmol Cl can herewith be analyzed with a precision of 0.1 to 0.4 ‰. Conclusions This method should be useful for environmental studies of CAAs at ambient concentrations in precipitations (<0.06 to 100 nmol L-1), surface waters (<0.2 to 5 nmol L-1) and soil (<0.6 to 2000 nmol kg-1 dry soil) where conventional off-line methods cannot be applied. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]