Evaluation of Halogen‐Specific Detector (XSD^TM) for Trace Analysis of Chlorinated Fatty Acids in Fish

Abstract

The applicability of a halogen‐specific detector (XSD™, manufactured by OI Analytical) was evaluated for GC analysis of chlorinated fatty acid methyl esters (FAMEs) that are present at trace levels in transesterified fish extract, a complex matrix consisting of similar but nonchlorinated compounds. A characteristic of the XSD working principle is that thermal electron emission, negative surface ionization and positive surface ionization are all operative in a concerted manner. While the XSD is not superior to other GC detectors in terms of signal‐to‐noise, its merit is in its high selectivity (10⁶) and low detection limit (2 pg Cl) for chlorinated fatty acids, and ease of operation and maintenance. Its reasonably wide linear range (up to 10 ng Cl) is desirable for trace analysis of chlorinated FAMEs. A major drawback of this detector is a certain degree of peak broadening and peak tailing of eluted compounds with concentrations larger than ∼1 ng Cl/µL in the injected solution even though this value does not exceed the upper limit of the XSD linear range. Nevertheless, in trace analysis of chlorinated compounds, the concentrations of analytes are usually well below 1 ng Cl/µL. Parallel use of the XSD and a universal detector such as FID in gas chromatography is useful for optimizing operation conditions for trace analysis and simultaneously analyzing nonchlorinated major components.

Keywords:

• Halogen‐specific detector
• XSD
• GC detector
• Trace analysis
• Chlorinated fatty acid
• Fish extract
• Food analysis
• Environmental analysis

Acknowledgments

This work was funded by the consortium “Using Chemistry and Biology to Improve Bleaching Effluent Quality” at the University of Toronto Pulp & Paper Centre with the following industrial partners: Alberta Pacific Forest Industries Inc., Aracruz Cellulose SA, Avenor Inc. (now Bowater Pulp and Paper Canada Inc., Boise Cascade Corp., Georgia‐Pacific Corp., International Paper, Irving Forest Services Ltd., Japan Carlit Co. Ltd., Nippon Paper Industries Co. Ltd., Ontario Ministry of Environment & Energy, Potlatch Corp., Sterling Pulp Chemicals Ltd., Tembec Inc., and Weyerhaeuser Co. We appreciate laboratory support from National Water Research Institute; in particular, we thank M. Servos and J. Toito for assistance in securing fish samples, and S. Backus, I. D'sa and M. Kohli for help in GC/XSD operation. We also appreciate technical support from OI Analytical and Chromatographic Specialties Inc.