Potential Application of Gas Chromatography/Tandem Mass Spectrometry in the Measurement of Coeluting Isomers

Abstract

Despite the unprecedented popularity of separation chromatography, the measurement of coeluting isomeric chemicals remains an extremely difficult task. We developed an analytical scheme capable of measuring two coeluting isomers using a single chromatographic column and a gas chromatography/tandem mass spectrometry system. The protocol utilized two product ion fragments generated from a common parent ion associated with the isomers for quantitation. The utility of the analytical scheme was demonstrated with the measurements of several pairs of coeluting polychlorinated biphenyl (PCB) isomers in standard solutions and fish liver samples. Best results were given when a set of stringent constraints for the abundance ratio of the two product ion fragments was satisfied. Analyses of seven fish liver samples collected from nearshore San Diego, CA, indicated that the domain that had been previously reported to comprise PCB 153 and PCB 168 actually contained PCB 153 only. Although only a selected number of PCB congeners were examined, the results presented indicate that the analytical scheme has the potential to be used to determine the concentrations of all chromatographically coeluted isomers.

Pulsed large volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry for simultaneous determination of typical halogenated persistent organic pollutants

“…However, GC/MS is preferred now because absolute chromatographic separation for the individual analyte was difficult even if multidimensional GC was employed [10]. Several GC/MS methods have been established based on high-resolution magnetic-sector MS (HR-MS) [11], tandem MS (MS/MS) using an ion trap detector [12][13][14], or triple quadrupole analyzer [15] and time-of-flight MS (TOF-MS) [16], as well as lowresolution quadrupole MS (qMS) [17]. Obviously, HR-MS is the most powerful tool offering high selectivity with satisfactory sensitivity by virtue of its high ultimate resolving power and accurate mass measurement; nevertheless, nowadays only a few laboratories can afford this instrument.…”