MoP-11
ANALYTICAL TANDEM MASS SPECTROMETRY WITH A BENCHTOP GC/MS/MS SYSTEM FOR THE ANALYSIS OF CHLORINATED PESTICIDES
Steven T. Fannin*, Meredith Conoley*, James Edwards* and
Lisa Stokan**
*Finnigan Austin/Gas Chromatography Systems, 2215 Grand Avenue Parkway, Austin TX 78728-3812
**Thermo Instruments Australia, 20/38-46 South Street, Rydalmere
Tandem mass spectrometry (MS/MS) is a powerful technique for the analysis of target analytes at trace levels in complex matrices. The principle advantage of MS/MS is the increased selectivity, whereby a target ion is separated (isolated) from the chemical background (coeluting chromatographic peaks or highly complex matrix). The isolated precursor ion is then collisionally activated, followed by a dissociation producing a characteristic product ion spectrum. The product ion spectrum, free from chemical interference, is used for confirmational purposes. In addition, a unique product ion in the spectrum can be used for quantitation. Because the chemical background (the matrix) is eliminated in the first stage of tandem mass spectrometry, the limit of detection (signal-to-noise ratio) is greatly improved for the target analytes. Conventional approaches to MS/MS require the use of more than one analyser, e.g. more than one quadrupole rod assembly (tandem in space). Tandem in time mass spectrometry, achievable with quadrupole ion trap technologies, affords the analyst benchtop MS/MS capabilities.
The work presented in this report demonstrates the utility of benchtop MS/MS with an external source quadrupole ion trap GC/MS/MS system (the Finnigan GCQ Tandem). Several chlorinated pesticides were analysed using Positive Ion Chemical Ionization (PICI) MS/MS. PICI was chosen as the ionization technique to further enhance the selectivity of the analysis. In addition, because PICI is a "soft" ionization technique, much less fragmentation is observed, thereby providing greater precursor ion abundance. Specific target pesticides were chosen to demonstrate the linearity and limits of detection for the MS/MS mode of operation on the GCQ system.