Thesis Abstracts 2004
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The Development of Novel Analytical Techniques for the Analysis of PCBs in Small Samples of Avian Blood
By: Christina M. Harrison (MSc Chemistry - Speciality : Environmental Science)
Supervisors: Dr. Ron Weir and Dr. David Kelly
Abstract
Two analytical methods were developed for the analysis of PCBs in small samples of avian blood. The detection of PCBs in blood is considered difficult, since low concentrations must be determined in small sample sizes. In this work two techniques have been designed that afford low limits of detection in avian blood samples smaller than 1 mL.
Traditional analytical methods of detecting PCBs in blood require a minimum sample size of 5 mL for a detection limit of 1 ppb. The objective of the current work was to reduce this sample size by at least an order of magnitude, while maintaining the same detection limit. This was achieved by creating analytical methods that were capable of using a greater proportion of the analytes contained in the sample for detection purposes.
Detection by Ion-Trap Mass Spectrometry (ITMS) was investigated for all 209 PCB congeners. By using MS-MS analysis, an instrument detection limit of approximately 2 pg per congener was achieved, which is an order of magnitude lower than the typical detection limits attained by Single-Quadropole SIM analysis. Upon the creation of the ITMS-MS detection method, a Large Volume Injection (LVI) GC method was investigated. A single injection volume of 150 µL was used to increase the amount of analyte that could be introduced into the ITMS detector. The developed LVI-GC method for PCBs was demonstrated to decrease the detection limit of the GC/ITMS-MS method by one order of magnitude, when compared to a standard injection volume of 2 µL.
The extraction techniques of Direct Immersion-Solid Phase Microextraction (DI-SPME) and Pressurized Solvent Extraction (PSE) were investigated for PCBs in avian blood. A DI-SPME method was developed and coupled directly to GC/ITMS-MS, which reduced the dilution factor of the entire analysis to a factor of the partitioning coefficient. Samples of 0.1 g of avian plasma were successfully quantified for all 209 congeners by this method at or above a concentration of 3 ng/g (per wet weight plasma). The developed PSE method was coupled to LVI-GC/ITMS-MS, so that a larger proportion of the final PSE extract could be used for detection purposes. Samples of 0.2 g of avian whole blood and plasma were successfully quantified for the 209 PCBs by the developed PSE/LVI-GC/ITMS-MS method at or above a sample concentration of 5 ng/g and 6 ng/g respectively. The PSE system used contained trace levels of PCB background, which elevated the MDL by approximately 2 ng/g per congener. Thus if a pristine PSE system were employed, an MDL of approximately 3 ng/g per congener would be possible for PCBs in avian blood. The analytical techniques developed in this work were therefore successful in reducing the typical detection limit for PCBs in avian blood by at least one order of magnitude, thereby allowing small sample sizes to be quantified at the ppb level.
