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of Cl from CI5 11). This made PCA analysis very complex, time-consuming and 
expensive. As a consequence, only a handful of PCA studies existed, and information 
about the PCA burden is not available from most regions of the world. 
5.3.2 Challenges of PCA method development 
One of the main aims of this project was to make PCAs analysis simpler in order to 
enable routine analysis. This required to develop alternatives and to overcome the 
following problems: 
• To avoid the use of expensive equipment such as HRMS and, as a consequence: 
• To separate PCAs from all other interfering (polychlorinated) contaminants 
already during the clean-up step to allow the application of low resolution mass 
spectrometry (LRMS). 
• To eliminate or at least minimise differences in the response factors between 
formula groups, congeners and isomers, which would allow: 
• To use commercially available technical mixtures as references for quantifi 
cation. 
• To allow the detection of lower chlorinated congeners. 
• To enable the comparability with ECNI as the current quantification technique. 
5.3.3 PCA method development 
5.3.3.1 Clean-up and gas chromatography 
The first step to establish a simpler PCA method was to collect all PCAs within one 
fraction without other interfering pollutants (mainly PCB and polychlorinated pesticides 
such as toxaphene etc.). A carefully optimised fractionation on deactivated Florisil 
fulfilled this requirement as closely as possible (Reth and Oehme, 2005). Moreover, the 
analysis of sediments requested a cautious removal of elemental sulphur (e.g. by surface 
activated copper) and a corresponding method optimisation.