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Full text: R&D-Project - Identification of organic compounds in the North and Baltic Seas

6.4.6 Dicofol 
The analysis of dicofol turned out to be quite problematic because of its thermal and 
chemical instability. It was difficult to control the GC-MS response even with the use of 
GC injectors, which are generally considered optimal for thermolabile compounds (on 
column and PTV injectors). The degradation led to dichlorobenzophenone (DBP). It is 
not unlikely that many of the methods described in literature in fact detected DBP 
formed in-situ during GC analysis. 
Unfortunately, dicofol was found to have a poor ESI-MS sensitivity in HPLC-MS 
analysis. The approach of using HPLC-MS to reduce thermal stress during the analysis 
thus was not successful. 
Nevertheless, it was possible to develop a GC-MS method having a moderate 
sensitivity, which was suitable for first screening of sea water. The LODs and LOQs 
achieved were 0.3 and 1 ng/L, respectively. (The sensitivity is considered “moderate” in 
comparison with the LOD that is normally used for marine matrices at the BSH. 
Compared to literature data it may be considered good). A full validation of the method 
was not performed because no positive findings were obtained in sample screening. Water 
Dicofol was determined in sea water samples from the North Sea which had been 
collected during 2 cruises in 2003 and 2004 \ Dicofol was below the LOD ( 0.3 ng/L) 
in all samples. 
Because of the instability of dicofol observed during the development of the analytical 
method, it was considered useful to investigate the stability of the pesticide in natural 
waters. Lor that purpose, sea water was spiked with dicofol and its degradation was 
observed for four weeks. Ligure 51 shows the temporal trend of dicofol and of its 
1 Altogether, samples were taken during 4 cruises. However, samples from the first cruise had been eluted 
with acetone, which later was found to enhance degradation of dicofol to DBP - with a half-life of 45 
min. at room temperature! Samples from the 4 th cruise were not analysed because of the negative findings 
for the two other cruises.

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