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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.
6.4.6.1 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.
