170 
Analytical procedure for biota samples 
After optimisation of the method, sample preparation was carried out via MAE, gel 
permeation chromatography (GPC), and neutral aluminium oxide clean-up. The 
procedure is summarised in Figure 32, experimental details are presented in 
Appendix 6.6.5. 
Fish sampling; liver preparation 
Storage at -20-0 
, thawing, addition of 
ISTD 
Freeze drying (1.3 mbar, 24 h) 
* 
Microwave assisted extraction 
of 2-4 g fish liver with 
acetone/hexane (3:1) 
(700 W, lOOC, 10 min) 
* 
Filtration, removal of 
solvent, gravimetric 
determination of 
extractable lipids 
Gel permeation chromatography 
(solid phase: biobeads, liquid phase: 
ethyl acetate/cyclohexane (1:1)) 
4 
Change to 
hexane solvent 
Aluminium oxide (neutral) clean-up 
elution with hexane/dichloromethane 
(1:1) 
* 
GC-MS 
Figure 32: Overall scheme for the analysis of biota samples for chlorpyrifos, endosulfan, and trifluralin 
6.3.2.2 Methods for Dicofol 
As dicofol was found to be thermally unstable during gaschromatographic separation, 
the compound had to be injected “on column” at low temperature. Mass spectrometric 
detection of dicofol was carried out in El mode. An HPLC-MS/MS method proved to be 
unsuitable for dicofol because the yield of ions was too low in the ESI mode. 
Experimental details are presented in Appendix 6.7.