166 
The extraction principles were similar for all compounds. While solid phase extraction 
(SPE) with a polymer resin was used for water samples, microwave assisted extraction 
(MAE) was used for sediment and biota samples (6.3.2.1 and 6.6.3 to 6.6.5). 
6.3.2.1 Methods for Chlorpyrifos, Endosulfan and Trifluralin 
GC-MS analysis 
A common GC-MS analysis method is used for all three matrices (water, sediment and 
biota). Experimental details are provided in the appendix under 6.2. 
GC analysis using a standard non-polar capillary column was unproblematic and 
yielded baseline separation of all compounds. MS analysis was performed both in El 
and NCI mode. The parameters for GC and MS are summarised in Table 82 (chapter 
6.6.2). 
Deuterated analogues of trifluralin, chlorpyrifos and endosulfan I were used as internal 
standards for quantification. 
As has been demonstrated in the chapter on validation (6.3.3), the NCI method was 
more sensitive with all compounds, and was consequently used to analyse all samples. 
Apart from the inherently high sensitivity of the NCI method for pure standard 
solutions, it was found to have additional advantages in real samples with matrix 
underground. Due to its high selectivity, all MS traces showed very clean baselines with 
little chemical noise. Examples of this are shown in Figure 29.