175 
6.3.3.2 Blank values 
Water samples 
Chlorpyrifos-ethyl and -methyl, trifluralin, and endosulfan II showed no blank values 
above the limits of detection (LOD). In the internal standard (ISTD) D^endosulfan I 
traces of non-deuterated endosulfan I were found. Thus a blank value is caused in high 
concentrated solutions of ISTD (e. g. 4 ng/L). In lower concentrated ISTD solutions, 
(e. g. 0.4 ng/L) the amount of endosulfan I is below the limit of detection whereby the 
blank value is deleted. 
Table 66: Blank values in water samples 
Trifluralin 
Chlorpyrifos- 
methyl 
Chlorpyrifos- 
ethyl 
Endosulfan 
I 
Endosulfan 
II 
SPE system 3 
<LOD 
<LOD 
<LOD 
<LOQ 
<LOD 
Sea water b 
<LOD 
<LOD 
<LOD 
<LOD 
<LOD 
Internal 
Standard 3 
(0.4 ng/L 
water) 
<LOD 
<LOD 
<LOD 
<LOD 
<LOD 
a : Average of 4 measurements; b : 
Average of 2 measurements 
Sediment samples 
No problems were encountered with blank values in sediment samples. 
Table 67: Blank values in sediment samples 
Trifluralin 
Chlorpyrif os- 
methyl 
Chlorpyrifos- 
ethyl 
Endosulfan 
I 
Endosulfan 
II 
Blank value of 
the system 3 
<LOD 
<LOD 
<LOD 
<LOD 
<LOD 
Silica sand b 
<LOD 
<LOD 
<LOD 
<LOD 
<LOD 
Internal 
Standard b 
(0.1 pg/kgdw) 
<LOD 
<LOD 
<LOD 
<LOD 
<LOD 
a : Average of 2 measurements containing blank values from solvents, rotary evaporator, silica 
gel column, filtration unit; b : Average of 3 measurements