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Environ Sci Pollui Res (2015) 22:19887-19895 
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solvent and weighted. Gravimetric results were used to quan 
tify swelling as the volume increases after extraction relatively 
to the initial polymer volume, taking the loss of oligomers into 
account. Finally, strips were air dried in a fume hood to evap 
orate absorbed solvent and re-weighted. The mass of released 
oligomers was calculated from the initial mass of the strip and 
the mass after extraction and drying. 
In addition, time and temperature of extraction were opti 
mized to achieve the highest release rates of oligomers. There 
fore, (i) time series extraction experiments («=3) where the 
static extraction step increased in 10 min steps from 10 up to 
90 min, at constant temperature (100 °C) and (ii) extraction 
experiments at different temperatures (75, 100 and 125 °C) 
but constant extraction time (50 min) were performed with n- 
hexane/acetone (l:lv/v). 
For a reliable evaluation of the clean-up efficiency with 
ASE, a comparison was made with classical clean-up proce 
dures, e.g. Soxhlet extraction or extraction by shaking 
(Table 3). For comparable results, all clean-up methods were 
performed two times with three strips each cut from the same 
PDMS sheet. 
Sample extraction 
The main aim during extraction and purification of PDMS 
samplers is to achieve good recovery rates of analytes, as well 
as to completely remove non-crosslinked silicone oligomers. 
In order to gain optimized recovery rates of CHCs and PAFls, 
the same organic solvent should be used for the entire extrac 
tion and clean-up process (Fig. 1) to avoid target compound 
losses due to solvent exchange during the extraction process. 
In contrast to the pre-cleaning step (s.a.), where the solvent 
should have a high oligomer release capacity, organic solvent 
for sampler extraction should yield a minimum oligomer 
release. 
Therefore, in a first step, different solvents («-hexane/ace- 
tone (l:lv/v), dichloromethane, acetonitrile and acetonitrile/ 
methanol (2:1 v/v)) typically used for non-polar contaminants 
extraction from passive sampler (Rusina 2009; Schafer et al. 
2010; Smedes and Booij 2012; Shahpoury and Flageman 
2013) were tested twice for their extraction efficiency for an 
alytical target compounds by using ASE. Briefly, ASE cells 
were filled with sea sand as filling matrix and spiked with IS. 
Each sample was extracted in 3 cycles of 5-min static time 
(100 °C) to find the optimal extraction time for a complete 
extraction of analytes. An azeotropic solvent exchange from 
the more polar solvents acetonitrile and methanol to hexane 
was performed with an excess of hexane according to Smedes 
and Booij (2012). 
In a second step, extraction tests were performed on pre 
cleaned PDMS sheets spiked with PRCs (Table 1) in a 
methanol/water mixture (90:10v/v) according to Rusina 
(2009) and shaken for 14 days, while the water content was 
increased to methanol/water (1:1 v/v) after 1 week. Spiked 
PDMS sheets were ASE extracted, whereas each ASE cell 
(100 mL) was filled with six spiked PDMS sheets (1 sample), 
filled up with pre-combusted sea sand (Merck, Darmstadt, 
Germany) and IS. Extraction was performed with optimized 
solvent, temperature and time (1x10 min, 100 °C, hexane/ 
dichloromethane (1:1 v/v)). These PDMS sheets represent the 
fabrication blank with no further transportation or deployment 
in water. 
In a third step, the newly developed method (Fig. 1) was 
applied on field samples which have been deployed in marine 
waters of the German Bight (Fleligoland waters) for 43 days 
and in brackish waters of the Baltic Sea (Fehmam waters) for 
63 days. Field samples comprised each of a set of two de 
ployed sampler and a transport blank and enabled the direct 
comparison of real sampler matrix with laboratory sampler 
blanks. 
All extracts were evaporated to 1 ml by parallel solvent 
reduction and further purified (“Extract purification and anal 
ysis”) prior to GC-MS analysis. 
Extract purification and analysis 
The ASE sample extracts need additional purification steps to 
remove last traces of silicone oligomers and co-extracted ma 
terial (e.g. organic matter) from field samples. Purification 
from co-extracted material was performed by SPE using 
500-mg silica gel. Target compounds were eluted with 
hexane/dichloromethane (70:30, 5 mL) and evaporated to 
1 ml by a gentle stream of nitrogen. Extracts were further 
purified by HPLC-SEC. Co-extracted silicone oligomers were 
separated by F1PLC-SEC (injection volume 0.5 mL) with 
hexane/dichloromethane (80:20), whereby the first fraction 
Table 3 Comparison of different silicone rubber pre-clean-up methods regarding solvent and time 
Clean-up method 
According to reference 
Total solvent (mL) 
Time (h) 
Swelling (%) 
Release of oligomers (%) 
Soxhlet extraction ethylacetate 
Smedes and Booij (2012) 
400 
100 
92 
2.5 
Extraction ethylacetate 
Shahpoury and Hageman (2013) 
400 
48 
76 
2.4 
Extraction n-hexane/acetone (3:1) 
Schafer et al.(2010) 
800 
96 
124 
2.5 
ASE n-hexane/acetone (1:1) 
This study 
169 
1.2 
42 
2.2 
Results of experimental approach using different clean-up methods in regard to swelling and the associated silicone oligomer release in %