method.
SBSE Analysis. The stir bar was supplied from Gerstel GmbH
(M€ulheim a/d Ruhr, Germany). A 10 mm long and 3.2 mm o.d. stir bar
with a 0.5 mm thickness of polydimethylsiloxane (PDMS) coating was
used.
The stir bar was conditioned in a glass tube at 300 C for 60 min by
passing helium through the tube (50 mL/min). Sample extraction was
performed by placing 10 mL of sample spiked with internal standards
(final concentration = 1.3 mg/L of each internal standard) in a 20 mL
glass vial, adding a stir bar. The vial was crimped with a PTFE/silicone
septum purchased from Chromacol. The extraction procedure was based
on conditions described by Hora´k (33), stirring at 1000 rpm for 60 min at
roomtemperature.After extraction, the stir bar was removed with forceps,
rinsed briefly in distilled water, and dried with a lint-free tissue.For solvent
back extraction the stir bar was placed into a 350 μL glass insert containing
200 μL of the solvent mixture dichloromethane/hexane, 50:50. This insert
was immersed into a 2 mL vial closed by a PTFE/silicone septum and
stirred at 1000 rpm for 40 min again.
method.
SBSE Analysis. The stir bar was supplied from Gerstel GmbH
(M€ulheim a/d Ruhr, Germany). A 10 mm long and 3.2 mm o.d. stir bar
with a 0.5 mm thickness of polydimethylsiloxane (PDMS) coating was
used.
The stir bar was conditioned in a glass tube at 300 C for 60 min by
passing helium through the tube (50 mL/min). Sample extraction was
performed by placing 10 mL of sample spiked with internal standards
(final concentration = 1.3 mg/L of each internal standard) in a 20 mL
glass vial, adding a stir bar. The vial was crimped with a PTFE/silicone
septum purchased from Chromacol. The extraction procedure was based
on conditions described by Hora´k (33), stirring at 1000 rpm for 60 min at
roomtemperature.After extraction, the stir bar was removed with forceps,
rinsed briefly in distilled water, and dried with a lint-free tissue.For solvent
back extraction the stir bar was placed into a 350 μL glass insert containing
200 μL of the solvent mixture dichloromethane/hexane, 50:50. This insert
was immersed into a 2 mL vial closed by a PTFE/silicone septum and
stirred at 1000 rpm for 40 min again.
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