Polydimethylsiloxane retracted

Solid-phase extraction devices and applications are evolving rapidly, and novel techniques that stretch the classical definition of SPE are becoming routine. Pawliszyn introduced solid-phase micro extraction (SPME) in 1989,5,14 and a commercial apparatus is available from Supelco (Bellefonte, PA). The SPME apparatus is merely a modified syringe that houses a fused silica optical fiber coated with an immobilized polymer film. The fiber can be exposed for extraction and then retracted for insertion or removal from the sample vial or instrument. Both manual and autosampler devices are available and each can be adjusted for proper fiber depth. Several coatings are available with varying thickness including polydimethylsiloxane, polyacrylate, polydimethylsiloxane/divinylbenzene, and carbowax/divinylben-zene. In contrast to SPE, which is an exhaustive extraction approach, SPME will extract only a fraction of an available analyte, hence it is not suitable for the isolation of impurities and degradants in most applications.15... 

HS-SPME analysis of volatile compounds for food samples was performed according to a previously reported method applied to bread samples [29] with slight modifications. Similar conditions to those proposed by Blanda et al. [4] were used in the study with strawberries. The SPME fiber used was divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/ PDMS) 50/30 pm, StableFlex, 1 cm long mounted to an SPME manual holder assembly from Supelco (Bellefonte, PA) (Fig. 1). Prior to use, the fiber was conditioned by following the manufacturer s recommendations. The needle of the SPME device was inserted into the container through the septum and the fiber was exposed to the food sample headspace for 30 min at room temperature. The fiber was then retracted into the needle assembly, removed from the container, transferred to the injection port of the GC unit and immediately desorbed. 

The SPME apparatus looks like a modified syringe (see Fig. 5) consisting of a fiber holder needle and a fiber assembly, the latter equipped with a 1-2 cm long retractable SPME fiber. The fiber itself is a thin fused-silica optical fiber, coated with a thin polymer film (such as polydimethylsiloxane, PDMS), as shown... 

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