Carboxen/polydimethylsiloxane

Solid-phase microextraction (SPME) consists of dipping a fiber into an aqueous sample to adsorb the analytes followed by thermal desorption into the carrier stream for GC, or, if the analytes are thermally labile, they can be desorbed into the mobile phase for LC. Examples of commercially available fibers include 100-qm PDMS, 65-qm Carbowax-divinylbenzene (CW-DVB), 75-qm Carboxen-polydimethylsiloxane (CX-PDMS), and 85-qm polyacrylate, the last being more suitable for the determination of triazines. The LCDs can be as low as 0.1 qgL Since the quantity of analyte adsorbed on the fiber is based on equilibrium rather than extraction, procedural recovery cannot be assessed on the basis of percentage extraction. The robustness and sensitivity of the technique were demonstrated in an inter-laboratory validation study for several parent triazines and DEA and DIA. A 65-qm CW-DVB fiber was employed for analyte adsorption followed by desorption into the injection port (split/splitless) of a gas chromatograph. The sample was adjusted to neutral pH, and sodium chloride was added to obtain a concentration of 0.3 g During continuous... 

In the early 90s, a new technique called solid-phase-micro extraction (SPME), was developed (Arthur and Pawliszyn, 1990). The key-part component of the SPME device is a fused silica fiber coated with an adsorbent material such as polydimethylsiloxane (PDMS), polyacrylate (PA) and carbowax (CW), or mixed phases such as polydimethylsiloxane-divinylbenzene (PDMS-DVB), carboxen-polydimethylsiloxane (CAR-PDMS) and carboxen-polydimethyl-siloxane-divinylbenzene (CAR-PDMS-DVB). The sampling can be made either in the headspace (Vas et al., 1998) or in the liquid phase (De la Calle et al., 1996) of the samples. The headspace sampling in wine analyses is mainly useful for quantifying trace compounds with a particular affinity to the fiber phase, not easily measurable with other techniques. Exhaustive overviews on materials used for the extraction-concentration of aroma compounds were published by Ferreira et al. (1996), Eberler (2001), Cabredo-Pinillos et al. (2004) and Nongonierma et al. (2006). Analysis of the volatile compounds is usually performed by gas chromatography (GC) coupled with either a flame ionization (FID) or mass spectrometry (MS) detector. 

The fiber carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB 50/30 xm x 2cm) proved to be optimal in the GC-MS analysis in terms of the maximum signal recorded for each compound and the simpler sampling procedure and operating conditions (ionic strength, sample temperature, adsorption time) (Fedrizzi et al., 2007a). 

Fig.1 Relative peak areas and standard deviations after triplicate headspace extractions of 100-ng 2-cyclopentyl-cyclopentanone standard. Extraction time and temperature was 30 min at 80 °C. Fiber material PA = polyacrylate PDMS = polydimethylsUox-ane CW/DVB = carbowax/divinylbenzene PDMS/DVB = polydimethylsUoxane/divinyl-benzene, CAR/PDMS = carboxen/polydimethylsiloxane. Reprinted from [66] with permission of Elsevier. Elsevier (2004)...

Accurate studies of grape juice and wine matrix effects in the headspace (HS)-SPME analysis of 3-alkyl-2-methoxypyrazines using a triphase fiber divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/ PDMS) was reported by Kotseridis et al. (2008). Also, PDMS/DVB and CAR/PDMS were selected as suitable fibers for analysis of wines (Sala et al., 2002 Galvan et al., 2008 Ryan et al., 2005). The optimized analytical conditions found are described in Table 4.2. 

Also, a HS-SPME-GC/MS method for analysis of 4-ethylcatechol in wine was performed using a triphase divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) fiber after derivatization of the sample with acetic anhydride (Carrillo and Tena, 2007). 

We are interested in trace volatile sampling and measurement with emphasis on odour measurement. Commercially about 11 SPME fibre types are available such as those from Supelco , but in the case of odour (trace volatile) detection in air, we have found that three fibre types are most applicable. These comprise 100 pm polydimethylsiloxane (PDMS), 65 pm polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 75 pm carboxen/polydimethylsiloxane (CAR/PDMS) types. Our previous work has investigated the use of both 100 pm PDMS and 65 pm PDMS/DVB fibre types, and we have adopted the latter after initial screening studies. 

Carboxen/polydimethylsiloxane compounds Carboxen/PDMS Very volatile... 

In the method reported by Fedrizzi et al. (2007), fibers with six different coatings were examined for their extraction efficiency with regard to reductive sulfur containing compounds. Although other light sulfur compounds were included in the current study, the Divinylbenzene/Carboxen-Polydimethylsiloxane (DVB/CAR-PDMS 50/30 im x 2 cm) fiber (Product No. 57298U, Supelco, Bellefonte, PA, USA) provided the best results, and was... 

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. 

LLE, liquid-liquid extraction MAE, microwave-assisted extraction SEE, solid-phase extraction SPME, solid-phase microextraction LPME, liquid-phase microextraction SOME, single-drop microextraction D-LLLME, dynamic liquid-liquid-liquid microextraction SEE, supercritical fluid extraction MIP, molecularly imprinted polymers sorbent SPMD, device for semipermeable membrane extraction PDMS, polydimethylsiloxane coated fiber PA, polyacrylate coated fiber CW-DMS, Carbowax-divinylbenzene fiber PDMS-DVB, polydimethylsiloxane divinylbenzene fiber CAR-PDMS, Carboxen-polydimethylsiloxane coated fiber DVB-CAR-PDMS, divinylbenzene Carboxen-polydimethylsiloxane coated fiber CW-TPR, Carbowax-template resin HS-SPME, headspace solid-phase microextraction MA-HS-SPME, microwave-assisted headspace-solid-phase microextraction HEM, porous hollow fiber membrane PEl-PPP, polydydroxylated polyparaphenylene. 

Carboxen-PDMS, Carboxen-Polydimethylsiloxane (75 pm, 85 pm) DVB-Carboxen, Divinylbenzene/Carboxen (50/30 pm)... 

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