Polar polyacrylate fiber

As indicated above the fiber coatings can range from a rather nonpolar polydimethyl-siloxane to the more polar polyacrylate film. The polydimethylsiloxane phase is used for the determination of nonpolar volatile compounds in water samples [174,175]. In comparison, the polyacrylate fiber is preferred for the extraction of more polar compoimds. The first application of SPME to the analysis of polar compounds was the determination of phenols performed by Buchholz and Pawlisz)m [176]. These authors reported a detection limit at the ng/L level for the GC/FID and GC/MS procedures using a saturated sodium chloride solution at pH 4 to increase the SPME sensitivity. In connection with... 

SPME is based on the partitioning of compounds between a sample and a coated fiber immersed in it. The odorants are first adsorbed onto the fiber (e. g. nonpolar polydimethylsilo-xane or polar polyacrylate) immersed in a liquid food, a food extract or in the headspace above a food sample for a certain period of time. After adsorption is completed, the compounds are thermally desorbed into a GC injector block for further analysis. 

Eor semivolatile analytes, polarity with respect to fiber type was critical. The more polar analytes were best extracted by polar fibers such as polyacrylate and CW-DVB. The less polar analytes were extracted by both polar and nonpolar fibers and, in some cases, were extracted better with the polyacrylate fiber. The functional group that increases polarity was also important. Amines were extracted well with the PDMS-DVB fiber, whereas CW-DVB and polyacrylate were better for other polar functional groups. 

A newer addition is in-tube SPME that makes use of an open capillary device and can be coupled online with GC, HPLC, or LC/MS. All these techniques and their utilization in pharmaceutical and biomedical analysis were recently reviewed by Kataoka.45 Available liquid stationary fiber coatings for SPME include polydimethylsiloxane (PDMS) and polyacrylate (PA) for extracting nonpolar and polar compounds, respectively. Also in use for semipolar compounds are the co-polymeric PDMS-DVB, Carboxen (CB)-PDMS, Carbowax (CW)-DVB, and Carbowax-templated resin (CW-TPR). A few examples of in-tube SPME extractions from biological matrices are shown in Table 1.19 and drawn from Li and coworkers.166... 

Melt spinning is not used for polyacrylics because they are sensitive to high temperatures. They actually begin to decompose before they reach melting temperature. Solution spinning is used instead. The dried polymer is dissolved in a polar solvent like acetone or dimethyl formamide (DMF). The spinning mechanics are otherwise the same, except the solvent is recovered as it vaporizes, immediately after the extrusion through the spinneret. Most acrylics are sold and used in the form of staple fiber. 

Rhodococcus rhodochrous was used for the hydrolysis of both granular PAN and acrylic fibers by nitrile hydratase and amidase (Tauber et al., 2000). Similarly, Agrobacterium tumefaciens (BST05) was found to convert polyacylonitrile into polyacrylic acid by nitrile hydratase and amidase (Fischer-Colbrie et al., 2006). Nitrilase was also used for the surface hydrolysis of PAN from Micrococcus luteus BST20 (Fischer-Colbrie et al., 2007). However, polyamidase from Nocardia farci-nica leads to an increase of polar groups on the surface of PA, which was measured by tensiometry (Heumann et al., 2009). 

The commercially available fibers include polydi-methylsiloxane (PDMS 100, 30, and 7 pm), PDMS-divinylbenzene (PDMS-DVB 65 pm), polyacrylate (PA 85 pm), carboxen-PDMS (CAR-PDMS 75 and 85 pm), Carbowax-DVB (CW-DVB 65 and 75 pm), Carbowax-templated resin (CW-TPR 50 pm), and DVB-CAR-PDMS (50/30 pm). The type of fiber used affects the selectivity of extraction. In general, polar fibers are used for polar analytes, and nonpolar types are used for nonpolar analytes. Selectivity toward target analytes and interferences can be enhanced by surfaces common to affinity chromatography. Fibers can be reused up to 100 analyses or more depending on the sample matrix, on the care of the analyst, and on the applications for which used. 

The crucial part of the SPME is the fiber coating, which provides the enrichment of the solute of interest selectively from the matrix components. Typical SPME fibers are [162,163] poly(dimethylsiloxane) (PDMS), polyacrylate (PA), PDMS-divinylbenzene (PDMS/DVB), Carboxen-PDMS, Carbowax-divinylbenzene (CW/DVB), and Carbowax-templated resin (CW/TPR). According to the principle of alike dissolves like, the more polar fibers (PA, PDMS-DVB, CW-DVB, and CW-TPR) have been found suitable for the extraction of phenols, whereas the PDMS fiber was not satisfactory because of its relative nonpolar nature. According to many publications, the most favorable extraction of phenols is performed using a PA fiber. 

Zhou et al. [180] used a laboratory-made fiber with 25,27-dihydroxy-26,28-oxy (2, 7 -dioxo-3, 6 -diazaoctyl)oxy-p-ferf-butylcalix[4]arene/hydroxy-terminated silicone oil (amide bridged-C[4]/OH-TSO) coating in headspace SPME coupled to GC-EID for the determination of phenolic compoimds in wastewater matrices. They have compared the extraction ability of this new fiber with the commercially available polyacrylate (PA, 85 xm) fiber. They showed that the new calixarene fiber had high affinity for the phenolic compounds due to the introduction of the polar amide bridge in calix[4]arene. The authors have applied the method to determine the phenolic analytes in real wastewater samples and found recoveries ranging from 89.7% to 103.2%. 

Polar fibers Polyacrylate (PA) 85 320 Polar compounds (pesticides and phenols)... 

Similar to the properties of divinylbenzene porous polymer phases higher polarity than Carbowax, and when combined with Carbowax results in a more polar phase like polyacrylate, it is a solid particle that must be carried in a liquid to coat on a fiber. 

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