Carbowax/divinylbenzene

A procedure involving SPME followed by GC/MS has been developed to determine propanil in water samples. A Carbowax-divinylbenzene SPME fiber is used. Linearity of the calibration curves is attained in the range 0.1-10 ugL in water samples. ... 

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 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

Boyd-Boland and Pawliszyn [77] pioneered the SPME analysis of APEOs by SPME-HPLC using normal-phase gradient elution with detection by UV absorbance at 220 nm. The Carbowax-template resin (CW-TR) and Carbowax-divinylbenzene (CW-DVB) fibres allowed the analysis of APEO with a linear range of 0.1-100 mg L 1. The former coating produced the best agreement between the distribution of ethoxymers before and after extraction. This CW-TR fibre provided a limit of detection for individual AP ethoxamers at the low ppb level. The determination of NP in water by SPME-GC (FID) was accomplished by Chee et al. [78] using a polydimethylsiloxane (PDMS) fibre. The linear range was between 1 and 15 mg L 1 with an estimated detection limit of 0.1 mg L-1. 

Heterocyclic aromatic amines Food Carbowax, carbowax-divinylbenzene, polydimethylsiloxane-divinylbenzene, polyacrylate HPLC-UV... 

In a couple of studies, SPME methods were developed to follow the migration of low molecular weight compounds from bottles for mineral water. Acetaldehyde is a common degradation product of poly(ethylene terephtha-late) formed during the melt condensation reaction and melt processing of PET. A rapid and sensitive SPME method was developed to extract acetaldehyde by inserting the carbowax/divinylbenzene fiber into the inner air-space of PET bottles [81]. The detection limit was 0.5 mLL and relative standard deviation was lower than 7%. The acetaldehyde content of 50 PET bottles was analysed. In another study, the SPME method was developed to determine the terephthalic acid monomer from aqueous solutions [43]. 

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)...

A method based on the use of multiple-headspace (MHS) SPME using a carbowax-divinylbenzene (CW/DVB) fiber (three consecutive extractions of the same sample to minimize the possible matrix effects), showed LODs (S/N = 3) of 0.06qg/L for 4-EG and 4-EP, 0.20qg/L for 4-VG, and 0.12 qg/L for 4-VP, below the sensory thresholds of these compounds in wines (Pizarro et al.,2007). 

Solid phase microextraction (SPME) was used to determine the presence of volatiles in cranberry seed extract. The optimized SF extract was diluted with 5mL of a mixture of dichloromethane and methanol (1 1). A carbowax/divinylbenzene (CW/DVB) fiber was exposed for 60 min to the headspace of the diluted cranberry seed extract. The assembly was kept at 30 C with stirring. The fiber was then desorbed for 5 min in the injection port of an HP 6890 Series GC interfrced with a HP 5973 Series MSD. The injector temperature was maintained at 220 C. The helium flow was kept at 2mL/min. The oven temperature was initially maintained at 40°C for 3 min and then ramped at 4°C/min to 100 C and finally heated to 220°C at 15°C/min. 

FIGURE 9.2 Total ion chromatogram of a spiked water solution (10 ixglX) extracted for 30 min with direct immersion of a carbowax divinylbenzene 65 fim fiber (1) toluidine (2) / -chloroanniline (3) 2,4 and 2,5-dichloroanniline (4) 3,5-dichloroanniline and (5) 3,4-dichloroanniline. (Reproduced with permission from Muller, L., Fattore, E., and Benfenati, E. J. Chromatogr. A, 791, 221-230, 1997. Copyright 1997, Elsevier Science.)... 

Air pollution is a important problem for public health. For air analysis, the National Institute for Occupational Safety and Health specifies exposure limits for amines in industrial air (10 to 30 ng/ml) and for amines in indoor air (10 to 300 pg/ml). The direct SPME could be used to monitor the amounts of the amines extracted from air in the following order Carbowax divinylbenzene CAX(DAB) > poly(acrylate) PA > poly(dimethyl-siloxane) PDMS." °... 

Solid-phase micro-extraction (SPME) first became available to analytical researchers in 1989. The technique consists of two steps first, a fused-silica fiber coated with a polymeric stationary phase is exposed to the sample matrix where the analyte partitions between the matrix, and the polymeric phase. In the second step, there is thermal desorption of analytes from the fiber into the carrier gas stream of a heated GC injector, then separation and detection. Headspace (HS) and direct insertion (DI) SPME are the two fiber extraction modes, whereas the GC capillary column mode is referred to as in-tube SPME. The thermal desorption in the GC injector facilitates the use of the SPME technology for thermally stable compounds. Otherwise, the thermally labile analytes can be determined by SPME/LC or SPME/GC (e.g., if an in situ derivatization step in the aqueous medium is performed prior to extraction). Different types of commercially-avarlable fibers are now being used for the more selective determination of different classes of compounds 100 /rm polydimethylsiloxane (PDMS), 30 /rm PDMS, 7 /rm PDMS, 65 /rm carbowax-divinylbenzene (CW-DVB), 85 /rm polyacylate (PA), 65 /rm PDMS-DVB, and 75 /rm carboxen-polydimethyl-siloxane (CX-PDMS). PDMS, which is relatively nonpolar, is used most frequently. Since SPME is an equilibrium extraction rather than an exhaustive extraction technique, it is not possible to obtain 100% recoveries of analytes in samples, nor can it be assessed against total extraction. Method validation may thus include a comparison of the results with those obtained using a reference extraction technique on the same analytes in a similar matrix. 

SPME fibers (100 mm polydimethylsiloxane (PDMS), 70 mm carbowax-divinylbenzene (CW-DVB), and 75 mm Carboxen-PDMS) were obtained from Supelco (Bellefonte, PA, USA). 

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. 

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. 

Carbowax/divinylbenzene 65 pm Polar, with strong afinlty for alco-... 

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