Sorbents graphitized carbon blacks

The most widely used carbon-based SPE sorbent graphitized carbon black (GCB) with specific surface areas up to 210m /g. Applications of the GCB sorbent in SPE have been extensively studied for polar pesticides in water. Table 10.4 shows the results of recovery values for extraction of 2L of water samples using Ig of GCB comparing with recoveries using C-18 sorbent and liquid-liquid extraction (LLE) with methylene chloride. The recoveries for GCB reach 90% to 100% for most of the compounds. 

Various forms of carbon are used to sample those analytes whose breakthrough volume is too low on Tenax for sufficient preconcentration [8,395-399]. Charcoal, graphitized carbon blacks, and ceurbosieves with wface areas from 5 to 900 w /g are commercially availablJ Bhe high surface area sorbents are used... 

QhEChERS 3 g homogenized sample mixed with water, addition of ACN, NaCl, an. MgS04, centrifugation Clean-up Mix with PSA sorbent, an. MgS04, Cl8, graphitized carbon black, 0.45 pm PTFE filtering... 

In some instances, combinations of Cig and silica columns are also used for better purification of the crude extracts (431, 445). A combination of Cg, silica, and amino solid-phase extraction columns has been successfully employed to fractionate anabolic and catabolic steroid hormone residues from meat in polar and nonpolar neutral and phenolic compounds, and to purify further each fraction effectively (452). Another combination of two solid-phase extraction columns, one using a graphitized carbon black sorbent and the other Amberlite resin in the hydroxyl form, allowed neutral anabolics to be isolated and separated from acidic anabolics and their metabolites (453). A combination of basic alumina column placed in tandem with an ion-exchange column has also been applied for the purification of the crude extracts in the determination of diethylstilbestrol and zeranol (427), and estradiol and zeranol in tissues (450). 

Nonporous mono- and polycrystalline sorbents, (e.g., graphitized carbon black, NaCl). 

One extraction phase developed for triazines is graphitized carbon black, which has been shown to be versatile for a wide range of pesticides (Di Corcia et al, 1987 Di Corcia and Marchetti, 1992 Di Corcia et al., 1993 Bucheli et al, 1997 Crescenzi et al, 1997). It has also been shown to be very effective for retaining the more polar metabolites (e.g., deisopropylatrazine (DIA), deethylatrazine (DEA), and hydroxyatrazine (ATOH) see Table 20.1, also Appendix, Table A3) (Berg et al, 1995 Di Corcia et al, 1997 Pichon et al, 1995 Schulein et al., 1995). The methods published require considerably more column preparation and elution steps than traditional Cl8 methods. Pichon et al. (1995) also included the polar triazine metabolites ammeline, ammelide, and cyanuric acid, with good recoveries using a graphitic carbon sorbent. 

Graphitized carbon black (GCB) materials are frequently used for off-line SPE as well. GCB behaves as a nonspecific sorbent, but because positively-charged adsorption sites are present, it also acts as an anion exchanger, which is useful for the enrichment of acidic compounds [75]. Examples involve the enrichment of chlorinated phenoxy acids [42], aryloxyphenoxypropionic herbicides [45], sulfonylurea herbicides [50], and imidazolinone herbicides [65]. 

Sorbents including several binding mechanisms were represented by, for example, Carbopack B, a graphitized carbon black with positively charged oxonium groups. The graphite structure and anion-exchange sites make it a very selective adsorbent for aromatic anions. 

Graphitized carbon black (GCB) has been reported to be a highly effective sorbent for sample clean-up but also removes structurally planar analytes, limiting its applications. Addition of HOAc to the extraction solvent may help to improve recovery of analytes, but it also inhibits the retention of acidic matrix compounds. Several papers have reported the use of Cl8 for dSPE in veterinary residue analysis. " The use of PSA, NH2, and silica has also been reported. While dSPE does not provide the same degree of clean-up as SPE, it does provide good recovery and reproducibility, coupled with practical and cost advantages. ... 

Solid-phase extraction (SPE) has been used in conjunction with separation techniques [gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE)] for environmental analysis. Recent developments in both SPE and solid-phase microextraction (SPME) have been reviewed. Some of the solid phases investigated previously include graphitized carbon black, octadecylsilica, and Ci8 cartridges. Comparisons of the sorbent materials available for the extraction of phenols have been carried out in conjunction with chromatographic separations. A comparison of polycrystalline graphites and SPME fibers [poly (dimethyl... 

For some years, SPE, an adsorption-desorption technique, has been widely used in procedures of purification, trace enrichment, and class fractionation of phenolics. The SPE extraction of phenolics is usually performed using Cig-bonded silica reversed-phase (RP) sorbents, styrene-divinylbenzene copolymers, or graphitized carbon black, but other new polymeric sorbents such as RP105 and Oasis HLB are successfully used in the separation and preconcentration of phenolic acids. 

The use of carbons as sorbents for preconcentration of pollutants, an application that has much in common with the preceding one, was recently reviewed by Matisova and Skrabakova [23], who investigated the applicability of carbon sorbents (active carbon, graphitized carbon black, molecular sieves, and porous carbon) for preconcentration of organic pollutants in environmental samples and their analysis by GC and HPLC. Another example of an application of carbonaceous materials in which surface chemistry is involved is the reduction of pollutant emissions from aqueous and gaseous media [24]. 

Franken and co-workers [14] separated nitrogen-containing compounds (see Fig. 2-1) on a sorbent composed of 3% phthalocyanine on graphitized carbon black. It is evident that using capillary-type chromatography improves separation (e.g., in the case of 2,3-lutidine, 2,4-lutidine, and 2,5-lutidine) and dramatically reduces the analysis time (by a factor of approximately12). 

The sorbent materials used to make the traps are mainly Tenax, silica gel, activated charcoal, graphitized carbon black (GCB or Carbopack), carbon molecular sieves (carbo-sieve such as Carbosieve-SIII), and Vocarb (Table 23.4). 

Relative strengths of some commonly used sorbents (Markes 2012a). = Graphitized carbon blacks. 

The main types of inorganic sorbents are silica gels, molecular sieves/zeolites, aluminum oxides and magnesium silicates. Carbon-based sorbents include activated charcoals, carbon blacks, graphihzed carbon blacks and graphitized molecular sieves. Styrene-divinylbenzene copolymers, ethylvinylbenzene/divinylbenzene... 

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