Graphitised carbon black

The sample pretreatment steps for surfactant analysis such as extraction and concentration can be carried out in a variety of ways. Most of the common and well tested procedures have been described by Schmitt [46]. Solid phase extraction (SPE) with C2, Cg or Cis and divinyl benzene resins as well as special phases, e.g. graphitised carbon black (GCB), can be adequate methods, especially for SPE of metabolites from... 

In an area where domestic wastewater was discharged through cesspools, Crescenzi et al. [76] could identify LAS and DATS in a groundwater sample. After preconcentration of the aqueous sample on a graphitised carbon black (GCB) cartridge, co-extracted basic, neutral and weakly acidic compounds were removed from the cartridge by a... 

As stated earlier the procedure for this analysis is based largely on the methods developed by Hangartner.(4) Figure 1 outlines the scheme utilised for sample processing and analysis. In addition to the detection system already discussed the only other significant difference in this work is the choice of adsorbent which is Carbotrap D-l a graphitised carbon black (GCB). The use of GCB s in environmental analysis is well documented in the literature both as column materials and adsorbants. (7, 8) Initial work within Severn Trent confirmed the claimed superiority of GCB s compared with adsorbents based on porous polymers such as Tenax GC. No evaluation of the relative merits of GCB s and activated carbons have been made at this laboratory but tests with the latter are likely in the future. 

These phases are composed of adsorbing materials molecular sieves, alumina, porous glass and gels (such as Chromosorb 100, Porapak and PoraPLOT1 ), and graphitised carbon black. They are mainly used to separate gases or volatile compounds. Capillary columns made by deposition of these materials in the form of very fine particulates are called PLOT (porous layer open tubular) columns. 

This technique seems to have been introduced in late 1998, and consists of extracting organic contaminants from the soil with a solvent, generally sub-critical water, and then passing the extract through a small disc of solid sorbent. The solid sorbents discussed to date include graphitised carbon black [123], styrene-divinyl benzene [124],Carbograph-4 [122] and polyisobutylene [193]. 

Di Corcia [368] used subcritical water (phosphate-buffered) extraction with a graphitised carbon black cartridge to recover terbuthylazine herbicide and its metabolites from soil. 

Samples of atmospheric mercury were obtained by pre-concentration of mercury on columns of graphitised carbon black (Carbotrap). The columns, at ambient temperature, retained mercury vapour and alkylmercury compounds (Bloom and Fitzgerald, 1988). Methylmercury chloride, ethylmercury chloride and dimethylmercury were held on the column at temperatures as high as 29°C and air flow rates as high as 790cm3min 1. At high flow rates and high temperature,... 

Simazine, atrazine herbicides Concentration on graphitised carbon black U V at 220nm ppt range [125]... 

Polyethylene surfactants Graphitised carbon black preconcentration LC-MS with electrospray interface ppt [15]... 

Phenols Acid washed graphitised carbon black, modified with trimesic acid and PEG 20M [243]... 

The adsorption isotherms for carbon black and graphitised carbon black (graphon) are completely different. For graphitised carbon black a step-like adsorption isotherm is... 

The Type VI isotherm, in which the sharpness of the steps depends on the system and the temperature, represents stepwise multilayer adsorption on a uniform nonporous surface. The step height now represents the monolayer capacity for each adsorbed layer and, in the simplest case, remains nearly constant for two or three adsorbed layers. Amongst the best examples of Type VI isotherms are those obtained with argon or krypton on graphitised carbon blacks at liquid nitrogen temperature. 

Carbopak B and C are graphitised carbon black, having siuface areas of 12 and 1(X) mVg, respectively. They e usually modified with a light coating of a polar stationary phase. DifiGcult separations of the Cj to CjQ hydrocarbons can be achieved... 

The attainable enrichment and clean-up in SPE depend primarily on the selectivity and affinity of the sorbent for the selected target analyte or analytes, the sample load capacity for the analytes and the rate of mass transfer to and from the binding sites, the latter affecting the minimum desorption volume and thus the enrichment that can be obtained. Other factors of importance are the reproducibility of the recovery yields and the stability and reusability of the sorbent when online procedures are desired. For hydrophobic analytes satisfactory results are usually obtained using standard reversed phase sorbents. Thus hydrophobised silica (C8, Cl8), styrene-divinylbenzene copolymers (PS-DVB) and graphitised carbon black (GCB) are the conventional sorbent materials used in SPE (Fig. 15.2)... 

The separation of the cis- and trans-isomers of l,2-bis(trimethylsilyl)-, 1-tri-methylgermanyl-2-trimethylsilyl- and l,2-bis(trimethylgermanyl)ethylene is possible by gas-solid chromatography on graphitised carbon black and by gas-liquid chromatography on Chromosorb W supporting Apiezon L, with helium as carrier gas and a thermal conductivity or flame ionisation detector445. 

HEAT CAPACITIES OF ETHYL AND TERTIARY BUTYL ALCOHOLS IN ADSORPTIOLN LAYERS ON GRAPHITISED CARBON BLACK. 

HEAT CAPACITIES OF ALCOHOLS ADSORBED ON GRAPHITISED CARBON BLACK. //ENGLISH TRANSLATION OF ZH. FIZ. 

The amount of adsorption that takes place at each step is evaluated by integrating the difference in the detector response to changes in the effluent composition after it leaves the cell filled with the adsorbent, and a parallel response obtained when the cell is filled with a non-adsorbing solid. This is illustrated in Figure 3 by the concentration profiles obtained for adsorption of n-butanol from n-heptane on a graphitised carbon black (Graphon). 

Figure 3. Computer graphics of (a) changes in the refractive index of the effluent from the adsorption cell filled with the adsorbent, graphitised carbon black, and a non-adsorbing solid (PTFE) and, (b) thermal output of the thermistors measuring heat effects due to interactions at solid-water interface caused by adsorption and desorption of n-butanol from its 10 gf solution in water on 0.0696 g of GRAPHON at 25°C. Flow rate of water carrier - 3 mlh. ...

Figure 3. Simultaneous determination of heats and amount of adsorption/desorption of K2PtCl6 from water on 10.9 mg graphitised carbon black mixed with 90 mg of PTFE at 25°C.

A typical example of the FIAT method applied to the determination of differential enthalpies of adsorption is illustrated in Figure 8 for adsorption of potassium chloroplatinate on a graphitised carbon black. The first injection of 0.2 pmol of K2PtCl6 produced a molar heat of adsorption of 128 kJmoland the fourth injection yielded 31 kJmol k The individual adsorptions occur on surface sites of different activity and reflect the heterogeneity of the surface. On the other hand, similar adsorption experiments on alumina produced relatively low heats of adsorptions emphasising the high affinity for transition metal salts of the polar sites present in graphitised carbons. 

Figure 8. Pulse adsorptions following sequential injections of 20 pi of 0.01 molar aqueous solution of K2PtCl6 (0.2 pmol) into water percolating throught 25.8 mg of graphitised carbon black mixed with PTFE powder. Flow rate of water - 3 mlh, temperature - 20°C.

Later work with various binary liquid mixtures and different types of solids indicated that the flow calorimeter methods of specific surface determination can also be applied to homogenous surfaces represented by graphitised carbon blacks. In this case strong preferential adsorption of long-chain paraffins from n—heptane was used to produce a monolayer and the corresponding heat of adsorption measured the total graphitic basal plane in such carbons [11]. 

Concentration, mmoles Figure 19. Cumulative heats of adsorption on 0.0704 g of graphitised carbon black, from water at 25°C. 

The irmnersion enthalpies of the four activated carbons and of a graphitised carbon black (V3G, surface area 59 m g ), which is used as referraice to obtain the accessible surface area... 

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