Water grade type carbons

All solvents and chemicals were HPLC grade. Organic solvents, sodium carbonate (anhydrous), and sodium bicarbonate were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Carbonate buffer, pH = 10.0, was prepared using the sodium carbonate (anhydrous), and sodium bicarbonate. A solution of 0.1 % triethylamine in methanol was made for the elution solvent. Diethylcarbamazine citrate was obtained from Sigma, and used to make stock solutions (St. Louis, MO, USA). The internal standard, 1-diethylcarbamyl-4-ethylpiperazine (E-DEC) was synthesized by the Division of Medicinal and Natural Products Chemistry at the University of Iowa, College of Pharmacy. Ultra-pure analytical grade Type I water was produced by a Milli-Q Plus water system (Millipore Corporation, Bedford, MA, USA). For the extraction of DEC and of its internal standard, Alltech Extract - Clean C18 cartridges, 500 mg with a 2.8 mL reservoir, and a SPE vacuum manifold (Alltech, Deerfield, IL, USA) were used. 

The grade of carbon is an important variable. Coal- or coconut-shell types usually are preferred, with structures that are predominantly micropores and with surface areas of 700-1,200 m g Mean particle diameters are 1-2 mm. The various grades are rated by a dechlorination half-value test (DIN 19603). This determines the depth of the carbon bed that will remove half the chlorine from a flowing stream under standard test conditions. The standard test is performed on chlorinated water, and one must remember that the reaction is slower in brine than it is in water. It is best to base designs on experience or on data produced by the carbon supplier at the temperature and pH of interest. 

Semiconductors. Phosphine is commonly used in the electronics industry as an -type dopant for siUcon semiconductors (6), and to a lesser extent for the preparation of gaUium—indium—phosphide devices (7). For these end uses, high purity, electronic-grade phosphine is required normally >99.999% pure. The main impurities that occur in phosphine manufactured by the acid process are nitrogen [7727-37-9] hydrogen [1333-74-0] arsine [7784-42-17, carbon dioxide [124-38-9], oxygen [7782-44-7], methane [74-82-8], carbon monoxide [630-08-0], and water [7732-42-1]. Phosphine is purified by distillation under pressure to reduce the level of these compounds to <1 ppm by volume. The final product is sold as CYPURE (Cytec Canada Inc.) phosphine. 

The slurry phase, the traditional route to PP, uses Ziegler-Natta type catalyst, a hydrocarbon solvent like hexane or heptane and polymer grade propylene (99.5%). Like the stringent requirements for polyethylene plant feeds, propylene must be high purity. Water, oxygen, carbon monoxide, or carbon dioxide will poison the catalyst. The reaction takes place in the liquid phase at 150—160°C and 100—400 psi. When the isotactic polymer particles form, they remain suspended in the diluent as slurry. The atactic polymers dissolve in the diluent. 

The commercial grade is purified by washing with portions of concentrated sulphuric acid until the acid layer remains colourless, and then with water, sodium carbonate solution and water again. It is dried initially over calcium chloride and then distilled from calcium hydride before use. The fraction b.p. 40-41 °C is collected. Dichloromethane should be stored in a brown bottle away from light over Type 3A molecular sieve. 

All carbons used in this research were pretreated to remove fines by sonication (Bransonic 220, Branson Cleaning Equipment) for 30 seconds followed by a rinse with Type I reagent-grade water (Millipore Corp). Coal-based carbons were then extracted with 2-N HCl in a soxhlet extractor for 42 hours to remove ash components and alkaline impurities. After extraction, the sample was boiled for four hours, then exhaustively rinsed until the pH of the suspension was in the range 5 to 6. All carbon samples were dried at 100 °C under vacuum, and stored in a vacuum desiccator. 

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