Dissolved organic carbon solid-phase extractions

UV—Vis = spectrophotometry CL = chemiluminescence FAAS = flame atomic absorption spectrometry MIP = molecularly imprinted polymer SPE = solid phase extraction DIC = dissolved inorganic carbon DOC = dissolved organic carbon. 

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

After the solution has been cooled, 100 ml. of 4 N hydrochloric acid is added and the solution is evaporated to dryness under reduced pressure (water pump) from a water bath the receiver is cooled in an ice bath. The pale yellow syrupy residue (or crystalline solid) is dissolved in 60-75 ml. of water, and the organic base is liberated by the addition of 50 ml. of 18 N sodium hydroxide solution. The upper (organic) phase is separated, and the lower (aqueous) phase is extracted with two 30-ml. portions of benzene. The combined organic base and benzene extracts are dried over 10 g. of anhydrous granular potassium carbonate (Note 3). After the benzene has been distilled slowly under slightly reduced pressure from a 125-ml. Claisen flask, the pressure is lowered further, and the product is distilled. The yield of colorless /3-phenylethyl-dimethylamine boiling at 97-98°/22 mm. (Note 4) is 22-24.7 g. (74-83%) (Note 5). 

Oxotelluraxanthcnc2 180 mg of 9-oxotelluraxanthene Te, 7e-dichloride are suspended in 10 m/ of diethyl ether, and the suspension is shaken in a separatory funnel with a solution of 240 mg (1.9 mmol) of sodium sulfite and 180 mg (1.3 mmol) of potassium carbonate in 5 ml of water until the suspended solid has dissolved. The organic phase is separated, the aqueous phase is extracted twice with diethyl ether, the organic phases are combined, washed with water, dried with anhydrous magnesium sulfate, filtered, and the solvent evaporated under aspirator vacuum. The residue is recrystallized from bcnzene/dichloromethane yield 120 mg (82%) m.p. 116°. 

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