(5) Ferreira, V.; Pena, C.; Lopez, R.; Crespo, C.; Cacho, J.
Concentration of Small Volumes of Nonpolar Solutions Containing Trace
Volatile Compounds.
J. Chromatogr. A 1998, 824, 195-203.
Abstract
The analytical behaviour of the concentration of extracts under a stream of nitrogen of small volumes of hexane solutions containing volatile analytes has been studied. The proportion of analyte blown off the solution is a function of its bailing point, of its polarity, and of the final volume reached. For similar boiling points, the more polar the compound, the higher the level of losses. If the evaporation progresses to a final volume of 0.01 mi, all the compounds with boiling points below 150 degrees C are lost in proportions higher than 50%. Compounds with boiling points between 150 and 250 degrees C are lost in proportions ranging from 70 to 25%, and only eicosane (b.p. 340 degrees C) is almost fully retained in the solution. The addition of small amounts (5 mg) of dehydrated silica to the evaporating solution allows the evaporation to proceed without noticeable losses of solutes more polar than hydrocarbons. After concentration, the solutes can be easily recovered by adding a small amount of ethanol or a mixture water-ether.