MECHANISM OF HYDROPHOBIC BONDING
Compounds are retained by non-polar interactions from polar solvents or matrix environments. They are bound by dispersion forces/van de Waals forces. Elution, or disruption, of the non-polar interactions is achieved by solvents or solvent mixtures with sufficient non-polar character. Some polar solvents, such as acetonitrile have enough non-polar characteristics to disrupt nonpolar binding to cause elution of a compound from the sorbent. Methanol can be used as well, although it should be noted that it will take off both polar and non-polar analytes of interest as well as interferences.
These sorbents are composed of a silica backbone bonded with hydrocarbon chains. It is used to extract compounds which exhibit non-polar or neutral characteristics from complex matrices. The C18 phase is the most widely used for non-polar interactions because of its non-selective nature; C18 will extract a large number of compounds with differing chemical properties. To enhance selectivity, UCT offers a variety of hydrophobic sorbents. Several chain configurations are available as well as endcapped and unendcapped versions.
One can extract alkanes, alkenes, aromatic and neutral compounds using Clean Up® sorbents. These compounds are washed with aqueous solvent with some polar organic solvent included. The compounds are then eluted with solvent ranging from non-polar to polar organic solvents depending upon the analyte.
HYDROPHOBIC SORBENTS & STRUCTURES
Sorbent Structure
C2 Ethyl -SiCH2CH3
C4 n-Butyl -Si(CH2)3CH3
C8 Octyl -Si(CH2)7CH3
C18 Octadecyl -Si(CH2)17CH3
C30 Tricontyl -Si(CH2)29CH3
