High Performance Liquid Chromatography Lab
Polarity
Polarity in molecules is created by the unequal sharing of electrons, one of the atoms in
the molecule is more electronegative than the other
The unequal sharing of electrons causes one part of the molecule to have a slightly
negative charge, and another part of the molecule to have a slightly positive charge
Polar molecules are attracted and can form bonds with other polar molecules, ions, or
charged molecules
Solubility
“like dissolves like”
–Polar substances dissolve other polar, ionic, or charged substances (water dissolves
sugar, salt, etc)
–Non-polar substances dissolve other non-polar substances
–Most substances fall somewhere on a polarity continuum, being neither strongly polar
or strongly non-polar
The C18 cartridge
Made of small glass beads with long hydrocarbon chains attached
Hydrogen and carbon share electrons equally so hydrocarbons are very non-polar
The most non-polar parts of the Kool-aid solution will be strongly attracted to the
material in the cartridge
Alcohols
2 different alcohols, methanol (CH2OH) and isopropanol (C3H7OH)
4 different concentrations, 5%, 20%, 60%, 100%
Use the lowest alcohol concentration first
The higher the ratio of hydroxyl groups
(-OH) to carbons, the more polar the molecule
Questions:
Rank isopropanol, methanol, and water from highest to lowest polarity.
Water: methanol: isopropanol
Rank the alcohol concentrations from highest to lowest polarity
5%: 20%: 60%: 100%