Chapter 10E - Chromatography

• seperate/identify/quantify components of a mixture • seperates substances based on solubility • polar molecules dissolve in polar solvents vice versa

• solid • fixed position (not moving) • can be polar/non-polar

• moving phase (fluid) • can be polar/non-polar

• mobile phase sweeps over stationary phase, carrying components of the mixture • components seperate based on different relative attractions (adsorption) to the stationary phase and readiness to dissolve (desorption) in mobile phase

• how strongly compound adsorbs onto the stationary phase • how readily it dissolves (desorbs) onto the mobile phhase

• sample is placed at the top of column • mobile phase moves down column • components seperate based on adsorption/desorption • components elute from the column at different rates

Time taken for a component to pass through the column

• components more strongly adsorbed to the stationary phase • has polarity closest to stationary phase

• components least strongly adsorbed onto the stationary phase • component has polarity closest to that of the mobile phase

• qualitative & quantitative technique • mobile phase/sample pumped through tightly packed stationary phase under pressure

• polar stationary phase

• non-polar stationary phase

• beam of light is passed through the sample • recorded light produces a chromatogram

• identity of SP • identity of MP • length of column • temperature of column • mobile phase flow rate • surface area of SP

• retention time • position of the peak • identify components of a mixure (compare time w/ known standards run under same operating conditions)

• area under the peak • uses a calibration curve • compare areas w/ areas for standard samples • higher concentration = greater area (retention time remains the same)

• several standard solutions of component of known concentration are run through the HPLC column under identical conditions • resulting peak areas are then plotted against concentrations to produce a calibration curve • the concentration of the component in the mixture is interpolated from the calibration curve

• mobile phase normally under high pressure (improved peak resolution) • decrease: longer retention time • particles take more time to move through the column due to more interactions b/w particles + stationary phase.

Decreased temperature: * particles move slower * longer retention time * substances will take more time to move through the column (more interactions b/w particles & stationary phase)

A less tightly packed column: * easier for particles to move through * shorter retention time * particles will take less time to move through the column (less interactions)

• small particle size • frequent adsorption/desorption/seperation • larger surface area