Question

Analytical Chem Tutorial: High-Performance Liquid Chromatography

Answer 1

\({\bf{Overview:}}\)
- abbreviated HPLC, in contrast to gravity-flow methods. most modern LC is HPLC
- uses high pressure to create flow, more sophisticated than traditional methods
- many different sub-techniques depending on the size and polarity of the solutes you are trying to separate (might go over this in another tutorial 'cause there are a ton of methods)

\({\bf{Optimization:}}\)
- Cm in the van deemter equation is proportional to the square of the diameter of packing particles --> therefore, column efficiency increases as particle size goes down
- extracolumn band broadening: broadening caused as solute interacts through open tubes/pipes connecting the components of the chromatograph, rather than the column itself. can reduce this by reducing the radius of the column

Answer 2

\({\bf{Instrumentation:}}\)
reservoirs: large glass containers that contain solvents
- must be free of dissolved gas/dust/other contaminants, otherwise flow rates become inconsistent and band broadening occurs
ex: sparging - flushing out dissolved gasses using an inert gas
pumping systems
- pulse-free preferred
- low flow rate
ex:
> reciprocating pumps: small chamber, pumps the solvent back and forth with a piston, with 2 valves that alternatively open and close to let solvent in and out
- pulsed
- small internal volume
- high pressure
- adaptable to gradient elution
- large solvent capacity
> displacement pump: large chamber with motorized plunger
- non pulsed
- limited solvent capacity
- hard to change solvents

alternatively use a computer-controlled system that will automatically adjust the flow

Answer 3

going to get back to this later >>