What are the 3 main types of columns in HPLC?
analytical
preparative
capillary
note: all packed with small diameter porous particles
5 um, 3.5 um, 1.8 um
What are guards?
short disposable column placed before main column to protect from highly retained materials
What are trends of relationships between particle size, column lengths and N efficiency?
as particle size decreases, efficiency increases so same N can be achieved with shorter length
porous shell columns achieve high N w/ low pressure, w/o decreasing particle size
You can reduce ____ and ____ through a simultaneous reduction in ______ and ______
analysis time; solvent usage; particle size; column length
What are preparative columns used for?
isolate and purify synthetic, biochemical and natural compounds into fractions prior to analysis
What are capillary columns used for?
increase Rs and decrease solvent use
Spherical particles help to produce ____ peaks
symmetrical
What are the properties of silica chromatography particles?
- porous shell, solid core
- porous shell inc Rs and dec P needed w/o reducing small particle size
contains silanol group
Why are porous particles better than semi-porous ones?
porous shell increases the resolution and decreases pressure without needing to reduce particle size
What are common polar and non-polar stationary phases?
Polar
amino - C3+NH2
cyano C3+CN
diol
nonpolar
octadecyl C18
octyl C8
phenyl CH2*3+benzene
Thermostating improves ___ precision
tR
How does high temperature affect HPLC separations?
causes changes in thermodynamics of analyte-stationary phase interaction
- lnk (retention factor) inversely proportional to T
-> lowers tR = faster separations!
- decreases solvent viscosity which reduces mass transfer (lower H and increase N)
-> decrease
Thermostating improves ___ precision
tR