CH23 Vocab Flashcards
in chromatography, this parameter is T’r=tr-tm, where tr is the retention time of a solute and tm is the time for mobile phase to pass through the column
adjusted retention time
a technique in which solute equilibrates between the mobile phase and adsorption sites on the stationary phase
adsorption chromatography
a technique in which a particular solute is retained by a column by virtue of specific interaction with a molecule covalently bound to the stationary phase
affinity chromatography
In chromatography, the parameter describing the shape of a peak. B is the distance from the peak apex to the back of the peak measured at 10% of peak height. A is the distance from the peak apex to the front of the peak at 10% of peak height. B/A = 1 is a symmetrical peak. B/A > 1 is tailing, and B/A < 1 is fronting.
asymmetry factor, B/A
occurs in chromatography, when two adjacent peaks are sufficiently resolved that the signal between the peaks returns to the baseline. Allows determination of accurate peak areas.
baseline resolution
a graph showing chromatography detector response as a function of elution time or volume
chromatogram
net transport of a solute from a region of high concentration to a region of low concentration caused by the random movement of molecules in a liquid or gas
diffusion
defined by Fick’s first law of diffusion: J=D(dc/dx), where J is the rate at which molecules diffuse across a plane of unit area and dc/dx is the concentration gradient in the direction of diffusion
diffusion coefficient
in extraction, the equilibrium constant for the process in which a solute is partitioned between 2 phases: solute (in phase 1) and solute (in phase 2)
distribution constant, Kd
for a solute partitioned between 2 phases, the distribution coefficient is the total concentration in phase 1.
distribution ratio
what comes out of a chromatography column ; also called effluent
eluate
solvent applied to the beginning of a chromatography column
eluent
process of passing a liquid or a gas through a chromatography column
elution
process in which a solute is transferred from one phase to another. Analyte is sometimes removed from a sample by extraction into a solvent that dissolves the analyte
extraction
a technique in which the stationary phase has a porous structure into which small molecules can enter but large molecules cannot. Molecules are separated by size, with larger molecules moving faster than smaller ones
gel filtration chromatography
same as gel filtration chromatography
gel permeation chromatography
a technique in which solute ions are retained by oppositely charged sites in the stationary phase
ion-exchange chromatography
motion with a parabolic velocity profile of fluid through a tube. Motion is fastest at the center and zero at the walls
laminar flow
the distance per unit time traveled by the mobile phase
linear velocity
diffusion of solute molecules parallel to the direction of travel through a chromatography column
longitudinal diffusion
net movement of a molecule from one location to another by mechanisms such as diffusion, convection, and deliberate mixing . In chromatography, refers to the movement of solute between the mobile and stationary phases
mass transfer
two liquids that a single phase when mixed in any ratio
miscible
in chromatography, the phase that travels through the column
mobile phase
a hollow capillary column whose inside walls are coated with stationary phase
open tubular column
chromatography column filled with stationary phase particles
packed column
a technique in which separation is based in differences in the solubility of sample components in the stationary phase in gas chromatography and in the mobile and stationary phases in liquid chromatography
partition chromatography
length of chromatography column divided by plate number of the column
plate height
dimensionless number indicative of column performance; calculated as the square of retention time of an analyte divided by the variance of the analyte band
plate number
how close 2 bands in a spectrum or chromatogram can be to each other and still be seen as two peaks; in chromatography it is the difference in retention times of adjacent peaks divided by their width
resolution
in chromatography, the adjusted retention time for a peak divided by the time for a mobile phase to travel through the column
retention factor
the time from injection for an individual solute to reach the detector of a chromatography column
retention time
the volume of solvent needed to elute a solute from a chromatography column
retention volume
in chromatography, the ratio of adjusted retention times for two components
separation factor
treatment of a chromatographic solid support or glass column with hydrophobic silicon compounds that bind to the most reactive Si-OH groups. It reduces irreversible adsorption and tailing of polar solutes
silanization
a technique in which the stationary phase has a porous structure into which small molecules can enter but large molecules cannot. Molecules are separated by size with larger molecules moving faster than smaller ones. also called gel filtration, gel permeation, or molecular exclusion chromatography
size exclusion chromatography
in chromatography the phase that does not move through the column
stationary phase
H=A +B/ux + Cux
A depends on band broadening processes such as multiple flow paths
B depends on the rate of diffusion of solute in mobile phase
C depends on the rate of mass transfer
van Deemter equation
the volume of mobile phase per unit time eluted from the column
volume flow rate
