Chromatographic Methods Flashcards
Technique in which the components of a mixture are separated based on differences in the rates at which they are carried through a stationary phase by a mobile phase
Chromatography
Solid or liquid film coated on a solid substrate that is fixed in place wither in a column or on a planar surface
Stationary phase
Liquid or gas that moves over or through the stationary phase carrying with it the analyte mixture
Mobile phase
Components of a sample are resolved on a packed column by _____, a process in which components are carried througha stationary phase by the movement of a mobile phase.
Elution
A plot of the detector’s response as a function of elution time (or volume of mobile phase) is called _____
Chromatogram
Time between the sample’s injection and the appearance of a solute peak at the detector of a column
Retention time
Width of a solute’s chromatographic peak at the baseline
Baseline width
Small peak on the left of a chromatogram is for _______: the time required to elute them is called ____
Dead or void time
A quantitative measure of the separation of two chromatographic peaks
Resolution
The amount of time a solute spends in the stationary phase relative to the time it spends in the mobile phase
Retention factor
The relative selectivity of a chromatographic column for a pair of solutes is given by
Selectivity factor
_____ and _____ are widely used as quantitative measures of chromatographic column efficiency.
Plate heights and plate count
In a van deemter equation, constants A, B, and C are
A. Longitudinal difussion, Coefficients of multiple path effects, Mass transfer
B. Coefficients of multiple path effects, Longitudinal difussion, Mass transfer
C. Mass transfer, Longitudinal difussion
B
Van deemter equation is only applicable for packed columns at _____ flow velocities
High
Most common movile ohases for gas chromatography which are chemically inert towards both sample and stationary phase.
He, Ar, N2
A chromatographic column
- packed with stationary phase
- short column length with large ID
- large sample
- poor resolution
Open tubular column
A chromatographic column
- coated with stationary phase
- long column length with small ID
- small amount of sample
- better resolution
Capillary column
5% of the injected sample enters the column
Split injection
Over 98% of injected sample enters the column
Splitless injection
This part of gas chromatography instrument rapidly volatilizes the components in a liquid sample
Heated injection
Temperature control where the column is maintained at constant temperature
Isothermal Programming
Refers to the temperature control that sets oven to increase temperature at a specific time interval
Temperature programming
Oldest GC detector, universal detector that responds to all substances
TCD Thermal Conductivity
Most commonly used general detector used for all organic substances
FID Flame Ionization
GC detector that is sensitive for compounds containing electronegative atoms
ECD Electron Capture
Non-destructive GC Detector, more sensitive than FID for many compounds such as substituted aromatics and cyclic compounds
PID Photomtric Ionization
NPD, a detector for nitrogen- and phosphorus- containing substances is also called _____
Thermionic Specific Detector TSD
GC detector used for nearly all substances that can provide structural and molecular weight information
MS Mass Spectrometry
Identify if GLC or GSC
1. Liquid S phase
2. Solid S phase
3. Uses packed column
4. Used capillary column
5. Partition principle
6. Adsorption principle
7. Shorter retention time
8. Longer retention time
- GLC
- GSC
- GSC
- GLC
- GLC
- GSC
- GLC
- GSC
Of all analytical separation techniques, ____ is widely used because of it’s sensitivity, adaptability, ease of automation, and widespread applicability to substances that are important to industry.
Liquid Chromatography
Aspirates the mobile phase from the solvent resevoir and forces it through the systems column and detector
Pump
An elution with a single solvent or solvent mixture of constant composition
Isocratic elution
An elution with two (or sometimes more) solvent systems that differ significantly in polarity is used
Gradient elution
Automated tools designed to quickly and accurately load samples. It increases the speed and accuracy of sample loading
HPLC Autosamplers
An HPLC includes two columns. ____ is responsible for the separation, and _____ protects it from contamination
Analytical column, guard column
LC detector that respond to some proerty of solutes, such as UV Vis absorbance, fluorescence, or diffusion current
Solute property detectors
LC detector that responds to a mobile ohase bulk property including refractive index, dielectric constant, or density
Bulk-proert detectors
Most widely used type of HPLC wherein the S phase is a second liquid that is immiscible with the liquid mobile phase
Partition Chromatography
The liquid is held in place by physical adsorption in ____, while it’s covalently bonded in _____ chromatography
L-L chromatography, Liquid-bonded-phase
Most useful bonded-phase coatings are ____ formed by reaction of hydrolyzed surface with an organochlorosilane
Siloxanes
Partition Chromatography with polar S phase and nonpolar M phase.
Normal-phase chromatography
Partition Chromatography with nonpolar S phase and polar M phase.
Reversed- phase chromatography
Processes based on exchange equilibria between ions in solution and ions in siliar charges on the surface of an insoluble, high MW solid.
Ion-exchange
Powerful technique particularly applicable to high molecular weight species
Size-exclusion or gel chromatography
Chromatography based on hydrophilic packing
Gel titration
Technique based on hydrophobic packings
Gel permeation
Involves covalently bonding a reagent, the affinity ligand, to a solid support
Affinity chromatography
A hybrid of GC and LC that combines the best features of each. Best method for nonvolatile or thermally unstable species that contain no chromophoric groups
Supercritical fluid chromatography
