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FDSN 507 Midterm 2
Chromatography
Chromatography is used as a _____ technique. | seperation |
Define extraction. | Transfer of solute from one liquid phase to another, |
Name three different types of extractions. | Batch, continuous, counter-current |
Counter-current extraction is the basis for ____ chromatography. | partition |
Describe batch extraction. | Solute is extracted with solvent by shaking it with a second, immiscible solvent. |
T or F: At equilibirum, the partition coefficient (K) is constant. | True |
Define chromatography. | Separation techniques based on partitioning of a solute between mobile phase and stationary phase. |
The relative interaction of solute with mobile and stationary phases is described by _____. | partition coefficient. |
T or F: A gas can be in the stationary phase. | False |
Chromatography methods have retention which varies with ____ and _____. | molecular size, polarity |
____ chromatography is used to separate thermally stable volatiles. | GC |
What three characteristics are volatiles separated by in GC? | Boiling point, molecular size, polarity |
Supercritical fluids have high ____ and low ____. | diffusivity, viscosity |
What is supercritical fluid chromatography used to separate? | Non-polar and non-volatile compounds |
The stationary phase for supercritical fluid chromatography is similar to _____; equipment is similar to ____ and detector is similar to ____. | HPLC, HPLC, GC |
Describe liquid chromatography. | Involves a liquid mobile phase and a solid or liquid stationary phase. |
Components of a mixture in paper chromatography are characterized by their _____. | relative mobility |
Define Rf value. | Distance moved by the component/distance moved by solvent |
Which Rf value will be higher, that of a more polar or less polar compound? | Polar |
What are the advantages to TLC over paper chromatography? | Better resolution, faster, more reproducible. |
What technique would you use to screen corn and peanuts for mycotoxins before processing? | TLC |
What three ways can separation occur in TLC? | Adsorptive, partition, ion exchange |
What thee ways can TLC be visualized? | Colorimetrically, emitted radiation, radioactivity |
A ____ can be used to quantitatively measure TLC. | densitometer |
In column chromatography, the mobile phase is ____ while the stationary phase is ____. | liquid, solid |
Define isocraticin column chromatography. | Constant mobile phase composition. |
Define gradient in column chromatography. | Changing nature of mobile phase. |
How are solutes separated in column chromatography? | Based on strength or interaction with stationary phase. |
A detector response for column chromatography is recorded as a _____. | chromatogram |
T or F: The adsorption coefficient is constant in comparison to partition coefficient. | False |
T or F: More polar solutes elute first in adsorption chromatography. | False |
What is the principle of adsorption chromatography? | Separates non polar compounds based on the number and type of functional groups present. |
What technique would you use to separate fat-soluble pigments and vitamins? | Adsorption chromatography |
In partition (liquid/liquid) chromatography, when the most polar phase is held stationary this is called stationary _____ phase chromatography. | normal |
In partition (liquid/liquid) chromatography, when the least polar phase is held stationary this is called stationary _____ phase chromatography. | reversed |
What is the disadvantage to partition chromatography? | The liquid stationary phase is often stripped off (overcome with bonded supports). |
What three intermolecular interactions are responsible for adsorption chromatography? | Electrostatic forces, hydrogen bonds, hydrophobic interaction |
Ion exchange chromatography involved ____ interactions between the solute and the stationary phase. | electrostatic |
What are the four types of ion-exchangers? | cation (binds anions), anion (binds cations), polystyrene, polysaccharide |
How can solutes bound to an ion-exchanger be eluted? | Change the mobile phase pH, increase ionic strength of mobile phase. |
Name three items which can be separated using ion-exchange chromatography. | Amino acids, sugars, proteins, drugs, fatty acids |
Describe solid-liquid chromatography. | Separation occurs based on interaction between a solute and an immobilized ligand. |
A ____ holds the ligand away from the support surface in affinity chromatography. | spacer arm |
T or F: The ideal stationary phase in affinity chromatography does not absorb anything. | True |
What are three non-specific elution methods for affinity chromatography? | Changing pH, ionic strength, temperture |
What is affinity chromatography used to separate? | enzymes, glycoproteins |
What are the four types of interactions present in affinity chromatography? | Hydrophobic, electrostatic, hydrogen bonding, van der waals |
T or F: Large molecules move fastest in size-exclusion chromatogrpahy. | True |
What type of chromatography would be used to separate proteins? | Size-exclusion |
Define void volume. | The volume of the mobile phase in a column. |
Define elution volume. | The volume required to elute a certain solute. |
What are the four types of interactions present in size-exclusion chromatography? | Hydrophobic, electrostatic, hydrogen bonding, covalent bonding |
What four things must be considered in deciding on a separation technique? | Stationary phase, mobile phase, elution conditions, detection method |
What three characteristics define a chromatographic peak? | Retention time, peak width, peak height |
Resolution is a function of ____, _____, and _____. | efficiency, selectivity, capacity |
The number of theoretical plates is generally proportional to ______ in chromatographic resolution. | column length |
How are chromatographic peaks qualitatively analyzed? | Compare retention time to standards under identical conditions to identify unknown compounds. |
How are chromatographic peaks quantitatively analyzed? | External and internal standards. |
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