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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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