Term
| What is gas-liquid chromatography used for? |
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Definition
| Species that are somewhat volatile and thermally stable. |
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Term
| What is liquid adsoption chromatography used for? |
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Definition
| Nonpolar low to moderate molecular mass organics and particularly isomeric organic species. |
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Term
| What is liquid-liquid partition chromatography used for? |
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Definition
| Molecular species that are nonvolatile or thermally unstable |
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Term
| What is reversed-phase partition chromatography used for? |
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Definition
| Most low to moderate molecular mass organic compounds that are nonvolatile or thermally unstable. |
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Term
| What is ion exchange chromatography used for? |
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Definition
| Substances that are ionic or that can be derivatized to form ions. |
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Term
| What is gel permeation chromatography used for? |
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Definition
| High molecular mass compounds that are soluble in nonpolar solvents |
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Term
| What is gas-solid chromatography used for? |
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Definition
| Low molecular mass nonpolar gases. |
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Term
| What is gel filtration chromatography used for? |
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Definition
| High molecular mass hydrophilic compounds. |
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Term
| What is ion-pair chromatography used for? |
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Definition
| Small organic and inorganic ions. |
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Term
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Definition
| the solvent composition is held constant throughout the elution. |
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Term
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Definition
| two or more solvents are used and the composition of the mobile phase is changed continuously or in steps as the separation proceeds. |
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Term
| Define stop flow injection |
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Definition
| the flow of solvent is stopped, a fitting at the head of the column is removed, and the sample is injected directly onto the head of the column. The fitting is then replaced and pumping is resumed. |
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Term
| Define reveresed-phase packing |
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Definition
| is a nonpolar packing that is used in partition chromatography with a relatively polar mobile phase. |
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Term
| Define normal phase packing |
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Definition
| the stationary phase is polar and the mobile phase is relatively nonpolar. |
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Term
| Define ion pairing chromatography |
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Definition
| a large organic counter-ion is added to the mobile phase as an ion-pairing reagent. Separation is achieved either through partitioning of the neutral ion-pair or as a result of electrostatic interactions between the ions in solution and charges on the stationary phase resulting from adsorption of the organic counter-ion. |
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Term
| Define Ion chromatography |
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Definition
| the stationary phase is an ion-exchange resin, and detection is ordinarily accomplished by a conductivity detector. |
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Term
| Define bulk property detector |
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Definition
| responds to some property of the mobile phase (such as thermal or electrical conductivity) that is altered by the presence of analytes. |
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Term
| Define Solute property detector |
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Definition
| responds to some property of analytes, such as absorption or fluorescence. |
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Term
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Definition
| a process for removing dissolved gases from a solution by sweeping the liquid with a stream of fine bubbles of an inert gas of low solubility. |
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Term
| Describe the fundamental difference between ion-exchange and size exclusion chromatography. |
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Definition
In size-exclusion chromatography separations are based upon the size, and to some extent the shape, of molecules with little interactions between the stationary phase and the sample components occurring.
In ion-exchange chromatography, in contrast, separations are based upon ion-exchange reactions between the stationary phase and the components of the sample in the mobile phase. |
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Term
| The length of the column L is the distance from: |
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Definition
| the sample entrance to the detector |
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Term
| The purpose in running a non retained species on a column is to measure: |
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Definition
| The average rate of migration of the mobile phase |
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Term
| As the plate count, N, increases for a column: |
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Definition
| the column efficiency increases |
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Term
| Draw block diagram of a liquid chromatography system |
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Definition
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