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Definition
- The transfer of a solute from one phase to another. - Carried out to: (1) isolate or concentrate the desired analyte; (2) Separate it from species that would interfere in the analysis.
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Term
1. Partition Coefficient: 2. Fraction Remaining: |
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Definition
1. K = [S]2/[S]1 2. K = [S]2/[S]1 = ((1-q)m/V2)/(qm/V1) - After n extractions with volume V2; qn= (V1/(V1 + KV2))2
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Term
| pH Effects on Extraction: |
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Definition
- If a solute is an acid or base, its charge changes as the pH is changed.
- Usually a neutral species is more soluble in an organic solvent and a charged species is more soluble in aqueous solution.
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Term
| Extraction with Metal Chelator: |
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Definition
- Most complexes that can be extracted into organic solvents must be neutral.
- Charged complexes, such as Fe(EDTA)- or Fe(1,10-phenanthroline)32+, are not very soluble in organic solvents
- Selectively complex one ion with an organic ligand and then extract it into an organic solvent.
- Three ligands commonly employed are: Dithizone, 8-hydroxyquinoline, cupferron.
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Term
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Definition
- Most powerful tool in an analytical chemist's arsenal for separating and measure the components of a complex mixture.
- Process in which compounds areseparated from one another by passing them all through a column that retains some compounds longer than others.
- Operates on same principle as extraction, but one phase is held in place while the other moves past it.
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Term
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Definition
- Either a liquid or a gas.
- In gas chromtography, is a gas.
- In liquid chromatography, is a liquid.
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Term
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Definition
| -Either a solid or a viscous liquid coated onto solid particles or onto the inside wall of a hollow capillary column. |
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Definition
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Definition
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Definition
| Filled with particles containing stationary phase. |
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Definition
- Narrow, hollow capillary with stationary phase coated on the inside walls.
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Term
[Types of Chromatography] Adsorption Chromatography- |
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Definition
| -Uses a solid stationary phase and a liquid or gaseous mobile phase: Solute is adsorbed on the surface of the solid particles. |
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Term
[Types of Chromatography] Partition Chromatography- |
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Definition
| - Involves a thin liquid stationary phase coated on the surface of a solid support: solute equilibrates between the stationary liquid and the mobile phase. |
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Term
[Types of Chromatography] Ion Exchange Chromatography- |
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Definition
| - Features ionic gropus such as -SO3- or -N(CH3)3+ covalently attached to the stationary solid phase, which is usually a resin: solute ions are attracted to the stationary phase by electrostatic forces; the mobile phase is liquid. |
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Term
[Types of Chromatography] Molecular exclusion chromatography (Gel filtration)- |
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Definition
| -Separates molecules by size, with larger molecules passing through most quickly |
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Term
[Types of Chromatography] Affinity Chromatography- |
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Definition
| Most selective kind of chromatography, employs specific interactions between one kind of solute molecule and a second molecule that is covalently attached to the stationary phase. |
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Term
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Definition
| - For each component is the time needed after injection of the mixture onto the column until that component reaches the detector. |
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Term
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Definition
- The volume of mobile phase required to elute a particular solute from the column. - Vr = tr * uv |
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Term
| Adjusted retention time, t'r- |
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Definition
-For a solute is the time requried for solute to travel the length of the column beyond the time required by unretained solvent, tm. t'r = tr - tm |
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Term
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Definition
- α will be > 1
- greater relative retention, the greater the separation b/w two components.
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Term
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Definition
- The longer a component is retained by the column, the greater the capacity factor.
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Term
- To monitor performance of a column, measure the:
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Definition
- capacity factor for a standard
- number of plates
- peak symmetry
- Changes above reflect degradation of the column.
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Term
| What two factors contribut to how well compounds are separated by chromatography? |
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Definition
- Difference in elution times between peaks; the further apart the better.
- How broad the peaks are; the narrower the better.
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Term
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Definition
- In quant. anal. a resolution of > 1.5 is desirable.
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Term
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Definition
- More theoretical plates, the narrower the bandwidth when the compound emerges.
- The smaller the plate height, the narrower each eluted peak, and the better the separation.
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Term
| Factors Affecting Resolution: |
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Definition
- Doubling column length increases res. by √2
- Res. increases as α; change the stationary phase in GC or either stationary phase or mobile phase in LC.
- Res. increases as capacity factor increases. Increasing capacity factor is equivalent to increasing the fraction of time spent by the solute in the stationary phase.
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Term
| Advantages of Open Tubular Columns: |
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Definition
- Higher resolution
- Shorter analysis time
- Increased sensitivity
- Lower sample capacity
- Particles in packek column resist flow of the mobile phase, so flow rate cant be very fast
- Open tubular column has higher linearflow rate for same length column
- Allows for longer column that provides 100 times more theoretical plates.
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Term
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Definition
H ≈ A + B/ux + Cux - A- multiple paths
- ux - longitudnal diffusion
- C- Equilibrium time
- A, B, and C are constant for given column and stationary phase.
Packed column: A, B, C ≠ 0 Open Tubular Column: A = 0 Capillary electrophoresis: A = C = 0 |
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