Separation Science 1

• What are the three types of errors in analysis?

  Gross, random, and systematic errors
• What is an example of a gross error?

  Samples being spilled
• What is an example of a random error?

  Poor pipetting technique
• What is an example of a systematic error?

  Repeated inaccuracy in volume measurement
• What is the difference between precision and accuracy?

  • Precision: Closeness of results from repeated measurements
  • Accuracy: Closeness to the known amount of analyte
• What are the definitions of repeatability and reproducibility?

  • Repeatability: Precision under same conditions over time
  • Reproducibility: Precision between different laboratories
• What does selectivity measure in an analytical method?

  Capability to measure analyte in presence of others
• What does sensitivity indicate in an analytical method?

  Responsiveness to small changes in analyte concentration
• What is the equation for a straight line in a calibration plot?

  Y = bx + a
• What does 'a' represent in the equation Y = bx + a?

  Intercept of the line with the Y axis
• What does 'b' represent in the equation Y = bx + a?

  Slope of the line
• What is the formula for concentration?

  [Concentration] = Mass / Volume
• What is the formula relating concentrations and volumes?

  C1V1 = C2V2
• What must be the same units for C1 & C2 and V1 & V2 in the formula C1V1 = C2V2?

  Concentration and volume
• What are the base units for concentration, mass, and volume?

  • Concentration: mole
  • Mass: gram
  • Volume: litre
• What is solvent extraction used for?

  • Separation of components due to unequal solubility
  • Purification of drugs in formulations or biological fluids
• What are the strengths and limitations of solvent extraction?

  Strengths:

  • Simple and economical method

  Limitations:

  • Limited efficiency and selectivity
  • Limited choice of partitioning solvents
• What factors should be considered when selecting an extraction solvent?

  • Efficiency
  • Selectivity
  • Inertness
  • Boiling point
  • Toxicity
• What is the partition coefficient (K) in solvent extraction?

  K = [S]2 / [S]1
• How does pH affect the extraction of weak acids and bases?

  • Adjusting pH alters charge
  • Controls extraction of polar and non-polar species
• What is solid-phase extraction?

  • Isolating and concentrating solutes from large volumes
  • Effective at extremely dilute concentrations

  
• What is chromatography used for?

  • Separation of multiple components in a sample
  • Based on relative affinities between phases
• What are the components of basic column chromatography?

  • Mobile phase: liquid or gas
  • Stationary phase: solid particles in a column

  
• What are the two phases in chromatography?

  Stationary phase and mobile phase

  
• What materials did Tswett use for chromatography?

  Calcium carbonate and petroleum/ether/ethanol
• How does chromatography differ from extraction?

  One phase is moving while the other is stationary
• What is the mobile phase in chromatography?

  A liquid or gas moving through the stationary phase

  
• What is the stationary phase commonly made of?

  Solid particles packed into a column
• What is the basic setup of column chromatography?

  • Tube filled with spherical particles (stationary phase)
  • High purity solvent (mobile phase) passed through
  • Sample (analyte) introduced
  • Analyte retained and eluted over time
• What factors affect the performance of chromatography?

  Particle size, porosity, resolution, molecules, column length
• What are the different forms of chromatography mentioned?

  • Gel filtration
  • Ion exchange chromatography
  • Normal/reversed phase chromatography
  • Affinity chromatography
  • Gas chromatography
• What is the stationary phase in adsorption chromatography?

  Materials containing polar groups like silica gel
• How does separation occur in adsorption chromatography?

  By adsorption of polar groups of analyte onto stationary phase
• What happens when a polar solvent is used in adsorption chromatography?

  Competition occurs between solute and solvent for silica sites
• How does polarity affect the retention time of a drug in adsorption chromatography?

  More polar drugs have longer retention times
• What is the effect of a more polar solvent on drug retention time?

  It results in a shorter retention time
• What happens to the retention time of drugs with stronger polar solvents?

  Retention time decreases for polar drugs
• If 1 mg of phenol is placed on two columns, which solvent elutes it first?

  Methanol elutes phenol first
• In which order would toluene, phenol, and o-hydroxybenzoic acid be eluted?

  Order is toluene, phenol, o-hydroxybenzoic acid
• What is the stationary phase in partition chromatography?

  Silica particles with bonded alkyl groups