Separations and Purifications

Question 1

Extraction

Answer 1

Transfer of dissolved compounds fr om starting solvent into a solvent which the product is more soluble

Question 2

Inmiscible

Answer 2

Solvents don’t mix so they can be extracted

Question 3

Position of layer is determined by?

Answer 3

Relative densities

Question 4

Rotary evaporator (rovotap)

Answer 4

Evaporate solvent to obtain product alone

Question 5

Wash

Answer 5

Using a small amount of solute to extract and remove impurities

Question 6

Filtration

Answer 6

Isolate solid from liquid and left with filtrate and residue

Question 7

Gravity filtration

Answer 7

Solvent’s weight pulls it through the filter

Question 8

Vaccum filtration

Answer 8

More often used when solid is desired product

Question 9

Recrystallization

Answer 9

Purifying crystals in solution

Dissolve in hot solvent where product only dissolves when hot

Question 10

Distillation

Answer 10

When product is a liquid soluble in solvent- uses differences in boiling point

Question 11

Which liquid will rise first in distillation?

Answer 11

One with the lower boiling point

Question 12

Simple distillation

Answer 12

Boil below 150 C and have at least 25 C difference in boiling point

Question 13

Condensor

Answer 13

What the water is run through to lower temperature

Question 14

Vacuum distillation

Answer 14

When liquid is distilled above 150 C

Question 15

What does the vacuum do?

Answer 15

Lower ambient pressure to decrease temperature that liquid must reach in order to be able to boil (lower bpO

Question 16

Fractional distillation

Answer 16

To separate liquids with boiling points less than 25 C difference
Increase surface area in column-more refined separation

Question 17

Silica gel is highly?

Answer 17

Polar

Question 18

Mobile phase is usually?

Answer 18

Nonpolar

Question 19

Reverse-phase chromatography

Answer 19

Stationary phase is nonpolar, so polar molecules move up plate quickly

Question 20

High Rf values means a more what solvent?

Answer 20

Nonpolar

Question 21

Preparative TLC

Answer 21

Large spot splits into bands and can be scraped off and washed to yield pure compounds

Question 22

What separation technique is best to collect macromolecules and proteins or nucleic acids?

Answer 22

Column chromatography

Question 23

Ion-exchange chromatography

Answer 23

Beads in column coated with charged substances so they attract and bind compounds with opposite charge

Question 24

Size-exclusion chromatography

Answer 24

Beads contain various pores and large compounds move through faster

Question 25

Affinity chromatography

Answer 25

Protein of interest is bound by creating column with affinity for that protein
With receptor (nickel for histidine)
Washed away with free receptor or antibody

Question 26

Gas/Vapor-phase chromatography

Answer 26

Gas is mobile phase

Absorbent is crushed metal or polymer

Question 27

GC compounds must be

Answer 27

volatile: low melting point, sublimable solids or vaporizable solids

Question 28

Mass spectrometer

Answer 28

Used for molecular weight determination- ionization and fragmentation of compounds and run through magnetic field which separates them by mass-to-charge ratio to determine molecular weight
First separate using GC

Question 29

High-performance liquid chromatography

Answer 29

Compounds pass through detector on their way out

Uses liquid under pressure and more sophistictated solvent gradients and temperature