Unit 2

Separations, Chromatography

All biological fluids are ___ mixtures

complex

in a solution, the solvent makes up the

majority

in a solution, the solute makes up the

minority

physical process

chemical identity remains the same

we separate mixtures to prevent

interference

positive interference

false positive

negative interference

false negative

qualitative

y/n — characteristic

quantitative

how much?

preparative separations isolate mixture ___ or ____ from sample

components, remove impurities

analytical separations aim to ___ and ___ as many components of a mixture as needed (or as possible)

identify, quantify

gas chromatography

analytical separation of gaseous samples

for GC, all components of a mixture must have BP

< 300 C

How does GC separate mixtures?

phase change and noncovalent interaction

liquid chromatography

analytical separation of liquid samples

for LC, samples contain components with BP

>300 C

How does LC separate mixtures?

noncovalent interactions

for chromatography, the presence of a peak is ___, and the intensity of a peak is ___

qualitative, quantitative

noncovalent interactions

transient or reversable at room temperature

____ is released when a noncovalent interaction occurs

heat

____ is required to break a covalent interaction

heat

Van der Waals

all molecules have this type of noncovalent interaction

Dipole - Dipole

any bonds other than C—C or C—H

Hydrogen bonding

O—H or N—H

weakest nonco bond

Van der Waal

strongest nonco interaction

H bonding

intermediate nonco bond

dipole-dipole

what nonco interactions would CH3CH2Cl have?

Van der Waal, dipole-dipole

Would CH3OCH3 have H bonding?

no, there is no OH bond

Extraction

chromatography primer

immiscible substances

don’t mix with each other

Extractions allow us to

selectively remove mixture components through washes

two types of extractions

solid-liquid

liquid-liquid

immiscible substances stack by

density

Extractions involve

equilibrium

Find Kpart

(mol organic/volume organic) / (mol water/volume water)

reactions must maintain __ before and after

number of moles

Kpart > 1

GOOD — more noncovalent interactions in organic liquid

Kpart = 1

NOT GOOD — equal distribution of noncovalent interactions between water and organic liquid

Kpart < 1

VERY BAD — more noncovalent interactions in water than organic

The favorability of a reaction ____

never changes

Find q (fraction of component remaining in water)

Vol aqueous / Vol aqueous + Vol organic x Kpart

Kpart is concentration-__

independent

find mol component remaining in water

q x mol initial

find q after multiple (n number) extractions

(Vol aqueous / Vol aqueous+ Vol water x Kpart)ⁿ, where n=number of extractions

find number of extractions needed to remove a certain amount of particles from the water

log(q) = nlog(Vol aqueous / Vol aqueous+ Vol water x Kpart), round UP to nearest whole number if decimal

charged species have ____ solubility in organic liquids

limited

to determine if a species may be charged

look for pKa

for charged species, the ___ of the aqueous layer will affect the extraction

pH

find D (distribution coefficient) for deprotonated

Kpart x Ka / Ka + [H3O+]

find D for protonated

Kpart x [H3O+] / [H3O+] + Ka