Liquid Chromatography

Front 1

Analyte property - size

Back 1

size exclusion chromatography

Front 2

analyte property - shape

Back 2

affinity chromatography

Front 3

analyte property - charge

Back 3

ion-exchang chromatogaphy

Front 4

anaylte property - polarity

Back 4

absoption chromatography

liquid/liquid chromatography

Front 5

Moolecular exculsion chromatogrpahy

Back 5

-lacks an attractive interaction bewteen stationary phase and solute
-liquid passes through a porous gel which seperates the molecules according to size.
-pores usually small and exclude larger solute molecules
-allows smaller molecules to enter the gel, causing them to flow at a larger volume
-lafrger molcules pass through the column at a faster rate.

Front 6

Affinity chromatography

Back 6

-most selective type of chromatography
-utilizes the specific interaction bewteen one kind of solute molecule and a second moecule that is immobilized on a stationary phase

Front 7

Polar compounds

Back 7

-bonding electrons are not shared evenly
-end of a bond with electrons become partically negative
-end os a bond without electrons becomes partically positive

two ends of a molecules charged with the opposite chrage form a dipole.

Front 8

Ion - dipole forces of attraction

Back 8

-involves a charged ion and a polar molecule-cations attracted to negative
-anions attracted to positve

ION-DIPOLE FORCES ARE IMPORTNAT IN SOLUTION OF IONIC SUBSTANCES IN POLAR SOLVENTS.

Front 9

dipole - dipole forces of attraction

Back 9

- exsists between neutral polar molcules
-partical positive charge of a molecule is next to a partical negative charge on another molcule.
-must be in close proximity

WEAKER THAN ION-DIPOLE FORCES THOUGH FORCES INCREASE WITH AN INCREASE IN THE POLARITY OF A MOLECULE.

Front 10

London dispersion forces

Back 10

- a motion of electrons within an antom or non-polar molceule can result in a transient dipole moment.
-the ease with which an external electrical field can induce a dipole is the polarizability

THE GREATER THE POLARIZABILITY OF A MOLCEULE THE EASIER IT IS TO INDUCE A MOMENTARY DIPOLE AND THE STRONGER THE DISPERSION FORCE

Front 11

hydrogen bonding

Back 11

-hydrogen atoms in a polar bond experiences an attractive force with a neighbouring electronegative molecule or ion with an unshaired pair of electrons.
-formed between hydrogen on an -OH group and electronegative atoms, such as oxygen and nitrogen

Front 12

order of strengths

Back 12

london dispersion < dipole-dipole < hydrogen bonding < ion dipole < ion - ion

Front 13

Absorbtion chromatography

Back 13

-solid stationary phase-liquid/gas mobile phase
-equibibration bwteen the mobile phase absorbed onto the starionary phase accounts for the seperation of diffrent solutes.
-forces attracting solutes to absorbent stationary phase ( dipole-dipole or hydrogen bonding)

Front 14

Elution

Back 14

-The tednecy of a solute to dissolve and move with the mobile phase

Front 15

Displacement

Back 15

when the solvent molcules compete with the solute for the absorption sites on the stationary phase.

Front 16

Absorbents - insouble mobile pahse/inert to solutes

Back 16

1) SILICA GEL - SILICA - SILICA ACID
-Acitves sites of silica gel are the hydroxyl groups attached to the silicon atoms, SILANOL GROUPS.
-form hydrogen bonds with solutes.
-if contains water acts by partion not absoption
2) ALUMINA
-activated by heating at 400c over night

Front 17

Normal phase chromatography

Back 17

-Adsorbent stationary phase is polar and the mobile pahse is relatively non polar
-more polar the analyte the greater the retention time
-increasing polarity of mobile ohase decrease the retention time

Front 18

Reversed phase chromatography

Back 18

-adsorbent stationary phase is non polar and mobile phase is relatively polar.
-less polar the analyte the greater the retention time
-decreasing the polarity of the mobile phase decrease the retention time.

Front 19

Partition Chromatography

Back 19

-thin film formed on the surface of a solid support by a liquid stationary phase
-solute equilibrates between the liquid mobile phase and the stationary phase liquid.
-stationary phase is present as a thing film on an inert solid support

Front 20

ion-exchange chromatography

Back 20

-stationary solid phase (resin) is used to covalently attatched anions or cations to it.
-solute ions of the opposite charge in the mobile phase are attracted to the resin by electrostatic forces

Front 21

Hydrophilic interaction liquid chromatography

Back 21

-seperates polar and hydrophilic compounds including small organic acids or basic drugs.
-retention cause by the partitiong of the analyte solute molecules bwteen the mobile phase eluent and a water-enriched layer in the hydrophilic stationary phase.
-more hydrophilic the more the partitioning equilibrium shifted towards the immoblized water layer in the stationary phase.
-statonary phase divided into 3 different groups, neutral, chared and zwitterionic.
-retention increases with increasing fraction of organic solvent.
-column with hydrophilic stationary phase
-eluent with water, buffer and high concentration of water miscibile organic solvent.

Front 22

High performance liquid chromatogrpahy

Back 22

1)HPLC Columns
-silica or alumina
-bond phases on either alumina or silica
-gels
-controlled pore glasses of silica
2)HPLC detection
- uv absornace; single wavelength or array scanning
-mass spectometry
-florescence
-conductivity
-electrochemical
-refractive index

Front 23

Choice in sample solvent

Back 23

-solubility
-misicibility with eluent
-not a volatile solvent
-minimum effect on detector

Front 24

Choice of elution mode

Back 24

isocratic elution - preformed with a single solvent or constant solvent mixture

gradient elution - continuous change in solvent compositionto increase eluent strength

Front 25

Asymmetrical peaks

Back 25

-contaimination column surface
-high concentration or viscosity of sample
-flow rate to high
- non uniform column packing
-dead space or channeling
-temperature irregularites.

Front 26

Tailing in HPLC

Back 26

-inject less
-inject neautral compounds

Front 27

optimize seperation

Back 27

very early peak elution K' = 1 - increase interaction with the stationary phase

Front 28

incease plate number

Back 28

1) column or stationary phase
- new column with same stationary phase but better packing.
-spherical particles
-longer column
2) chromatography parmeters
-increase of temperature
-decrease of viscosity
-readucing smaple amount

Front 29

Gas Chromatography

Back 29

method of seperation and analysis of complex mixtures of volatile organic and inorganic compounds
- seperates by differences in b.p and by interactions with stationary phase

Front 30

gass - liquid chromatography

Back 30

stationary phase is a liquid dispersed on a solid support.
-seperation achieved by partition of the components of a sample between phases

Front 31

gas - solid chromatography

Back 31

stationary phase is an active solid.
-seperation is acheived by adsorbtion of the somonents of a sample.

Front 32

characteristics of GC injectors

Back 32

-low/no contribution to brand broadening
-introduces representative and homogenous samples
-no discrimination based on differences in analyte
-avoids thermal/catalytic degradation
-good accuracy and precision with a wide range of analyte concentrations

Front 33

GC columns

Back 33

1) packed
- contains finely divided, inert, solid support material
2) open tubular
-inner wallas are coated with thin layer of stationary phase

Front 34

Stationary phase properties

Back 34

-low volatility
-thermal stability
-chemical inetness
-suitable solvent characteristics

Front 35

GC detectors

Back 35

TCD - Thermal conducivity detector
FID - flam ionization detector
MSD - mass selective detector
ECD - electron caption detector
NPD - nitrogen phosphorus detector
FTIRD - fourier transformed infrared detector
AED - atom emission detector

Front 36

peak tailing

Back 36

adsorption effects in the injector or on the columns

clean or replace injector components

Front 37

peak fronting

Back 37

intector or column overload

reduce sample size

Front 38

negative peaks

Back 38

dirty EC detector

remove anode and clan with solvent

Front 39

decomposition

Back 39

component is decomposing in injector or column

check that T of injector and oven are not to high, change column

Front 40

Late peaks

Back 40

peaks from previous sample still eluting

Front 41

memory peaks

Back 41

residual amounts of previous samples are being reintroduced on the column

Front 42

single sovlent peaks

Back 42

column unable to reatin sample components

Front 43

how does mass spec work

Back 43

- finds a way to charge an atom or molecule ( ionization)
-finds a way to seperate ions with different m/z ( for example place charged atoms or molecule into a magnetic field or subject it to an electrical field and measure its speed or radius or curvature relative to its mass-to-charge ratio) (mass analyzer)
-find a way to see the ion that have been produced and seperated ( detector)