Principles of chromatography

Question 1

what is chromatography

Answer 1

the science of seperation

Question 2

how do sample components partition

Answer 2

according to their relative affinity for the stationary or mobile phase

Question 3

what are the components to be seperated

Answer 3

solute and analyte

Question 4

what is the partition coefficient also known as

Answer 4

distribution co-efficient

Question 5

define the partition coeffcient

Answer 5

ratio of concentrations in a mixture of two immiscible phases at equilibrium

Question 6

equation for P

Answer 6

P=[organic]/[aqueous]

Question 7

what does it mean if the P value is less than 1

Answer 7

hydrophillic

Question 8

what does it mean if P is greater than 1

Answer 8

hydrophobic/lipophillic

Question 9

why is P useful

Answer 9

when looking at reference tables it is easy to hydrophobic or phillic molecules

Question 10

purposes of chromatography

Answer 10

analytical
preparative

Question 11

what is meant by analytical

Answer 11

separate and identify compounds
determine the composition

Question 12

what is meant by preparative

Answer 12

-fractionation
-isolate and purify compounds for collection from a mixture

Question 13

How does seperation occur

Answer 13

analytes move through the mobile phase at different rates

Question 14

describe the stationary phase in TLC

Answer 14

adsorbent matrix

Question 15

what is TLC

Answer 15

thin layer chromatography

Question 16

adsorbent vs absorbent

Answer 16

adsorbent means to stick to the outside
absorbent means to be taken in

Question 17

materials used for the stationary phase of TLC

Answer 17

silica gel
alumina oxide
cellulose

Question 18

what is used to identify or characterise analytes of interest compared to standards/references in TLC

Answer 18

Retention factor

Question 19

describe column chromatography

Answer 19

a solid stationary phase is contained in a cylinderical tube. The sample is loaded into the cylinder. a liquid mobile phase is passed through the cylinder using gravity or high pressure. The sample is seperated according to relative affinity of the compounds to either the mobile or stationary phase

Question 20

if compound A has lower affinity for the stationary phase than compound B which will elute first

Answer 20

Compound A

Question 21

what is a chromatogram?

Answer 21

elution profile or detector signal plotted as a function of time

Question 22

define retention time

Answer 22

time from when the sample is injected into the mobile phase to the apex of the eluting peak

Question 23

define resolution

Answer 23

the difference in rentention times of two closely spaced peaks / distance between peaks divided by the average width of the peaks

Question 24

define seperation

Answer 24

difference/distance between two close peaks

Question 25

what R value indicates complete seperation

Answer 25

> 1.5

Question 26

describe the resolution if there is overlap

Answer 26

no resolution

Question 27

how can baseline resolution be acheived

Answer 27

increasing seperation or making the peaks more narrow

Question 28

how to make peaks more narrow

Answer 28

increase column effciency

Question 29

how to increase seperation

Answer 29

better column selectivity

Question 30

what is the theoratical plate concept

Answer 30

mathematical concept used to describe the efficiency pf a chromtography system
-capacity/ability to seperate peaks

Question 31

what is a theoratical plate

Answer 31

hypothetical zone used to conceptuliase the sections of the column at equilibrium for mass transfer between mobile nad stationary phases

Question 32

how are theoratical plates calculated

Answer 32

according to peak width using an equation

Question 33

how are analytes measured

Answer 33

using a detector

Question 34

what does quantitative analysis do

Answer 34

quantify amount

Question 35

what does qualitative analysis do

Answer 35

identify compounds

Question 36

types of chromatography

Answer 36

HPLC
GS
SFC