Principles of chromatography Flashcards

1
Q

what is chromatography

A

the science of seperation

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2
Q

how do sample components partition

A

according to their relative affinity for the stationary or mobile phase

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3
Q

what are the components to be seperated

A

solute and analyte

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4
Q

what is the partition coefficient also known as

A

distribution co-efficient

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5
Q

define the partition coeffcient

A

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

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6
Q

equation for P

A

P=[organic]/[aqueous]

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7
Q

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

A

hydrophillic

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8
Q

what does it mean if P is greater than 1

A

hydrophobic/lipophillic

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9
Q

why is P useful

A

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

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10
Q

purposes of chromatography

A

analytical
preparative

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11
Q

what is meant by analytical

A

separate and identify compounds
determine the composition

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12
Q

what is meant by preparative

A

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

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13
Q

How does seperation occur

A

analytes move through the mobile phase at different rates

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14
Q

describe the stationary phase in TLC

A

adsorbent matrix

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15
Q

what is TLC

A

thin layer chromatography

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16
Q

adsorbent vs absorbent

A

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

17
Q

materials used for the stationary phase of TLC

A

silica gel
alumina oxide
cellulose

18
Q

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

A

Retention factor

19
Q

describe column chromatography

A

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

20
Q

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

A

Compound A

21
Q

what is a chromatogram?

A

elution profile or detector signal plotted as a function of time

22
Q

define retention time

A

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

23
Q

define resolution

A

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

24
Q

define seperation

A

difference/distance between two close peaks

25
what R value indicates complete seperation
>1.5
26
describe the resolution if there is overlap
no resolution
27
how can baseline resolution be acheived
increasing seperation or making the peaks more narrow
28
how to make peaks more narrow
increase column effciency
29
how to increase seperation
better column selectivity
30
what is the theoratical plate concept
mathematical concept used to describe the efficiency pf a chromtography system -capacity/ability to seperate peaks
31
what is a theoratical plate
hypothetical zone used to conceptuliase the sections of the column at equilibrium for mass transfer between mobile nad stationary phases
32
how are theoratical plates calculated
according to peak width using an equation
33
how are analytes measured
using a detector
34
what does quantitative analysis do
quantify amount
35
what does qualitative analysis do
identify compounds
36
types of chromatography
HPLC GS SFC