Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Separation Techniques in Food Analysis > Unit 2 > Flashcards

Unit 2 Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards
1
Q

what are the most common separation techniques in the lab?

A

extractions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

describe extractions

A
  • allows for the transfer of the analyte(s) of interest from the sample (liquid or solid) to another phase not miscible with the first one
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the principle behind extractions

A

based on the partition/distribution of the analyte between the two phases

depends on affinity with both phases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are 2 major types of extractions?

what techniques are an example of these?

A

solvent extraction:

  • liquid-liquid
  • solid-liquid
  • SFE
  • LPME

solid-phase

  • SPE
  • SPME
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

brewed coffee is an example of what type of extraction?

A

solid-liquid extraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe liquid-liquid extraction (LLE)

A

occurs when a solute is partitioned between 2 immiscible liquids and the system is allowed to attain a thermodynamic equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

in LLE, the chemical of interest is ____

A

solute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

in LLE, what is left after the extraction?

A

raffinate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the two phases in LLE?

A

phase 1: raffinate

phase 2: extractant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what relationships describe the distribution of the solute between the 2 phases in LLE?

what type of constants are these?

A
  1. partition constant
  2. partition ratio/distribution constant

they are thermodynamic constants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

define solvent

A

substances (usually liquids) that acts as a medium for the dissolution of solvents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

define solvation

A

when a solute is dissolved in a solvent and the solvent molecules arrange themselves around molecules of the sulte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does solvation involve?

A
  • bond formation
  • H bonding
  • vander Waals forces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how does solvation affect entropy and thermodynamic stability of the solution?

A

increases entropy and thermodynamic stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe non-polar solvents

A

solvents that consist of molecules with low or no net dipole moments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe polar solvents

A

solvents with large dipole moments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how are dipoles derived

A

from chemical bonds between atoms with large differences in electronegativity

results in a molecule with uneven distribution of the bonding electron cloud about nuclei in the molecule

18
Q

in LLE, the ____ (larger/smaller) the interface area is, the faster the extraction will take place

A

larger interface area = faster extraction

19
Q

how can you increase the interface for the mass transfer (ie. create a faster extraction)

what should you be careful of

A

vigorous shaking of the spearatory funnel

be careful of pressure build up

20
Q

k’ is what?

A

capacity factor

21
Q

beta is what?

A

phase ratio

22
Q

what is the fundamental equation for separation methods driven by equilibrium?

A

Kd = k’ x beta

23
Q

what is distribution ratio (D)?

A

the ratio of total analytical concentration of a solute in the extract (regardless of its chemical form) to its total analytical concentration in other phases

D = C(A phase 2) / C (A phase 1)

24
Q

describe dominant chemical species

A

when pH < pKA

efficiently extracted in organic solvent

25
Q

what is the non-dominant species

A

when pH > pKa

less efficiently extracted in organic solvent

26
Q

what is LPME?

A

liquid phase microextraction

27
Q

what are 3 types of LPME?

A
  1. single drop microextraction
  2. hollow fiber LPME
  3. dispersive liquid-liquid mic
28
Q

what was the soxhlet extraction first used for? by who?

A

determination of milk fat by Franz von Soxlet

29
Q

describe soxhlet extraction

A
  • method which minimizes the use of extraction solvent by circulation
  • thermally labile volatile analytes may be lost
  • potential interference from contaminants from extraction thimbles; may necessitate a blank extraction prior to actual sample extraction
30
Q

describe pressurized liquid extraction (PLE)

A
  • involves use of pressurized liquids/fluids for extraction
  • uses elevated temp and pressures
  • allows extraction solvent to penetrate sample matrix, thus enhancing solvation of solute to be extracted
31
Q

in PLE, what are 2 types of extraction?

A
  1. solubility controlled

2. diffusion controlled

32
Q

what are 3 factors affecting extraction in PLE?

A
  1. solvent type
  2. temp
  3. time
33
Q

in PLE, what are 3 extraction enhancers?

A
  1. drying agents
  2. dispersing agents
  3. other additives
34
Q

how is microwave energy used in microwave assisted solvent extraction

A

to heat molecules in the sample (notably water) by ionic conduction and dipole rotation

35
Q

how does microwave assisted solvent extraction (MASE) work?

A

within in closed vessel systems:

  • heated water expands and generates pressure within the sample
  • increased pressure disrupts sample matrix from inside
  • analytes escape the matrix and be dissolved in the extraction solvent
36
Q

how does the use of solvent in MASE compare with conventional extraction methods?

A
  • MASE uses less solvent

- solvent used maybe be microwave absorbing or non-microwave absorbing

37
Q

what is SFE?

A

supercritical fluid extraction

38
Q

how is a supercritical fluid formed?

A
  • when a substance is heated above its critical temp/point

- fluid would have new properties different from the gas and liquid state

39
Q

how can the “solvent power” of a supercritical fluid be tuned?

A

by varying T and P

40
Q

what is the most commonly used supercritical fluid?

what are some properties?

A

CO2

properties

  • low Tc (critical temp)
  • non-polar
  • non-toxic, non-flammable, non-explosive
  • relatively cheap
  • easily accessible in high purity

Separation Techniques in Food Analysis (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions