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Separation Techniques in Food Analysis > Unit 1 > Flashcards

Unit 1 Flashcards

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1
Q

what are examples of naturally occurring substances?

A

water
CHO
peptides
pigments

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2
Q

what are examples of synthetic substances?

A

functional additives
food colorings
flavorings

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3
Q

what are examples of undesirable chemical substances?

A

environmental contaminants
process induced contaminants
agrochemical residues
food contact material residues

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4
Q

define analyte

A

component of a system to be analysed

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5
Q

define matrix

A

components of the sample other than the analyte

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6
Q

define matrix effect

A

combined effect of all components of the sample other than the analyte on the measurement of the quantity

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7
Q

define interference

A

when a specific component is identified to be causing a matrix effect

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8
Q

describe a small molecule

A
  • low molecular wt (below 900Da)
  • simple sugars,
    AAs, FAs
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9
Q

describe a large molecule

A
  • up to several hundreds of thousands of Da

- proteins, complex CHOs

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10
Q

describe polar compounds

give examples

A
  • soluble in water and protic organic solvents

ex:

  • simple sugars
  • oligosaccharides
  • AAs
  • small proteins
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11
Q

describe non-polar compounds

give examples

A

soluble in non-polar organic solvents (hydrophobic)

ex:

  • fats
  • phospholipids
  • sterol
  • liposoluble vitamins
  • carotenoids
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12
Q

when the chemical is hydrophobic, Kow will be… (high/low)

A

high

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13
Q

when the chemical is hydrophillic, Kow will be… (high/low)

A

low

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14
Q

what is Kow? what is the equation?

A

octanol-water partition coefficient

Kow = conc (octanol) / conc (H2O)

measure of the difference in solubility between two compounds, which tells you how hydrophobic or hydrophillic the compound is

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15
Q

define solubility of a solute

A
  • analytical composition of a saturated solution

- expressed in terms of the proportion of a designated solute in a designated solvent

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16
Q

what can solubility be expressed as?

A 
concentration
molality
mole fraction
mole ratio
etc...
17
Q

define a non-volatile compound

give examples

A
  • low vapor pressure or high boiling point

- ex: sucrose, NaCl

18
Q

define a volatile compound

give examples

A
  • high vapor pressure or low boiling point

- ex: essential oils, low molecular wt FAs, flavor compounds

19
Q

what are some challenges of food analysis?

A
  • complex matrices
  • matrix composition may vary among samples (origin and different processes)
  • analyses usually need to be performed within a few hours to a few days to maintain sample integrity and respond quickly to the requester
20
Q

why do analyses usually need to be performed within a few hours/days?

A
  1. to maintain sample integrity (microbiological, physical, chemical degradation)
  2. respond quickly to requester (client’s request, inspection, regulatory compliance)
21
Q

what are some technologies that allow for direct analysis of food components without sample prep/separation?

A
  • X-ray fluorescence
  • infrared spectroscopy and near infrared
  • guided microwave spectrometry
  • magnetic resonance imaging
22
Q

is it possible to analyze food without manipulation? how?

A

yes. Some technologies allow direct analysis of specific food components without sample prep

23
Q

what is the Bruker handheld XRF food scanner?

A
  • type of portable analyzer that doesn’t require sample prep

some tasks includes:

  • salt analysis for iodine
  • milk analysis
  • nutrient verification
  • etc…
24
Q

what are advantages of direct analysis?

A
  • no sample prep = overall shorter analysis time
  • avoidance of cross-contamination
  • large potential for automation
  • less hazardous chemicals
  • less chemical wastes
  • no specific chemical facilities

overall: direct analysis = less manpower, consumables or facilities

25
Q

what are current limitations of direct analysis?

A
  • sensitivity and selectivity
  • surface vs bulk
  • methods not standardized or approved yet by regulatory agencies
  • high instrument costs
26
Q

what does most sample preparation steps involve?

A

separation to isolate the target analyte(s) into a fraction that is more appropriate for analysis

27
Q

define separations

A

process of any scale by which the components of a mixture are separated from each other without substantial chemical modification

28
Q

what did Carl Willhelm Scheele do?

A

first separated citric acid by crystallizing it from lemon juice

29
Q

define partition/distribution

A
  • terms are used synonymously

- describes general process by which the distribution of a solute between phases comes into equilibrium

30
Q

define adsorption

A

the distribution processes that occur between a solute and a phase at the surface of phase

31
Q

define absorption

A

the distribution processes that occur between a solute and a phase within the bulk of the phase

32
Q

define equilibrium

A

thermodynamic state of a system where the parameters that define its properties (eg. activity or concentration of a solute) remain unchanged

33
Q

separation methods may be classified based on what?

A

the driving force for the separation

34
Q

compare/contrast the driving forces in equilibrium and non-equilibrium

A

equilibrium: driving force is what attains the equilibrium

non-equilbrium (kinetic): driving force is the rate at which solutes migrate

35
Q

describe differential centrifugation

which particles will sediment faster/slower?

A
  • particles of different densities or size will sediment at different rates
  • largest and more dense particles sediment the fastest
  • less dense and smaller particles sediment slower
36
Q

what driving forces occur in differential centrifugation?

A

kinetic non-equilibrium forces

it is the driving force which allows solutes to migrate

37
Q

what are equilibrium driven separation methods?

A
  • partition chromatography extraction
  • distillation
  • precipitation
  • crystallization
38
Q

what are kinetic driven separation methods?

A
  • dialysis
  • electrophoresis
  • exclusion chromatography
  • centrifugation
  • filtration
  • sedimentation
  • membrane methods
39
Q

what are hybrid or hyphenated techniques?

what are examples?

A
  • combination of various instrumental methods

ex:

  • gas chromatography mass spectrometry
  • high performance liquid chromatographu with diode array

Separation Techniques in Food Analysis (13 decks)

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