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Clinical Chemistry > Module 3c: Electro-analytical methods > Flashcards

Module 3c: Electro-analytical methods Flashcards

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1
Q

concerned with the interplay between electricity & chemistry, electrical quantities like current, potential or charge and chemical parameters such as concentration

A

Electroanalytical techniques

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2
Q

Advantages of electroanalytical methods over other analytical methods include:

A
  1. determination of different oxidation states, not just concentration
  2. exceptionally low detecrion limits
  3. abundance of characterisation information (chemical kinetics)
  4. low cost
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3
Q

The relationship of Electrical potential to resitamce amd current

A 
E = RI
V = IR
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4
Q

Term for the relationship E = RI

A

Ohm’s law

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5
Q

5 types of electroanalytical techniques

A
  1. Potentiometry
  2. Coulometry/Amperometry (current)
  3. Voltammetry
  4. Polarography
  5. Osmometry
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6
Q

cathode or anode:

deonoted by a positive sign

A

cathode

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7
Q

cathode or anode:

electrons are liberated here

A

anode

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8
Q

cathode or anode:

oxidation reaction occurs here

A

anode

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9
Q

cathode or anode:

electrons are consumed here

A

cathode

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10
Q

cathode or anode:

denoted by a negative sign

A

anode

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11
Q

cathode or anode:

reduction reaction occurs here

A

cathode

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12
Q

cathode or anode:

electrons move out

A

anode

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13
Q

cathode or anode:

electrons move in

A

cathode

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14
Q

Electrochemical Cells are made up of

A

two half cells consisting of electrode dipped in electrolyte, connected by a salt bridge

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15
Q

The tendency of an electrode which is in contact with an electrolyte to lose or gain
electrons

A

electrode potential

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16
Q

The standard or reference electrode used to measure electrode potentials

A

hydrogen electrode

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17
Q

Cells in which the reactions are irreversible in nature, and made up of use-and-throw galavanic cells

A

Primary cells

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18
Q

Here, the reactants are consumed for the generation of electrical energy and the cell stops producing an electric current once the reactants are completely depleted

A

Primary cells

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19
Q

Electrochemical cells in which the cell has a reversible reaction, i.e. the cell can function as a Galvanic cell as well as an Electrolytic cell.

A

Secondary cell

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20
Q

Secondary cells are also known as

A

rechargeable batteries

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21
Q

Two primary types of electrochemical cells

A
  1. Galvanic cell (voltaic cell)

2. Electrolytic cell

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22
Q

Galvanic or Electrolytic cell:

chemical energy –> electrical energy

A

galvanic

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23
Q

Galavanic or Electrolytic cell:

electrical energy –> chemical energy

A

electrolytic

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24
Q

Galvanic or Electrolytic cell:

spontaneous redox reactions

A

galvanic

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25
Q

Galvanic or Electrolytic cell:

Input of energy is required for redox reaction to proceed/ non spontaneous

A

electrolytic

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26
Q

Galvanic or Electrolytic cell:

positively charged anode

A

electrolytic

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27
Q

Galvanic or Electrolytic cell:

anode is negatively charged

A

galvanic

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28
Q

Galvanic or Electrolytic cell:

cathode is positively charged

A

galvanic

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29
Q

Galvanic or Electrolytic cell:

cathode is negatively charged

A

electrolytic

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30
Q

Galvanic or Electrolytic cell:

electrons originate from oxidizing species

A

Galvanic

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31
Q

Galvanic or Electrolytic cell:

electrons originate from external source (such as battery)

A

electrolytic cell

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32
Q

Measures - change in electric potential

Constant- current

A

Potentiometry

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33
Q

A form of potentiometry where the potential of the glass electrode is measured as a function of hydrogen ion concentration in the solution.

A

measurement of pH

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34
Q

An analytical technique which converts the activity of a specific ion (dissolved in a solution)
into a voltage (potential), which can be measured by a mV or Ion meter.

A

Ion selective electrode

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35
Q

The sensing part of an ion seoecrive electrode is made up of

A

ion specific membrane coupled with reference electrode

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36
Q

There is a voltage change in the ion selective electrode when

A

there is change in potential after ions comes in contact with electrode

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37
Q

The strength of the net charge measured is _______ to the concentration of the selected ion

A

directly proportional

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38
Q

The high degree of selectivity of Ion specific electrode is due to

A

the high specificity of membrane for one ion

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39
Q

The ion selective electrode works on the principle of :

A

galvanic cell

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40
Q

Three main components of n ISE

A

reference electrode
ion selective membrane
voltmeter

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41
Q

Three main components of ISE measurement

A

inner reference or standard solution
outer analyte or sample solution
thin membrane

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42
Q

Ion selective membrane formed from special ionically conducting glass.

A

Glass membrane electrode

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43
Q

Two most common glass membrane ion selective electrode

A

pH electrode

sodium selective electrode

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44
Q

Ion selective membrane made from relatively insoluble ionically conducting inorganic salts, where only ions that cn introduce themselves to the lattice can interfere

A

Crystalline or solid state membrane electrodes

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45
Q

Two examples of Crystalline or solid state electrodes

A 
Fluoride electrode (doped LaF3 crystal)
Chrploride electrode (silver chloride powder)
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46
Q

Ion selective membrane based on special organic polymer membranes which contain various ion-exchange ionophores incorporated into an inert matrix.

A

Polymer membrane electrodes

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47
Q

Polymer membrane elctrodes are used in measurement of

A

K, Ca, N

48
Q

Ion selective electrodes thag have gas permeable membranes and an internal solution, where gas molecules diffuse across the membrane and react with the solution causing a pH change

A

Gas sensing electrodes

49
Q

Common gas sensing electrodes include:

A

ammonia and Carbon dioxide

50
Q

Ion selective electrodes based on the reaction of an enzyme reacting with a specific
substrate, and the resultant product of this reaction (usually H+ or OH-) is detected by an
electrode such as a pH electrode.

A

Enzyme electrodes

51
Q

Example of enzyme electrode

A

Glucose electrode

52
Q

universally used ISE in the clinical laboratory

A

pH electrode (sensitive to H+)

53
Q

Components of a pH meter

A
  1. indicator electrode
  2. reference electrode
  3. liquid junction
  4. readout meter
54
Q

commonly used reference electrode in pH meter

A

calomel electrode
Mercurous chloride
AgCl

55
Q

Commonly used filling solution for liquid junction due to same mobilities

A

KCl

56
Q

Analytical method converting analyte from one oxidation state to another to measure the flow of electrons per unit of time.

constant: potential

A

Coulometry

57
Q

Coulometry operates on the principle of

A

Faraday’s Law

58
Q

Soultion which has chloride ions interacts with electrode that releases silver ions which attach to Cl. What happens next?

A

Chloride ions are used up = change in electricity

59
Q

measure: concentration of reducible elements through differences in current
increase at a constant rate: voltage

A

polarography

60
Q

Polarography is based on the principle of

A

Ilkovic Equation

61
Q

Similar to polarography except that electrical potential is varied over time.

A

Voltameter

62
Q

defined as the concentration of solutes dissolved in a solvent

A

osmolality

63
Q

Major osmotic substances are:

A 
sodium (half)
chloride
glucose
urea
proteins
ethyl alcohol
64
Q

as osmolality increases, osmotic pressure ________

A

increases

65
Q

as osmolality increases, freezing point ________

A

decreases

66
Q

as osmolality increases, boiling point ________

A

increases

67
Q

as osmolality increases, vapor pressure ________

A

decreases

68
Q

describes the migration of a charged particle under the influence of an electric field.

A

electrophoresis

69
Q

two main types of gel electrophoresis

A

horizontal gel electrophoresis

vertical gel electrophoresis

70
Q

vertical or horizontal gel electrophoresis:

buffer system is dicontinuous

A

vertical

71
Q

vertical or horizontal gel electrophoresis:

contijuous running buffer

A

horizontal

72
Q

vertical or horizontal gel electrophoresis:

has a single separating gel layer only

A

horizontal

73
Q

vertical or horizontal gel electrophoresis:

has two layers: upper stacking gel and lower running/resolving gel

A

vertical

74
Q

vertical or horizontal gel electrophoresis:

uses acrylamide gel

A

vertical

75
Q

vertical or horizontal gel electrophoresis:

uses agarose gel

A

horizontal

76
Q

vertical or horizontal gel electrophoresis:

used mainly in spearating mixtures of DNA and RNA

A

horizontal

77
Q

vertical or horizontal gel electrophoresis:

idelly used in separating proteins

A

vertical

78
Q

positive electrode

A

anode

79
Q

negative electrode

A

cathode

80
Q

Usual pH of medium

A

pH 8.6

81
Q

charge of proteins in 8.6 pH

A

negatively charged

82
Q

proteins move towards what electrode at 8.6 pH

A

anode

83
Q

five factors affecting the velocity of migration

A
  • net charge of particle
  • size and shape of the particle
  • strength of electrical field
  • chemical and physical properties of the supporting medium
  • electrophoretic temperature
84
Q

Three main components of an electrophoresis machine

A
  1. power supply
  2. buffers
  3. support materials
85
Q

Should be able to provide constant current for constany migration rate

A

power supply

86
Q

Molecules, such as protein, whose net charge can be either positive or negative

A

ampholytes

87
Q

two buffer properties that affect the charge of ampholytes

A

pH

ionic strength

88
Q

buffer: more acidic than isoelectric point of ampholyte, more H+
ampholyte: binds H+
charge of analyte :
migrates toward:

A

positively charged, cathode

89
Q

buffer: more basic than pl, less H+
ampholyte: loses H+
charge of ampholyte:
migrates toward:

A

negatively charged

anode

90
Q

4 types of support materials

A
  1. cellulose acetate
  2. agarose gel
  3. polyacrylamide gel
  4. starch gel
91
Q

Support material not commonly used anymore due to dryness and brittleness. it should be soaked to soften which uses more time and more resources

A

Cellulose acetate

92
Q

How cellulose acetate is made

A

cellulose is acetylated to by treating wuth acetic anhydride

93
Q

Support material that has big pores so almost all proteins can pass through. It also has neutral charge so it does not produce electroendosmosis.

A

agarose gel

94
Q

size of molecules allowed in agarose gels

A

> 10nm

95
Q

amount of sample required in agarose gel

A

2 mL

96
Q

Support medium usually used for common proteins only (albumin, globulin) with a small pore separation at the bottom, followed by large pore spacer and with a neutral charge

A

polyacrylamide gel

97
Q

First ever support media that is not commonly used anymore due to technical difficulty in uniform consistency

A

starch gel

98
Q

Support media which involves separation of protein on the basis of charge and molecular size

A

polyacrylamide gel

99
Q

Support media which involves separation of protein on the basis of charge only

A

agarose gel

100
Q

Support media which involves separation of protein on the basis molecular size only

A

cellulose acetate

101
Q

Support media which involves separation of protein on the basis of surface charge and molecular size

A

starch gel

102
Q

Used to visualize the separated fractions in gel electrophoresis

A

Dyes

103
Q

Dye used for serum proteins in generap

A

Amido Black

Ponceau S

104
Q

Dye used for lipoprotein zones

A

Fat red 7B

Sudan Black B

105
Q

the amount of dye taken up by the sample is affected by :

A

typee of protein

degree of denaturation

106
Q

The result of zone electrophoresis and consists of sharply separated zones of a macromolecule.

A

electrophoretogram

107
Q

A detergent with a strong protein-denaturing effect and binds to the protein backbone at a constant molar ratio, unfolding protein into linear chains with negative charge proportional to peptide chain length

A

SDS (sodium dodecyl sulfate) and reducing agent

108
Q

Electrophoresis that eliminates the influence of the structure and charge, and proteins are separated solely based on polypeptide chain length.

A

SDS- PAGE ( sodium dodecyl sulfate- polyacrylamide gel)

109
Q

DNA or RNA molecules separated based on their size, through the movement of negatively charged nucleic acid molecules. Molecules with smaller size move faster and migrate farther compared to longer ones.

A

Agarose gel electrophoresis

110
Q

Refers to the bulk flow of liquid toward the cathode upon application of an electric field and it is superimposed on electrophoretic migration.

A

electro-osmotic flow

111
Q

All positive and negative ions are pulled through in the same direction byelectroosmotic flow, and the analytes separate as they migrate due to their electrophoretic mobility.

A

Capillary electrophoresis

112
Q

Separates protein based on isoelectric points and molecular weights.

A

two-dimensional electrophoresis (2D)

113
Q

Defined as the pH of a solution at which the net charge of the protein becomes zero.

A

isoelectric point

114
Q

First dimension of 2D electrophoresis

A

Isoelectric focusing (separation based on charge)

115
Q

Second dimension of 2D electrophoresis

A

SDS-PAGE (based molecular weight)

Clinical Chemistry (14 decks)

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