1. Electrodes
1.1. Requires at least 2 electrodes
1.2. Working Electrode
1.2.1. Indicator Electrode
1.2.2. Electrode of interest
1.2.3. Active Electrode
1.2.3.1. Metal
1.2.3.2. Electrode metal part of the half-reaction
1.2.4. Inactive Electrode
1.2.4.1. Carbon or Platinum
1.2.4.2. doesn't directly participate in reaction
1.2.5. Cathode
1.2.5.1. Electrons cross the interface from the electrode to a species in solution
1.2.5.2. Cathodic Current
1.2.5.3. Species are reduced
1.2.6. Anode
1.2.6.1. Electrons flow from a solution species into the electrode
1.2.6.2. Anodic Current
1.2.6.3. Species are oxidized
1.3. Reference Electrode
1.3.1. the electrode against which potential of the working electrode is measured/applied
1.3.2. Ideal
1.3.2.1. invariant potential
1.3.2.2. zero impedance
1.3.2.3. no resistive load
1.3.2.4. No leaking
1.3.3. Common
1.3.3.1. Saturated Calomel Electrode
1.3.3.2. Silver-Silver Chloride Electrode
1.3.3.3. Mercury-Mercurous Sulfate Electrode
1.4. Ideal Electrodes
1.4.1. Polarizable
1.4.1.1. Charge accumulated on electrode
1.4.1.2. Like capacitor
1.4.2. Non-Polarizable
1.4.2.1. Charge can leak out of the electrode
1.5. Faraday's Law of Electrolysis
2. Potentiometry
2.1. Measures the potential between the indicator electrode and the reference electrode
2.2. Current is essentially zero
2.3. Indicator electrode changes in response to analyte
2.4. Potential
2.4.1. work needed to bring a positive unit from infinite distance to a point
2.4.2. Potential drops happen at phase boundaries
2.5. Working Electrode
2.5.1. Electrode of first kind
2.5.1.1. pure metal electrode in direct equilbrium with its ion
2.5.1.2. obey Nernst equation
2.5.1.3. Not commonly used
2.5.2. Electrode of second kind
2.5.2.1. metal electrode responds to anion that forms precipitate or complex with metal ion
2.5.2.2. commonly used as reference electrode
2.5.3. Electrode of Third Kind
2.5.3.1. metal electrode responds to another from competition reaction
2.5.4. inert metal electrode
2.5.4.1. Measure redox potential
2.5.5. Membrane Electrode
2.5.5.1. Liquid Membranes
2.5.5.2. Polymer Membranes
2.5.5.3. Glass Membranes
2.5.5.3.1. Protons do not traverse the membrane
2.5.5.3.2. Used to measure Na+ levels in undiluted blood
2.5.5.3.3. Alkaline Error
2.5.6. Gas Sensor
2.5.7. ISFET and coated wire electrodes
2.6. Ion Selective Electrode
2.6.1. Liquid/Polymer
2.6.1.1. Elements
2.6.1.1.1. Internal Reference Electrode
2.6.1.1.2. Filling Solution
2.6.1.1.3. Ion Selective Element
2.6.1.1.4. External Reference Electrode
2.6.1.2. Used to measure electrolyte ions
2.6.1.3. Electrodes can be prepared for both anions and cations
2.7. Error
2.7.1. Liquid Junction Potential
2.7.1.1. Bulk mixing but has ionic permeability, a potential develops
2.7.1.2. Type 1
2.7.1.2.1. same salt
2.7.1.2.2. different concentration
2.7.1.2.3. ion of higher mobility will impart its charge to opposite side
2.7.1.3. Type 2
2.7.1.3.1. one ion in common
2.7.1.3.2. same concentration
2.7.1.3.3. ion of higher mobility will impart its charge to the opposite side
2.7.1.4. Type 3
2.7.1.4.1. no common ions and/or one common ion
2.7.1.4.2. different concentrations
3. What is it?
3.1. any process involving motion of charge
3.2. Can control current or voltage but not both
4. Redox reactions
4.1. Electrochemical Cell
4.1.1. Spontaneous when Ecell is greater than 0
4.1.2. Charge carried by ions
4.1.3. electrons do not go into solution
4.1.4. Galvanic Cell
4.1.4.1. Spontaneous
4.1.4.2. Does Work
4.1.5. Electrolytic Cell
4.1.5.1. Nonspontaneous
4.2. Nernst Equation
4.2.1. Electric potential at non-standard state
4.2.2. Half-cell Potential
4.2.2.1. E=E^0-((RT)/nF)ln((ared)/(aox))
4.2.3. Activity Coefficient
4.2.3.1. higher charge, the greater depression on coefficient by any inert salt
4.2.3.2. Debye-Hucke;
5. Voltammetry
5.1. collection of methods studying the dependence of current on the applied potential at the working electrode
5.2. current from oxidation or reduction is measured
5.3. Change the potential
5.4. i vs E graph is a voltammogram
5.5. Current
5.5.1. Non-faradaic Current
5.5.1.1. Charging Current
5.5.1.2. Not associated with electrochemical reactions
5.5.2. Faradaic Current
5.5.2.1. Associated with electrochemical reactions
5.5.3. Directly proportional to the flux
5.5.4. Direct Measurement of reaction rate
5.5.4.1. Signs only indicate direction
5.5.5. Steady State Current
5.5.5.1. the rates of all reaction steps in a series are the same
5.5.5.1.1. Mass Transfer
5.5.5.2. Current response is not a function of time or scan rate
5.5.5.3. Same Sigmoidal Shape
5.5.5.4. Range depends on rotation rate
5.5.6. Time Dependent
5.5.6.1. Current response is a function of time or scan rate
5.5.6.2. Duck shaped
5.5.6.3. Current is a function of scan rate
5.6. Voltametric Methods
5.6.1. Cyclic Voltammetry (CV)
5.6.1.1. Vary scan rate
5.6.2. AC Voltammetry
5.6.2.1. vary AC Frequency
5.6.3. Microelectrode Voltammetry
5.6.3.1. Vary R0
5.6.4. Rotating Disk
5.6.4.1. Vary Rotation Rate
5.6.4.2. Hydrodynamic Voltammetry
5.6.5. Sampled Current Voltammetry
5.7. Two Electrode System
5.7.1. Working Eletrode
5.7.2. Reference/Counter Electrode
5.7.3. Small Current
5.8. Three Electrode System
5.8.1. Working electrode
5.8.2. Reference Electrode
5.8.3. Counter Electrode
5.8.4. Current passed between WE and CE
5.8.5. Voltage measured between WE and RE
5.8.6. No current passes through RE
5.9. Polarography
5.9.1. Voltammetry with a dropping mercury working electrode
5.9.2. Reproducible results
5.9.3. Good for reductions
5.9.4. Quantitative Analysis
5.9.4.1. the limiting current should be controlled by the rate at which analyte can diffuse to the electrode
5.9.4.2. Convection minimized
5.9.4.3. High concentration of supporting electrolyte is used to minimize migration
5.10. Non-steady State CV
5.10.1. Two peak potentials
5.10.2. Halfwave potentials
5.10.3. Peak Current
5.10.3.1. Randles Sevcik Equation
5.11. Amperometry
5.11.1. Current at the working electrode is proportional to analyte concentration
5.11.2. Current vs Time
5.11.3. Clarke Electrode
5.11.4. Glucose Monitoring
5.11.4.1. 1st Generation
5.11.4.2. 2nd Generation
5.11.5. Faraday's Law