Instrumental methods in electrochemistry Flashcards

a chemical reaction in which we apply a voltage to drive a redox reaction that would not otherwise occur

it is a one that can be oxidized or reduced at an electrode.

analyte is plated out on an electrode and weighed.

1. Disappearance of color

2. Deposition on freshly exposed electrode surface

3. Qualitative test for analyte in solution

• electrons participating in a chemical reaction are counted to learn how much analyte reacted.
• the quantitative determination of any substance that can be made to undergo an electrochemical reaction with 100% current efficiency, i.e. the number of Coulombs required to carry out a chemical reaction is measured (integration is needed).

• the measured electric current between a pair of electrodes that are driving an electrolysis reaction.
• we measure an electric current that is proportional to the concentration of a species in solution

an electrode that measures ambient oxygen partial pressure in a liquid using a catalytic platinum surface according to the net reaction

a device that uses a biological component such as an enzyme or anti- body for highly selective response to one analyte.

transports electrons between analyte and the working electrode. The mediator undergoes no net reaction itself.

• Provides fixed reference potential with negligible current flow
• an electrode which has a stable and well-known electrode potential.

• Controls potential difference between working and reference electrodes
• an analytical instrument designed to control the working electrode's potential in a multiple electrode electrochemical cell.

• Analyte reacts here, voltage is measured between working and reference electrodes
• the electrode in an electrochemical system on which the reaction of interest is occurring.

• Other half of the electrochemistry occurs here, current flows between working and auxiliary electrodes
• An electrode that serves merely to carry the current flowing through an electrochemical cell
• also called a counter electrode

• current is measured while voltage between two electrodes is varied.
• the study of the current response of a chemical under an applied potential difference.

• a voltammetry conducted with a dropping-mercury electrode.
• an instrumental method of chemical analysis used for qualitative and quantitative determinations of reducible or oxidizable substances

is a graph of current versus voltage

The potential at which half the maximum current is reached

• The constant current in the plateau region
• because it is limited by the rate of diffusion of analyte to the electrode. For quantitative analysis, diffusion current is proportional to the concentration of analyte.

the absence of analyte due mainly to reduction of impurities in the solution and on the surface of the electrodes

• The current that we seek to measure in voltammetry due to reduction (or oxidation) of analyte at the working electrode.

• Due to migration of ions toward or away from an electrode because of electrostatic attraction or repulsion; redox reactions have no role in charging current
• interferes with every measurement

• Increased signal

• Derivative (peak) shape provides better resolution of neighboring signals

•Faster measurements

1. Concentrate analyte into a drop of Hg by reduction.

2. Reoxidize analyte by making the potential more positive.

3. Measure polarographic signal during oxidation.