Electrochemistry Lecture Review

Flashcards covering key vocabulary terms and definitions from a lecture on electrochemistry, including types of electrochemical cells, analytical methods, and specific electrodes.

Electrochemistry

The study of electricity by chemical action due to the presence or flow of electrons.

Electrochemical Cells

Consist of two half-cells with a salt bridge connecting them, or two electrodes immersed in a salt solution within one large beaker.

Galvanic Cells

Electrochemical cells where there is a spontaneous flow of electrons from the electrode with the lowest electron affinity to the cathode, producing electrical energy.

Electrolytic Cells

Electrochemical cells formed when current is forced to flow through a dead cell by creating an external electromotive force.

Reference Electrode

One half-cell that contains a reference solution of an analyte for calibration purposes and is compared to another electrode.

Indicator Electrode

The measuring electrode consisting of an electrode solution with the sample containing the analytes to be measured.

Potentiometry

A method that measures the electrical potential (in volts) between two electrodes (indicator and reference) due to the activity of ions, with no current allowed to flow.

Ion Selective Electrodes (ISE)

Electrodes designed to be selective towards individual ions, with permaselective membranes that control selectivity.

Glass ISE

A type of ISE used for pH and sodium measurements, with varying glass composition for particular ion selectivity.

Polymer Membranes (ISE)

A type of ISE used for potassium, sodium, chloride, and bicarbonate, predominant in modern instrumentation.

Gas ISE

A type of ISE used for analytes such as PCO2, which is a blood gas measurement.

pH Indicator Electrode

Contains a silver wire coated with silver chloride and encased in a glass membrane sensitive to only hydrogen ions.

pH Reference Electrode

Electrodes such as the calomel electrode or silver-silver chloride electrode, which provide a stable voltage.

Calomel Electrode

A commonly used reference electrode made of a paste of mercurous chloride in direct contact with metallic mercury and an electrolytic solution of potassium chloride.

Liquid Junction

A tiny opening at the bottom of a combined electrode, allowing for electrical connection between the reference and indicator electrodes, often using potassium chloride.

Sodium Electrodes

Ion selective glass capillary membranes where sodium ions bind to the membrane, developing a potential proportional to sodium ion concentration.

Potassium Electrode

Ion selective electrode that incorporates valinomycin, a neutral antibiotic, to create a sensor with higher selectivity for potassium over sodium.

PCO2 Electrode

A gas sensing electrode covered by a thin CO2 permeable membrane, which measures the partial pressure of CO2 as a change in pH of a sodium bicarbonate solution.

Direct ISE

A method where whole blood or plasma is used, the sample is not diluted, typically found in blood gas analyzers or point-of-care instrumentation.

Indirect ISE

A method where the sample is diluted before measurement, making results susceptible to errors with lipemia or very high proteins.

Amphiometry

A method that measures the current in an electrochemical cell (a dead cell with an external voltage applied) at a fixed potential difference between working and reference electrodes.

Clark Electrode

The amperometric electrode used for PO2 determination, covered with an oxygen permeable membrane, where reduced oxygen produces a current proportional to its partial pressure.

Co-oximetry

A continuous, non-invasive method that uses multi-wavelength spectrophotometry to measure oxygen by relying on the different absorbent properties of various forms of hemoglobin.

Oxyhemoglobin

Hemoglobin that is bound to oxygen, the primary form measured by co-oximetry.

Henderson-Hasselbalch Equation

Used to calculate the bicarbonate and carbonic acid ratio based on measured pH and pCO2 in blood gas analysis.

Base Excess/Deficit

A measure of the metabolic component of an acid-base disorder, calculated using pH, PCO2, and hemoglobin, indicating metabolic alkalosis (positive) or acidosis (negative).

Coulometry

Related to ampiometry, involves applying a single potential between two electrodes and measuring the amount of electricity or charge produced by an oxidation/reduction process, historically used for chloride detection.