Electrogravimetry is a method used to separate and quantify

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s of a substance, usually a

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

. In this process, the analyte solution is electrolyzed. Electrochemical reduction causes the analyte to be deposited on the cathode. The

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

of the cathode is determined before and after the experiment, and the difference is used to calculate the mass of analyte in the original solution. Controlling the

potential Potential generally refers to a currently unrealized ability. The term is used in a wide variety of fields, from physics to the social sciences to indicate things that are in a state where they are able to change in ways ranging from the simple re ...

of the electrode is important to ensure that only the metal being analyzed will be deposited on the electrode. The process is similar to

electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current. The part to be ...

. The phenomenon of polarization exerts a

back EMF Counter-electromotive force (counter EMF, CEMF, back EMF),Graf, "counterelectromotive force", Dictionary of Electronics is the electromotive force (EMF) manifesting as a voltage that opposes the change in current which induced it. CEMF is the EMF c ...

in electrolysis, which reduces the actual EMF of the cell. Thus electrolysis of an electrolyte is possible only when this back EMF is overcome. If two separated platinum electrodes are placed in a dilute solution of

copper sulfate Copper sulfate may refer to: * Copper(II) sulfate, CuSO4, a common compound used as a fungicide and herbicide * Copper(I) sulfate Copper(I) sulfate, also known as cuprous sulfate, is an inorganic compound with the chemical formula Cu2 SO4. It ...

and if a source of potential is applied, no appreciable current will flow through the system, until some minimum potential is applied after which the current will increase as the applied potential increases. The applied voltage which is just sufficient to overcome the back EMF due to polarization and also to bring about the electrolysis of an electrolyte without any hindrance is known as decomposition potential. The decomposition potential Ed is composed of various potentials and is given by: :Ea (min)= Ed= Eb+ Es+ Ev where: *Ea = applied potential *Ed = decomposition potential *Eb = theoretical counter or back potential *Ev = overvoltage. The origins of electrogravimetry date back to the 19th century, when Oliver Wilcott Gibbs, an American chemist, studied the electrolytic precipitation of copper and nickel. This procedure was the first of its kind until Carl Luckow did similar research on electric metal analysis. Today, these two are credited with the invention of the electrogravimetry, known at the time as “electrochemical analysis,” “electroanalysis,” or “electrolytic analysis”. All methods of electrogravimetry involve a traditional

quartz crystal microbalance A quartz crystal microbalance (QCM) (also known as ''quartz microbalance'' (QMB), sometimes also as ''quartz crystal nanobalance'' (QCN)) measures a mass variation per unit area by measuring the change in frequency of a quartz crystal resonator. The ...

(QCM) system in which a sensor is used from an AT cut quartz crystal. The groundwork of the QCM is built upon the notion that any mass delivered on the quartz electrode’s interfacial region can be detected through the resonating frequency of the vibrating quartz crystal. While most vibrational modes occurring in the AT cut quartz are negligible, the vibration mode is known as thickness shear mode. These vibrations are extremely sensitive, which permits accurate detection of atomic interactions near the sensor, allowing these techniques to be used in analytical chemistry . Through combining the techniques of QCM with classic electrochemical techniques, the

electrochemical quartz crystal microbalance Electrochemical quartz crystal microbalance (EQCM) is the combination of electrochemistry and quartz crystal microbalance, which was generated in the eighties. Typically, an EQCM device contains an electrochemical cells part and a QCM part. Two ele ...

(EQCM) was created. EQCM is a new device used to perform the process of electrogravimetry. This device employs a high frequency acoustic wave generated by a piezoelectric resonator to store and dissipate energy infused into the device’s interfacial region. Electrogravimetry has been useful in polymer studies, copper electrodeposition, gold oxidation in an acidic medium, and passivity of iron in a sulfuric medium, as well as Ionic insertion in WO3.

References

Electroanalytical methods {{Analytical-chemistry-stub