Question

Fluoride Selective Ion Electrode. Describe how a fluoride selective ion electrode measures the fluoride ion concentration and explain why the potential approaches 0 at high concentrations

Answer 1

Operation of the Fluoride ISE

On account of the F ISE, the particle specific layer is a solitary precious stone of Lanthanum Fluoride (LaF3) doped with Europium Fluoride (EuF2) which produces gaps in the gem cross section through which F particles can pass. At the point when drenched in a fluoride arrangement and associated by means of a voltmeter to an AgCl/KCl outer reference terminal inundated in a similar arrangement, the negative F particles in the arrangement go through the gem layer by ordinary dispersion from high fixation to low focus until there is a harmony between the constrain of dissemination and the turn around electrostatic compel because of aversion between particles of comparable charge. On the opposite side of the film there is a comparing develop of positive particles.

The development of negative F particles within the film is adjusted for by Cl particles in the inward reference arrangement getting to be distinctly killed by joining with the Ag/AgCl wire, and electrons are along these lines constrained through the outer wire to the voltage measuring gadget (particle meter or PC interface). The other terminal of the voltmeter is associated with the Ag/AgCl wire of the outer reference cathode. Here, the convergence of electrons causes Ag particles in the filling answer for acknowledge electrons and store on the silver wire and, thusly, Cl particles to stream out into the specimen arrangement.

Take note of that, as a rule, contingent upon the focuses inside and outside the layer and which particle is being measured, every one of the responses depicted above could happen the other way

A fluoride selective electrode : it is a kind of particle specific cathode delicate to the grouping of the fluoride particle. A typical illustration is the lanthanum fluoride terminal.

In the lanthanum fluoride terminal, the detecting component is a precious stone of lanthanum fluoride LaF3, doped with europium fluoride EuF2 to make cross section opportunities. Such a gem is an ionic conductor by temperance of the versatility of fluoride particles which hop between grid opening. An electrochemical cell might be developed utilizing such a precious stone as a film isolating two fluoride arrangements. This cell goes about as a fixation cell with transference where the fluoride transport number is 1. As transference of charge through the gem is solely because of fluoride, the terminal is exceptionally particular to fluoride. The main particle which altogether meddles is hydroxide (OH−). By and large such "antacid blunder" can be kept away from by buffering the specimen to a pH underneath 7.

Some industrially accessible reference cathodes have an inward intersection which minimizes the fluid intersection potential between the specimen arrangement and the electrolyte in the reference terminal (KCl). The inner electrolyte is at settled arrangement and the cathode reaction is given by the Nernst condition:

E = E0 − RT/F ln aF−