It works as supporting electrolyte. We needs some salt which should not oxidize or reduce within the potential range of the investigated system. Salts should be stable, should not decompose, or oxidize or reduce. It increase the conductivity of the system.

Tetrabutylammonium cation is a supporting electrolyte,suitable for measurements in non-aqueous solvents.

Quite right the tetrabutyl ammonium ion is part of the supporting electrolyte it is commonly used in nonaqueous electrochemical experiments, I tended to use tetraethyl ammonium perchlorate when I did CV experiments. But be careful it can decompose violently, I think it is reported to be an explosive.

I used to make my own out of tetraethyl ammonium chloride and perchloric acid, but be careful when the crude product is contaminated with acid it is more unstable. I used to do several recrysts of my product (by remote control) before drying at 20 oC in high vacuum. The easy way I usedto do a remote control recryst is to put the flask in a cold water bath, then to plug in the waterbath with a long extension lead. The flask is attached to a When the mixture is hot and homogenous then pull out the plug staying on the other side of the room thus keeping a great distance from the flask. Then allow to cool before you go and do anything with the flask.

I used to use the rotary evapourator in my lab to gently mix the water and solid as it heated up, no vacuum is attached to the rotary evapourator it is just used to spin the flask. I used to stop the spinning in the same way by pulling out the plug on my end of the extension lead.

If you want to avoid perchlorate then you can use things like tetrafluoroborate or hexafluorophosphate, but be careful these anions can form HF if they are exposed to water. It is worst when the water is acidic, I found that a 1M solution of NaPF6 will reach a pH of about 1 after standing for 24 hours at 20 oC.

If you have the money and want to avoid explosive anions and the anions which can form HF with ease then you could choose to use (CF3SO2)2N anions. It is also important to keep in mind that the perchlorate salts of many things are very crystaline, the BF4 or PF6 salts tend to be more soluble in many solvents.

• Tetraalkylammonium ions are used for supporting electrolytes in voltammetric studies as they are used to minimize solution resistance. And are considered to be resistant to reduction. This ions increases the rate of the reaction as the carbon chain length from methyl to butyl is decreased and it shows the steady continuity with an Electron transfer reactions, and it also reflects the stability of the alkyl radical which will be initially formed. The rate constant decreases significantly as the carbon chain length decreased

On the flip slide if you were to use a super large cation such as the trioctyl methyl ammonium cation in Aliquat 336 it would not be so good as it would be too large. The diffusion of such a large ion would be slow thus reducing the specifiic conductivity of the salt. Also in 30 % (v/v) solutions of things like aliquat 336 the mixture starts to become viscous. Years ago an electrochemist told me about the time he tried increasing the concentration of the supporting electroyte up and up, he found that at superhigh concentrations the CV of a simple thing like ferrocene changes as the viscosity of the mixture becomes large

Dear Pradeep Ilayaperumal,

TBA acts as a suppoting electrolyte and also increasing the conductivity. This is the role of Tetra butylammonium chloride

Thank you all

Mark has written excellent responses....like a section of a new textbook. Well done!

Well I am glad that Peter likes what I wrote, I keep meaning to finish off writing the book which I want to write. But having a two year old son is a great distraction, while I would be very happy if he grew up to be a genius of chemistry I would be quite happy if he choose another profession.

Enjoy the little guy.... Mine are 34 and 30 and that happened faster than a speeding voltammogram.

 Hi,

I carried out CV measurements with just DCM(Dry) and TBAPF6 to see whether I get some peaks (as a blank) I observe a peak at ~-0.8 V just for the solvent and supporting electrolyte. What could be the peak? Is it because of dissolved oxygen content? or is the electrolyte breaking down? or is the solvent a bad choice? Should I vacuum dry the electrolyte prior to use? my potential range -1.2V to +1.5V

This depends on both the solvent and electrode material. Oxygen would be a good possibility. Purging with inert gas such as dry nitrogen will reduce such a peak in just a few minutes... If the solvent is acetonitrile use high quality to avoid acrylonitrile as an impurity.  Avoid halide salts. PF6 is a good anion.  Really good acetonitrile is quite expensive.  Dry solvent and salts are best...  Dry salts with vacuum not high heat. Beware perchlorate salts which can be explosive under some conditions...treat them with care.. 

@Prof Kissinger

Thank you very much for the inputs. I will work on those lines. I would like to add to my previous question. In most of the papers I have come across, there are reports on CV carried out on thin films of organic semiconductors especially small molecules (ITO as working electrode). I have been unsuccessful in all my attempts since the compounds were soluble in acetonitrile/DCM/DMF and so on. Whenever I make a thin film on an ITO substrate and dip them in the electrolyte, the film would dissolve within no time. I am searching for an orthogonal solvent which falls well within the electrochemical window. Can you suggest me any such solvent wherein I could carry out analysis for thin film without the dissolution of the compound?

Hydrophobic films stay on in water, but water limits the potential range too much. I suspect you may need a polymeric film or some means of covalent attachment to the surface.  Why use ITO? You can not use an electrode such as glassy carbon?  And put the film on that or perhaps gold?

@Prof Kissinger

As I working on Solid state electronic devices wherein ITO is the working electrode. So, I have maintained the same for CV. I have tried using Glassy carbon/Pt/Au and the result is the same. As you had suggested, it boils down to the polarity of the compound 

It just might not be possible to keep your compound on the surface and do solution phase electrochemistry to study it at the same time.  Perhaps there are too many incompatible requirements?

dear colleague, I need a biological to make microbiological tests on a series of organic molecules. thank you

Hi! I have one metal complex having bromide ion in the first coordination sphere. I tried to check CV using Tetrabutylammonium bromide as supporting electrolyte in acetonitrile. But, I observed some reduction as well as some oxidation waves when I was checking the blank CV without metal complex. Can we use Tetrabutylammonium bromide as supporting electrolyte? Thanks in advance

I worry about oxidation of the bromide. A perchlorate salt can avoid that aspect. Be safe with perchlorates.