Dear Meysam,

The following reagents might be used to stop the Fenton's reaction:

1- An excess of thiosulphate.

2- DTPA which is  much better than EDTA.

3- Deferoxamine which is strong iron specific chelator

4- Catalase

5- methanol or ethanol is an efficient agent for scavenging hydroxyl radicals in the Fenton's process.

Good luck,

Rafik

Dear Meysam,

The following reagents might be used to stop the Fenton's reaction:

1- An excess of thiosulphate.

2- DTPA which is  much better than EDTA.

3- Deferoxamine which is strong iron specific chelator

4- Catalase

5- methanol or ethanol is an efficient agent for scavenging hydroxyl radicals in the Fenton's process.

Good luck,

Rafik

Dear Rafik

Thank you for your useful answer. My question is about the effect of TCA on Fenton reaction and different end-products which has produced on produced by Fenton products.

Thank You Again,

Meysam 

Dear Rafik

Thank you for your useful answer. My question is about the effect of TCA on Fenton reaction and different end-products which has produced by Fenton system.

Thank You Again,

Meysam 

Dear Meysam,

No effect because you neutralize it with the added buffer.

Rafik

Dear Rafik

I mean I added 10% TCA to the mixture of protein+fenton system and then centrifuged it. subsequently, removed supernatant and repeated TCA adding two more times and finally dissolved into phosphate buffer. 

Meysam

Dear Meysam,

I agree with Rafik's answer. to my opinion desferrioxamine would be the best chelatant for iron. As for addition of alcohols, usually the best is t-butanol because the resulting free radical does not react or reacts much slower than metanol or ethanol radicals. However all alcohols might change the conformation of proteins.

CHL

Dear Chantal

Thank you for your answer.

Meysam

I'm going to use sodium thiosulfate for stopping this reaction. how much sodium thiosulfate should I use?

Thank You  

It is impossible to inhibit the Fenton reaction - the decomposition of hydrogen peroxide to hydroxyl radicals because these radicals very reactive and live a very short time, about one millisecond. Especially no need to use TCA which is a strong acid and no antioxidant.

Professor Igor Afanas'ev 

Dear Igor

thank you for your reply. As we should expose the samples treating with Fenton reaction for 30 minutes we should stop this reaction, somehow because this reaction is time dependent and during time more amount of H2O2 will be decomposed to OH radical and finally higher oxidations would be happened.

Thank you

I suggest EGTA 10 mM final concentration!

I suggest the use of either organic cheating agents such as EDTA or EGTA or inorganic cheating agents such as sodium pyro phosphate at 10mM final concentration as suggested by Lucia Marcocci

Dear Abdelrahman,

Look at old works (Profs.Chapzki, Bielski, Wintreburn, and others) which demonstrate that EDTA accelerate hydroxyl radicals formation by the decomposition oh hydrogen peroxide. It was a reason why at the beginning everybody believed by mistake that hydroxyl radicals were formed in in vitro systems in the presence of EDTA.

Professor Igor Afanas'ev

Thank you professor Igor Afanas'ev

prof A Hunaiti

thank you for all of your suggestions

Meysam

Egta, edta, or dtpa are do not stop the Fenton reaction, as Prof. Afanas'ev pointed out, see also our 1987 paper.  It is also not clear that at neutral pH hydroxyl radicals are formed.  Desferrioxamine, as suggested by Dr. Karaman, will stop the reaction, as explained in the 2nd attachment.  Addition of TCA will not necessarily stop the Fenton reaction.  I do not know the kinetics of binding of iron to desferrioxamine, and therefore it would be best to add t-butanol (Prof. Houée-Levin, see above) and desferrioxamine at the same time. 

Good luck!

Dear Willem

Thank you for your valuable suggestion.

Meysam

Dear Prof. Willem Koppenol,

Is it only ionic iron (i.e. Fe3+ and Fe2+) responsible for Fenton reaction or other di/multivalent metals (such as copper - Cu2+ & Cu+, Cobalt , nickel, manganese etc.) can also promote Fenton reaction? Few researchers showed that di/multivalent metals also promote Fenton reaction.

Dear Dr Pardha-Saradhi

In principle, all reduced metal ions can be involved in Fenton activity, it depends on the electrode potential of the Mn+/Mn+1 couple.  In vivo, only Cu(I) may be involved.  Interestingly, edta inhibits the redox activity of Cu.

Dear Dr. Farsani

From my experience, the best chelator to stop a Fenton-type reaction is DETAPAC (diethylenetriaminepentaacetic acid). In contrast to EDTA it catches everything.  mM should be enough; but much helps a lot.

Best

Leopold Flohé

Dear Prof. Willecan Koppenol,,

Thanks a lot for clearing my doubt. Can you please send me few of your and/or some other good papers or references where in it has been demonstrated that other multivalent metal ions promote Fenton reaction (so that we can cite).

Dear Leopold,

Detapac (dtpa) does not stop the Fenton reaction: we measured a rate constant of 0.51 x 103 M-1s-1, J. Inorg.Biochem. 29, 199-215 (1987); a similar value had been reported by H. C. Sutton and C. Winterbourn, Arch. Biochem.Biophys. 235, 106-115 (1984). 

Dear Dr. Pardha-Saradhi,

I attach a review; unfortunately, it cannot be printed.

Dear Willem,

Thanks a lot for your informative review and the critical remark on my earlier comment on chelators and ‘Fenton-type’ reactions. I was not aware of Christin’s and your work on this issue. My comment, as I said, was not based on clean experimentation, but on ‘experience’. Some decades ago, I had been working at industrial scale on the refolding of a recombinant protein obtained from E. coli as ‘inclusion bodies’. We actually managed to re-nature the protein that contained 12 disulfide bridges to optimum activity at near 100% yield and verified the correct position of disulfide bridges by tryptic fragmentation of the re-natured product. After the process had run smoothly for several month, all of a sudden the yields went down to zero repeatedly we first could not find any explanation for the disaster, since at lab scale, using clean glass equipment, everything went as perfect as before and doing “experiments” at an 8000 l scale was simply too expensive, even for industrial researchers. We had to rely on best guesses. When checking the large-scale equipment, we discovered a tiny corrosion in the stainless steel cover of the refolding vessel. My guess was that the two-electron oxidation of the protein thiols in the regular process had switched to a free radical chain reaction initiated by transition metal-catalyzed thiol oxidation that lead to unspecific cross-linking. That is what I considered ‘Fenton-type’. To be honest, I do not have any precise knowledge what happened in the regular refolding process and in the ruined one, nor do I have any precise data on the steel impurity that caused the corrosion and obviously ruined the process. But, after some trial and error, we completely solved the problem by making the whole 8000 l vessel 1mM in DETAPAC (later on the whole procedure was run in plastics to be on the safe side). After reading your review again, I am still convinced that the disaster we experienced had something to do with radical formation during the thiol autoxidation and that the cure of the disaster by DATAPAC points to scavenging of transition metals and blocking a transition metal-catalyzed step. This interference of DETAPAC with transition metal catalyzed thiol oxidation does not necessarily affect the “Fenton step”, but it works. Perhaps you can help me to solve this old puzzle.

Best regards

Leopold

PS: Don't ask me for a publication. the material is hidden in the archives of the company.

Dear Leopold,

I agree; in your case there was redox-cycling and dtpa may have prevented the reduction of Fe(III). 

Best wishes,

Wim

Dear Prof. Willecan Koppenol,,

Thanks a lot for an excellent review. It is very educative. This would be extremely useful for both my teaching & research.

Hi,

you can use the methanol alcohol, it's best scavenger of OH° radicals.

This is serious, I never know that methanol and ethanol can work as scavenger for fenton reagent. I have been working on a compound dat has very slightly solubility in water (PRIMIDONE).On the cost of it I choose to dissolv first with ethanol and then make up to mark with dist. water then subject to photo fenton reaction. But the result is not necessary agreement with literature. Which solvent do I use? I don't know if acetic acid is ok since it is resistant to attack by fenton reagent.?

Rate constants for the hydroxyl radical can be found at http://kinetics.nist.gov/kinetics/index.jsp.

Good question and good discussions ..

Hi you might find the data below useful. The mechanism of how the quencher works is that the quenchers will react rapidly with the residual peroxide. This effectively stops the Fenton's process. 3 commonly used quencher were evaluated for cost, performance and also COD contribution. Sodium sulfite, bovin liver and also sodium thiosulphate was tested. Sodium sulfite was shown to be the most cost effective and efficient in quenching residual peroxide. You may refer below for the quantity of quencher needed as well. Hope this helps. cheers. :D

Experiment Findings Residual Peroxide from Fenton process and a study to evaluat...

You may also try a good iron chelator.DETAPAC is the best one.

https://www.researchgate.net/post/Which_reagent_can_be_used_for_quenching_of_fenton_and_fenton-like_reactions