Glutathione is not a good developer

[Alan Johnson]

I thought it might be better than ascorbate at regenerating phenidone as it is a stronger reducing agent in biological systems.
However, it is not (pic).
Both ascorbate and glutathione were tested in using the formula of Dr C T Blood (post 27) except that in one test the ascorbic acid was replaced by an equal weight of glutathione:. Fomapan 200 @ EI 160 was developed 7m 30s in each.
https://www.photrio.com/forum/threa...-is-as-simple-as-caffenol-et-al.119453/page-2

 

[markjwyatt]

Looks like vitamin-C is good for film too!

 

[trendland]

Well - "gluathione" isn`t a develpoer agent in any way. It is more a substance wich may work like an alternative developer substance. What " may " could mean in that special concern we can see quite clearly from your example. Thanks for this - but the question with " gluatahione " may be answered from logical considerations in general.

There are many ways to try a bw film developement with all kind of alternative stuff. I would not wonder about if " Pepsi Cola " with some heard medications inside ( in addition )
will give simular results as you have shown.

Definitifly you would need this medications in a pure form for yourself when you have to look at results from this .....!

with regards

PS : The enviromental issues of some oldschool developer agents are a serius issue. But like with many other things in live there are ways of extreme wich have to be to avoid.
Gluathione is one extreme in the oposite direction to p-phenyldiamene.
BTW - with PPD in combination with methol you will get superb results but it will cause cancer - with Gluathione you will avoid that cancer problem ( hope ) but you may result
heard problems from your experience......with pure negatives!!!!

 

[trendland]

... sorry "poor" negatives of course....

with regards

 

[pentaxuser]

There is presumably a good chemical reason why glutathione does not work very well? I wonder what it is?

pentaxuser

 

[markjwyatt]

Steric hindrance? Gluathione is a bulkier molecule with the same number of oxygen sites as the smaller, nimbler ascorbic acid. Plus the amino groups (NH) and sulfur (thione) may cause other undesirable effects.


(ignore the size differences- I just grabbed these from the web, and there is no way to adjust)

Glutathione:

ascorbic acid:

 

[Alan Johnson]

Yes, seems possible.Attempts to provide glutathione as a health supplement seem to show that in water solution it fails diffuse through the intestine wall at an adequate rate to be useful.

 

[Rudeofus]

There is every reason to believe, that Glutathione is a developer, there are at least two section which could be looked at as OH-C=N< sections. The -SH group would, on the other side, stick very strongly to silver halide grains, therefore I would not expect oxidized Glutathione to go away - this appears to be the reason why your film wasn't fully developed. Remember, how mercaptans have ridiculously low solubility products with silver unless they form a soluble complex.

I wonder whether it would work alright as primary developer, i.e. together with Ascorbate instead of Phenidone. If it works, it should be used in very small doses, otherwise fixation could become very difficult.

 

[Alan Johnson]

Glutathione could possibly transfer electrons to ascorbate and so to silver ion (fig 3) but the result would be an oxide of glutathione which you suggest would stop development.
http://www.plantphysiol.org/content/155/1/2

 

[Alan Johnson]

In theory it might be possible to regenerate glutathione with the enzyme NADPH but this costs about $10 per gram..

 

[hol571]

Interesting, have you thought about repeating this experiment with an equimolar basis of glutathione to ascorbate (requires ~1.75x more glutathione than ascorbate w/w) to see if that makes any difference?

It may not matter with developing agents, but there was a study done that the shows ascorbate reduces the free radical from the reactive metabolite of acetaminophen more rapidly than glutathione - http://www.jbc.org/content/265/2/844.long

If you're interested in going down the NADPH route, I'd suggest looking at the 2 part NADPH regenerating solutions which I've found to be more efficient vs using NAPDH alone which exhausts itself faster (although this is probably not cost effective either way)

 

[Alan Johnson]

Thanks, I note that glutathione used was not an equimolar amount to ascorbate but I don't have enough of it to re-run this.I would expect it to show some effect with the amounts actually used.
The study with acetaminophen does seem to show that just because glutathione is a stronger reducing agent it wont necessarily be a faster acting one.
When I get around to it I hope to try the developer with phenidone alone, just in case the slight development shown in strip labelled "glutathione" in the pic above is not actually caused by glutathione at all.

 

[Rudeofus]

The study with acetaminophen does seem to show that just because glutathione is a stronger reducing agent it wont necessarily be a faster acting one.

The redox potential of Glutathione is right where strong development agents are located, however, the reaction behind this redox potential is the 2* G-SH <===> GS-SG + 2* H, which may not take place due to formation of G-S-Ag type salts. The redox potential coming from the various HO-C=N< groups may be much weaker, and a much higher pH may be needed to deprotonize their -OH groups in quantity.

 

[Raghu Kuvempunagar]

@Alan Johnson: Glutathione might not be a good developer but your negatives from Dr. Blood look good. Have you printed any Dr. Blood negatives and in your opinion how would you rate Dr. Blood in comparison to XTol?

 

[Alan Johnson]

Here's what Dr Cyril T Blood says about his developer, from BJP Nov 10 1999:
"...ascorbic acid developer... the first such formulation for modern films to be made public........compared with..other developers this one shows more sensitivity and better rendering of contrast in the low exposure (shadow) region, and the highlight region does not shoulder off too seriously.. well matched to modern B&W films especially those of of a slower speed rating... it is ..possible to increase practical exposure indices considerably, for example with Delta Pro 100 up to EI 250-320 whilst retaining easily printable shadow density."
He does not mention grain , I measured pH working solution ~10 , or keeping properties.

 

[Alan Johnson]

2 more tests:
(1) Dr Blood developer using glutathione not ascorbate with added 5g/L sodium sulfite to working solution, same film & development time as before - result - similar to the strip labelled "glutathione" in the pic above.
(2) Developer as in (1) with added 10g/L sodium hydroxide to working solution, ph ~ 13-14, result as (1) above, faint image.
Conclusion - When silver ion is reduced, a phenidone free radical is formed and , unlike the case with ascorbic acid, it does not react with glutathione but goes to "phenidone oxide".which is inert.