[Maisinxy]

Im currently in a chemistry 12 class and I have to make a chemistry lab all by myself and so, I though I would do something with glow in the dark solutions.

I did some research and I found that luminol and hydrogen peroxide when combined would create the glow in the dark liquid, but Im having trouble actually getting it to glow.

Before we started the labs, maybe a week before I made my luminol solution, I added 0.2g solid luminol, 115ml water and 10ml NaOH to make it basic. I left this in a container in the fume hood for a week prior to doing the lab because my teacher told me to put it there.

On Thursday when i had my lab, i mixed together a 1M solution of CuSO4 to catalyze, 10mL Hydrogen peroxide and the luminol solution but for some reason it turned brownish yellow?

I also heard that it was carbonating too, i heard bubble fizzing like in a pop drink.

I tried it again, but I didnt add the CuSO4 and the luminol + Hydrogen peroxide made a clear solution which didnt glow. Im guessing the issue is that i shouldnt have premade the luminol solution and maybe it turned weird after leaving it for a week? I cant figure out any other issues.

I have to finish this lab by November 21st so if you have any ideas of what the issue might be please let me know.

[Borek]

I added 0.2g solid luminol, 115ml water and 10ml NaOH to make it basic

10 mL NaOH doesn't tell us anything about the amount of NaOH present (was it 1M NaOH solution, or 0.01 M solution?) and this is a crucial information, as it can mean several unit differences in the final pH.

(same about other parts of your text, 10 mL hydrogen peroxide is just half of the information needed, just like 1M CuSO₄)

Perhaps our organikers will have something to add, but bonds in hydrazides (luminol is a hydrazide) are similar to those present in amides and look susceptible to hydrolysis in high/low pH. So yes, could be leaving the solution for a week was not a good idea. If anything, I wouldn't add NaOH.

[Babcock_Hall]

There is a 2007 review article by Barni and coworkers on luminol.  They give the Weber formulation of this reagent as follows:

"Prepare 0.5 L of 0.4 M NaOH (8 grams NaOH).  Stock solution A.
Add 10 mL of 30% H2O2 to 490 mL water.  Stock solution B.
Dissolve 0.354 g luminol in 62.5 mL of 0.4 M NaOH, and dilute to a final volume of 500 mL.  Stock solution C (final concentration is 4 mM).
Store solutions A, B, and C at 4°C away from direct light.
Mix 10 mL of each stock with 70 mL of water to obtain 100 mL of working solution.  Decant solution into a vaporizer or sprayer and use immediately as an aerosol.  Wear goggles, gloves, and protective clothing.  Use a respirator, and keep the number of people to a minimum.  Apply in the dark.  Aerate the room after investigation."

Obviously, this could be scaled up or down as needed.  I will try to add some further comments, probably about copper ion as a catalyst, when I am a little less pressed for time.

[Babcock_Hall]

https://www.bluestar-forensic.com/wp-content/uploads/2020/09/false_positives_2008_study.pdf
There was a 2008 study of false positives involving BluStar^R, a commercial formulation of luminol.  They used a stock solution 0.1 M CuSO₄, but I am not sure how they performed the experiment (such as the volume used).  They noted:

All the solid chemicals were first dissolved into distilled water at a 0.1 mol/L concentration. Liquid chemicals
were diluted to obtain this same concentration.
MnSO4 (Manganese sulfate): bright, short-lasting white chemiluminescence; build-up of a brown precipitate.
CuSO4 (Copper sulfate): non-lasting blue chemiluminescence; build-up of a brown precipitate.
FeSO4 (Iron sulfate): non-lasting blue chemiluminescence; build-up of a brown precipitate.
MgSO4 (Magnesium sulfate): no reaction.

So the brown color sounds normal, but I think decreasing the concentration of the metal ion couldn't hurt.

[Babcock_Hall]

It is possible that the fizzing sound was from nitrogen gas being released, but I am far from certain.  The 2007 review article I mentioned appeared in the journal Talanta:  PMID: 19071703  DOI: 10.1016/j.talanta.2006.12.045. 

[Maisinxy]

I see! I've also been told by others that leaving the luminol out in the fume hood in a container was the issue as the luminol decomposes in light. Thank you your insights.

Just to clear up some uncertainties, here are some of volumes and molarities I used:
10mL NaOH (1M)
0.2g Luminol
115ml Water
10mL H2O2 (3%)
0.25mL CuSO4 (1M)

I just wanted to clarify, by combining the NaOH and the luminol solution (hydrazide) it caused hydrolysis due to becoming basic and thus the solution became bad?

And for the future, should I just mix the Luminol solution and the H2O2 and then the catalyst at the moment of the experiment?

I was actually planning on changing the concentration of the H2O2 and determining the effect it has on the intensity of the reaction. I was going to do 10 different concentrations for 5 trials each, would this mean I should prepare the luminol solution for each trial at the moment of doing it?

[Borek]

I just wanted to clarify, by combining the NaOH and the luminol solution (hydrazide) it caused hydrolysis due to becoming basic and thus the solution became bad?

It is not like I am 100% sure, but just looking at the bonds present that's a possibility.

And for the future, should I just mix the Luminol solution and the H2O2 and then the catalyst at the moment of the experiment?

That would be probably better that keeping the solution for a week. Or at least dissolve luminol, but don't add the base.

I was actually planning on changing the concentration of the H2O2 and determining the effect it has on the intensity of the reaction. I was going to do 10 different concentrations for 5 trials each, would this mean I should prepare the luminol solution for each trial at the moment of doing it?

I wouldn't care if the solution is used in one sitting (especially if you can keep it in a dark glass bottle), it is probably the week that matters, not few hours.

[Babcock_Hall]

What follows (from Barni F et al. 2007) is the recipe for the Weber formulation of luminol.

Weigh out 8 g of sodium hydroxide and completely dissolve them in 0.5 L of deionized water to obtain a 0.4 N solution (stock solution A).

Measure 10 mL of 30 % hydrogen peroxide and add them to 0.49 L of deionized water to obtain a 0.176 M solution (stock solution B).

Weigh out 0.354 g of luminol and completely dissolve them in 0.0625 L of 0.4 N sodium hydroxide solution to obtain a final volume of 0.5 L (0.004 M) (stock solution C).

Store the three stock solution in glass or plastic containers at 4° C, away from direct light.

Prepare the test solution by mixing 0,01 L of each of the three stock solutions to 0.07 L. of deionized water to obtain 0.1 L. of final working solution.

Decant solution into a vaporizer or sprayer and use immediately.


Tobe SS et al., J. Forensic Sci. 2007 Jan;52(1):102-9.  doi: 10.1111/j.1556-4029.2006.00324.x.
Regarding how to perform a test, I found a discussion that might be helpful.
"The six different [color-change] reagents were tested against saliva, semen, potato, tomato, tomato sauce, tomato sauce with meat, red onion, red kidney bean, horseradish, 0.1 M ascorbic acid, 5% bleach, 10% cupric sulfate, 10% ferric sulfate, and 10% nickel chloride.  For each of the presumptive reagents tested, a large piece of filter paper (approximately 100 cm²) was exposed to each of the substances being tested in 25 separate sample stains. These were allowed to dry for a minimum of 18 h. Each of the pieces of filter paper, and subsequent stains, were then tested with their corresponding reagent to see whether the substance caused a reaction."

[Maisinxy]

I see, just one last question. Would the same apply for the Copper Sulfate mixture? Should I also create that mixture right before the lab or is it okay to keep in a transparent bottle in the fume hood?

I added 2.4g of CuSO4 with 15mL water to make a 1M solution. I will be using this 15mL for the entire lab, I am using 0.25mL CuSO4 for each trial (5 trials per increment, 10 increments)

[Hunter2]

Copper sulfate solution is no problem to make up in advance. Its stable.

[Maisinxy]

UPDATE:

I tried the lab again today with the new tips I received.

I added 0.02g of luminol into 4mL water and stirred it until it was dissolved.
I then added 5mL of 3% and 9% peroxide (I tried it twice with each concentration respectively)
after adding the peroxide, I added 0.25mL CuSO4 and stirred more.

This time, the mixture didnt turn brown, it was a translucent yellowish colour, thoug hti still did not glow or turn into the light blue.

As I said, I tried it twice, changing the concentration from 3% to 9% though both times it didnt glow. Im currently trying to troubleshoot the issue, though I cannot find anything wrong with my procedure.

I may try again tomorrow by adding 1g baking soda (sodium bicarbonate) into the luminol as I have watched some videos, specifically from Nile Red in which he added sodium bicarbonate.

If anyone knows the reason why it still is not glowing please let me know!

[Babcock_Hall]

My reading of the Weber formulation, which has been used for many years, is that a portion of sodium hydroxide is used to make stock solution A, and the rest is added later as stock solution C.  Let me focus on one aspect right now and possibly come back to other possible issues later.  I would spray a piece of filter paper with the CuSO₄ solution and let it dry overnight as noted in a previous comment.  I would spray the luminol solution onto this paper in the dark.
EDT
Corribus raised a good point regarding the age of the hydrogen peroxide.  It decomposes over time.

[Corribus]

Are you sure your peroxide is good? You are buying commercial 3% and 9% solutions? How old are they?

[Maisinxy]

I bought my peroxide around 3 weeks ago brand new.

A few days ago I actually took a glow stick and I took out the glass vial  from the stick which should've included the  dye and oxalate ester. I mixed my peroxide with the liquid in the glass vial and it started to glow, so i feel like the peroxide is okay.