Does Caffeine Gradually Lose Its Effects In Water?
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daphniamagnaheartbeats
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Does Caffeine Gradually Lose Its Effects In Water?
My science fair project is using Daphnia Magna (water fleas) to test the effects of caffeine on heart rate. My question is can I make the solution (of spring water & caffeine) ahead of time or will the caffeine's effects wear off after being in the water for maybe a few days? I have to make 4 separate solutions for my 4 different concentrations of caffeine (mg/L). I want to make my solutions ahead of my experiments to save time because I have to repeat my experiment 3 times so having the solution ready-to-go in a container each time would be a real help. I just don't want to risk the caffeine wearing off after being in the water by the time I get to my third experiment.
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17eugenekim
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Re: Does Caffeine Gradually Lose Its Effects In Water?
Hi there!
First of all, love the username
I did some brief digging online, and the best I could find was this old thread on Reddit:
https://www.reddit.com/r/askscience/com ... e_content/
It is Reddit, so let's harness our inner science skepticism, and take a closer look.
For caffeine to lose its efficacy, caffeine has to stop being caffeine, i.e. it has to undergo a chemical process that turns it into a different chemical compound. There are two main ways (I can think of) that happens: degradation, and metabolism.
I'm no chemist, but I don't see a reason why caffeine should be a horribly unstable molecule. The only two things you really have to worry about in terms of stability and reactivity are the water solvent and light-sensitivity. As a matter of fact, checking an material data sheet for caffeine tells me that "aqueous solutions (1.12 mg/mL) are stable for three weeks at 41° F if protected from light. In normal room lighting and at room temperature, solutions are stable for 3 days. Solutions of caffeine in water [...] should be stable for 24 hours under normal lab conditions." (source: https://pubchem.ncbi.nlm.nih.gov/compou ... -Reactions)
As long as you're not putting in any acidic compounds or anything like that, the caffeine should be fine for a couple days. Keep it out of light, and it'll be good for a few weeks.
But wait! What about the other thing I mentioned - metabolism?
Caffeine is an organic (carbon-based) molecule. And because it is carbon-based, there exist living organisms that will try to break it down to use it as food. There's no good way of saying what kind of bacteria (or fungi?) are metabolizing caffeine, but it's safe to say it's going to be difficult to keep them out of your solution when making them. Even sterile technique has its limits.
So based on that, we can conclude that a) metabolism is the bigger concern, and b) you won't be able to stop it completely.
How do we minimize the damage? Let's think about it. Metabolism is essentially digestion - here, it's basically the microbial equivalent of "eating." And bacteria eat to do two things - survive, and grow. You can prevent a lot of them from surviving by employing a sterilization technique, but I would not advise that. The most likely way you're going to sterilize your caffeine solution is by irradiation, but then we're stumbling into degradation again.
But we can probably do the next best thing: prevent the bacteria from growing. This is easier: put it somewhere cold! Metabolism usually happens at a certain temperature, so cooling down the sample to a refrigerator-level temperature will probably go a long way towards slowing things down, minimizing caffeine metabolism. I tentatively say freezing it will be fine as well, though I can't be certain - freezing and thawing has the potential to do some weird things. If it were me, knowing very little about that aspect, I'd keep it in the fridge and assume that freezing would have little extra benefit. But it's your project, your call.
Conclusion: your caffeine solutions will lose some efficacy, but we can minimize the damage by a) keeping it out of light and b) keeping it in the cold. I can't say how much - the Reddit post cited a 40% decrease in 24 hours at room temperature, so hopefully less than that.
Hope that helps!
First of all, love the username
I did some brief digging online, and the best I could find was this old thread on Reddit:
https://www.reddit.com/r/askscience/com ... e_content/
It is Reddit, so let's harness our inner science skepticism, and take a closer look.
For caffeine to lose its efficacy, caffeine has to stop being caffeine, i.e. it has to undergo a chemical process that turns it into a different chemical compound. There are two main ways (I can think of) that happens: degradation, and metabolism.
I'm no chemist, but I don't see a reason why caffeine should be a horribly unstable molecule. The only two things you really have to worry about in terms of stability and reactivity are the water solvent and light-sensitivity. As a matter of fact, checking an material data sheet for caffeine tells me that "aqueous solutions (1.12 mg/mL) are stable for three weeks at 41° F if protected from light. In normal room lighting and at room temperature, solutions are stable for 3 days. Solutions of caffeine in water [...] should be stable for 24 hours under normal lab conditions." (source: https://pubchem.ncbi.nlm.nih.gov/compou ... -Reactions)
As long as you're not putting in any acidic compounds or anything like that, the caffeine should be fine for a couple days. Keep it out of light, and it'll be good for a few weeks.
But wait! What about the other thing I mentioned - metabolism?
Caffeine is an organic (carbon-based) molecule. And because it is carbon-based, there exist living organisms that will try to break it down to use it as food. There's no good way of saying what kind of bacteria (or fungi?) are metabolizing caffeine, but it's safe to say it's going to be difficult to keep them out of your solution when making them. Even sterile technique has its limits.
So based on that, we can conclude that a) metabolism is the bigger concern, and b) you won't be able to stop it completely.
How do we minimize the damage? Let's think about it. Metabolism is essentially digestion - here, it's basically the microbial equivalent of "eating." And bacteria eat to do two things - survive, and grow. You can prevent a lot of them from surviving by employing a sterilization technique, but I would not advise that. The most likely way you're going to sterilize your caffeine solution is by irradiation, but then we're stumbling into degradation again.
But we can probably do the next best thing: prevent the bacteria from growing. This is easier: put it somewhere cold! Metabolism usually happens at a certain temperature, so cooling down the sample to a refrigerator-level temperature will probably go a long way towards slowing things down, minimizing caffeine metabolism. I tentatively say freezing it will be fine as well, though I can't be certain - freezing and thawing has the potential to do some weird things. If it were me, knowing very little about that aspect, I'd keep it in the fridge and assume that freezing would have little extra benefit. But it's your project, your call.
Conclusion: your caffeine solutions will lose some efficacy, but we can minimize the damage by a) keeping it out of light and b) keeping it in the cold. I can't say how much - the Reddit post cited a 40% decrease in 24 hours at room temperature, so hopefully less than that.
Hope that helps!
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daphniamagnaheartbeats
- Posts: 2
- Joined: Sun Oct 14, 2018 12:25 pm
- Occupation: Student
Re: Does Caffeine Gradually Lose Its Effects In Water?
Thanks so much!!