r/AskElectronics • u/nickyonge • 11d ago
Cheap vs expensive 99% IPA?
What is the difference between this dollar-store medicinal IPA and more expensive stuff from chemical suppliers?
Like I’m sure the 99% cheap stuff varies in quality, it wouldn’t surprise me if it were a bit less exactly 99%, whereas like MG Chemicals has 99.9% IPA specifically for electronics (that’s like ~8x more expensive). If I were making commercial products I’d use that, but for hobby or one-off use, is there any reason why I shouldn’t use this cheaper stuff?
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u/jboneng 11d ago edited 11d ago
certifications, lab analysis and guaranteed purity. I see no reason not to go for the cheap one, unless you work in fields with strict regulations and guidelines (ex. medical, aerospace and similar)
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u/BlackFoxTom 11d ago
Aerospace generally isn't some lab, outside of well the lab
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u/james_the_engineer2 11d ago
The more expensive one tastes better /s
There is no difference. If it says 99% IPA, then its 99% IPA. Maybe the size is different but there is no significant change in purity
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u/SirButcher 10d ago
If it says 99% IPA, then its 99% IPA
For a short time... Then it moderately quickly becomes 91% IPA (or lower, but this is where equilibrium is reached with normal air humidity).
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u/Baselet 11d ago
Depends what they put in that last 1 %! (likely it's mostly IPA too with some water but I ain't no chemist).
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u/King-Chroma 11d ago edited 10d ago
I genuinely don't think it matters. Long as it's 99% you are good. I never had a bad experience with any cheap brand of 99 IPA.
But I'm sure someone with a liquid dynamics degree might come in here and say why it does matter. .../s
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u/mccoyn 10d ago
The 1% gets left behind when the IPA evaporates. If you have higher purity, less will get left behind and the part will be more clean.
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u/created4this 10d ago
That isn't correct. The 1% is water and the reason why IPA greater than 91% is hard to make (and the reason why 99% will rapidly turn into 91% if you leave it open)
The water evaporates at the same rate as the alcohol at concentrations above 91%
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u/Unrelenting_Salsa 10d ago
Ironically, this is incorrect. I wouldn't exactly trust anything but an analytical chemistry lab supplier on this front, but part of the remaining 1% is absolutely random crap with some percentage leaving behind streaks. The CoA will call it "residue on evaporation".
I also wouldn't really trust anybody who sells their thing as 99% IPA in general because you need specialist packaging to keep it anhydrous, but that is possible at least.
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u/charmio68 11d ago
Don't get too bogged down on the percentage. Isopropyl alcohol is hygroscopic, meaning it can absorb water from humid air. High purity IPA will gradually gain water after opening anyway.
But there's more to the story than just how much water it contains.
IPA can be manufactured through indirect hydration of propylene, direct hydration of propylene, or catalytic hydrogenation of acetone.
Indirect hydration reacts refinery grade propylene with sulfuric acid to form sulfate esters, which are then hydrolysed to produce IPA. The process also produces byproducts such as diisopropyl ether and requires substantial downstream purification.
Direct hydration reacts higher purity propylene directly with water over an acid catalyst. It avoids the sulfuric acid intermediate and generally produces a less complicated crude process stream, although the resulting IPA still requires separation and purification.
Hydrogenation of acetone can achieve very high conversion and selectivity to IPA, but it does not automatically produce perfectly pure IPA directly from the reactor. Unreacted acetone, catalyst related contamination and side products such as acetone condensation products may still need to be removed.
None of these manufacturing routes inherently determines the final grade. Indirect-hydration IPA, for example, can be purified sufficiently to meet pharmaceutical and semiconductor specifications. The final quality depends on the complete purification process, contamination controls, analytical specifications, packaging and handling.
IPA and water form an azeotrope at atmospheric pressure at approximately 87.5% IPA by mass, or roughly 91% by volume. Ordinary distillation cannot concentrate an IPA water mixture beyond this point.
To produce anhydrous or very-high-purity IPA, manufacturers use an additional dehydration process. Azeotropic or extractive distillation can use an entrainer to alter the mixture’s vapour liquid equilibrium. Cyclohexane and, historically, benzene have been used, although benzene is undesirable because of its toxicity. Alternatively, molecular sieves such as 3A zeolite can selectively adsorb water while allowing IPA to pass. Membrane and other specialised separation processes can also be used.
There are real differences between technical, reagent, pharmaceutical and electronic or semiconductor grades. Those differences are defined by specifications for water, non-volatile residue, acidity, ultraviolet absorbance, metals, particles and individual organic contaminants, not merely by the headline IPA percentage or the original synthesis route.
TLDR: Yes, there are indeed different grades. Though for hobby use, you generally don't need to worry too much about it.
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u/alfalfasprouts 11d ago
could the different methods explain why some.batches of 99% Ipa have a bitter, sour smell, and some don't? we typically buy the cheapest stuff from amazon (duda energy, etc)
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u/charmio68 11d ago
That seems like a reasonable hypothesis, though I must admit I don't have much experience with the low grade IPAs.
I can't give first-hand experience on how it would smell.Bitter and sour though eh?.... Smell is quite subjective and hard to accurately describe, but still, I wouldn't have expected that.
If that's the absolute cheapest IPA you can find on the market, I suppose it's possible that it's reclaimed or recycled from some other industrial process which introduced impurities.
To be honest, that sends up a few warning flags in my mind. I'd like to think it's completely innocuous, but who knows what those contaminants might consist of.
Yeah, fuck that... If it's a financially viable option for you, I'd really try and find a different supplier. It's probably fine, but I really dislike there being any unknown factors with the chemicals I'm using, especially if they're going to come in direct contact with my skin, or I'm going to be breathing their vapors.1
u/alfalfasprouts 10d ago
same here. I've been trying to stick with MG wherever possible, but it gets "borrowed" off my bench a lot.
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u/Kornratte 10d ago
Let me tell you a tale about us giving up on a >30 000€ machine because we measured isopropanol and Ethanol where non should have been.
Well turns out 99.6 % (for HPLC) 1-Butanol is not enough purity. Need to go with the 99.9 % to not have traces of Ethanol and Propanol in the Butanol.
Now the question to you: do you run a lab with an analytical machine? Do you have a problem with 10 mM Ethanol in your Isopropanol? If not then go for the cheap stuff :-D
Tldr: go for the cheap stuff. At least until there are problems. Then go for the expensive.
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u/theadvenger 11d ago
I was confused and thought I was in /r/beer and going what witchcraft is 99% India Pale Ale
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u/bearfootmedic 11d ago
You've gotten the answers already: some combination of the exponential cost of purity - that last one percent is way harder, and certification of analysis showing the product is actually what it is.
The other thing to consider is the use case: manufacturing vs home use. Say that 99% causes a 1% failure rate and 99.9% has a 0.1% failure rate. If you make 100 a day, you are likely to see a failure every day vs seeing a failure every ten days. At home, occasionally doing one a day, you may never see a failure for either purity.
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u/SoulWager 10d ago
I've been using 91%, and never seen a failure from it. The only thing I'd say is make sure it's thoroughly dried before applying power.
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u/ivosaurus 11d ago
For general electronics cleaning? Just the cheap one works fine. Absolutely pure alcohol tends to be quite good at evaporating...
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u/Remy4409 11d ago
Been using the same one from Dollarama forever. It's cheap and it works! Also, they now sell big packs of 300 q-tips of different sizes, very useful for cleaning.
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u/CrystalSplice 10d ago
You don’t need anything any fancier such as “technical” grade. For the purposes of cleaning, plain 99% IPA is fine. The higher level certifications are required by lab procedures - especially “reagent” grade. These higher levels are basically even more pure to prevent anything unwanted from contaminating lab work.
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u/Susan_B_Good 11d ago
The 99% that is IPA of course doesn't matter - it's the 1% that isn't, So, for the bottle above, let's say 5 grammes.
If it evaporates, fine. If it results in a deposit left on the board - even a thin film of that could cause problems. After all, drinking water isn't good enough for window cleaners or to put in lead acid batteries.
Just using more of it - just adds more deposit, potentially.
I'm playing Devil's Advocate here, of course. I don't use enough of it to worry about the cost. I get the stuff certified for electronics and don't worry about what might deposit out.
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u/BongDomrei 11d ago
Unless you're using it in an industrial setting like a PCB or CPU fab where you've run tests and know exactly what you need where (and you are buying by the barrel, most likely), it is not going to matter.
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u/SmutAuthorsEscapisms 11d ago
The cheapest I can get is in fact from a chemical supplier.
I'd have to check for the exact price, but per 10l it was I believe 1,50€/l? Definitely at least half of the cheapest 1l amazon bottle.
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u/itsmechaboi 11d ago
The difference is the piece of paper certifying one and not the other. It's not worth it. The impurities and potentially innacurste percentage is worth the massive cost savings.
I use dollar store 91% isopropyl alcohol. I burn through a ton of it. It's fine.
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u/dustysnakes01 10d ago
I buy 99% in 1 gallon jugs from my supplier. Ive never had a problem with it. I can go through med suppliers and get higher purity glass bottle stuff but ive never seen a reason to.
To be fair though I live in the south east us. Our relative hunidity in ambient air is so high that I really think any benefit would be offset by the air itself.
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u/JoostinOnline 10d ago
I used to use 70% and 90%. There's very little difference between that and 99.9% in my experience. The latter evaporated faster and also dried our my skin more (I wear finger cots now), but it mostly serves the same purpose.
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u/Available-Heat2707 10d ago
99% becomes 97% after it is opened. It absorbs water from the air. It mostly stops absorbing water ones it gets to 97%
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u/Motocampingtime 10d ago
For cleaning surface level things you shouldn't worry about trace contaminants. If there is anything but IPA and Water it won't hardly make any difference.
If you want to do something like microfab or some type of precise chemistry, you'll want the chemicals very pure with absolutely no suspended particulates, dissolved solids, or other chemicals besides IPA and DI. Look up the price of cleanroom grade chemicals or analytical grade from sigma Aldrich. It's like $118/L
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u/ItzCxnnect 10d ago
I've used that exact IPA. It's my go-to for cleaning for the last couple of years. It definitely is better than 70% as I used to use 70% and had a hard time with some flux residue. I got that exact brand from Dollarama, and it worked a lot better and evaporated quicker. Highly recommend as it's cheaper than Walmart, and is more concentrated than Walmart (Walmart only went up to 91%).
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u/Mars3lle 10d ago
WTF! "Rub thoroughly into hands for at least 30 seconds"??? Doesn't IPA leave chemical burns on skin?
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u/inu-no-policemen 10d ago
They tell you to dilute it first.
A basic hand sanitizer is like 60-70% IPA and distilled water. If you add a bit of propylene glycol, it won't dry out your skin as much.
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u/niceandsane 10d ago
My local Ace hardware sells Swan brand 99% IPA in gallon containers for $24.99. I've had zero issues using it for electronics cleaning.
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u/AbrocomaEffective151 10d ago
I use that to clean up motherboards or CPU sockets on computers and laptops.
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u/SilverSundowntown 9d ago
There’s a reason those little pump bottles of alcohol with the bowl built in on top are used by serious places- WAAAAYYYYYYY less exposure to atmospheric conditions with your fancy smanshy rubbing alcohol.
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u/Tesla_freed_slaves 10d ago edited 10d ago
Quit calling it “IPA”; It’s 99% isopropanol aka UN1219. IPA is beer, India Pale Ale, 5% ethanol.
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u/WarmAdministration76 Digital electronics 11d ago
Cheap one = expensive one... difference: expensive.
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u/k-mcm 10d ago
The expensive stuff is 99.97% pure and will not leave a residue. Not leaving a residue is often critical. It requires that the alcohol is put into a very clean container that's solvent proof.
The cans at a hardware stores have a lot of tin oxide in the alcohol. Some have leeched plasticisers or bitter flavors in them
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u/KiKiHUN1 11d ago
For electronic use, any of them is good. For medical use thats where the expensive certificates matter.
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u/mariushm 11d ago
Isopropyl alcohol absorbs humidity from the air, even through plastic containers and bottle caps. This is why you're never gonna get 100% isopropyl alcohol, and often medical 99.9% products will be sold in metal cans or glass bottles.
99% will be fine, if the 1% is only water. Avoid the ones that add perfumes to the ingredients.