mericad193724
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Sensitive H2O2 assay
Hello,
I know there is a lot of information out there on hydrogen peroxide decomposition, but I need a really sensitive way of determining is there is any
H2O2. I am using a Dissolved Oxygen sensor which acts abnormally when there is a trace of hydrogen peroxide (it reads it as oxygen).
What is the best way to determine if there is hydrogen peroxide?
Adding Ferrous Sulfate and observe for a dark color?
Adding Manganese Chloride and observing for black precipitate?
Something else that is very sensitive?
Thanks,
Mericad
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UnintentionalChaos
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This one is a little out there, but if you were to take indigo dye and reduce it to leucoindigo, which is soluble and clear, a dropper of the solution
(which is incredibly sensetive to oxidation, so much that the surface of the reduced solution will have blue scum floating on it from atmospheric
oxidation) added to the mixture in question with as little mixing and air exposure as possible should precipitate a good deal of opaque, dark blue
solid. I have never tried this before, but I imagine that oversensetivity may even be an issue. Theoretically, it could be used to provide a vague,
but nonetheless quantitative measurement of peroxide content, of course being skewed by atmosphereic oxidation, oxidation by dissolved oxygen not from
the peroxide, and oxidation induced during decanting of the solution still containing some reduced indigo. I am not sure just how fine the ppt would
be, so merely isolating it for weighing might be an issue.
[Edited on 4-8-07 by UnintentionalChaos]
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'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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12AX7
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If you need it at the same time as the oxygen, I wonder if a complex might be useful.
I've noticed titanium forms a strong, stable red complex with peroxide. Incidentially, it'll also sequester the peroxide (for the most part). Of
course, you need titanium in the first place, which in aqueous solution means enough acid to keep it that way.
Tim
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Alchemist
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H2O2 lifespan
Hello all,
Did not really no where to put this, so I hope someone replies.
What is the typical lifespan of 30% Hydrogen Peroxide?
I get mine from various sources, pool supply, hydroponics, etc.. I get it in the gallon size because it cost a lot less this way if it would last that
is. I keep it in the fridge (NOT the freezer), and still it only lasts for 4 mo. to 5 mo.. After that it's just pretty much water or VERY weak H2O2!
Any idea's on keeping it longer.
Thanks the Alchemist.....
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UnintentionalChaos
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If you have a spectrophotometer, an excess of guiacol and some peroxidase (easy to extract a crude form from turnips), you can do a extremely
sensitive test for H2O2. I would suggest having a micropipettor or a nice graduated pipette and some fairly large volumetric flasks as well in order
to accurately prepare a highly diluted solution for the test. To get an idea, the test solution we used in lab was 0.0046% H2O2 and attained a
medium-dark beer tone from formation of tetraguiacol oxidation product. The idea here is that if you dilute a high strength or low strength (or
unknown strength) product to 500 or 1,000 times its original volume, the test will still be very sensitive
[Edited on 9-13-08 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Picric-A
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@Alchemist - Is you peroxide stabilised? eg, most peroxide you can buy from a pharmacy contains a small amount of phosphoric acid, this works wonders.
Other than that you are storing it well, Just as long as you keep it cool and out of direct sunlight it shold be good for a few years,
No matter how well you store it though concentrations of around 30% will decompose slowly its just a atter of slowing that decomposition.
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UnintentionalChaos
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It is possible that if you are buying very cheap H2O2, you may be getting crude material with poor or no stabilization and transition metal
contaminants. I believe I got an extremely small amount of copper in what was a stable bottle (only 300ml left) of 15% and pressure started building
up from decomposition, requiring me to crack the seal every week or so. I ended up using it all for a rather impressive burning splint in oxygen
display rather than continue to deal with it.
I have very little pressure buildup from my 35% food grade H2O2, which I believe has a higher than normal phosphoric acid content and has extremely
low metal contamination.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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