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 on: Today at 06:10:02 AM 
Started by pavlosmelas - Last post by pavlosmelas

As an assignment I need to explain all fragments with high intensity, the molecule is 2,8-decadiyne (see structure made with chemdraw).

The MS spectrum:

The molecular ion is 134 m/z, the fragments with 133, 119, 67, 53 and 39 m/z I figured out already but I just can not figure out the fragments at 106, 105, 91, 79, 77, 41 and 27 m/z. Especially the base peak of 91 m/z does not make sense for me, I am new at analytical chemistry and my teacher told me that if you see 91 m/z you should think first about tropylium cation but I think this is not possible since this is no aromatic molecule but a diyne.

I hope someone can help, thank you very much.

 on: Today at 04:10:42 AM 
Started by Traumatic Acid - Last post by Babcock_Hall
Your answer may or may not be correct, but your method is suspect.  In a peptide most of the carboxylate groups and amino groups no longer exist in that form, being part of amide bonds (more specifically, peptide bonds).

 on: Today at 04:08:38 AM 
Started by Schattenmaler - Last post by Babcock_Hall
Are you certain that you cannot use some sort of coupled enzyme assay that involves bicarbonate as a reactant?  Many coupled enzyme assays are known, and adapting one of them might save you time.  Alternatively (and as implied by wildfyr), some enzymes that release or consume protons can be assayed via a pH-stat.

 on: Today at 03:59:33 AM 
Started by nhoratiu - Last post by wildfyr
A Tide pen and patience.

 on: Today at 03:57:36 AM 
Started by Schattenmaler - Last post by wildfyr
It occurs to me that youre probably already in a buffer. You should do the calibration curve in the buffer solution. I am a little worried that the pH changes my be small and difficult to measure.

 on: Today at 03:41:58 AM 
Started by Herbie72 - Last post by Herbie72
We are developing a product which will be made with polypropylene injection molding in the future.
But before we make an expensive mold for injection molding, we want to make some prototypes.
Making a mold for casting is a lot easier for us than making a mold for injection molding.

 on: Today at 03:09:51 AM 
Started by Schattenmaler - Last post by wildfyr
If carbonate is being released, there should be a pH change. Use a pH indicator that undergoes color changes around the pH of interest and a UV-Vis. You will probably need to make carbonate stock solutions with the indicator and establish the absorbance curve yourself, since pH indicator color shifts are not just simple increasing absorbance with concentration curves. They tend to look like

If you poke around, perhaps you can find another metal salt that will work if calcium is having a problem (binds to enzyme?)

 on: Today at 03:06:53 AM 
Started by nhoratiu - Last post by Corribus
I mean, you can use bleach but as Arckon pointed out, it's going to be difficult to avoid bleaching the parts that are supposed to be blue unless you use a localized application of it.

 on: Today at 03:02:31 AM 
Started by Herbie72 - Last post by Corribus
What kind of casting? Why can't you just use polypropylene?

 on: Today at 02:17:22 AM 
Started by Schattenmaler - Last post by Borek
Apparently because of pH condition (too alcaline), which of course is not impossible to fix, but finding a way to work around it would be great.

Not sure what you mean here - CaCO3 precipitation requires alkaline conditions. Lower the pH and you have karst chemistry, lower it even further and you have fizzling.

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