Hi,
we recently had problems with some syntheses where we use nitrogen flow to remove a byproduct (tBu-SH) from a reduction reaction from a reaction mixture. The educt is a StBu-protected peptide which we treat with excess TCEP in aqueous solution. For hydrogel formation, we had really soft gels and cells degraded the matrices really quick.
We did everything identical to earlier produced batches (which worked perfectly) and now we think it may be the nitrogen source. We leave the reaction mixture stirring over night under nitrogen flow and if there are traces of oxygen left - with time, the product will get oxidized may yielding to the low reactivity.
Now the question: How can we simply and quickly test the compostiton of the nitrogen gas we have in the institute? Anything to consider? Burn out the test flask etc... It is supplied from a company and they fill a huge tank every week.
Hi Michael,
thanks for your valuable answer. Since we routinely use this technique (spend many liters nitrogen for one synthesis) and that cartridges are rather expensive and have a restricted oxygen capture capability, I'd like to know the exact composition of that gas first if it is really necessary to buy that.
In the past, it worked all the time and this problems occured recently.
The best way to quickly measure oxygen, nirogen and other contaminants in gas samples is by GC. A simple unit with mol sieve run at room temperature or below will work very well. With a TCD (thermal conductivity detector), sensitivity down to about 10 ppm is easy; much lower levels can be detected using a helium photoionization detector.. One must chose the right mol sieve material, just to make sure the argon is separated from the oxygen. Otherwise, some errors can happen.
Scot Abbott gave - in my view - the best option to detect oxygen in a gas sample. Just to be clearer: mol sieve is the molecular sieve kind of gas chromatography column. If Marcus know anyone in his vicinity that has this kind of column installed or has a supplier of equipment and column who would like to give some support, his problem would be well attended. Good luck!
Hi Scott and Ademario,
thanks for your suggestions, I will have a meeting with the analytics facility of my institute soon, they already did such measurements in the past. Hope that they can help me.
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