Chromatography Forum

Dear all,
I am trying to quantify free hydrazine in one analyte ( hydrazine is part of the structure). I tried derivitization method with salicyladehyde and NH4OH buffer and then UV DETECTION. I could not get reproducible results and more over , the hydrazine levels are increasing over the time in solution. I tried using the chiller ( autosampler) and no use. The analyte is not stable in aqueous solutions. Did anyone tried GC FID methods. Please let me know.

thanks

Hi

Think there are a bunch of commercial hydrazine test kits based on reaction with p-Dimethylamino-benzaldehyde, have you looked at those if they may be useful? Possibly p-Dimethylamino-benzaldehyde may have some advatage compared to salicyladehyde.

It is not impossible that your choice of reagents/buffer cause increase of hydrazine if it reacts with your analyte which contain hydrazine structure, I suggest you discuss that possiblility with an organic chemist.

Thank you. I am sure that the analyte in solution is releasing the hydrazine since the analyte is not stable in solution ( higher pH, more degradation). I was thinking adding acetone to the analyte and convert free hydrazine to azine and analyte by GC.

Regards,
kishore

OK

If analyte is not particular water soluble, you could consider solvent extraction, organic:sulfuric acid (diluted), hydrazine is transformed to hydrazine sulfate. Water/sulfuric acid extract is then neutraziled pH wise (something like 8-9 in pH might be needed-guessing a bit) to reform hydrazine and then continue with classic aldehyde colour reaction.

krickos, what is hydrazine sulfate?

If you use acetone to dissolve the sample, hydrazine will react and you will be able to see it on GC/FID.

GCguy

gcguy, have you done this reaction between acetone and hydrazine?

krickos, what is hydrazine sulfate?

You are correct, I should have stated hydrazine hydrogen sulfate. Apologise for any confusion.

In answer to the question from HW Mueller....

We routinely perform this analysis with typical levels of less than 1%. It meets all our validation criteria, with excellent recovery figures.

GCguy

gcguy, without catalyst?
I am trying to say that we can not help here if we don´t know more about the chemistry of the analyte.

I can't discuss too much about the sample matrix, but what I can say is that the test was developed to allow the measurement of hydrazine in spent acidic liquors.
The method itself uses a pseudo standard to avoid the routine use of hydrazine. The relative response factor for the two compounds was calculated during the development stage and this was tested by spiked recovery in both neat acetone and the sample itself. This was found to give good values. The derivatisation is not instantaneous, it takes about 10 mins in an ultrasonic bath and again this time was checked by recovery calculation. No catalyst was required.
The GC method uses a 624 coulmn and is currently being used on a routine basis as part of process control for a production plant which reports back a good mass balance for hydrazine usage.

Hope this is of some help.
GCguy

It sounds like this is acid catalyzed. (The pseudo standard is even more toxic than hydrazine?)

The pseudo standard we use is non toxic. I don't think the reaction requires catalysis as we have seen good conversion when there has been no acid present. i.e. dissolving hydrazine in neat acetone gives good recovery.

GCguy