[h11c]

Hello!

I am an MS student and I am working on starch crosslinking. My crosslinking agent has aldehyde groups and the crosslinking reaction occurs through the attach of these aldehyde groups to OH on starch.

I am studying the kinetics of this crosslinking mechanism (rate order, rate constant, A and Ea) right now. I am struggling to find a proper way to do it since we don't know the initial concentration of OH groups in the complex structured starch. I thought I can find the concentration of crosslinking agent with titration. After crosslinking, OH and aldehyde groups will form Acetal groups. I will separate the crosslinked starch film. One will swell in water and the titration will give m the unreacted crosslinking agent. The other will be dissolved in an alkali and this will give me the unreacted and reacted crosslinking agents. However I couldn't find a good procedure for this titration, I mean I cannot find a proper titrant or titration method.

Does anybody have an idea about it?

I'd appreciate any help, because my graduation depends on the result of this experiment

Thanks a lot!

[Borek]

Please elaborate on what are the reactions you want to base your titration on, I don't see it now.

[h11c]

Crosslinking:
R-COH + Starch-OH --> R-CH(OStarch)2

Titration:

For only the unreacted crosslinking agent:
R-CH(OStarch)2 + H2O --> R-COH (unreacted)

For both unreacted and reacted crosslinking agent:
Starch-OH + NaOH --> Starch-ONa
R-CH(OStarch)2 +H2O + H+ --> R-COH

So I want to determine R-COH (the reducing sugar in my case) concentration. However the reducing sugar is crosslinked Starch in the acetal form, so I need to form an aldehyde from acetal again.

And the method I am planning to use for titration:

R-COH + NaHSO3 --> R-CHOHSO3Na
NaHSO3 exces + I2 --> NaHSO4  + 2HI
I2  excess + 2S2O32- -->  ….

Thank you!