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Why is NH4OH used in Polarimetric analysis?
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Moiz Saif
Why is NH4OH used in Polarimetric analysis?
If I'm not wrong, this is about polarimetry, not polarography. (No dripping mercury, but optical rotation).
If your sugar is a hexose, the following species will exist in aqueous solution:
open form (a bit)
furanose (traces)
pyranoses (major amount)
The pyranoses will adopt the $\alpha$- and the $\beta$-form. Both rotate polarized light by a different angle.
The interconversion between these forms (mutarotation) is facilitated by addition of acid or base. Thus, an equilibrium, resulting in a constant angle in polarimetry, is reached faster.
If I'm not wrong, this is about polarimetry, not polarography. (No dripping mercury, but optical rotation).
If your sugar is a hexose, the following species will exist in aqueous solution:
open form (a bit)
furanose (traces)
pyranoses (major amount)
The pyranoses will adopt the $\alpha$- and the $\beta$-form. Both rotate polarized light by a different angle.
The interconversion between these forms (mutarotation) is facilitated by addition of acid or base. Thus, an equilibrium, resulting in a constant angle in polarimetry, is reached faster.
Do you see a potential corresponding to the sugars, or to their Schiff bases, or to said imines' trimers? Perhaps ammonia gives you a nice pH buffer, as opposed to alkali hydroxides that will wildly swing pH and allow Cannizzaro disproportionation of reducing sugars' aldehyde groups at high pH. Ammonia does not reduce at the cathode.
Do you see a potential corresponding to the sugars, or to their Schiff bases, or to said imines' trimers? Perhaps ammonia gives you a nice pH buffer, as opposed to alkali hydroxides that will wildly swing pH and allow Cannizzaro disproportionation of reducing sugars' aldehyde groups at high pH. Ammonia does not reduce at the cathode.
If I'm not wrong, this is about polarimetry, not polarography. (No dripping mercury, but optical rotation).
If your sugar is a hexose, the following species will exist in aqueous solution:
The pyranoses will adopt the $\alpha$- and the $\beta$-form. Both rotate polarized light by a different angle.
The interconversion between these forms (mutarotation) is facilitated by addition of acid or base. Thus, an equilibrium, resulting in a constant angle in polarimetry, is reached faster.
If I'm not wrong, this is about polarimetry, not polarography. (No dripping mercury, but optical rotation).
If your sugar is a hexose, the following species will exist in aqueous solution:
The pyranoses will adopt the $\alpha$- and the $\beta$-form. Both rotate polarized light by a different angle.
The interconversion between these forms (mutarotation) is facilitated by addition of acid or base. Thus, an equilibrium, resulting in a constant angle in polarimetry, is reached faster.
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Do you see a potential corresponding to the sugars, or to their Schiff bases, or to said imines' trimers? Perhaps ammonia gives you a nice pH buffer, as opposed to alkali hydroxides that will wildly swing pH and allow Cannizzaro disproportionation of reducing sugars' aldehyde groups at high pH. Ammonia does not reduce at the cathode.
Do you see a potential corresponding to the sugars, or to their Schiff bases, or to said imines' trimers? Perhaps ammonia gives you a nice pH buffer, as opposed to alkali hydroxides that will wildly swing pH and allow Cannizzaro disproportionation of reducing sugars' aldehyde groups at high pH. Ammonia does not reduce at the cathode.
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