The polysaccharide is hydrophobically modified. It is assumed to have some hydrophobicity. So how to determine the HLB value. The polysaccharide has MW of about 200 kDa.
As defined by Griffin the Hydrophilic-Lipophilic-Balance of an amphipathic molecule may be calculated using the following mathematical equation:
HLB= 1/5 * [(MW of Hydrophylic portion of the molecule) / (MW of the whole molecule)] * 100
the ratio between the molecular weight of the hydrophilic part and the whole of the surfactant molecule, divided by 5
With this method an hypotetical molecule completely hydrophilic has a value of 1/5 * 100= 20
while an hypothetical molecule completely hydrophobic has a value of 0. This indicates that the HLB range is comprised from 0 to 20 units.
As the definition indicates, the native polisaccharide may be considered completely hydrophilic (HLB=20) and the HLB of the modified molecule may be calculated if you know how many lipophilic chains (and so their weight) are bonded. To estimate the ratio of substitution I would use High-field NMR spectroscopy, comparing the integrals relative to characteristics proton signals, of the lipophilic and hydrophilic parts of the molecule.
Thank you Alsessandro. I have the ds (degree of substitution) of the lipophic part.
Do you know any formula for hlb using ds?
Can i consider hlb as zero for the lipophilic part?
Dear Nirali, you're welcome.
The value 0 of HLB is for an hypothetical molecule completely hydrophobic.
Your poysaccharide has a MW of 200 KD before or after the derivatization?
If it is the MW before dreivatization, since you know the sudstitution degree, you may know how many hydrogen of the plysaccharide are substituted by a lipophilic chain. So you may calculate the MW of the hydrophilic part and the MW of the whole substituted molecule because you know how many chains are bonded and also the MW of these chains. These value should be placed in the mathematical equation:
HLB= 1/5 * [(MW of Hydrophylic portion of the molecule) / (MW of the whole molecule)] * 100
Hello Alessandro Venditti, could you, please give the complete reference of the Griffin method, if you have it, because i need it too. Thank you in advance
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