Solvent Density's Relationship to Molecular Weight
My company utilizes CO2 as a solvent to extract a wide variety of compounds from raw botanical material.
I would like to better understand the relationship between the density of the CO2 as it passes through the biomass, and what type of compounds it would pull.
One of my colleagues theorized that the the relationship between the density and molecular weight of the compounds we are targeting exist as a 1:1 ratio - meaning that if the density of the CO2 is less then the weight of the molecule, the molecule should not be extracted.
The reasoning behind my colleagues theory is as follows:
When we extract terpenes (molecular weight of ~ 136 g/mol) we use a solvent density of ~290 Kg/m3. When using this density, we extract clean terpenes with no alpha or beta acids contaminating the extract. That density is lower than the molecular weight of the alpha and beta acids - although the unit of measurement is different.
Most of the alpha and beta acids we target have a molecular weight of ~314 g/mol, and a lot of the waxes, fats, and lipids in our biomass typically have a molecular weight of ~ 352 g/mol.
I have a hard time believing it can be this simple, but if we were to use a solvent density of ~ 330 Kg/m3, would we be able to extract the 314 g/mol compounds without being able to extract the undesired compounds at 352 g/mol?