There's very little in phenobarbital solubility on the net (both water and alcohol are good)
Wrong. Phenobarbital is only sparingly soluble in water (1 part in 1000 parts water; going down to 1+100 in boiling water), and good soluble in EtOH (1+8 ). It's sodium salt on the other hand is very good water-soluble (1+2), and almost as good soluble in EtOH as the free acid (1+10).
Separation of the named compounds could be achieved by employing their specific acid/base-properties and solubilities:
1. Codeine is a base and can be separated by A/B-extraction at sufficiently basic pH.
2. Aspirine (pKa = 3.5) hydrolyzes easily (at both acidic and alkaline pH) to salicylic acid (pKa = 2.75), which enables it's separation by carefully adjusting the pH during the 2nd A/B-extraction (pKa of phenobarbital is 7.3). I'd think weak bases like NaHCO3 could be helpful here, as is the Henderson-Hasselbalch-equation.
3. Separation of caffeine and phenobarbital can be tried either by using their different solubility in ether (phenobarbital 1+20, caffeine 1+900) or in water (phenobarbital as above, caffeine 1+60, but this ration goes significantly down at higher temperatures).
4. Separating phenobarbital and paracetamol can be achieved easily by using their different solubility in ether (paracetamol <1+1000).
The details you need to figure out on your own.
Peace! -
Murphy
