I want to dissolve oxytetracycline (not hydrochloride salt) in a solvent.
It is soluble in organic solvents purged with inert gages , the solvents are DMSO and dimetyl formamide.
Dear Dhruba,
your question is far too general to allow for a simple answer.
You need to consider the purpose of your solution first, such as preparation of a dosage form, preparing a stock solution for antibiotic resistance testing, or maybe weeding out non-transfected bacteria from your expression system. From this you will see your required concentration and which solvents are compatible with your use.
You may also consider whether you really need to use oxytetracyclin free base or whether a salt of it would do.
DMSO and DMF are rather non-volatile, so they are not suitable for any use, where you need to evaporate the solvent at the end. On the other hand, DMSO is a standard solvent for stock solutions of pharmaceutical compounds to be used in biological experiments, such as cell culture testing. Oxytetracyclin is even slightly soluble in DMSO/aqueous buffer mixtures (e.g. 50/50 mixture of DMSO with PBS, pH 7.2).
As mentioned above, you might try another salt if the chloride is the trouble maker. Selecting another salt might render oxytetracyclin soluble in a range of organic solvents, but you may need to experiment a bit.
Alternatively, you may try to use solubilizers such as Tween 80 to obtain an aqueous solution with oxytetracyclin being carried within the surfactant micelles.
Rgds, Michal
Dear Michal
Thanks for the details. You have rightly said that it is difficult to work with DMSO and DMF, since they are nonvolatile solvents. My purpose is not to go for any biological experiment or bioefficacy test right now. My present objective is to solubilize the oxytetracycline in a solvent and finally evaporate the solvent. Hope get more valuable suggestions from you.
Dear Dhruba,
it looks like nobody (except of you, of course) is really interested in the solubility of oxytetracyclin. Thus, I am afraid you may need to do some experimenting.
Oxytetracycline is very slightly soluble in water (313 mg/L), sparingly soluble in ethanol (if similarity with tetracycline holds, the solubility may be in grams/L range).
Oxytetracyclin is soluble in acidic or alkaline solutions.
Not much data is available on the solubility in other solvents, but I would try to experiment with lower alcohols, ketones (such as acetone), maybe lower glymes (such as monomethyl ether of ethylene glycol) and mixtures thereof. Water/organic mixtures might also work. Volatile salts (such as ammonium carbonate) may help and be removed later by prolonged drying in vaccuo at elevated temperature.
Alternatively, you might try to precipitate oxytetracyclin from a solution of the hydrochloride in water. Ammonia would be the preferred base as it is volatile (likewise, the resulting ammonium chloride is volatile).
You can also play with dissolving oxytetracyclin in ammonia water (however, I don't know if that works) and then evaporate the solvent and decompose the ammonia salt by prolonged drying in vaccuo at elevated temperature.
However, using ammonia might cause some side reactions and kill your product. Dimethylamine or trimethylamine might be less reactive, though much more smelly ;-).
Michal
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