If 1g of the API is dissolved in 150ml of the organic solvent or 250ml of the organic solvent and spray drying is done, then during spray drying the organic solvent will vaporize and the bed will contain 1g of API only. Dilution of the spray drying solution is increased when the bed volume(on which the spraying is done) is increased. This is to maintain API concentration more uniformly throughout the bed.

Hey Debarati,

The first bit is totally understandable. Can you please elaborate more on the volume bed increase/decrease phenomenon? The theoretical mass yield of the powder excipients is set standard every time. What changes if I increase the initial volume of solvent?

Thanks

You can target the particle size you need by adjusting the spray parameters. You are dissolving the API in organic solvents which will evaporate. Therefore you have pure API particle in the collector, unless you are mixing it with excipients making the concentration relevant. The ratio can be adjusted through the flow rate in each nozzle of the spray dryer head.

Dear Andrei,

My API is mixed with other excipients in a 'soup' form of a solvent mixture.

I guess the dilution and/or concentration, respectively, of the initial target volume that we set (e.g. all ingredients to be dissolved in 100 mL solvent) determines somehow the final concentration of all excipients in the spray-dried powder that we finally collect. What's your opinion about that?