[Rishi]

I will be glad if someone can clarify my doubts -

1)  Can hygroscopic materials be spray dried ?
2)  Does the pH decrease during the spray drying process ?
3)  Will an alkaline pH have any any effect on the moisture content or the property of the product ?

I just conducted a pilot trial to recover the sodium salt of MCA from water. The liquid solution taken for the spray drying had a pH of 9 ( a mistake while neutralizing). Hence the powder product obtained was comparatively wet and sticky and more importantly I lost a lot of product because it got stuck in the chamber.

Would lowering the pH to 7 solve these problems ? Will it lower the moisture content in the output powder ?

[orgopete]

I don't know the answers to these questions. I have not used a spray drier. Also, I find them too vague to enable a more specific answer.

Q1)  Can hygroscopic materials be spray dried ?

A: If one attempts to remove water in vacuo, will anything else be removed besides water? It depends.

Q2)  Does the pH decrease during the spray drying process ?

A: If a volatile acid is present that can be removed with water, then yes.

Q3)  Will an alkaline pH have any any effect on the moisture content or the property of the product ?

A: It depends on whether the alkalinity is due to a volatile component or not. If NaOH resulted in the alkalinity, it will not vaporize, the hydroxide concentration would increase, and it would retain water. It could also destroy your compound. If the alkalinity were due to ammonia, it would vaporize and the pH would fall.

Q4) I just conducted a pilot trial to recover the sodium salt of MCA from water. The liquid solution taken for the spray drying had a pH of 9 ( a mistake while neutralizing). Hence the powder product obtained was comparatively wet and sticky and more importantly I lost a lot of product because it got stuck in the chamber.

Would lowering the pH to 7 solve these problems ? Will it lower the moisture content in the output powder ?

A: You don't want to add another acid as it will give a salt impurity. Add more MCA to neutralize the solution. I am presuming this is a procedure that has been successful in the past and a solution to recover this sample is desired.