Security per database in SQL Azure Pool
You can restrict user per database.  I will explain here using sql authentication and you can do the same if you have AD set up.

I have 3 database and 'taiobmdjamshed' is the server admin and have access to all the databases.



I create security1 login with db_owner privilege to security1 database and a user at master database.

CREATE LOGIN security1 
    WITH PASSWORD = 'S&lt;&lt;MM12345!@@!' 
GO


Create a user in master database.

CREATE USER security1
    FOR LOGIN security1
    WITH DEFAULT_SCHEMA = dbo
GO


Make a user in security1 database and make it a member of db_owner role.

CREATE USER security1
    FOR LOGIN security1
    WITH DEFAULT_SCHEMA = dbo
GO

-- Add user to the database owner role
EXEC sp_addrolemember N'db_owner', N'security1'
GO


If connecting to the server using security1 login and try to access security2 database this is what will happen because security1 login does not have a corresponding user or privilege in security2 database.




This link explains more in details.