Hello,
depends what ASE version you are using.
1) You can dump the B10 database and then drop it. Now rebuild your database with create database / alter database on the devices you already specified. You should have B10 data and log devices, make sure the database fits into these devices. Then load the database dump from your backup. After this the master device shouldn't contain any B10 fragments anymore.
2) If you use SP122 or higher, you can use alter database log off or off to shrink the database, see the SAP Notes 2000203 (SAP restrictions) and 1881347 (how to use alter database off / log off) for details.
Hope this will help.
Regards
Stefan