Create Login From Master

Is there any way I can create a login for a database while the database context is master or not the particular database.
I am trying to do something like this.......
USE [master]
GO

DECLARE @STRSQL VARCHAR(2000),
@DATABASE_NAME VARCHAR(50),
@DB_PATH VARCHAR(200),
@DB_USER VARCHAR(25)
SET @DATABASE_NAME='TDB4x'
SET @DB_PATH='D:Database'
SET @DB_USER='TDB4Test'

DECLARE @SQL_DB varchar(20),
@STRSQL1 varchar(500),
@STRSQL2 varchar(500),
@STRSQL3 varchar(500),
@STRSQL4 varchar(500)

SET @SQL_DB='USE '+@DATABASE_NAME
SET @STRSQL1=(' IF NOT EXISTS (SELECT *
FROM sys.server_principals
WHERE name='''+@DB_USER+''')')
SET @STRSQL2=(' BEGIN
CREATE LOGIN '+@DB_USER+'
WITH PASSWORD=N'''+@DB_USER+''',
DEFAULT_DATABASE=['+@DATABASE_NAME+'],
DEFAULT_LANGUAGE=[us_english],
CHECK_EXPIRATION=OFF,
CHECK_POLICY=OFF
END')
SET @STRSQL3=(' EXEC sys.sp_addsrvrolemember @loginame = N'''+@DB_USER+''', @rolename = N''sysadmin''')
SET @STRSQL4=(' ALTER LOGIN ['+@DB_USER+'] DISABLE')
EXEC (@SQL_DB+@STRSQL1+@STRSQL2+@STRSQL3+@STRSQL4)

The login is successfully created, but I cannot find the user in the specific database. Is there any other way this can be accomplished?