You can use -W switch.
From BOL :
-W
This option removes trailing spaces from a column. Use this option along with the -s option when preparing data that is to be exported to another application. Cannot be used with the -y or -Y options.
Check http://msdn.microsoft.com/en-us/library/ms162773.aspx
Madhu
MCITP, MCTS, MCDBA,MCP-- Blog : http://experiencing-sql-server-2008.blogspot.com/