CoditionalSplit Not Executing Correctly

I have a conditional split where i check for First name ,Last name to see if they are empty.

this is the condition i specify in the conditional split
ISNULL(Column Name)

It dosent remove rows which are empty to a different output..
I tried trim the input column using derived column before sending the data to conditional split but nothing worked.

but after loading the data when i query in the database
select * from TBL_Name
Where Column Name =' '

I get so many records


How to resolve this??