Identifying Reason for Column Name Returned by SELECT

   I run this SELECT statement on a table:

select distinct(site_id) from chemistry order by site_id;

and in the returned set I see:

  GW-21
  GW-22
  GW-22         +

  GW-24

   I want to find that row returning 'GW-22      +' because I believe it
should be 'GW-23'. However, my attempts to retrieve that row keep failing.
I've tried these statements:

select count(*) from chemistry where site_id = 'GW-22         +';
  count
-------
      0
(1 row)

yet,

select count(*) from chemistry where site_id = 'GW-22';
  count
-------
    803
(1 row)

   Looking for the blank row also fails when I try to specify site_id as is
null, = ' ', or =''.

   Please point me to the proper way of finding this rogue row so I can
correct the value in the site_id column.

TIA,

Rich