How to ensure column names are double quoted while using execute format when building a stored procedure?

The following command runs but does not produce results as expected.

 

Execute Format('insert into stats select %L as id, %2$L as checks, count(%3$s) from %4$s where %5$s is null', i, 'count of nulls in '||col, col, t_name, col);

There should be a lot of nulls in columns, but it produces o count.

All columns have got capital letters in.  How to ensure that the columns are double-quote when they are fed in as variables.

Regards,

David