How to identify unicode text in sql?

Table1 has nvarchar column called umsg which contains unicode text and some time english also.

I want to find out English text present in umsg column.

select *
from table1
where
RDate >='01/01/2014' and RDate < '09/26/2017'
and umsg = convert(varchar(max), umsg)

I used above query that work fine in regional language but some time fail. Suppose col contain text like 'ref no été' I think above message is unicode, if I used above query, it/sql is showing me as English not unicode.How to handle this

Table :
Id Date Umsg
1 2017-09-12 00:00:00.000 The livers detoxification processes.
2 2017-09-11 00:00:00.000 Purposely added 1
3 2017-09-10 00:00:00.000 ??????? ?? ????-???? ????? ?? ?? ???? ?? ???????? ?? ????? ?? ??? ????
4 2017-09-17 00:00:00.000 ???? ?? ?????? ?????? ??? ???? ??? ??? ??? ???? ?? ????? ?? ??? ???? ?
5 2017-09-17 00:00:00.000 ref no été

Above is data present in my table. But I want data/Output like :

Id Date Umsg
1 2017-09-12 00:00:00.000 The livers detoxification processes.
2 2017-09-11 00:00:00.000 Purposely added 1