Remove duplicate nodes from xml using c#

[C# Programming]

I an having some trouble with removing duplicate entries from an xml file.
I am using mostly Linq to XML and C# to build the list.So I would like a Linq to Xml aproach further too.
Example(before):

new_id

word1II.?

definition1


new_id

word2I

definition2


new_id

word1II.?

definition1


After it should be:


new_id

word1II.?

definition1


new_id

word2I

definition2


The xml database should have around 100k entries like this, so I need a fast method to remove duplicates. Thanks in advance