You can set up your EndNote library to identify retracted articles.
Retracted articles will be flagged at Library level and in the individual references for retracted articles.
To activate retraction alerts:
Once you are logged into your online account, EndNote desktop will automatically check for retractions:
The retraction data is drawn from the Retraction Watch database. To find out why EndNote has added a retraction you can look the article up in this database by any number of fields (DOI or PMID are certainly the quickest and most precise if you have them).