Assume your data having Time Stamp and email I.d.s Starts in C7.
1. Then go to a Empty column let us say D.
Let us say D7 is the 1st Cell.
1. In D7 use
=LEFT(C7,FIND("@",C7))
---> Gives Time stamp and I.ds ending with @
2.Go to next column Let us say E.
In E7 use
=RIGHT(E7,11)
---> Gives Data with student I.ds
3.Now you can Select all data and SORT in Ascending order
4. Go to “DATA” in Menu and Choose “Remove Duplicate Entries”