HITC Sport understands Rotherham are poised to sign Plymouth defender.
Purrington has impressed at Plymouth this season and has been instrumental in their push to win promotion from League Two.
The 20-year-old has come through the ranks at Plymouth and he has made over 60 first-team appearances for the club.
Purrington enhanced his growing reputation with two outstanding displays in the FA Cup clashes with Liverpool, helping Plymouth earn a 0-0 draw at Anfield before the Premier League side edged the Pilgrims out 1-0 in the replay.
A number of Championship clubs have been tracking Purrington, but Rotherham have stolen a march on their rivals by agreeing a deal with Plymouth for the left-back.
Plymouth were keen to keep hold of Purrington, but they have reluctantly agreed to sell the left-back as he is in the final six months of his contract at Home Park.
Purrington is understood to be undergoing a medical at Rotherham with the club hopeful of tying up the move before Tuesday's transfer deadline.