The pair were out of contract at the Iron, and indicated they would sign with other clubs. Mirfin turned down a contract, while the indication is talks with Murphy did not get that far.
Josh Wright, Ian Morris, Rory Coleman, Johnathan Williams and Paris Cowan-Hall have been released.
The departure of Wright has been inevitable for months given his January transfer request and drop in form, but it is a surprise he was not offered a deal to ensure the club received a transfer fee for him.
As he is under the age of 24, he was not able to leave Glanford Park on a free transfer.
Goalkeeper Sam Slocombe has had his contract extended by a year, and he will provide cover for new No.1 Josh Lillis.
Defender Eddie Nolan remains contracted for a further 12 months, having signed an 18-month deal when he joined in Preston rather than the six-month one originally announced.