<Chat id: 7, private: true, title: "Private Chat", created_at: "2016-01-25 08:50:03", updated_at: "2016-01-25 08:50:03", user_id: 1, privatemail: "darelvc@gmail.com, istokvc@gmail.com">

"darelvc@gmail.com, istokvc@gmail.com"

chat.split(", ").uniq!

["element@gmail.com", "darelvc@gmail.com"]

chat_new = chat.privatemail.split(", ").uniq
 => ["darelvc@gmail.com", "istokvc@gmail.com"]

2.2.1 :020 > chat_new.all? {|element| chat_new.include?("darelvc@gmail.com")}
 => true