The current invention describes novel immunogens which are used in the production of novel antibodies with unique binding properties in that they cross-react with a variety of phenylpiperazine derivatives. These antibodies enable methods and kits to detect and/or determine phenylpiperazine derivatives (for example mCPP, TFMPP and MeOPP) in an in vitro sample which are advantageous over currently available analytical methods in terms of cost, ease of use, speed and sensitivity.