I'd been pondering the discovery of plasticiser in Alberto Contador's doping control sample, when I came across an excellent overview at the VeloNews site (The Explainer: Plastics - VeloNews).  It's well worth reading to put the latest accusation in perspective. It would not seem to be an open and shut case. And furthermore, the issue of the sensitivity of testing lab procedures really needs to be addressed.  If WADA-accreditation requires a particular detection limit for clenbuterol, than that needs to be the limit for consideration as a positive test result.  Otherwise dope-testing becomes a lottery where some riders escape sanction because their samples were sent to a laboratory with less sensitive equipment.