The invention relates to a method and a device for purifying mixtures of substances by means of optionally fractional crystallization. The strap can thus be used to create a loop or a ring in order to attach or bear a load. The one or more permission indicators and the sequence of instructions are provided to a remote device. Instead, the user has had to connect, for example, using a RAS connection, to one of the email accounts and then terminate that RAS connection before initiating a new RAS connection to the next type of email account. The complementary datum features on both shield and shield retention stage enable accurate and repeatable positioning of the sample in the apparatus for sample processing and reprocessing.