An online control in production of crystalline substances with respect to their morphology or a solvent mediated phase transfer is of key importance in many industries. Here two rather new PAT tools are tested. Monitoring of solvent mediated phase transition by ultrasound (single frequency) and 3D optical reflectance measurement (ORM) (advanced particle analyzing system (APAS)) is evaluated based on case studies with sulfathiazole, magnesium sulfate and di-sodium tetraborate. The achieved results by the in-line PAT tools are proven by optical microscopy. The different solvates and polymorphic forms could be detected by the use of ultrasound (single frequency) and 3D ORM (APAS) techniques, however, the application of these techniques does not work in all cases, but always at least one is working. There are limitations with respect to the nature of the examined substances. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.