Solid State Characterization

In an overwhelming majority of cases, drugs and similar products are produced in solid form to ensure that consumption provides a well-balanced and rapid effect. Selecting the optimum solid form for an incredible variety of medicinal compounds is critical to the development of today’s pharmaceuticals.

Because pharmaceutical compounds can exist in more than a single form or crystal structure, a property called polymorphism, their biopharmaceutical characteristics can change depending on their physical attributes.

Current drug polymorph screening techniques are remarkably effective at identifying and characterizing solid-state substances. With such powerful information on hand, pharmaceutical chemists can more accurately determine the optimal physical form for a drug substance as well as develop methods to ensure it does not change over time.

Pharmaceutical Solid-state Characterization Techniques at Avomeen

Our solid-state characterization and testing labs perform rapid screens for polymorphs involving 25 crystallization conditions from 5-6 different solvents in order to determine most of the stable polymorphs. Polymorph testing and solid state  characterization services are performed using a variety of techniques, including:

  • Differential Scanning Calorimetry (DSC) – to determine melting points, which vary amongst polymorphs
  • Powder X-ray Diffraction (XRD) – Rapid analysis technique developed for phase identification of crystalline material to help determine unit cell dimensions, unique to each solid state form.
  • Solid-state NMR – Nuclear Magnetic Resonance (NMR) spectroscopy takes advantage of orientation-dependent interactions to characterize the forms and is one of the only polymorph screening techniques that is usable to monitor the solid state form in products that have a large amorphous composition like creams, lotions, and ointments.
  • Hot Stage and Polarized Microscopy – Measures melting points as well as provides a visual determination of crystal form. It is one of the few solid state characterization techniques that is truly non-contact making it amenable to sensitive drug substances that change form with handling.
  • FTIR – Measures absorption of infrared radiation at different wavelengths, creating an infrared spectrum that has some sensitivity to solid state form.

The turnaround time for a polymorph screen is dependent on the extent of characterization required. The study can be extended to use binary solvents, pH, and additives to discover and characterize the metastable forms as well. We can also develop and validate methods for process control of the solid-state form. Such methods may involve DSC, TGA, XRD, FTIR, or Solid-state NMR.

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