Our individually designed studies enable us to rationally select the most suitable salt form for long-term success.

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Salt Screening & Selection

Helping our clients understand and select the best salt form to take forward in development.

The selection of the most appropriate salt of an API provides an opportunity to alter its physicochemical properties and biologic characteristics. Salts are most commonly employed for modifying aqueous solubility; however, the salt form selected will influence a range of other properties, such as: hygroscopicity, chemical stability, dissolution rate, crystallinity and physical stability.

At Pii, salt screens are  carefully planned to address the required improvement of the API. Our individually designed studies enable us to rationally select suitable counter-ions for salt formation and is restricted to acids/bases and solvents suitable for pharmaceutical manufacturing. Such studies are designed to explore a range of stoichiometries and to optimise crystallization conditions for a particular crystalline form.

For companies with limited sample quantities, crystallization experiments are performed in specially designed microtiter plates that are individually sealed. After crystallization and solid-liquid separation, the solid samples are then characterised using:

  • High-throughput Raman spectroscopy (96 well plate)
  • 96 well plate reading transmission X-ray diffraction system
  • State-of-the-art chemometric software to speed up hit identification, with the resulting spectra grouped and assigned

Once salts have been identified,  the most suitable formulated salts are scaled up and physically screened using the following techniques:

  • X-ray crystallography
  • Thermal Analysis – DSC, TGA, hot-stage microscopy
  • Spectroscopy – NMR and FTIR
  • Solubility, intrinsic dissolution and purity by HPLC

Studies are carried for each of the solid forms, allowing us to rank order the salts with respect to suitability and functionality. This then allows you to move forward with confidence on their drug compound selection program.

As well as identifying suitable salt forms to alter the physicochemical properties of the API, our technologies may also be used for increased patent protection.

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