Speakers

Scientist specialising in the area of solid form and particle engineering with a back ground in solid state characterisation and crystallography.

Presentation Title: Utilisation of Crystallisation Kinetics to Preferentially Isolate a Meta-Stable Form – Pyrimethanil 3-Nitrobenzoic Acid Salt as a Case Study

Abstract: The number of Active Parametrical Ingredients (API) or Agrochemicals with less-than-ideal physiochemical properties, such as poor solubility, dissolution and physical / chemical stability has increased over the last decade. The solid form strongly influences these properties, and it is vitally important to understand and manufacture the appropriate solid form. Salts and co-crystals have been identified as viable solid forms that may improve the aforementioned properties of development candidates.

Pyrimethanil, a broad-spectrum fungicide, is able to form both a salt and co-crystal form with 3-nitrobenzoic acid. Previous studies have shown the co-crystal to be the thermodynamically stable form and is readily generated via crystallisation from solution. However, the salt is a metastable kinetic form, the isolation of which has been shown to be challenging. The salt form appears as a white powder whilst the co-crystal forms appear as a distinctive yellow powder.

The aim of this study was to develop scalable and transferable processes to produce reliably and selectively the metastable and the stable forms (salt and co-crystal) of pyrimethanil/3-nitrobenzoic acid. In this study, we demonstrate how through careful tuning of procedure parameters, such as temperature and solvent composition, the salt and co-crystal forms can be selectively isolated in pure phases by understanding the crystallisation kinetics of each system.

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