The impact of solvent systems, process conditions and structurally related impurities on the growth rate and morphologies of paracetamol crystals

Single crystal growth (S.C.G) experiments were conducted to investigate face specific growth rates of paracetamol (acetaminophen) crystals. There are a few examples in literature where S.C.G of paracetamol crystals and different process conditions are analysed [1] but no examples of the addition of structurally related impurities (Metacetamol and Acetanilide) can be found. Carefully selected conditions of supersaturation and temperature were also analysed. The resulting growth rates were then determined in two solvents, ethanol and 3-Methyl-1-butanol. The impact of the structurally related impurities on the solubility of paracetamol was determined in each of solvents investigated. The relative growth rates of pairs of faces and the associated habit change of monoclinic paracetamol was observed using in-situ optical microscopy. The respective growth rates increased with an increase of supersaturation and temperature, as the impurity concentration increased the relative growth rate of the faces decrease