Engineering Processing Properties of Acetaminophen by Cosolvent Screening
The authors used common solvents to develop an initial solvent-screening method for laboratory-scale research to determine the solubility, polymorphism, and crystal properties of various active ingredients.
Aug 2, 2010 By:
Tu Lee, Gen Da Chang Pharmaceutical Technology
Table II: Theoretical yield, apparent heat of solution, Gibb's free energy of dissolution, aspect ratio, enthalpy of melting,
and crystallinity of acetaminophen Form I crystals grown from or dissolved in cosolvent systems.
Out of the 100 cosolvent systems, the authors constructed only 92 solubility curves represented as van't Hoff plots because
eight cosolvent systems (i.e., THF and N-butyl alcohol, THF and DMF, methanol and DMSO, methanol and 1,4-dioxane, methanol and ethanol, ethanol and 1,4-dioxane, DMSO
and benzyl alcohol, and DMF and benzyl alcohol) had exhibited light pink–orange color, thus indicating the possible formation
of two side-products of acetaminophen oxidation (i.e., p-benzoquinonemonoimine and p-benzoquinone) (see Table II) (16).
In general, a cosolvent system was a better solubilizer than a single solvent system (7). The theoretical yield (i.e., the
amount of crystalline solids that would result if the saturated solution at 60 °C were cooled to 25 °C) was approximated from
each solubility curve using the following equation:
Table II (Continued).
where Sh is the solubility (g/mL) at 60 °C, and SL is the solubility (g/mL) at 25 °C. The cosolvent system of benzyl alcohol and acetonitrile and the cosolvent system of ethanol
and acetone gave a maximum theoretical yield of 71.73% and a minimum of 17.94%, respectively (see Table II). These results
implied that the interactions between protic benzyl alcohol and polar aprotic acetonitrile were relatively weak and more sensitive
to temperature change than the relatively strong interactions between hydrogen-bond donating ethanol and hydrogen-bond accepting