A screening design of experiments has been applied to the supercritical antisolvent precipitation of ampicillin
(APC) using carbon dioxide (CO2) and N-methylpyrrolidone (NMP) as antisolvent and solvent, respectively.
The proposed design of experiment (DOE) is useful for identifying the key factors involved in the SAS
process in just a few runs at an early stage of experimentation. Seven factors were studied, and two levels
were assigned to each. A fractional factorial design with 2
−
experiments plus two additional runs to calculate
the accuracy of the estimates was used. The mean particle size (PS) and particle size distribution (PSD) of
the processed ampicillin were chosen as responses to evaluate the process performance. Within the range of
operating conditions investigated, concentration, temperature, and nozzle diameter proved to be the key factors
having the greatest effect on both PS and PSD and, thus, the most important factors for controlling the formation
of submicrometer particles of ampicillin by the SAS technique.
The solubility of palmitic acid in supercritical carbon dioxide has been determined experimentally in the
pressure range (100 to 350) bar and the temperature range (35 to 55) °C. A cubic equation of state and
an empirical equation have been used to correlate the solubility of this fatty acid in supercritical carbon
dioxide. The first method, which is based on thermodynamic properties, uses two fitting parameters, the
solid sublimation pressure and the binary interaction parameter. The sublimation pressure values obtained
have been correlated using the Clapeyron equation. The interaction parameter has been correlated as a
function of temperature. The empirical method is based on an equation that relates the solubility of the
solid with the operation conditions. The empirical and equation of state methods provide good agreement
between theory and experimental results for the solubility of palmitic acid in supercritical carbon dioxide.
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