Measurement and Prediction of Solubility of Paracetamol in Water−Isopropanol Solution. Part 1. Measurement and Data Analysis

An attempt has been made to measure the concentration of paracetamol (98%, Aldrich Chemical Co. Inc., MO) in different solutions using an in situ ATR-FTIR device and chemometrics. A partial least-squares (PLS1) algorithm has been applied to construct two calibration models for paracetamol concentration, water mass percent, and temperature. The models and errors have been analyzed using validation data sets and diagnostic tools. The models are then used to evaluate the solubility of paracetamol (PA) in pure isopropanol, pure water, and isopropanol−water mixtures in the temperature range 5−40 °C. The solubility of paracetamol in isopropanol−water mixtures shows a maximum at almost 20 water mass percent. For some selected data points, the measured solubility by the FTIR is in good agreement with the corresponding solubility measured using the gravimetric method. Also the solubility in pure isopropanol and water is in reasonable agreement with the data reported in the literature.