Experimental and QSAR studies on adsorptive interaction of anionic nonsteroidal anti-inflammatory drugs with activated charcoal

Adsorptive interactions, namely adsorption capacity (q_m) and affinity (b), between nonsteroidal anti-inflammatory drugs (NSAIDs) in anionic forms and commercial activated charcoal (AC), were estimated by isotherm experiment in a batch, and the properties were modeled based on the concept of quantitative structure–activity relationship (QSAR). Experimental results showed that AC had a high q_m (0.38–0.67 mmol g⁻¹) and b (14.03–930.8 L mmol⁻¹) for the selected NSAIDs. In QSAR modeling, linear free energy relationship (LFER) descriptors of excess molar refraction (E), dipolarity/polarizability (S), and Coulombic interactions of anions (J⁻) were highly related to log q_m, and the combination of the three terms could predict log q_m in R² of 0.97 and SE of 0.015 log unit. In the case of b, only single B term showed a good correlation with log b in R² of 0.81. Additionally, the combination of hydrogen-bonding acceptors (HBAs) and molar volume (MV), which are easily calculable parameters, could also derive good predictability in R² = 0.81 and SE = 0.26 log unit. Afterwards, validation of the QSAR models based on the leave-one-out cross-validation (Q²_LOO) method showed that the models were acceptable.