Imprinted silicas for paracetamol preconcentration prepared by the sol–gel process

Paracetamol-imprinted silicas were prepared by three sol–gel routes, including two basic-catalyzed gelification and precipitation routes, and an acid-catalyzed route. The resulting materials from basic gelification were subjected to Soxhlet, ultrasound and thermal extractions, and characterized by infrared spectroscopy, elemental analysis, nitrogen porosimetry, scanning electron microscopy, and atomic force microscopy. Ultrasound was shown to be the most efficient for template extraction. The resulting materials showed surface areas between 30 m2 g−1 (for the precipitation route) and 200 m2 g−1 (for the acid-catalyzed route). After paracetamol extraction, the resulting surface area was between 30 m2 g−1 and 290 m2 g−1. The presence of paracetamol was confirmed by the presence of an infrared absorption band at 1546 cm−1, which is assigned to ν (C=O). The adsorption of paracetamol from aqueous and urine matrixes on the imprinted materials produced by the acid-catalyzed route was ca. 60% of the nominal concentration present in such matrixes. In the silica without molecular imprints, the preconcentration was ca. 20%.