Abstract <p>Silica modified with polyamines, polyhexamethylene guanidine (<b>SiO</b>_<b>2</b><b>-PHMG</b>) and polydimethyldiallylammonium (<b>SiO</b>_<b>2</b><b>-PDDA</b>) is proposed for the sorption preconcentration of antibiotic cefotaxime from aqueous solutions. The maximum recovery (91–93%) of cefotaxime is achieved at pH 3.9–4.3, with a sorption equilibrium time of 10 min. The sorption capacity of the sorbents for cefotaxime, determined from horizontal sections of sorption isotherms, is ∼74 μmol/g, and the distribution coefficient is 1 × 10³ cm³/g. Under dynamic concentration conditions, the recovery of cefotaxime is 99%. Cefotaxime exhibits yellow-green luminescence on the surface of sorbents when irradiated with UV light. The luminescence spectrum is a broad band with a maximum at 470 nm. The maximum luminescence intensity of cefotaxime is observed under the conditions of its quantitative extraction. A procedure is developed for the sorption–luminescence determination of cefotaxime with a limit of detection of 0.13 mg/L for the SiO₂-PDDA sorbent and 0.25 mg/L for the SiO₂-PHMG sorbent. The linearity of the calibration curve is maintained over the ranges 0.5–25 mg/L and 1–50 mg/L using SiO₂-PDDA and SiO₂-PHMG, respectively. The relative standard deviation does not exceed 0.09. The procedure is tested for the determination of cefotaxime in a pharmaceutical preparation and in a model solution.</p>