Determination of ceftriaxone by the fluorescence quenching of quantum dots using binding with polyethyleneimine

It is found that antibiotic ceftriaxone reacts with polyethyleneimine in aqueous solutions, probably, with the formation of a noncovalent molecular complex (complex I). The product of hydrolysis of complex I, when heated in an aqueous solution (product II), quenches the fluorescence of CdSe/CdS/ZnS coreshell- shell quantum dots, probably, because of the formation of free thiol groups. A possibility of ceftriaxone determination in aqueous solutions is demonstrated. The performance characteristics of the procedure using a spectrofluorimeter and a photocamera combined with a UV light-emitting diode are close to each other (cmin = 1 × 10–6 M, RSD = 10%). Na+, Ca2+, glucose, urea, uric acid, erythromycin, ciprofloxacin, and doxycycline produce no analytical signals under the conditions of ceftriaxone determination.