Determination of norfloxacin or ciprofloxacin by carbon dots fluorescence enhancement using magnetic nanoparticles as adsorbent

The authors describe a method for the determination of norfloxacin (NOR) or ciprofloxacin (CIP). It is making use of a combination of fluorescence enhancement and magnetic solid-phase extraction (MSPE). Sulfur-doped carbon dots (S-CDs) are used as a fluorescent probe. They were prepared by a one-pot method using poly(4-styrenesulfonic acid-co-maleic acid) (PSMA) as a source for carbon and sulfur. NOR or CIP act as sensitizers of fluorescence (with excitation/emission maxima at 324/412 nm), probably due to strong hydrogen bond interaction and charge transfer with the S-CDs. The S-CDs were characterized by using TEM, XRD, XPS, FT-IR, UV-Vis and fluorescence spectroscopies. Response is linear in the 0.02-1.25 mu MNOR concentration range, and the detection limit is 4.6 nM. The respective data for CIP are 0.02-1.0 mu M and 6.7 nM. The average recoveries of NOR and CIP residues from spiked bovine raw milk are 96.2%similar to 105.2% and 92.3%similar to 102.5%.