A sensitive “turn-on” fluorescent assay for quantification of ceftriaxone based on l-tryptophan-Pd(II) complex fluorophore

Based on l -tryptophan-Pd(II) system, a sensitive and selective fluorimetric assay for the quantification of ceftriaxone (CTRX) had been developed. The experimental results showed that in pH 4.0 Britton–Robinson (BR) buffer medium, the fluorescence of l -tryptophan ( l -Trp) ( λ ex / λ em   =   276   nm/352   nm) could be efficiently quenched by Pd(II). When CTRX was added to the mixed solution of the l -tryptophan and Pd(II), the fluorescence of l -Trp recovered. The reaction mechanism and the reasons for the fluorescence recovery were also discussed. Pd(II) reacted with l -Trp to form a 1:1 chelate complex, and then, after CTRX was added in l -Try-Pd(II) system, the ligand exchange reaction occurred between l -Trp and CTRX, which resulted in the fluorescence recovery. Under the optimized experimental conditions, the recovered fluorescence intensities at 352   nm showed excellent linear relationship with the concentration of CTRX over the range of 6.0   ×   10 −   8 –2.4   ×   10 − 6   mol   L −   1 (0.040–1.59   μg   mL −   1 ). The correlation coefficient (R) was 0.9997 and the detection limit was 1.8   ×   10 − 8   mol   L −   1 (11.9   ng   mL −   1 ). Furthermore, the assay had been applied to determine trace amount of CTRX human urine samples with satisfactory results.