Construction of a ratio fluorescence assay of 5-aminosalicylic acid based on its aggregation induced emission with blue emitting N/P-codoped carbon dots

Herein, a novel ratio fluorescence method based on N/P-doped carbon dots (NPCDs) for detecting 5-aminosalicylic acid (5-ASA) in mesalazine enteric coated tablets and blood were reported for the first time. NPCDs were successfully prepared through a simple one-step hydrothermal strategy by employing adenosine triphosphate (ATP) and p-toluidine as raw materials. NPCDs exhibit bright blue emissions with excitation/emission peaks at 340/423 nm with moderate quantum yield (20.75%). In addition, 5-ASA has a certain weak fluorescence emission peak at 487 nm. Adding 5-ASA into NPCDs significantly enhanced the fluorescence intensity, which may result from aggregation induced emission (AIE) of 5-ASA on the surface of NPCDs. Therefore, NPCDs only provide self-calibration signals, and their fluorescence remains almost unchanged when co-existing with 5-ASA. Therefore, the ratio of fluorescence at F-487/F-423 was used for detection of 5-ASA. For the fluorometric determination assay, there was a good linear relationship between F-487/F-423 and 5-ASA concentration between 0.50 and 130 mu M (R-2 = 0.9979). The detection limit was about 0.13 mu M. Therefore, this method is simple, sensitive and low cost, and will be successfully applied to the detection of 5-ASA in drugs.

Automated summary

A novel ratio fluorescence method based on NPCDs for detecting 5-ASA in drugs was reported, showing simplicity, sensitivity, and low cost. The method relies on the measurement of F-487/F-423 fluorescence ratio for quantifying 5-ASA concentration, with a good linear relationship and low detection limit.