Using Gold Nanoparticles for Ultra-trace Spectrophotometric Determination of Sitagliptin Drug in Various Real Samples

Background: The determination of trace drugs in aquatic environments is important. For this purpose, many methods such as High Performance Liquid Chromatography (HPLC) and gas chromatography mass spectrometry (GC/MS) have been used. Objective: This study introduces a simple, sensitive, and rapid colorimetric method for the spectrophotometric determination of sitagliptin (STG) in drinking water, tablet, human plasma, and human urine using gold nanoparticles (AuNPs). Methods: The Surface Plasmon Resonance (SPR) property of AuNPs and the interaction between STG and AuNPs are the base of the colorimetric method. The addition of STG into AuNPs led to the aggregation of AuNPs. Transmission Electron Microscopy (TEM) proved the aggregation of AuNPs in the presence of STG. Also, the size of the nanoparticles distribution was evaluated by Dynamic Light Scattering (DLS). In addition, Fourier-Transform Infrared Spectrophotometer (FTIR) was used to study the chemical structure of AuNPs, STG, and AuNPs in the presence of STG. Results: The parameters that affect the absorbance such as pH, type and volume of buffer, AuNPs concentration, interaction time, ionic strength, and interfering ions were investigated and optimized. Under the optimum conditions, the determination of STG was performed via this method over the range of 50-300 μgL^-1 (R²=0.9941) with the Limit of Detection (LOD) and Limit of Quantification (LOQ) of 1.23 and 1.39 μgL^-1, respectively. Conclusion: Eventually, the results showed that the proposed method has a high potential for simple, rapid, sensitive, and accurate determination of STG.