Colorimetric Detection of Platinum (IV) Using 4-MethylSulfonylaniline-Modified Gold Nanoparticles in Lanthanum Carbonate API

The control of elemental impurities is a critical step in the preparation of lanthanum carbonate, with platinum being one such impurity. Residual platinum is typically non-therapeutic and must be strictly controlled to ensure both safety and product quality. This paper describes a colorimetric method for determining platinum (IV) in solutions based on the anti-aggregation of gold nanoparticles modified with 4-methylsulfonylaniline (4-MESA). The presence of Britton–Robinson buffer induces the aggregation of the 4-MESA-AuNPs nanoparticle probe. However, when platinum (IV) is introduced, it disrupts the aggregation of the 4-MESA-AuNPs, causing a color change in the solution. The absorbance at 524 nm showed a strong linear correlation in the concentration range of 1.00 × 10−2 μM to 5.00 × 102 μM. Under optimal conditions, LOD and LOQ values of 10.00 × 10−3 μM and 3.03 × 10−2 μM, respectively, were observed. This method has been successfully applied to the determination of platinum (IV) in lanthanum carbonate API.