Multimodal Voltammetric sensor using Pd@ErGO nanocomposite for selective or simultaneous determination of Tetrandrine and Fangchinoline in traditional Chinese medicine and biological matrices

In this work, a sensitive glassy carbon electrode modified with palladium-doped electrochemically reduced graphene oxide (Pd@ErGO/GCE) was developed for the selective and simultaneous determination of tetrandrine (TET) and fangchinoline (FAN). The electrochemical behavior was investigated by cyclic voltammetry (CV) and a multimodal voltammetric platform was established: (1) differential pulse voltammetric (DPV) quantification of TET (LOD = 55 nM), (2) linear sweep voltametric (LSV) determination of total content (LOD = 45 nM), and (3) simultaneous determination of both analytes via DPV. The methods have great reproducibility and repeatability, great interference tolerance, and satisfactory accuracy in serum (recovery: 95.7% ~ 104%) and urine (97.4% ~ 103%). Comprehensive validation against HPLC-UV ( t = 0.32) confirmed method accuracy for pharmaceutical quality control in Radix Stephaniae tetrandrae. This methodology offers a reliable framework for alkaloid monitoring in herbal and biological matrices. • Pd@ErGO/GCE enables multimodal detection of TET and FAN • Low detection limits of 15 nM (TET) and 34 nM (FAN) were achieved • High discriminatory power against the structural analog magnoflorine • Retention >90% after 12-day storage confirms robust stability • Successful application in serum, urine, and herbal medicine samples