Sensitive Electrochemical Determination of Creatinine in Human Serum Based on its Complexation with Cobalt Ion

Determining creatinine in human body fluids, based on its complexation with transition metal ions, has been a significant non-enzymatic approach for assessing kidney function. While copper, silver, iron, and aluminium metal ions have frequently been utilized, the coordinating property of creatinine with cobalt ions remains an underexplored avenue in developing a non-enzymatic electrochemical creatinine sensor. This work presents an electrochemical insight into the creatinine-cobalt coordination in the presence of 2-nitrobenzaldehyde. It was found that the addition of creatinine to the Co 2+ -2-nitrobenzaldehyde complex converts the latter to a Co 3+ complex, triggering a voltammetric response. This electrochemical response has been utilized to determine creatinine in deproteinized human serum, under the optimized conditions of 5 min reaction time, 2-nitrobenzaldehyde concentration of 7 weight % and 500 mM cobalt chloride concentration. The system exhibited excellent linearity in the concentration range of 0.050 mM to 0.600 mM, with an R 2 value of 0.99 and an LOD of 0.0095 mM. From comprehensive electrochemical analysis, supported by spectroscopic findings, a plausible reaction mechanism has also been proposed and all the redox peaks have been designated. This novel method exhibits better analytical performances than many contemporary methods and is a promising new tool in clinical practices.