Microreaction Electrochemical Sensors for Highly Selective Detection of Nickel Ions Using Masking and Complexing Technology

Conventional electrochemical methods, improved for selectivity and sensitivity through the application of ion-selective membranes or electrode modifications, were complex to produce and prone to interference from other ions, lacking effective mitigation strategies. Therefore, a simple, accurate, and selective detection method for nickel ions based on a microfluidic electrochemical sensor was developed. The microfluidic electrochemical sensor incorporated a bare carbon electrode. The microfluidic technology was employed to control the sequential mixing of samples, masking agents, and chelating agents, achieving automated sample preprocessing within 1 min, faster than the conventional electrode modification process. The hybrid microchannel was designed to enhance the effectiveness of mixing between the sample and the masking agent, resulting in increasing the masking effect on interfering ions. Based on the high affinity of the masking agent for interfering ions, the interference ions were effectively masked, ensuring that only nickel ions reacted with the complexing agent. Tests using pure nickel solutions revealed that the microfluidic electrochemical sensor possessed excellent properties of linear detection range and resolution. Compared to conventional modified electrodes, the microfluidic electrochemical sensor simplified fabrication, exhibited good reproducibility and repeatability, and achieved higher selectivity. The experiments on anti-interference performance demonstrated that the masking agent effectively shielded against interfering ions, the Bias% after the mask was less than 3%. The practical tests using real water samples proved the effectiveness and suitability of this detection method in specifically identifying heavy metal ions.