1．IntroductionAlong with the continuous development of mineral resources, the arbitrary discharge of waste rock and tailings is prone to cause siltation of the river, in which heavy metals such as Cd2+ and Pb2+ pollute surface water, groundwater and the surrounding environment. 1-3. Heavy metal ions (HMIs) are considered to be a serious source of pollution to the global environmental ecosystem due to their accumulation and non-degradable nature in living organisms, causing many biological health and physiological disorders. Although heavy metal ions are present in trace amounts in the natural environment, they accumulate through transport and peak when absorbed by humans4-6. Many authors have investigated electrochemical-based detection of various heavy metal ions, as in most cases this method can be used for in situ measurements and high sensitivity can be achieved in a short time 7. Differential pulse dissolution voltammetry (DPSV) for the accurate detection of Cd2+ and Pb2+ in the environment faces significant challenges due to poor immunity to electrochemical interactions between multiple heavy metal ions (HMI)8-9. In order to improve detection accuracy, a solution to mitigate interference is necessary. In addition, despite the low detection limits and high sensitivity of electrochemical methods, all measurements are confined to the laboratory and operation requires skilled technicians 10.Microfluidic chips and electrochemical analysis techniques can be assembled into small portable devices that can be easily implemented for field testing11-12. Secondly, the microfluidics can be integrated into mobile applications for use via mobile phones or laptops. In addition, the chip is relatively inexpensive to manufacture13. A microfluidic chip laboratory platform for heavy metal pre-enrichment and detection was proposed by Andrzej et al. This is a design feature that allows multiple uses for the detection of lead ions, but with a more complex chip structure14. For rapid detection in the field, Zhou et al. designed an electrochemical paper-based sensing device that is easy to use, simple to operate and provides better detection of cadmium ions, but stability needs to be improved15.The presence of dissolved organic matter (DOM) in the aqueous environment has been found to interfere with the sensitivity of detection. Dissolved organic matter (DOM) is widely present in natural water bodies such as lakes, rivers (estuaries) and oceans, with a particle size of less than 0.45 μm, a complex structure and a heterogeneous mixture of dissolved organic components16-17. The presence of DOM adsorbs heavy metal ions, and the smaller the molecular weight of DOM, the better the adsorption of heavy metal ions. For example, the xanthate component of DOM has a stronger affinity for metal ions and the hydrophilic protein small molecule component of DOM preferentially complexes with it. As a result, the results are somewhat compromised during the electrochemical assay18-19. Although it has been shown that heavy metal measurements can be performed in the presence of xanthic acid (FA), the presence of FA results in higher peak currents and a more pronounced detection trend. However, there are limitations to this approach and the composition of DOM in natural waters is both complex and different20. Due to the economical and environmentally friendly nature of membrane separation technology, it is widely used for the separation or extraction of substances in a variety of aqueous environments21-23. Of these, ion exchange membranes (IEMs) have a more prominent application in ion separations and are often used in electrodialysis processes24-26. The fundamental feature of cation exchange membranes is the selective permeation of cations through the membrane, resulting in separation. The effective separation of ions can now be achieved by techniques such as electrodialysis and electrodeionisation.The effectiveness of electrochemical detection is highly dependent on the performance of the working electrode, and chemical modification of the working electrode using electron media can improve the selectivity and sensitivity of the sensor to ensure site-specific identification of the target analyte. Nanomaterials have been extensively investigated in the field of electrochemical sensing due to their large specific surface area and good quantum mechanical properties27. Moreover, they offer opportunities for miniaturisation of sensors and further advance the development of lab-on-a-chip applications5, 28. The use of multi-walled carbon nanotubes (MWCNT) and Nafion composite membranes (MWCNT/Nafion) to cover and modify screen-printed electrodes was investigated to further improve the performance of on-chip electrochemical sensors. The ion-exchange membrane effectively avoids contact between dissolved organic matter and the electrode, reducing the interference of natural water constituents with the test and significantly improving accuracy. A phase equilibrium resistance characteristic is formed between the microchannel and the detection electrode, and the optimum value is calculated to provide the design with the optimum sensor response current on the microscale. The design of the membrane based microfluidic coupling chip combines pre-treatment and detection in a single reactor, essentially synchronising the two and allowing significant miniaturisation of the device for fast and accurate detection.