Ultra-trace Cadmium Ion Detection Technology Based On Microfluidic Enrichment Effect

At present,with the increasing demand of industrial production,a large number of cadmium-containing wastes are discharged into the environment in the form of smoke,slag and waste water,which has gradually become one of the"public hazards"affecting human health.Cadmium is a highly toxic heavy metal pollutant,which has strong bioaccumulation and long half-life.Excessive exposure to cadmium will cause irreversible harm to human kidney,cardiovascular systems,lung and immune systems.Therefore,sensitive and specific detection of ultra-trace cadmium is of great significance in food safety and environmental monitoring.In order to solve a series of problems existing in the current detection technology of heavy metal cadmium ion(Cd²⁺),including low detection accuracy,poor selectivity,and the inability to meet the requirements of fast and real-time detection.In this paper,a simple-to-use aptasensor to rapidly detect Cd²⁺in various liquid media is developed based on a DNA aptamer modified gold interdigitated electrode（IDE）.Capacitance at the solid-liquid interface is utilized to reflect the change caused by adsorbed Cd²⁺.With the microfluidic enrichment by AC electrokinetic effect,Cd²⁺are sped up toward the IDE surface and captured by the aptamer probes instantaneously during the detection process.Owing to the integration of target enrichment and capacitance detection,the sample-to-result time of this sensor is as short as 30s.As a quantitative detector,the linear response range of the aptamer sensor is from 0.45f M to 4.5p M,and the detection limit is 253.16a M.In addition,its selectivity ratio reaches 2320:1 against non-target metal ions.Considering that cadmium enters the organism through various ways in real life.By detection of Cd²⁺spiked in tap water and olive oil as well as natural residual Cd²⁺in rice leaching solution,the sensor’s applicability and reliability in different practical liquid media are demonstrated.Finally,the sensor was placed in different environments（room temperature/24℃and refrigerator/5℃）for stability and long-term effectiveness research.The experimental results confirmed that the aptasensor has extremely high stability when detecting low-concentration target Cd²⁺,and it still has good properties after being stored at room temperature for a week.