Coordination Colorimetric Array And Paper-based Microfluidics Sensing Of Four Heavy Metal Ions

With the development of industry and the activity of human,a large amount of sewage and wastewater containing heavy metals are discharged into the environment,causing serious pollution to source of water.Heavy metal pollution is usually in a wide range and not easy detected early,and it will gradually accumulate in the human body through the food chain and cause harm.The colorimetric array is a method of rapid analysis,which simulates the smell sense of animals.Compared with specific recognition,it uses the pattern response of multiple sensing elements to distinguish different targets.Array is also a powerful technique for sensing analytes in mixtures and for multiple targets especially for food samples.However,the current colorimetric arrays with better effects still have problems such as synthetic materials are required,the sensing process is complex and the signal is hard to access.Coordination reagent has advantages of simple and easy to obtain,and the combination of heavy metal ions will be accompanied by color changes,rapid response and obvious signals,etc.,which can well solve the current problems of colorimetric array.Therefore,coordination reagent is strictly selected with condition which can be complexed with multiple target ions with color change,and the conditional stability constant is small.Then take coordination reagent as elements of colorimetric array to sense Cd²⁺,Cu²⁺,Hg²⁺and Pb²⁺in the aqueous solution combined with chemometrics.The main research contents are as follows:(1)Developed a coordination colorimetric array to sense four heavy metal ions.The reagents were bathocuproine(BCP),thiomichler's ketone(TMK),cadion(CDI),diphenyl carbazide(DPC),xylenol orange(XO)and victoria blue B(VBB).By screening coordination reagents,and optimizing the conditions and masking agents,a coordination colorimetric sensor array was formed.By scanning the spectrum in the visible light region,using spectral response combined with linear discriminant analysis(LDA)to distinguish single heavy metal ion,and the verification accuracy reached 100%,and the limit of detection was 1?mol/L.The accuracy of discrimination for mixed ions reached 93.3%,and the selectivity and detection limit of the array were further analyzed.Furthermore,the discrimination of Cd²⁺,Cu²⁺,Hg²⁺and Pb²⁺by the array in the actual water sample was explored.Through the reaction with common anions,metal ions and organic pollutants in water,it is found that the coordination array has good anti-interference property.The discrimination of Cd²⁺,Cu²⁺,Hg²⁺and Pb²⁺in lake water and tap water by the coordination colorimetric array was investigated.The accuracy of the method reached 94.4%and 100%,respectively,which proved the potential of the method in practical application.(2)Developed a microfluidic paper-based coordination colorimetric array to sense four heavy metal ions.The wax stamping method was used to form the hydrophilic channel and hydrophobic area on the paper.The coordination array developed in the first part of this paper was pre-embedded in the detection area of microfluidic paper-based chip,the reagent was screened and optimized,the reagents were BCP,TMK,CDI,DPC,XO and 4-(2-pyridinazo)-1,3-benzodiol(PAR),thus a portable detection platform of microfluidic paper based complexing array was constructed.The image was obtained by smart phone,and the RGB value was read by software.Combined with LDA analysis,the recognition accuracy of single heavy metal ion reached 100%,and the detection limit was 2?mol/L.It also had good ability to distinguish multiple mixed ions.The method is not obvious for common interference ions such as Na⁺,Cl^-,K⁺,SO₄^2-,NO^2-,Fe³⁺,Zn²⁺,Mg²⁺,Ca²⁺,which demonstrate the method has good anti-interference property.The successful identification of Cd²⁺,Cu²⁺,Hg²⁺and Pb²⁺in real water samples proves the potential of paper based microfluidic complex colorimetric array for the accurate detection of various heavy metal ions in the field.The paper based on the coordination reaction to develop two array method for identification heavy metal ions,which is rapid,high sensitivity and selectivity,successfully applied in the actual detection in water samples,and the paper-based detection achieved on site identification Cd²⁺,Cu²⁺,Hg²⁺and Pb²⁺in water samples,so as to provide effective portable sensor platform for heavy metal ions.