Research On Self-heating Magnetic Composite Paper Chip And High-throughput Detection Device For Detection Of Pesticide Residues In Tea

Tea is often drunk directly after soaking,and the pesticide residues in it are easy to be ingested by the human body and affect health.Enzyme inhibition is the most commonly used method for rapid detection of pesticide residues,covering 90% of the pesticides used in tea plants.However,the current pesticide residue test paper based on the enzyme inhibition method is used with too many manual operations,which is easy to introduce human errors.Moreover,the detection equipment is too large due to the need for external physical heat sources to provide temperature in order to maintain the activity of the enzyme.In addition,the lack of high-throughput pre-automatic elution devices also leads to low pesticide residue detection efficiency.These factors hinder the householdization and convenience of pesticide residue detection equipment.In view of the above problems,firstly,the influence of temperature and reaction time on the enzyme culture link and color reaction link in the enzyme inhibition detection reaction was explored,and the reaction conditions were optimized by taking into account the reaction efficiency and the color effect.Then whether there is any effect of the magnetic field on the result of the enzyme inhibition test was discussed.Based on the above experimental results,a self-heating composite magnetic paper chip that can be used for household pesticide residue detection is designed.Using microfluidic technology,the process of sampling,mixing,and reaction in the enzyme inhibition detection method is integrated on the composite paper-based chip to automatically proceed,reducing human operations;selecting a safe and stable iron powder electric oxidation reaction as the heating principle to design the heating layer And optimize the relevant parameters to ensure the required temperature during the enzyme reaction and simplify the physical heat source.However,the reagent mixing and colored substance precipitation process of the composite paper chip only relies on gravity and channel morphology,and there are often problems of insufficient mixing and unstable color rendering results.In this project,the magnetic reaction channel is designed and the main channel parameters are optimized,adding magnetic force to promote the mixing of reagents and enhance the color rendering effect.After that,the repeatability of the paper chip and the influence of different environmental temperatures on the detection results were analyzed experimentally,and the gray-scale difference compensation parameters under different environmental temperatures were established.In addition,in order to improve the detection efficiency of large quantities of tea samples,a high-throughput elution detection integrated pesticide residue detection device used with paper chips was designed.According to the small size of tea leaves,most of the pesticide residues that are easily ingested are distributed on the surface,a pre-soaking and elution mechanism integrating elution and sampling is designed;a multi-channel rotating flat plate mechanism is designed to integrate multiple elution injections The reaction unit meets the demand for high-efficiency detection of pesticide residues in tea;the image data is collected by the camera module and processed by the image to determine whether the pesticide residue in the sample exceeds the standard.Taking the gray-scale difference between the test sample and the blank control as the test result in the range of0.5～2.5μg/m L,the test results for chlorpyrifos and trichlorfon are y = 16.69 x + 4.52 and y = 18.4x + 8.72,respectively.The combined curve R2 is 0.8743 and 0.9512,respectively,the detection limit is 0.5μg/m L,the pesticide residue concentration thresholds for judging whether it exceeds the standard are 1.80 and 1.43μg/m L,respectively,and the recovery rates of addition are 91.9%～107% and 91.5%～ 106%,the relative standard deviation RSD is 1.25% and 3.0%.The detection limits are lower than the maximum residues in tea samples specified in the national standards,which can meet the requirements for semiquantitative detection of pesticide residues in tea,and the detection device also has good detection accuracy.