Pesticides Determination Based On Colorimetric Method With Nanomaterials And Microfluidic Chip

High detection limit and low sensitivity frequently occurred in the low concentration cases due to small size,little samples,weak detection signal,vulnerable disturbance by external environment,which resulted in many chronic diseases to human so for a long time.Therefore,the colorimetric method based on nanomaterials and high-effective structure of microfluidic chip demonstrated by Comsol simulation were developed from two aspects of nanomaterials and chip structure.In a word,this paper aimed to develop one method with low detection limit and high sensitivity for pesticide determination,which was properly important to food safety.The main contents and conclusions are as follows:?1?This paper built a new colorimetric method based on the CuFe₂O₄/GQDs peroxidase-like nanomaterials.CuFe₂O₄/GQDs were first prepared by modified one-step method and characterized by TEM and XRD,then whose performances were tested including catalytic activity,condition parameters,dynamic performance and linearity.The experimental results showed that CuFe₂O₄/GQDs were successfully prepared by TEM and XRD.Compared with CuFe₂O₄ and GQDs,CuFe₂O₄/GQDs has higher catalytic activity.Additionally,it was found that CuFe₂O₄/GQDs have a higher reactivity to TMB and H₂O₂ than nature enzyme HRP and other nanomaterials by kinetic study.Furthermore,a linear equation for A=0.04449+0.000786783CH₂O₂?C:mM?was built between absorbance and H₂O₂ concentration with a correlation coefficient of 0.98977.The limit of detection is 6.7×10-4 M.?2?This paper studied the relationship between the structure of microfluidic chip and the efficiency of micromixing and chemical reaction.For micromixers: three kinds of micromixers were respectively designed with the inner rib,dividion-combination and composite structures based on the principle of microfluidic tensile,compression,folding and dividion-combination etc.It was shown that the composite structure of “rectangle-circle” possessed the optimal micromixing performance with the inner rib depth of 550 mm and the circle diameter of 400 mm by Comsol simulation.Compared with the structures of rectangle inner rib and circledividion-combination,the micromixing quality factor of the composite structure of“rectangle-circle” was increased by 17.12% and 39.48% respectively.Additionally,test of comparison of the three micromixers confirmed the micromixing effect of“rectangle-circle” as well as.For the whole chip: two structures of the whole microfluidic chip was designed for pesticides determination according to different response strategies.Experimental results displayed that the detection time consumption of “umbrella” structure was reduced by 17.65% comparing the “ fish scale” structure.However,reaction efficiency of the latter was increased by 20.93%.Take everything into consideration,the “fish scale” microfluidic chip with“rectangle-circle” composite micromixers was choosed for further study.?3?The biosensor platform was built for performance analysis and pesticides determination.Firstly,several main condition parameters should be optimized before doing experiment.Sencondly,detection performance of this method was tested such as linearity,sensitivity,detection limit and so on.Thirdly,practicability of this method was tested for actual sample.Experimental results presented that a good linear relationship from 2.0×10-8⁶.0×10-7 M between absorbance values and chlorpyrifos pesticide concentration.The linear equation was A = 0.61822-0.000855261CChlorpyrifos?C:nM?with the correlation coefficient R2 of 0.99758.The detection limit of this method was 1.01×10-8 M,and the detection sensitivity was 855.261 a.u.mM-1 with good selectivity.Additionally,the standard addition recovery rate for pesticides in tomato,pear,and river was ranging from 91.2%¹15%,which displayed good practical performance for actual sample determation.