On-site Chip-based Colorimetric Quantitation Of Organophosphorus Pestcides Using An Office Scanner

In the21st century, food safety, especially the organophosphorus (OP)pesticide residues in fruits and vegetables, has attracted much moreattention. Since the OP pesticide residues would damage human bodythrough direct or indirect ways, the detection of OP pesticide residues isparticularly important. The enzyme inhibition method has been a fast wayto detect OP pesticide residues because of its simple operation, quickresponse. Based on this enzyme inhibition method, herein we report ascanner-readable plastic microchip for the colorimetric quantitation of OPpesticides in food products with the help of digital image analysis software.Comparing with the traditional sophisticated instruments to detect OPpesticide residues, the simplicity of the device fabrication and operation ofthis colorimetric protocol avoids many faults, such as complex andlong-time operation, expensive instrument charge and professional peoplerequirement. The new method can also replace spectrometer for thedetection of OP pesticide residues. The main research contents include: 1. We have fabricated a simple plastic microchip consisting of atransparent polydimethylsiloxane (PDMS) plate with embeddedmicro-channels (for the colorimetric reaction) attached to apolycarbonate (PC) base plate.2. Image quality and colorimetric detection accuracy has been comparedamong the smartphone, camera and flatbed scanner. The standardflatbed scanner was used to image the colorimetric reaction at real timefor its illuminant uniformity.3. A commercial photo editing software to read the different color values.We have found that yellow intensity (color intensity from the colorspace CMYK (cyan, magenta, yellow, black)) of the capturedimageshas the highest sensitivity. By analyzing the yellow intensity ofthe OP pesticides’ solution, we have found the detection limit for thetrail OP pesticides (e.g., malathion) was determined to be0.1ppm,which is below the food safety limits2ppm.4. We have compared colorimetric analysis with conventionalspectroscopic analysis for the detection of OP pesticides. Both theresults have come to an agreement significantly.