A Combined System of Paper Device and Portable Spectrometer for the Detection of Pesticide Residues

Pesticide residues are detected in food items globally at levels that may cause health problems. Paper-based analytical devices have emerged as an alternative low-cost and field-based tools for determining target analytes including the pesticide residues. However, the paper devices with colorimetric detection system are limited by lower sensitivity due to their inability to record wavelength specific signal from the assays when image analysis detection method is used. In this paper, we report a low-cost analytical method that combines paper-analytical platform with a do-it-yourself desktop spectrometer to determine pesticide residues in vegetables and fruits. The pesticide determination method utilizes acetylcholinesterase enzyme inhibition assay on paper platform for signal generation. The signal of the assay was then measured using a spectrometer made from locally available components. The enzyme reaction parameters were optimized using multivariate optimization methodology to obtain better assay signal. The average repeatability of the assay method was 5.7% RSD. The combined method responded to the concentration of dichlorvos pesticide with a linear range from 0.01 to 0.25 mg/kg and detection limit of 0.023 mg/kg using only 4 mu L of reagents and sample. As the enzyme inhibition assay used in this work is not able to discriminate individual pesticides, it can be used as a low-cost method for initial screening of pesticide residues in food samples in field settings.