Highly selective sensing of organophosphate pesticides based on a Dual-Detection 3D Paper-Based microfwluidic platform

A dual detection platform including colorimetry and LDI-MS was implemented with a 3D paper-based analytical device (PAD) for highly selective and sensitive detection of organophosphates (OPs). The colorimetric approach based on the inhibition assay of acetylcholinesterase (AChE) activity by OPs was employed for preliminary testing/screening of the presence of OPs and performing quantitative analysis of total OPs. Limit of detections (LODs) from colorimetric assay were 0.006 and 0.01 mg L−1 for dichlorvos and paraoxon, respectively, which were sufficient to monitor the OPs at the maximum residues levels (MRLs). However, LDI-MS as a complementary detection technique was further exploited to differentiate the type of OPs and quantify the amount of individual OPs at trace concentrations. With LDI-MS, the detection sensitivity was enhanced with extremely low LODs of 5 µg/L for both dichlorvos and paraoxon. This dual detection platform has shown its performance for determination of dichlorvos and paraoxon in cabbage, broccoli and grape with satisfied accuracy and precision.