Capillary-driven microfluidic paper-based analytical devices for lab on a chip screening of explosive residues in soil

• A μPad was developed to extract explosives in soil.
• Explosives extracted from the paper fibers were analysed via Lab on a Chip.
• μPads combined with Lab on a Chip are a fast and simple way to detect explosives.

A novel microfluidic paper-based analytical device (μPAD) was designed to filter, extract, and pre-concentrate explosives from soil for direct analysis by a lab on a chip (LOC) device. The explosives were extracted via immersion of wax-printed μPADs directly into methanol soil suspensions for 10 min, whereby dissolved explosives travelled upwards into the μPAD circular sampling reservoir. A chad was punched from the sampling reservoir and inserted into a LOC well containing the separation buffer for direct analysis, avoiding any further extraction step. Eight target explosives were separated and identified by fluorescence quenching. The minimum detectable amounts for all eight explosives were between 1.4 and 5.6 ng with recoveries ranging from 53–82% from the paper chad, and 12–40% from soil. This method provides a robust and simple extraction method for rapid identification of explosives in complex soil samples.