Conclusion
The combination of a PAD and LOC for sample preparation and analysis provides a new, fast approach for identification of explosive mixtures in soil. To the best of our knowledge this is the first report where a filter paper device containing the sample has been directly inserted into a microfluidic device for electrokinetic extraction. This approach directly inserting the paper chad into the chip sample wells represents a significantly simplified extraction process. The LOC device does not require any pumps or gas for its operation; this along with its low weight (approximately10 kg), small size and robust nature gives it excellent potential for portable use in mobile laboratories. The current method was optimized for the analysis of eight target explosives that were well separated and visualised using fluorescence quenching. The minimum detectable amounts for all eight explosives were between 1.4 and 5.6 ng with recoveries ranging from 65 to 82% from the paper chad and 12–40% from soil. Sample extraction and preparation maybe performed in approximately 12 min, with up to 12 samples processed by the LOC per hour. This rapid turnaround, the ability to analyze explosive mixtures, and relatively low costs per analysis(currently ∼$4/sample) makes this approach a viable alternative method of explosive screening [