Flow injection analysis in lab-on-paper format

Analytical applications of paper-based microfluidic devices, receive much attention and have been heavily investigated in the last few years. Liquid movement in the body of the paper brings the idea of paper-based flow injection analysis (FIA) developed according to lab-on-paper (LOP) concept. In this approach, paper patterned with hydrophobic borders playing the role of channels in FIA system. The channel is connected from one side with an unlimited source of the liquid carrier and from the other side with sorbent pad, which ensures constant and a continued flow of fluid along the channel. Microliter volumes of standards, consecutively placed directly on the paper surface are moving towards detection zone. The developed prototype of LOP-FIA system was tested with the dedicated optoelectronic detector, compatible with a model analyte (bromothymol blue) as well as with Prussian Blue based chemosensitive layer deposited inside a paper channel, playing the role of the prototype of the flow-through optical sensor integrated with LOP. The effects of sorbent/channel type, distance between injection and detection zone and sample volume on the shape of the analytical signal were investigated. Results obtained for sequential sample introduction show satisfactory reproducibility, confirming that paper-based microfluidic FIA without conventional tubing, pumps and valves, exploring merits of LOP concept only, is possible.