Enhancement of sensitivity of paper-based sensor array for the identification of heavy-metal ions

•Enrichment was introduced to enhance the sensitivity of paper-based sensor array.•8 pyridylazo indicators provide facile identification of the heavy-metal ions.•The immobilization of pyridylazo indicators was performed using polymer.•Array technologies and pattern-recognition were combined.

Paper-based microfluidic devices have been widely investigated in recent years. Among various detection techniques, colorimetric method plays a very important role in paper-based microfluidic devices. The limitation, however, is also clear: they generally require highly sensitive indicators. In this work, we have developed a novel enrichment-based paper test for the discrimination of heavy-metal ions. Comparing to regular paper-based microfluidic devices, enrichment-based technique showed largely improved sensitivity. Combining with eight pyridylazo compounds and array technologies-based pattern-recognition, we have obtained the discrimination capability of eight different heavy-metal ions at same concentration as low as 50 μM using our enrichment-based pyridylazo compounds array paper. Identification of the heavy-metal ions was readily achieved using a standard chemometric approach. This method can be, of course, used for other analytes as well.

Graphical abstractAn enrichment-based sensor array paper was developed for the sensitive discrimination of eight 5 heavy-metal ions at same concentration as low as 50 μm. The color changes in array paper 6 provide facile identification of these heavy-metal ions with no misclassification.Figure optionsDownload full-size imageDownload as PowerPoint slide