UV photometric assays on paper-based analytical devices by contact printing photography through transparent cellophane

Abstract

A limitation of paper-based devices that employ optical readout is that they can only be used for assays in the visible range of the electromagnetic spectrum. This work describes the first paper-based analytical devices that can be used for UV absorption photometric assays without scientific equipment. The devices consist of a transparent cellulose film (cellophane) as a reaction vessel and photometric cuvette and a photosensitive paper as a detector of UV irradiation. The analytes or their derivatives absorb part of the incident UV irradiation on the cellophane surface while the transmitted irradiation passes through the cellophane and photoreduces the surface of the photosensitive paper, producing an image. In this manner, the “colorimetrically invisible” UV absorption signaling is transformed into a visible image that can be captured and processed with common imaging devices. The analytical utility of these devices is demonstrated, as a proof-of-concept, for six UV-absorption model assays. The results show that cellophane-analytical devices are suitable for high-sensitivity measurements but exhibit a relatively large standard deviation, dictating multiple trials to correct the accuracy of the results. Technical aspects related to the improvement of the devices and the quality of analytical data are elucidated and discussed.