Stamping method based on 3D printing and disposable napkin: Cheap production of paper analytical devices for alcohol determination in beverages aiming forensics and food control

Abstract

In this work we report for the first time the use of napkin paper as substrate for production of paper analytical devices (PADs). Napkin paper is a more accessible and cheaper option compared to the most commonly used chromatographic and filter papers. The PADs were easily fabricated by depositing hydrophobic paraffin barriers using a simple stamping contact method. The stamps used here were fabricated by 3D printing. To the best of our knowledge, this is the first report of this stamping approach aiming production of paraffin barriers in PADs. The PADs proposed here were utilized for colorimetric determination of alcohol content in beverages. This method was based on the redox reaction between ethanol and dichromate in acidic medium. As far as we know, this is the first PAD-based method exploring this principle. The image-based method showed a linear range between 0 and 50 % (v/v) ethanol, with a limit of detection of 1.5 %. This concentration range allows the analysis of various alcoholic beverages. The results obtained during the analysis of real samples presented great concordance with the values found by UV–vis spectrophotometry, used for validation (relative error < 5 %). Thus, the new PAD-based colorimetric method reported here shows great potential for applications in areas such as food control and forensics. Moreover, the use of napkin paper for fabrication of PADs appears to be a promising, easier and less expensive option, being specially interesting for places with limited resources.