A simple ninhydrin method is one of several existing methods for quantifying protein levels samples. Ninhydrin reacts with the amine functional group of free amino acids to form a purple-colored complex called Ruhemann's purple, which can be detected by a colorimeter or bare eyes. In recent years, paper-based devices have been developed at low cost and consumption of reagents. Here, a paper analytical device (PAD) was created using a laser engraver to accommodate the ninhydrin reaction on the hydrophilic regions of a cellulose paper substrate. After the color formation, a cell phone or scanner was used to take an image of the PAD. Digital analysis software, such as imageJ or MicrosoftPaint, was used to analyze the intensity of the color formation. In this study, two naturally occurring polymers, chitosan and alginate, were functionalized to the paper and tested for their ability to enhance the sensitivity of the colorimetric assay. Various amino acids were used as standards (Glu, Phe, Tyr, Trp). The calibration graphs, stability, and ease of standardization were compared between these amino acids. The paper assay ninhydrin-based method was applied for determination of protein content in various samples, including amino acids supplements and tea.

Paper assay for ninhydrin-based quantitative determination of amino acids

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.