Evaluation of Improvised and Eco-Friendly Natural pH-Paper Indicators

Abstract

A substance that changes color when pH changes is referred to as an indicator. Synthetic indicators, which are expensive and toxic, are currently the best option for estimating acid-base concentrations or hydronium and hydroxide ion concentrations. This study aims to prepare pH paper indicators from natural sources to overcome this problem. Indicator strips of this type are eco-friendly, cheap, durable, non-toxic, biodegradable, and easy to prepare even at home. In this application, we are using natural sources such as turmeric (Curcuma longa), rose (Rosa Indica), beetroot (Beta vulgaris), and red cabbage (Brassica oleracea) for the preparation of pH paper indicator strips. We used 73 acids, bases, and neutrals solutions to conduct comparative studies. These include fifty-nine household chemicals, such as milk, lemon, mango, honey, glycine, etc., and fourteen standard solutions of acids and bases of pH from 1 to 14. By dipping yellow-colored turmeric acidic paper into sodium hydroxide, we transform yellow-colored turmeric acidic paper into red-colored turmeric basic paper. The results are the same in both cases, i.e., turns yellow in acids and red in bases but unaffected in neutrals. Rose paper easily differentiates acids and bases while red cabbage gives almost the same results as pH paper (wide color change from red to dark blue). As these can be easily prepared and give comparable results with commonly used paper indicators, it would be possible to replace synthetic paper indicators.