Portable colorimetric detection of copper ion in drinking water via red beet pigment and smartphone

The concentration of copper ion (Cu2+) in drinking water is closely related to the water quality and human health. Therefore, it is necessary to develop a novel, efficient and selective method for the detection of Cu2+ in drinking water. In this work, natural food pigment—red beet pigment was selected as a colorimetric indicator for the detection of Cu2+, which possessed a bright color, excellent water solubility and safety. Under alkaline condition, red beet pigment reacted selectively with Cu2+ by redox reaction and chelation, resulting in a color change from purple to orange-red. After analyzing the blue (B) value of the red beet pigment solution, it could be found that there was a good linear relationship between B value and the concentration of Cu2+ in the range of 4–20 μM, with a detection limit of 0.84 μM. In addition, a smart phone application based on Android system was developed for visual detection of Cu2+ by identifying B value of the colorimetric probe solution. The feasibility of this method was successfully verified in the detection of Cu2+ in drinking water by the standard-addition method, reflecting its great potential of practical application in environment monitoring and food security controlling. The method provides a new insight for rapid detection of heavy metal ions using nature pigments. [Display omitted] •A red beet pigment-based colorimetric probe for copper ions was developed.•The possible mechanism was oxidative dehydrogenation reaction and chelation effect.•A colorimetric analysis application was built on smartphone with Android system.•It provides a great potential for on-site detection of copper ions in drinking water.