Smartphone Nanocolorimetry for On-Demand Lead Detection and Quantitation in Drinking Water

Abstract

Lead ions (Pb) contamination in drinking water, a major source of lead poisoning to the general population, is typically detected by bulky and costly laboratory analytical instrument. A mobile analytical device for rapid Pb sensing is a growing demand. Herein, we report smartphone nanocolorimetry (SNC) as a new technique to detect and quantify dissolved Pb in drinking water. Specifically, we have employed a single-step sedimentation approach by mixing a controlled quantity of chromate ion (CrO) to react with Pb containing solutions to form highly insoluble lead chromate (PbCrO) nanoparticles as vivid yellow precipitates. This is followed by microscopic color detection and intensity quantitation at nanoscale level using dark-field smartphone microscopy. The sum of the intensity of yellow pixels bears a highly reproducible relationship with Pb concentration between 1.37 and 175 ppb in deionized water and 5-175 ppb in city tap water. In contrast to traditional colorimetric techniques analyzing bulk color changes, SNC achieves unparalleled sensitivity by combining nanocolorimetry with dark-field microscopy and mobilized the metal ions detection by integrating the detection into the smartphone microscope platform. SNC is rapid and low-cost and has the potential to enable individual citizens to examine Pb content in drinking water on-demand in virtually any environmental setting.

Highly-Efficient Sulfonated UiO-66(Zr) Optical Fiber for Rapid Detection of Trace Levels of Pb2+

“…As yet, there are considerable efforts to develop sensors to allow discrete measurements of lead contents at-the-source for home-users. The existing detection mechanisms are based on colorimetry [ 22 , 23 ], biosensing [ 24 ], and electrochemical configurations [ 25 ], which, in addition to their low detection limits, have many other constraints. For instance, matrix interferences in the colorimetric method either disrupt the reaction between the reagent and the analyte or interfere the spectrometric light measurement [ 21 ].…”

Rapid Antibody Selection Using Surface Plasmon Resonance for High-Speed and Sensitive Hazelnut Lateral Flow Prototypes

“…An alternative, more consumer-orientated method is to use smartphone apps to determine RGB/CMYK values of the test line region of the LFIAs and to convert these to LAB (where L is Luminance and A and B are color channels) values. Whilst RGB (red, green, blue) and CMYK (cyan, magenta, yellow, key) values are device dependent, LAB values provide device independent information about the darkness/lightness of a selected region of an image [23]. In this way a calibration curve of LAB color values against allergen concentration (ppm) can be plotted for semi-quantification of LFIA results.…”

Smartphone colorimetric assay of acid phosphatase based on a controlled iodine-mediated etching of gold nanorods

“…However, they still have limitations, especially in practical applications; for example, in most cases, the need for bulky instrumentation and trained personnel is not suited to point-of-care testing. The smartphone has recently emerged as a novel and efficient sensing platform for medical diagnosis and environmental monitoring [23][24][25][26][27][28] by means of its powerful image capture and processing and its advanced computing capabilities. Smartphone-based colorimetry [29][30][31][32], with the aid of a smartphone camera and color picker software, has been shown to be a simple, rapid, portable, and affordable on-site detection method, without the use of sophisticated instruments.…”