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Heavy metal ions released into various water systems have a severe impact on the environment and human beings, and excess exposure to toxic metal ions through drinking water poses high risks to human health and causes life-threatening diseases. Thus, there is high demand for the development of a rapid, low-cost, and sensitive method for detection of metal ions in water. We present a portable analytical system for colorimetric detection of lead (Pb 2þ ) and aluminum (Al 3þ ) ions in water based on gold nanoparticle probes and lab-on-a-chip instrumentation. The colorimetric detection of metal ions is conducted via single-step assays with low limits of detection (LODs) and high selectivity. We design a custom-made microwell plate and a handheld colorimetric reader for implementing the assays and quantifying the signal readout. The calibration experiments demonstrate that this portable system provides LODs of 30 ppb for Pb 2þ and 89 ppb for Al 3þ , both comparable to bench-top analytical spectrometers. It promises an effective platform for metal ion analysis in a more economical and convenient way, which is particularly useful for water quality monitoring in field and resource-poor settings.

A sensitive colourimetric method for lead (Pb II ) detection is reported in this paper using a common tripeptide, glutathione (GSH), and label-free gold nanoparticles (AuNPs). A limit of detection of 6.0 ppb in water was achieved and the dynamic linear range was up to 500 ppb. Selectivity over fourteen potential interfering metal ions was tested and most of these metal ions do not interfere with the method.

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