Researchers from the University of Houston have created an inexpensive way of detecting dangerous levels of lead in tap water below the safety threshold set by the Environmental Protection Agency. System uses a microscope system integrated on smartphone and a lens made with an inkjet printer. This discovery combines nano-colorimetry with dark-field microscopy. Smartphone nano-colorimetry is rapid, not expensive and could allow individual citizens to test drinking water for heavy metals presence, in this case lead in virtually any environmental setting. Lead is very dangerous heavy metal, especially for young children, which are more vulnerable to neurological damage than adults.

Researchers built a self-contained smartphone microscope that can operate in both fluorescence and dark-field imaging modes. Credit: University of Houston

Aforementioned solution is both portable and easy to operate thanks to inexpensive smartphone equipped with an inkjet-printed lens and using the dark-field imaging mode.

Last year, the same researchers have also explained in their publication how to convert a smartphone equipped with the elastomer lens into a microscope capable of fluorescence microscopy. The latest application incorporates color analysis to detect nanoscale lead particles.

They’ve contaminated tap water sample with varying amounts of lead, ranging from 1.37 parts per billion to 175 parts per billion. Then they’ve added chromate ions, which react with the lead to form lead chromate nanoparticles, which can be detected by combining colorimetric analysis and microscopy. The analysis measured both the intensity detected from the nanoparticles, correlating that to the lead concentration and noticed that the reaction was spurred by the presence of lead. The mixture was transferred to a polydimethylsiloxane slab attached to a glass slide and after drying, deionized water was used to rinse off the chromate compound and the remaining sediment was imaged for analysis.

The microscopy imaging capability proved essential, because the quantity of sediment was too small to be imaged with an unassisted smartphone camera, making it impossible to detect relatively low levels of lead.

Source: rdmag.com