A new molecular gel recipe developed at the University of Michigan is at the core of a prototype for a more accurate lead paint test.

The test makes it easy to see whether a paint chip contains more than the regulated 5,000 parts per million (ppm) of the poisonous metal that was banned from pigments in 1978. Government agencies use that threshold to define paint as "lead based," and the Environmental Protection Agency requires that home test kits can differentiate above and below it. Yet these home kits have a wide margin of error and produce many false positives, the researchers say.

According to the researchers, led by Gesine Veits, a postdoctoral scholar in chemistry, the new test is simpler and more accurate than its counterparts. It consists of a vial that holds paint thinner and a sprinkling of certain salts that, when combined with the right concentration of lead, form a gel.

Gesine Veits, a postdoctoral scholar in chemistry, examines a sample. Image credit: Joseph Xu, UM Engineering.Users drop a paint chip in, heat the mixture and observe how the solution reacts. If a gel forms and stays at the top of the inverted vial, it is positive for at least 5,000 ppm lead. If the solution stays liquid and no gel forms, there may be lead in the paint, but not enough to require steps to maintain it or get rid of it.

To come up with their recipe, the researchers first assumed that exploring crystal growth could give them insights about gel formation. Crystals are rigid solids, and gels are in between solids and liquids.

Next, they turned to the Cambridge Structural Database, a global repository of more than 800,000 crystal structures. Any researcher who reports a new crystal structure is required to enter it in the database.

They looked for crystals that contain lead and then narrowed their search criteria further. From examining gels under a microscope, they knew gels often resemble bowls of spaghetti—tangles of long fibers. Of the possible crystal structures, it occurred to them that a long strand would be most similar to a needle-shaped crystal. So the research team zeroed in on the crystal structures that contain lead and produce a shaft shape. They then used those molecules as their starting point.

The team says the test could help homeowners and renters better understand their level of risk. They say it also pushes forward some exciting science—demonstrating a more streamlined approach to making targeted molecular gels, Jello-like substances that hold promise for sensing, biomedicine and environmental cleanup applications.

The university is now pursuing patent protection for the intellectual property and seeking commercialization partners to help bring the technology to market.