Analyzing Fingerprints With A Dash Of Turmeric

Turmeric has a long history as a kitchen spice, dye, and traditional medicine. Now researchers have cooked up a new use for the gold-colored powder: Its main ingredient, curcumin, could help forensic scientists analyze the molecular constituents of fingerprints using mass spectrometry (Anal. Chem., DOI: 10.1021/ac4007396). Chemical information from fingerprints might reveal characteristics such as a suspect’s sex or if a person has recently handled cocaine, the researchers say.

Typically, forensic experts study fingerprint patterns to connect a suspect to a weapon or the scene of a crime. Simona Francese of Sheffield Hallam University, in the U.K, develops ways to get chemical information from the prints using matrix-assisted laser desorption ionization (MALDI) mass spectrometry. In this technique, researchers crystallize samples within a chemical matrix to protect the molecules and help ionize them. When the researchers shine a laser on the crystals, the sample molecules ionize and fly into the air. A mass spectrometer then measures the mass of the jettisoned ions.

Unfortunately, the dust used to visualize prints can obscure mass spectrometry results. Francese thought curcumin would be a MALDI-friendly alternative to the standard dust because its structure—with its multiple double bonds—suggested it could make a good matrix. She got this insight after reading a 2011 study that showed curcumin works as a nontoxic and inexpensive dusting agent on a variety of surfaces (Egypt. J. Forensic Sci., DOI: 10.1016/j.ejfs.2011.04.011).

Francese and colleagues dusted half of a fingerprint with curcumin and the other half with α-cyano-4-hydroxycinnamic acid, a standard matrix. They then scanned a laser over the fingerprint’s surface, collecting spectra on the constituent compounds as they went. The researchers compared the intensity of the signals from each half of the fingerprint. “In most cases,” Francese says, “we found that curcumin performed better,” generating taller and sharper peaks on the spectra for fatty acids and other molecules. In another experiment, the researchers spiked fingerprints with cocaine, which curcumin effectively ionized, producing a clear spectrum.