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Cosmos » Materials » Using a phone to identify molecules
With a few additions, commercial smartphones can be used as microscopes and medical monitors. But the humble phone may have more applications in scientific analysis. A group of US researchers has contributed compelling research to the growing potential for phones to carry out spectroscopy, which could allow them to identify individual chemicals in drugs, contaminants and pathogens.
Spectroscopy refers to a range of methods that identify molecules by shining different types of light on substances and seeing how it’s absorbed or reflected. Infrared spectroscopy, for example, uses infrared light and is useful for telling researchers about the bonds between atoms in a molecule.
Most chemists use spectroscopy of one form or another in their work, but it’s particularly crucial in forensic science and environmental monitoring – both of which involve a lot of work in the field, and thus benefit from having smaller, more portable devices. Australian researchers have previously developed technology that could allow a phone to do infrared spectroscopy, but analytical techniques like this are not widely available in phones yet.
The new research, published in Review of Scientific Instruments, describes two different types of spectroscopy that could be integrated into a phone: Raman and fluorescence spectroscopy. Fluorescence spectroscopy measures fluorescent light emitted by a sample, and is particularly useful for identifying organic molecules. Raman spectroscopy is used to examine the way molecules vibrate and rotate, and is used for detecting molecules like DNA and RNA, among other things.
The researchers, based at Texas A&M University in the US, created a device roughly the same size as a smartphone, consisting of a laser, a lens, a spectroscope that splits light and a grating that scatters light in a specific way onto a phone’s camera. Samples sit between the grating and the camera, and the researchers manipulated the focus settings on the phone cameras until they could accurately measure the light coming through.
The whole setup costs around $50 US, or $65 AUD. The researchers used it to study a few common solvents, like ethanol and acetone, as well as some solid objects like a carrot and a pellet of bacteria. They could identify molecules correctly in each substance.
The device was about a tenth as sensitive as a commercial Raman spectrometer, which would usually cost thousands of dollars. The researchers have a few ideas for additions that could make the device more sensitive.
“This inexpensive yet accurate recording pocket Raman system has the potential of being an integral part of ubiquitous cell phones,” conclude the authors in their paper. They say the device “will make it possible to identify chemicals impurities and pathogens, in-situ, within minutes.”
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Assuming they’re accurate, cheaper devices like this could be used to identify drugs, including in pill testing scenarios.
Jody Moller, an Associate Research Fellow at the University of Wollongong who was not involved in the study, says the device is a “novel use of technology”, but there are a few limitations on its use in pill testing. First, the readings generated from the phone need to be matched to a spectroscopy database of known substances to identify compounds.
“This is obviously an issue for new psychoactive substances as there would be no known spectra available for these compounds (this is an issue with all pill-testing methods currently available).”
A second limitation is that “in complex mixtures it would difficult to identify psychoactive compounds.”
“It would be able to identify the major compound/s present but it would likely be unable to identify compounds present at low concentrations or samples with complex mixtures,” says Moller.
“It would be interesting to see the effects of real-life samples to provide an indication of background effects of other components in the mixture such as colouring and flavouring compounds,” she adds.
“Overall if this method is validated and is shown to work in a pill-testing setting it would allow for a cost effective technique to be employed,” says Moller.
She stresses that pill testing still requires qualified professionals, though. “It is important that there is a chemist performing the analysis as interpretation isn’t always easy.”
Originally published by Cosmos as Using a phone to identify molecules
Ellen Phiddian is a science journalist at Cosmos. She has a BSc (Honours) in chemistry and science communication, and an MSc in science communication, both from the Australian National University.
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