Infrared detector unmasks cocaine addicts

If a police patrol stops a suspicious driver these days, he has to blow into the famous tube for an alcohol test. If the driver is suspected of having consumed illegal substances like cocaine, however, the officer has to order a complicated and expensive lab test to obtain quantitative results. A new approach could now make the process easier: a team of ETH-Zurich researchers headed by physics professor Markus Sigrist is currently developing a device to detect cocaine in saliva. “Our work is the basis for a compact device that law enforcement authorities can use ‘in the field’,” says Sigrist. This basis for rapid drug detection has just been presented in an article published in the journal Drug Testing and Analysis.

A few micrograms suffice

With the aid of so-called ATR infrared spectroscopy, the researchers have succeeded in detecting cocaine and a variety of its metabolic products in saliva reliably and currently up to a threshold of fewer than ten micrograms of cocaine per millilitre. Compared to the standard methods at toxicology labs, which can trace the drugs up to a threshold of one to five nanograms per millilitre, this limit of detection is still too high. However, the samples have to be prepared painstakingly and the apparatus is not transportable. The ATR-IR method is different: it is non-invasive and the saliva can be obtained easily and with little preparation. Moreover, the detection levels reached using ATR-IR spectroscopy are already accurate enough to take consumers of illegal drugs into custody directly after consumption. If someone smokes cocaine, for instance, up to 500 micrograms per millilitre are still present in the saliva a short time later.

Careful not to mix up cocaine and caffeine

The first important step for the ETH-Zurich physicists was to find out which wavelengths cocaine and its metabolic products absorb, so they examined the spectra that are characteristic and distinctive of these substances.

The physicists also had to determine the spectra of other substances present in the saliva. to make sure they do not overlap within the spectrum of cocaine. Consequently, they examined caffeine, extenders used to cut cocaine, mouthwash, painkillers, and energy and soft drinks. The researchers especially focused on alcohol. The result of this detective work was that the cocaine spectrum leaves behind distinct traces. The substance and its metabolic products absorb within a wavelength range of 5.55 to 5.84 micrometers. However, because water in the saliva absorbs the infrared light strongly, the researchers first extract the cocaine with a water-repellent solvent that then evaporates on the test apparatus.

More accurate detectors, better light

Meanwhile, Markus Sigrist and his team are in the process of refining and simplifying the procedure. For instance, they have also begun measuring cocaine directly in the liquid phase after extraction into the solvent. The physics professor also wants to reduce the detection threshold dramatically. He believes it is possible to detect amounts of twenty nanograms per millilitre of liquid using the infrared spectroscopy method. Apart from more sensitive IR detectors that are ten times more sensitive, the researchers therefore also require a new light source: a so-called “quantum cascade laser”, which can generate infrared light within a narrow spectral band around a central wavelength of between four and fifteen micrometers. “This range is interesting for spectroscopy,” says Sigrist. The initial experiments with this light source have been positive. It might also be possible to extend the drug test for the detection of other narcotics, such as heroin.

However, Markus Sigrist and his team will not be developing a market-ready, compact device, for instance, for law enforcement officers,: “We provide the basis and a sensor platform for such a device. It is up to an industrial partner to realize it,” says the ETH-Zurich professor.

The detection of cocaine in saliva using infrared is a sub-project of IrSens conducted within the scope of the nationwide Swiss research initiative nano-tera. Besides Sigrist’s team, the research group headed by ETH-Zurich professor Jérôme Faist which developed the quantum cascade laser and other teams, including detector specialists from the University of Neuchâtel, are also involved in the sub-project.

Infrared spectroscopy

The measurement method is based on ATR infrared spectroscopy (IR-ATR). ATR stands for “attenuated total reflection”. This measurement technique was developed in 1960 and is used to examine the surfaces of opaque substances such as varnish or polymer foil. However, it can also be used to analyse liquid samples.

In IR-ATR, an infrared beam of light is directed into a crystal at a particular angle. The beam is reflected on both surfaces and thus crosses the entire crystal along a zigzag path before exiting it. The substances to be analysed are then applied to the upper surface of the crystal in an thin layer. The absorbed wavelengths are absent when the beam of light exits the crystal, which the researchers can measure.

More information: Hans KMC, Müller S & Sigrist MW. Infrared attenuated total reflection (IR-ATR) spectroscopy for detecting drugs in human saliva. Drug Testing and Analysis (2011), published online, doi: 10.1002/dta.346

Provided by ETH Zurich

Outlook for an industry that touches 96 percent of all manufactured goods

C&EN points to positive developments for some chemical manufacturers, like Boeing ramping up production of its Dreamliner planes, a boon for makers of high-tech glues and carbon fiber. The article explains U.S. chemical firms will be more competitive globally due to low prices of natural gas and other raw materials and good opportunities for exports. Petrochemical producers are looking past 2012, according to the article, and several companies plan to build new manufacturing plants to take advantage of the growing supply of natural gas in the U.S.

At the same time, the pharmaceutical industry is facing the challenge of expiring patents on some of its most popular drugs, which will allow generic manufacturers to grab profits from big-name companies like AstraZeneca. The story also predicts slowing growth in Asia will hurt a number of chemical industries, especially makers of paint and other construction materials. For chemical makers, the article says, "2012 is likely to be a year to endure rather than enjoy."

More information: World Chemical Outlook - http://cen.acs.org/articles/90/i2/World-Chemical-Outlook.html

Provided by American Chemical Society (news : web)

Strengthening metal alloys would provide energy, environment conservation benefit

The results of the work promise to help engineers and scientists better understand how to enhance the performance of new light-weight materials used in a wide variety of technological applications. The light-weight materials can be particularly effective in helping to improve the energy efficiency of motor vehicles and reduce their polluting emissions.

Solanki recently joined ASU as an assistant professor in the School for Engineering of Matter, Transport and Energy, one of the university’s Ira A. Fulton Schools of Engineering. He combines expertise in solid mechanics and material science to study the microstructural properties of materials and predict their behavior under various conditions.

The Minerals, Metals & Materials Society (TMS) has awarded Solanki and two co-authors its 2011 Light Metals Magnesium Best Paper award for the report detailing their research on light-weight metal alloys.

He has been aided by Mehul Bhatia, who is pursuing a doctoral degree in mechanical engineering at ASU, and Amitava Moitra, a former postdoctoral fellow at Mississippi State University who worked there with Solanki. Bhatia and Moitra are the winning paper’s other co-authors. 

Titled “Effect of Substituted Aluminum in Magnesium Tension Twin,” the paper addresses a major challenge in development of new alloys. It involves finding ideal concentrations of new solutes that can be added to base metals to optimize their performance. Solutes are substances that dissolve into another substance in solutions.

The solute additions are critical to enhance the deformation and failure modes of materials, which occurs both when alloys are manufactured and when they are subjected to complex loading such as in a crash impact, Solanki explains.

Understanding how the metal alloy will respond in such circumstances provides information needed to make effective adjustments in the ratio of the solute to the base metal in a solution. That ratio is important in affecting the mechanical properties of an alloy to produce an optimal performance.

In the award-winning paper, Solanki’s research team demonstrates use of a nanoscale simulation technique to reveal how an aluminum substitution in pure magnesium affects its deformation and its behavior when the material fails.

“Our research provides a fundamental understanding of the role of solutes on deformation and fracture modes of metal alloys,” Solanki says. “This will guide the science of designing structural materials with enhanced properties and performance capabilities.”

He is working with magnesium and magnesium alloys because they are particularly light-weight materials that also offer the advantage of being highly recyclable.

“With the world’s energy needs increasing, energy efficiency and conservation become more important. More effective light-weight structural materials that help reduce the energy consumption needed for transportation will contribute to meeting that goal,” Solanki says.

Prior to coming to ASU, Solanki was an associate director at the Center for Advanced Vehicular Systems at Mississippi State University, where he earned a doctorate degree in 2008.

He has published more than 50 peer-reviewed journal and conference papers and he serves on the editorial board of the Journal of Surfaces and Interfaces in Materials. His paper “Finite element analysis of plasticity-induced fatigue crack closure: an overview,” published in Engineering Fracture Mechanics, was one of the most highly cited papers from 2002-05.

Solanki won the 2008 Henry O. Fuch Award from the Society of Automotive Engineers International for outstanding achievements in fatigue and fracture mechanics.

Solanki and Bhatia will be presented their best paper award from the Minerals, Metals & Materials Society at the organization’s annual meeting in March in Orlando, Fla.

Provided by Arizona State University (news : web)

Twist-and-glow molecules aid rapid gas detection

Now, Takashi Uemura of Kyoto University and colleagues at several other Japanese institutes, including the RIKEN SPring-8 Center, have created a gas sensor that works rapidly, emits a clear fluorescent signal, and detects different gases. Most importantly, the new sensor can distinguish between gases with similar chemical and physical properties.

Uemura and colleagues’ sensor contains so-called ‘flexible porous coordination polymers’ coupled with fluorescent reporter molecules that change structure, and therefore emit signals, according to different gases present in the air. 

“We thought that the incorporation of functional polymers into flexible porous coordination matrices would show unique dynamic properties,” says Uemura. He and his colleagues therefore inserted a fluorescent reporter molecule into the coordination polymer, whereupon the whole combined structure twisted out of shape.

In this normal and twisted state, the fluorescent light from the reporter is quite dim and green. Once gas molecules are introduced, the structure begins to return to its original shape, and the fluorescence returns, brightening as the gas pressure intensifies. For example, the fluorescence changes from green to blue when the molecule adsorbs carbon dioxide.

By this method, the sensor allows regular monitoring of both the type of gas and its concentration in the air. Crucially, the fluorescent response begins within seconds upon interaction with the gas and is complete within minutes, allowing emergency responders to make decisions quickly (Fig. 1).

In addition to these attributes, this is the first such detection system shown to work for gases with almost identical physical properties, the team notes. “Physical properties, such as size, shape, and boiling points, are very similar between carbon dioxide and acetylene, for example, so it is difficult to distinguish between them,” explains Uemura. “Our material has carboxylate sites in the pore, and these sites can bind to acetylene more strongly than carbon dioxide.

“This unique cooperative change of host and guest could allow us to design new advanced materials,” he adds. By investigating different flexible host structures and other ‘guest’ reporter molecules, the researchers believe they could create gas detection systems for a variety of different gases and other applications in the future.

More information: Nature Materials 10, 787–793 (2011) doi:10.1038/nmat3104

Provided by RIKEN (news : web)