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ANALYTICAL CHEMISTRY

Instantaneous recognition

Handheld device employs infrared radiation to ensure the quality of food, polymers, pharmaceuticals and textiles

Using the device to determine the sweetness and quality of apples

Léo RamosUsing the device to determine the sweetness and quality of applesLéo Ramos

In the near future, if a man wants to buy a 100% cotton shirt and doubts that the one being sold by the store is made ​​of this material, he can take out a pocket device, point to the fabric and see from the readout whether or not the fabric is indeed cotton as indicated on the label. The reality is that this type of portable equipment will within a few years be available, for example, to consumers, law enforcement and quality inspectors. The precursor of this device is the MicroNIR 1700 portable spectrophotometer, a compact instrument that operates in the near infrared wavelength, invisible to the human eye. With the potential to identify the chemical composition of commercial products and other types of objects without touching them, the device is being tested by a group of Brazilian researchers interested in making technology accessible to people with no technical knowledge.

The electromagnetic wave produced by the instrument is concentrated on the object being analyzed and is reflected and partially absorbed. With this information, the device generates data on the chemical composition distinguishing the object, which enables its identification and reveals details of interest to the user. “The MicroNIR has great potential, but methods and adaptations need to be developed before it becomes an effective tool for analytical problem solving; in addition, it must be made easier to operate. This is what we are trying to do in our research,” says Celio Pasquini, a chemist and professor in the Department of Analytical Chemistry at the University of Campinas Chemistry Institute (IQ-Unicamp) and coordinator of the National Institute of Advanced Analytical Science and Technology (INCTAA) supported by FAPESP and the National Council for Scientific and Technological Development (CNPq).

The NIR (which stands for near infrared) technology is not new. It has been around since the 1970s, but its use has been limited to expensive, complex and non-portable devices, mainly operated by specialized technicians or scientists. “The introduction of the MicroNIR 1700 in 2013 by the U.S.-based company JDSU opened up new opportunities for NIR spectroscopy, including the possibility of one day making it accessible to the average consumer,” says Pasquini.

075-077_Infravermelho_231Quantitave interaction
Pasquini says that near infrared spectroscopy is based on the study of the interaction between electromagnetic radiation and matter. Its use for various applications is already well established in the scientific literature, including for the quality control of foods such as milk and dairy products, oils, beverages, and seafood, as well as for the analysis of textile products, polymers and pharmaceuticals, among others. The technique involves measuring the intensity of radiation absorption in the near infrared range according to the wavelength produced by a certain object or sample.

NIR spectrophotometry is used for quantitative measurement of organic functional groups, especially O-H (oxygen and hydrogen bonding), N-H (nitrogen and hydrogen bonding) and C=O (double bonding between carbon and oxygen). Each object or sample has unique chemical characteristics—often resulting from complex compositions such as the human fingerprint—that can be identified by a spectrophotometer. “The atoms of the molecules making up any sample of organic substances are not static, or still, but vibrating. When we concentrate the appropriate amount of radiation that can be absorbed by a certain chemical bond, for example, this radiation is attenuated and transfers some of its energy to the vibration of the bonded atoms, which is recorded by the NIR spectrophotometry equipment,” says Pasquini.

“Interactions with the chemical substances present in the sample reveal its characteristics, and their measurement generates unique information that can be considered its fingerprint,” says Pasquini. One of the technique’s features is the fact that it is nondestructive, and allows access to the information inside intact samples.

“The new instrument used in our work cost $5,500, an amount that is about 15 times cheaper than conventional spectrophotometers. Moreover, it is portable, robust, easy to use, and provides an immediate answer. With all these features, we see it as a solution looking for a problem—similar to the technology of lasers in the 1960s,” says Pasquini.

Pasquini is also part of the Instrumentation and Automation in Analytical Chemistry Group (GIA) of Unicamp’s Chemistry Institute, which also includes Jarbas José Rodrigues Rowedder and Ivo Milton Raimundo Júnior, researchers at INCTAA. GIA has been working with spectroscopy since 1995. It is one of Brazil’s pioneering centers in the research and development of this technology, and has already developed several instruments resulting in four patent applications. One of them is used to ensure fuel quality control by determining the alcohol content in gasoline and the presence of water in ethanol. The device is marketed by Tech Chrom, a Campinas-based company, and used to prevent the most common types of fraud in these products (see Pesquisa FAPESP Issue No. 209).

Results on display
Matheus Angeluzzi Jardim, a graduate student at Unicamp’s Chemistry Institute and a member of Pasquini’s team, says that the effectiveness of the MicroNIR 1700, which measures 4.5 cm long , 4.2 cm wide and weighs 150 grams, depends on having a vast database of the fingerprints or absorption spectrum of a large number of samples. Thus, when reading a specific object, the machine makes its identification by comparing the absorption spectrum captured from the object with spectra previously stored in the database. For now, the device only shows the results as graphs on a computer screen. In the future the results will be shown, more simply, on a small display on the device itself.

“Let’s suppose we want to analyze textile products to create a model that can identify whether a certain dress is, in fact, made of silk, as stated on its label. The first step would be to have a few dozen silk fabric samples of different colors and patterns and thereby obtain their absorption spectra,” says Jardim. Then, by using chemometrics—the science of applying statistical and mathematical tools to obtain information from vast data sets—the researchers generate a classification model capable of statistically identifying whether or not the spectrum of the sample indeed matches that of silk. Finally, with the finished model, a spectrophotometer such as the MicroNIR 1700 can be used on any garment to determine whether or not it is silk.

For now, the library of models is being assembled in Brazil only by Pasquini’s group. “We already have a sufficient library to create models to determine sugar in fruits such as oranges, kiwi and apples, as well as to identify textiles—cotton, polyester, leather, silk and others,” says Jardim. One of the goals of his master’s work is to create a model to determine the Brix scale—a measure that indicates the amount of dissolved solids in fruit, which directly reflects the amount of sugar present in it.

The spectrophotometer therefore could help consumers select fruits at the supermarket according to their sweetness preference. “The initiative to build databases and models, like the one we are working on, is the focus of several research groups around the world. But this work is still being done in isolation. In the future, collaboration between Brazil and groups from other countries could be an opportunity to develop more universal databases. But this is a job that will take a few years. In the system now being built, the models for the devices will always be automatically updated via the web and wireless communications,” says Pasquini.

The device could also be used to determine whether a certain piece of furniture was made ​​with the wood reported by the manufacturer, whether a medicine really has the chemical composition announced by the manufacturer, and so on. “The MicroNIR could be very useful in verifying the authenticity of goods, curbing the sale of counterfeit or pirated products, a problem costing billions of dollars each year worldwide. Data in the scientific literature also show that the technology has the potential to be used in identifying counterfeit currency,” says Unicamp’s Jardim. “As portability is a growing trend in our society, I believe that over time it may be possible to make an NIR device for a smartphone. When this happens, near infrared technology is likely to gain momentum, and anyone will be able to use it.”

Project
National Institute of Advanced Analytical Science and Technology (INCTAA) (No. 2008/57808-1); Grant mechanism: Thematic Project – INCT; Principal investigator: Celio Pasquini (Unicamp); Investment: R$375,421.77 and $531,453.87 (FAPESP).

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