Innovative Spectrograph Has Medical Applications

A high-precision spectograph holds promise in multiple applications, from the early detection of diseases to monitoring for chemical weapons and environmental pollutants.

Researchers at PAIR Technologies (Newark, DE, USA) developed the new sensor, a planar array infrared (PAIR) spectrograph, which can identify biological and chemical agents in solids, liquids, and gases, present at low levels, and in less than a second. The new spectrograph has no moving parts, and relies on a focal plane array (FPA) detector which consists of a cluster of light-sensing pixels at the focal plane of a lens to receive optically dispersed infrared light, displaying the individual wavelength components. The detected image can be immediately converted to a spectrum by either plotting intensity versus pixel location for a single row, or by first coaveraging a number of rows before carrying out this operation. Since the PAIR instrument contains a slit, image curvature occurs, but proprietary software removes any frequency variations from row-to-row due to misalignment of the spectra caused by image curvature. Because the PAIR instrument incorporates an ultrafast FPA, it is capable of obtaining an IR spectrum in less than 100 µsec integration times; this enables a whole range of kinetics and dynamics experiments to be carried out that were previously inaccessible. The patent of PAIR technology belongs to the University of Delaware (Newark, USA; www.udel.edu), which also has a minority position in the company.

"This is a rugged replacement for the existing technology, taking it out of the lab and into the field," said Bruce Chase, Ph.D., PAIR cofounder, who recently retired from DuPont (Wilmington, DE, USA) as a research chemist. "Our instrument has no moving parts. It's durable, compact, and portable -- you can carry it out to your local stream or use it in a doctor's or dentist's office."

Current detection technology, which is based on Fourier Transform Infrared (FT-IR) spectrography, requires tens of minutes to chemically identify a molecular fingerprint. An FT-IR spectrograph divides the infrared light source into two beams that reflect off both a fixed and a moving mirror. Two separate experiments must be run for every analysis, one with the sample, and one without, to account for any environmental interference, which must be mathematically reconciled. Additionally, the sample chamber must be purged with nitrogen gas to displace any water vapor.

Besides medical, environmental, and military monitoring solutions, the researchers see applications in industry to help maintain and improve manufacturing processes, ensuring, for example, the purity of pharmaceutical drugs or the thickness of paints or polymer coatings.

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PAIR Technologies

University of Delaware