A Compact Benchtop FTIR Spectrometer for the Academic Laboratory

Fourier transform infrared spectrometers (FTIRs) currently used in colleges and universities have several limitations. Their size and complexity limit the number of students that can be accommodated. The instruments are not always rugged enough to stand up to tough handling by students. System maintenance and validation of functionality require time management and resources.

The ALPHA FTIR spectrometer (Bruker Optics, Billerica, MA) was designed from the ground up to address these concerns. It occupies the footprint of an A4 sheet of paper, less than half the size of current academic instruments. It is the first instrument targeted to the academic market to offer a permanently aligned interferometer with a wear-free bearing. The attenuated total reflectance (ATR) sampling accessory and software that controls the instrument are both simpler and more robust than current academic offerings.

Limitations of current academic instruments

FTIR spectroscopy is a well-established and important technique for sample analysis and characterization that has found daily application across many disciplines of endeavor. These include pharmaceutical products, materials science, and forensic science. As such, students are introduced to FTIR in organic and physical chemistry, materials science, chemical engineering, physics, and other academic programs. The first exposure to FTIR is usually in the second semester of organic chemistry along with other basic analysis methods such as liquid chromatography. Traditionally, students were taught to press samples in KBr pellets, but more recently ATR accessories have become the predominant FTIR sample analysis tool. This is because sample handling is greatly simplified and sample preparation is all but eliminated.

Space is often an issue in the chemistry laboratory because of the need to introduce many students to multiple instruments. Multiple copies of each instrument are required in order to accommodate an entire class in a reasonable amount of time. However, instruments used today in the academic setting tend to be nearly as large and bulky as the more powerful instruments used in industrial settings.

Ease of use is another critical requirement for an academic instrument. If the mechanics of the instrument are too complex, students will have to spend considerable time figuring out its operation, limiting the amount of time that can be spent on academic goals. Unfortunately, the software that drives the instruments used in academia is not always easy and straightforward. Because the software is menu-driven, it requires the user to know the right commands or to hunt for them in order to complete the analysis.

Academic instruments need to be able to withstand handling that tends to be rougher than that seen in industry or research applications. With perhaps 200 students per semester using an instrument, downtime to even a single instrument can adversely affect the course timeline.

Most conventional academic instruments use interferometers with dynamically aligned flat mirrors that move on mechanical bearings. Typically, the fixed mirror is equipped with piezo transducers that tilt one mirror to compensate for positional errors detected in the scanning mirror. If the instruments are subjected to shock and vibration, as is common in the classroom environment, they may need to be realigned. The interferometers of current instruments also use mechanical bearings that are prone to wear, and may move the output beam relative to the detector enough to reduce system stability (U.S. Patent 5,883,712). These bearings typically have to be serviced or replaced every three to five years with heavy usage.

Current academic FTIRs also use HeNe reference lasers that are subject to damage if the instrument is dropped or bumped. HeNe lasers also lose gas over time, resulting in replacement every three to five years under the best circumstances.

New spectrometer designed to meet academic needs

Figure - 1 Undergraduate students using ALPHA FTIR spectrometers during a chemistry class at Loras College in Dubuque, IA. (Photograph courtesy of David Oostendorp, Ph.D., Professor of Chemistry, Loras College.)

Figure 2 - OPUS/Mentor software provides guided analysis.

Figure 3 - ATR accessory prevents sample positioning errors.

The ALPHA FTIR spectrometer was designed specifically to address these concerns in order to meet the needs and requirements of the academic market. The design of the instrument is based on research that was originally performed to develop compact and rugged FTIR spectrometers for military applications.1 The robustness and compactness of these militarized spectrometers is reflected in the ALPHA spectrometer. It provides sensitivity, wavelength axis reproducibility, and stability that are at least equal to or typically exceed those provided for academic use.

With a footprint of only 22 × 30 cm (about 8 × 11 in.), the ALPHA is the world’s smallest FTIR. The spectrometer is also light, at about 7 kg (13 lb). Occupying only half the space of instruments now used in the classroom, the ALPHA makes it possible for universities to better utilize scarce laboratory space and thus serve more students in less time (Figure 1).

The ease of use of the ALPHA FTIR spectrometer makes it well suited for use in the classroom environment. The entire analysis process is driven by wizards that guide the user through every step (Figure 2). It is nearly impossible for the user to get lost or make a mistake that will generate incorrect results. The user interface can also be easily customized, making it even easier for students to use. For example, an administrator or laboratory manager can further tailor the user interface, while students only have access to the basic functionality. The ALPHA also has its own validation routine that runs without user intervention. This saves time by eliminating the need for manual validation runs. It also includes a Kensington lock that can be used to secure the instrument and prevent unauthorized removal from the laboratory.

The ALPHA FTIR spectrometer offers three easily exchangeable sampling modules. The Platinum ATR accessory (Figure 3) is a single-reflection diamond ATR sampling module that is easier to use than conventional ATR accessories. The ergonomic one-finger clamp simplifies sample positioning. The user simply flips a lever to make optimum contact pressure with the sample. The device also has an indicator that shows a red dot when the clamp is engaged and no color when it is not engaged. The simplicity of the ATR accessory makes it easy to achieve reproducible results.