Raman has become the “go-to” analytical method in materials science, pharmaceuticals, and homeland security. Its advantages are that it is nondestructive, detects analytes through packaging, and requires no sample preparation. The principal drawback is that Raman provides only confirmation, not quantitation.
Richard Larsen, Ph.D., spectroscopy products manager at Jasco (Easton, MD), divides Raman instrumentation into three categories: macro, micro, and imaging. Macro measures bulk properties in traditional “spectrophotometer” mode, micro instruments incorporate microscopy to analyze particles or very small samples, and imaging Raman involves spectral analysis of materials in 2D and 3D mode. Higher-end Raman spectrometers provide exquisite spatial and spectral resolution.
Portable Raman spectrophotometers come in plug-in and batterypowered formats. The latter, which are mostly handheld field analyzers, are popular for inspecting materials on loading docks, in oil exploration, for crime scene analytics, and for detection of narcotics and explosives. What makes handheld instruments possible are inexpensive 785 nm diode lasers that consume less than 1 amp.
Most users of Raman today view it as a tool like every other lab instrument. “To make systems appeal to these customers, vendors have to think a lot more about making self-optimizing instruments that are easy to operate, with little or no learning curve,” says Joe Hodkiewicz, Raman product manager at Thermo Fisher Scientific (Madison, WI). “This can be a challenge to designers with a lot of Raman experience, to whom instrumentation is second nature. Telling them they have to simplify things is a challenge.” Hodkiewicz compares the hurdles to making Raman accessible with the rise of digital cameras that allow users to take professional-quality photographs without worrying about exposure times, apertures, and film speed. “That’s the approach we’re taking with spectroscopy,” he says.
Another trend is the desire for flexibility and expandability. Users, Hodkiewicz says, are purchasing not just for today but for anticipated applications that may require future upgrades, for example, the use of different excitation lasers, microscope and automation options, specialized sample cells, and remote fiber probes.
Larsen views Raman as being at approximately the same level of acceptance and use as FTIR was 20 years ago. “Back then an FTIR cost $100,000 to $200,000. Now we’re down to sub- $20,000 FTIRs. Raman is going in the same direction. I don’t think it will ever be as widely used as FTIR, but there’s no doubt there is still plenty of room for growth.”
Raman has traditionally been viewed as an exotic, if not problematic, analysis method. The main limitation, says Haydar Kustu, global marketing communications manager at Bruker Optics (Billerica, MA), was the laser which was difficult to operate. “Today, manufacturers are improving their Raman spectrometers by paying more attention to the laser.” This has led, he says, to greater adoption of Raman in labs, and notable handheld product introductions as well. The signature trait of these newer systems has been reliability and ease of use.
• Features Volume Phase Grating (VPG®) as the special dispersion element and InGaAs array detector as the detection element
• Helps reduce the likelihood of human error by eliminating sample preparation and test interpretation
• Uses a fiber optic bundle or slit optics arrangement based on customer preferences
• Features self-automated wavelength calibration
• InGaAs photocathode and electron bombardment CCD technology provide high sensitivity
• Features a spectral range of 200 to 2,200 cm1 and a resolution of 10 cm1
• Includes a sample cell attachment for 8 mm vials, NMR tubes or MP tubes
• Provides the fluorescence rejection of a FT-Raman spectrometer and ease of fibre-optic interfacing of a dispersive Raman analyzer
• Provides an effective route for in situ monitoring
• Offered with either iC Raman™ 4.1 for reaction development and understand, or synTQLite for process monitoring and control
Kaiser Optical Systems
• Capable of integrating as many as 8 excitation lasers from the UV to the NIR
• Offers high-speed imaging using the Software Programmable Raman Integration System (SPRIntS)
• Verti-Scan ensures consistent confocal sample excitation for undistorted 3D images
• Dual Spatial Filtering reduces sample fluorescence while enhancing spatial resolution