PerkinElmer Spectrum FTIR — Mid-Infrared Spectrometers in the Gem Lab
PerkinElmer Spectrum FTIR — Mid-Infrared Spectrometers in the Gem Lab
The Spectrum and Frontier benchtop FTIR series in gemmological practice
The PerkinElmer Spectrum series is a family of mid-infrared Fourier-transform infrared spectrometers used widely in gemmological laboratories for material identification and treatment detection. The Spectrum Two and the higher-specification Frontier are the models most frequently encountered in the trade, configured as benchtop instruments with attenuated total reflectance (ATR) and transmission sampling accessories. FTIR is one of the standard tools, alongside UV-Vis-NIR spectroscopy, Raman, and EDXRF, that a modern gem laboratory deploys when a stone's identity, treatment status, or origin is in question.
What FTIR measures
Fourier-transform infrared spectroscopy probes the vibrational modes of molecular bonds. When a sample is illuminated with mid-infrared radiation, bonds in the material absorb at characteristic frequencies determined by the masses of the atoms and the bond stiffness. The resulting absorption spectrum is a fingerprint of the molecular structure. In gemmology, this fingerprint is diagnostic of polymer impregnations, oils and resins in fissure fillings, water and hydroxyl content in beryl and other species, and certain features associated with high-temperature treatment of corundum and other materials.
The Spectrum Two and Frontier instruments cover the standard mid-IR range of approximately 4000 to 400 wavenumbers, with the Frontier extending into the near-infrared and far-infrared with appropriate detectors and beam-splitters. ATR sampling, in which the sample is pressed against a diamond, germanium, or zinc selenide crystal, allows non-destructive analysis of finished stones without the sample preparation required by traditional transmission or KBr-pellet methods.
Applications in gemmology
For emerald, FTIR is the principal tool for distinguishing oil from polymer-resin filler in fissures. Cedarwood oil, Opticon, and various proprietary resins each produce characteristic absorption patterns in the C-H stretching region around 3000 wavenumbers and elsewhere. Laboratories use these signatures to grade clarity enhancement on the AGTA scale (none, minor, moderate, significant) and to detect filler types that have implications for value and care.
For corundum, FTIR contributes to the detection of certain heat-treatment indicators and, alongside other instruments, to the identification of beryllium-diffusion-treated material. For beryl species more broadly, the OH and water region carries information about origin and growth environment. For amber and other organic gems, FTIR distinguishes natural amber from copal and from various plastic imitations. Composite materials — assembled stones, glass-filled rubies, polymer-impregnated turquoise — typically reveal themselves clearly in the IR.
Practical considerations
The Spectrum Two is the more common choice for trade laboratories needing routine treatment detection at a moderate budget. The Frontier is positioned for research-grade work with extended spectral range and higher signal-to-noise. Both instruments require a controlled environment — humidity affects the diamond-window ATR crystal, and temperature stability matters for long-term reproducibility — but neither is exotic to operate. Software automates baseline correction, peak identification, and library matching, reducing the analyst's workload to interpretation.
FTIR is not a stand-alone identifier. The trained gemmologist combines IR data with microscopic observation, refractive index, UV-Vis-NIR, Raman, and EDXRF to reach a confident conclusion. The Spectrum series simply provides the IR layer of that workflow at a level of quality and reliability that has made PerkinElmer instruments the default in many laboratories worldwide.