Near-IR spectroscopy can work for sample identification of organic compounds, but there are downsides with sample prep and interference from strong absorbers in the bands used, including water. The lenses and windows in the insurgents are made of IR-transmissive salt (often literally NaCl), which has to be kept dry and scratch free.
A better, and newer, option is to use Raman spectroscopy, which relies on the intrinsic molecular vibrations of a material (phonons) to shift the wavelength of interrogating light by a characteristic magnitude[1]. Once the Raman spectra is obtained, sample identification is a matter of finding the spectrum of the most similar compound in a database of known spectra. So in order to correctly identify something, it helps if it has been seen before and is present in the database.
Because Raman spectrometers are essentially a laser, some very narrow optical notch filters (band rejection at the interrogating frequency), and some fairly sensitive semiconductor detectors (often in the form of a mini spectrophotometer), the instruments can be made quite small. Some are even handheld and have integrated material databases[2].
A better, and newer, option is to use Raman spectroscopy, which relies on the intrinsic molecular vibrations of a material (phonons) to shift the wavelength of interrogating light by a characteristic magnitude[1]. Once the Raman spectra is obtained, sample identification is a matter of finding the spectrum of the most similar compound in a database of known spectra. So in order to correctly identify something, it helps if it has been seen before and is present in the database.
Because Raman spectrometers are essentially a laser, some very narrow optical notch filters (band rejection at the interrogating frequency), and some fairly sensitive semiconductor detectors (often in the form of a mini spectrophotometer), the instruments can be made quite small. Some are even handheld and have integrated material databases[2].
1. http://en.wikipedia.org/wiki/Raman_spectroscopy
2. http://www.thermoscientific.com/content/tfs/en/product/trusc...