Advantages and Disadvantages of Raman spectroscopy

Advantages

Disadvantages

Can be used with solids and liquids
No sample preparation needed
Not interfered by water
Non-destructive
Highly specific like a chemical fingerprint of a material
Raman spectra are acquired quickly within seconds
Samples can be analyzed through glass or a polymer packaging
Laser light and Raman scattered light can be transmitted by optical fibers over long distances for remote analysis
Raman spectra can be collected from a very small volume (< 1 µm in diameter)
Inorganic materials are normallys easier analyzed by Raman than by infrared spectroscopy

Can not be used for metals or alloys.
The Raman effect is very weak. The detection needs a sensitive and highly optimized instrumentation
Fluorescence of impurities or of the sample itself can hide the Raman spectrum
Sample heating through the intense laser radiation can destroy the sample or cover the Raman spectrum

Comparison of Raman, infrared, and near infrared spectroscopy

Raman spectroscopy combines the advantages of infrared spectroscopy with the advantages of near-IR spectroscopy. Although the fingerprinting techniques Raman and infrared spectroscopy are based on different physical processes, both excite fundamental molecular vibrations or rotations. These are easily analyzed or interpreted. In the near infrared typically the broad and less specific absorptions of the vibrational combination and overtones of carbon-hydrogen (C-H), nitrogen-hydrogen (N-H), and oxygen-hydrogen (OH) bondings are observed. The analysis of NIR spectra is limited to specific analytical issues and needs often a time consuming method development. However, in the near infrared glass is transparent that reduces sample preparation and provides remote sampling by fiber probes.

	Raman Spectroscopy	Mid Infrared Spectroscopy	Near Infrared Spectroscopy
Phenomenon	Scattering	Absorption	Absorption
Information	Fundamental vibrations (down to low wavenumbers)	Fundamental vibrations	Overtone and combination bands
Type of sample analyzed	Organics and Inorganics	Organics and Inorganics	Organics
Sample Preparation	None	Normally required	Seldom
Sample State	Solids and liquids	Solids, liquids, and gases	Mainly solids
Glass Vials	Yes	No	Yes
Water	Yes	Water has a strong spectrum	Yes
Remote Sampling	Yes	No	Yes

Home • Fundamentals • Technology • Links