Seminar: Raman Spectroscopy

Sunday, November 14, 2010

NIR Spectrometer

By Alston Kook

NIR spectrometers are the new generation of Fourier Transform near Infrared (FT-NIR) spectrometer. These are the first industry hardened FT-NIR systems that are strong enough to withstand the harsh conditions.

NIR spectrometer uses the state-of-the-art optics for exceptional sensitivity and stability. There is continuous improvement in the designs and this provides consistent high quality results with less downtime, direct methods transfer and probable new applications. These NIR instruments can be used both in the lab and the factory; thus eliminating the need for new instrument during integration with the process control system.

In addition, the same NIR instrument can go directly from the lab to the factory, and this removes the need for a new instrument when your method is ready for integration into your process control system. These can further be integrated easily because of the Full support of industry standard communication protocols available.
The most successful NIR instrument is the Raman spectrometer which was developed for process control and automated lab applications. The system emphasize an On-Axis spectrograph, optimized for Raman spectroscopy and one standard grating covering the most widely used Raman signature range. The patent pending curve slit correction for aberration free imaging, low noise CCD and innovative technology in signal processing result in excellent signal to noise ratio and high performance.
Many NIR instrument come with no moving parts, being free from mechanical wear it requires low maintenance. The integrated diode laser provides 532 nm or 785 nm with different power levels available.

The system comes equipped with a Class 3 light-tight safety enclosed with interlocks in 19" rack

The NIR spectrometer has taken NIR spectroscopy to new heights and is compatible for a choice of laboratory, site glass and process immersion probes, allowing real time process monitoring from a remote location. The Raman UniLab Research is a high sensitivity device designed to utilize both large illumination and collection areas. The large illumination design reduces the susceptibility of sample misalignment as well as decreases the effects of heterogeneity issues of the sample, resulting in superior averaging capability.

NIR spectroscopy utilizes Sure_Cal calibration technology, a method for achieving a standard Raman spectrum that has both short and long term precision and accuracy. The Sure_Cal technology allows for the collection of the standard spectrum independent of any instrument instabilities. The Raman spectrum from the sample, the laser/neon spectrum and the neon spectrum are collected simultaneously.
The NIR instruments are also much easier to implement, operate, and maintain. The NIR spectrometer is a compact fibered spectrometer able to measure from 900nm to 2600nm or from 2000nm to 4500nm with a resolution of 8cm-1 (or about 1-5 nm). This world known unique scanning Fourier Transform Spectrometer (FTS) uses an exclusive actuator fabricated thanks to modern micro machining technology. The spectrometer needs only a single detector that assures highest dynamic range and allows attractive pricing.

Alston is an eminent analyst and writer which are writing about NIR analyzer. For more info visit at
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Tuesday, October 5, 2010

Raman Spectrometer

Raman Spectrometer

By Hamilton Sunstrand

Raman spectrometer is a monochromatic visible laser. The scattered radiation can be analyzed by using scanning optical monochromator with a phototube as a detector. A laser beam is used to irradiate a spot on the sample under investigation. The scattered radiation produced by the Raman Effect contains information about the energies of molecular vibrations and rotations and these depend on the particular atoms or ions that comprise the molecule, the chemical bonds connect them, the symmetry of their molecule structure and the physio-chemical environment where they reside.

Raman spectrometer measures the wavelength and intensity of inelastically scattered light from molecules. It is used to determine the chemical composition of a sample based on the wavelength and intensity of the light passing through the sample. Raman spectroscopy is based on the theory of Raman scattering, which states that light is scattered due to the vibrations of the molecules in the substance and changes its energy from that of the incident light. In this way, Raman spectrometers use the Raman Effects by comparing the different energies of the incident light and the scattered photons.

The observation of the vibrational Raman spectrum of a molecule depends on a change in the molecules polarizability rather than its dipole moment during the vibration of the atoms. Raman spectrometers are similar to Infrared Spectrometers (IR) in a way that both measure the vibrational energies of the molecules in a sample. As a result, Infrared and Raman spectra provide complementary information and between the two techniques, all vibrational transitions can be observed. This combination of techniques is essential for the measurement of all the vibrational frequencies of the molecules of high symmetry that do not have permanent dipole moments. Since Raman scattering is different from infrared absorption, the two methods of spectroscopy are often used to provide complementary data.

Most incident photons are scattered by the sample with no change in frequency. To enhance the observation of the radiation, the scattered radiation is observed perpendicular to the incident beam. To provide high intensity incident radiation and to enable the observation of lines, Raman spectrometers are used as a source.

Raman spectrometers often use lasers, the most typical being an argon ion laser. A laser spectrometer offers many benefits including focused, high power excitation of the tested substance, which results in a high incidence of light scattering. Because the Raman Effect measures the difference between scattered and incident light, Raman spectrometers are particularly useful in gathering data from a small section of a sample. Consequently, Raman spectrometers are being used to develop confocal microscopy techniques. The incident laser radiation of the Raman spectrometer is focused with a microscopic objective on a point in the sample. The resulting Raman spectrum contains data almost exclusively from a point within the sample.

This article is issue in public interest by Applied Instrument Technologies (AIT) is the process analytical technology business within Hamilton Sundstrand, a United Technologies company. AIT delivers process analytical technology solutions to the leading companies of the world. We design and manufacture robust process development and on-line analyzers for quantitative and qualitative analysis.

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