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Raman Spectrometer

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.

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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.

how to stabilize Tin (Sn) reading in Atomic Absorption Spectrometer (AAS)?

Interesting question....

Atomic absorption spectroscopy is an analytical technique used to determine the concentration of metal or even metals in a sample.

The sample is taken up by an apparatus into the Atomiser or Nebulizer which convert the Liquid sample into a spray.
The spray is then taken up into the Flame where the solvent evaporates leaving the dry aerosol particles.
The excitation source which can be a flame or plasma etc .... heats the particles further into their molecule, ions and Atoms .... Dissociation from molecules to their individual Atoms allows the Atoms to contribute in Absorption in energy and promote them to their excited states.

the Radiation source can be achieved from a Cathode Ray tube, which consists of an Anode and a Cathode which may be coated or made of the same element the user is attempting to identify. the emission lines coming from the cathode ray tube are less broad than the absorption peak in the flame.
background testing is used such as a second deuterium lamp to insure that there is no back round interference.

that was a simple round down .... from above we can make a list on how to maintain and stabilize Tin reading .. Instrumentally.

1) Droplet size of sample taken into nebulizer must be Uniform < 20micrometers
2) rate of feed must be constant
3) the sample must be clean ..... so it must not have any matrixes or any other interfering substances ....

Spectral interference:-
1) Overlap of emission and absorption lines (use deuterium lamp as a check)

2) Refractory oxides :- Refractory means applying a temperature greater than >600 degree to a product.
Ti can form Refractory oxides.... at these high temperatures .... so you can stabilise it by deciding how much O2 you are going to use in your excitation source or if you have to use a different excitation source .... but that comes at a cost ..... Refractory oxides can bend light which can detract the signal ...
there are so many other factors to consider ... like .
Chemical interference:- solve by elevating temperature

refractory oxides are the main complication in AAS involving Tin ....
so controlling the oxygen being inputed into the flame exitation source is one way to stabilize reading .... using a background Correction lamp .. to ensure the absorption you get is the sample doing it rather than other species, is another ....

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