Problems with Raman Spectroscopy

In summary: Hello, the raw material has a very low fluorescence signal, but there is no way to measure it with the equipment we have. The material is very thick and we need to use a long exposure time to obtain a signal. No, we do not have a big slit or a wide slit.
  • #1
GuiHn
3
0
Hello,

Recently I had a problem in the analysis of a raw material called Propranolol HCl, when performing Raman identification for the specific batch the obtained spectrum does not generate signal and, consequently, identity of the material.

By testing other techniques like infrared and NMR, I got the results without problems.

It turns out that I need to understand why the problem occurs only in Raman spectroscopy. Searching the internet did not find anything that could explain, since the problem happens only with this lot in question, other lots of the same product provide perfect spectra.

Anyone who has good knowledge of the technique could help me?

Thank you.
 
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  • #2
I'm far from an expert in the field, but my first intuition is to test the Raman spectrometer. Have you tried producing other spectra, such as for ethanol or acetone, which you probably have in your lab?
 
  • #3
DrClaude said:
I'm far from an expert in the field, but my first intuition is to test the Raman spectrometer. Have you tried producing other spectra, such as for ethanol or acetone, which you probably have in your lab?
Hello, thanks for the help. In the laboratory we have a polystyrene standard that is made before any reading to evaluate the equipment. In addition, in the same equipment we made other batchs of the same product that had the spectra with normal intensity, only for this batch that we did not obtain spectra with product identity.
Initially I imagined that it could be a physical characteristic of the batch, but the granulometry and other aspects are similar with the other batchs that approved in the identification
 
  • #4
That's strange. What wavelength is the laser?
 
  • #5
HAYAO said:
That's strange. What wavelength is the laser?
Hello, the wavelenght is the standart of equipament 785nm, I can't change this value.
I've been thinking that this raw material has a smaller fluorescence signal, but I don't have the equipment to prove it.
 
  • #6
Some material have low raman intensivity. Do you have big thickness this material ? Do you have long exposition? Can you growing optical power up or wide slit?
 

Related to Problems with Raman Spectroscopy

1. What are the limitations of Raman spectroscopy?

Raman spectroscopy has limitations in terms of sensitivity, as it is not as sensitive as other spectroscopic techniques such as infrared spectroscopy. It is also not suitable for analyzing samples that are highly fluorescent or have low concentrations of the analyte. Additionally, Raman spectroscopy requires a relatively long acquisition time, making it less suitable for real-time analysis.

2. How does Raman spectroscopy differ from infrared spectroscopy?

Raman spectroscopy is based on the inelastic scattering of light, while infrared spectroscopy is based on the absorption of light. This means that Raman spectroscopy provides information about the vibrational and rotational energies of a molecule, while infrared spectroscopy provides information about the bond energies. Additionally, Raman spectroscopy does not require the use of a reference sample, making it more versatile for analyzing a wider range of samples.

3. What are some common sources of error in Raman spectroscopy?

One common source of error in Raman spectroscopy is fluorescence interference, which occurs when the sample emits light at the same wavelength as the Raman signal. This can be mitigated by using a longer wavelength excitation source or by using a different analytical technique. Other sources of error include sample preparation, instrument calibration, and sample degradation.

4. Can Raman spectroscopy be used for quantitative analysis?

Yes, Raman spectroscopy can be used for quantitative analysis. However, it is not as accurate as other techniques such as mass spectrometry or gas chromatography. This is due to the fact that the Raman signal intensity is not directly proportional to the concentration of the analyte, and there can be interference from other molecules in the sample.

5. What are some applications of Raman spectroscopy in scientific research?

Raman spectroscopy has a wide range of applications in various fields, including material science, pharmaceuticals, and biotechnology. It is commonly used for identifying and characterizing molecules, studying chemical reactions, and monitoring biological processes. Raman spectroscopy is also used in forensic analysis, environmental science, and art conservation.

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