Laboratory analysis by RAMAN Spectroscopy

Raman spectroscopy is an analytical technique used to identify and characterise molecules. It measures changes in the inelastic scattering of monochromatic light, i.e. when a photon interacts with a molecule and causes it to vibrate. This interaction produces an optical signal that contains information about the molecular structure, such as bond strength, molecular symmetry and conformation. By deciphering this signal, Raman analysis obtains information about the composition of the sample being analyzed.

Raman spectroscopy has become increasingly important for many different applications due to its ability to provide rapid and reliable analysis without damaging or altering samples, making it ideal for life science research and quality control and assurance testing in industry. The technique also provides information on the crystallinity, purity, phase and homogeneity of the sample. By combining various spectroscopic techniques such as infrared spectroscopy, X-ray diffraction and thermogravimetric analysis with RAMAN spectroscopy, researchers can obtain more detailed structural information about the analyzed sample. RAMAN analysis is a powerful tool for research in fields such as materials science and biochemistry. In addition to laboratory applications, Raman spectroscopy is also used for clinical diagnosis and space exploration.

Raman spectroscopy is also advantageous because of its portability; it requires minimal sample preparation compared to other analytical techniques and can be performed using portable instruments. It is therefore ideal for field work or on-site measurements, as the standard operating conditions are very good.

Raman spectroscopy plays an important role in many industries and can be used to analyse a wide range of sample types. Industries such as pharmaceuticals, food and beverage, cosmetics, materials science and biochemistry are just some of the areas that benefit from this technology. Raman analysis allows researchers to quickly identify unknown compounds or confirm molecular structures in a variety of samples. Raman spectroscopy is useful for characterising catalysts and studying chemical reactivity. Its portability makes it ideal for field work or on-site measurements. The use of Raman spectroscopy in quality control and quality assurance testing has increased dramatically in recent years due to its accuracy, reliability and cost effectiveness.

Raman spectroscopy is based on the inelastic scattering of monochromatic light. When a sample is illuminated by a laser beam, certain particles interact with the molecules present and cause them to vibrate. This vibration produces an optical signal that contains information about the molecular structure. By analysing this signal, it is possible to obtain information about the composition and properties of the sample being analysed. The Raman spectrum produced by this process can be used to identify unknown compounds or confirm molecular structures. The use of filters and software algorithms allows weak signals to be amplified and background noise to be reduced, leading to more accurate results. Finally, data analysis techniques such as principal component analysis are used to interpret complex Raman spectra.

L'analyse Raman est largement utilisée dans le secteur pharmaceutique pour ses capacités de caractérisation rapide et non destructive. Voici ses principales applications :

> Identification des matières premières : Pour assurer la qualité des médicaments.

> Contrôle de qualité : Détecte les impuretés et confirme la composition chimique des produits finis.

> Analyse des formes posologiques : Examine la distribution des ingrédients actifs dans diverses formes comme les comprimés et les gélules.

> Développement de formulations : Optimise les formulations en analysant les interactions entre composants.

> Étude de la stabilité : Surveille les changements chimiques des médicaments sous différentes conditions de stockage.

Ces utilisations font de l'analyse Raman un outil essentiel pour améliorer la sécurité et l'efficacité des produits pharmaceutiques.

Raman analysis is highly versatile and can be carried out on a wide variety of samples and materials in many fields:

• Crystals and minerals: Used to study crystal composition and structure.
• Pharmaceuticals: As mentioned above, for raw material identification, quality control and dosage form analysis.
• Polymer materials: Analysis of the chemical and structural properties of plastics and other polymers.
• Nanomaterials : Assessment of the composition and properties of nanotubes, nanoparticles, etc.
• Semiconductor materials: Analysis of the structure and defects of materials used in electronics.
• Chemicals: Monitoring of chemical reactions, identification of pure chemical compounds or mixtures.

Thanks to its non-destructive approach and its ability to provide detailed information on chemical composition, Raman spectroscopy is applicable to almost all types of materials.

Raman analysis on metals is possible but complex due to the specific optical characteristics of these materials. Metals reflect light strongly, which can be problematic for Raman spectroscopy as much of the laser radiation used is reflected back rather than scattered in a way that is useful for analysis.

In addition, metals tend to produce a strong fluorescence signal when exposed to the laser, which can mask the often weaker Raman signal. Another problem is localised heating of the sample due to laser absorption, which can alter the results of the analysis. Despite these challenges, specific techniques and instrument configurations can be used to minimise these effects and enable efficient Raman analysis of metallic samples.

The choice between Raman spectroscopy and FTIR depends on the sample and the type of analysis. FTIR is best suited to polar materials such as proteins and plastics with O-H bonds, but water can interfere. Raman is ideal for non-polar substances, carbon structures (graphite, graphene), and polymers, and allows analysis of aqueous samples without complex preparation.

• Raman spectroscopy is used to perform qualitative analyses to determine the chemical composition of a sample.
• Raman spectrometry is used to perform quantitative analyses to measure the concentrations of components present in a sample.
• Raman microscopy is used to create detailed chemical maps on a microscopic scale, useful for studying complex samples such as composites, polymers or nanomaterials.

Raman spectroscopy is based on the principle of inelastic light scattering, known as the Raman effect. When a monochromatic laser beam is directed onto a sample, most of the light is elastically scattered (Rayleigh scattering) without any change in energy. However, a small fraction of the light interacts with the molecular vibrations of the sample, causing a slight energy shift in the scattered light. These energy shifts correspond to the specific vibrations of the chemical bonds in the molecules, making it possible to construct a unique spectrum for each material. This non-destructive method is invaluable for identifying chemical composition, studying molecular structures and analysing a variety of materials, such as polymers, crystals, and organic and inorganic compounds.

Raman spectroscopy is used in a variety of industrial contexts and sectors because of its ability to provide detailed, non-destructive information about the chemical composition and molecular structure of materials.

In the pharmaceutical industry, it is used for analysis of active ingredients and quality control of drugs.

In the materials sector, it is used to study polymers, composites and nanomaterials to check their uniformity and properties.

The petrochemical industry uses this technique to analyse hydrocarbons and catalytic reactions.

Raman spectroscopy addresses a range of industrial problems, providing precise quality control and detecting impurities, particularly in the pharmaceutical and cosmetics sectors.

It checks the homogeneity of materials, studies composites and nanomaterials to optimise their properties, and characterises chemical reactions in the development of new products.