What are the uses of analytical spectroscopic techniques in chemistry

There is no denying the fact that analytical spectroscopic techniques have multiple uses in chemistry. Whether it be in the research and development sector, in the industry, or our everyday lives, spectroscopy is a chemist’s survival kit. Now before heading onto the many different uses of spectroscopy, here is a quick revision of what is spectroscopy and its basic working principle.

What is spectroscopy

Spectroscopy is a general term that refers to the study of the interaction of electromagnetic radiation with matter. The electromagnetic spectrum consists of radiations having an electric and a magnetic field oscillating perpendicular to the direction of propagation. Different chemical molecules interact differently with specific regions of the electromagnetic spectrum in terms of light absorbance, emittance, transmittance, and scattering. Based on this interaction, the nature, structure, and identity of a specific chemical compound are determined.

Chemical molecules interact with radiant energy and undergo electronic, vibrational, and/or rotational energy changes based on the type of spectroscopic technique used. In addition to that, magnetically active nuclei such as ¹H nuclei and/or ¹³C nuclei present in a chemical compound can also change their spin energy state by absorbing electromagnetic energy. In all cases, the goal is to obtain some structural information about the targeted molecules.

Why is spectroscopy important

There are different types of analytical spectroscopic techniques. The most widely used spectroscopic techniques include ultraviolet-visible (UV-Vis) spectroscopy, infrared (IR) spectroscopy, atomic absorption spectroscopy (AAS), light scattering spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Each spectroscopic technique is important to serve a specific application in the industry and academia. Let’s find out how.

The uses of analytical spectroscopic techniques in research and development

• The foremost and the most important application of spectroscopic techniques is their ability to give detailed information about the atomic and molecular structure of a chemical substance as well as its electronic arrangement.
• IR spectroscopy is the most widely used spectroscopic technique for characterizing newly synthesized chemical compounds in the laboratory.
• Another powerful technique for structure determination in the R and D sector is nuclear magnetic resonance (NMR) spectroscopy especially proton NMR. It gives the scientist a complete structural profile of the tested compound.
• Spectroscopic instruments can be coupled as detectors with chromatographic setups such as GC and HPLC. It helps in determining the identity and the amount of a chemical substance eluting out of the column.
• A mass spectrometer coupled with a gas chromatographic column allows the determination of relative atomic mass and percentage abundance of the different isotopes of an element present in the tested sample.
• Mass spectroscopy (MS) is used in geochemistry for determining the age of organic matter.

The uses of analytical spectroscopic techniques in industry

• Infra-red spectroscopy including FTIR spectroscopy is specifically important in the pharmaceutical sector. It gives structural information about newly synthesized drugs, therapeutic agents, polymers, and medicinal materials. Thus, ensuring quality assessment and quality control in the industrial sector.
• Toxic enantiomers of useful medicinal drugs can be readily detected using IR spectroscopy.
• Trace toxins and adulterants present in a drug, or a food material can be detected.  To ensure the purity of an unknown compound, its fingerprint region recorded on the IR spectrum should exactly superimpose on that of the pure compound.
• The progress of a chemical reaction can be traced mid-way with the help of analytical spectroscopic techniques.
• FTIR spectroscopy is an extremely efficient technique that allows structural elucidation of inorganic industrial compounds including glass, minerals, metal oxides, etc.

• In the polymer industry, analytical spectroscopic techniques such as ¹³C-NMR spectroscopy are used to study polymer structure, polymer composition, tacticity, etc.
• Crystal structures can be studied using X-ray spectroscopy giving information such as the bond angles, bond lengths, size of atoms, size distribution as well as any defects present in the crystal.

• Spectroscopy is also important in the petrochemical industry to study the chemical composition of refined petroleum products.

The uses of analytical spectroscopic techniques in organic chemistry

• Analytical spectroscopic techniques help study the structures of complex organic molecules.
• Conjugated organic molecules and aromatic compounds strongly absorb ultraviolet-visible radiation so they can be studied using UV-Vis spectroscopy. The presence and/or absence of chromophores (C=O, N=N, C=C) and auxochromic (O-H, NH₂, SH) functional groups control conjugation present in an organic compound thus strongly affecting its UV-Vis spectrum.
• Thus, the changes that take place in organic molecules during a chemical reaction can be effectively examined via spectroscopic analysis. Beer Lambert’s law can be further applied to quantify the amount of a certain chemical species present in the tested sample. In this way, spectroscopy provides detailed information on the chemical composition of an unknown sample mixture.

The uses of analytical spectroscopic techniques in biochemistry

• Structural arrangement of atoms in biological molecules such as proteins, carbohydrates, and nucleic acids (DNA and RNA) can be studied using X-ray spectroscopy. This helps in disease diagnosis.
• Biological molecules can be tagged with fluorescent materials and analyzed via fluorescence spectroscopy. 
• Naturally fluorescent bioactive compounds such as plant pigments, aflatoxins, antioxidants, and vitamins can be studied using luminescence spectroscopy.
• The physiological stage of a plant and environmental stress (pH, temperature) present on it can change the fluorescing ability of the plant pigment such as chlorophyll so fluorescence spectroscopy can also be used to examine such changes.
• Radiant energy scattered from different regions in a biological molecule such as its nucleus and mitochondria differs. In this way, light scattering spectroscopy can detect malignancy in tumor-affected body tissues.
• Atomic emission spectroscopy (AES) also called flame photometry is a versatile spectroscopic technique that can determine alkaline earth metal atoms. So, calcium deficiency can be detected in living organisms using AES. It can also detect metallic tracings in wounded skin.
• Structural conformations in biomolecules such as the α helix and β-pleated sheets in the secondary structure of a protein can be studied using a unique analytical spectroscopic technique called circular dichroism (CD) spectroscopy.
• Similarly, CD spectroscopy also helps study protein-ligand binding and protein mutation to detect diseases in the field of biochemistry.
• MRI scanning of body tissues is based on the principles of NMR spectroscopy. Radiowaves can easily penetrate soft body tissues such as the brain tissues to determine their structure and function.

• Biochemical pathways can be studied via NMR spectroscopy based on NMR active ¹³C, ¹⁵N, ³¹P, and ¹H nuclei present in amino acids, proteins, and carbohydrates.

The uses of analytical spectroscopic techniques in everyday life

• Analytical spectroscopic techniques such as atomic absorption spectroscopy (AAS) play a vital role for scientists to keep a check on food contamination on an everyday basis.
• Using AAS, the concentration of toxic metal atoms can be readily detected in environmental samples such as river water, drinking water, agricultural soil, and fertilizers.

Here is a detailed probe on the working principle and instrumentation of the 10 different spectroscopic techniques that we have talked about in this article.

You may also like to revise all your basic concepts about spectroscopy through this video.

References

1. Cuisset, A., D. S. Venables, X. Gao and H. Aroui (2016). “Applications of Spectroscopy in Environmental Monitoring of Gases and Aerosols.” Journal of Spectroscopy 2016: 2575782.

2. Perkampus, H.-H. (2013). UV-VIS Spectroscopy and its applications. Springer

3. Silva, J. C. D., A. Queiroz, A. Oliveira and V. Kartnaller (2017). Advances in the Application of Spectroscopic Techniques in the Biofuel Area over the Last Few Decades.