*2.8.1 Instrumentation*

**Figure 17** illustrates the basic components of an ESR spectrometer. Fields of 50–500 mT, required for accurate work are generated by electromagnets. Auxiliary sweep generators with a capacity of 10–100 mT are also provided. Monochromatic microwave radiation might be readily obtained by using a klystron oscillator.

**Figure 17.** *Components of NMR spectrometer.*

**Figure 18.**

*Basic components of an electron spin resonance spectroscopy.*

Samples for ESR must be solids. Biological samples which contain a large amount of water are therefore frozen in liquid nitrogen before ESR experiment. **Figure 18** shows the Basic components of an ESR [7].

### *2.8.2 Principle*

The principle of ESR spectroscopy is based on the fundamental properties of electrons. An unpaired electron in atoms or molecules possesses paramagnetic character and shows both magnetic moment and angular momentum. In an external magnetic field, the spin magnetic moment aligns parallel or antiparallel to the field, and the spinning electrons are split or divided into high and low energy states. These split electrons form spectral lines, and they can be determined [44].

### *2.8.3 Applications*


### **3. Conclusion**

Spectroscopy is one of the most important analytical tools for the analysis of various compounds in various fields including chemistry, physics, biology, agriculture, engineering, and medicine. This is working with different principles which are projected through various instrumentation techniques like UV-visible spectrophotometry, IR spectroscopy, Raman spectroscopy, NMR spectroscopy and ESR spectroscopy. The applications of these techniques are providing very useful

*Spectroscopy and Spectrophotometry: principles and Applications for Colorimetric and Related… DOI: http://dx.doi.org/10.5772/intechopen.101106*

information to the teachers, students, and researchers. These analytical methods are nondestructive, consistent, and reliable and require no or very little sample preparation. We can apply these methods to solid, liquid, and powdered samples. They can be used for a wide range of elemental analysis and provide detection limits at the sub-ppm level concentrations easily and simultaneously. Therefore, the spectrophotometric techniques are very useful in elementary analysis in all most all fields by providing reliable information about elements to be analyzed.
