Infrared (IR) Spectrometry and Mass Spectrometry (MS) are two significant analytical techniques in environmental chemistry, used extensively for the detection, identification, and quantification of pollutants and environmental contaminants. Both these methods offer unique advantages in the analysis of complex environmental samples such as air, water, soil, and biological materials. Here, we will explore the principle, instrumentation, and environmental applications of each technique in detail.

---

### Infrared (IR) Spectrometry

#### Principle of IR Spectrometry

Infrared spectrometry is based on the absorption of infrared radiation by molecules. When IR radiation passes through a sample, certain frequencies of the radiation are absorbed by the sample, causing molecular vibrations such as stretching, bending, or twisting of chemical bonds. Each chemical bond or functional group absorbs IR radiation at a characteristic frequency, producing a spectrum that can be used to identify the molecular structure of a compound.

There are two types of IR spectroscopy commonly used:
- Near-IR (NIR): 14000–4000 cm⁻¹
- Mid-IR: 4000–400 cm⁻¹
- Far-IR: 400–10 cm⁻¹

The mid-IR region is most commonly used for qualitative analysis of organic compounds because it contains the fingerprint region unique to each compound.

#### Instrumentation of IR Spectrometry

1. IR Radiation Source:
   - A stable and intense IR radiation source is used.
   - Common sources include Nernst glower (zirconium oxide) and globar (silicon carbide rod).

2. Sample Handling