Fourier Transform Infrared Spectroscopy (FTIR) - QnA

Questions and Answers:

1. What is measuring unit of IR Spectroscopy?

Answer: cm⁻¹

2. Formula of wavenumber

Answer: Wavenumber = 1 / Wavelength

3. Principle of IR Spectroscopy

Answer: IR Spectroscopy is based on vibrational energy level changes when IR radiation passes through a material.

IR Electromagnetic Range: 4000 cm⁻¹ – 400 cm⁻¹
4. Which test we perform in IR Spectroscopy
Answer: Identification tests

5. Region in IR Spectroscopy
Answer:

Two regions:
a. Functional group region: 4000–1400 cm⁻¹
b. Fingerprint region: 1400–400 cm⁻¹

6. How many types of vibration occur in IR Spectroscopy
Answer:

Two types of vibration occur:
a. Bending
b. Stretching

7. What is bending vibration?
Answer: Vibration in bond angle due to vibration

8. What is stretching vibration?
Answer: Vibration in bond distance

9. Types of bending vibration (4 types)
Answer:

a. Scissoring
b. Wagging
c. Rocking
d. Twisting

10. Why KBr is used in IR Spectroscopy?
Answer:

Few reasons:
a. Dipole moment zero
b. Temperature resistant substance
c. IR inactive substance (does not show peak)

11. Why water is not used in IR Spectroscopy?
Answer:

Reason:
a. Strong polar substance
b. Shows two strong peaks

12. What is the sample and KBr weight used?
Answer:

Sample: 1–2 mg
KBr: 300–400 mg

13. Which USP chapter has information about FTIR?
Answer:

Chapter Number 854

14. Which lamp is used in NIR?
Answer:

Tungsten Halogen lamp

15. Which lamp is used in MID IR?
Answer: Nernst Globar

16. Which lamp is used in FAR IR?
Answer: High pressure Mercury lamp