Question

Which technique is commonly used to study polymorphism?

• A. Flame photometry
• B. IR spectroscopy
• C. X-ray diffraction
• D. UV spectroscopy

Hint:

Polymorphism is the ability of a solid drug to exist in more than one crystalline form.

Answer 1

The Correct Option is C

Concept:
Polymorphism is the ability of a solid drug to exist in more than one crystalline form. Different polymorphs have the same chemistry but different internal crystal arrangements, which can change solubility and stability — so we need a technique that reveals the crystal lattice.

Step 1: X-ray diffraction (XRD) is the gold-standard tool here. When X-rays hit a crystal, the regularly spaced atoms diffract them into a unique pattern that acts like a fingerprint of that specific crystal arrangement. Different polymorphs give different diffraction patterns, so XRD clearly distinguishes them.

Step 2: The others are less suitable as the primary method — flame photometry measures metal ions, while IR and UV spectroscopy probe molecular bonds and chromophores rather than the overall crystal lattice. They may give supporting evidence but do not directly characterize crystal structure the way XRD does.

Answer: Option (3) — X-ray diffraction is commonly used to study polymorphism. (3)