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🌈 Structure Identification · Method

Infrared Spectroscopy (IR)

Read functional-group fingerprints fast
🎯 Difficulty ★★☆ Medium Duration About 20–40 min 🎯 Use Detect characteristic functional-group absorptions to help confirm or compare structures.
📖 Principle
Each bond absorbs unique IR frequencies, leaving a distinctive fingerprint.
Below are 3 steps. Open each to see how to do it and add products to your shared list.

📋 Workflow

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1

Prepare the sample

10 min
Press a KBr pellet for solids, a liquid film for liquids, or use ATR for microsampling.
💡 Tip ATR needs no pellet—fast and easy
⚠️ Caution KBr is hygroscopic; press pellets dry
🧪 Materials for this step (click to shop by spec/brand)
2

Acquire the spectrum

5–15 min
Place the sample in the IR, acquire 4000–400 cm⁻¹ full scan with background subtraction.
💡 Tip Subtract blank to remove air/water
⚠️ Caution A sample too thick saturates to flat peaks
🧪 Materials for this step (click to shop by spec/brand)
3

Interpret characteristic absorptions

15 min
Match diagnostic regions for C=O, O–H, N–H, C≡N etc., and assign functional groups.
💡 Tip Sharp strong band near 1700–1600 often = carbonyl
⚠️ Caution A broad band may fold several H-bond vibrations
🧪 Materials for this step (click to shop by spec/brand)

⚠️ 5 Common Beginner Mistakes

  • Water from moist KBr masks O–H
  • Thick sample saturates key bands
  • No background subtract mixes CO₂/H₂O
  • Misreading fingerprint noise as peaks
  • IR alone can't settle a full structure

❓ FAQ

+Can IR confirm structure?
Good for groups; usually combine with MS/NMR.
+ATR vs pellet?
ATR is fast/non-destructive; pellet gives stronger signal.
+Why a broad water band?
Hygroscopic KBr/sample adds a broad 3000–3500 band.

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Data authenticity: Product categories from JW Supply Chain standard taxonomy; method→step→product connected. Last updated: 2026-08-23 · v3.0