By admin 
Classification of Residual Solvents:
The International Conference on Harmonisation (ICH) Q3C(R6) guideline classifies residual solvents into three categories:
Class 1 Residual Solvents:
Known human carcinogens or strongly suspected human carcinogens
Examples:
1. Benzene
2. Carbon tetrachloride
3. 1,4-Dioxane
4. Chloroform
5. Ethylene oxide
Class 2 Residual Solvents:
Non-carcinogenic, but potentially toxic
Examples:
1. Acetone
2. Ethyl acetate
3. Ethanol
4. Isopropanol
5. Methanol
6. Toluene
7. Xylene
8. Dichloromethane (DCM)
9. N-Methylpyrrolidone (NMP)
Class 3 Residual Solvents:
Low-toxicity solvents
Examples:
1. Acetic acid
2. Ethyl ether
3. Glycerin
4. Isobutanol
5. Propylene glycol
Examples of Residual Solvents:
1. Acetone
2. Benzene
3. Chloroform
4. Dichloromethane (DCM)
5. Ethanol
6. Ethyl acetate
7. Isopropanol
8. Methanol
9. N-Methylpyrrolidone (NMP)
10. Toluene
11. Xylene
Limit Concentrations:
1. Class 1: Not detectable
2. Class 2: 10-50 ppm (depending on solvent)
3. Class 3: 50-5000 ppm (depending on solvent)
Regulatory Requirements:
1. ICH Q3C(R6)
2. FDA Guidance
3. EU GMP Annex 15
4. USP <467>
Understanding residual solvent classification and testing ensures pharmaceutical product quality and safety.
Key Takeaways:
1. Residual solvents are classified into three categories.
2. Class 1 solvents are known human carcinogens.
3. Class 2 solvents are non-carcinogenic but potentially toxic.
4. Class 3 solvents have low toxicity.
5. Testing methods include GC, LC-MS, and NMR.