Class 2 Residual Solvents

Analytical testing dots Class 2 Residual Solvents

Residual solvents are separated into three classes based on risk assessment or their potential toxicity level. Because of its inherant toxicities, class 2 residual solvents should be limited in drug substances, excipients, and drug products.

The following is a list of class 2 residual solvents as well as their acceptable levels as adopted by the International Conference on Harmonization (ICH Q3C).

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USP Class 2 Residual Solvents List

Solvent PDE (mg/day) Concentration limit (ppm)
Acetonitrile  4.1 410
Chlorobenzene  3.6 360
Chloroform  0.6 60
Cyclohexane  38.8 3880
1,2-Dichloroethene 18.7 1870
1,2-Dimethoxyethane 1 100
N,N-Dimethylacetamide 10.9 1090
N,N-Dimethylformamide 8.8 880
1,4-Dioxane 3.8 380
2-Ethoxyethanol 1.6 160
Ethylene glycol 6.2 620
Formamide 2.2 220
Hexane 2.9 290
Methanol 30 3000
2-Methoxyethanol 0.5 50
Methylbutylketone 0.5 50
Methylcyclohexane 11.8 1180
Methylene chloride 6 600
N-Methylpyrrolidone 5.3 530
Nitromethane 0.5 50
Pyridine 2 200
Sulfolane 1.6 160
Tetrahydrofuran 7.2 720
Tetralin 1 100
Toluene 8.9 890
Trichloroethylene 0.8 80
Xylene* 21.7 2170

* Usually 60% m-xylene, 14% p-xylene, 9% o-xylene with 17% ethyl benzene

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