Regulatory and process considerations for switching to dimethyl sulfoxide
Dimethyl sulfoxide (DMSO, CAS 67-68-5) is a highly polar, water-miscible dipolar aprotic solvent with a relatively high boiling point (189 °C) and low acute toxicity. As EU regulation tightens around the nitrogen-containing solvents N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF), manufacturers in battery, polymer, and pharmaceutical processing are increasingly evaluating DMSO as a substitute. This article reviews the regulatory drivers and the practical considerations for substitution.
In this article
Regulatory Pressure on NMP and DMF
Both NMP and DMF are classified as toxic to reproduction, Category 1B (H360D), under the EU CLP Regulation, and both now face supply-chain restrictions under REACH.
NMP (CAS 872-50-4) is listed on the ECHA Candidate List as a Substance of Very High Concern (SVHC) and is restricted under REACH Annex XVII, entry 71. Since 9 May 2020, NMP at concentrations of 0.3% w/w or above may not be placed on the market unless derived no-effect levels (DNELs) for workers — 14.4 mg/m³ for long-term inhalation exposure and 4.8 mg/kg bw/day for dermal exposure — are included in the chemical safety report and safety data sheet.
DMF (CAS 68-12-2) carries the same reproduction-toxicity classification, plus acute toxicity (H312, H332) and serious eye irritation (H319). Under REACH Annex XVII, entry 76, DMF as a substance or in mixtures at 0.3% w/w or above may not be placed on the market from 12 December 2023 unless worker DNELs (6 mg/m³ inhalation; 1.1 mg/kg bw/day dermal) are documented. DMF has also been on the SVHC Candidate List since 19 December 2012. For transport, DMF is regulated as UN 2265, Class 3 flammable liquid (packing group III) under ADR, IMDG and RID, adding logistics and compliance cost.
| Parameter | NMP | DMF |
|---|---|---|
| CLP classification | Repr. 1B (H360D) | Repr. 1B (H360D); Acute Tox. 4 (H312, H332); Eye Irrit. 2 (H319) |
| ECHA SVHC Candidate List | Listed | Listed (19 December 2012) |
| REACH Annex XVII | Entry 71 — requirements apply at ≥0.3% w/w from 9 May 2020 | Entry 76 — requirements apply at ≥0.3% w/w from 12 Dec 2023 |
| Worker DNELs (inhalation; dermal) | 14.4 mg/m³; 4.8 mg/kg bw/day | 6 mg/m³; 1.1 mg/kg bw/day |
| Transport (ADR/IMDG) | Not classified as dangerous goods | UN 2265, Class 3, PG III |
NMP and DMF manufacture and use at or above the threshold also require appropriate risk-management measures and operating conditions that keep worker exposure below the specified DNELs. The 0.3% threshold is not a blanket ban or a universal concentration limit. Sector-specific transition periods have now elapsed.
Table 1: EU regulatory status of NMP and DMF
The DMSO Regulatory Profile
Supplier EU safety data sheets typically report that pure DMSO does not meet CLP classification criteria, including reproductive toxicity. This differs from the harmonised reproductive-toxicity classifications of NMP and DMF. Always check the current SDS for the actual product, impurities and formulation, and the applicable REACH obligations.
DMSO is not hazard-free: it is combustible, can irritate the eyes and readily penetrates the skin, potentially carrying dissolved chemicals into the body. Appropriate gloves, eye protection, ventilation and handling procedures remain necessary. Product-specific SDS information should determine storage, transport and waste-management arrangements.
| Parameter | DMSO | NMP | DMF |
|---|---|---|---|
| CAS number | 67-68-5 | 872-50-4 | 68-12-2 |
| Boiling point (1 atm) | 189 °C | 202 °C | 153 °C |
| CLP reproduction toxicity | Not classified | Repr. 1B | Repr. 1B |
| SVHC / relevant REACH restriction | Check current SDS and ECHA lists | SVHC + Entry 71 | SVHC + Entry 76 |
| Transport classification | None | None | UN 2265, Class 3 |
Table 2: DMSO compared with NMP and DMF
Substitution in Practice
DMSO is a candidate solvent for selected polymer, chemical-synthesis and electronics processes. However, replacing NMP or DMF is a process-development decision rather than a direct one-for-one swap. Solubility, reaction selectivity, viscosity, moisture sensitivity and compatibility with equipment and seals must be assessed for the actual formulation.
Its boiling point of approximately 189 °C is higher than DMF’s approximately 153 °C, which changes drying conditions, recovery energy and residual-solvent removal. Validate recovery, impurity accumulation, product quality and operating safety at laboratory and pilot scale before production. A different hazard classification does not remove the need for an occupational-exposure assessment.
When requesting a DMSO sample, share your current solvent, application, purity and moisture requirements, and the main constraints in your process.
References
- Commission Regulation (EU) 2018/588 — NMP, REACH Annex XVII entry 71
- Commission Regulation (EU) 2021/2030 — DMF, REACH Annex XVII entry 76
- ECHA Candidate List — N,N-dimethylformamide
- ILO International Chemical Safety Card 0457 — DMF
- ILO International Chemical Safety Card 0459 — DMSO
- Thermo Fisher Scientific — DMSO EU safety data sheet, revised 2 May 2025
For the physical-property and work-up differences to check during screening, see DMSO vs DMF: Properties, Work-up and Solvent Selection.