DMSO is hygroscopic. Keep moisture control tied to the reaction specification and an actual water measurement, rather than a fixed drying time.
In this article
Measure Before Choosing a Drying Method
Specify a Karl Fischer method and sampling procedure appropriate to the expected water level. Avoid judging dryness from clarity or a grade name.
The listed YUJI moisture limits are ≤1,000 ppm for industrial grade and ≤300 ppm for pharmaceutical and electronic grades. These are supplier specifications, not universal limits for every material sold under those names.
Control Moisture During Handling
Keep containers closed and minimize exposure during transfer and sampling. Use equipment and seals compatible with DMSO and the other substances present. A sample can gain moisture after the original COA measurement.
Molecular-sieve treatment or reduced-pressure distillation may be evaluated in a qualified procedure. Their effectiveness depends on initial water, equipment, adsorbent condition and contact time; a fixed treatment duration does not guarantee a particular ppm result.
Verify the Outcome and Compatibility
Re-test water after drying, and consider contamination or decomposition products introduced by the treatment. Select temperature and pressure from the actual equipment and process-safety assessment.
Do not use sodium hydride as a casual drying recommendation for DMSO. Documented explosion hazards make that combination unsuitable as a general handling instruction. Request pre-qualified material when drying capability is limited.
Sources and Further Reading
- Yang et al., Explosion Hazards of Sodium Hydride in DMSO, DMF and DMAc (2019)
- YUJI: Listed grade specifications and moisture limits
Further reading: DMSO Physical Properties for Process Planning; Ester Hydrolysis in Aqueous DMSO.