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DMSO Properties and Sample Integrity
DMSO is chosen as a solvent due to its strong polarity, high boiling point, aprotic nature, versatility, and excellent solubilizing capacity. It can dissolve most aromatic and unsaturated hydrocarbons, organic nitrogen compounds, organic sulfur compounds, and many inorganic salts. It also has low toxicity, making it suitable for daily handling.
🧪 Chemical Stability and Solubility
The integrity of a sample in DMSO depends on both chemical stability and DMSO solubility, which may rely on different chemical characteristics.
- Chemical stability increases at low temperature, where potential reactions proceed more slowly.
- However, lower temperatures increase the risk of precipitation, especially when water content rises.
💧 Hygroscopic Nature of DMSO
DMSO is highly hygroscopic. When exposed to air in a typical laboratory, it will absorb water.
- It can absorb up to 30% water exposed in an environment with 50% relative humidity at 20 °C in approximately an hour
- Fortunately, our laboratories have low relative humidity (≈30% in summer and ≈10% in winter), meaning water uptake is not a major concern.
🧴 Storage Materials and Environmental Considerations
The greatest impact on compounds occurs during handling, rather than during typical storage. Still, storage conditions matter.
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Our primary storage material is polypropylene (PP).
- PP is highly resistant to DMSO but permeable to gases and water.
- This means sealed samples may accumulate water or oxygen over time.
- Permeability increases with higher temperature.
- Storage systems with humidity control reduce water uptake, but do not reduce oxygen diffusion.
❄️ Temperature Effects
Cold conditions are generally better.
- Some users avoid freezing and prefer 20 °C storage because DMSO has a melting point of 18 °C.
- However, multiple freeze–thaw cycles do not increase degradation or precipitation.
Keeping DMSO completely water‑free is very difficult. Once water content reaches 20%, the melting point drops to –30 °C, meaning:
- Solutions stored at –20 °C remain liquid.
- However, the low temperature significantly reduces chemical reactions.
- Gas permeability is lower at cold temperatures.
Methods
❄️ –20 °C Storage
We store our compounds as 10 mM DMSO solutions at –20 °C.
- Freezers with automatic defrosting reduce internal humidity.
- Freezers without this system do not necessarily accumulate humidity, as moisture instead forms frost on solid surfaces.