DSS (NMR standard) explained

Sodium trimethylsilylpropanesulfonate (DSS) is the organosilicon compound with the formula (CH₃)₃SiCH₂CH₂CH₂SO₃⁻Na⁺. It is the sodium salt of trimethylsilylpropanesulfonic acid. A white, water-soluble solid, it is used as a chemical shift standard for proton NMR spectroscopy of aqueous solutions.^[1] The chemical shift, specifically the signal for the trimethylsilyl group, is relatively insensitive to pH.^[2]

The proton spectrum of DSS also exhibits resonances at 2.91 ppm (m), 1.75 ppm (m), and 0.63 ppm (m) at an intensity of 22% of the reference resonance at 0 ppm.

Alternatives

Sodium trimethylsilyl propionate (TSP) is a related compound used as an NMR standard. It uses a carboxylic acid instead of the sulfonic acid found in DSS to confer water solubility. As a weak acid, TSP is more sensitive to changes in pH.

4,4-Dimethyl-4-silapentane-1-ammonium trifluoroacetate (DSA) has also been proposed as an alternative, to overcome certain drawbacks of DSS.^[3]

Notes and References

1. 10.1351/pac200880010059. Further Conventions for NMR Shielding and Chemical Shifts (IUPAC Recommendations 2008). Pure and Applied Chemistry. 80. 2. 59–84. 2008. Harris. Robin K.. Becker. Edwin D.. Cabral De Menezes. Sonia M.. Granger. Pierre. Hoffman. Roy E.. Zilm. Kurt W.. 2008JMagR.191..340.. free.
2. 10.1016/0022-2364(77)90104-4. pH Dependence of Internal References. Journal of Magnetic Resonance . 26. 3. 527–528. 1977. De Marco. Antonio. 1977JMagR..26..527D.
3. DSA: A New Internal Standard for NMR Studies in Aqueous Solution . James S.. Nowick. Omid. Khakshoor. Mehrnoosh. Hashemzadeh. Justin O.. Brower . . 2003 . 5 . 19 . 3511–3513 . 10.1021/ol035347w . 12967312.