DSS (NMR Standard)
Encyclopedia
DSS is a chemical compound
used in proton- and carbon-related NMR
spectroscopy as a calibration standard, similar to tetramethylsilane
(TMS), but with much higher water solubility. Whereas TMS is the most common NMR standard used in organic solvents such as chloroform
or benzene
, DSS or its sodium salt is more often used for protein experiments in water.
The low electronegativity
of the silicon
shields the nine identical methyl protons. The result is a high intensity proton signal further upfield (at lower chemical shift
) than almost all peaks found in naturally occurring organic molecules. The resulting standard peak is easily identified as such and set to chemical shift 0.0.
The proton spectrum of DSS also exhibits minor peaks at 3.1 ppm (triplet), 1.9 ppm (pentet), and 0.8 ppm (triplet) at an intensity of 22% of the reference peak at 0 ppm. However, these peaks appear much smaller than 22% of the height of the reference singlet because of their width (i.e. multiplicity). If these peaks pose a problem, a deuterated version of DSS is available at much higher cost.
(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 weaker acid, TSP is more prone to be affected by sample pH.
4,4-Dimethyl-4-silapentane-1-ammonium trifluoroacetate (DSA) has also been proposed as an alternative, to overcome certain drawbacks of DSS.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
used in proton- and carbon-related NMR
NMR
NMR may refer to:Applications of Nuclear Magnetic Resonance:* Nuclear magnetic resonance* NMR spectroscopy* Solid-state nuclear magnetic resonance* Protein nuclear magnetic resonance spectroscopy* Proton NMR* Carbon-13 NMR...
spectroscopy as a calibration standard, similar to tetramethylsilane
Tetramethylsilane
Tetramethylsilane is the chemical compound with the formula Si4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral...
(TMS), but with much higher water solubility. Whereas TMS is the most common NMR standard used in organic solvents such as chloroform
Deuterated chloroform
Deuterated chloroform , is an isotopologue of chloroform in which the hydrogen atom is replaced with a deuterium isotope . Deuterated chloroform is a common solvent used in NMR spectroscopy of organic molecules....
or benzene
Deuterated benzene
Deuterated benzene , is a form of benzene in which the hydrogen atom is replaced with deuterium isotope . Deuterated benzene is a common solvent used in NMR spectroscopy....
, DSS or its sodium salt is more often used for protein experiments in water.
The low electronegativity
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
of the silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
shields the nine identical methyl protons. The result is a high intensity proton signal further upfield (at lower chemical shift
Chemical shift
In nuclear magnetic resonance spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard. Often the position and number of chemical shifts are diagnostic of the structure of a molecule...
) than almost all peaks found in naturally occurring organic molecules. The resulting standard peak is easily identified as such and set to chemical shift 0.0.
The proton spectrum of DSS also exhibits minor peaks at 3.1 ppm (triplet), 1.9 ppm (pentet), and 0.8 ppm (triplet) at an intensity of 22% of the reference peak at 0 ppm. However, these peaks appear much smaller than 22% of the height of the reference singlet because of their width (i.e. multiplicity). If these peaks pose a problem, a deuterated version of DSS is available at much higher cost.
Alternatives
Trimethylsilyl propionateTrimethylsilyl propionate
Trimethylsilyl propanoic acid is a chemical compound containing a trimethylsilyl group. It is used as internal reference in the NMR spectrum nuclear magnetic resonance for aqueous solvents . For that use it is often deuterated...
(TSP) is a related compound used as an NMR standard. It uses a carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
instead of the sulfonic acid
Sulfonic acid
Sulfonic acid usually refers to a member of the class of organosulfur compounds with the general formula RS2–OH, where R is an alkyl or aryl. The formal part of acid, HS2–OH, are formally derivatives of the "parent" inorganic compound with the formula HSO2.-Preparation:Sulfonic acid is...
found in DSS to confer water solubility. As a weaker acid, TSP is more prone to be affected by sample pH.
4,4-Dimethyl-4-silapentane-1-ammonium trifluoroacetate (DSA) has also been proposed as an alternative, to overcome certain drawbacks of DSS.