69889 Sigma-Aldrich

MES monohydrate

BioUltra, for molecular biology, ≥99.5% (T)

Synonym: 2-(N-Morpholino)ethanesulfonic acid, 4-Morpholineethanesulfonic acid monohydrate

  • CAS Number 145224-94-8

  • Empirical Formula (Hill Notation) C6H13NO4S · H2O

  • Molecular Weight 213.25

  •  Beilstein/REAXYS Number 6350956

  •  EC Number 224-632-3

  •  MDL number MFCD00149409

  •  eCl@ss 32129211

  •  PubChem Substance ID 329762028

  •  NACRES NA.25



Related Categories BioUltra, Molecular Biology, Molecular Biology Reagents More...
Quality Level   200
grade   for molecular biology
product line   BioUltra
assay   ≥99.5% (T)
form   powder or crystals
impurities   DNases, none detected
  Insoluble matter, passes filter test
  Phosphatases, none detected
  Proteases, none detected
  RNases, none detected
ign. residue (900 °C)   ≤0.05% (as SO4)
pH   2.5-4.0 (25 °C, 0.5 M in H2O)
useful pH range   5.5 - 6.7
pKa (25 °C)   6.1
mp   >300 °C (lit.)
solubility   H2O: 0.5 M at 20 °C, clear, colorless
anion traces   chloride (Cl-): ≤50 mg/kg
  sulfate (SO42-): ≤50 mg/kg
cation traces   Al: ≤5 mg/kg
  As: ≤0.1 mg/kg
  Ba: ≤5 mg/kg
  Bi: ≤5 mg/kg
  Ca: ≤20 mg/kg
  Cd: ≤5 mg/kg
  Co: ≤5 mg/kg
  Cr: ≤5 mg/kg
  Cu: ≤5 mg/kg
  Fe: ≤5 mg/kg
  K: ≤50 mg/kg
  Li: ≤5 mg/kg
  Mg: ≤5 mg/kg
  Mn: ≤5 mg/kg
  Mo: ≤5 mg/kg
  Na: ≤50 mg/kg
  Ni: ≤5 mg/kg
  Pb: ≤5 mg/kg
  Sr: ≤5 mg/kg
  Zn: ≤5 mg/kg
λ   0.5 M in H2O
UV absorption   λ: 260 nm Amax: 0.025
  λ: 280 nm Amax: 0.020
SMILES string   O.OS(=O)(=O)CCN1CCOCC1
InChI   1S/C6H13NO4S.H2O/c8-12(9,10)6-3-7-1-4-11-5-2-7;/h1-6H2,(H,8,9,10);1H2


General description

MES is one of the "Good" buffers developed for biological applications. MES is not recommended at pH 7.4; other buffers should be considered. All qualities are tested for trace ions and all can be used for biological and biochemistry applications. This product is used in molecular biology.


MES Monohydrate has been used:
• In the preparation of a solution used for the suspension and dilution of protoplasts to measure the density and number of protoplasts using a haemocytometer
• As a component of Murashige and Skoog basal salt media
• In the preparation of total ionic strength adjustment buffer (TISAB)

Preparation Note

A buffer using MES free acid can be prepared by titrating the free acid with sodium hydroxide to the desired pH (pKa =±1). Alternatively, volumes of equimolar MES free acid and sodium MES can be mixed to attain the desired pH. Standard mixing tables using stock solutions to prepare a buffer of a given pH have been published.

Other Notes

Solubility/Stability: MES is soluble in water, giving a clear colourless solution at concentrations of 0.5 M or higher. The pH of a solution should be between 2.5 and 5, depending on the concentration. Solutions are stable at 2-8C for months.
Sterilization: Sterilization should be by filteration through 0.2 uM filters. Autoclaving is not recommended by any sulfonic acid buffers. If buffers must be nuclease-free, it is best to treat the water, and then add the buffer solids after autoclaving. When MES solutions are autoclaved, they turn yellow (although pH does not change measurably. The identity of the yellow breakdown product is unknown.

Safety & Documentation

Safety Information

Personal Protective Equipment 
NONH for all modes of transport
WGK Germany 
Flash Point(F) 
Not applicable
Flash Point(C) 
Not applicable
Protocols & Articles
Peer-Reviewed Papers


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