Determination of pH using water protons and chemical exchange dependent saturation transfer (CEST)

Magn Reson Med. 2000 Nov;44(5):799-802. doi: 10.1002/1522-2594(200011)44:5<799::aid-mrm18>;2-s.


Solution pH was measured using water proton NMR via chemical exchange dependent saturation transfer (CEST) with selected chemical exchange sites. Several useful pH-sensitive proton chemical exchange agents were found: 5,6-dihydrouracil, 5-hydroxytryptophan, and a combination of 5-hydroxytryptophan and 2-imidazolidinethione. A ratiometric approach was developed that permitted pH determinations that were independent of water T(1) or exchange site concentration.

MeSH terms

  • Contrast Media / chemistry
  • Contrast Media / metabolism
  • Gadolinium / chemistry
  • Gadolinium / metabolism
  • Hydrogen-Ion Concentration*
  • Magnetic Resonance Imaging / methods*
  • Magnetic Resonance Spectroscopy / methods
  • Protons
  • Water / chemistry


  • Contrast Media
  • Protons
  • Water
  • Gadolinium