Isethionic acid

This chapter discusses isethionic acid. The occurrence of isethionate as the major anion in squid axoplasm encouraged the view that this unusual sulfonate had an important role in the bioelectric behavior of the squid axion. While isethionate is found in mammalian tissue at only a small fraction of the 200 μmol/g concentration observed in squid axoplasm, additional interest was stimulated by the structural relationship and possible biological relationship between isethionate (2-hydroxyethyl sulfonate) and taurine (2-aminoethyl sulfonate). Indeed early studies using isotopically labeled taurine revealed the in vivo and in vitro conversion taurine to isethionate. Early analytical procedures involved separation of the isethionate from contaminating anions using ion-exchange resins followed by digestion with nitric acid. The sulfate formed was isolated and determined gravimetrically as the barium salt. The conflicting results reported by various workers on the metabolic origin and fate of isethionate encouraged the development of gas-liquid chromatographic procedures. Three methods are discussed that use methyl ether/methyl ester, silyi, or chloroethylsulfonylchloride derivatives. Employment of the chlorinated derivative extended the sensitivity of the gas chromatographic analysis manyfold because of the intrinsic sensitivity of the electron capture detector. With this method, sensitivity was greater than 5 ng/g tissue.