Separation of the enzyme cofactor pyrroloquinoline quinone and three isomeric analogues by capillary electrophoresis with ion-pairing media

The enzyme cofactor pyrroloquinoline quinone (PQQ) was successfully separated from three closely related isomeric analogues by capillary electrophoresis with ultraviolet detection. Rapid and efficient separation of all four negatively charged isomers with baseline resolution was achieved by the addition of low concentrations (1–5 mM) of short chain tetraalkylammonium (TAA) salts to the capillary buffer. The TAA cations act as ion-pairing agents and promote differential migration of the isomers with only a minimal reduction in the electroosmotic flow. The effects of the TAA salt concentration and the alkyl chain length were examined. Detection limits of PQQ and its isomers were in the range of 7–15 μM with mass detection limits of 98–210 fmol.