Determination of phytochelatins by capillary zone electrophoresis with electrospray tandem mass spectrometry detection (CZE-ES MS/MS)

The coupling of capillary zone electrophoresis with electrospray mass spect rometry was optimized for the direct determination of phytochelatins (PCs) in extracts obtained from cells and plants that had been exposed to metal s tress. Gluthathione and phytochelatins belonging to the different families (gamma Glu-Cys)(n)Gly (n-PC), (gamma Glu-Cys)(n)Ser, (gamma Glu-Cys)(n)beta Ala and (gamma Glu-Cys)(n) were separated in an uncoated capillary at pH 4 using a 5 mM ammonium acetate buffer, and detected by electrospray (ES) MS in the full scan mode (300-1100 u). The use of on-line tandem MS detection in the product ion scan mode of putative protonated molecules of PCs allow ed the unambiguous confirmation of the identity of the compounds detected b y ES MS. The operational conditions were optimized and the figures of merit were evaluated using n-PC2, n-PC3 and n-PC4 standards purified from a mixt ure obtained after the reaction of glutathione in the presence of Cd2+ and the enzyme PC-synthase. The method was applied to the characterization of b ioinduced ligands in cell cultures of soybeans (Glycine max) and in rice (O ryza sativa) roots without the need for a preliminary sample cleanup by siz e-exclusion and/or reversed phase chromatography.