On-line indirect chemiluminescence detection in capillary electrophoresis

Capillary electrophoresis with on-line indirect chemiluminescence detection was firstly used in detecting catecholamines and six amino acids neurotransmitters. The high and constant chemiluminescence background was obtained by the chemiluminescence reaction of luminol–H2O2, enhanced by Co(II). The analytes could complex with Co(II) and reduced the free Co(II) concentration, and thus, the chemiluminescence intensity decreased. The degree of chemiluminescence suppression was a measure of the analytesʹ concentration. The choice of the catalyst ion, the mixing model of analytes with chemiluminescence reagent, the concentration of H2O2 and Co(II) were discussed. Sodium dodecyl sulfate was used in separating catechol, epinephrine, norepinephrine and dopaminde, with the detection limit of 87, 51, 22, and 38 fmol, respectively. The detection limit for six amino acid is 9, 41, 15, 28, 33, and 250 fmol, respectively, which are 2 orders of magnitude lower than that of HPLC.