Sensitized and quenched phosphorescence as a detection mode in capillary electrophoresis

The potential of sensitized and quenched phosphorescence of biacetyl as an optical detection mode in capillary electrophoresis (CE), complementary to absorption and fluorescence detection, was explored. From 24 naphthalenesul fonates (NS) that were studied in batch experiments, 5 NS were used as test compounds in CE, The technique is based on the intense phosphorescence emi ssion of biacetyl (present as a constituent of the CE buffer) at room tempe rature in deoxygenated liquid solutions. A simple device, based on purging with nitrogen gas, was developed to meet this deoxygenation requirement in CE, A standard liquid chromatography luminescence detector, provided with a pulsed xenon light source, was used for detection. In view of the phosphor esence lifetime of biacetyl (70 mu s under present solution conditions), th e background caused by scattered excitation light could be readily suppress ed by using a delay time for detection. Both phosphorescence modes can be a pplied at a 0.02 M biacetyl concentration, though in the quenched mode a bi acetyl concentration of 0.05 M yields better results. From the five test an alytes considered, three show sensitized phosphorescence and two dynamicall y quenched phosphorescence. Though various experimental parameters still ha ve to be optimized further, the results are quite encouraging: under stacki ng conditions (pt = 768 mbar.s), detection limits ranged from 5 x 10(-8) to 4 x 10(-7) M.