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Quenched phosphorescence, a new detection method in capillary electrophoresis
Author(s) -
Kuijt Jacobus,
Brinkman Udo A. T.,
Gooijer Cees
Publication year - 2000
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/(sici)1522-2683(20000401)21:7<1305::aid-elps1305>3.0.co;2-u
Subject(s) - phosphorescence , analyte , chemistry , detection limit , capillary electrophoresis , chromatography , chemiluminescence , analytical chemistry (journal) , fluorescence , physics , quantum mechanics
The applicability of quenched phosphorescence as a detection mode in capillary electrophoresis (CE) was explored for a number of analyte classes and buffer systems. The detection method is based on the quenching of biacetyl phosphorescence (biacetyl is a constituent of the CE buffer) by the analytes via various mechanisms (energy transfer, electron transfer and, possibly, hydrogen donation) and gives rise to negative peaks in the electropherograms. A number of buffers in the pH range 4.7—11.5, frequently used in CE, were tested for their compatibility with this detection mode. Borate, succinate, malonate, acetate, and phosphate buffers (pH 4.7—8.5) could be used without any problems. With a pH of ca. 8.5 or higher the baseline declined with time, while at a pH higher than 9.5 no signal at all was obtained. Obviously, the noise on the phosphorescence signal ( i.e. , the baseline) determines the ultimate analyte detection limits (LODs). The baseline signal‐to‐noise ratio, usually denoted as the dynamic reserve (DR), was enhanced ca. 25‐fold compared to direct biacetyl excitation by sensitization of the biacetyl phosphorescence by 1,5‐naphthalenedisulfonic acid, and by application of a total emission mirror (TEM). A concentration of 1 × 10 −3 M 1,5‐naphthalenedisulfonic acid was found to be optimal. For the buffer systems considered, the DR was typically ca. 300—600 under optimized conditions (noise defined as 1 × σ). Investigated analytes include naphthalenesulfonic acids (NS), nitrophenols, hydroxybenzoic acids, amino acids, and dithiocarbamates (DTCs.). For most of these, the LODs were in the 10 −7 —10 −8 M range, which is significantly lower than with direct or indirect absorption detection.