Quenched phosphorescence, a new detection method in capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science
• Spectroscopy

Background:

• Capillary electrophoresis (CE) is a powerful separation technique.
• Phosphorescence detection offers high sensitivity but requires specific conditions.
• Direct biacetyl excitation in CE has limitations in sensitivity and dynamic reserve.

Purpose of the Study:

• To evaluate quenched phosphorescence as a detection mode in capillary electrophoresis (CE).
• To investigate the compatibility of various buffer systems with this detection method.
• To enhance the sensitivity and dynamic reserve of biacetyl phosphorescence detection.

Main Methods:

• Exploration of quenched phosphorescence detection in CE using biacetyl as a phosphorescent probe.
• Testing of various buffer systems (borate, succinate, malonate, acetate, phosphate) across a pH range (4.7-11.5).
• Optimization of detection sensitivity through sensitization with 1,5-naphthalenedisulfonic acid and use of a total emission mirror (TEM).

Main Results:

• Biacetyl phosphorescence quenching by analytes results in negative peaks in electropherograms.
• Compatible buffer systems identified in the pH range of 4.7-8.5; higher pH led to baseline decline or signal loss.
• Significant enhancement (approx. 25-fold) in dynamic reserve (DR) achieved, reaching 300-600 under optimized conditions.
• Analyte detection limits (LODs) in the 10(-7)-10(-8) M range were obtained for naphthalenesulfonic acids, nitrophenols, hydroxybenzoic acids, amino acids, and dithiocarbamates.

Conclusions:

• Quenched phosphorescence is a viable and sensitive detection mode for CE.
• Optimized conditions, including buffer selection and use of sensitizers/mirrors, are crucial for high performance.
• This method offers significantly lower detection limits compared to traditional absorption detection in CE.