Electrochemically generated Ru(bpy)(3)(3+)-based chemiluminescence detection in micellar electrokinetic...

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrochemistry

Background:

• Chemiluminescence (CL) detection offers high sensitivity for trace analysis.
• Micellar electrokinetic chromatography (MEKC) is effective for separating neutral analytes.
• Traditional methods for generating ruthenium(III) (Ru(3+)) for CL detection can lead to surfactant precipitation.

Purpose of the Study:

• To develop and validate an in situ generated ruthenium(III) (Ru(bpy)(3)(3+)) chemiluminescence detection method compatible with micellar electrokinetic chromatography (MEKC).
• To overcome limitations of existing Ru(3+) generation protocols, particularly surfactant precipitation.
• To demonstrate the separation and detection of underivatized amines and amino acids.

Main Methods:

• Continuous post-capillary addition of the chemiluminescence reagent, ruthenium(II) tris(2,2'-bipyridine) (Ru(bpy)(3)(2+)).
• In situ electrochemical generation of Ru(bpy)(3)(3+) at the interface of the separation capillary and working electrode.
• Utilizing micellar electrokinetic chromatography (MEKC) for analyte separation, ensuring the critical micelle concentration is not exceeded in the detection zone.

Main Results:

• Demonstrated compatibility of in situ generated Ru(bpy)(3)(3+)-based chemiluminescence with MEKC.
• Achieved high separation efficiency for triethylamine, with 70,000 plates per meter.
• Obtained a limit of detection of 1.5 femtomoles (S/N=2) for triethylamine, showcasing enhanced sensitivity.

Conclusions:

• The developed method provides significant advantages over existing Ru(3+) generation protocols for CL detection in MEKC.
• The approach effectively prevents surfactant precipitation and allows analytes to react with the CL reagent.
• This methodology enables sensitive and efficient separation and detection of underivatized amines and amino acids.