Post-column ultra-fast co-catalyzed peroxyoxalate chemiluminescence detection in capillary electrophoresis and capillary electrochromatography

CEC of phytochemical bioactive compounds

Although there are many publications related to technological or methodological developments of CEC, few focus on the analysis of natural products, especially phytochemical bioactive compounds. This review summarized the application of CEC in the analysis of phytochemical bioactive components, including flavonoids, nucleosides, steroids, lignans, quinones and coumarins, as well as fingerprint analysis of herbs. The strategies for optimization of CEC conditions and detection were also discussed.

On-line chemical generation of tris(2,2′-bipyridyl)ruthenium(III) and its application in CE with chemiluminescence detection

A novel tris(2,2'-bipyridyl)ruthenium(III) [Ru(bipy)(3) (3+)]-based chemiluminescence (CL) detection in CE using an on-line chemical generation scheme has been demonstrated. Two continuous streams respectively containing solutions of Ru(bipy)(3) (2+) and acidic cerium(IV) used as a homogeneous chemical oxidant are employed to generate Ru(bipy)(3) (3+), which is delivered into the reaction capillary of a coaxial flow interface and then reacted with analytes at the end of the separation capillary to yield light. The important operational parameters for separation and detection are identified and optimized. Four alpha-ketocarboxylic acids used as models, outside of the amine-containing compounds, are successfully separated and detected to evaluate the feasibility of the approach. The excellent resolution and detection sensitivity was achieved by using 50 mmol/L phosphate running buffer (pH 9.5) with 0.7 mmol/L CTAB, and CL reagent solution streams containing 0.15 mmol/L Ru(bipy)(3) (2+) and 0.8 mmol/L cerium(IV) (0.25 mol/L H(2)SO(4)), respectively. The concentration detection limits for alpha-ketocarboxylic acids were below 3.7x10(-8) mol/L (S/N = 3). The proposed method was applied to the determination of alpha-ketocarboxylic acids in five different honey samples with satisfactory results.

Solvent and pH effects on fast and ultrasensitive 1,1′-oxalyldi(4-methyl)imidazole chemiluminescence

Solvent and pH effects on fast and ultrasensitive 1,1'-oxalyldi(4-methyl)imidazole chemiluminescence (OD4MI-CL) were studied. The influences of these two factors on the complex OD4MI-CL reaction are discussed within a conceptual prototype for developing aqueous and non-aqueous capillary electrophoresis (ACE and NACE) devices with OD4MI-CL detection. The reaction channel length and OD4MI yield from the reaction between bis(2,4,6-trichlorophenyl) oxalate (TCPO) and 4-methylimidazole in the channel will be influenced by pH, water volume fraction, and cosolvent properties of the solution. Optimum OD4MI-CL efficiency is observed at pH 6.5 when 1-propanol, which has a low dielectric constant (epsilon = 20.8), is used as the NACE solvent in the separation channel. Water (epsilon = 80.1), the solvent in the ACE separation channel, acts similarly to a high dielectric constant organic solvent in NACE because the disadvantages normally associated with TCPO-CL reactions in water disappear due to the faster OD4MI-CL reaction versus OD4MI decomposition in aqueous solution. Therefore, it is expected that the OD4MI-CL detection system can be used in both NACE and ACE devices without requiring detector modifications. We also conclude that OD4MI-CL detection in NACE and ACE devices will be much more sensitive than the TCPO-CL detection used in current NACE devices.