Microchip micellar electrokinetic chromatography separation of alkaloids with UV‐absorbance spectral detection

A microchip device is demonstrated for the electrophoretic separation and UV‐absorbance spectral detection of four toxic alkaloids: colchicine, aconitine, strychnine, and nicotine. A fused‐silica (quartz) microchip containing a simple cross geometry is utilized to perform the separations, and a miniature, fiber‐optic CCD spectrometer is coupled to the microchip for detection. Sensitive UV‐absorbance detection is achieved via the application of online preconcentration techniques in combination with the quartz microchip substrate which contains an etched bubble‐cell for increased pathlength. The miniature CCD spectrometer is configured to detect light between 190 and 645 nm and LabView programming written in‐house enables absorbance spectra as well as separations to be monitored from 210 to 400 nm. Consequently, the configuration of this microchip device facilitates qualitative and quantitative separations via simultaneous spatial and spectral resolution of solutes. UV‐absorbance limits of quantification for colchicine, 20 μM (8 mg/L); strychnine, 50 μM (17 mg/L); aconitine, 50 μM (32 mg/L); and nicotine, 100 μM (16 mg/L) are demonstrated on the microchip. With the exception of aconitine, these concentrations are ≥20‐times more sensitive than lethal dose monitoring requirements. Finally, this device is demonstrated to successfully detect each toxin in water, skim milk, and apple juice samples spiked at sublethal dose concentrations after a simple, SPE procedure.

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