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

Abstract

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 microM (8 mg/L); strychnine, 50 microM (17 mg/L); aconitine, 50 microM (32 mg/L); and nicotine, 100 microM (16 mg/L) are demonstrated on the microchip. With the exception of aconitine, these concentrations are > or =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.

The advances of electromigration techniques applied for alkaloid analysis

“…There are works proving usefulness of the sodium cholate–Tris composed buffer as the background electrolyte and sodium acetate as the high salt sample medium for the micelle stacking technique. The same team of authors later applied it for toxic alkaloid determination in milk with microchip electrophoresis (Newman et al ., ).…”

“…Application of capillary electrophoresis in the area has recently focused mainly on potatoes (Kvasnicka et al ., ), beverages (Newman et al ., ; Bodoki et al ., ; Lu et al ., ; Mikus et al ., ; Zhu et al ., ; Nogueira and do Lago, ), tobacco (Chen and Xu, ; Zhang et al ., ; Huang and Hsieh, ; Chang et al ., ) and vegetable oils (Sanchez‐Hernandez et al ., , ; Table ). The interest in the products has been triggered not only by the food product quality control, but also and primarily by the demand for monitoring toxic compounds such as calystegines (Kvasnicka et al ., ), trigonelline (Sanchez‐Hernandez et al ., , ), colchicine (Newman et al ., ; Lu et al ., ), and pyridine alkaloids in accordance with their permissibility in human consumption. Extensive research has been carried out in determination of nicotine and its derivatives in tobacco products and pharmaceutical formulations.…”

“…Owing to the properties of alkaloids, cation‐exchange sorbents have been found most popular in their determination. Application of CXSPE has been reported for food (Newman et al ., ; Copper et al ., ), plant material (Kreft et al ., ), and pharmaceutical (Sturm et al ., ) analysis (Tables and ). Incorporation of the step in the analytical procedure has enabled preconcentration, which in some cases has been crucial for quantitation, and removal of the interfering matrix such as the highly viscous syrup (Sturm et al ., ) or herbal compounds (Kreft et al ., ).…”

Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices

“…The silica monolith was prepared in situ in the second part of the channel (effective length, 2.6 cm) from a polymerisation solution containing methyl trimethoxysilane (MTMOS), phenethyl trimethoxysilane (PTMOS), PEG, acetic acid and diethylamine. On- chip UV detection was carried out via optical fibres as described in more detail elsewhere [56]. The sample was injected electrokinetically by applying a potential of 2 kV between the sample inlet and the waste reservoir for 100 s, after which the sample inlet reservoir was sealed.…”

Capillary Electromigration Techniques for the Quantitative Analysis of Colchicine

“…Comparatively, only a few papers have been dealing with the analysis of colchicine by electromigration techniques, 13,[33][34][35] amongst which two describing the use of microchip micellar electrokinetic chromatography. One of the major drawbacks of the described electrophoretic techniques, applied to clinical drug monitoring of colchicine, toxicological screening and food analysis, is their relatively high limit of detection and quantification (the lowest theoretical LOD reported is 360 ng mL -1 ).…”