Interfacing microfluidic chip-based chromatography with flame atomic absorption spectrometry for the determination of chromium(VI)

This work demonstrates the first study on interfacing of microfluidic chip-based chromatography to flame atomic absorption spectrometry (FAAS) for a simple and fast separation or preconcentration and subsequent determination of species. The developed low-cost polydimethylsiloxane microchip includes 12 microcolumns of conventional C18 (5μm) chromatographic particles, making the parallel chromatographic separation/preconcentration and the direct introduction of the effluent into the spectrometer possible. In order to test this hyphenated microchip–FAAS system, the Cr(VI) was selected to be determined. The adsorbed Cr(VI) was eluted with methanol, and the 30μL effluents were collected into plastic vessels inserted into the ends of the microcolumns. Then, the effluents were analyzed by FAA spectrometer using micro-injection of the effluents as discrete samples. The separation/preconcentration and FAAS determination of 12 samples needed less than 5min due to the multiplex feature of the proposed system. The overall capacity of the microcolumn (C18, 5μm beads, 20mm×1mm×0.1mm) was calculated to be 0.45μg/mm for Cr(VI). Loading only 80μL samples onto the microchip and nebulizing the methanolic effluent of 30μL into the FAA spectrometer, 0.0031μg/mL limit of detection was obtained.