Fig. 4.
(a,) Picture of the chip-based microcolumns, on which the mixture of 0.05–1 mg/mL Cr(VI) and Cr(III) standard solutions of 10 μL volumes is loaded for 4 min to retain (separate) the Cr(VI). (b,) Signals of the effluents obtained with FAA spectrometer using micro-injection of the effluents as discrete samples of 30 μL. Effluents were collected into a plastic vessel inserted into the ends of the microcolumns. (c,) Densitogram of the adsorbed Cr(VI) (measuring the intensity (RGB) of colors on the microcolumns of (a,)). (d,) The calibration plot of the Cr(VI) standard solutions adsorbed on the microchip and eluted into the FAA spectrometer.