Assess the ability of detecting low concentration analyte with near-infrared spectroscopy based on dynamic enrichment

Abstract The ability to detect low concentration analyte with near-infrared diffuse reflectance spectroscopy (NIRDRS) based on dynamic enrichment method has been assessed. A special design of fluidized bed enrichment device was used to enrich a large volume of analyte's dilute solution before spectrum detection, in order to improve the detection sensitivity of NIRDRS. A kinetic model, which considers the mass transfer with liquid film diffusion, has been used to characterize the adsorption process in this device. The developed model agreed with the experimental results very well in a wide range of the influent flow rate (F) and solution concentration (C0). Based on this model, the lowest detectable concentration was estimated, at the same time the effects of liquid fluid rate and operation time on this value were also investigated. Meanwhile, a comparison between this model and the static adsorption model was made. Furthermore, a series of carbaryl aqueous solutions at different concentrations were treated with the enrichment device to verify the estimated lowest concentration. This study reveals that the specially designed fluidized bed device is able to enrich enough amount of analyte in a quite short time, and based on this dynamic adsorption model, it is possible to detect analyte in solution quantitatively at ppm-level by NIRDRS.