Solid-Phase Extraction and Detection by Digital Image Directly in the Sorbent: Determination of Nickel in Environmental Samples

Abstract

Recently, analytical procedures based on computer vision related to the colorimetric analysis of digital images have been described in the scientific literature. In this sense, a novel analytical approach is presented based on digital image colorimetry for nickel determination. The method consists in the development of a system with solid-phase extraction, consisting basically of an extraction chamber filled with polystyrene divinylbenzene sorbent impregnated with the complexing reagent 1-(2-thiazolylazo)-p-cresol (TAC) and a portable microscope multifunction, used for image acquisition. The image of the sorbent after extraction of Ni is obtained. This image is related to the concentration of the elements. The variables (pH, flow, and sample volume) were evaluated using a full factorial design 23 for the screening and a Doehlert matrix to establish the significant variables’ optimal levels. The enrichment factor and limit of detection were 148 and 0.8 μg L−1, respectively. The method was applied to the determination of nickel in river water, coffee, and cigarette samples.