A novel liquid colorimetric probe for highly selective and sensitive detection of lead (II)

Abstract

A novel liquid colorimetric sensor based on deep eutectic solvent (DES) was developed for the preconcentration and detection of Pb²⁺ in fruit juice, milk and cereal samples. The colorimetric probe was simply fabricated by adding dithizone (DZ) into DES, prepared from choline chloride and phenol. Pb²⁺ was formed complex with DZ in the probe, providing hydrophobic complex of [Pb-DZ] which was simultaneously extracted into DES and the color was changed from light orange to carmine red. The enriched [Pb-DZ] in DES was detected using spectrophotometer at 520 nm and naked-eyes. In addition, a smartphone in combination with an Image J program was used as an alternative detection device. Under optimal conditions, the enrichment factor was 92 with LOD of 2.1 µg L^-1 and the linear range was 0.007-0.075 mg L^-1. The proposed liquid colorimetric sensor was successfully applied for Pb²⁺ detection in various food samples and the results were in good agreement with those obtained by FAAS. The advantages of this method are simple, rapid, environmental friendly and low cost.

Keywords: Colorimetric sensor; Deep eutectic solvent; Lead; Liquid phase microextraction.