A combination of dispersive liquid–liquid microextraction and smartphone-based colorimetric system for the phenol measurement

•A smartphone-based colorimetric system was used for the phenol determination.•A preconcentration technique was developed by ultrasound assisted-dispersive liquid–liquid microextraction (UA-DLLME).•The method was used for the analysis of phenol in water and wastewater samples.•In this method, reagents were miniaturized and LOD is lower than the standard method of 5530 APHA.•The method was simple, rapid and cost-effective with the capability of field analysis. In this work, a rapid and effective analytical procedure has been developed forphenol determination from aqueous samples using a smartphone-based colorimetric system. This methodology is based on the reaction of the phenol with 4-aminoantipyrine (4-AAP) in the presence of the oxidant agent, forming of brown-orange color product which extractable by ultrasound assisted-dispersive liquid–liquid microextraction (UA-DLLME), and direct obtaining of RGB (Red, Green, and Blue) values of organic phase in a conic tube by free Android app Color Grab. The effect of various parameters on the derivatization process and microextraction procedure including; sample pH, hexacyanoferrate and 4-AAP concentration, type and volume of extraction solvent and ultrasound time were investigated. Under the optimized conditions, a working range between the 5.0 and 300 μg L−1 of phenol was attained and the limit of detection (LOD) and limit of quantification (LOQ) obtained were 1.7 and 5.7 μg L−1, respectively. Finally, the proposed methodology was applied for phenol determination in environmental water and wastewater samples with satisfactory results. The recoveries of phenol from spiked samples were found in the range of 93.7–103.6 %.