Microfluidic-based liquid-liquid microextraction in combination with smartphone-based on-chip detection for the determination of copper in biological, environmental, and food samples

•Microfluidic-based microextraction was combined with smartphone-based detection.•An on-chip sensing strategy was introduced using a smartphone.•The copper assay was performed by the method successfully.•The method was used for the analysis of biological, environmental, and food samples.•The method was simple and cost-effective with adequate analytical performance. In the present work, a simple and green microfluidic-based liquid-liquid microextraction in combination with smartphone-based on-chip detection was introduced for the determination of copper in environmental, biological, and food samples. The procedure was based on an ion-pair formation between tetrabutylammonium and tetrathiocyanatocuprate(II) anion, which was extracted with a suitable extractant and subsequent color sensing using a smartphone. All the steps were performed in a microchip. The smartphone was used as both a detector and a data processing unit. Different experimental parameters affecting analytical signal were studied and optimized. Under the optimum conditions, the method showed a linear dynamic range between 0.3 and 40 mg L−1 with a determination coefficient of 0.9953. The limits of detection and quantification were obtained 0.1 and 0.3 mg L−1, respectively. The method provided a precise determination with relative standard deviations in the range of 4.1–5.3%. Finally, the method was successfully applied for the determination of copper in whole blood, mushroom, wastewater, and tap water samples with spiking recoveries in the ranges of 80–98%, 96–108%, 95–107%, and 100–103%, respectively. In comparison with the atomic absorption technique, no significant difference was observed between the two methods in terms of accuracy.