A simple and rapid technique for the determination of copper based on air-assisted liquid–liquid microextraction and image colorimetric analysis†
In this study, a new, cheap, simple and rapid method for the determination of copper in water and food samples using air-assisted liquid–liquid microextraction and digital image decomposition into the primary colors Red (R), Green (G) and Blue (B) is introduced. In the proposed method, sodium diethyl-dithiocarbamate (Na-DDTC) and carbon tetrachloride (CCl4) were used as the chelating agent and extraction solvent, respectively. The digital images of the extraction phase were obtained using an Android mobile phone and analyzed using a free app (Color Grab). Then the value of the B channel was taken as the analytical signal. The effects of different parameters influencing the extraction efficiency were investigated and optimized. Under the optimal conditions, the limit of detection (LOD) and quantitation (LOQ) were 1.5 and 5 μg L−1, respectively. The repeatability of the proposed method, expressed as the relative standard deviation (RSD), was 4.53% for intra-day (n = 8, C = 100 μg L−1) and 5.66% for inter-day (n = 5) precision. The proposed method was applied for the determination of trace amounts of copper in rice, lettuce and water samples with satisfactory results validated by the Graphite Furnace Atomic Absorption Spectrometry technique.