This research presents a novel, simple and green method for colorimetric determination of As(III) using a digital camera as the colorimeter. It is based on chemical hydride generation of arsine (AsH3) from acidic solution of As(III) by NaBH4 as well as the sequential reaction of arsine with Fe(III)-1,10-phenanthroline solution that produces red complex of Fe(II)-1,10-phenanthroline. The intensity of color red is related to the concentration of As(III) and acquired by image processing—Image J—software. To achieve the best sensitivity, we investigated the changes of RGB value in terms of red color intensity of the complex. Blue was the best as it showed the highest sensitivity. Under optimized conditions, the calibration curve was linear in the range of 1–25 µg mL−1 for As(III) and detection limit was 0.392 µg mL−1. The relative standard deviation (RSD) for five replicate measurements of 10, 15, 20 µg mL−1 of As(III) were 0.89, 2.43 and 3.08%, respectively. The proposed method was successfully used to determine As(III) in the industrial wastewater using standard addition method. The desirable recovery values (96–109%) indicate applicability of the proposed method for determination of As(III) in a complex matrix, such as industrial samples, in the presence of several unknown interferences without the need for any sample preparation.

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