عنوان مقاله [English]
In this study, an image analysis method using a homemade colorimeter for determination of trace amount of nitrite in various water samples is provided. The proposed method is based on using a smartphone to obtain RGB values of digital images. 4-nitroaniline and α-naphthol were used to convert nitrite to a colored product. Magnetic solid phase extraction was then used to extract azo dye. In magnetic solid phase extraction, magnetic graphene was used as adsorbent and acetone as a desorption solvent. After taking the extraction phase digital images using a cell phone and their analyzing using Color Grab software, R values were used to obtain analysis signal related to nitrite concentration. The experimental parameters affecting the reaction and extraction efficiency were investigated. Under optimum conditions, the detection limit and the quantitative limit of the method were obtained 1.2 and 4 μg l-1, respectively. The calibration graph was linear in the range of 10-300 μg l-1 with a correlation coefficient of 0.993. The relative standard deviations for 100 and 30 μg l-1 were 2.2 and 3.9, respectively. The proposed method was successfully applied for the determination of nitrite in various water samples.