A Green Analytical Approach Based on Smartphone Digital Image Colorimetry for Aspirin and Salicylic Acid Analysis

Aspirin (ASA) is a globally used anti-inflammatory drug and salicylic acid (SA) is the biological metabolite of ASA. As an analytical chemist, it's always a challenge to accurately and precisely determine a drug along with its metabolites with a single method. Hence, we aim to develop a simple and low-cost assay based on combination of vortex assisted-dispersive liquid-liquid microextraction (VADLLME) with smartphone based digital image colorimetry (DIC) as a promising platform for simple low-cost analysis of ASA and SA. The method comprises of three simple steps viz. (i) extraction and pre-concentration of ASA/SA by VADLLME, (ii) reaction of ASA/SA with Trinder reagent on a filter paper strip to produce blue colour, and (iii) DIC of developed colour with imageJ software. Design of experiment approach comprising of Plackett-Burman design (PBD) and central composite design (CCD) were used for optimization of parameters affecting the efficiency of the proposed method. Under the optimized conditions, the limits of detection (LOD) and the limit of quantitation (LOQ) were found to be 8.88 and 29.0 µg mL−1, respectively. Calibration plot demonstrated good linearity in the range of 50–400 µg mL−1, with coefficients of determination (R2) higher than 0.993 and standard deviation less than 10%. The proposed method has been successfully applied for the estimation of ASA/SA in pharmaceutical formulations (tablets), cosmetic product and human urine samples, with percent recoveries (%R) ranging from 92.14–99.6%. In addition, the green character of the proposed method from sample collection to final determination has been evaluated by using ComplexGAPI index.