On-chip electromembrane extraction using deep eutectic solvent and Red-Green-Blue analysis by Quick-Response code readable customized application on a smartphone for measuring Salicylic acid in pharmaceutical and plasma samples

The current work presents an on-chip electromembrane extraction (OC-EME) method using deep eutectic solvent followed by QR code-based red-green-blue (RGB) analysis for measuring salicylic acid (SA) in plasma and pharmaceutical samples. The RGB analysis was performed based on forming the SA-Fe3+ complex in the acceptor phase giving a purple solution. The QR code readable customized app provided rapid, easy, and cost-less qualification and quantification of SA with the aid of principal component analysis (PCA). Parameters affecting OC-EME, including the supported liquid membrane (SLM), pH of the donor and acceptor phases, applied voltage, and sample flow rate, were optimized. Also, the concentration of FeCl3, as a chromogenic reagent, and its reaction time with SA were investigated to find the best concentration-dependent signal. Under the optimized conditions, a good relationship was observed between the green intensity and SA concentration within the range of 1.0-100.0 mg l−1 (R2 = 0.9946) in water and 5.0-100.0 mg l−1 (R2 = 0.9902) in plasma. Intra- and inter-day RSDs% were obtained less than 4.7% and 7.7%, respectively. Finally, the method was successfully applied for measuring SA in foot corn treatment, Aspirin medicines, and human plasma, with relative recoveries between 89.0-129.2%.