Chalcone-based colorimetric naked eye detection of vanadium in crude oil using a new microfluidic device

Chalcones are a highly effective chelating agent used in spectrophotometric vanadium ion detection. It was observed that potassium (E)-(4-(3-(4-hydroxy-3- methoxyphenyl) acryloyl)phenyl) carbamodithioat (HMAPC) reagent formed a yellow colored complex with vanadium ion at 420 nm. Vanadium ion was chelated with the chalcone (HMAPC) reagent in acidic medium at pH = 6 using Britton–Robinson buffer (BRB). The effect of reagent volume, pH, temperature, time, and interferences was studied. The stoichiometric composition of the formed complex was found to be 1:2 (metal: reagent) by Job's method of continuous variation and mole ratio methods. Beer's law was obeyed in the range of 1–32 µg mL⁻¹ with molar absorptivity of 1589.32 L mol⁻¹cm⁻¹, sensitivity of 0.03225 µg mL⁻¹, regression coefficient of 0.9945 and an estimated detection limit of 0.1354 µg mL⁻¹. The accuracy (recovery percentage) was ranged between 97.2 and 104.8%, and precision (R.S.D.%) is less than 1.5%. A colorimetric method equipped with a portable microfluidic device (µ-chip), as well as a smartphone (iPhone), is used to measure vanadium concentrations. The resulting color changes were taken by a smartphone camera. The obtained images were analyzed by ImageJ software to assay the vanadium concentration. Under the identical experimental settings, the suggested approach and the spectrophotometric method were compared, and it was discovered that both were advantageous. The suggested approach technique was straightforward and easy to use, and the findings indicated that it was practical and might be used for on-site analysis. It also had promising properties of mobility and low manufacturing cost, making it appropriate for the detection of vanadium in crude oil.