Calcium-doped lanthanum cobaltite-based electrochemical sensor for the sensitive detection of salicylic acid in real samples: pond water and acne gels.

Salicylic acid (SA) is a type of contaminant of emerging concern (CEC) belonging to the category of pharmaceutical products. It is a commonly used drug in the treatment of various skin diseases and an over-the-counter (OTC) drug used in an undisciplined manner across the world. It is also used as a supplement for yield improvement in plants. Exposure to high doses of SA can lead to a toxic condition known as salicylism. To better monitor the levels of SA, Ca-doped LaCoO3 (LCCO)/GCE is fabricated in this study. LCCO is synthesized by a solvothermal method and characterised by SEM, FE-TEM, XRD, EDX, and XPS techniques. Substitution of Ca2+ with La3+ results in the formation of oxygen vacancies due to the variation in the oxidation states of Co. The similar ionic radius of La3+ and Ca2+ delivers a better structural stability and better catalytic activity for the perovskite. LCCO/GCE with its excellent catalytic activity could detect SA with a limit of detection (LOD) of 30 nM and a linear range of 0.05-800 μM. The fabricated sensor is reproducible with a relative standard deviation (RSD) of less than 1% and is stable up to 30 days with less than 5% variation from the initial current value. The sensor is also selective in sensing SA, even in the presence of a hundred-fold concentration of other interferents. In addition, the real-world applicability of the sensor is investigated in pond water and acne gels, which both give excellent recovery percentages.