Voltammetric determination of organic UV filters by carbon paste electrodes modified with pyridinium-based ionic liquids.

The rapid and sensitive voltammetric determination of organic UV filters benzophenone-3 (BP-3) and avobenzone (AVO) was performed by an ionic liquid carbon paste electrode (IL-CPE). Namely, the synthesized pyridinium-based ILs, 1-butyl-3-methylpyridinium chloride ([N-C-3CPy]Cl) and 1-ethoxyethyl-3-methylpyridinium chloride ([N-COC-3CPy]Cl) were compared as bulk CPE modifiers for BP-3 determination. [N-C-3CPy]Cl-CPE showed more favorable interactions with the target analyte, and it was tested for AVO determination, too. Cyclic voltammetric (CV) studies suggested that the irreversible electrode reaction is adsorption controlled in the case of both UV filters. Also, the square-wave adsorptive stripping voltammetric (SW-AdSV) method was optimized for quantifying selected UV filters. In the model solutions, the linear calibration curve was obtained by the SW-AdSV method in the concentration range from 0.05 to 0.89 μg mL at pH 3.0 for BP-3 (E = -0.7 V, t = 100 s), and from 0.05 to 1.77 μg mL at pH 11.98 for AVO (E = 0.2 V, t = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL in both cases, while the relative standard deviation (RSD) was lower than 1.5%. The affordable IL-based voltammetric sensor fulfills the main requirements for application in real samples due to an adequate selectivity towards selected analytes in the presence of interferents usually found in swimming pool water. Therefore, the BP-3 and AVO were quantified in a swimming pool water matrix with good repeatability and recovery. The obtained results demonstrate an excellent potential of the IL-CPEs, especially of the [N-C-3CPy]Cl-CPE, for determining selected UV filters in various real samples.