Electroanalytical performance of a β-cyclodextrin and ionic liquid modified carbon paste electrode for the determination of verapamil in urine and pharmaceutical formulation

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-C4-3C1Py]Cl) and 1-ethoxyethyl-3-methylpyridinium chloride ([N-C2OC2-3C1Py]Cl) were compared as bulk CPE modifiers for BP-3 determination. [N-C4-3C1Py]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-1 at pH 3.0 for BP-3 (Eacc = -0.7 V, tacc = 100 s), and from 0.05 to 1.77 μg mL-1 at pH 11.98 for AVO (Eacc = 0.2 V, tacc = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL-1 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-C4-3C1Py]Cl-CPE, for determining selected UV filters in various real samples.

A Highly Sensitive Electrochemical Sensor Based on Electrocatalytic Reduction Effect of Cu2+ on Trace Determination of Malathion in Soil and Other Complex Matrices

The current strategy reports a highly sensitive and selective square wave-cathodic stripping voltammetric protocol for malathion determination. The established method was based on the controlled adsorptive accumulation of malathion in the presence of Cu2+ ions in an aqueous solution of pH 2 onto the hanging mercury dropping electrode (HMDE) and measuring the resulting cathodic peak current of the adsorbed species at −0.42 V versus Ag/AgCl electrode. The low limits of detection (LOD) and quantification (LOQ) of malathion of the assay were estimated to be 3.1 × 10−10 and 1.03 × 10−9 M with a linear dynamic range of 1.03×10−9 – 2.0 × 10−7 M, respectively. The method was satisfactorily applied and validated for malathion determination in environmental samples. The experimental Student texp and Fexp values did not exceed the tabulated ttab (2.78) and Ftab (6.39) at 95% (P = 0.05) confidence (n = 5), confirming the precision and independence on the matrix. The developed sensing platform for the detection of malathion shows superior performance to conventional electrochemical methods. The proposed sensor offered simple, economical, reproducible, and applicable approach for the determination of malathion in environmental samples.