A Novel Voltammetric Methodology Based on a Methacrylic Acid/2-Methyl Thiophene Ion-Imprinted Polymer Sensor for the Determination of As(III) in Water Samples.

Abstract

A highly selective ion-imprinted polymer (IIP) was synthesized for the first time, optimized, characterized, and incorporated in a carbon paste electrode (CPE) for As(III) determination in water samples by differential pulse anodic striping voltammetric (DPASV). The As(III)-IIP was prepared considering as functional monomers 2-methyl thiophene and methacrylic acid and ethylene glycol dimethacrylate as a cross-linker, for the As(III) determination, since it is estimated that several people are chronically exposed to arsenic-contaminated water worldwide, therefore a selective and sensitive technique is necessary. A Simplex Centroid Experimental Design was used for the optimization of the IIP synthesis to maximize the anodic peak current (Iap) corresponding to the analytical signal to As(III). The proportions of the composite mixture and the parameters related to the load of the IIP were evaluated, while the DPASV parameters were optimized by a Taguchi design. The higher Iap obtained using the CPE-IIP respect to a single CPE, and a CPE-non-imprinted polymer (NIP), confirms the existence of the recognition cavities of the IIP. Two linear trends were obtained (0.026 to 0.075) mg L⁻¹ and from (17.00 to 700) mg L⁻¹; and a limit of detection (LOD) of 0.007 mg L⁻¹. The proposed electrochemical methodology was successfully applied to determine As(III) in commercial, tap, and dam water samples with and without acid digestion obtaining recovery percentages close to 99.74% suggesting that the digestion pretreatment is not required for this kind of samples. The As-IIP presented the capability to recognize As(III) ions in diverse matrices as demonstrated in the selectivity study.