Square-wave adsorptive stripping voltammetry for the determination of cyclofenil after photochemical derivatization

Square-wave adsorptive voltammetry was applied for the determination of cyclofenil at ultra-trace levels. Due to the unstable behavior of cyclofenil, the analyte photochemical derivative was used for quantification. This stable analyte photoderivative was pre-concentrated (30 s accumulation time) on the hanging mercury drop electrode (HMDE), using Britton-Robinson buffer (pH 9) as the supporting electrolyte. Under these conditions, the cyclofenil photoderivative presented one reduction peak maximum at −1280 mV. Instrumental and experimental parameters were carefully optimised. Limit of detection of 1.5 × 10−8 mol l−1, was achieved with a linear dynamic range from 5 × 10−8 to 6 × 10−6 mol l−1. This analytical approach was tested through the analysis of one commercial pharmaceutical formulation and analyte spiked urine samples. While no interferences were observed for the analysis of the pharmaceutical tablet, urine samples imposed interferences that were corrected by using the analyte addition technique. Recovery tests enabled results from 93.6 to 106.5%. Repeatability of the measurements was below 7% at 1 × 10−6 mol l−1 concentration level.