Determination of Methylparaben by Square Wave Voltammetry at Boron-Doped Diamond Electrode

Parabens have been widely used as preservative in personal care products, foods and drugs. However, due to their endocrine disruption and carcinogenic possible action, the quantification of these pollutants in several matrices is necessary. In this way, the present work has as objective, the development of an electroanalytical methodology using square-wave technique. The target molecule is the methylparaben (MePa), which will be determined using the boron-doped diamond electrode (BDD) as the work electrode. Several operating conditions and voltammetric parameters were studied seeking greater efficiency of the technique. Under chosen conditions, the measurements were realized in an electrochemical cell containing Ag/AgCl as the reference system and a platinum foil as auxiliary electrode. Several electrolyte solutions were tested and the best results were obtained in 0.2 molL^-1 phosphate buffer (pH 7.5). In such electrochemical cell, MePa  showed a well-defined square wave voltammetric peak at a potential around 0.8 V, whose peak currents are linearly proportional to the MePa concentration in the electrolyte. Adequate linearity (0.9986), as shown in figure 1, in the range of 0.5 to 30 mgL^-1, with limit of detection and quantification of 0.103 mgL^-1 and 0.344 mgL^-1, respectively, was found. The method was validated for the determination of MePa in a creek water sample, with low pollution content, obtained in Sao Carlos – SP county (S 21 59.670’ / W 047 54.183’). Spiked solutions of such water samples added to the buffer solution, showed recovery range between 68.40% a 106.15%, with a relative standard deviation (RSD) less than 6.8% (n=3). The method seemed to be sensitive to MePa and can be used for detection in others water samples. In future, we intended to use this method for detection of methylparaben in cosmetics creams.

Figure 1. Method calibration curve for determination of MePa. Concentrations: 0.5, 0.75, 1.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0 mgL^-1.