Abstract
Lead is one of the most toxic metals for living organisms: once absorbed by soft tissues, it is capable of triggering various pathologies, subsequently bioaccumulating in the bones. In consideration of this, its detection and quantification in products for human consumption and use is of great interest, especially if the procedure can be carried out in an easy, reproducible and economical way. This work presents the results of the electroanalytical determination of lead in three different commercial products used as progressive hair dyes. Analyses were performed by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) using a composite cork–graphite sensor in 0.5M H2SO4 solution or 0.1M acetate buffer (pH 4.5), in the presence and absence of hair dye samples. The H2SO4 solution gave better results in terms of analyte sensitivity than the acetate buffer electrolyte. In both cases, well-defined signals for lead were obtained by DPSV analyses, enabling the calibration curve and figures of merit to be determined. The limits of detection (LOD) were found to be approximately 1.06 µM and 1.26 µM in H2SO4 and acetate buffer, respectively. The DPSV standard addition method was successfully applied to quantify the lead in hair dye samples, yielding values below 0.45% in Pb. All three analyzed samples were shown to comply with the limit set by the Brazilian Health Regulatory Agency, i.e., 0.6% lead in this type of product. The comparison of the electroanalytical results with those obtained by the reference method, based on the use of inductively coupled plasma optical emission spectrometry (ICP–OES), confirmed that the electroanalytical detection approach is potentially applicable as a strategy for quality control.
Highlights
Hair coloring is a fashion practice used by many people around the world
Hair salons use temporary or permanent hair dyes to give a new look to countless people; the process leads to the release into the sewer system of a large amount of polluted water containing residues of dyes [1]
Synthetic and mineral hair dyes are available on the market, and dyes are distinguished by the material of manufacture [2]
Summary
Hair salons use temporary or permanent hair dyes to give a new look to countless people; the process leads to the release into the sewer system of a large amount of polluted water containing residues of dyes [1]. In the case of lead, the composition of hair dyes contains it in the form of lead acetate. By reaction with the sulfur of the keratin of the hair, a mixture of metal oxides and insoluble sulfide is formed, which is responsible for the gradual darkening of the white strands [3]. Due to its bio-accumulative character, once lead is absorbed, various organs of the body can be poisoned [6]. For this reason, it is necessary to monitor pollution and control exposure to lead
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