Ultrasonic-Assisted Digestion of Cement and Clinker Samples for the Determination of Manganese by Square Wave Cathodic Stripping Voltammetry

Abstract

Cement and clinker are complex samples and constitute a challenge for elemental analysis. Manganese, usually present in these matrices, can accumulate in bones, liver, the pancreas, kidneys, and brain and its monitoring is very important. This work presents an alternative method of sample treatment based on ultrasonic-assisted extraction for the determination of trace amounts of manganese in cement and clinker samples by square wave cathodic stripping voltammetry (SWCSV) on a gold working electrodes. The proposed extraction procedure occurs at room temperature inside closed vessels and uses 3.0 mol L−1 HCl solution, a less corrosive extractant compared to concentrated acids. Ultrasonic extraction was compared with conventional extraction by heating on hot plate and no significant differences between the two extraction methods were observed at the 95% confidence level. The possible use of H2O2 in the extraction process was evaluated but not used due to its interferences in the electrochemical determination of manganese. The SWCSV results obtained employing 0.20 mol L−1 H3BO3/0.10 mol L−1 KCl electrolyte at pH 6.5 produced two distinct linear regions of concentration for the analytical curve from 1.1 to 2.0 × 10−7 mol L−1 and from 2.0 to 3.2 × 10−7 mol L−1. The limits of detection and quantification were 3.1 × 10−8 mol L−1 and 9.8 × 10−8 mol L−1, respectively, and suitable for the proposed application. The results obtained by SWCSV were consistent with those obtained by flame atomic absorption spectrometry (FAAS) at the 95% confidence level.