Investigation of the quartz cuvette surface contamination used for permanganate quantification in tap water by photothermal lens spectroscopy

Abstract

Abstract In this work, the PhotoThermal Lens (PTL) spectroscopy was used to investigate the contamination effect of the quartz cuvette on the quantification of permanganate concentration in tap water at neutral pH. Different permanganate solutions were prepared at a concentration range from 0.2 µM to 10 µM. The PTL signal measurements performed for samples having the same permanganate concentration in tap water increase continuously. Contrary to the solutions prepared in distilled water where the PTL signal remains constant for all the measurements. Thus, it results from that the main cause of this behavior is related to the decomposition reaction of permanganate in tap water giving rise to manganese dioxide, which then will be adsorbed on the optical window surfaces of the quartz cuvette. The contribution of the adsorbed amount on the PTL signal was examined and its variation was described based on Langmuir model. To remove this contamination effect caused by the adsorption process, three 0.1 M acidic solutions (HCl, H2SO4 and H3PO4) were applied separately for the cleaning of the optical window surfaces. The obtained results show that 4 min is sufficient to reach a desorption rate higher than 90% whatever the used acid.