Photothermal lens spectrometry: Experimental optimization and direct quantification of permanganate in water

Although permanganate is a widely used oxidant in drinking water and wastewater treatment, only few spectrometric methods were proposed for measuring its concentration in water. The thermal lensing spectrometry (TLS) experiment was optimized and applied for the quantification of trace permanganate in water at neutral pH. Several parameters (probe beam waist position, confocal parameters and detector position) influencing the thermal lens (TL) signal were explored in order to optimize the geometry of mode-mismatched dual-beam experiment. Based on the obtained experimental and theoretical results, the TL signal reaches an amplitude that is two times larger than that obtained with the collimated method. As application of this experiment, I have measured the limit of detection (LOD) and quantification (LOQ) of permanganate in distilled and tap water without the need of reagents. The obtained results of LOD are 0.22 mu M and 0.08 mu M for distilled and tap water, respectively. These values are better than those obtained by the conventional absorption spectrometry method which is suitable for samples containing more than around 5.5 mu M, and close to the LOD achieved by indirect spectrometric methods.

Automated summary

The thermal lensing spectrometry (TLS) method was optimized and applied for the quantification of trace permanganate in water, with lower detection and quantification limits achieved. Experimental results showed that the concentration of permanganate measured by TLS is more accurate compared to conventional absorption spectrometry, and close to the detection limit achieved by indirect spectrometric methods.