Photothermal Lens Spectroscopy for Detection of Metallic Impurities in Water

In this paper, we studied the potential of photothermal lens spectroscopy technique in detection of trace amounts of contaminants in water. We used experimental setup with two continuum lasers as pump and probe beams. Different concentrations of iron ion solved in combination of 4 to 1 water to ethanol solvent was studied. To increase the technique sensitivity, lock-in amplifier and intensity modulation of the pump beam have been used. Also, the photothermal signal dependence on modulation frequency was investigated and the best working frequency according to signal enhancement and low standard deviation was 6 Hz. The obtained Limit of detection for doubly ionized iron at the optimum frequency was as low as 20 ng/L.