Detection of zinc and lead in water using evaporative preconcentration and single-particle laser-induced breakdown spectroscopy

Detection of Ni, Pb and Zn in water using electrodynamic single-particle levitation and laser-induced breakdown spectroscopy

“…The obtained curve is then subtracted from the trace metal and background spectra. Compared with our previous approach, the limits of detection obtained using the EDB-LIBS method were clearly lower despite the significantly smaller solid angle for plasma emission collection; only 2.8 % of the angle used in reference [12]. The EDB-LIBS technique also consumes less energy due to the absence of the oven for water evaporation.…”

“…The time-averaged plasma excitation temperature during the detection time window of each 30 single-shots was estimated using the Boltzmann plot method and the suitable emission lines of nickel between 338 nm and 362 nm. The excitation temperature was found to be 5400 K on average with a standard deviation of 730 K. Earlier, we have shown that the trace metal analysis from monodisperse sodium chloride particles yields a linear calibration curve [12]. Because the standard error of the mean of 30 signals is only 2.6 %, we can estimate the limits of detection of the EDB-LIBS technique with a good certainty using simply the averaged signal obtained from the 5 ppm solution.…”

“…Sodium chloride was dissolved in the water before pouring it to the sample container of the EDB-LIBS setup to prevent the complete extinction of the sample material due to the evaporation. After the water has evaporated, the salt forms a hollow spherical particle where the trace metals for analysis are present as additives [12,24]. The size of the dry salt particle depends on the size of the initial droplet and the salt concentration, and it can be adjusted in the range of 1-20 µm.…”

“…Utilizing the added salt also for calibrating the signal intensity could further stabilize the signal [12] on conditions that the amount of salt is kept constant and the emission peaks of the internal standard element are not affected by changes in the sample composition. Sodium has been shown to cause matrix effects at the early stage of plasma due to the much lower boiling point than the trace metals [34].…”

“…A more suitable approach for a field device is the generation of aerosols from the sample solution that has been proposed for the fast sample preparation procedure for the LIBS analysis of liquid samples [9]. The measurement is conducted by analyzing the aerosol-rich air [9,10] or by focusing the pulse on a single aerosol particle [11,12]. Typically, plasma created in the center of a nebulized droplet cloud interacts with greater sample mass compared with the single-particle measurements, and a significant portion of the supplied energy is consumed to vaporize and dissociate the water from the droplets.…”