Detection enhancement at parts per billion level of aluminum in water droplets by a combination of acoustic levitation and nanoparticle enhanced laser induced breakdown spectroscopy

Abstract

Nowadays, detecting metals dissolved in water is a paramount health concern, due to the sustained contamination of water reservoirs for human consumption. Limits of detection in the sub-ppm range are required, but a simple and fast method suitable to measure such levels is not easy to implement. Laser induced breakdown spectroscopy (LIBS) is a simple technique and can be employed on field, but its lack of sensitivity at sub-ppm has restricted its application. With the recent use of metallic nanoparticles to enhance the plasma emission, ppb limits of detection are achieved. In combination with liquid droplet acoustic levitation, this work demonstrate that few ppb limit of detection is possible measuring directly in the liquid sample without any pretreatment. When limits of detection obtained with and without the use of metallic nanoparticles are compared, improvements up to three orders of magnitude were obtained for aluminum dissolved in water, keeping similar relative standard deviations in the range of 10–20%. It is also important to note that after optimization, excitation energies as low as 1 mJ are sufficient to generate spectra with signal to noise ratios around 7 at concentrations below 1 ppb. The resulting spectra are suitable to be analyzed for quantification, opening the real possibility of its implementation on field applications.