Detection of chromium aerosol using time-resolved laser-induced plasma spectroscopy

Time-resolved laser-induced plasma spectroscopy (LIPS) has been used as a tool for the detection of chromium in aerosol. In this article, LIPS has been used to achieve the lowest limits of detection for chromium (400 ng/dscm) in droplets. A comparison with other LIPS instruments and inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows that the limits of detection for chromium metal in aerosol range from 12 to 60 mu g/dscm and 200 ng/dscm for LIPS and ICP-AES, respectively. We have studied the effects of laser wavelength, excitation energy, and optimum spectrometer delay time to optimize these low limits of detection. A Nd:YAG laser with output wavelengths of 1064, 532, and 266 nm has been used to study the effects of wavelength on laser energy and aerosol interactions-specifically, plasma initiation and efficiency of ionization in the detection of elemental species. Measured time-resolved spectra are used to establish the most appropriate time delay producing an optimum signal-to-background ratio.