Observation of Atom and Ion Clouds Produced from Single Droplets of Sample in Inductively Coupled Plasmas by Optical Emission and Laser-Induced Fluorescence Imaging

Abstract

An instrument to obtain optical emission and laser-induced fluorescence images of atom or ion clouds, each produced from isolated, monodisperse droplets of sample in an inductively coupled plasma, is described. An excimer laser pumped dye laser is used to produce a large (28-mm × 24-mm) beam for saturated fluorescence from atoms or ions throughout a large portion of the ICP. An intensified charge-coupled device (ICCD) detects optical emission or laser induced fluorescence snapshot images at the focal plane of an aberration-corrected slitless spectrograph. Images produced from a single laser pulse can be detected. Double-exposure emission images with 1-μs gate times can be acquired to monitor the movement of atom or ion clouds produced from a single droplet of sample solution. Variations in the number of atoms or ions produced as a function of time (or height) in the plasma can be monitored. Excitation in the plasma can be assessed from ratios of emission to fluorescence intensities.

Single Particle ICP-MS: Advances toward routine analysis of nanomaterials

“…Sufficient time is required in the hot ICP to completely vaporize the nanoparticles [31,81,82]. After vaporization, atomization, and ionization, a cloud of mainly elemental ions (for the majority of elements in the Periodic Table) is produced [83,84]. The location along the center channel where vaporization and ionization are complete can depend on the chemical composition and size of the particles, particularly for particles that are much greater than 100 nm in diameter [32].…”

“…When operating conditions of the sample introduction system are optimized for maximum ICP-MS signal creating monodisperse droplet injection into the radial center of the center channel of the plasma, the ion cloud is approximately 4 to 10 mm wide when it reaches the sampling orifice [84,85]. At a typical plasma gas velocity of~20 m/s, the duration of the particle-generated signal peak is therefore typically 200 to 500 μs.…”

Toward a Fuller Understanding of Analytical Atomic Spectrometry

“…This behavior is consistent with what has been termed a lateral diffusion interference. 2,[34][35][36][37][38] In this hypothesized mechanism, addition of an interfering species causes earlier release of analyte atoms and ions from the volatilizing sample aerosol. In turn, this earlier release provides more time for vaporization and diffusion to occur at any particular point higher in the plasma.…”

Double-Viewing-Position Single-Particle Inductively Coupled Plasma-Atomic Emission Spectrometry for the Selection of ICP Sampling Position in SP-ICP Measurements

“…Direct imaging of the entire plume also requires a large slit width (a few mm). 40 In contrast, ICP-AES with photomultiplier tube (PMT) detectors measures ICP emission at a nominal observation position over the slit height of the spectrometer. For slit height that is small relative to the dimension of the ion plume, the method can be used to determine the dimension of an ion plume by measuring the time-resolved emission of the plume as it moves up the plasma.…”

“…The use of dry sample particles avoids the convoluted effects of droplet evaporation and particle vaporization. Several studies have used a monodisperse microdroplets generator 2,4,5,46-49 and a monodisperse dried microparticulate injector 40,50,51 to produce monodisperse droplets reproducibly to study the local effects of the droplet evaporation and particle vaporization on plasma cooling, excitation conditions, and emission intensity.…”