Atomic Absorption Measurements in an Inductively Coupled Plasma Using Spatial Dispersion of the Plasma Image

Abstract

An optical design is presented for inductively coupled plasma atomic absorption spectroscopy (ICP-AAS). In this configuration, a see-through ICP torch is oriented co-axially along the optical axis. Incident radiation from a hollow cathode lamp (HCL) is collimated and passed through the center of the plasma. The plasma is located at a distance less than the focal length of the camera lens while the monochromator was positioned at its focal length. This results in the efficient transfer of the HCL radiation while minimizing the amount of ICP emission reaching the PMT detector through the dispersion of the background and plasma emission. Solutions containing Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Tl and Zn were analyzed both individually and collectively with a background concentration of 1000 mg l^–1 uranium. For comparison purposes the same solutions were analyzed with a commercial (radial viewing) ICP-AES instrument. Comparing the detection limits for each element in the multi-element solution with the single element solution, no significant degradation can be seen. This is in comparison to a degradation of measured detection limits for emission by a factor of 423 for the same solutions. Aluminum in the multi-element solution was found to give a poor response on both the ICP-AAS and ICP-AES.