Solid sampling GFAAS and ICPMS for the determination of trace amounts of palladium

Abstract

The great importance of palladium in todays industry and its widespread use make the development of analytical methods that allow the reliable determination of this precious metal in a great variety of samples necessary. However, the determination of this element at trace and ultratrace levels, as often required, may be very challenging. Sample dissolution for palladium determination is frequently complicated, especially for environmental and geological analysis, requiring timeconsuming and cumbersome procedures, frequently involving the use of hazardous reagents (e.g., HF or HClO 4) [1-2]. Moreover, even the most sensitive analytical techniques face some difficulties in order to accomplish the determination of palladium at the ?g g-1 level and below. Neutron Activation Analysis (NAA) is a powerful technique, but for reliable ultratrace palladium determination the use of pre-concentration/separation steps is necessary [3-4]. Similar comments can be made for atomic absorption (AAS) or optical emission (OES) techniques [1,5,6]. Inductively coupled plasma-mass spectrometry (ICPMS) offers a higher detection power for this element, but the main problem for this technique is the well-documented occurrence of spectral interferences on all palladium isotopes due to the occurrence of isobaric nuclides and molecular and doubly charged ions. Many of these interferences cannot even be spectrally resolved when high resolution-ICPMS is used [7], and the low concentration of the analyte compared to the higher level of the interfering elements in many samples may make the use of separation/pre-concentration steps compulsory [8,9]. Literature on the development of different pre-concentration/separation steps for palladium determination is extensive. The use of selective chelating agents [1,5], ion exchange resins [9,10], electrochemical pre-concentration [11,12], and mercury or tellurium co-precipitation [13,14], are some of the solutions proposed. However, while many of these methods can provide reliable results, they are often time-consuming and may suffer from incomplete recovery and/or contamination problems. Taking all these factors into consideration, the development of methods that permit the direct determination of palladium in solid samples could be a logical choice to deal with this problem. In this way, it would be possible to improve the sensitivity (by avoiding the dilution that usually accompanies sample digestion), considerably increase the sample throughput (by eliminating the digestion and pre-concentration steps) and reduce the risk of contamination/losses. It is the main goal of this chapter to present information on the current potential of some solid sampling techniques that, according to recent advances reported in the literature, may be well suited for the fast and reliable direct determination of Pd in different samples. The techniques covered in this work include solid sampling-graphite furnace atomic absorption spectrometry (SS-GFAAS), solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry (SS-ETVICPMS) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS).