Analytical techniques for trace element determinations in plant tissues

Recent developments in the analytical procedures for trace element assay in plant tissue ash have been toward automated procedures utilizing highly sophisticated instrumentation such as activation analysis, flameless atomic absorption spectroscopy, emission spectroscopy with plasma excitation, x‐ray fluorescence spectroscopy and voltometry. These techniques provide the analyst the ability to determine the concentration of trace elements well into the subparts per million range. Although the instrumentation procedures have their limitations and require special skills on the part of the analyst, the problem of sample preparation is still a major concern limiting the assay for a number of important elements. Trace level determination for elements, As, B, Cd, Co, Hg, Mo, Pb and Se is difficult. Acceptable reference standards are still needed as the current U.S. National Bureau of Standard Reference materials are not completely adequate. There is considerable evidence that there is significant element to analytical technique correlation which means the assay technique is a factor in the concentration found. This paper discusses procedures for sample preparation and analysis by various analytical procedures and reviews current and future analytical needs. The analyst who must determine the trace element content of a plant tissue sample faces many decisions and potential difficulties, beginning with sample collection and following through until the final result is obtained in the laboratory. To collect, store, transport, prepare and analyze without adulterating the sample and to obtain a statistically desired result is not an easy task. Since many of the trace elements and their effect on plants frequently relates to environmental aspects, the excellent series of editorials in Analytical Chemistry by the editor1,2,3,4 on the association between analytical chemistry and environmental science are quite timely. Dr. Laitinen provides an excellent overview of the problem as viewed by an analytical chemist. An excellent review paper by Lisk5 points to the problems and potential solutions when working with environmental samples and trace constituents, particularly those elements which are considered toxic elements. He covers most of the topics discussed in this paper.