Extreme trace analysis of the elements—the state of the art today and tomorrow. Plenary lecture

Abstract

The main aim of innovative elemental analysis is the improvement of analytical methods in terms of power of detection, reliability and economy. In routine analysis, there is a definite trend towards fully computerised, simultaneous or sequential multi-element methods that offer savings in both manpower and time. Extreme trace analysis, on the other hand, which involves ng g^–1 and pg g^–1 levels, usually cannot be achieved by routine cost-saving methods owing to the inadequate power of detection and the growing uncertainty of the results as lower and lower concentration levels are reached.

The costs of erroneous decisions based on unreliable or wrong analytical results are often greater than the savings in manpower costs achieved by employment of direct instrumental methods. It is therefore the responsibility of the analyst to find the right strategy, taking into consideration the economic viewpoints in each instance and realising that expert knowledge, experience and critical capability are often to be valued more highly than the employment of the newest types of apparatus that are currently so fashionable.

Improvements in both detectability and reliability in the determination of very low concentrations are usually achieved by first carrying out basic research, often involving contributions from techniques based on a wide range of principles, particularly with regard to more sensitive excitation sources with lower inter-element interferences.

After a brief systematic discussion of the most important principles of atomic spectrometric methods—those based on the absorption, emission and fluorescence of electromagnetic radiation and also on emitted ions and atoms—-a critical comparison is given of new developments in determination methods, e.g., atomic absorption spectrometry, optical emission spectrometry, coherent forward scattering, laser-enhanced ionisation spectrometry, atomic fluorescence spectrometry, X-ray fluorescence analysis and mass spectrometry.