Analytical atomic spectrometry going into the next millennium: photons or ions, atoms or molecules?

摘要

Analytical atomic spectrometry seems to be suffering a sort of 'identity crisis' at the sunset of this millennium. The field has undergone profound changes and the rate of change has increased dramatically in the last decade. For many years the main goal of analytical atomic spectrometry was to provide atomic/elemental information on the composition of matter via the development of spectrochemical knowledge, instrumentation and determination strategies for the around 90 elements of the Periodic Table. Nowadays, however, we are witnessing a come back of many atomic spectroscopists to look for molecular (species) information, in a sort of re-encounter with 'chemistry' without renouncing the advantages of traditional spectrochemistry (sensitivity and selectivity). As expected, this turning point in the goals of the discipline seems to have been accompanied by profound changes in analytical tools and techniques used in this field. After reviewing the strengths and weaknesses of photon-based 'workhorses' of present routine elemental analysis, the dramatic change introduced by the combination of an 'electrical' flame (ICP) and a quadrupole mass analyser (MS) in a 'recombinant' instrument, the ICP-MS, is highlighted. The ICP-MS success originated a spectacular revival of atomic inorganic-mass spectrometry. Almost any possible coupling of a classical spectrochemical ion source with any mass analyser (developed for organic mass spectrometry) is now being intensively investigated. In fact, the popularity and economical importance of atomic MS has increased dramatically in the last few years and this importance is discussed in terms of techniques commercially available and those under active development. In order to cope with present needs for chemical speciation information, atomic techniques are widening their scope to be able to provide molecular information. One approach consists of studying new MS instrumentation capable of producing both atomic (elemental information) and molecular (molecular ions and fragmentation) mass spectra in the same instrument. Additionally, an extra degree of specificity can be afforded by coupling powerful separation techniques (gas or liquid chromatography, capillary electrophoresis, etc.) to the above spectrometric instruments, which would eventually be able to provide elemental, molecular and perhaps structural information of the compound(s) responsible of a given chromatographic or electrophoretic peak. In brief, more ambitious goals, more powerful elemental detectors (based on both photon and ion measurements), more and more flexible hybrid techniques and more active cross-fertilization with other fields of science are good indicators of a bright future for analytical atomic spectrometry entering the next millennium. [References: 83]