Review Glow discharge atomic spectrometry for the analysis of environmental samples Ð a review Stephane Baude, a Jose  A. C. Broekaert, b Daniel Delfosse, c Norbert Jakubowski, d Lars Fuechtjohann, e Nestor G. Orellana-Velado, f Rosario Pereiro f and Alfredo Sanz-Medel f a Commisariat a Á l'Energie Atomique (CEA/DIF/DASE/RCE), De Âpartement Analyse et Surveillance de l'Environnement, F-91680 Bruye Áres-le-Chatel, France b Institut fu Èr Analytische Chemie, Universita È t Leipzig, Linne Âstr. 3, D-04103 Leipzig, Germany c Eidgeno Èssisches Materialpru Èfungsamt (EMPA), Abteilung 126, CH-3602 Thun, Switzerland d Institut fu Èr Spektrochemie und Angewandte Spektroskopie, Bunsen-Kirchhoff-Str. 11, D- 44139 Dortmund, Germany e Institut fu Èr Analytische Chemie, Universita Èt Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany f University of Oviedo, Department of Physical and Analytical Chemistry, Julian Claveria 8, E-33006 Oviedo, Spain Received 19th May 2000, Accepted 29th August 2000 First published as an Advance Article on the web 4th October 2000 1 Introduction 2 Samples and sample preparation 2.1 Powdered and particulate samples 2.2 Liquid solutions 2.3 Gases and volatilised samples 2.4 Calibration standards and certi®ed reference materials 3 Glow discharge optical atomic spectrometry 3.1 Atomic emission spectrometry of glow discharges with planar cathodes 3.2 Atomic emission spectrometry of glow discharges with hollow cathodes 3.3 Glow discharges as atom reservoirs for atomic absorption and atomic ¯uorescence spectrometry 4 Glow discharge mass spectrometry 5 Future trends 6 Conclusion 1. Introduction Glow discharges (GD) have been used as sources for atomic spectrometry for many years. First studies with hollow cathode (HC) discharges go back to Paschen. 1 However, it was the 1960's before they were studied in more detail as spectrometric radiation sources. A strong impulse came from the work of Grimm, 2 who developed a ¯at cathode dc (direct current) discharge, which proved to be very useful both for bulk and for depth-pro®le analysis of conducting samples, as also described by Laqua. 3 Reviews on the early work with glow discharges, which at the beginning were mainly used as radiation sources for atomic emission spectrometry, were written by Mavrodineanu 4 and Broekaert, 5 whereas Caroli reviewed the work with hollow cathodes. 6 Glow discharges were also developed as powerful ion sources for mass spectrometry. Soon a wide variety of geometries such as pin and different ¯at sample arrangements were investigated, reports on different spectroscopic techniques with these sources were published 7 and a book on glow discharge atomic spectroscopy was published by Marcus. 8 A further impetus for glow discharges normally operated with a direct current (dc) in atomic spectrometry was given by the development of suitable radio frequency (rf) sources, which allow a direct analysis of electrically non-conducting samples, as described by Marcus. 9±11 Further, more knowledge on the processes occurring in glow discharges became available 12 and these sources also started to be used routinely for in-depth pro®le analysis in metallurgical samples. 13 Until recently the diagnostics of the analytical glow discharge sources were scarcely investigated. With the modelling work of Bogaerts and Gijbels, 14 an evaluation of the number densities for different species and the related atomic emission line intensities in the different locations of the plasma was possible 15 and the description of sputtering pro®les was established. With glow discharges of different shapes and at different working conditions, samples of different states of aggregate can be analyzed. Accordingly, these sources can be used for solving different analytical tasks and challenges in environmental analytical chemistry. The different glow discharges described can be used in optical atomic spectrometry as well as in mass spectrometry for different tasks. They can be used for analyses of samples from the different areas of the environment, namely air including airborne dust, solid samples such as sediments and soils as well as liquid samples such as waters, and also for analyses of various biological ¯uids. Through coupling with separation methods or even directly, signals stemming from different species of the same element can be detected separately, which makes speciation possible. This review will deal with the possibilities offered by different types of glow discharges for the determination of elements within a very wide concentration range of species in the different sections of the environment; it will show the lines of development in atomic emission spectrometry, atomic absorption and atomic ¯uorescence work, also with laser sources, and in mass spectrometry. In a number of cases sampling approaches and analytical ®gures of merit will be discussed and the corresponding applications as well. 2. Samples and sample preparation In environmental analysis, the most interesting samples consist of powders and particles (sediments, soil, airborne dust), dried organic substances (from animals or plants), gases and liquids or solutions containing the analytes to be analysed. Glow discharge spectroscopy (GDS) is a relative method, which means that calibration is required for quanti®cation, because the sensitivity strongly depends on various factors such as geometry and conditions of sample and source or chosen discharge working conditions (pressure, power, voltage, current). 2.1. Powdered and particulate samples The advantage of glow discharges for powdered and particulate samples is that sample preparation is extremely simple in comparison to other techniques of atomic spectroscopy which require complete dissolution of the sample. Dissolution for some of the matrices described is dif®cult, laborious and time 1516 J. Anal. At. Spectrom., 2000, 15, 1516±1525 DOI: 10.1039/b004039h This journal is # The Royal Society of Chemistry 2000 Published on 04 October 2000. Downloaded on 27/05/2013 15:50:12. View Article Online / Journal Homepage / Table of Contents for this issue