Organised surfactant assemblies in analytical atomic spectrometry

• Published in: Spectrochimica Acta Part B: Atomic Spectroscopy 1999-02, Vol.54 (2), p.251-287
• Main Authors: Sanz-Medel, Alfredo, Fernandez de la Campa, Maria del Rosario, Gonzalez, Elisa Blanco, Fernandez-Sanchez, Maria Luisa
• Format: Article
• Language: English
• Subjects: analytical atomic spectrometry; Analytical chemistry; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; General, apparatus, technics of preparation; micellar and vesicular chromatography; Spectrometric and optical methods; Surfactant assemblies; trace element speciation
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/S0584-8547(98)00241-9

The use of surfactant-based organised assemblies in analytical atomic spectroscopy is extensively and critically reviewed along three main lines: first, the ability of organised media to enhance detection of atomic spectroscopic methods by favourable manipulation of physical and chemical properties of the sample solution second, the extension of separation mechanisms by resorting to organised media and third a discussion of synergistic combinations of liquid chromatography separations and atomic detectors via the use of vesicular mobile phases. Changes in physical properties of sample solutions aspirated in atomic spectrometry by addition of surfactants can be advantageously used in at least four different ways: (i) to improve nebulisation efficiency; (ii) to enhance wettability of solid surfaces used for atomisation; (iii) to improve compatibility between aqueous and organic phases; and (iv) to achieve good dispersion of small particles in “slurry” techniques. Controversial results and statements published so far are critically discussed. The ability of surfactant-based organised assemblies, such as micelles and vesicles, to organise reactants at the molecular level has also been applied to enhance the characteristics of chemical generation of volalite species of metals and semi-metals (e.g., hydride or ethylide generation of As, Pb, Cd, Se, Sn, and cold vapour Hg generation) used in atomic methods. Enhancements in efficiency/transport of volatile species, increases in the reaction kinetics, stabilisation of some unstable species and changes in the selectivity of the reactions by surfactants are dealt with. Non-chromatographic cloud-point separations to design pre-concentration procedures with subsequent metal determination by atomic methods are addressed along with chromatographic separations of expanded scope by addition of surfactants to the conventional aqueous mobile phases of reversed-phase high-performance liquid chromatography. Finally, the synergistic effect of using vesicles to improve both the separation capabilities of reversed-phase HPLC and the detectability of atomic detectors by on-line vesicular hydride generation is described. In particular, the possible separation mechanisms responsible for micellar and vesicular mobile phases in reversed-phase chromatographies are analysed and compared. The possible effect of modification of stationary phases by monomers of the surfactants should also be taken into account. The application of such on-l