Investigation of chemical modifiers for phosphorus in a graphite furnace using high-resolution continuum source atomic absorption spectrometry Fábio G. Lepri a , Morgana B. Dessuy b , Maria Goreti R. Vale b , Daniel L.G. Borges a , Bernhard Welz a, ⁎ , Uwe Heitmann c a Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis – SC, Brazil b Instituto de Química, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 91501-970 Porto Alegre – RS, Brazil c ISAS – Institute for Analytical Sciences, Department of Interface Spectroscopy, Albert-Einstein-Str. 9, 12489 Berlin, Germany Received 26 April 2006; accepted 9 August 2006 Available online 22 September 2006 Abstract Phosphorus is not one of the elements that are typically determined by atomic absorption spectrometry, but this technique nevertheless offers several advantages that make it attractive, such as the relatively great freedom from interferences. As the main resonance lines for phosphorus are in the vacuum–ultraviolet, inaccessible by conventional atomic absorption spectrometry equipment, L´vov and Khartsyzov proposed to use the non-resonance doublet at 213.5 / 213.6 nm. Later it turned out that with conventional equipment it is necessary to use a chemical modifier in order to get reasonable sensitivity, and lanthanum was the first one suggested for that purpose. In the following years more than 30 modifiers have been proposed for the determination of this element, and there is no consensus about the best one. In this work high-resolution continuum source atomic absorption spectrometry has been used to investigate the determination of phosphorus without a modifier and with the addition of selected modifiers of very different nature, including the originally recommended lanthanum modifier, several palladium-based modifiers and sodium fluoride. As high-resolution continuum source atomic absorption spectrometry is revealing the spectral environment of the analytical line at high resolution, it became obvious that without the addition of a modifier essentially no atomic phosphorus is formed, even at 2700 °C. The absorption measured with line source atomic absorption spectrometry in this case is due to the PO molecule, the spectrum of which is overlapping with the atomic line. Palladium, with or without the addition of calcium or ascorbic acid, was found to be the only modifier to produce almost exclusively atomic phosphorus. Lanthanum and particularly sodium fluoride produced a mixture of P and PO, depending on the atomization temperature. This fact can explain at least some of the discrepancies found in the literature and some of the phenomena observed in the determination of phosphorus using line source atomic absorption spectrometry. © 2006 Elsevier B.V. All rights reserved. Keywords: Phosphorus; Electrothermal atomic absorption spectrometry; High-resolution continuum source atomic absorption spectrometry; Chemical modifiers; Molecular absorption 1. Introduction The main problem in the determination of phosphorus with all atomic spectrometric techniques is the fact that the resonance lines of this element are situated between 167.16 nm and 178.77 nm in the vacuum–ultraviolet (UV). This spectral range is not accessible at all with conventional atomic absorption spectrometry (AAS) and requires special equipment in optical emission spectrometry [1]. L´vov and Khartsyzov [2] were the first ones to propose the use of the non-resonance doublet at 213.5 and 213.6 nm as alternate lines for the determination of phosphorus. These lines originate from the 2 D 0 3/2 and 2 D 0 5/2 terms, respectively, which are 1.4 eV above the 4 S 0 3/2 ground state, so that a reasonable population could be expected at temperatures of about 2900 K, which can easily be attained in a Spectrochimica Acta Part B 61 (2006) 934 – 944 www.elsevier.com/locate/sab ⁎ Corresponding author. Tel./fax: +55 48 3331 6850. E-mail address: welz@qmc.ufsc.br (B. Welz). 0584-8547/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2006.08.001