Spectrochimica Acta Part B 57 (2002) 243–260 0584-8547/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0584-8547 Ž 01 . 00367-6 Corrosion of transversely heated graphite tubes by iron and lanthanum matrices H.M. Ortner *, U. Rohr , G. Schlemmer , S. Weinbruch , B. Welz a, a b c d Department of Chemical Analytics, Institute of Material Science, Darmstadt University of Technology, Petersenstr. 23, a D-64287 Darmstadt, Germany Perkin Elmer, P.O. Box 10 17 61, D-88647 Uberlingen, Germany b ¨ Institute of Mineralogy, Darmstadt University of Technology, Schnittspahnstr. 9, D-64287 Darmstadt, Germany c Department of Chemistry, Federal University of Santa Catarina, 88040-900 Florianopolis, SC, Brazil d Received 23 October 2000; accepted 6 October 2001 Abstract An in-depth study of corrosion phenomena in transversely heated graphite atomizers (THGA), caused by iron and lanthanum matrices, was performed by combining a variety of techniques. Analytical performance was determined by lifetime measurements under recommended conditions for vanadium determination. Average mass loss per atomization cycle and change of electrical resistivity were measured and compared to respective data for mineral acid matrices. Morphological changes of inner tube surfaces related to the corrosive attack were studied by scanning electron microscopy and compared to literature data of respective changes found for longitudinally heated graphite atomizer systems. Qualitative and quantitative depth profiles through the platform wall and through the tube wall were determined by wavelength-dispersive X-ray analysis in the electron microprobe. They were found to be dramatically different for iron and lanthanum. A quantitative evaluation of the remaining matrix elements after total tube system lifetime also revealed an essential difference between iron and lanthanum. Carbide formation and high temperature diffusion were discussed in detail for iron and lanthanum and were related to the observed phenomena. A combination of all these results, with data of semi-quantitative particle analysis and data from speciation studies by precision measurements of the line shifts for the C K X-ray emission line, allowed a profound description of a phenomena occurring during one atomization cycle related to corrosion.  2002 Elsevier Science B.V. All rights reserved. Keywords: Corrosion; THGA tubes; Fe and La matrices 1. Introduction It is well known from routine work with graphite furnace atomic absorption spectrometry (GFAAS) that certain matrices cause pronounced tube system * Corresponding author. Tel.: q49-6151-166379; fax: q49- 6151-166378. E-mail address: h.ortner@hrzpub.tu-darmstadt.de (H.M. Ortner). corrosion with the important economic conse- quence of greatly reduced analytical and total tube lifetimes w1x. One of the most corrosive matrices of practical importance is iron w2x. Lanthanum was proposed as a matrix modifier for the determina- tion of lead w3,4x and other heavy metals in biological materials w4,5x as early as 1973. The most widespread application of lanthanum as mod- ifier is in the determination of phosphorus w6,7x.