SPECTROCHIMICA ACTA PART B ELSEVIER Spectrochimica Acta Part B 52 (1997) 1377-1394 Adaptation of the filter furnace atomizer for atomic absorption determination of less volatile metals 1 D.A. Katskov a'*, P.J.J.G. Marais a, V.J. Katkovnik b, P. Tittarelli c ~Department of Chemistry and Physics, Technikon Pretoria, Private Bag X680, Pretoria, South Africa bDepartment of Statistics, University ~ South Africa, PO Box 392. Pretoria, South Africa ~Stazione Sperimentale per i Combustibili, Viale A. De Gasperi 3. 20097 San Donato Milanese, MI, ltalv Received 30 July 1996; accepted 22 October 1996 Abstract The filter furnace atomizer (FF), which has already been proposed for electrothermal atomic absorption spectrometry, provides enhanced sensitivity, a reduction of interferences and reduced analytical time. The main disadvantage of the FF is the rapid destruction of the filter at the atomization temperatures of less volatile or carbide-forming elements. In the current work, radiative heat exchange between the components of the FF was considered to be predominant at high temperature. The thermal behaviour of the FF was therefore examined at fast heating rate as a function of its configuration, the type of graphite used for the components, and the voltage applied. The optimal combination of electrical resistivity, relative dimensions and mass of the FF components was determined for the HGA-500 atomizer. The improvements resulted in a significantly increased lifetime of the FF in the multiple determination of Al, As, Co, Cr, Cu and Ni. The filter withstood 150 firings at 2600°C (hold time 15 s) in the determination of Cr. The theoretical approach can be applied to different types of atomizers. © 1997 Elsevier Science B.V. Keywords: Electrothermal atomic absorption spectrometry; Filter furnace; Heat exchange; Matrix interference minimization; Theoretical modelling 1. Introduction The main advantages of the filter furnace (FF), a new atomizer for electrothermal atomic absorption spectrometry (ET AAS), are the increase of the sampling volume up to 100/zl, the short drying period (10-15 s), a two- to threefold improvement in detection limit, and efficient reduction of background and chemical interferences [1-5]. The general design of the FF is displayed in Fig. 1(a). ~ Presented at the Second European Furnace Symposium, St. Petersburg, Russia, May 1996. * Corresponding author. Liquid samples are dispensed into the ring cavity between the pyrocoated tube 1 and the filter 2 (made of porous graphite), dried, ashed and atomized in accordance with the appropriate program. After dry- ing, fine particles of the residue are scattered over the fibre 3. During the atomization stage the sample vapours enter the analytical zone in the central part of the filter through the pores of the graphite. The advantages of the FF are fully displayed during the evaporation of volatile elements and matrices that do not form stable chemical compounds or solid solu- tions with graphite. The configuration of the filter and its material were chosen empirically to reach low detection limits [5]. The goal of that FF design was 0584-8547/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0584-8547(96)0 1622-9