Effect of permanent modifiers on the temperature of the analytical zone of a graphite furnace

Abstract

543.422Using tungsten and zirconium as examples, we have studied the effect of permanent modifiers on the temperature of the analytical zone of a graphite furnace in an atomic absorption spectrometer. We observed an increase in the temperature of the analytical zone of the modified furnace during atomization of the sample, and we give an explanation for this effect.Keywords: atomic absorption spectrometry, graphite furnace, temperature of the analytical zone, permanent modifiers.Introduction. Atomic absorption spectrometry with electrothermal atomization (ETA-AAS) today has achieved the theoretically possible sensitivity limit of the method, which is mainly determined by the negative effect of the chemical matrix of the sample on the analysis results. Two approaches are widely used in atomic absorption spectrometry to eliminate matrix interferences: preliminary chemical separation of the analyte elements (analytes), and chemical modification of the matrix [1]. The latter is currently an indispensable component of the STPF (stable temperature platform furnace) concept in ETA-AAS, in order to improve the volatility of the matrix.Despite the fact that many papers are devoted to study of modifiers (see, for example, [1-4]), the most effective modifiers to date have been selected empirically. In order to make such a selection a priori, based only on the chemical composition of the analyte sample and the properties of the analyte, we need a detailed study of the processes involved in the impact of modifiers on the major atomization parameters, especially on parameters determining the intensity and shape of the analytical signal. One of the most important shaping parameters is the temperature of the gas phase in the analytical zone of the graphite furnace.The aim of this work was to study the effect of permanent modifiers based on zirconium, tungsten, and palladium compounds on the temperature of the analytical zone of a graphite furnace.Experimental Section. Equipment. The studies were conducted on a KAS 120.1 atomic absorption system (SELMI, Ukraine) with deuterium corrector for non-atomic absorption. We used LT-6 spectral lamps to detect lead, λ = 368.3 nm and 280.2 nm. A dispensing device was used to introduce a 10 μL sample into a standard furnace with a pyrolytic graphite coating (equivalent to HGA-500). The atomic absorption signal was scanned and processed using a personal computer. The equipment used allowed us to follow the intensity of atomic absorption over time with step 0.016 s.The temperature conditions for the furnace for measurement of atomic absorption by lead were as follows: drying for 30 s at 363 K, pyrolysis for 10 s at 773 K, atomization for 5 s at a temperature of 2473 K. The electron microscope images were obtained on an RE ′ MMA-102 scanning electron microscope (SELMI, Ukraine) in secondary and backscattered electron modes with accelerating voltage 20 kV.Reagents and reference standards. We used aqueous solutions with lead concentration 0.5 g/L, prepared from state standard samples (6077-91). A...

Surface studies on graphite furnace platforms covered with Pd, Rh and Ir as modifiers in graphite furnace atomic absorption spectrometry of tellurium

“…Particularly in the case of the platinum group modifiers (PGMs), several studies have been published with the aim of explaining their mechanisms of action [20][21][22], in some cases through comparison with classic modification as reported recently by Borges et al [23].…”