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Issue 2, 2003
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Characteristics of atomic absorption calibration curves with the transversely heated graphite furnace

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Abstract

Calibration curves with two quasi-linear sections (“double sloping”) were observed for the medium volatile elements, Cr and Cu, with the use of a SIMAA 6000 graphite furnace atomic absorption spectrometer under interrupted internal gas flow conditions. If a standard transversally heated graphite atomizer (THGA) tube was shortened by 0.5 mm at both of its ends, (i.e. the gaps were enlarged between graphite furnace housing and tube ends), a stronger declination of the calibration curves resulted. Elements with fairly high diffusion coefficients (>5.8 cm2 s−1) and with short appearance time of their transients (<0.6 s), such as Cr and Cu, have shown the most characteristic sensitivity drop towards higher concentrations. This anomalous feature could be eliminated in three different ways; (1) by applying end-capped THGA tubes, (2) using mini-flow (50 cm3 min−1) conditions during the atomization stage, and (3) by adding Pd–Mg chemical modifier. For the low volatile Mo and V, the calibration curves had no irregular shape. For Ag, Co, Cr, Cu, Mn and Ni, the mini-flow settings improved the linearity of the calibration curves and extended the upper limit of the linear calibration range by a factor of 1.5–2.0. The irregular characteristic of the analytical curves was interpreted as an increased vapour loss at higher analyte concentrations through the opened ends of the standard THGA tubes. This vapour loss was associated with the significantly diverse expulsion velocities of atoms, caused by the difference in temperature and concentration gradients, when evaporating amounts of analytes with more than one order of magnitude difference.

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Publication details

The article was received on 21 Aug 2002, accepted on 03 Dec 2002 and first published on 14 Jan 2003


Article type: Paper
DOI: 10.1039/B208198A
Citation: J. Anal. At. Spectrom., 2003,18, 105-110
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    Characteristics of atomic absorption calibration curves with the transversely heated graphite furnace

    L. Bencs, O. Szakács, N. Szoboszlai, Z. Ajtony and G. Bozsai, J. Anal. At. Spectrom., 2003, 18, 105
    DOI: 10.1039/B208198A

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