Removal of water and hydrogen from graphite tubes investigated by electrothermal vaporization inductively coupled plasma mass spectrometry

Inductively coupled plasma-mass spectroscopy (ICP-MS) detection can be applied to study fundamental processes in the graphite furnace, The retention and high-temperature release of water/hydrogen and carbon under various furnace heating conditions are described in this work. Different feasible monitor masses were studied and the signal for (ArH+)-Ar-36 (m/z = 37) is shown to be indicative of the amount of water present. The release of carbon was monitored by measuring the integrated signal at m/z = 13. In our study no water was found in the vaporization step using blank correction of a dry tube. However, we observed an (ArH+)-Ar-36 Signal when the dry graphite tube was heated, even after up to 50 such heating cycles, This behavior was studied by monitoring the intensity of the (ArH+)-Ar-36 signal in long-term experiments with pyrolytic graphite-coated and uncoated tubes. The effect of release of water/hydrogen and carbon was significantly higher for the uncoated tubes. The source of the evolved hydrogen causing the (ArH+)-Ar-36 signal is supposed to be the graphite material of the tube. The influence of the effect on selected analyte ETV-ICP-MS signals (Al, V, Cu, Pb) is described in this study. (C) 1997 Elsevier Science B.V.