Inductively coupled plasma isotope calibration

In isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) the spike, the unspiked and a spiked sample are measured by ICP-MS in order to determine the isotope ratio. Using this technique, more precise and accurate results can be obtained than by using a calibration graph or by standard addition. This is due to elimination of various systematic errors. Isotopes behave identically in most chemical and physical processes. Signal suppression and enhancement due to the matrix in ICP-MS affects both isotopes equally. The same holds for most long-term instrumental fluctuations and drift. Accuracy and precision obtained with ID-ICP-QMS are better than with other ICP-QMS calibration... 

Since the introduction of the first commercial instrument in 1983, inductively coupled plasma mass spectrometry (ICP-MS) has become widely accepted as a powerful technique for elemental analysis. Two excellent books on ICP-MS have been published [1,2]. ICP-MS provides rapid, multielement analysis with detection limits at single parts part trillion or below for about 40 to 60 elements in solution and a dynamic range of 104 to 108. These are the main reasons most ICP-MS instruments have been purchased. Two additional, unique capabilities of ICP-MS have also contributed to its commercial success elemental isotope ratio measurements and convenient semiquantitative analysis. The relative sensitivities from element to element are predictable enough that semiquantitative analysis (with accuracy within a factor of 2 to 5) for up to 80 elements can be obtained using a single calibration solution containing a few elements and a blank solution. 

Institute of Science and Technology has been described by Bowers et al [3]. A recent report describes using isotope dilution to calibrate analysis of solid samples using electrothermal vaporization with inductively coupled plasma mass spectrometry (ICP-MS) [4]. 

Whatever the analytical method and the determinand may be, the greatest care should be devoted to the proper selection and use of internal standards, careful preparation of blanks and adequate calibration to avoid serious mistakes. Today the Antarctic investigator has access to a multitude of analytical techniques, the scope, detection power and robustness of which were simply unthinkable only two decades ago. For chemical elements they encompass Atomic Absorption Spectrometry (AAS) [with Flame (F) and Electrothermal Atomization (ETA) and Hydride or Cold Vapor (HG or CV) generation]. Atomic Emission Spectrometry (AES) [with Inductively Coupled Plasma (ICP), Spark (S), Flame (F) and Glow Discharge/Hollow Cathode (HC/GD) emission sources], Atomic Fluorescence Spectrometry (AFS) [with HC/GD, Electrodeless Discharge (ED) and Laser Excitation (LE) sources and with the possibility of resorting to the important Isotope... 

M. Resano, I. Gelaude, R. Dams, and F. Vanhaecke. Solid sampling-electrothermal vaporiza-tion-inductively coupled plasma mass spectrometry for the direct determination of Hg in different materials using isotope dilution with a gaseous phase for calibration. Spectrochimica Acta Part B 60 319-326, 2005. 

Mestek, O., Koplik, R., Fingerova, H., and Suchanek, M. (2000). Determination of thallium in environmental samples by inductively coupled plasma mass spectrometry Comparison and validation of isotope dilution and external calibration methods.J.y4mi/./l(. Spectrom., 403-408. 

Reid,J. E., Horn, I., Longerich, H. R, Forsythe, L., and Jenner, G.A. (1999). Determination of Zr and Hf in a flux-free fusion of whole rock samples using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) with isotope dilution calibration. Geostand, Newsl. 23(2), 149. 

Vanhaecke, E, Boonen, S., Moens, L., and Dams, R. (1997). Isotope dilution as a calibration method for solid sampling electrothermal vaporization inductively coupled plasma mass spectrometry./. Ana/. At. Spectrom. 12(2), 125. 

Zhang, L.-S., and Combs, S. M. (1998). Double calibration (external calibration and stable isotope dilution) for determining selenium in plant tissue by hydride generation inductively coupled plasma mass spectrometry.J. Assoc. Off. Anal. Chem. Int. 81(5), 1060. 

Snell, J. R, Stewart, I. L, Sturgeon, R. E., and Freeh, W. (2000) Species specific isotope dilution calibration for determination of mercury species by gas chromatography coupled to inductively coupled plasma or furnace atomisation plasma ionisation-mass spectrometry. J. Aruil. At. Spectrom., 15,1540-5. 

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