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Theoretical evaluation of error in the isotopic analysis of carbon and oxygen as CO 2 + : considerations for determining two different isotopic abundance ratios simultaneously
Author(s) -
Datta B. P.
Publication year - 2001
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.375
Subject(s) - natural abundance , chemistry , abundance (ecology) , isotopic ratio , carbon fibers , oxygen 18 , oxygen , analytical chemistry (journal) , isotopes of carbon , isotope , mass spectrometry , environmental chemistry , chromatography , total organic carbon , physics , mathematics , algorithm , organic chemistry , quantum mechanics , fishery , composite number , biology
The computations involved in the ${\bf CO_{2}^{+}}$ ion beam method of determining simultaneously a pair of constituent elemental isotopic abundance ratios P and Q (viz. 13 C/ 12 C and 17 O/ 16 O, or 13 C/ 12 C and 18 O/ 16 O, or 17 O/ 16 O and 18 O/ 16 O) are worked out, and the possible implications of their involvement as an analytical step are evaluated theoretically. It is shown, as an immediate consequence, that accurate measurements of the required isotopic ${\bf CO_{2}^{+}}$ abundance ratios (R j and R k ) do not necessarily mean that the results (P; Q) are equally accurate. It is demonstrated that, and also explained why, the results can be far more inaccurate, or even in some cases more accurate, than the (R j ;R k ) values themselves. It is clarified how the errors of analysis (δ P and δ Q ) are actually governed, and elaborated further by evaluating their variations as a function of different possible parameters which control their magnitudes. The investigations thus help to predict the required analytical conditions for accurate isotopic analysis of carbon and/or oxygen samples of any origin as ${\bf CO_{2}^{+}}$ . The considerations for the case of natural samples predict that, while it should be generally possible to simultaneously determine the isotopic abundance ratios of 13 C/ 12 C and 18 O/ 16 O with an accuracy better than the measurements themselves, the determination of either the ( 13 C/ 12 C and 17 O/ 16 O) ratios or the ( 17 O/ 16 O and 18 O/ 16 O) ratios, with an accuracy as good as that of the measurements, would be extremely difficult and may, in practice, be impossible. Copyright © 2001 John Wiley & Sons, Ltd.