Jan Kaiser, How accurate do we know 13C/12C, 18C/16O and 17O ...

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Recommended inter-laboratory comparability (1σ) 14 th WMO/IAEA Meeting of Experts on Carbon Dioxide Concentration and Related Tracers Measurement Techniques, 10-13 September 2007 in Helsinki, Finland CO 2 ±0.1 ppm (±0.05 ppm in southern hemisphere) 13 δ(CO 2 ) ±0.01 ‰ 18 δ(CO 2 ) ±0.05 ‰
How do we measure carbon and oxygen isotope ratios with mass spectrometers? Measure ion current ratios of sample relative to reference (NBS 19-CO 2 as stand-in for VPDB-CO 2 ) m/z 44 12 C 16 O + 2 m/z 45 13 C 16 O + 2 12 C 17 O 16 O + m/z 46 12 C 18 O 16 O + 13 C 17 O 16 O + 12 C 17 O + 2 45 δ I = 45 I/ I / 45 r 44 44 I I r −1 We assume that all minor isotopologues have the same relative ionisation efficiency. Then, the ion current delta is the same as the isotopologue delta. 45 45 δ I = δ = 45 R/ R / 45 r 44 44 R R r −1
Page 1: 8 September 2009 How accurately do
Page 5 and 6: "New" isobaric correction using δ
Page 7 and 8: C from δ measurements only MOW /V
Page 9 and 10: Influence of C on the computed 13
Page 11 and 12: Influence of the relative ionisatio
Page 13 and 14: VIM 3 rd edition (2008) reference q
Page 15 and 16: 13 R(VPDB-CO 2 ) 10 613 R Original
Page 25 and 26: Calculation of isotopologue mixing

Jan Kaiser, How accurate do we know 13C/12C, 18C/16O and 17O ...

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