Hello Everyone;
I wanted to know how IRMS can make a distinction between 32S18O16O and 34S16O2?
1) By Tunable Laser Spectroscopy of SO2
· Measurement of Sulfur Isotope Compositions by Tunable Laser Spectroscopy of SO2
Lance E. Christensen*, Benjamin Brunner†, Kasey N. Truong, Randall E. Mielke, Christopher R. Webster, and Max Coleman
Anal. Chem., 2007, 79 (24), pp 9261–9268
2) By IRMS :
The correction of isotopic measurements of sulfur and oxygen has proved problematic.
The correction method we have employed is approximate but represents the only approach for determining the isotopic sulfur and oxygen of SO2 .
For Oxygène :
L’oxygène qui possède trois isotopes stables (16O, 17O et 18O). En utilisant la notation δ :
δ17O = 1000*[(1 + δ18O/1000)0.512 - 1]
For Soufre :
Le soufre possédant 4 isotopes stables, deux formules peuvent être déduites. Les relations reliant les isotopes du soufre sont :
δ33S = 1000*[(1 + δ34S/1000)0.515 - 1]
δ36S = 1000*[(1 + δ34S/1000)1.91 - 1]
· Les fractionnements indépendants de la masse sont représentés par une nouvelle terminologie notée Δ :
For Oxygène :
Δ17O = δ17O -1000 * [(1 + δ18O /1000)0.512 - 1]
For Soufre :
∆33S = δ33S - 1000 * [(1 + δ34S / 1000)0.515 - 1]
∆36S = δ36S - 1000 * [(1 + δ34S / 1000)1.91 - 1]
Isotope Ratio Mass Spectrometry does not differentiate between 32S18O16O and 34S16O2 since both isotopologues share the same mass: mz/z 66.
Stan Halas has discussed the bias on d34S data from SO2 gas analysis in an IAEA publication from 1985 on "Studies on Sulphur Isotope Variations in Nature".
Contribution of 32S18O16O to 34S16O2 can only be corrected for by analysing a subsample of the same material a second time by the SF6 method.
Analysing 34S by SO2 and SF6 is discussed in: Rees, C.E. 1978, Geochim Cosmochim Acta, 42, 383-390
The question is not specific. W M-A's answer is true for the goal he states.
However, every phase change (gas, liquid, solid) or chemical reaction will fractionate the sulfur isotopes, measurable by mass spectrometry. To the extent various sulfur materials have different histories, isotopic measurements can distinguish them.
P.S. Isotopic fractionation is temperature dependent, increasing with lower temperatures. This effect is utilized in many fields.
Sorry Dr Bogard, you are not even wrong but you missed the point. The question was, can IRMS distinguish between two isotopologues of SO2 sharing the same mass 66. The question was not, can IRMS be used to measure subtle differences in 34S abundance that will tell us something about processes involving mass discrimination and, hence, isotopic fractionation. The answer to the latter is yes. The answer to the former is no, unless, as I have pointed out, one analyses subsamples of the same material twice; once by the SO2 method and once by the SF6 method.
Chapter I.4 f my text book “Stable Isotope Forensics” discusses general aspects of isotope effects, mass discrimination and isotopic fractionation. Chapter I.5 presents information how natural abundance of light elements stable isotopes (incl. 34S) varies as a result.
https://onlinelibrary.wiley.com/doi/book/10.1002/9781119080190
- Badges
- Science topic
- Similar topics
- Biological Science
- Anatomy
- Tissue