Nitrogen isotopic measurement

Figure 5. Nitrogen isotope measurements on various components of the natural environment. The 15N values expressed with respect to AIR. (z) Data from Ref. 52 (b) data from Ref. 53 and (c) data from Ref. 31.

Nitrogen in the Archaean mantle The initial nitrogen isotopic composition of the Earth is not well known. However, nitrogen isotope measurements on 2.9-3.3 Ga diamonds from the subcontinental lithosphere have a mean S15N value of -5, and a similar C/N ratio to that of the modern mantle (Fig. 5.4), suggesting that there has been very little change since about 3.0 Ga (Marty Dauphas, 2003). 

Bohlke,J. K., C. J. Gwinn T. B. Coplen, 1993. New reference materials for nitrogen-isotope measurements. Geostandards Newsletter 17 159-164. 

Important additional evidence for aryl cations as intermediates comes from primary nitrogen and secondary deuterium isotope effects, investigated by Loudon et al. (1973) and by Swain et al. (1975 b, 1975 c). The kinetic isotope effect kH/ki5 measured in the dediazoniation of C6H515N = N in 1% aqueous H2S04 at 25 °C is 1.038, close to the calculated value (1.040-1.045) expected for complete C-N bond cleavage in the transition state. It should be mentioned, however, that a partial or almost complete cleavage of the C — N bond, and therefore a nitrogen isotope effect, is also to be expected for an ANDN-like mechanism, but not for an AN + DN mechanism. 

Schurr, M.R. 1997 Stable nitrogen isotopes as evidence for the age of weaning at the Angel Site A comparison of isotopic and demographic measures of weaning age. Journal of Archaeological Science 24 919-927. 

The 8 C values of the Preclassic humans at Cuello (Table 2.1) average -12.9 0.9%o (n = 28) in collagen, -9.8 1.0 in bone apatite (n = 16), and -8.7 2.3%o in tooth enamel apatite (n = 33) the S N values in collagen average 8.9 1.0%o (n = 23). The discrepancy in the number of specimens is due to the fact that more teeth were available than post-cranial material, while some of the specimens contained insufficient collagen to measure the nitrogen isotope ratios. Additional bone apatite analyses are in progress. 

Table 9.4. C N molar ratios (calculated and measured), total C and N content and stable carbon and nitrogen isotope data from bacteria, their growth medium (nutrient broth), and from collagen (infected and non-infected marten bone). The bacteria for inoculation were raised on nutrient broth (nb), with/without additives.

Higginson et, have used vinyl monomers to capture the radical intermediate, which turned out to be NH2 when Ti(III) was employed as reductant. Brown and Drury measured the nitrogen isotope elfect for the reduction of several... 

Oxygen isotopes, sometimes combined with carbon, nitrogen, strontium, and lead isotopic measurements, have been used to study the mobility of diverse human groups such as in Teotihuacan and Oaxaca, Mexico, dating from about 300 bc to ad 750 (Stuart-Williams et al. 1996), the Kellis 2 cemetery (c. ad 250) in the Dakhleh Oasis, Egypt (Dupras and Schwarcz 2001), and in Britain (Budd et al. 2003). 

The 2,2 -hydrazonaphthalene doubly labelled with nitrogen-15 for the nitrogen isotope effect experiments and the [l,l -13C2]-2,2 -hydrazonaphthalene required for measuring the carbon isotope effect were synthesized by the reaction sequence shown in Schemes 18 and 19. 

---