Isotope-ratio-monitoring gas chromatography methods for high-precision isotopic analysis of nanomole quantities of silicate nitrogen

Nitrogen concentration and δ15N of altered oceanic crust obtained on ODP Legs 129 and 185: Insights into alteration-related nitrogen enrichment and the nitrogen subduction budget

“…Thus, large sample sizes (500-1000 mg) were used for samples containing only 1-2 ppm N in order to maintain high precision for all analyses. Total system blanks depend largely on the amounts of reagent used, but the blanks are uniform in size and isotopic composition for certain amount of reagent, allowing accurate corrections to be performed on data for unknowns (Bebout et al, , 2007. For example, in a 2-month period, 29 analyses of the system blank using 1 g Cu x O x reagent indicate an average blank size of 3.8 ± 0.2 nmol N 2 , with d 15 N of À7.3 ± 0.4&.…”

“…In this study, we employed sealed-tube, carrier-gas methods developed in our laboratory for analyses of low-N silicate materials (methods described in Bebout et al, 2004Bebout et al, , 2007. For most of the AOC samples, 50-350 mg powder (depending on the N content) was loaded with Cu x O x reagent into quartz tube (outer diameter: 6 mm; inner diameter: 4 mm) and pumped for 48 h while heated to temperatures of $100°C.…”

“…In this study, we employed sealed-tube, carrier-gas methods recently developed in our laboratory (Bebout et al, 2007) to investigate the N concentrations and isotopic compositions of AOC from the Pacific, Atlantic and Antarctic ocean basins recovered by DSDP/ODP drillings. We first present the results of a detailed study of AOC in the IBM margin (39 samples, including composites, from the sections drilled during Legs 129 and 185, at Sites 801 and 1149), with the goals of better defining the N input flux into the IBM convergent margin and identifying sources and mechanisms of N enrichment during seafloor alteration.…”

Isotope Fractionation Processes of Selected Elements

“…For these samples, static mass spectrometry, in which the gas is left under static conditions in the ion source, a method developed for noble gas analysis and adopted for nitrogen, has been used. As an alternative, Bebout et al (2007) described a continuous flow technique for nanomole quantities of nitrogen.…”

Nitrogen recycling in subducted oceanic lithosphere: The record in high- and ultrahigh-pressure metabasaltic rocks

“…scribed by Bebout et al (2007) and Li et al (2007) involving transfer of extracted N (as N 2 ) into a Finnigan MAT 252 mass spectrometer using a Finnigan Gas Bench II and a U-trap interface in which small samples of N 2 are entrained in a He stream. About 100-250 mg of sample powder (grain size <10 lm) were used and tests with analyses of finegrained powders, involving varying evacuation times and heating regimens for the quartz tubes before sealing, indicate that atmospheric contamination is minimal.…”