On‐line triple oxygen isotope analysis of nitrous oxide using decomposition by microwave discharge

Abstract

A novel on-line analytical method was developed to measure the triple oxygen isotopes of N2O using microwave discharge to decompose N2O. This easy-to-use method is free from conditioning of reaction devices, and is applicable to molecules other than N2O such as NO and NO2.

Comparison of methods to determine triple oxygen isotope composition of N2O

“…3 and they show that the carry-over was not statistically significant for any of the reaction units, as has also been reported before for quartz microwave. [13] When running alternating sets of CS and STD-N 2 O at different amounts (starting with the smallest amounts), the results of the smallest samples (10 nmol N 2 O) of STD-N 2 O indicate that a carry-over from the preceding CS samples (with highest amounts) might have occurred because these samples show a distinct deviation from the quantity dependence of the other samples (Fig. 4).…”

“…At higher N 2 O amounts, however, the precision is very good. Mukotaka et al [13] reported comparable precision for the microwave quartz, but no data on Δ 17 O was available for the gold wire oven. [12] CONCLUSIONS Taken together, the data indicate that two processes are affecting the quality of the Δ 17 O data: (i) exchange of sample oxygen with oxygen present in the reaction unit, and (ii) mass-independent fractionation when O 2 and N 2 are present in the ion source at the same time (although this mass-independent fractionation should also be possible in the reaction unit, as N 2 and O 2 are formed there simultaneously).…”

“…1): (1) Microwave-induced plasma (MIP) with quartz tubing [13] The microwave discharge unit consists of a Beenakker cavity [18] (AHF Analysentechnik, Tübingen, Germany) and a quartz tube (i.d. 1 mm, o.d.…”

“…The advantage of this approach over the usual 18 O tracing lies in the possibility of the simultaneous investigation of isotopic fractionation processes affecting δ and O 2 use either a heated gold catalyst [11,12] or a microwaveinduced plasma (MIP). [13] The latter has also been used for measuring N 2 from denitrification tracer experiments where 15 N is distributed non-statistically among the N 2 molecules. [14][15][16] Here, we present a comparison of the gold wire oven [12] and the MIP [13] methods.…”

“…[13] The latter has also been used for measuring N 2 from denitrification tracer experiments where 15 N is distributed non-statistically among the N 2 molecules. [14][15][16] Here, we present a comparison of the gold wire oven [12] and the MIP [13] methods. In addition, the use of a corundum tube in the MIP reactor was tested to see if it produced better results than the quartz tube used in the original method.…”