Isotope-ratio analysis for nitrogen15 in solid-phase samples such as plant tissue starts with transformation to gas phase by extremely rapid and complete flash combustion of the sample material. Ionized combustion product (dinitrogen) is mass-analyzed by means of differing mass/charge ratios among the various isotopic species of N2. More details of the process are in the Process Overview.
Sample prep considerations
Plant samples must be oven-dried, ball-milled to less than 250 um particle size and weighed (~3 mg, with ug digits significant) into 5 x 5 mm tin capsules before combustion. Poor precision can often be traced to inadequate grinding that leaves fibrous matter or visible granules in the sample. Sample prep for plant 15N analysis is here. Clients may send us unprocessed samples (e.g. leaves, stems, roots) or may provide any of the above processing themselves at a major reduction in price.