A commercial system for automated nitrogen isotope-ratio analysis by the Rittenberg technique

Abstract

A sequential sample treatment system is described that permits use of an isotope-ratio mass spectrometer for automated Rittenberg analyses of ammonium salts. This system is based on the design of McInteer and Montoya [Recent Developments in Mass Spectrometry in Biochemistry, Medicine and Environmental Research, edited by A. Frigerio (Elsevier, Amsterdam, 1981), Vol. 7, p. 343]. An x-y table and a set of valves under computer control are used to automatically perform hypobromite oxidations, introduce the N2 thus liberated to the mass spectrometer for isotope-ratio analysis, and effect spent sample pumpaway. Analyses can be performed on samples containing 20 μg of N. When operated with a Nuclide Model 3-60-RMS double-collector mass spectrometer, the standard deviation for measurements at the natural abundance level (12 samples, 50 or 100 μg of N per sample) ranged from 0.0002 to 0.000 06 at. % 15N. Throughput capacity is 100–250 samples per day, and unattended operation can continue for at least three days.

Evaluating the effects of gross nitrogen mineralization, immobilization, and nitrification on nitrogen fertilizer availability in soil experimentally contaminated with diesel

“…Soil extracts were spiked with 5 ml NH 4 NO 3 standard (30 lg N ml )1 ) before distillation to meet the 50-200 lg nitrogen requirement of the mass spectrometer. Distillates were dried at low temperatures (50-60 o C) to a NH 4 -salt, residual liquid H 2 SO 4 immobilized by adding 2 M KCl to each well in the microplate, and nitrogen isotope ratio analyses were performed using a Nuclide Model 3-60 RMS mass spectrometer equipped with an automated Rittenberg apparatus (ARA-MS, University of Illinois at U-C) (Mulvaney et al 1990). …”

Injection of porcine growth hormone releasing hormone gene plasmid in skeletal muscle increases piglets' growth and whole body protein turnover

“…The 15 N-enrichment of the total nitrogen in the urine was determined by emission spectrometry (Finnigan MAT-251). The procedure was the same with the method used by Mulvaney et al (1990) except that NaOBr was used instead of LiOBr to oxidize NH 4 + -N to N 2 . Urinary and fecal nitrogen excretion as well as nitrogen intake were based on each metabolic crate originally and then averaged to a base of each piglet for calculation of nitrogen balance and protein turnover.…”

Nitrogen preferences and plant-soil feedbacks as influenced by neighbors in the alpine tundra

“…We calculated microbial N as the CHCL 3 -labile N minus extractable TN, divided by a factor of 0.54 to correct for chloroform-labile N extraction efficiency (Brookes et al 1985;Jenkinson et al 2004). To measure the recovery of 15 N, we diffused the inorganic N, total N, CHCL 3 -N soil extracts for 5 days onto acidified disks (Brooks et al 1989), which were analyzed using an automated Rittenberg apparatus-mass spectrometer (Mulvaney et al 1990) at the 15 N Analysis Service of the University of Illinois (Champaign-Urbana, IL).…”