Open AccessMembrane inlet mass spectrometric analysis of N‐isotope labelling for aquatic denitrification studies
Author(s) -
Jensen Karen M.,
Jensen Mikael H.,
Cox Raymond P.
Publication year - 1996
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.1996.tb00309.x
Subject(s) - nitrate , denitrifying bacteria , denitrification , mass spectrometry , inlet , environmental chemistry , nitrite , stable isotope ratio , isotope , chromatography , isotope analysis , tracer , analytical chemistry (journal) , biology , nitrogen , chemistry , ecology , oceanography , physics , quantum mechanics , geology , organic chemistry , nuclear physics
Techniques are described for measuring the isotope distribution in dissolved nitrate and N 2 using membrane inlet mass spectrometry, which allows several gases to be measured in a water sample without the need for any separation steps. The isotope distribution in dissolved nitrate was measured using denitrifying Pseudomonas nautica to reduce the nitrate to N 2 which was then measured by mass spectrometry. Pseudomonas nautica NCIMB 1967 was easily grown in nitrate‐limited continuous culture minimising intra‐ or extracellular nitrate or nitrite pools, and the bioassay was tolerant of a range of salinities. The precision of the bioassay when measuring samples with high 15 NO 3 − contents (0.5 μmol) was 0.05 atom%; with 0.1 μmol 15 NO 3 − , the precision was around 0.2 atom%. Differences in labelling of N 2 in preserved samples obtained from 15 NO 3 − incubations of water‐covered sediment cores were measured on parallel samples with membrane inlet MS and GC‐MS. The membrane inlet technique was accurate but the precision on ratio measurements was lower than by GC‐MS.