14Ncontaining

14N-containing refers to chemical species that include nitrogen-14 as one or more of their nitrogen atoms. 14N is the most abundant nitrogen isotope, accounting for about 99.63% of natural nitrogen, while 15N makes up about 0.37%. In most contexts, "14N-containing" denotes the naturally occurring form unless otherwise specified.

Isotopic properties and analysis: In nuclear magnetic resonance, 14N has nuclear spin I=1 and is quadrupolar, which often yields broad, less informative signals compared with 15N (I=1/2) used for high-resolution 15N NMR. In mass spectrometry, substituting 14N with 15N in one or more nitrogens increases the molecular mass by one per substituted atom, producing distinct isotopologues that can be used to trace nitrogen sources and transformations.

Applications: 14N-containing compounds serve as the natural baseline in experiments that track nitrogen chemistry. Researchers often use 15N-labeled substrates to label nitrogen pathways and then monitor 15N incorporation; the unmodified molecule remains 14N-containing. In environmental and biological studies, distinguishing 14N- from 15N-containing species helps elucidate nitrogen cycling, metabolism, and provenance.

Examples: common 14N-containing molecules include ammonia (NH3), ammonium (NH4+), nitrates (NO3-), amino acids, nucleotides, and proteins; in natural samples these atoms are predominantly 14N. Any nitrogenous compound will be 14N-containing unless enriched with 15N.

See also: nitrogen isotopes, 15N, isotopic labeling.