ABSTRACT
N-Nitroso compounds (NOCs) were originally synthe-
sized about 100 years ago by reacting secondary
amines with nitrous acid. They were used by various
industries as solvents until their toxicity was discovered
in 1937. Freund (1) was the original discoverer of the
toxicity of NOCs in 1937 and reported that animals
such as mice and dogs exposed to N-nitrosodimethyl-
amine (NDMA) vapors develop liver necrosis. An
extensive investigation by Barnes and Magee (2) also
found that NDMA is acutely hepatotoxic. Two years
later, the same workers (3) showed that liver tumors
could be induced in rats by feeding them NDMA. This
research into the carcinogenicity of NOCs was pub-
lished in 1956 and triggered intense research into the
biological effects of NOCs. The suspicion that NOCs might be contained in
foods resulted from studies carried out in Norway
in the late 1950s. Ender et al. (4) found that liver
disorders in mink and several ruminants were related
to the feeding of nitrite-preserved herring meal. The
toxic component of the herring meal was then isolated
and identified as NDMA and it was suggested that
NDMA may result from the reaction of dimethylamine
(DMA) in fish meal with nitrous acid derived from the
sodium nitrite preservative (5). These seminal studies
prompted researchers to examine human foods for
the presence of NOCs. Since the middle of the 1960s,
many human foods have been analyzed and several
have been found to contain NOCs (6-9). From the
early 1970s, the literature concerning the analysis,
detection, and synthesis of NOCs expanded consider-
ably and resulted in the proceedings from meetings
that were held in 1971 and again in 1973 at the
International Agency for Research on Cancer (IARC). To detect NOCs in foods, methods involving the
precise gas chromatography (GC)–mass spectrometry
(MS) technique were developed by a large number of
investigators (10-14). Subsequently, a thermal-energy
analyzer (TEA) was found to be superior to other GC
detectors in detecting NOCs in foods, beverages, and
complex biological mixtures due to its high sensitivity
and selectivity. Currently, the most frequently used
method for detecting N-nitrosamines (NAs) is GC-
TEA and high-performance liquid chromatography
(HPLC)–TEA.
