Technical Support Note-000
High Sensitivity Analysis of Nitrosamines
Using GC-MS/MS
Alex Chen
1
, Hans-Joachim Huebschmann
2
, Li Fangyan
3
, Chew Yai Foong
3
and Chan Sheot Harn
3
1
Alpha Analytical Pte. Ltd., Singapore;
2
Thermo Fisher Scientific, Singapore,
3
Health Sciences
Authority, HSA Singapore
Introduction
Nitrosamines is the common term used for compounds
of the class of N-nitrosodialkylamines. A large variety of
compounds are known and described with different alkyl
moieties
[1]
. The simplest N-nitrosodialkylamine with two
methyl groups is the N-nitrosodimethylamine (NDMA).
Nitrosamines are in common highly toxic compounds
with high cancerogenity for humans and animals, in
higher doses leading to severe liver damage with internal
bleeding
[2,3]
.
Nitrosamines in food are mainly produced from nitrites.
Nitrites are added to food as preservatives in meat and
meat products preventing the Botulinus poisoning.
Antioxidant food additives like vitamin C can prevent the
formation of nitrosamines from nitrites
[4]
. Another source
of nitrosamines is described by the reaction of nitrogen
oxides with alkaloids as it is reported from the drying
process of the germinated malt in beer production
[5]
. As
nitrosamine levels in malt and beer have been significantly
reduced in the brewing process, high analytical
performance is required. In addition to the regular control
of other food products for daily consumption, malt in
beer is also monitored for low levels of nitrosamines.
The “classical” nitrosamine analysis was performed for
many years by gas chromatography using a thermal
energy analyzer (TEA) as detector. This special TEA
detector was used due to its selectivity for nitrosamines
with to the specific chemilumniscent reaction of ozone
with the detector generated NO from nitrosamines. Today,
with increased sensitivity requirements, the detection
limits of the TEA, and also its complex operation, no
longer comply with the required needs for low detection
limits and sample throughput. Mass spectrometric
methods have increasingly replaced the TEA.
The EPA method 521 by Munch and Bassett from 2004
provided at that time a suitable GC-MS method based
on chemical ionization (CI) using an ion trap mass
spectrometer with internal ionization
[6, 7]
, in contrast
to standard quadrupole or ion trap mass spectrometers
using a dedicated (external) ion source design. Current
developments in GC-MS triple quadrupole technology
deliver today very high sensitivity and selectivity also in
the small molecule mass range and allow the detection
of nitrosamines at very low concentration levels even in
complex matrix samples. This is made possible by using
a much simpler and standard approach with the regular
electron impact ionization (EI) for a very straightforward
method for low level nitrosamine analysis.
This application note describes a turn-key GC-MS/MS
method for routine detection and quantitation of food
borne nitrosamine compounds. The food matrix in this
work has been different malt beer products and as a
final food product the commercial beer. Special focus
in the method development has been made to provide
the required high sensitivity for the detection of the
nitrosamine compounds for a fast, easy to implement
routine method.
The sample preparation is adapted and slightly modified
from AOAC Official Method (2000), 982.11
[8]
. An SPE
column extraction method using a celite column and
elution with DCM to isolate the nitrosamines from the
beer samples was developed.
Keywords:
Nitrosamines, Food Safety, beer, TSQ 8000, GC-MS/MS,
quantitation, confirmation, AutoSRM, TraceFinder
Application No e 10315
