Other Instrumental Methods in Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 320

Figure 12.8 Mass spectrum of 1,4-dichlorobenzene. Source: NIST Mass Spec Data Center,
S.E. Stein, director, ''Mass Spectra'' in NIST Chemistry WebBook, NIST Standard Reference Database
Number 69, Eds. P. J. Linstrom and W.G. Mallard, June 2005, National Institute of Standards and
Technology, Gaithersburg MD, 20899 (http://webbook.nist.gov)
less abundant, are also apparent in the mass spectrum. The ions at 111 and 113
correspond to the dissociation of one of the 35 Cl (more abundant) from the molecule
(146111 ¼ 35; 148113 ¼ 35). The ions at around m/z of 76 represent the
dissociations of the second Cl atom from the parent molecule. The mass spectrum of
1,4-dichlorobenzene shows a clear feature of isotopic cluster as a result of the
isotopic chlorines in the molecule. Note, however, that isotopic clusters will appear
in the mass spectra of all organic compounds. This is because both C and H, the two
most common elements of organic compounds, have their naturally occurring
isotopes ( 12 C: 13 C¼98.89%: 1.11%; 1 H: 2 H¼99.99%: 0.01%).
12.1.3 Mass Spectrometric Applications
in Environmental Analysis
Both atomic (ICP-MS) and molecular (GC-MS and LC-MS) mass spectrometric
methods have played a key role in environmental analysis. From the early discovery
of disinfection byproducts in drinking water using GC-MS in 1974, mass
spectrometry has become the prime tool in many environmental research and
regulatory laboratories in helping analysts to identify pollutants in an unequivocal
way, and advancing our understanding of the complex environmental processes. In
the early 1980s, mass spectrometry was considered to be expensive, complicated,
time-consuming, and personnel-intensive, but technology advancement has made
such instrument more affordable, user-friendly, and productive. Today there is
hardly a GC lab which is not equipped with a GC-MS system for organic analysis. In
a similar trend, ICP-MS has grown to become the technique of choice for rapid
ultratrace multielement analysis since its first commercialization in 1983.
ICP-MS Applications: ICP-MS can detect almost all elements in the periodic
table (few exceptions include C, H, O, N, F, Cl). ICP-MS further offers the analytical