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dibenzodioxins (PCDDs) or polychlorinated biphenyls (PCBs). The former, often
produced as side products of some chemical synthesis reactions carried out at high
temperatures, have received wide attention particularly after the Seveso incident [1].
PCBs, before being banned, were used in many industrial products [2]. Persistence
properties and long-range transport phenomena led to worldwide distribution of
such compounds and culminated in their accumulation even in remote Arctic and
Antarctic environments [3, 4]. As a consequence, both compound classes have been
included in the Stockholm convention on persistent organic pollutants [5]. The
chemical complexity of samples containing PCDDs (75 congeners) and polychlorinated dibenzofurans (PCDFs, 135 congeners) in the presence of PCBs (209 congeners) requires high resolution analysis, which in the 1970s boosted the sales of
double-focusing sector field mass spectrometers, the only instruments capable of
resolving powers above 20,000 at that time [6, 7].
One major limitation in chemical analysis until the 1990s was that only volatile
or thermally stable target substances could be analyzed by mass spectrometry. This
is because the ionization method of choice then was electron ionization (EI) or
chemical ionization (CI), and sample introduction was usually performed through
gas chromatography (GC), with a temperature gradient up to 300 °C. This setup
limited the analytical window to mostly small and non-polar chemicals, typically
below 500 Da. Consequently, all larger, thermally labile, or polar chemicals, including many pharmaceuticals, personal care products and pesticides, could not be analyzed and no standard MS methods were available for their monitoring. Hence,
regulation was not possible at the time.
Only in the 1990s, with the advent of electrospray ionization (ESI) and matrixassisted laser desorption ionization (MALDI), polar and ionic target analytes also
became amenable to MS analysis. Additionally, the measured mass range could be
extended by orders of magnitude, because ESI easily produces multiply charged
molecules and mass spectrometers measure m/z. For instance bovine serum albumin, a protein of mass 66 kDa, could now be detected with a quadrupole MS having
a mass range of up to 2000 Da, provided it was carrying 100 protons, giving a signal
at m/z of 660. This new capacity provided by ESI made it possible to analyze biological macromolecules such as enzymes, allowing to investigate stress response
and evolutionary adaptation of organisms on the molecular level [8–10].
Figure 6.1 illustrates the fields of application of gas chromatography (GC)-MS
and liquid chromatography (LC)-MS in a biased personal representation. Of course,
derivatization allows the polar part to be partially addressed with GC-MS as well [11].
6.1.1 Analyzing the “Universe of Chemicals”
With improved sample preparation and increasing sensitivity, it has now become
possible to analyze very complex samples for emerging, potentially unknown, contaminants and their transformation products, present at very low concentrations.
This allows understanding patterns of low dose, chronic and pulse exposure, which
could be further linked with resulting toxicity and thus help explain the different
effects manifesting in the exposed organisms in each case.
K. J. Groh and M. J.-F. Suter
dibenzodioxins (PCDDs) or polychlorinated biphenyls (PCBs). The former, often
produced as side products of some chemical synthesis reactions carried out at high
temperatures, have received wide attention particularly after the Seveso incident [1].
PCBs, before being banned, were used in many industrial products [2]. Persistence
properties and long-range transport phenomena led to worldwide distribution of
such compounds and culminated in their accumulation even in remote Arctic and
Antarctic environments [3, 4]. As a consequence, both compound classes have been
included in the Stockholm convention on persistent organic pollutants [5]. The
chemical complexity of samples containing PCDDs (75 congeners) and polychlorinated dibenzofurans (PCDFs, 135 congeners) in the presence of PCBs (209 congeners) requires high resolution analysis, which in the 1970s boosted the sales of
double-focusing sector field mass spectrometers, the only instruments capable of
resolving powers above 20,000 at that time [6, 7].
One major limitation in chemical analysis until the 1990s was that only volatile
or thermally stable target substances could be analyzed by mass spectrometry. This
is because the ionization method of choice then was electron ionization (EI) or
chemical ionization (CI), and sample introduction was usually performed through
gas chromatography (GC), with a temperature gradient up to 300 °C. This setup
limited the analytical window to mostly small and non-polar chemicals, typically
below 500 Da. Consequently, all larger, thermally labile, or polar chemicals, including many pharmaceuticals, personal care products and pesticides, could not be analyzed and no standard MS methods were available for their monitoring. Hence,
regulation was not possible at the time.
Only in the 1990s, with the advent of electrospray ionization (ESI) and matrixassisted laser desorption ionization (MALDI), polar and ionic target analytes also
became amenable to MS analysis. Additionally, the measured mass range could be
extended by orders of magnitude, because ESI easily produces multiply charged
molecules and mass spectrometers measure m/z. For instance bovine serum albumin, a protein of mass 66 kDa, could now be detected with a quadrupole MS having
a mass range of up to 2000 Da, provided it was carrying 100 protons, giving a signal
at m/z of 660. This new capacity provided by ESI made it possible to analyze biological macromolecules such as enzymes, allowing to investigate stress response
and evolutionary adaptation of organisms on the molecular level [8–10].
Figure 6.1 illustrates the fields of application of gas chromatography (GC)-MS
and liquid chromatography (LC)-MS in a biased personal representation. Of course,
derivatization allows the polar part to be partially addressed with GC-MS as well [11].
6.1.1 Analyzing the “Universe of Chemicals”
With improved sample preparation and increasing sensitivity, it has now become
possible to analyze very complex samples for emerging, potentially unknown, contaminants and their transformation products, present at very low concentrations.
This allows understanding patterns of low dose, chronic and pulse exposure, which
could be further linked with resulting toxicity and thus help explain the different
effects manifesting in the exposed organisms in each case.
K. J. Groh and M. J.-F. Suter