Chemistry Reference
In-Depth Information
CHAPTER
2
General Chemistry, Sampling, Analytical
Methods, and Speciation
*
RITA CORNELIS AND MONICA NORDBERG
ABSTRACT
instrumental in understanding metal toxicology and
related adverse health effects.
The commonly used term “heavy metals” to
describe metals or metalloids that can give rise to
toxicity was brought to the attention of the partici-
pants of workshops held by the Scientifi c Committee
on Toxicology of Metals (SCTM) under the Interna-
tional Commission on Occupational Health (ICOH) in
the 1970s. It was concluded by the Task Groups that
the term should not be used (Task Group on Metal
Accumulation, 1973; Nordberg, 1976). Recently, the
improper use of the term “heavy metals” to design
a group of metals and semimetals (metalloids) asso-
ciated with contamination and potential toxicity or
ecotoxicity was brought to further attention, and the
misuse of the term was critically commented upon
(Duffus, 2002). Nevertheless, the term continues to be
commonly (mis)used in toxicology and legislation to
encompass the pure metal and all its chemical species.
This meaningless terminology totally ignores the fact
that pure metals and their compounds do not have the
same physiochemical, biological, and toxicological
properties. It is obvious that metal species need to be
addressed in each case.
Considering the persistence of the misuse of the
term “heavy metals,” it is interesting to learn some-
thing more about the origin of the term. An excellent
historic overview of the terminology “heavy metals”
has been published by J. Duffus (2002), to which the
reader is referred to fi nd the historic references. A
brief summary might be helpful to illustrate the con-
fusion that surrounds the term and avoid its further
This chapter provides an introduction to the general
chemistry of metals with particular emphasis on the
biological and toxicological characteristics. This is fol-
lowed by an elaborate description of analytical chem-
istry aspects relevant to trace element analysis. Be-
cause total element analysis is giving way to elemental
speciation and fractionation, detailed information is
given about useful strategies in sampling and sample
preparation, followed by separation techniques and de-
tection methods for the elemental species. In addition,
the major issues of calibration, reference materials, and
quality assurance are dealt with.
Of 111 identifi ed elements—90 occurring naturally
on earth—most (67) form metals, and all but one of
these (Hg) are solid. Eleven elements make up atomic
or molecular gases, and 12 more elements form solid or
liquid nonmetals. The chemistry of metals represents a
major part of inorganic chemistry. Understanding the
toxicology of metal species has advanced substantially
during the past decades, thanks to the considerable con-
tributions of bioinorganic chemistry (e.g., the discovery
that metal species undergo biomethylation and thus
can form organometallic compounds). This discipline
goes hand in hand with chemical speciation, which is
