Chemistry Reference
In-Depth Information
Such are the fi rst requirements for obtaining accu-
rate and representative analytical data to be consid-
ered by physicians, epidemiologists, and toxicologists.
This chapter does not intend to give in-depth detail
for every possible element in any feasible matrix. Such
information is given in the specifi c chapters, metal by
metal. Additional information can be found in publica-
tions in international journals and also in monographs
and topic chapters. Sample collection guidelines for
trace elements in blood and urine have been published
by IUPAC (Cornelis
et al.
, 1995). The article describes
harmonized guidelines for collection, preparation,
analysis, and quality control. The aim was to assist
scientists worldwide to produce comparable data to be
useful on a regional, national, and international scale.
The guidelines cover the elements Al, As, Cd, Cr, Co,
Cu, Pb, Li, Mn, Hg, Ni, Se, and Zn. Avoidance of con-
tamination is a major issue when determining the trace
elements in body fl uids and tissues (Versieck, 1985).
Informative chapters on sampling of clinical samples
for trace element speciation purposes can be read in
the
Handbook of Elemental Speciation
(De Cremer, 2003
and Muñoz Olivas and Cámara, 2003).
Many species are thermodynamically unstable. The
simple act of sampling and storing the species may
alter them. The information is then irreversibly lost.
8.2.1.1 Ambient Air
Metal concentrations in ambient air are generally
low, and intake through air is usually small in relation
to intake of food. Exceptions may occur in the vicinity
of plants emitting large amounts of metals (e.g., smelt-
ers) and in areas with heavy traffi c. In the past, the
intake of lead through inhalation exceeded that from
food as a result of the use of leaded automobile fuels.
Today, a new problem has occurred through the use
of automobile exhaust catalysts containing Pt, Pd, and
Rh (platinum group elements or PGE). Emission rates
are estimated to be in the ng/km
1
range. The forms
in which the PGEs are emitted are still unclear; how-
ever, a signifi cant soluble fraction has been measured
in automobile exhausts. Analysis of exhaust particles
revealed the occurrence of metallic Pt(0) attached onto
aluminium oxide together with a small amount of
Pt(IV) (Rauch and Morrison, 2005).
8.2.1.2 Industrial Air
Occupational exposure takes place mainly by inhala-
tion. Good sampling techniques and accurate analysis
are thus essential for evaluating the exposure in work-
places. Concentrations in industrial air are usually
much higher than in ambient air, which makes it easy
to collect suffi ciently large amounts for accurate meas-
urements. Personal samplers are the preferred method.
Special attention is needed concerning sampling tech-
niques and storage of airborne metal species in the
workplace (Dabek-Zlotorzynska and Keppel-Jones,
2003). The choice of the fi lter media plays a prepon-
derant role. General criteria that must be considered
in fi lter selection are: (1) representative sampling for
particulates of
8.2 Air, Water, and Food
8.2.1 Air
Metals exist in ambient or workplace air in both
vapor and particulate forms, depending on the specifi c
metal and chemical species. In the case of particulate-
borne metals, particle size distribution and chemical
properties such as solubility are important in deter-
mining the site of deposition in the respiratory tract
and the degree of absorption. These factors have been
addressed in a number of studies (Baron, 2003).
Environmental surveys using stationary samplers
did allow establishing the concentration of several met-
als in a number of cities and rural and remote locations
(Van Dingenen
et al.
, 2004). More relevant estimates
can be obtained by the use of personal samplers. The
use of such devices for the determination of workplace
exposures has become common practice (Schwela
et al.
,
2002; WHO, 1982). An interesting survey about sam-
pling systems can be found in Dabek-Zlotorzynska
and Keppel-Jones (2003). The choice of the fi lter sub-
strate is very important. Filters should be mechanically
and thermally stable and should not interact with the
deposit, even when subject to a strong extraction sol-
vent. The rule of thumb is that when no data are avail-
able from reliable studies by other research groups,
the effect of sampling and storage conditions on the
stability of the species in the matrix should be studied.
m, (2) low hygroscopicity, because
hygroscopicity exceeding 1 mg per piece leads to seri-
ous errors in weight concentration measurements and
hence to the improper estimate of the environmental
concentration, and (3) absence of impurities that might
interfere with the analysis. As an example of the latter,
glass fi ber or Tefl on fi lters were found to be unsuitable
for the sampling of airborne dust with low platinum
content (Alt
et al.
, 1993). Only polycarbonate and cellu-
lose gave blank values as low as 5 pg Pt per total fi lter.
The absence of interaction between species and fi l-
ter substrate is particularly relevant in the case of the
analysis of Cr(III)/(VI) in air particulate matter. Spini
et al.
(1994) have reported the reduction of Cr(VI) to
Cr(III) when cellulose fi lters were extracted with
an alkaline solution containing a known amount of
≥
0.3
µ
