Lead - Toxicology of Metals - page 587

laboratories during the 1960s and 1970s. It does not
reach as low detection limits as ETAAS, but fairly sim-
ple FAAS methods exist, based on complexation of lead
followed by extraction into an organic phase, that allow
detection limits of 10

2.2.2 Air, Water, Soil, and Sediments

Inorganic lead in air of normal temperatures is
present as particles. In work environments, standard
hygienic methods are used with collection of air parti-
cles on fi lter, usually followed by wet ashing. Several
different analytical techniques are available for the
quantifi cation of lead on fi lter, such as ASV, ETAAS,
ICP-MS, and FAAS, but other methods are also
available (US ATSDR, 1999).
Water may be analyzed for dissolved or particulate
lead. Different extraction or preconcentration methods
may be used for dissolved lead to increase the concen-
tration before analysis. Particulate lead may be col-
lected on a fi lter and is then usually wet ashed. Also,
samples of dusts, sediments, and soils are usually wet
ashed before analysis.

g/L in urine
(Schütz and Skerfving, 1976). Considering the simplic-
ity and worldwide availability of FAAS instruments,
these methods may be of value in lead exposure inves-
tigations in regions where costs limit the availability of
newer instruments with higher performance. Further
back in history lie insensitive colorimetric methods,
which require even simpler instrumentation.
Regardless of the analytical method used, the issues
of contamination and calibration are crucial for success
in the determination of lead, especially at low levels, as
found in most biological samples. Contamination always
occurs in all steps from sampling to determination. The
question is not whether contamination occurs, but how
large it is and how much it varies between samples.
Plastic materials are often preferred in containers for
samples and chemicals. Chemicals, as well as compo-
nents of the analytical instrumentation, such as tubing
and pumps, may need to be checked for any lead contam-
ination. Also, the atmosphere can be a signifi cant source
of contamination, with lead-containing dust particles
contaminating samples. This problem may be overcome
by special fi ltering systems for the air in the laboratory
or workbenches or minimizing the time samples are
exposed to open air. To prepare and analyze samples
in duplicate or triplicate is a good way of assuring that
occasional contaminations do not pass unnoticed.
For some methods, it has become evident that cal-
ibration needs to be made in the same matrix as the
samples. Thus, when determining lead in human
blood, it may be necessary to calibrate the method by
using the method of standard addition or calibration
with spiked human blood samples.
Internal quality control (QC) within the laboratory
by inclusion of QC samples in each analytical run is
essential. Intercalibration between laboratories by use
of external QC samples is widespread in lead deter-
mination, and there are several national and interna-
tional intercalibration programs for lead in blood, for
example, from United Kingdom National External
Quality Assessment Service, UKNEQAS; Centre de
Toxicologie du Quebec, CTQ; and the German External
Quality Assessment Scheme, G-EQUAS. Also, accredi-
tation systems and/or approval of laboratories by
governmental bodies are available in several coun-
tries. Finally, reference blood samples with different
lead levels are commercially available (e.g., from the
International Atomic Energy Agency, IAEA; National
Institute of Standards and Technology, NIST, US; and
the commercial company Sero, Norway).

µ g/L in blood and 3 µ

2.2.3 Specialized Techniques

In addition to the analyses mentioned previously,
there are numerous other analytical techniques avail-
able for the determination of lead in different matrices.
Some examples will be mentioned in the following,
especially techniques that cannot be regarded as rou-
tine, but have provided (and may also in the future
provide) new insights in lead toxicology.
XRF may be used for determination of lead in a vari-
ety of matrices. Because of its nondestructive character,
one of its uses is for noninvasive measurements of the
lead concentration in bone in vivo (Ahlgren et al ., 1976;
Somervaille et al ., 1985).
The mass spectrometric techniques, mainly ICP-MS
and thermal ionization mass spectrometry (TIMS) but
also others, make it possible to determine the abun-
dance of the different lead isotopes. As mentioned
previously (Section 2.1), the ratio between the differ-
ent lead isotopes depends on the geological source of
the lead. These differences in isotopic profi les can be
used to evaluate the contribution to lead in blood from
different sources or “fi ngerprinting” the lead (Gulson
et al ., 2003; Naeher et al ., 2003).
With its low detection limits, ICP-MS has also
recently made it possible to determine lead in blood
plasma, serum (Schütz et al ., 1996), and seminal plasma
(Apostoli et al ., 1997), for example. The lead concentra-
tion in these matrices are usually so low that they were
previously very diffi cult to determine. Saliva (Koh
et al ., 2003) and sweat (Omokhodion and Crockford,
1991) from occupationally exposed workers have been
analyzed for lead by ETAAS, and analyses of urine and
hair have been carried out with different techniques,
such as ETAAS, ICP-MS, or ASV.
There are also techniques for speciation analysis
of lead (i.e., identifying or measuring the quantities