Chemistry Reference
In-Depth Information
2 METHODS AND PROBLEMS OF
ANALYSIS
palladium. In the year 2003, they produced 64.8, 74.0,
11.0, and 14.6 tons, respectively. Production from other
countries was 7.0 tons, making the total 171.0 tons
(USGS, 2005a). Because the production of palladium
is relatively limited to a few production sites, supply
shortages can cause substantial fl uctuations in the
market price. In 2000 and early 2001, the price rose
and peaked at fi ve times the usual market prices (Pal-
ladium, Metal of the 21st Century, 2005).
Because it is very expensive, a high proportion of pal-
ladium, and other platinum group metals, is recycled
by either the users or the producers (e.g., catalysts) and
does not appear on the market. In 2003, an estimated
8 tons of palladium was available in the United States
for recycling from autocatalysts (USGS, 2005b).
Current measurement techniques do not allow the
separate chemical species of palladium to be differen-
tiated when more than one form is present. Almost all
measurements of palladium determine the total palla-
dium content.
A solution of palladium(II) nitrate at high concen-
tration (mg/L range) is frequently used as a chemi-
cal modifi er in graphite furnace atomic absorption
spectrometry (GF-AAS; Schlemmer and Welz, 1986;
Taylor
et al
., 1998). Therefore, to avoid contamination,
care must be taken in analytical laboratories that use
palladium as a chemical modifi er.
For biological materials, such as blood and urine,
atomic absorption spectrometry (AAS) and induc-
tively coupled plasma mass spectrometry (ICP-MS) are
often applied. By using quadrupole ICP-MS, Schramel
et al
. (1997) reported a detection limit of palladium of
0.03
3.2 Uses
Demand for palladium is high for its use in electrical
equipment, dental materials, and automobile catalysts.
Palladium metal and silver-palladium powder
pastes are important in the production of many elec-
tronic components. The pastes are used in active com-
ponents such as diodes, transistors, integrated circuits,
hybrid circuits, and semiconductor memories. They are
also used for passive electronic components, such as
small multilayer ceramic capacitors, and for thick fi lm
resistors and conductors. Palladium alloys are used in
electrical contacts, electrical relays, and switching sys-
tems in telecommunications devices. The gold in the
coatings of electronics, electrical connectors, and lead
frames of semiconductors can sometimes be replaced
with palladium (Kroschwitz, 1996).
Palladium is a component in some dental amalgams.
Palladium alloys (gold-silver-copper-palladium) can be
matched to any dental application such as inlays, full-
cast crowns, long-span bridges, ceramic metal systems,
and removable partial dentures (Stümke, 1992).
Catalysts are used to reduce levels of nitrogen oxides,
carbon monoxide, and hydrocarbons in automobile
exhausts. Recently developed catalysts use combina-
tions of precious metals, such as platinum, palladium,
and rhodium (Abthoff
et al
., 1994; Degussa, 1995; Kro-
schwitz, 1996). The concentrations of the precious met-
als in the catalysts vary depending on the specifi cations
of the manufacturer (IPCS, 1991). Worldwide demand
for palladium in automobile catalysts rose from 23.5
tons in 1993 to 139 tons in 1998. Approximately 60%
of European gasoline-powered cars sold in 1997 were
equipped with palladium-based catalysts; many
Japanese cars are also equipped with palladium sys-
tems, but platinum-rich technology remains dominant
elsewhere in Asia (Cowley, 1997). North American
carmakers continue to use platinum-rich catalysts,
g/L of urine after acidifi cation with nitric acid.
When using fl ameless AAS, decomposition with nitric
acid gives much lower detection limits: 0.003
µ
µ
g/L
of urine and 0.01
g/g of blood (Jones, 1976). More
recently, Begerow
et al
. (1997a,b) reported a limit of
0.2 ng/L for whole blood and urine on cleaning of
all materials (UV photolysis), resulting in a drastic
reduction of blanks, when using sector fi eld ICP-MS.
Applying high-performance liquid chromatography, a
detection limit of 10 ng/L for urine was reported after
UV photolysis (Philippeit and Angerer, 2001).
For particulate matter in ambient air, X-ray fl uores-
cence analysis has been performed at detection limits of
1 ng/m
3
(Lu
et al
., 1994) or 0.5 ng/m
3
(Gertler, 1994). For
analysis of water, AAS and ICP-MS are often applied,
with their limits of detection differing depending on
the pretreatment procedure used.
Palladium is rarely found in signifi cant concentrations
in environmental and biological materials. Materials
being investigated for very low levels of palladium must
be sampled in large amounts. Therefore, homogeniza-
tion, digestion, storage, and matrix effects become major
problems. For biological materials, destructive methods
are often required during the analytical procedures.
For example, samples may be ashed to destroy organic
materials and then treated with strong acids, causing
information about the palladium species to be lost.
µ
3 PRODUCTION AND USES
3.1. Production
The Republic of South Africa, Russia, Canada, and
the United States are the four primary producers of
