Chemistry Reference
In-Depth Information
Platinum is unaffected by air at any temperature.
It reacts with boiling
aqua regia
with formation of chlo-
roplatinic acid and with molten alkali cyanides. Halo-
gens, cyanides, sulfur, molten sulfur compounds, and
hydroxides can affect platinum.
The most important platinum compounds are those
with halogens. The binary compounds are chlorides
(+2 and +4), the oxide, and also the sulfate and nitrate.
Tetravalent platinum compounds are readily soluble in
water except platinic oxide, which is soluble in dilute
phosphoric acid, other concentrated acids, and easily
soluble in dilute potassium hydroxide solutions. Diva-
lent platinous chloride is insoluble in water, alcohol,
and ether but soluble in hydrochloric acid. Platinum
compounds are considered to be soluble in human
body if they are soluble to 0.07 mol/L hydrochloric
acid (HSE, 1996). Coordination complex compounds,
hexachloroplatinic and tetrachloroplatinic acids, and
their alkali salts, dominate in aqueous solutions.
Certain platinum coordination complexes with dif-
ferent ligands (cisplatin, carboplatin, oxaliplatin, loba-
platin, satraplatin) are used in cancer chemotherapy.
Of the two stereoisomers of diammonium chloropla-
tinate (
cis
- and
trans
-diamminedichloroplatinum (II)),
only
cis
-form is effective as chemotherapeutic.
obtained with both methods, but voltammetry was
20 times more sensitive than ICP-MS (Renner
et al
.,
2002; Zimmermann
et al
., 2001) and approximately
6000 times more sensitive than the standard fl ameless
atomic absorption spectrophotometry (AAS) method
(Gelevert
et al
., 2001) The lowest platinum concentra-
tions measured in tissue samples were approximately
200 ng/kg analyzed with SF-ICP-MS (sector fi eld). Also
X-rays have been exploited in tissue analysis (Taylor
et al
., 2002). After UV irradiation of urine samples,
platinum was determined by use of SF-ICP-MS on the
level 1000 pg/L with the absolute detection of 30 pg/L
(Caroli
et al
., 2001). An ultrasonic nebulizer connected
with SF-ICP-MS has been used for plasma and whole
blood samples (Morrison
et al
., 2000). For accurate
determination of platinum by ICP-MS correction by
use of interference equations is needed to prevent the
molecular ion and doubly charged ion interferences
induced by CuAr
+
, HfO
+
, SrO
+
, YO
+
and Pb
2
+
.
Because the need of detection is at nanogram level,
preconcentration methods are required in many cases.
With improved analytical methods, part of the con-
centrations presented earlier in literature has been
shown to be in error. There is a lack of useful control
materials at required concentration levels and matri-
ces; international quality assurance schemes are badly
needed.
2
METHODS AND PROBLEMS
OF ANALYSIS
3
PRODUCTION AND USES
Several methods are available to determine platinum
from biological materials. Earlier mainly electrother-
mal atomic absorption and adsorptive voltammet-
ric methods were used; their detection limits are low
enough for the studies of the body fl uids of patients
who were treated with drugs, but for environmental
exposure more reliable methods are needed. Inductive
coupled plasma with atomic emission spectrometry
or with mass detector (ICP-MS), neutron activation
analysis, and modern adsorptive voltammetry are
sensitive enough and widely used techniques for the
determination of platinum at nanogram and sub-
nanogram levels in a wide variety of biological and
environmental matrices. The most sensitive method is
adsorptive voltammetry with a limit of quantifi cation
of few picograms per gram levels.
The limit of quantization 50pg/L for urine, 10pg/L
for plasma, and 5 pg/L for plasma were recently
reported for electrothermal atomic absorption meth-
ods (Vouillamoz-Lorenz
et al
., 2001). In a comparison
of sector fi eld ICP-MS (SF-ICP-MS) with adsorptive
cathodic stripping voltammetry at ultratrace levels of
platinum in biological samples identical results were
3.1
Production
Platinum is found mainly in sulfi de and arsenide
minerals as sperrylite PtAs
2
, cooperite (Pt,Pd)S, and
braggite (Pt,Pd,Ni)S; it usually occurs together with
other platinum-groups metals (PGM). The main
deposits are in the Republic of South Africa, Russia,
Canada, and the United States. The world produc-
tion of platinum-group metals in 2000 was 365 tons
(Kelly and Hilliar, 2003). Demand for platinum in
2003 was 185 tons and is steadily increasing (Matthey,
2004b). In 2004, the demand was 223 tons, of which
approximately 20 tons was recovered from recycling
(Matthey, 2004a).
Sulfi te and arsenide ores are fi rst smelted to pro-
duce a matte of metal sulfi de mixture. The other metals
are precipitated from the mixture. Selenium, tellurium,
and sulfi de are removed from the concentrate of pre-
cious metals. Silver and gold are separated electro-
lytically, with liquid extraction or precipitation from
the chlorinated solution. The platinum-group metals
are precipitated and refi ned with different techniques
(Renner
et al
., 2002).
