2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P50 DETERMINATION OF uRANIuM by ICP-
AES IN ThE AbSENCE AND PRESENCE OF
PRECONCENTRATION ON MACROPOROuS
SORbENTS
MARTIn MOOS, KRISTýnA URBánKOVá and LUMíR
SOMMER
Brno University of Technology,Chemistry and Technology of
Environmental Protection, Purkyňova 118, 612 00 Brno,
xcmoos@fch.vutbr.cz
Introduction
Determination of uranium at very low concentrations
often needs preconcentration in order to meet the detection
limit of a given analytical method. Matrix interferences are
another problem when using AAS and ICP-AES. The preconcentration
by solid phase extraction is simple, rapid and usually
help to eliminate interferences from the matrix elements.
Several sorbents were used for preconcentration and separation
of trace uranium (VI) 1 , among them the macroporous
Amberlite XAD resins 2,3 , silica 4,5 , active carbon 6 and polyurethane
foam 7 which can be loaded with completing reagents.
The modified Amberlite XAD 4 resin in various particle size
was studied for the sorption of uranium in this paper prior to
the final determination by ICP-AES 1–3 .
Experimental
C h e m i c a l s
All chemicals used were of analytical grade quality.
1 g dm –3 standard solution of uranium (VI) Astasol
(Analytika, Praha, Czech Republic)
0.5 g dm –3 solution of 4-(2-pyridylazo)resorcinol (PAR)
from, Lachema, Brno, Czech Republic, the ammonium salt
of pyrrollidincarbodithioate (APDC) from, Lachema, Brno,
Czech Republic, 8-hydroxyquinoline-5-sulphonic acid (8-
HQS) from Aldrich, Steinheim, Germany and 1,2-dihydroxybenzene
(PYR) from Lachema, Brno, Czech Republic in
distilled water were stock solutions.
Cationic surfactants 1-ethoxycarbonylpentadecyl-trimethylammonium
bromide (Septonex ® ) from Tamda, Oloumouc,
Czech Republic, benzyldimethyltetradecyl-ammonium
chloride (Zephyramin ® ) from Merck, Darmstadt, Germany
and benzyldimethyldodecyl-ammonium bromide (Ajatin®)
from Fluka, Buchs, Switzerland were in 0.1 mol dm –3
aqueous solutions.
The macropourous sorbent Amberlite ® XAD 4 (Fluka,
Buchs, Switzerland) was previously dried 24 h at 100 °C,
milled and sieved; the fraction 0.32–0.63 µm was used and
ctivated in methanol for 24 hours. 200 mg of activated sorbent
was filled into empty cartridges. The columns were finally
washed by 10 ml of acetone and 10 ml of distilled water.
Solutions for the sorption or the eluent were aspirated
through the sorbent-filled plastic cartridges using the vacuum
pump operated vacuum suction device Dorcus (Tessek,
Praha, Czech Republic). A peristaltic pump UnIPAM 315
(Scientific instrument, Warszawa, Poland) was attached with
s432
3 mm wide silicon tubing to the cartridges and operated at a
solution flow rate of 1 ml min –1 .
I n s t r u m e n t
An echelle-based ICP-spectrometer with a prism predisperser
IRIS AP (Thermo Jarell Ash, U.S.A.) containing
a CID detector with 512 × 512 pixels for 195–900 nm, axial
plasma discharge and echelle grating with 54.4 lines mm –1
was used. The plasma source was a generator with 27.12 MHz
with the power output of 1.35 kW. The plasma argon flow rate
was 12 dm 3 min –1 . The integration time was 30 s. The results
were the average of 3 measurements. Spectral lines (nm) in
high orders: U 385.958 and U 409.014 nm were tested for
the determination and the spectral line 385.958 was used for
future measurement.
C a l i b r a t i o n P l o t s a n d L i m i t s o f
D e t e c t i o n
All linear calibration plots were evaluated according to
the ČSn ISO 8466-1 standard including the variation range
homogeneity test and linearity test 8 . The confidence limits of
the plot are also expressed.
The recovery was calculated by the expression
c(
U )
R =
eluted ⋅
c(
U ) applied onto the column
where f is the enrichment factor.
The detection limit was expressed according to Graham
9 , Miller 10 from the calibration plots and to IUPAC 11
from 10 points of the blank.
Results
D e t e r m i n a t i o n o f U r a n i u m b y
I C P - A E S i n t h e A b s e n c e o f
P r e c o n c e n t r a t i o n
Some determination in geological samples was earlier
described 12 . A 10% signal decrease was observed for
0.75 mol dm –3 HnO 3 , but for 1 mol dm –3 HCl the decrease
reaches 20 %. In the presence of various 3 × 10 –3 mol dm –3
surfactants, Brij 35, Zephyramine, Ajatin and dodecylsuphate
the 5–15 % increase of the calibration slope was observed.
Similarly, the slope of calibration plots increased by 5 % in
the presence of 6 × 10 –5 mol dm –3 PAR, 9 × 10 –5 mol dm –3
APDC or 2.2 × 10 –5 mol dm –3 8-HQS. (cf. Table I)
C a l i b r a t i o n p l o t s a n d e f f e c t o f
i n t e r f e r i n g i o n s
The strictly linear calibration plots were evaluated
for seven concentration levels between 0.1 mg dm –3 –
50 mg dm –3 . The points were measured in triplicate. The detection
limits were X ∆ α = 1.26 mg dm –3 , X∆ β = 3.69 mg dm –3
according to Graham, X ∆ m = 1.13 mg dm –3 according to Miller
and 0.30 mg dm –3 according to IUPAC.
For 1–3 mg dm –3 U, no interference were observed for
100 : 1 nO 3 – , Cl – , SO4 2– , SiO3 2– , nH4 + , na + , K + , Ca 2+ , Mg 2+ ,
f
(1)