2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P78 SEPARATION AND PRECONCENTRATION
OF ARSENIC, ANTIMONy, SELENIuM AND
TELLuRIuM ON MODIFIED SILICAGELS
FOR ThEIR DETERMINATION by ICP-AES
KRISTýnA URBánKOVá, LUMíR SOMMER and
MARTIn MOOS
Brno University of Technology, Chemistry and Technology of
Environmental Protection,Purkyňova 118, 612 00 Brno,
urbankova@fch.vutbr.cz
Introduction
The determination of toxic or ambivalent microelements
arsenic, antimony, selenium and tellurium in water samples
requires inevitably a preconcentration prior to the determination
by ICP-AES. The separation and preconcentration by
various solid phase extractions were earlier studied and such
technique widely used for water samples. The complexation
of these elements with organic reagents is of particular
interest when interacting with various kinds of silica sorbent
used. 1–5 The combination of organic reagent with cationic
surfactant was examined for sorption in this paper.
Experimental
C h e m i c a l s
All chemicals and solvents used were of analytical grade
quality.
Astasol standards for arsenic, antimony, selenium and
tellurium containing 1.000 ± 0.002 g dm –3 of element were
from Analytica Prague, Czech Republic.
The cationic surfactant 1-ethoxycarbonylpentadecyltrimethylammonium
bromide (Septonex ® ) from Aventa, Czech
Republic and organic reagents 4-(2-Pyridylazo)resorcinol
(PAR), Pyrrollidincarbodithioate (APDC), thiourea (THU)
and 1,2-dihydroxybenzene (PYR) from Lachema, Czech
Republic, diethyldithiocarbamidate (DTC) from Fluka,
Switzerland and 8-hydroxyquinoline-5-sulphonic acid (8-
HQS) from Aldrich, Germany were used.
Modified sorbents were Separon SGX C18, C8, SGX
nH 2 , SGX Cn, SGX RPS and SGX Phenyl with particle size
60 μm, from Tessek Prague, Czech Republic.
I n s t r u m e n t a t i o n
An echelle based ICP-spectrometer with a prism-predisperser
IRIS AP, (Thermo Jarell Ash) and CID detector with
512 × 512 pixels for 195–900 nm, axial plasma discharge of
1.35 kW and echelle grating with 54.4 lines were used.
The following spectral lines [nm] As 228.8, Sb 231.1,
Se 190.6 and Te 214.2 were suitable for final evaluation
only because of their high intensity, selectivity and low background
influences.
s497
Results
S o r p t i o n o f E l e m e n t s o n t h e
S i l i c a S o r b e n t i n t h e P r e s e n c e o f
S u r f a c t a n t
Prior to the sorption, the column was conditioned
successively with 10 ml of distilled water and 10 ml of
5 × 10 –4 – × 10 –2 mol dm –3 aqueous solution of surfactant.
50 ml of solution containing 1 mg dm –3 of As, Sb, Se and
Te (each of them) was always sorbed by a flow rate 1.0–
3.0 ml min –1 at pH 7. The column was then rinsed with 10 ml
of distilled water and the elements eluted with 10 ml of acetone-ethanol
(1 : 1) mixture in the presence of 0.1 mol dm –3
HCl which showed the highest elution efficiency. The organic
eluent was always removed by evaporation under an infra-red
lamp to 1 ml in a suitable Teflon dish.
5 × 10 –3 mol dm –3 Septonex ® is optimal for the retention
of inorganic form of As, Sb, Se and Te. The recovery values
decrease from concentration larger than 1 × 10 –2 mol dm –3
Septonex ® because of the competing influence of micelles
formed under these conditions in solutions. The recovery was
nearly 100 % on SGX C18 (C8) for Sb, Se and Te but for As
it reaches 60 % only. On the other sorbents, the sorption efficiency
decreased. As was retained from 4 % on SGX Phenyl
to 15 % on SGX Cn. 70 % retention of Sb was on SGX nH 2 .
The recoveries for Se were about 90 % for SGX nH 2 , RPS
and Phenyl. On the other hand, more than 40 % of Te was
retained on sorbent SGX RPS and nH 2 .
E f f e c t o f O r g a n i c R e a g e n t s
The retention of monitored microelements was carried
out from 50 ml of solutions containing 1 mg dm –3 of each
metal with organic reagents when the column was previously
conditioned by 5 × 10 –3 mol dm –3 Septonex ® only.
The sorption from solution containing 0.85 × 10 –4 –
3.35 × 10 –4 mol dm –3 PAR was quantitative for Separon
SGX C18, SGX C8, SGX Cn for Sb, Se and Te. On SGX
C18 and C8 the retention of complexes was nearly 100 % for
2.77 × 10 –4 –1.1 × 10 –3 mol dm –3 8-HQS and also 6.25 × 10 –4
–8.33 × 10 –3 mol dm –3 PYR. The recoveries about 90 %
were observed for 4.86 × 10 –4 –7.29 × 10 –4 mol dm –3 APDC
and about 80 % for 4.90 × 10 –4 –1.50 × 10 –3 mol dm –3 DTC
or 1.05 × 10 –3 –4.20 × 10 –3 mol dm –3 THU for Sb, Se and
Te. The sorption of As was far from being quantitative.
1.70 × 10 –4 mol dm –3 PAR can be used for the retention of As,
Sb, Te on SGX nH 2 and SGX RPS for As, Sb, Se. On the
other hand, 2.77 × 10 –4 mol dm –3 8-HQS is optimal for Se on
SGX nH 2 and SGX Phenyl and 2.43 × 10 –4 mol dm –3 DTC
was suitable for the retention of Te on SGX RPS, SGX Phenyl
and for As on SGX Phenyl.
E f f e c t o f S a m p l e V o l u m e
The influence of sample volume was tested for the retention
from 50–1,000 ml solution containing 0.2–0.01 mg dm –3
each of element in the presence of the particular organic reagents
after conditioning. This corresponds to a 5–100-fold