This journal is © The Royal Society of Chemistry 2004
Table S1 Instrumental operating conditions of the HPLC-UV-HG-AFS set-up.
Anion-exchange
Cation-exchange
HPLC
Column
Hamilton PRP X-100
Chrompack IonoSpher 5C
Dimensions
4.1 mm  250 mm  10 µm
4.6 mm  150 mm  5 µm
Eluent
NH4H2PO4
Pyridinium formate
Injected volume
100 µl
100 µl
Elution program
gradient elution
Elution steps Flow rate Eluent
Elution steps Flow rate Eluent
pH
pH
-1
min
ml min
mM
min
ml min-1
mM
0-1.8
1.5
5
3.5
1-9
1
2
1.9-7
1.1
5
7.1-18
10
2.8
6.0
9.1-22
1.2
5
18.1-31
50
1.5
31.1-35
5
3.5
22.1-27
1.2
2
Flow rate at the determination of total selenium content: 1.0 ml min-1
UV
Thermal reduction
at 122 ºC; with 5 % w/v KBr dissolved in 7.4 % m/m HCl
UV-wavelength
254 nm
HG
Reductive solution
1.5 % w/v NaBH4 dissolved in 0.75 % w/v NaOH solution
Purging Ar gas flow rate
400 ml min-1
Counter-current dryer Ar flow rate 2000 ml min-1
AFS
Primary and boosted currents
25 mA
Table S2 Analytical figures of merit of the HPLC-UV-HG-AFS developed method for the
determination of Se-species. a A minimum of five standards and a blank were used for each
calibration line in the concentration range from 0 to 100 ng ml -1.
b
The relative standard
deviation was established from three independent measurements of solutions containing 5 ng
ml-1 (total Se; Se(IV), MeSeCys and SeCys2), 20 ng ml-1 (SeMet at cation exchange), 50 ng
ml-1 (SeMet at anion exchange), and 100 ng ml-1 (Se(VI) at anion exchange) of the Se-species
considered, respectively.
Retention
Se-species
time, min
Total Se as Se(IV)
–
Cation exchange
Se(IV)
3.5
MeSeCys
8.6
SeMet
14.0
SeCys2
20.0
Anion exchange
SeCys2
2.5
SeMet
4.0
Se(IV)
9.5
Se(VI)
20.1
LOD as ng
Calibration equationa
-1
Se ml
0.3 y = 39179 x + 81333
R2
RSDb
0.9941
2.8
0.6
1.2
7.2
0.5
y = 37105x + 13549
y = 21575x – 18412
y = 4138x – 3347.4
y = 34241x – 21245
0.9997
0.9991
0.9999
0.9949
1.5
2.0
5.6
1.8
0.8
24.5
2.0
55.6
y = 29143x – 25886
y = 12040x – 106907
y = 37105x – 13549
y = 1333.7x + 6605
0.9991
0.9896
0.9997
0.9982
3.9
7.2
2.6
5.1