Transcript The Separation of Beryllium from Spectral Interfering

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The Separation of Beryllium from Spectral
Interfering Elements in Inductively Coupled
Plasma – Atomic Emission Spectroscopic Analysis
Daniel R. McAlister and E. Philip Horwitz
PG Research Foundation, Inc.
8205 S Cass Avenue, Suite 109
Darien, IL 60561
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Problems with Current Method
Interfering elements in the AES spectrum of Beryllium
a
Table 1. Potential Spectral Interferences for Be determination by ICP-AES
Analyte Peak (nm)
Intensity
Analyte Peak (nm)
Intensity
Cr
312.870
15.0
Nb
313.079
2200.0
U
312.879
6.0
Ti
313.080
6.0
Zr
312.918
400.0
Ce
313.087
65.0
Nb
312.964
22.0
Th
313.107
27.0
b
Be
U
312.973
15.0
313.107
41000.0
Zr
312.976
550.0
Tm
313.126
2300.0
Th
312.997
10.0
U
313.132
8.0
V
313.027
1020.0
Hf
313.181
20.0
OH
313.028
0.0
U
313.199
15.0
Ce
313.033
50.0
Cr
313.206
1000.0
b
Be
313.042
64000.0
Zr
313.207
7.0
U
313.056
6.0
Th
313.226
5.0
OH
313.057
0.0
Mo
313.259
1800.0
U
313.073
0.0
Ce
313.259
30.0
a
As listed in Varian Plasma96 software version 1.12
b
Commonly used peaks for beryllium determination by ICP-AES
Beryllium lines very
intense  method is very
sensitive for the
determination of beryllium
Interfering lines from other
elements could lead to false
positives.
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Uptake of Selected Elements on Dipex Resin
10
5
k' for U(VI) and Th(IV)
4
> 10 for all HNO3
a
Several EXC materials
evaluated
10
4
Zr
Nb
Dipex offered the most
promising beryllium
retention characteristics
10
3
Ce
Be
k' 10
2
V
10
10
10
1
Be(II)
Ce(III)
Zr(IV)
Nb(V)
Cr(III)
V(V)
0
Cr
-1
10
-2
10
-1
10
0
10
1
[HNO3]
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Uptake of Selected Elements on Dipex Resin
10
5
Single column should
remove all ICP-AES
interferences
b
10
Ti
4
Hf
Tm
10
3
Load pH 2-4
Mo
Rinse 0.2 M HNO3
Be
k' 10
2
Strip Be with 4 M HNO3
10
10
10
1
0
Potential for 2-10 x
concentration of Be
depending on sample
size
Be(II)
Mo(VII)
Ti(IV)
Hf(IV)
Tm(III)
-1
10
-2
10
-1
10
[HNO3]
0
10
1
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Uptake of Selected Elements on Dipex Resin
10
5
a
10
4
10
3
Resin selective for Be
over other alkaline earth
metal ions
Be(II)
Mg(II)
Ca(II)
Sr(II)
Ba(II)
Be
k' 10
Ca and Mg common
matrix impurities
2
Ca
10
1
10
0
Ba
Sr
Mg
10
-1
10
-2
10
-1
10
0
10
1
[HNO3]
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Uptake of Selected Elements on Dipex Resin
10
5
b
10
4
10
3
k' 10
2
Fe(III) strongly retained
Al(III) and Pb(II) have similar
retention to Be(II)
Fe
Cu(II) more weakly retained
Pb
Large amounts of Fe(III)
could interfere with Be(II)
uptake
Al
Cu
Be
10
10
10
1
Be(II)
Fe(III)
Cu(II)
Pb(II)
Al(III)
0
-1
10
-2
10
-1
10
0
10
1
[HNO3]
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Uptake of Selected Elements on Dipex Resin
10
5
c
10
4
10
3
k' 10
2
Resin selectively retains Be(II)
over most other divalent metal
ions
Be(II)
Cd(II)
Zn(II)
Hg(II)
Mn(II)
Be
Cd
Mn
Be(II) can be separated from
samples containing large
quantities of divalent metal ion
impurities
Zn
10
1
10
0
10
Hg
-1
10
-2
10
-1
10
0
10
1
[HNO3]
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Proposed Method for Beryllium Purification
Prepare samples as before (Digest with H2SO4/H2O2, dilute with HNO3)
Neutralize samples to pH 1-2 with sodium aceate
Buffers to maximum pH of 4.5
Monitor pH with methyl violet or crystal violet or pH strip
pH
0.0
0.3
0.5
1.1
1.6
2.8
3.4
4.0
4.5
pH Range over which separation is effective
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Elution of Be and Selected Elements on Dipex Resin
10
3
Load 5.5 cm digested ashless filter + 140 g Be, Al, V and Cr
neutralized to pH 2.0 with 3.4 M Sodium Acetate
10
2
Rinse
0.2 M
HNO3
Cr
10
1
Be
ppm
Al
10
0
10
-1
10
-2
10
-3
Strip
4.0 M
HNO3
1 mL/min
mL %Be
6
66
8
79
10
92
12
95
14
97
16
97
Background
V
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Bed Volumes
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ppm
Elution of Be and Selected Elements on Dipex Resin
10
3
10
2
10
1
10
0
Load 5.5 cm digested ashless filter + 140 g Be, Ce, Nb, U and Zr
neutralized to pH 1.0 with 3.4 M Sodium Acetate
Ce
Rinse
Strip
Strip
0.2 M
4.0 M
mL %Be
0.2 M
Be
HNO3
HNO3
6
86
Na4EDTA
8
90
U
10
91
12
93
14
94
16
94
Zr
10
-1
10
-2
10
-3
Nb
Background
0
5
10
15
20
25
30
Bed Volumes
35
40
45
50
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Elution of Be and Selected Elements on Dipex Resin
10
3
10
2
ppm
10
10
Load 5.5 cm digested ashless filter + 140 g Be, Hf, Mo, Ti, Tm and Th
neutralized to pH 1.0 with 3.4 M Sodium Acetate
mL
6
8
10
12
14
16
1
0
10
-1
10
-2
10
-3
%Be
84
89
91
94
94
97
Rinse
0.2 M
HNO3
Be
Strip
0.2 M
Na4EDTA
Strip
4.0 M
HNO3
Th
Ti
Hf
Background
0
5
10
15
20
25
30
Bed Volumes
35
40
45
Tm
Mo
50
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Simulated Sample Results
Successfully separated Be from samples digested with
H2SO4/H2O2
Several different digested methods employed in Be
analyses (HCl, H2SO4, HNO3, HF, H2O2, HClO4)
High levels of impurities
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Digestion Methods using HF
3
10
Rinse
0.2 M
HNO3
Load
2
10
Strip
4.0 M
HNO3
(1 mL/min)
No Boric Acid
1
ppm
10
98% of Be
0
10
-1
10
2% of Be
-2
10
0.1 M Boric Acid
Background
-3
10
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Bed Volumes
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Separation of Be from Large Amounts of Interferences
®
Capacity of Dipex Resin for Selected Metal Ions
Metal Ion
®
Dipex capacity
U(VI)
mg/2 mL bed
N/A
N/A
a
102.6
Ti(IV)
12.5
Th(IV)
60.6
Fe(III)
22.6
Pb(II)
53.8
Ca(II)
Be(II)
Cr(VI)
Mo(VI)
mg to reduce
c
Be yeild to 90%
> 100
25
25
b
7.5
a
10
a
10
b
50
10.4
a
>100
0.9b
0.5
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Separation of Be from Large Amounts of Interferences
100 mg Cr
50 mg Fe
10 mg Ti
100 mg U
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Uptake of Selected Metal Ions on LN2 and LN3 Resins
10
O
10
4
10
3
10
2
k' for U, Th, Ti, Fe
3
>10 for all [HNO3]
Be
Ca
10
1
10
0
10
U(VI), Th(IV), Ti(IV)
retained from all
[HNO3]
k' for U, Th, Ti
3
>10 for all [HNO3]
LN2: Strongly retains
Fe(III)
k'
P
OH
LN3
LN2
5
Be
k' for Mg, Sr, Ba
<1 for all [HNO3]
-1
10
-4
10
-3
LN3: Be not retained
from pH < 2
-2
10
[HNO3]
10
k' for Mg, Ca, Sr Ba
<1 for all [HNO3]
-1
10
-4
10
-3
-2
10
[HNO3]
10
-1
Choice of LN2/LN3
depends on desired
operating conditions
and amount of Fe in
samples
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Elution of Be on LN2 and LN3 Guard Columns
ppm Be vs. Bed Volumes of Eluate
o
2.0 mL Resin, 50-100 m, Assisted Gravity Flow 2.0 mL/min, 22(2) C
3
10
Load
pH 2
2
10
Strip
4.0 M
HNO3
(1 mL/min)
Rinse
0.2 M
HNO3
LN3
1
ppm
10
LN2
0
10
Background
-1
10
-2
10
93 % Be
6 % Be
1 % Be
5% Be
10% Be
85% Be
-3
10
0
2
4
6
8
10
12
14 16 18
Bed Volumes
20
22
24
26
28
30
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Effect of Large Quantities of Uranium
a
Beryllium Yields and Uranium Impurity vs mg Uranium in Load Solution
2 mL Beryllium Resin
2 mL Beryllium Resin
2 mL Beryllium Resin
+ 2 mL LN2
+ 2 mL LN3
g U in
g U in
g U in
% Be
% Be
% Be
b
mg U
in 12 mL
Be fraction
0.14
10
25
50
75
100
90
92
86
61
N/A
29
< 1.5
< 1.5
< 1.5
< 1.5
N/A
580
c
b
b
in 12 mL
Be fraction
in 12 mL
Be fraction
85
N/A
87
88
81
88
< 1.5
N/A
< 1.5
< 1.5
< 1.5
< 1.5
N/A
N/A
97
97
93
79
N/A
N/A
< 1.5
< 1.5
< 1.5
< 1.5
a
Whatman filter paper spiked with 0.14 mg Be, digested with H2SO4/H2O2, and neutralized with
sodium acetate to pH 1.8
b
Beryllium Resin Strip Solution 4.0 M HNO3
c
Detection limit for Uranium by ICP-AES under the experimental conditions
LN2 and LN3 Resins effectively increase the capacity for Uranium
With LN2, the GC remains connected through the load, rinse and strip
With LN3, the GC can be removed following the rinse
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Conclusions
Efficient, Reliable method for purifying Be from all ICP-AES spectral
interfering elements has been found using a single column
Method is compatible with current monitoring and sample digestion
methods
Method is robust and performs over a wide pH range
Inserting a LN2 or LN3 Resin guard column increases U capacity
without changing the chemistry or significantly decreasing Be yields.
Working to develop methods to isolate Be from high levels of other
impurities
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