The Bonded-Phase
M+
M+
M+
M+
M+
Support
Exploring a Combinatorial
Approach
H2 N
C
COOH
SH
Cysteine
OH
Tyrosine
Anion Binding
Residues
C
CH2
+
NH2
NH2
Arginine
+
C
NH3
Lysine
O
O
O
Aspartate
OGlutamate
Other Chelating Residues
(CH2)4
NH
CH2
C
R
(CH2)3
CH
CH2
N
NH
C
To ICP-MS
CH2
CH2
O
CH2
NH2
C O HN
Asparagine
NH2
Tryptophan
Glutamine
Histidine
Developing Fluorescencebased Sensors
Creating Chemical-free
Remediation Systems
Internal Standards for ICPTOF-MS
High Throughput Screening of
Combinatorial Libraries
Eapplied
U
Cd
Library of
Oligopeptides
Auxiliary
Electrode
2
Cu
valve
1.2
U238/Hf178
1
U238/As75
0.8
0.6
0.2
U
Determine what
exclusively binds U
Fluorescence
Microscopy
Metal
Recovery
Stream
High throughput
screening
ETV-ICPMS
UO22+ in solution
Absorption bands: 330-350nm,
390-440nm
Electrothermal vaporization
inductively-coupled plasma
mass spectrometry
Emission bands: 470-570nm with
lmax at 485nm, 510nm, 535nm,
and 560nm
Resonance energy transfer (RET) can be used to determine
various characteristics of metal binding. RET involves the
transfer of energy between a fluorescent donor and an acceptor
molecule. The efficiency of the energy transfer is dependent on
the distance between the molecules, which can be related to
their spectroscopic properties.
Bind
metal
Moulin, C. et al. Anal. Chem., 1995, 67, 348-353
Bead in metal
solution
LED - stage illumination
TackyDot™
slide to array
beads
Clean Effluent
Stream
Metal-bound
bead in acid
solution
Free metal can be
bound and released
by exposing the
ligand to successive
reduction and
oxidation cycles.
• Single bead screening
• Applicable for wide range of
metals
• Based on fluorescence
of bound species
• Quantitative elemental
information
• Non-destructive
• Non-destructive
• Non-destructive
Working
Electrodes
Questions? Email Shelly.
slcascaito@mail.utexas.edu
6
7
8
9
10
11
12
13
14
15
Torch Position (mm)
1.0E+07
5.0E+06
0.0E+00
0
2
4
6
8
10
0
2
4
Time, s
6
8
10
6
8
10
Time, s
8.0E+06
6.0E+06
4.0E+06
2.0E+06
0.0E+00
0
2
4
6
8
10
0
2
4
Time, s
Time, s
One problem with ICP-MS is elements of the same nominal
mass (isobaric interference). ETV can be used to separate
some problematic elements based on their differing
volatilities. Rb and Sr can be separated to remove the isobar
at mass 87.
Determining the Relationship Between
%RSD and Chemical Properties
Mn+
A
Mn+
Mn+
Mn+
r = 0.0037
r = 0.81
Mn+
Oxidation
238U/(IS)
Counter
Electrodes
Flow
• Bulk screening
0
Mn+
Reduction
1mm
• Bulk/single bead screening
An electrical
potential is used
to change the
binding
characteristics of
the column.
By definition, a small change
in the ratio between two
elements as a condition
changes, is indicative of a
good analyte-IS pair. The
%RSD of these ratios is used
as a quantitative measure of
internal standard
compatibility.
1.5E+07
Mn+
Metal solution to
be quantified
Questions? Email Carina.
cgunder@mail.utexas.edu
Second Vaporization Stage
2.0E+07
60.0%
Mg 1:10
50.0%
B
Ti 10:1
40.0%
Ti 1:1
%RSD
CGGDCCGDGC
Bell and Biggers. J. Molec. Spec., 1965, 18, 247-275
Sample
1.4
0.4
High Throughput Screening Techniques
Polycapillary optic/
Si Li detector
x-ray source
1.6
Reference
Electrode
Sequence peptide
Micro-x-rayfluorescence (MXRF)
1.8
3-electrode
potentiostat
%RSD
Synthesize
polypeptide(s)
and characterize
uranium binding
Graphical Illustration of %RSD
Normalized Ratio
M
ETV-ICP-MS for Isobars and
Isotopes
First Vaporization Stage
Column
+
Exposure to
mixed metal
solution
Though many labs rely on solution nebulization
for sample introduction, this is not always the best
technique. It can be problematic for some matrices
(e.g. salty solutions, organic solutions, and solids or
slurries). An alternative is electrothermal vaporization
(ETV). This uses a carbon tube to vaporize the sample
before introduction to the ICP-MS. Vaporization
temperatures of up to 3,000o C can be achieved in a
controlled manner. It can handle a wide variety of
sample types, and generally has higher sample
introduction efficiency than nebulizers.
Intensity
M+
2
CH
Intensity
M+
CH
CH
H
Δmass
238U/(IS)
Isotope Ratio Error
Ion-Exchange System
ICP-MS is the cutting edge technology for atomic
spectrometry. It can offer part per trillion detection
limits, over 5 orders of magnitude of linear response,
and works for almost all elements in the periodic table.
It uses an inductively coupled plasma (~8,000 K) as the
ionization source. Our ICP-MS uses a time of flight
system for mass analysis.
Cation Binding Residues
Sample
For the past several years, one of the primary
focuses of our research group has been the
development of novel ion-exchange systems for the
purpose of metal remediation from aqueous systems.
Expanding on hints from Mother Nature, we chose to
explore the metal chelation abilities of proteins and, in
particular, their constituent amino acids. In order to
simplify these ion-exchange systems, short-chain
homopolymers consisting of repeating monomers of a
specified amino acid residue have been used. These
systems exhibit many of the characteristics for an ideal
ion-exchanger – strong binding; fast, efficient release
and structural stability. These biologically-based
systems also have the added benefit of being
environmentally friendly, unlike many traditional
exchange systems which require harsh extraction
agents.
Amino Acid
ΔIP
30.0%
Ba 10:1
20.0%
Ba 1:1
10.0%
0.0%
2050
-10.0%
2100
2150
2200
2250
2300
2350
2400
2450
-20.0%
-30.0%
-40.0%
Scale up of the
electrochemical reactor to
practical size requires
consideration of materials,
geometry, operating
conditions, and overall cost.
Questions? Email Ram.
ramk@mail.utexas.edu
Visit us! On the web: http://research.cm.utexas.edu/jholcombe/index.html
Detector Potential
Each point on the scatter plots illustrated in the example plot
above represents a ratio of 238U and one of approximately 100
IS considered. Analyte-to-IS mass separation typically offered
the strongest and most consistent relationship to %RSD for
all conditions.
Questions? Email Haley.
hjf244@mail.utexas.edu
In the Lab: Welch 3.240 and 3.238
The time of flight design is able to offer excellent isotope ratio
precision as a result of simultaneous ion extraction from the
plasma. However, difficulties have been encountered with ratio
accuracy. Factors that cause this and possible fixes are
actively being researched.
Questions? Email Adam.
adamrowland@mail.utexas.edu