prepFAST-MC Environmental :
Bioavailable Trace Metals
Elemental Scientific
Authors: Hwan Kim and Paul Field ([email protected])
Brief
The prepFAST-MC is a fully automated low pressure chromatography system that can isolate and collect
discrete fractions from a dissolved sample. The syringe driven system allows sample loading, elution and
column conditioning cycles all with user-defined parameters (time, volume and flow rate).
Features:
Total Dissolved and Bioavailable Metal in Carter Lake
•Fully automated bioavailability
Mn Total: 212
Mn Bioavailable: 96%
3 Concentra)on in ppb  Load exact volume
 Dispense exact volume
 Accurate, precise flow rate
• All fluoropolymer flow path
• 3 Destination locations
Concentra)on (mg/L)
(ppb) •Syringe control
Element Cd Co Cu Fe Mn Ni Pb Zn 2 Bioavailable 0.0023 0.0092 0.33 0.68 204 0.044 0.010 0.29 1 35% • Flexible chemistry
17% 0 Elemental
Scientific
Total 0.0121 0.04 1.94 1.95 213 0.54 0.018 1.28 19% 24% Cd Co 23% 8% Cu Fe Mn Labile Total Ni 56% Pb Zn Figure 1. Concentrations for dissolved (blue bars) and bioavailable (red bars) trace
metals are plotted. The percent bioavailable fraction of dissolved metals in Carter
Lake, IA / NE (above each red bar) indicates a wide range from 8% (Ni) to 96% (Mn). Large ranges in the bioavailable fraction are expected in natural waters as variable
organic ligand concentration, complexation, pH and ionic strength all affect the colloidal
partitioning of each metal differently.
1
Automated Extraction
1
Sample
Nebulizer**
Sample In
SC-4 DX
V1
Destination 2
Bioavailable
DIWater
DIWater
V1
V2
To Loop
3
Reagent1 Reagent3 Reagent5
Reagent2 Reagent4 Reagent6
Colloidal
V2
Destination
Nebulizer**
2 Destination 1
From Loop
Nebulizer**
4
Nebulizer**
Waste
V1
V2
V1
V2
From Loop
From Loop
**For Inline Method Development Only
Figure 2. The prepFAST-MC system schematic illustrates four steps, 1) load sample into loop, 2) push sample
onto column and collect colloidal, 3) elute and collect bioavailable, 4) condition and regenerate.
Abstract
A simple, fully automated
prepFAST-MC method is used
to extract bioavailable metals
from the total dissolved fraction
of natural, fresh waters. The
operationally defined Chelex
labile fraction is collected
after a sample at natural pH is
exposed to a bed of resin for
0.25 seconds (Bowles et al.,
2005). Concentrations of Chelex
labile and total dissolved metals
determined by ICP-MS are used
to calculate the bioavailability
of each metal. Excellent
reproducibility (rsd=0.7%; n=3)
for replicate determinations of
bioavailable Cu in natural waters
is achieved through automation. Water collected from Carter
Lake, IA / NE exhibits a range in
bioavailability for a suite of metals
(Co =24%, Mn =96%, Fe =35%,
Cu =17%, Ni =8%, Zn =23%,
Cd =19% and Pb =56%) that is
typical of natural waters.
Column Chemistry
1) Load sample
2) Column elution
3) Condition/regenerate
Natural
pH
Acid
pH < 1
Buffer
pH ~ 5.7
Colloidal
Fraction 1
Bioavailable
Fraction 2
Waste
Figure 3. The three main steps in processing samples for the determination of
bioavailable metals are illustrated: 1) 10 mL of sample at natural pH is passed
through a Chelex column (~ 0.25 sec exposure time) retaining bioavailable metals
and collecting the colloidal fraction (Destination 1), 2) Metals are eluted from the
column at low pH (<1) and collected as the bioavailable fraction (Destination 2), and
3) Regenerate / recondition column for next sample (pH 6.7).
2
Flow Rate Determination
Selected Flow rate
20mL/min = 0.25 sec Exposure Time
Cu-NTA
Figure 4. The bioavailable Cu fraction is plotted as a function of flow rate for inorganic Cu (green diamonds)
Cu-NTA (100µg/L Cu, 1mM NTA, pH 6.1; blue diamonds) and Cu spiked lake water (red squares; natural
pH). At a 20 mL/min flow rate (0.25 sec exposure) all inorganic Cu (100%) and approximately 40% of Cu-NTA
is retained by the column while flow rate has little effect on the retention of Cu in natural lake water. These
results are consistent with the operationally defined bioavailable fraction for Chelex resin (0.25 sec exposure
time; Bowles et al., 2005).
Reproducibility at 20 mL/min
50 Average: 25.31
25.3
Average:
RSD%:
0.7
RSD%: 0.7
Bioavailable Cu (%) 40 30 25.2 25.5 25.2 1 2 3 20 10 0 Trials Figure 5. Three replicate determinations of bioavailable Cu in natural waters indicate excellent precision is
obtained through automating chemistry.
3
5 x 12
Samples
5 x 12
Destination
1
5 x 12 2
Desination
5 x 12
Destination
3
Figure 6. SC-4 DX top view with locations for Samples, Destination 1, Destination 2,
and Destination 3. Vial sizes, styles and rack configurations are flexible.
Benefits:
• Fully automated
• Collect all bioavailable and colloidal fractions
• Routine
• Software controlled
• Excellent reproducibility through automation
• Flexible (can be adapted for other resins
or chemistries)
• Inert flow path
• Micro column reduces sample/reagent volumes
K.C. Bowles, S.C. Apte, G.E. Batley, L.T. Hales,
N.J. Rogers. "A rapid Chelex column method for
the determination of metal speciation in natural
waters." Analytica Chimica Acta. (2005)
7277 World Communications Drive
Phone: 1.402.991.7800
|
|
Omaha, NE 68122 USA
Fax: 1.402.991.7799
Email: [email protected]
Web: www.prepFAST.com
|
Elemental Scientific
www.icpms.com
14066
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