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1 1 © 2009 PerkinElmer
Stan Smith and Ewa Pruszkowski, Ph.D.,
PerkinElmer, Inc.
NEMC 2013
Collaborative Efforts for Creating a Robust Trace Metals Analytical Procedure for Flue Gas Desulfurization Wastewaters by ICP-MS
© 2011 PerkinElmer
2 2
In 2009 US EPA completed study of wastewater discharges
from the steam electric power generating industry
Focus was on wastewater from flue gas desulfurization
(FGD) systems as these comprised a significant portion of
the plant pollutant discharges
Rulemaking process was begun to address pollutants and
waste streams not already covered in 40 CFR Part 423
(Steam Electric Power Guidelines)
Proposed revisions to the effluent guidelines are expected
May 2014
Background
3 3 FDG Process
Background
Typical FGD treatment system using wet scrubber to
remove SO2 emissions from the flue gas
4 4
ICP-MS currently preferred technique for FGD due to
sensitivity and wide availability (ICP-OES ?)
Current methods 200.8, 6020, and 1638 lack detailed
treatment for interferences associated with FGD
May 2010 EPA proposed draft testing procedure specific to
FGD through a collaborative effort with a contract lab
(instrument-specific)
Draft procedure largely based on 200.8 and 1638 with
additional procedures on handling interferences
Just what does FGD wastewater look like?
Analytical Techniques
Background
5 5
Constituents of FGD wastewater come from the limestone used to
make the slurry, the coal burned, and the water supply
FGD wastewaters vary widely depending on above parameters as well
as the efficiency of the FGD treatment system
FGD Wastewater
Background
Parameter Range (mg/L) Total Dissolved Solids 4000 - 68,000 Chloride 1000 - 35,000 Sulfate 1500 - 8000 Calcium 750 - 4000 Magnesium 1100 - 4800 Sodium 670 - 4800 Boron 10 - 800 Total Organic Carbon 5 - 1100
Also high ppm
Al, Fe, and Mn
Nearly 7%
TDS Polyatomic
Interferences
e.g., 34S16O16O
on 66Zn
6 6
Merriam-Webster Definition of COLLABORATE
1. to work jointly with others or together especially in an
intellectual endeavor
2. to cooperate with or willingly assist an enemy of one's
country and especially an occupying force
3. to cooperate with an agency or instrumentality with
which one is not immediately connected
Collaborative Goals
7 7
Create alternate test procedure for different
instrument and interference removal technology
Along the way, opted to include significantly more detail;
instrument hardware, interference removal techniques
Digestion procedure (1638); evaluate open vessel
digestion vs closed vessel digestion
Minimal dilution needed for signal suppression for best
DLs
Dilution via traditional liquid dilution vs gas dilution
Collaborative Goals
8 8
Collaborative process involves a process where ideas are
exchanged, rarely does the first draft survive as the final
A non-inclusive list
Speaking of Collaboration
9 9
Title: Standard Operation Procedure for Trace Element Analysis of
Flue Gas Desulfurization Wastewaters Using ICP-MS
Collision/Reaction Cell Procedure
Introduction - 1.2 The ICP-MS spectrometer with the Universal Cell
can operate in reaction, collision and standard modes…
The use of instrument configurations and/or accessories designed
to accommodate samples with high dissolved solids levels is highly
recommended…
This method was developed on a Perkin Elmer NexION 300D
ICP/MS using an Environmental Scientific SC-DX FAST Automated
Sample Introduction System.
1.3 …analysis of 13 elements… Al, As, Cd, Cr, Cu, Pb, Mn, Ni, Se,
Ag, Tl, V, and Zn
Procedure Development
10 10
2.4 A NexION 300D ICP-MS (Perkin
Elmer, Shelton, CT) coupled to an SC
DX FAST (ESI, Omaha, NE)
automated sample delivery system is
used for this procedure… The FAST
portion of the delivery system uses a
6-port switching valve containing a
Teflon sample loop…In this procedure,
a 1.5 ml was adequate…
2.5 …The baffled, cyclonic spray
chamber used in the SC DX FAST
introduction system is Peltier-cooled to
2oC to ensure low oxides and greater
stability of the instrument.
Procedure Development, Hardware
11 11
6.1.2 The sample introduction system also
includes a PFA ST concentric nebulizer, 2.0 mm
quartz injector, and baffled cyclonic spray chamber
with gas addition port (ESI, Omaha, NE)…
6.1.3 PVC peristaltic pump tubing, orange-white,
is used to produce a sample flow rate of 270
uL/min…
6.1.4 A mixing tee is used to blend in the internal
standards after the peristaltic pump and before the
nebulizer… The peristaltic pump tubing used for
the internal standard solution is orange-whitered
and when used in combination with orange-white
pump tubing for the carrier solution or sample,
creates a minimum dilution of approximately 8.1%.
Procedure Development, Hardware
12 12
10.2.1 EPA Method 1638 was used as the reference for the
digestion of the samples in which section 12.2 describes
Aqueous Sample Preparation.
Block digestion with vials sealed or open with watch glass
covers?
Sealed results in a dilution factor that must be
accounted for
Open has the potential for contamination
No contamination was noted in digestion blanks
Procedure Development, Sample Preparation
13 13
10.2.2 Transfer a 50mL (± 0.5 mL) aliquot from a well-mixed, acid-
preserved sample to a 50mL block digestion tube.
10.2.3 Add 1.0mL of concentrated nitric acid and 0.25mL
concentrated hydrochloric acid…
10.2.5 Place a ribbed disposable watch glass over the digestion
tube.
10.2.6 Place the digestion tube into a block digester adjusted to
achieve a temperature of approximately 85°C.
10.2.7 Heat for 2 hours after 85°C is obtained.
10.2.8 Remove the tubes from the block and allow to cool.
10.2.9 Add deionized water to digestates to bring them back to 50.0
ml.
Procedure Development, Sample Preparation
14 14
7.2.4 Mixed Interference Check Solution
(Synthetic FGD Wastewater)
7.2.4.2 The following solution is prepared in 1.6% HCl
7.2.4.3 Calcium, 2,000 mg/L
7.2.4.4 Magnesium, 1,000 mg/L
7.2.4.5 Sulfate, 2,000 mg/L
7.2.4.6 Sodium, 1,000 mg/L
7.2.4.7 1-Butanol, 2000 mg/L
Simulates “Typical” FGD Samples
Synthetic FGD Solution
15 15 To Purchase Or To Prepare?
Synthetic FGD Solution
Seemingly simple mixture
Purchase custom solution from commercial supplier
Prepare from neat reagents and stock elemental solutions
Beware contamination in stock solutions
9.3.1.2 In some cases it may not be possible to obtain
interference check solutions that are completely free of
contamination. In these cases, results up to 5X the
reporting limit are acceptable if it is possible to
demonstrate that the isotopic ratios correspond to natural
abundances…
16 16
More detailed descriptions of interference removal techniques
2.0 Hardware Description
2.1 The NexION 300D… allows the analyst to choose the most
appropriate collision/reaction cell (CRC) conditions for each analyte
in FGD wastewater…
Collision Mode: In this mode, the instrument offers conventional
collision cell capability with kinetic energy discrimination (KED). By
using a non-reactive gas, such as helium, the collision mode with
KED removes many of the simple solvent- and argon-based
polyatomic spectral interferences. This makes it ideal for elements
such as Co, Ni, Cu and Zn which are prone to the larger cross-
sectional polyatomic interferences to be concerned about. It is also
effective for other analytes, such as As and Se.
Procedure Development, Interference Removal
17 17
Reaction Mode: A technique that offers the best available detection
capability. This mode, known as DRC (Dynamic Reaction Cell™)
technology, removes the majority of interferences with little or no loss
of analyte sensitivity by using pure reaction gases like ammonia
while not allowing any reaction byproducts to leave the cell which
could cause further interferences. DRC technology features a
scanning quadrupole with a bandpass that removes by-product
reactions created in the Universal Cell. Therefore any reaction gas
can be used and in its pure form… This would be the mode of choice
for the lowest possible detection limits for elements such as Cr, V
and Mn.
Procedure Development, Interference Removal
18 18
Attachment 1: Suggested Mass Choices and Analysis Mode
Procedure Development, Interference Removal
Mass Element of
Interest Analysis Mode
27 Aluminum STD or He
75 Arsenic He
111, 114 Cadmium He
52, 53 Chromium NH3 or He
63, 65 Copper He
208, 207, 206 Lead STD
55 Manganese NH3 or STD
60, 62 Nickel He
78, 82 Selenium NH3 or He
107 Silver STD or He
205, 203 Thallium STD or He
51 Vanadium NH3 or He
66 Zinc He
19 19
Important objective of analytical procedure; achieve detection limits
to support FGD regulations
Due to high TDS of typical FGD wastewaters, some dilution of
samples is necessary to reduce signal suppression and to achieve
minimum internal standard recovery of 60%
What is minimum dilution needed for typical FGD?
Traditional liquid dilution, approximately 1:10 needed
Gas dilution, approximately 1:3 needed
6.1.5 Automated sample dilution, liquid or gas, simplifies the dilution
process and results in less matrix being deposited on the cones
during analysis and minimizes the rinse times normally needed for
difficult matrices…
Procedure Development, Detection Limits
20 20
Developing MDLs for EPA’s Draft Collision Cell ICP/MS Procedure for
Determination of Metals in FGD Effluent Samples
Round Robin conducted by EPA and contractor with several
participant labs
Specific to subset of elements of particular interest to EPA; As, Cd,
Cr, Pb, Se, and Tl
Procedure Development, Detection Limits
MDLs in Synthetic FGD (KED/Collision Mode)
Cr 52
(ug/L)
As 75
(ug/L)
Se 78
(ug/L)
Cd 111
(ug/L)
Tl 205
(ug/L)
Pb 208
(ug/L)
0.168 0.520 1.102 0.032 0.003 0.036
21 21
Mass/Element
Int. Time
(sec) Mode
Internal
Standard MDL (µg/L)
27 Al 0.5 STD Sc 0.54
51 V 0.5 NH3 In 0.02
52 Cr 0.5 NH3 In 0.09
55 Mn 0.5 NH3 In 0.27
60 Ni 0.5 He Ge 0.28
63 Cu 0.5 He Ge 0.30
66 Zn 0.5 He Ge 1.20
75 As 1.5 He Ge 0.30
78 Se 1.5 He Ge 1.01
107 Ag 0.5 STD In 0.03
111 Cd 0.5 He Ge 0.03
205 Tl 0.5 STD In 0.01
208 Pb 0.5 STD In 0.04
Determined in Synthetic FGD
Obtained Method Detection Limits
Attachment 10: Typical Method Detection Limits
22 22
The SOP is available on the Steam Electric/FGD web page:
http://water.epa.gov/scitech/wastetech/guide/steam-electric/fgd.cfme
The Final Product
23 23
Specific to FGD wastewater
Addresses physical matrix issues (robust)
Addresses interference removal techniques (UCT)
Specific hardware
Enough detail to run the procedure
Procedure Highlights
24 24
Thanks to the Collaboration Team
U.S. Environmental Protection Agency
Office of Science and Technology
Engineering and Analysis Division (EAD)
Washington, DC
CSC
Engineering and Mission Support
Alexandria, VA
Perkin Elmer, Inc.
Shelton, CT
Thanks
25 25
Questions