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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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…

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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

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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

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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

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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

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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

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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

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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

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Specific to FGD wastewater

Addresses physical matrix issues (robust)

Addresses interference removal techniques (UCT)

Specific hardware

Enough detail to run the procedure

Procedure Highlights

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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

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Questions