Wh ite Pa p er 7 04 2 3
Evaluation of Various Anion-Exchange
Chemistries for the Analysis of Haloacetic
Acids in Drinking Water Using 2-D Matrix
Elimination Ion Chromatography and
Suppressed Conductivity Detection
Kannan Srinivasan, Rong Lin, and Christopher Pohl
Thermo Fisher Scientific, Sunnyvale, CA, USA
Executive Summary
Table 1. What Are HAAs?
Haloacetic acids (HAAs) are drinking water disinfection
byproducts that are regulated due to their potential
carcinogenicity. Analysis of trace levels of HAAs in high
ionic strength drinking water matrices is challenging.
Traditional GC methods require laborious and timeconsuming sample preparation and derivatization steps
prior to analysis. Direct injection IC-MS-based methods
are highly sensitive and selective, and obviate the need
for extensive sample pretreatment and derivatization, but
ESI-MS instrumentation may not be readily available in
routine monitoring laboratories. Two-dimensional matrix
elimination IC (MEIC) with suppressed conductivity
detection is a simple and cost-effective alternative for
sensitive and selective quantitative determination of ppb
levels of HAAs in drinking water samples. Optimization of
anion-exchange chemistry is critical for maximum method
performance.
Abbreviation
Chemical
Formula
pKa
Boiling
Point °C
Monochloroacetic Acid
MCAA*
ClCH2CO2H
2.86
187.8
Dichloroacetic Acid
DCAA*
Cl2CHCO2H
1.25
194
Acid
Trichloroacetic Acid
TCAA*
Cl3CCO2H
0.63
197.5
Monobromoacetic Acid
MBAA*
BrCH2CO2H
2.87
208
Dibromoacetic Acid
DBAA*
Br2CHCO2H
N/A
195
Tribromoacetic Acid
TBAA
Br3CCO2H
0.66
245
Bromochloroacetic Acid
BCAA
BrClCHCO2H
N/A
103.5
Dibromochloroacetic Acid
DBCAA
Br2ClCCO2H
N/A
N/A
Dichlorobromoacetic Acid
DCBAA
Cl2ClCCO2H
N/A
N/A
* MCAA, DCAA, TCAA, MBAA, and DBAA are collectively referred to as HAA5.
Keywords
Abstract
Haloacetic acids, Water analysis,
2-D ion chromatography, ICS-3000
Disinfecting water is an important step when processing drinking water. However, commonly used
disinfectants, such as chlorine, chlorine dioxide, chloramine, and ozone, react with naturally
occurring organic and inorganic matter in the source water to form disinfectant byproducts that
are potentially harmful to humans. The U.S. EPA has regulated five haloacetic acids referred to
as HAA5, which include monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid. Stage 1 Disinfectants/Disinfection Byproducts Rule
regulates the HAA5 at 60 μg/L annual average.
U.S. EPA Methods 552.1, 552.2, and 552.3 are presently used for analyzing the HAAs. These
methods are labor intensive and require multiple extraction and derivatization steps. Recently, a
direct injection IC-MS and IC-MS-MS method that uses a high capacity Thermo Scientific™
Dionex™ IonPac™ AS24 anion-exchange column showed excellent separation of nine HAAs and
bromate with greater than 90% recovery in the presence of high concentrations of matrix ions such
as chloride and sulfate. In this analysis, we evaluated a direct injection suppressed conductivity
detection method for analyzing HAAs. Additionally, we evaluated the use of two-dimensional
MEIC in conjunction with various column chemistries such as Dionex IonPac AS11-HC, AS16,
AS19, and AS24.
2
U.S. EPA Regulation
Current: Stage 2 Disinfection Byproducts Rule (DBPR)
• Monitoring of HAA5 at all plants that disinfect with chlorine
– Total MCAA, MBAA, DCAA, DBAA, and TCAA
– Maximum contamination level (MCL) = 60 µg/L annual average
• Maximum contamination level goal (MCLG)
– DCAA should not be present
– TCAA less than 30 µg/L
•Bromate
– MCL = 10 µg/L
– MCLG = not present
Drinking Water Matrix
Sulfate in drinking water currently has a secondary maximum contaminant level (SMCL) of
250 mg/L, based on aesthetic effects (i.e., taste and odor). This regulation is not a federally
enforceable standard, but is provided as a guideline for states and public water systems. U.S. EPA
estimates that about 3% of the public drinking water systems in the country may have sulfate levels
of 250 mg/L or greater.
• Chloride 250 mg/L
• Nitrate 20 mg/L
• Ammonium chloride 100 mg/L
Current Methods
• U.S. EPA 552.1, 552.2, and 552.3
Liquid-liquid microextraction, derivatization, and gas chromatography with:
(a) Electron capture detection
(b) Mass spectrometry detection
• Suppressed ion chromatography with MS or MS-MS detection:
– Direct injection method
– Matrix diversion setup
– No need for liquid-liquid extraction or sample pretreatment
– No need for derivatization
– Fully automated
– Coelution not an issue since MS is a selective detector
– Recovery >90%
Table 2. Column chemistry details.
Functionality
Capacity µeqv/
Column
Hydrohobicity
Dionex IonPac AS16, 4 × 250 mm
Alkanol quaternary ammonium
170
Ultralow
Dionex IonPac AS19, 4 × 250 mm
Alkanol quaternary ammonium
240
Low
Dionex IonPac AS20, 4 × 250 mm
Alkanol quaternary ammonium
310
Low
Dionex IonPac AS24, 2 × 250 mm
Alkanol quaternary ammonium
140
Ultralow
Column
3
Peak Identification:
1. Fluoride
2. Acetate
3. MCAA
4. Bromate
5. Chloride
6. MBAA
7. Nitrite
8. Nitrate
1.5
5
1
10
9. Bromide
10. DCAA
11. Chlorate
12. DBAA
13. Carbonate
14. TCAA
15. Sulfate
8,9
µS
55.00
13
Peak Identification:
1. Fluoride
11. Chlorate
2. Acetate
12. Benzoate
3. MCAA
13. Bromide
4. Chlorite
14. Nitrate
5. MBAA
15. TCAA
6. Bromate
16. Carbonate
7. Chloride
17. Sulfate
8. DCAA
18. Phosphate
9. DBAA
10
10. Nitrite
7
15
11
1
2
10
6
9
18
14
11 13
8
12
16
15
Concentration: 6.00 mM 10.00
3
2
36
5
12
4
µS
4
17
65.00
14
7
–1
0
4
8
12
16
20
Minutes
24
28
32
35
25585
Figure 2. Analysis of HAA5 in the presence of inorganic matrix ions
using a Dionex IonPac AS19 column at 15 ºC. HAA5 is poorly resolved
or coelutes with matrix ions as shown above (colored labels).
10.00
Concentration: 4.00 mM
0.3
0
2.5
5.0
7.5
10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0
Minutes
25584
Figure 1. Analysis of HAA5 in the presence of inorganic matrix ions
using a Dionex IonPac AS16 column at 30 ºC. HAA5 is poorly resolved
or coelutes with matrix ions as shown above (colored labels).
7
Peak Identification:
1. Fluoride
9. DBAA
2. Acetate
10. Nitrite
13
3. MCAA
11. Chlorate
4. Chlorite
12. Bromide
5. MBAA
13. Nitrate
6. Bromate
14. TCAA
7. Chloride
15. Carbonate
8. DCAA
4
Peak Identification:
1. Fluoride
11. Chlorate
2. Acetate
12. Carbonate
3. MCAA
13. Bromide
4. Chlorite
14. Nitrate
5. MBAA
15. TCAA
6. Bromate
7. Chloride
4
8. DCAA
9. DBAA
10. Nitrite
3
16.90
µS
4
10
µS
5
1,2
10
12
11 13
6
3
6
14
65.00
7
11
8
5
1,2
12
7
15
8
9
18.00
15
Concentration: 7.00 mM
9
14
0
0
Concentration: 7.00 mM
0
0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0
Minutes
4
8
12
16
20
24
28
Minutes
32
36
40
44 47
25587
25586
Figure 3. Analysis of HAA5 in the presence of inorganic matrix ions
using a Dionex IonPac AS20 column at 15 ºC. HAA5 is poorly resolved
or coelutes with matrix ions as shown above (colored labels).
Figure 4. Analysis of HAA5 in the presence of inorganic matrix ions
using a Dionex IonPac AS24 column at 15 ºC. HAA5 is poorly resolved
or coelutes with matrix ions as shown above (colored labels).
4
Matrix Elimination Ion Chromatography
Features
• Allows for large loop injection in the first dimension (4 mm column):
– Possible to inject a larger loop than the standard approach since the capacity and selectivity
of the analytical column in the first dimension dictates the recovery, and the analyte of
interest is analyzed in the second dimension
• Focus the ions of interest in a concentrator column after suppression in the first dimension:
– Hydroxide eluent suppressed to deionized (DI) water, thus providing an ideal environment
for focusing or concentrating the ions of interest
• Pursue analysis in the second dimension using a smaller column format with a smaller crosssectional area, leading to sensitivity enhancement that is proportional to the flow rate ratio:
– For example, for a 4 mm column operated in the first dimension at 1 mL/min and a 1 mm
column operated in the second dimension at 0.05 mL/min, the enhancement factor is 20
• Pursue analysis in the second dimension using a different chemistry:
– Enhanced selectivity
• Easy implementation on the Thermo Scientific Dionex ICS-3000 system
2.2
1
10
3
12
1st Dimension
17
75.001516
Waste
14
13
18
Peak Identification:
10. Phosphate
1. Fluoride
11. DCAA
2. Acetate
12. Nitrite
3. Chlorite
13. Benzoate
3. MCAA
14. DBAA
5. MBAA
15. Bromide
6. Bromate
7. Carbonate 16. Chlorate
17. Nitrate
8. Chloride
18. TCAA
9. Sulfate
6
7–9
2
0.1
5
Concentration: 20.00 mM
0
10
20
1st Dimension
Column (4 mm)
30
40
Minutes
50
60
Waste
CD 2
Injection Valve 1
CRD 2
External Water
Diverter Valve
Waste
Suppressor 2
Injection Valve 2
Waste
50.00
µS
Autosampler 1
EG
Large Loop
Load
Inject
65.00
11
4
2nd Dimension
Pump
CD 1
2nd Dimension Column (2 mm)
External Water
Waste
Suppressor 1
CRD 1
Pump
Concentrator
Column
(UTAC-ULP1)
Transfer to 2-D
Load Concentrator
EG
Waste
25589
Figure 6. Diagram of an MEIC 2-D system setup.
70 75
25588
Figure 5. Analysis of HAA5 in the presence of inorganic matrix ions
using a new prototype anion-exchange chemistry at 15 ºC. Excellent
resolution of all HAA5 was achieved in the presence of matrix ions.
5
Figure 7 shows analysis of HAA5 in reagent water (DI water). The top chromatogram shows the
analysis in the first dimension of the MEIC setup using a 4 mm Dionex IonPac AS19 column.
Excellent resolution of HAA5 can be inferred. The bottom chromatogram shows the analysis in the
second dimension of the MEIC setup using a 2 mm Dionex IonPac AS19 column.
In Figure 8, conditions are similar to Figure 7, except the sample is high-ionic-strength water
(HIW). Under these conditions, the matrix ions overwhelm the analytes, as shown in the top
chromatogram. The bottom chromatogram shows the analysis in the second dimension using the
MEIC setup. Performance is similar to what was shown in Figure 7B. The above example demonstrates the utility of the MEIC methodology for this work.
Columns:
Flow Rate:
Suppressor:
Current:
Inj. Volume:
Concentrator:
Temperature:
Samples:
1. Dionex IonPac AG19, AS19, 4 mm
2. Dionex IonPac AG19, AS19, 2 mm
1. 1.0 mL/min
2. 0.25 mL/min
1. Thermo Scientific™ Dionex™
ASRS™ ULTRA II 4 mm
2. Dionex ASRS ULTRA II 2 mm
1. 161 mA
2. 41 mA
1000 µL
UTAC-LP1
30 °C
1) MCAA
2) MBAA
3) DCAA
4) DBAA
5) TCAA
Time Gradient
(mM)
0
8
10
8
10.1 12
28
12
28.1 65
35
65
42
65
42.1 65
60
65
60.1 65
65
65
Gradient
(mM)
65
65
7
7
7
7
7
12
12
65
65
Columns:
1. Dionex IonPac AG19, AS19, 4 mm
2. Dionex IonPac AG19, AS19, 2 mm
1. 1.0 mL/min
2. 0.25 mL/min
Suppressor: 1. Dionex ASRS ULTRA II 4 mm
2. Dionex ASRS ULTRA II 2 mm
Current:
1. 161 mA
2. 41 mA
Loop:
1000 µL
Concentrator: UTAC-LP1
Oven:
30 °C
Samples:
1) MCAA
2) MBAA
3) DCAA
4) DBAA
5) TCAA
1800
Flow Rate:
Time
0
10
10.1
28
28.1
35
42
42.1
60
60.1
65
Gradient Gradient
(mM)
(mM)
8
65
8
65
12
7
12
7
65
7
65
7
65
7
65
12
65
12
65
65
65
65
SO4
A. First Dimension: 10 ppb HAA5 in HIW
0.35
A. First Dimension: 10 ppb HAA5 in RW
Cl
µS
3
µS
1
NO3
2
12.00
–0.05 EGC_1.Concentration: 8.00 mM
0
10
20
Minutes
B. Second Dimension: 10 ppb HAA5 in RW
µS
12.00
–200 EGC_1.Concentration: 8.00 mM
0
10
20
Minutes
5
4
1.2
30
2
–0.2
30
40
30
35
B. Second Dimension: 10 ppb HAA5 in HIW
1.2
65.00
65.00
3
µS
EGC_2.Concentration:
7.00 mM
5
4
–0.2
50
Minutes
PO4
CO3
35
3
EGC_2.Concentration: 12.00
7.00 mM
1
65.00
65.00
60
65
25590
Figure 7. MEIC analysis of HAA5 in reagent water (deionized water).
30
40
1
12.00
2
4
50
Minutes
5
60
65
25591
Figure 8. MEIC analysis of HAA5 in HIW (high ionic strength water).
Conclusion
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Wh ite Pa p er 7 04 2 3
An MEIC method was developed for the analysis of HAAs in drinking water matrices. HAA5
were detected at low ppb levels in reagent water and in high-ionic-strength water. Several column
chemistries were evaluated and a new high capacity stationary phase was found to optimize
separation selectivity and method performance. MEIC is a (potentially) simple and economical
alternative to current GC- and IC-MS techniques for routine monitoring of HAAs in drinking
water.

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