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Bromate Analysis Methods
Bromate: monitoring a potential carcinogen in drinking water
Bromate is a disinfection byproduct produced when ozone is used to disinfect drinking water that contains bromide and bromide-containing compounds. Because bromate is a potential human carcinogen, it is critical for the public water systems to monitor the presence of bromate before distributing the drinking water to households.
Many countries have established regulatory standards for bromate. Both the U.S. EPA and European Commission set a maximum contaminant level (MCL) of 10μg/L bromate in drinking water.
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Bromate analysis in drinking water
Bromate can be separated from other anions based on different ion chromatography (IC) column chemistries, then detected by a variety of techniques. The type of drinking water samples and the required detection limits determines which bromate analysis methods to use. When matrix elimination is not required, suppressed conductivity detection is the easiest method. Otherwise, several strategies can be used to increase signal to noise ratio by combining the elution conditions, column chemistries and detection methods to remove interference from other major anions. Multiple EPA and ISO methods developed for measurement of bromate in drinking water are illustrated below.
For more information
EPA Methods 300.0 and 300.1, and ISO 15061
U.S. EPA Method 300.0, written in 1993, uses ion chromatography with suppressed conductivity detection. The method is the original IC standard for inorganic anion analysis in different types of waters, such as ground, surface, drinking and wastewater. This method has Part A and B: Part A for the seven common anions and Part B for disinfection byproduct (DBP) anions including chlorate, chlorite, and bromate.
The method has a method detection limit (MDL) of 20µg/L for bromate in drinking water, which is not sensitive enough to meet the current regulatory standard. That is why EPA 300.1 was developed with modification of EPA 300.0 to achieve a MDL of 4µg/L for bromate in drinking water. Even today, EPA Method 300.1 is still the preferred method for low ionic strength drinking water, for which no matrix elimination is necessary.
The following advancements in IC have allowed current operation of EPA Method 300.1 to exceed the requirement for original EPA 300.1 and achieve better sensitivity:
- Improved column chemistries, smaller particle size, and higher capacity anion exchange columns
- Hydroxide eluents on a reagent-free ion chromatography (RFIC™) system
For more information on EPA 300.1
EPA Methods 317.0 and 326.0, and ISO 11206
For high ionic matrices of water, such as surface and ground water containing high concentration of chloride and sulfate, EPA Method 300.1 with only suppressed conductivity detection is not sufficiently sensitive to determine trace levels of bromate due to interference from chloride and sulfate. EPA methods 317.0, 326.0 and ISO 11206 use IC combining suppressed conductivity with a post column reaction (PCR) (addition of potassium iodide) and visible detection for triiodide to determine low concentrations of bromate in high ionic strength matrices.
These methods achieve an MDL of 0.04ug/L for bromate. ISO 11206 differs from EPA methods 317.0 and 326.0 by changing the eluent to sulfuric acid to eliminate the interference of chloride but limits the choices of commercially available columns. It should be mentioned that anions such, as bromide, cannot be determined in EPA 317 and 326, which is a major limitation of these methods.
The difference between EPA 317.0 and 326.0 lies in the reagent added in the postcolumn reaction and detection. EPA 317 has addition of O-dianisidine before visible light detection while EPA 326.0 has addition of potassium iodide before UV detection.
EPA Method 302.0
EPA 302.0 uses two-dimensional IC (2D-IC) with suppressed conductivity detection. While EPA 300.1 is only used for low ionic strength water analysis, EPA methods 317.0 and 326.0 are used to remove the interferences of the high ionic strength matrix. Although, the detection methods are selective to only bromate, the high ionic strength matrix may overload the column capacity, resulting in peak broadening and signal loss especially for bromate analysis in natural mineral water.
In EPA Method 302.0, bromate is partially resolved from matrix ions on the first dimension column (4mm internal diameter or i.d.); the fraction containing bromate is concentrated on a concentrator column before transfer to the second dimension column, which has a different selectivity chemistry, while the matrix ions are diverted to waste. The second column typically has a smaller i.d. of 2mm or even 0.4mm (capillary). The bromate, hidden under the major anions and undetectable in the first dimension, is fully resolved in the second column.
With this 2D-IC technique, a MDL of 0.036µg/L for bromate is achieved for high ionic strength water samples. As a result, 2D-IC is a powerful tool for the analysis of ultra-trace level of bromate needed to meet the regulatory requirements.
For more information
EPA Method 557
EPA 557 is a method for the analysis of nine haloacetic acids, bromate and dalapon (a selective herbicide) in drinking water using ion chromatography coupled with electrospray mass spectrometry. Although the method permits flexibility in use of columns, eluent conditions, and eluent suppression techniques, the sample must be directly injected without filtering or pretreatment by the use of solid phase extraction. Using this sensitive IC-MS method, a MDL of 0.015 to 0.2µg/L can be achieved when analytes are fortified into reagent water.
For more information on EPA Method 557
Selection of bromate analysis methods
Regulatory agencies have developed multiple ion chromatography (IC) methods for bromate analysis to suit different needs in sensitivity and instrumentation. The following table of application notes will help you select the method that’s best for your requirements. Choose between:
- Gradient, isocratic, postcolumn (ODA or KI) or 2D-IC methods
- Thermo Scientific™ Dionex™ IonPac™ Hydroxide columns:
- Thermo Scientific™ Dionex™ IonPac™ Carbonate columns:
In most cases, the hydroxide or carbonate eluent is generated electrolytically on Reagent-Free™ IC (RFIC™) systems to improve reproducibility and simplify analysis.
Methods using Dionex IonPac AS19 Hydroxide Columns
Improved sensitivity
Application note | Dionex IonPac column | Eluent | Employs | Application note demonstrates |
|---|---|---|---|---|
| AN 167 | Electrolytic hydroxide generation | Gradient method with suppressed conductivity detection | Trace Concentrations of Oxyhalides and Bromide in Municipal and Bottled Waters
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| AN 154 | Electrolytic hydroxide generation | Isocratic method with suppressed conductivity detection | Inorganic Anions in Environmental Waters
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| AN 168 | Electrolytic hydroxide generation | Postcolumn derivatization using o-dianisidine (ODA) to enhance detection | Trace Bromide in Drinking Water Using RFIC and Postcolumn Addition of o-Dianisidine
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| AN 171 | Electrolytic hydroxide generation | Postcolumn derivatization using potassium iodide (KI) to enhance detection |
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| AN 187 | Dionex IonPac AS19 (4mm) and AS24 (2mm) | Electrolytic hydroxide generation | 2D-IC with suppressed conductivity | Sub-μg/L Bromate in Municipal and Natural Mineral Waters
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Methods using Dionex IonPac AS23 Carbonate Column
Higher capacity carbonate column changes retention of carbonate for easier bromate analysis
Application Note | Dionex IonPac Column | Eluent | Employs | Application Note Demonstrates |
|---|---|---|---|---|
| AN 184 | Compares Dionex IonPac AS23 and AS19 | Electrolyic | Conductivity detection | Trace Chlorite, Bromate, and Chlorate in Bottled Natural Mineral Waters
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| AN 208 | Electrolytic carbonate/ | CRD-300 to reduce background noise | Bromate in Bottled Mineral Water Using the CRD 300 Carbonate Removal Device
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Methods using Dionex IonPac AS9-HC Carbonate Column
Traditional column in EPA methods
Application Note | Dionex IonPac Column | Eluent | Employs | Application Note Demonstrates |
|---|---|---|---|---|
| AN 149 | carbonate | Postcolumn derivatization using potassium iodide (KI) to enhance detection | Sub-μg/L Bromate Analysis in Drinking Water Using an On-Line-Generated Postcolumn Reagent
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| AN 136 | carbonate | Postcolumn derivatization using o-dianisidine (ODA) to enhance detection | Trace Bromate Analysis in Drinking Water With Addition of a Postcolumn Reagent
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| AN 81 | carbonate | Direct Injection with suppressed conductivity detection | Trace Level Bromide Analysis by Direct Injection
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