Bromate—monitoring a potential carcinogen in drinking water

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.

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.

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

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.

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.

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:

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

Dionex IonPac AS19

Electrolytic hydroxide generation

Gradient method with suppressed conductivity detection

  Trace Concentrations of Oxyhalides and Bromide in Municipal and Bottled Waters

  • Introduces the Dionex IonPac AS19 column designed for use with hydroxide eluent
  • Improves sensitivity compared to carbonate eluent
  AN 154

Dionex IonPac AS19

Electrolytic hydroxide generation

Isocratic method with suppressed conductivity detection

  Inorganic Anions in Environmental Waters

  • Update to AN 167 demonstrates the advantages of the Dionex IonPac AS19 columns using an isocratic hydroxide eluent method
  • Provides a good, quick method
  • Does not determine all the inorganic anions in a single injection
  AN 168

Dionex IonPac AS19

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

  • Trace bromate analysis using the Dionex IonPac AS19 hydroxide column and ODA postcolumn dervatization with visible detection
  • Provides sub-μg/L quantitation
  • Meets U.S. EPA Method 317.0 with a bromate MDL of 0.1μg/L and a practical quantitation limit (PQL) of 0.5μg/L
  • This method replaces Dionex IonPac AS9-HC carbonate eluent column method in AN 136
  AN 171

Dionex IonPac AS19

Electrolytic hydroxide generation

Postcolumn derivatization using potassium iodide (KI) to enhance detection

  Trace Bromate in Drinking Water Using RFIC and Postcolumn Addition of an Acidified On-Line Generated Reagent

  • Trace bromate analysis using the Dionex IonPac AS19 hydroxide column and KI postcolumn dervatization with visible detection
  • Provides sub-μg/L quantitation
  • Meets U.S. EPA Method 326.0 with a bromate MDL of 0.1μg/L and a practical quantitation limit (PQL) of 0.5μg/L
  • This method replaces Dionex IonPac AS9-HC carbonate eluent column as shown in AN 149
  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

  • These samples can have low bromate concentrations in high-ionic-strength matrices with potential interferences and loss of sensitivity
  • 2D-IC provides preconcentration in the first dimension
  • Does not require postcolumn derivatization
  • Results are comparable and lower than ODA and KI postcolumn derivatization methods using visible detection

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
hydroxide
generation for
AS19. Electrolytic carbonate/ bicarbonate generation for
AS23

Conductivity detection

  Trace Chlorite, Bromate, and Chlorate in Bottled Natural Mineral Waters

  • Compares linearity, method detection limits, precisions, and recovery of Dionex IonPac AS19 hydroxide and AS23 carbonate columns for three European mineral waters
  • Both columns provided the required sensitivity to meet 10μg/L bromate currently required by most regulatory agencies
  • Dionex IonPac AS19 hydroxide column provides higher sensitivity and is recommended for compliance with EU Directive 2003/40/EC, which permits a maximum of 3μg/L bromate in mineral waters
  AN 208

Dionex IonPac AS23

Electrolytic carbonate/
bicarbonate generation

CRD-300 to reduce background noise

  Bromate in Bottled Mineral Water Using the CRD 300 Carbonate Removal Device

  • Demonstrates higher capacity Dionex IonPac AS23 carbonate column with CRD achieves less than 1 ppb MDL bromate
  • Replaces the original Dionex IonPac AS9-HC carbonate column
  • When higher sensitivity is required, use the AS19 hydroxide column

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

Dionex IonPac AS9-HC

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

  • Employs postcolumn derivatization techniques in U.S. EPA Method 326.0
  • Uses Dionex IonPac AS9-HC column and suppression technology for conductivity detection of oxyhalides
  • KI method improves sensitivity by more than a factor of 10
  AN 136

  Dionex IonPac AS9-HC

carbonate

Postcolumn derivatization using o-dianisidine (ODA) to enhance detection

  Trace Bromate Analysis in Drinking Water With Addition of a Postcolumn Reagent

  • Employs post-column derivatization techniques in U.S. EPA Methods 317.0
  • Demonstrates our Dionex IonPac AS9-HC column and suppression technology for conductivity detection of oxyhalides
  • Employs ODA o enhance visible absorbance detection for enhanced determination of bromate
  AN 81

Dionex IonPac AS9-HC

carbonate

Direct Injection with suppressed conductivity detection

  Trace Level Bromide Analysis by Direct Injection

  • U.S. EPA Method 300.0(B) and 300.1(B) uses the Dionex IonPac AS9-SC and AS9-HC columns, respectively, along with suppressed conductivity detection for bromate, chlorite, and chlorate determinations in drinking water
  • Easily meets 10μg/L regulatory requirement
  • Recommend using the newer, high-capacity AS23 Carbonate Eluent Anion-Exchange column for determination of oxyhalides and inorganic anions, such as trace bromate, in ozonated drinking water
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