4110 DETERMINATION OF ANIONS BY ION CHROMATOGRAPHY*

4110 A. Introduction

Determination of the common anions such as bromide, chloride, fluoride, nitrate, nitrite, phosphate, and sulfate often is

desirable to characterize a water and/or to assess the need for

specific treatment. More recently, the need to measure the concentration of the disinfection by-products chlorite, chlorate, and

bromate has arisen. Although conventional colorimetric, electrometric, or titrimetric methods are available for determining individual anions, ion chromatography provides a single instrumental technique that may be used for their rapid, sequential

measurement. Ion chromatography eliminates the need to use

hazardous reagents and it effectively distinguishes among the

halides (Br, Cl, and F) and the oxyhalides (ClO2

, ClO3,

and BrO3

), and the oxy-ions (PO43, SO42, NO2, and

NO3

).

Methods 4110B and 4110C are applicable, after filtration to

remove particles larger than 0.45 m, to surface, ground, and

wastewaters as well as drinking water. Some industrial process

waters, such as boiler water and cooling water, also may be

analyzed by this method. Method 4110D is applicable to untreated and finished drinking water as well as drinking water at

various stages of treatment.

4110 B. Ion Chromatography with Chemical Suppression of Eluent Conductivity

1. General Discussion

a. Principle: A water sample is injected into a stream of eluent

and passed through a series of ion exchangers. The anions of

interest are separated on the basis of their relative affinities for a

low-capacity, strongly basic anion exchanger (guard and analytical columns). The separated anions are directed through a suppressor device that provides continuous suppression of eluent

conductivity and enhances analyte response. In the suppressor

the separated anions are converted to their highly conductive

acid forms while the conductivity of the eluent is greatly decreased. The separated anions in their acid forms are measured

by conductivity. They are identified on the basis of retention time

as compared to standards. Quantitation is by measurement of

peak area or peak height.

b. Interferences: Any substance that has a retention time

coinciding with that of any anion to be determined and produces

a detector response will interfere. Low-molecular-weight organic

acids, bromate, and chlorite may interfere with the determination

of chloride and fluoride. A high concentration of any one ion also

interferes with the resolution, and sometimes retention, of others.

Sample dilution or gradient elution overcomes many interferences. To resolve uncertainties of identification or quantitation

use the method of known additions. Spurious peaks may result

from contaminants in reagent water, glassware, or sample processing apparatus. Modifications such as preconcentration of

samples, gradient elution, or reinjection of portions of the eluted

sample may alleviate some interferences but require individual

validation for precision and bias and are beyond the scope of this

method.

c. Method detection level: The detection level of an anion is a

function of sample size. Table 4110:I presents detection levels

obtained for reagent water with a 25-L sample loop. Detection

levels in natural waters may be substantially higher because of

the presence of high levels of some of the anions.

d. Limitations: Exercise caution if this method is used to

determine F in unknown matrices. Two problems are commonly encountered: first, with some column/eluent combinations the fluoride peak elutes very close to the baseline

depression caused by the elution of water, the so-called “water dip”. This may cause difficulty in quantitating samples

with low fluoride concentrations; second, the simple organic

acids (formic, acetate) elute close to fluoride and may interfere. Determine precision and bias before analyzing samples.

If fluoride is to be determined, preferably select a column/

eluent combination that resolves water, fluoride, and simple

organic acids.

Because of the utilization of nitrate, nitrite, and phosphate as

nutrients by some species of bacteria, store samples at 4°C and

analyze within 48 h. Disinfected samples to be analyzed for

nitrate may be held for up to 14 d because all nitrite will already

be converted to nitrate. Store samples to be analyzed for sulfate

* Approved by Standard Methods Committee, 2000. Editorial revisions, 2011.

Joint Task Group: 21st Edition—Richard Mosher (chair), Bruce A. Hale, Daniel

P. Hautman, Peter E. Jackson, S. V. Karmarkar, James Krol, James W. O’Dell,

Roy-Keith Smith.

TABLE 4110:I. DETECTION LEVEL FOR ANIONS IN REAGENT WATER.*

Anion

MDL

g/L

Fluoride 2.0

Chloride 4.0

Nitrite-N 3.7

Bromide 14

Nitrate-N 2.7

Orthophosphate-P 14

Sulfate 18

* See Figure 4110:1 for experimental conditions.

1
at 4°C and analyze within 28 d. The other analytes do not require

cold storage. Complete analysis within 28 d.

2. Apparatus

a. Ion chromatograph, including an injection valve, a sample

loop, guard column, analytical column, suppressor device, a

temperature-compensated small-volume conductivity cell and

detector (6 L or less), and an electronic peak integrator or

chromatography data acquisition system. Use an ion chromatograph capable of delivering 2 to 5 mL eluent/min at a pressure of

5600 to 28 000 kPa (800 to 4000 psi).

b. Analytical column: Any commercially available anionexchange column capable of resolving fluoride, bromide, chloride, nitrate, nitrite, phosphate, and sulfate is acceptable.*

c. Guard column, identical to separator column† to protect

analytical column from fouling by particulates or organics.

d. Suppressor device:‡ Place this ion-exchange-based device

between column and detector to reduce background conductivity

of the eluent and enhance conductivity of the target analytes.

Several such devices with different operational principles are

available commercially; any that provides the required sensitivity and baseline stability may be used.

3. Reagents

a. Reagent water free from interferences at the method detection level of each constituent with 18 megohm resistivity and

containing no particles larger than 0.2 m. See Section 1080.

b. Eluent solution, appropriate to column used to resolve target

anions. The eluent used to produce the chromatogram in Figure

4110:1 was sodium bicarbonate-sodium carbonate, 1.7 mM

NaHCO3

, 1.8 mM Na2CO3. Dissolve 0.5712 g NaHCO3 and

0.7632 g Na2CO3 in water and dilute to 4 L. Degas eluent before

use either by vacuum filtration to simultaneously remove particles greater than 0.45 m or by purging with helium for 10 min.

c. Regenerant solution: Required with some types of suppressors. See manufacturer’s recommendations.

d. Standard anion solutions, 1000 mg/L: Purchase stock standard solutions as certified solutions or prepare from ACS reagent-grade salts. Prepare standard anion solutions by weighing

the indicated amount of salt (Table 4110:II), dried to a constant

weight at 105°C, and diluting to 100 mL with distilled/deionized

water. Store in plastic bottles at 4°C. These solutions are stable

for at least 6 months except for the nitrite and phosphate standards, which should be discarded after 1 month. Prepare most

dilute working standards monthly, nitrite and phosphate, daily.

4. Procedure

a. System equilibration: Turn on ion chromatograph and adjust

eluent flow rate to manufacturer’s recommendations for the

column/eluent combination being used. A representative chromatogram is presented in Figure 4110:1. Adjust detector to

desired setting (usually 10 to 30 S) and let system come to

equilibrium (15 to 20 min). A stable base line indicates equilibrium conditions. Adjust detector offset to zero out eluent conductivity. If regenerant is used with the suppressor, adjust flow

rate to manufacturer’s specifications.

b. Calibration: Inject standards containing a single anion or a

mixture and determine approximate retention times. Observed

times vary with conditions. If the analytical column and eluent

mentioned in 4110B.2b and 3b, respectively, are used, retention

always is in the order F, Cl, NO2

, Br, NO3, HPO42, and

SO4

2. Inject at least three different concentrations for each

anion to be measured. Use concentrations that will bracket the

expected analyte concentrations in samples. Construct a calibration curve by plotting peak height or area versus concentration

using appropriate software. Verify calibration curves with a

mid-range check standard from a source independent of that of

the calibration standards. Check validity of existing calibration

curves daily with a mid-range calibration standard. Results

* Dionex P/N 37041, Lachat P/N 28084, Waters P/N 26765, or equivalent.

† Dionex P/N 37042, Lachat P/N 28085, or equivalent.

‡ Dionex P/N 46081, Lachat P/N 28097, Alltech P/N 535101, or equivalent.

TABLE 4110:II. STOCK STANDARD PREPARATIONS

Anion Salt

Amount

g/100 mL

Fluoride NaF 0.2210

Chloride NaCl 0.1649

Bromide NaBr 0.1288

Nitrate-N* NaNO3 0.6068

Nitrite-N* NaNO2 0.4926

Phosphate-P KH2PO4 0.4394

Sulfate K2SO4 0.1814

* Do not oven-dry. Dry to constant weight in a dessicator.

Figure 4110:1. Typical inorganic anion separation. Eluent: 1.7 mM

NaHCO3, 1.8 mM NaCO3; sample loop: 25 L; flow rate:

2.0 mL/min; column: Dionex AG4A-SC plus AS4A-SC.

Anion

Conc

mg/L

1. Fluoride 2.0

2. Chloride 3.0

3. Nitrite 5.0

4. Bromide 10.0

5. Nitrate 10.0

6. Orthophosphate 15.0

7. Sulfate 15.0

ION CHROMATOGRAPHY (4110)/Ion Chromatography with Chemical Suppression of Eluent Conductivity

2
should be within 10% of original curve at mid-range. Recalibrate

whenever the detector setting, eluent, or regenerant is changed. To

minimize the effect of the “water dip”§ on F analysis, analyze standards that bracket the expected result or eliminate the water dip by

diluting the sample with eluent or by adding concentrated eluent to the

sample to give the same concentration as in the eluent. If sample

adjustments are made, adjust standards and blanks identically.

If linearity is established (r 0.99) over the calibration range,

the average response factor is acceptable. Record peak height or

area for calculation of the response factor, RF. HPO4

2 is

nonlinear below 1.0 mg/L.

c. Sample analysis: If sample is collected with an autosampler that

does not automatically filter samples, remove particulates by filtering

through a prewashed 0.45-m (or smaller) pore membrane. With either

manual or automated injection, flush loop with several volumes of

sample. Take care to prevent carryover of analytes from samples of

high concentration. After last peak has appeared and detector signal has

returned to base line, another sample can be injected.

d. Solid matrices: Soluble forms of the target anions may be determined in solid matrices (soils, sludges) after extraction and filtration of

the extract. A slurry of the solid to be extracted is prepared with either

reagent water or eluent and is either shaken or sonicated. (A representative standardized method for such extractions is available.1

) Document the precision of the extraction process and the analyte recovery

achieved by analyzing duplicate laboratory-fortified matrices for each

distinct matrix.

5. Calculations

Determine the concentration of each anion, in milligrams per

liter, by referring to the appropriate calibration curve. Alternatively,

when the response is shown to be linear, use the following equation:

C  H  RF  D

where:

C mg anion/L,

H peak height or area,

RF response factor concentration of standard/height (or area)

of standard, and

D dilution factor.

6. Quality Control

The QC practices considered to be an integral part of each method

are summarized in Table 4020:I. Preferably check recovery daily at

reporting level using a reporting-level standard. Recovery should be

between 75 and 125%. Alternate analysis of mid-range and high-range

check standards after each 10 samples. Recovery should be between 90

and 110%. If the results are to be used for environmental compliance

monitoring, document precision and accuracy of the method by the

analysis of four replicates of a mid-range calibration standard and

calculation of the average percent recovery, and the standard deviation

of the recoveries, for each analyte. Additional QC may be required for

regulatory purposes.

7. Precision and Bias

Multilaboratory data from a joint validation study with EPA and

ASTM using older columns and hardware can be found in the 20th

Edition of Standard Methods. Table 4110:III shows single-laboratory recoveries for laboratory-fortified blanks (LFB) and known

additions to a variety of raw waters and finished drinking waters

obtained with columns and equipment described herein.

8. Reference

1. AMERICAN SOCIETY FOR TESTING AND MATERIALS. 1992. Method

D3987. Annual Book of ASTM Standards, Vol. 11.01 Water. American Soc. Testing & Materials, Philadelphia, Pa.

9. Bibliography

SMALL, H., T. STEVENS & W. BAUMAN. 1975. Novel ion exchange chromatographic method using conductimetric detection. Anal. Chem. 47:1801.

JENKE, D. 1981. Anion peak migration in ion chromatography. Anal.

Chem. 53:1536.

BYNUM, M.I., S. TYREE & W. WEISER. 1981. Effect of major ions on the

determination of trace ions by ion chromatography. Anal. Chem.

53:1935.

WEISS, J. 1986. Handbook of Ion Chromatography. E.L. Johnson, ed.

Dionex Corp., Sunnyvale, Calif.

PFAFF, J.D., C.A. BROCKHOFF & J.W. O’DELL. 1994. The Determination

of Inorganic Anions in Water by Ion Chromatography. Method

300.0A, U.S. Environmental Protection Agency, Environmental

Monitoring Systems Lab., Cincinnati, Ohio.

PFAFF, J.D., D.F. HAUTMAN & D.J. MUNCH. 1997. Determination of Inorganic Anions in Drinking Water by Ion Chromatography. Method

300.1, U.S. Environmental Protection Agency, National Exposure Research Lab., Off. Research & Development, Cincinnati, Ohio.

§ Water dip occurs because water conductivity in sample is less than eluent

conductivity (eluent is diluted by water).

TABLE 4110:III. SINGLE-LABORATORY PRECISION (ONE STANDARD DEVIATION) AND BIAS DATA FOR 30 SETS OF SAMPLES OVER A 2-MONTH-PERIOD

Element

LFB

Concentration

mg/L

LFB Recovery and

Precision

%

Known Addition

Concentration

mg/L

Known Addition

Recovery and

Precision

%

Chloride 25 104  4.5 25 107  10

Nitrite as N 1 97  4 1 103  7

Bromide 0.02 101  8 0.1 to 0.5 106  10

Bromide 0.3 102  3— —

Nitrate as N 2.5 106  2.6 2.5 113  5

Orthophospate-P 10 101  4 10 102  4

Sulfate 50 105  4 50 111  6

ION CHROMATOGRAPHY (4110)/Ion Chromatography with Chemical Suppression of Eluent Conductivity

3
4110 C. Single-Column Ion Chromatography with Direct Conductivity Detection

1. General Discussion

a. Principle: An aqueous sample is injected into an ion chromatograph consisting of an injector port, analytical column, and

conductivity detector. The sample merges with the eluent stream

and is pumped through the analytical column where the anions

are separated on the basis of their affinity for the active sites of

the column packing material. Direct conductivity detection without chemical suppression is used to determine concentrations.

b. Interferences: See 4110B.1b. Note that HCO3

 elutes between F and Cl with this method. See Figure 4110:2.

Because method sensitivity is high, take care to avoid contamination by reagent water and equipment.

c. Method detection level: The detection level of an anion is a

function of sample volume injected and the signal-to-noise ratio

of the detector electronics. Generally, minimum detectable concentrations are about 0.02 to 0.12 mg/L (20 to 120 g/L) for the

anions with an injection volume of 100 L (Table 4110:IV).

Larger injection volumes can reduce detection levels. However,

coelution is a possible problem with large injection volumes.

Determine method detection level for each anion of interest

under the conditions used to produce reportable data.

2. Apparatus

a. Ion chromatograph, complete with all required accessories

including syringes, analytical columns, detector, and a data system. Required accessories are listed below.

b. Guard column, placed before analytical column to protect it

from fouling by particulates or organic constituents.*

c. Analytical column, packed with low-capacity anionexchange resin capable of resolving fluoride, chloride, nitrite,

bromide, nitrate, orthophosphate, and sulfate.†

d. Conductivity detector, flow-through, with integral heatexchange unit allowing direct temperature control and with

separate working and reference electrodes.

e. Pump, constant flow between 0.5 and 5.0 mL/min at a

pressure of 5600 to 28 000 kPa (800 to 4000 psi).

f. Data system, preferably computer with software capable of

acquiring and processing chromatographic data. An integrator

also may be used.

g. Sample injector: Either an automatic sample processor or a

manual injector. The automatic device must be able to inject a

minimum sample volume of 10 L.

3. Reagents

a. Reagent water: See 4110B.3a.

b. Borate/gluconate concentrate: Place approximately 25 g of

a strong cation-exchange resin‡ in the hydrogen form in a 60-mL

plastic syringe fitted with a 0.45-m filter. Wash resin with five

20-mL portions of deionized water. Dissolve 9.06 g sodium

gluconate in 20 mL deionized water. Transfer this solution to the

60-mL syringe and slowly pass through the syringe into a 1-L

volumetric flask. Wash resin with five 20-mL portions deionized

water, adding washings to flask. Discard syringe and resin.

Alternatively use commercially available 50% gluconic acid.

This usually comes as a brown solution that when diluted gives

a yellow tint to the eluent that may affect long-term performance.

Remove color by passing the 50% gluconic acid through a C18

cartridge (5 mL/cartridge). Use 13.2 mL of the 50% gluconic

acid for the eluent concentrate.

Adjust volume in the 1-L volumetric flask to approximately

500 mL with deionized water and add a stirring bar. Add 7.2 g

lithium hydroxide monohydrate and 25.5 g boric acid. Stir until

all reagents are dissolved. Add 94 mL 95% glycerol and mix

well. Remove stirring bar and dilute to 1 L. This may be stored

at room temperature for 6 months or at 4°C for 1 year (warm to

ambient before use). Discard if evidence of microbial growth

appears.

c. Eluent solution, 8.25 mM borate, 0.83 mM gluconate, 12%

(v/v) acetonitrile: Combine 20 mL borate/gluconate concentrate

and 120 mL HPLC-grade acetonitrile, and dilute to 1 L with

reagent water. Vacuum filter through a 0.45-m- (or smaller)

pore size membrane before use.

* Waters P/N WAT010551, or equivalent.

† Waters P/N WAT0026765, or equivalent.

‡ Bio-Rad AG-50W-X12, or equivalent.

Figure 4110:2. Typical inorganic anion separation. Eluent: borate/gluconate containing 12% acetonitrile; flow rate: 1.0 mL/min;

injection volume: 100 L; column: Waters IC Pak A/HR;

background conductivity: 240 S.

Anion

Conc

mg/L

1. Fluoride 1.0

2. Bicarbonate —*

3. Chloride 2.0

4. Nitrite 4.0

5. Bromide 4.0

6. Nitrate 4.0

7. Orthophosphate 6.0

8. Sulfate 4.0

* Not quantified.

ION CHROMATOGRAPHY (4110)/Single-Column Ion Chromatography with Direct Conductivity Detection

4
d. Stock standard solutions: See 4110B.3d.

4. Procedure

a. System equilibration: Set up ion chromatograph in accordance with the manufacturer’s directions. Install guard and separator columns and begin pumping eluent until a stable base line

is achieved. The background conductivity of the eluent solution

is 240  20 S.

b. Calibration: Determine retention time for each anion by

injecting a standard solution containing only the anion of interest

and noting the time required for a peak to appear. Retention

times may vary with operating conditions and with anion concentration. The order of elution is shown in Figure 4110:2.

Construct a calibration curve by injecting prepared standards

including each anion of interest. Use at least three concentrations

plus a blank. Bracket the range of concentrations expected for

samples. Construct calibration curve by plotting either peak

height or peak area versus concentration. If a data system is

being used, make a hard copy of the calibration curve available.

After generating calibration curves, verify them with a midrange check standard from a source independent of that of the

calibration standards. Verify working calibration curves daily by

injecting a mid-range standard. Agreement should be within

10%. Also verify curves with each batch of eluent. If linearity is

established over the calibration range, the average response

factor is acceptable. Record peak height or area for calculation of

the response factor (RF).

c. Sample analysis: Inject sufficient sample (about two to three

times the loop volume) to ensure that sample loop is properly

flushed. Let all peaks elute before injecting another sample.

Compare response in peak height or peak area and retention time

to values obtained in calibration.

5. Calculation

See 4110B.5.

6. Quality Control

See 4110B.6.

7. Precision and Bias

Precision and bias data are given in Table 4110:V. These data

were produced in 1988. NOTE: The columns and other hardware

discussed herein were not available when the study was conducted. The advances in technology that have occurred since that

time should be considered when using these data.

8. Reference

1. GLASER, J., D. FOERST, G. MCKEE, S. QUAVE & W. BUDDE. 1981.

Trace analyses for wastewater. Environ. Sci. Technol. 15:1426.

4110 D. Ion Chromatographic Determination of Oxyhalides and Bromide

1. General Discussion

a. Principle: See 4110B.1a.

b. Interferences: The need to quantitate low levels of disinfection by-products and their precursors in the presence of much

higher levels of the common anions poses an analytical problem.

Any ionic material that coelutes with a target analyte will interfere with the determination of that analyte. Bromate has been

shown to be subject to positive interferences in some matrices.

The interference is noticeable usually as a flattened peak. It often

can be eliminated by passing the sample through an H cartridge.* This problem may be addressed by selection of a different column/eluent combination or by dilution of the eluent,

which will increase retention times and spread the chromatogram. Additionally, chloride or a non-target analyte present in

* Dionex PN 039596.

TABLE 4110:IV. DETECTION LEVEL FOR ANIONS IN REAGENT WATER

Anion

MDL

g/L

Fluoride 40

Chloride 20

Nitrite-N 15

Bromide 75

Nitrate-N 17

Orthophosphate-P 40

Sulfate 75

TABLE 4110:V. SINGLE-COLUMN CHROMATOGRAPHY SINGLE-OPERATOR

PRECISION AND BIAS*

Anion

Sample

Type†

Amount

Added

mg/L

Mean

Recovery

%

SD

mg/L

Cl RW 16 105 1.6

DW 16 98 1.9

NO2

-N RW 4 101 0.10

DW 4 101 0.43

Br RW 16 104 0.75

DW 16 98 2.3

NO3

-N RW 8 103 0.75

DW 8 87 1.9

PO4

3-P RW 16 113 0.92

DW 16 110 1.6

SO4

2 RW 32 101 0.42

DW 32 94 4.8

* Data provided by EPA/EMSL (NERL), Cincinnati, OH 45268. Seven replicates

were analyzed for each anion and sample type.

† RWreagent water; DWdrinking water.

ION CHROMATOGRAPHY (4110)/Ion Chromatographic Determination of Oxyhalides and Bromide

5
unusually high concentration may overlap with a target analyte

sufficiently to cause problems in quantitation or may cause

retention-time shifts. Dilution of the sample may resolve this

problem. Care must be exercised to avoid carryover from a

sample of high concentration to the subsequent sample. Method

interferences also may be caused by contamination of reagents,

reagent water, glassware, syringes, and other equipment used to

process samples.

c. Method detection level: The detection levels for bromide,

bromate, chlorate, and chlorite in reagent water free of interfering anions are shown in Table 4110:VI.

d. Sample collection and storage: Collect samples to be analyzed for chlorite in opaque containers and store them at 4°C. All

of the oxyhalides, including chlorite, require preservation with

50 mg/L ethylenediamine (EDA).

Residual chlorine dioxide present in the sample will result in

the formation of additional chlorite between the times of sampling and analysis. If chlorine dioxide is suspected to be present,

purge sample with an inert gas such as nitrogen, helium, or argon

for approximately 4 min at time of collection, before adding

ethylenediamine preservative.

2. Apparatus

a. Ion chromatograph: See 4110B.2a.

b. Analytical column: Any commercially available column†

capable of resolving the oxyhalides chlorite, chlorate, and bromate, from the other anions that may be present in drinking

water, including fluoride, chloride, nitrite, nitrate, phosphate, and

sulfate, is acceptable.

c. Guard column: This is a short column‡ packed with the

same stationary phase as the analytical column, used to protect

the analytical column from particulates and organics.

d. Pretreatment cartridge for removal of interferences such as

cations and carbonates.

e. Suppressor device: See 4110B.2d.

3. Reagents

a. Reagent water: See 4110B.3a.

b. Eluent solution, appropriate to the column used to resolve

the target anions. Figure 4110:3 was obtained by using 9 mM

sodium carbonate prepared as follows: Dissolve 1.91 g sodium

carbonate in reagent water and dilute to 2 L. Vacuum filter eluent

through a 0.45-m or smaller filter to remove particles that could

ultimately plug the column. This also degasses the eluent.

c. Regenerant solution (required with some suppressors): See

manufacturers’ recommendations.

d. Standard anion solutions, 1000 mg/L: Purchase stock standard solutions as certified solutions or prepare from ACS reagent-grade potassium or sodium salts. See Table 4110:VII.

e. Ethylenediamine (EDA) preservation solution, 100 mg/mL:

Dilute 2.8 mL EDA (99%) to 25 mL with reagent water. This

solution is stable for 1 month.

4. Procedure

a. System equilibration: See 4110B.4a.

b. Calibration: Prepare a series of calibration standards by

diluting the stock standards appropriately to bracket the expected

analyte concentrations in the samples. If the analytical column

and eluent described in 4110D.2b and 3b are used, retention is in

† Dionex P/N 51786, or equivalent.

‡ Dionex P/N 51791, or equivalent.

TABLE 4110:VI. DETECTION LEVEL FOR ANIONS IN REAGENT WATER*

Anion

MDL

g/L

Bromide 0.98

Bromate 1.32

Chlorate 2.55

Chlorite 1.44

* Determined under the following operating conditions: Eluent: 9 mM Na2CO3;

flow rate: 1.25 mL/min; columns: Dionex AG9-HC and AS9-HC, 4 mm; sample

loop: 200 L; suppressor: Dionex ASRS-I, 300 mA in external water mode;

detector: Dionex CD20.

SOURCE: PFAFF, J.D., D.F. HAUTMAN & D.J. MUNCH. 1997. Determination of

Inorganic Ions in Drinking Water by Ion Chromatography. EPA Method 300.1,

U.S. Environmental Protection Agency, National Exposure Research Lab., Off.

Research & Development, Cincinnati, Ohio.

Figure 4110:3. Typical separation in a simulated drinking water sample.

Eluent: 9 mM Na2CO3; flow rate: 1.0 mL/min; columns:

Dionex AG9-HC and AS9-HC, 4 mm; sample loop: 200 L;

suppressor: Dionex ASRS, 100 mA in external water mode

at 10 mL/min; detector: Dionex CD20 stabilized at 35°C.

Anion

Conc

mg/L

1. Fluoride 1.0

2. Chlorite 0.01

3. Bromate 0.005

4. Chloride 50

5. Nitrite 0.1

6. Bromide 0.01

7. Chlorate 0.01

8. Nitrate 10

9. Phosphate 0.1

10. Sulfate 50

ION CHROMATOGRAPHY (4110)/Ion Chromatographic Determination of Oxyhalides and Bromide

6
the order chlorite, bromate, bromide, and chlorate (See Figure

4110:3). Use at least three concentrations for each anion and

construct calibration curves by plotting peak height or area

(recommended) against concentration using appropriate software. If linearity is established (r 0.99) the average response

factor may be used in place of a calibration curve. Verify

calibration curves with a mid-range standard from a source

independent of that of the calibration standards. Check validity

of existing calibration curves daily with a mid-range calibration

standard. Agreement should be within 10% at mid-range. Also

verify existing calibration curves whenever eluent or regenerant

is changed. A change in detector setting usually will require

recalibration. Samples preserved with EDA may show a bias

attributable to the presence of this compound. If such a bias is

suspected, add EDA to each calibration standard.

c. Sample analysis: See 4110B.4c.

5. Calculations

See 4110B.5.

6. Quality Control

See 4110B.6.

NOTE: If any sample is pretreated, also pretreat QC samples.

7. Precision and Bias

The data in Table 4110:VIII provide single-laboratory precision and bias information for a variety of matrices. The HIW

matrix is designed to simulate a high-ionic-strength field sample.

It was prepared from reagent water that was fortified with

chloride at 100 mg/L, carbonate at 100 mg/L, nitrate at 10 mg/L

as nitrogen, phosphate at 10 mg/L as phosphorus, and sulfate at

100 mg/L.

TABLE 4110:VII. STOCK STANDARD PREPARATION

Anion Salt

Amount

g/100 mL

Bromide NaBr 0.1288

Bromate NaBrO3 0.1180

Chlorate NaClO3 0.1275

Chlorite* NaClO2 0.1676

* High-purity sodium chlorite is not commercially available. The value assumes

the use of a salt that is exactly 80% pure. Preferably confirm concentration of the

chlorite stock standard by iodometric titration (4500-ClO2C). Also demonstrate

that this stock is free of the other target anions before preparing mixed working

standards.

ION CHROMATOGRAPHY (4110)/Ion Chromatographic Determination of Oxyhalides and Bromide

7
TABLE 4110:VIII. SINGLE-OPERATOR PRECISION AND ACCURACY FOR BROMIDE, CHLORATE, CHLORITE, AND BROMATE*

Analyte Matrix†

Unfortified

Conc

g/L‡

Fortified

Conc

g/L

Mean

Conc

g/L

Mean

Recovery§

%R

SD(n1)

g/L

RSD

%

Bromide RW DL 20.0 20.9 104 0.50 3.82

100 107 107 0.60 0.56

HIW 3.24 20.0 21.8 92.5 0.79 3.63

100 105 102 1.05 1

SW 31.0 20.0 51.3 —§ 0.97 1.9

100 140 109 1.88 1.35

GW 151 20.0 172 — 0.78 0.45

100 265 — 2.18 0.82

ClW 16.3 20.0 39.3 115 0.64 1.62

100 125 109 2.00 1.6

CDW 11.5 20.0 34.4 115 0.76 2.22

100 125 113 1.24 0.99

O3W 39.8 20.0 65.4 — 3.67 5.61

100 153 113 1.00 0.65

Chlorate RW DL 100 98.3 98.3 0.80 0.82

500 520 104 4.15 0.8

HIW DL 100 86.1 86.1 1.47 1.7

500 502 100 4.52 0.9

SW 3.18 100 102 98.3 1.57 1.55

500 513 102 7.11 1.39

GW DL 100 93.5 93.5 2.00 2.14

500 510 102 3.84 0.75

ClW 34.4 100 136 102 1.01 0.74

500 549 103 3.11 0.57

CDW 121 100 223 — 3.20 1.44

500 651 106 3.50 0.54

O3W 6.15 100 106 100 1.20 1.13

500 523 103 2.45 0.47

Chlorite RW DL 100 96.2 96.2 0.95 0.99

500 523 105 3.13 0.60

HIW DL 100 102 102 2.19 2.15

500 520 104 3.64 0.70

SW DL 100 91.4 91.4 1.22 1.33

500 495 99.0 7.54 1.52

GW DL 100 92.9 92.9 1.65 1.77

500 490 98.1 3.40 0.69

ClW DL 100 87.4 87.4 0.59 0.68

500 485 97.1 6.36 1.31

CDW 292 100 396 — 1.64 0.41

500 811 104 4.00 0.49

O3W DL 100 84.4 84.4 0.46 0.54

500 481 96.1 3.24 0.67

Bromate RW DL 5.00 5.04 101 0.45 8.86

25.0 26.5 106 1.71 6.47

HIW DL 5.00 4.88 97.5 0.95 19.5

25.0 25.6 102 1.37 5.37

SW DL 5.00 4.46 89.2 0.58 13.0

25.0 26.3 105 1.10 4.18

GW DL 5.00 5.10 102 0.50 9.75

25.0 22.2 88.9 1.29 5.81

ClW DL 5.00 4.63 92.6 0.77 16.7

25.0 25.1 100 1.64 6.55

CDW DL 5.00 4.14 82.7 0.62 15.1

25.0 25.1 101 1.28 5.09

O3W 1.45 5.00 5.49 80.9 0.61 11.1

25.0 24.1 90.6 1.13 4.69

* Nine replicates were analyzed for each matrix/concentration combination. Analytical conditions: Ion chromatograph — Dionex DX500; columns — Dionex AG9-HC/

AS9-HC, 2 mm; detector — Dionex CD20; suppressor — ASRS-I, external water electrolytic mode, 100 mA current; eluent — 9.0 mM Na2CO3; eluent flow —

0.40 mL/min; sample loop  50 L.

† RW reagent water

HIW high-ionic-strength water

SW surface water

GW ground water

ClW chlorinated drinking water

CDW chlorine-dioxide-treated drinking water

O3W ozonated drinking water

‡ DL indicates less than minimum detection level.

§ Blank (—) indicates mean was not calculated since amount fortified was less than unfortified native matrix concentration.

SOURCE: PFAFF, J.D., D.F. HAUTMAN & D.J. MUNCH. U.S. ENVIRONMENTAL PROTECTION AGENCY. 1997. Determination of Inorganic Anions in Drinking Water by Ion

Chromatography. Method 300.1, U.S. Environmental Protection Agency, National Exposure Research Lab, Off. Research & Development, Cincinnati, Ohio.

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