## 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 forspecific treatment. More recently, the need to measure the concentration of the disinfection by-products chlorite, chlorate, andbromate 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 (ClO 2  

### , ClO 3 


### , and BrO 3  

### ), and the oxy-ions (PO 4 3

 

### , SO 4 2

 

### , NO 2  

### , and NO 3  

### ).

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 beanalyzed 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 alow-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 conductiveacid 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 resultfrom 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 com

monly encountered: first, with some column/eluent combinations the fluoride peak elutes very close to the baselinedepression 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 organicacids (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. D ETECTION 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 orchromatography 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 areavailable 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 m M NaHCO 3  

### , 1.8 m M Na2 

### CO 3 

### . Dissolve 0.5712 g NaHCO 3 

### and 0.7632 g Na2 

### CO 3 

### in water and dilute to 4 L. Degas eluent beforeuse 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 stablefor 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 thecolumn/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.2 b and 3 b , respectively, are used, retention always is in the order F  

### , Cl  

### , NO 2  

### , Br  

### , NO 3  

### , HPO 4 2

 

### , and SO 4 2

 

### . Inject at least three different concentrations for each anion to be measured. Use concentrations that will bracket theexpected 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. S TOCK S TANDARD PREPARATIONS

Anion Salt Amount g/100 mL

Fluoride NaF 0.2210 Chloride NaCl 0.1649 Bromide NaBr 0.1288 Nitrate-N* NaNO 3 0.6068 Nitrite-N* NaNO 2 0.4926 Phosphate-P KH 2PO 4 0.4394 Sulfate K2 SO 4 0.1814
* Do not oven-dry. Dry to constant weight in a dessicator. Figure 4110:1. Typical inorganic anion separation . Eluent: 1.7 m M NaHCO 3 , 1.8 m M NaCO 3 ; 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 stan

dards 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. HPO 4 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 eitherreagent water or eluent and is either shaken or sonicated. (A representative standardized method for such extractions is available. 1 

### ) Docu

ment 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 S OCIETY FOR TESTING AND M ATERIALS . 1992. Method

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

### 9. Bibliography

S MALL, H., T. S TEVENS & W. B AUMAN . 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. B YNUM , 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. B ROCKHOFF & J.W. O’D ELL . 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. Method300.1, 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. S INGLE -LABORATORY PRECISION (O NE S TANDARD D EVIATION) AND B IAS D ATA FOR 30 S ETS OF S AMPLES OVER A 2-M ONTH -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 ofthe column packing material. Direct conductivity detection without chemical suppression is used to determine concentrations.

b. Interferences: See 4110B.1 b . Note that HCO 3  

### elutes be

tween 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 ratioof 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 accessoriesincluding 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.3 a

. 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 C 18 

### 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 m M borate, 0.83 m M 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.3 d

.

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. Retentiontimes 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. N OTE 

### : The columns and other hardwarediscussed 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. F OERST , G. M C KEE , S. Q UAVE & W. B UDDE . 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.1 a

. 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  

### car

tridge.* 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. D ETECTION 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. S INGLE -C OLUMN C HROMATOGRAPHY S INGLE -O PERATOR PRECISION AND B IAS *

Anion Sample Type† Amount Added mg/L Mean Recovery % SD mg/L

Cl  RW 16 105 1.6 DW 16 98 1.9 NO 2  -N RW 4 101 0.10 DW 4 101 0.43 Br  RW 16 104 0.75 DW 16 98 2.3 NO 3  -N RW 8 103 0.75 DW 8 87 1.9 PO 4 3

 -P RW 16 113 0.92 DW 16 110 1.6 SO 4 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. † RW reagent water; DW drinking 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 inthe 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.2 a

. 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.3 a

. b. Eluent solution, appropriate to the column used to resolve the target anions. Figure 4110:3 was obtained by using 9 m M 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.4 a

. 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.2 b and 3 b are used, retention is in

† Dionex P/N 51786, or equivalent. ‡ Dionex P/N 51791, or equivalent.

TABLE 4110:VI. D ETECTION 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 m M Na2 CO 3 ; 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. S OURCE : PFAFF , J.D., D.F. H AUTMAN & D.J. M UNCH . 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 m M Na2 CO 3 ; 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.4 c

.

5. Calculations



### See 4110B.5.

6. Quality Control



### See 4110B.6. N OTE 

### : 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. S TOCK S TANDARD PREPARATION

Anion Salt Amount g/100 mL

Bromide NaBr 0.1288 Bromate NaBrO 3 0.1180 Chlorate NaClO 3 0.1275 Chlorite* NaClO 2 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-ClO 2  C). 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

7TABLE 4110:VIII. S INGLE -O PERATOR PRECISION AND A CCURACY FOR B ROMIDE , C HLORATE , C HLORITE , AND B ROMATE *

Analyte Matrix† Unfortified Conc


g/L ‡ Fortified Conc


g/L Mean Conc


g/L Mean Recovery§ % R SD( n
 1)


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 O 3 W 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 O 3 W 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 — Dio nex AG9-HC/ AS9-HC, 2 mm; detector — Dionex CD20; suppressor — ASRS-I, external water electrolytic mode, 100 mA current; eluent — 9.0 m M Na2 CO 3 ; 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 O 3 W 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. S OURCE : PFAFF , J.D., D.F. H AUTMAN & D.J. M UNCH . U.S. ENVIRONMENTAL PROTECTION A GENCY . 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. ION CHROMATOGRAPHY (4110)/Ion Chromatographic Determination of Oxyhalides and Bromide

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