Method 300.0 Determination of Inorganic Anions by Ion Chromatography, Rev. 2.1

METHOD 300.0

DETERMINATION OF INORGANIC ANIONS BY ION CHROMATOGRAPHY

John D. Pfaff

Inorganic Chemistry Branch

Chemistry Research Division

Revision 2.1

August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY

CINCINNATI, OHIO 45268

METHOD 300.0

DETERMINATION OF INORGANIC ANIONS BY ION CHROMATOGRAPHY

1.0 SCOPE AND APPLICATION

1.1 This method covers the determination of the following inorganic anions:

PART A.

Bromide Nitrite

Chloride Ortho-Phosphate-P

Fluoride Sulfate

Nitrate

PART B.

Bromate Chlorite

Chlorate

1.2 The matrices applicable to each method are shown below:

1.2.1 Drinking water, surface water, mixed domestic and industrial

wastewaters, groundwater, reagent waters, solids (after extraction 11.7),

leachates (when no acetic acid is used).

1.2.2 Drinking water and reagent waters

1.3 The single laboratory Method Detection Limit (MDL defined in Section 3.2) for

the above analytes is listed in Tables 1A and 1B. The MDL for a specific

matrix may differ from those listed, depending upon the nature of the sample.

1.4 Method A is recommended for drinking and wastewaters. The multilaboratory

ranges tested for each anion are as follows:

Analyte

mg/L

Bromide 0.63 - 21.0

Chloride 0.78 - 26.0

Fluoride 0.26 - 8.49

Nitrate-N 0.42 - 14.0

Nitrite-N 0.36 - 12.0

Otho-Phosphate-P 0.69 - 23.1

Sulfate 2.85 - 95.0

1.5 This method is recommended for use only by or under the supervision of

analysts experienced in the use of ion chromatography and in the

interpretation of the resulting ion chromatograms.

1.6 When this method is used to analyze unfamiliar samples for any of the above

anions, anion identification should be supported by the use of a fortified

sample matrix covering the anions of interest. The fortification procedure is

described in Section 11.6.

1.7 Users of the method data should state the data-quality objectives prior to

analysis. Users of the method must demonstrate the ability to generate

acceptable results with this method, using the procedures described in

Section 9.0.

2.0 SUMMARY OF METHOD

2.1 A small volume of sample, typically 2-3 mL, is introduced into an ion

chromatograph. The anions of interest are separated and measured, using a

system comprised of a guard column, analytical column, suppressor device,

and conductivity detector.

2.2 The main differences between Parts A and B are the separator columns and

guard columns. Sections 6.0 and 7.0 will elicit the differences.

2.3 An extraction procedure must be performed to use this method for solids

(See Section 11.7).

2.4 Limited performance-based method modifications may be acceptable provided

they are fully documented and meet or exceed requirements expressed in

Section 9.0, Quality Control.

3.0 DEFINITIONS

3.1 Calibration Blank (CB) -- A volume of reagent water fortified with the same

matrix as the calibration standards, but without the analytes, internal

standards, or surrogate analytes.

3.2 Calibration Standard (CAL) -- A solution prepared from the primary dilution

standard solution or stock standard solutions and the internal standards and

surrogate analytes. The CAL solutions are used to calibrate the instrument

response with respect to analyte concentration.

3.3 Field Duplicates (FD) -- Two separate samples collected at the same time and

placed under identical circumstances and treated exactly the same throughout

field and laboratory procedures. Analyses of field duplicates indicate the

precision associated with sample collection, preservation and storage, as well

as with laboratory procedures.

3.4 Instrument Performance Check Solution (IPC) -- A solution of one or more

method analytes, surrogates, internal standards, or other test substances used

to evaluate the performance of the instrument system with respect to a defined

set of criteria.

3.5 Laboratory Fortified Blank (LFB) -- An aliquot of reagent water or other blank

matrices to which known quantities of the method analytes are added in the

laboratory. The LFB is analyzed exactly like a sample, and its purpose is to

determine whether the methodology is in control, and whether the laboratory

is capable of making accurate and precise measurements.

3.6 Laboratory Fortified Sample Matrix (LFM) -- An aliquot of an environmental

sample to which known quantities of the method analytes are added in the

laboratory. The LFM is analyzed exactly like a sample, and its purpose is to

determine whether the sample matrix contributes bias to the analytical results.

The background concentrations of the analytes in the sample matrix must be

determined in a separate aliquot and the measured values in the LFM

corrected for background concentrations.

3.7 Laboratory Reagent Blank (LRB) -- An aliquot of reagent water or other blank

matrices that are treated exactly as a sample including exposure to all

glassware, equipment, solvents, reagents, internal standards, and surrogates

that are used with other samples. The LRB is used to determine if method

analytes or other interferences are present in the laboratory environment, the

reagents, or the apparatus.

3.8 Linear Calibration Range (LCR) -- The concentration range over which the

instrument response is linear.

3.9 Material Safety Data Sheet (MSDS) -- Written information provided by

vendors concerning a chemical's toxicity, health hazards, physical properties,

fire, and reactivity data including storage, spill, and handling precautions.

3.10 Method Detection Limit (MDL) -- The minimum concentration of an analyte

that can be identified, measured and reported with 99% confidence that the

analyte concentration is greater than zero.

3.11 Performance Evaluation Sample (PE) -- A solution of method analytes

distributed by the Quality Assurance Research Division (QARD),

Environmental Monitoring Systems Laboratory (EMSL-Cincinnati), U. S.

Environmental Protection Agency, Cincinnati, Ohio, to multiple laboratories for

analysis. A volume of the solution is added to a known volume of reagent

water and analyzed with procedures used for samples. Results of analyses are

used by QARD to determine statistically the accuracy and precision that can be

expected when a method is performed by a competent analyst. Analyte true

values are unknown to the analyst.

3.12 Quality Control Sample (QCS) -- A solution of method analytes of known

concentrations that is used to fortify an aliquot of LRB or sample matrix. The

QCS is obtained from a source external to the laboratory and different from

the source of calibration standards. It is used to check laboratory performance

with externally prepared test materials.

3.13 Stock Standard Solution (SSS) -- A concentrated solution containing one or

more method analytes prepared in the laboratory using assayed reference

materials or purchased from a reputable commercial source.

4.0 INTERFERENCES

4.1 Interferences can be caused by substances with retention times that are similar

to and overlap those of the anion of interest. Large amounts of an anion can

interfere with the peak resolution of an adjacent anion. Sample dilution

and/or fortification can be used to solve most interference problems associated

with retention times.

4.2 The water dip or negative peak that elutes near, and can interfere with, the

fluoride peak can usually be eliminated by the addition of the equivalent of 1

mL of concentrated eluent (7.3 100X) to l00 mL of each standard and sample.

4.3 Method interferences may be caused by contaminants in the reagent water,

reagents, glassware, and other sample processing apparatus that lead to

discrete artifacts or elevated baseline in ion chromatograms.

4.4 Samples that contain particles larger than 0.45 microns and reagent solutions

that contain particles larger than 0.20 microns require filtration to prevent

damage to instrument columns and flow systems.

4.5 Any anion that is not retained by the column or only slightly retained will

elute in the area of fluoride and interfere. Known coelution is caused by

carbonate and other small organic anions. At concentrations of fluoride above

1.5 mg/L, this interference may not be significant, however, it is the

responsibility of the user to generate precision and accuracy information in

each sample matrix.

4.6 The acetate anion elutes early during the chromatographic run. The retention

times of the anions also seem to differ when large amounts of acetate are

present. Therefore, this method is not recommended for leachates of solid

samples when acetic acid is used for pH adjustment.

4.7 The quantitation of unretained peaks should be avoided, such as low

molecular weight organic acids (formate, acetate, propionate etc.) which are

conductive and coelute with or near fluoride and would bias the fluoride

quantitation in some drinking and most waste waters.

4.8 Any residual chlorine dioxide present in the sample will result in the

formation of additional chlorite prior to analysis. If any concentration of

chlorine dioxide is suspected in the sample purge the sample with an inert gas

(argon or nitrogen) for about five minutes or until no chlorine dioxide remains.

5.0 SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method have not

been fully established. Each chemical should be regarded as a potential health

hazard and exposure should be as low as reasonably achievable. Cautions are

included for known extremely hazardous materials or procedures.

5.2 Each laboratory is responsible for maintaining a current awareness file of

OSHA regulations regarding the safe handling of the chemicals specified in

this method. A reference file of Material Safety Data Sheets (MSDS) should be

made available to all personnel involved in the chemical analysis. The

preparation of a formal safety plan is also advisable.

5.3 The following chemicals have the potential to be highly toxic or hazardous,

consult MSDS.

5.3.1 Sulfuric acid (Section 7.4)

6.0 EQUIPMENT AND SUPPLIES

6.1 Balance -- Analytical, capable of accurately weighing to the nearest 0.000l g.

6.2 Ion chromatograph -- Analytical system complete with ion chromatograph and

all required accessories including syringes, analytical columns, compressed

gasses and detectors.

6.2.1 Anion guard column: A protector of the separator column. If omitted

from the system the retention times will be shorter. Usually packed

with a substrate the same as that in the separator column.

6.2.2 Anion separator column: This column produces the separation shown

in Figures 1 and 2.

6.2.2.1 Anion analytical column (Method A): The separation shown in Figure

1 was generated using a Dionex AS4A column (P/N 37041). An

optional column may be used if comparable resolution of peaks is

obtained, and the requirements of Section 9.2 can be met.

6.2.2.2 Anion analytical column (Method B): The separation shown in Figure 2

was generated using a Dionex AS9 column (P/N 42025). An optional

column may be used if comparable resolution of peaks is obtained and

the requirements of Section 9.2 can be met.

6.2.3 Anion suppressor device: The data presented in this method were

generated using a Dionex anion micro membrane suppressor

(P/N 37106).

6.2.4 Detector -- Conductivity cell: Approximately 1.25 µL internal volume,

(Dionex, or equivalent) capable of providing data as required in

Section 9.2.

6.3 The Dionex AI-450 Data Chromatography Software was used to generate all

the data in the attached tables. Systems using a stripchart recorder and

integrator or other computer based data system may achieve approximately

the same MDL's but the user should demonstrate this by the procedure

outlined in Section 9.2.

7.0 REAGENTS AND STANDARDS

7.1 Sample bottles: Glass or polyethylene of sufficient volume to allow replicate

analyses of anions of interest.

7.2 Reagent water: Distilled or deionized water, free of the anions of interest.

Water should contain particles no larger than 0.20 microns.

7.3 Eluent solution (Method A and Method B): Sodium bicarbonate

(CASRN 144-55-8) 1.7 mM, sodium carbonate (CASRN 497-19-8) 1.8 mM.

Dissolve 0.2856 g sodium bicarbonate (NaHCO ) and 0.3816 g of sodium

carbonate (Na CO ) in reagent water (Section 7.2) and dilute to 2 L.

2 3

7.4 Regeneration solution (micro membrane suppressor): Sulfuric acid

(CASRN-7664-93-9) 0.025N. Dilute 2.8 mL conc. sulfuric acid (H SO ) to 4 L

2 4

with reagent water.

7.5 Stock standard solutions, l000 mg/L (1 mg/mL): Stock standard solutions

may be purchased as certified solutions or prepared from ACS reagent grade

materials (dried at 105°C for 30 minutes) as listed below.

7.5.1 Bromide (Br ) 1000 mg/L: Dissolve 1.2876 g sodium bromide (NaBr,

CASRN 7647-15-6) in reagent water and dilute to 1 L.

7.5.2 Bromate (BrO ) 1000 mg/L: Dissolve 1.1798g of sodium bromate

(NaBrO , CASRN 7789-38-0) in reagent water and dilute to 1 L.

7.5.3 Chlorate (Cl0 ) 1000 mg/L: Dissolve 1.2753g of sodium chlorate

(NaC10 , CASRN 7775-09-9) in reagent water and dilute to 1 L.

7.5.4 Chloride (Cl ) l000 mg/L: Dissolve 1.6485 g sodium chloride (NaCl,

CASRN 7647-l4-5) in reagent water and dilute to 1 L.

7.5.5 Chlorite (Cl0 ) 1000 mg/L: Dissolve 1.3410g of sodium chlorite

(NaC10 , CASRN 7758-19-2) in reagent water and dilute to 1 L.

7.5.6 Fluoride (F ) 1000 mg/L: Dissolve 2.2100g sodium fluoride (NaF,

CASRN 7681-49-4) in reagent water and dilute to 1 L.

7.5.7 Nitrate (NO -N) 1000 mg/L: Dissolve 6.0679 g sodium nitrate (NaNO ,

3 3

CASRN 7631-99-4) in reagent water and dilute to 1 L.

7.5.8 Nitrite (NO -N) 1000 mg/L: Dissolve 4.9257 g sodium nitrite (NaNO ,

2 2

CASRN 7632-00-0) in reagent water and dilute to 1 L.

7.5.9 Phosphate (PO

-P) 1000 mg/L: Dissolve 4.3937 g potassium phosphate

(KH

, CASRN 7778-77-0) in reagent water and dilute to 1 L.

7.5.10 Sulfate (SO

) 1000 mg/L: Dissolve 1.8141 g potassium sulfate (K

CASRN 7778-80-5) in reagent water and dilute to 1 L.

Note: Stability of standards: Stock standards (7.5) are stable for at

least one month when stored at 4°C. Except for the chlorite standard

which is only stable for two weeks. Dilute working standards should

be prepared weekly, except those that contain nitrite and phosphate

should be prepared fresh daily.

7.6 Ethylenediamine preservation solution: Dilute 10 mL of ethylenediamine (99%)

(CASRN 107-15-3) to 200 mL with reagent water.

Use 1 mL of this dilution to

each 1 L of sample taken.

8.0 SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1 Samples should be collected in plastic or glass bottles. All bottles must be

thoroughly cleaned and rinsed with reagent water. Volume collected should

be sufficient to insure a representative sample, allow for replicate analysis, if

required, and minimize waste disposal.

8.2 Sample preservation and holding times for the anions that can be determined

by this method are as follows:

Analyte

Preservation Holding Time

Bromate None required 28 days

Bromide None required 28 days

Chlorate None required 28 days

Chloride None required 28 days

Chlorite Cool to 4°C immediately

Fluoride None required 28 days

Nitrate-N Cool to 4°C 48 hours

Combined conc. H SO

2 4

28 days

(Nitrate/Nitrite) to a pH <2

Nitrite-N Cool to 4°C 48 hours

0-Phosphate-P Cool to 4°C 48 hours

Sulfate Cool to 4°C 28 days

Note: If the determined value for the combined nitrate/nitrite exceeds

0.5 mg/L as N , a resample must be analyzed for the individual concentrations

of nitrate and nitrite.

8.3 The method of preservation and the holding time for samples analyzed by this

method are determined by the anions of interest. In a given sample, the anion

that requires the most preservation treatment and the shortest holding time

will determine the preservation treatment. It is recommended that all samples

be cooled to 4°C and held for no longer than 28 days for Method A and

analyzed immediately in Method B.

Note: If the sample cannot be analyzed for chlorite within ≤10 minutes, the

sample may be preserved by adding 1 mL of the ethylenediamine (EDA)

preservation solution (Section 7.6) to 1 L of sample. This will preserve the

concentration of the chlorite for up to 14 days. This addition of EDA has no

effect on bromate or chlorate, so they can also be determined in a sample

preserved with EDA. Residual chlorine dioxide should be removed from the

sample (per Section 4.8) prior to the addition of EDA.

9.0 QUALITY CONTROL

9.1 Each laboratory using this method is required to operate a formal quality

control (QC) program. The minimum requirements of this program consist of

an initial demonstration of laboratory capability, and the periodic analysis of

laboratory reagent blanks, fortified blanks and other laboratory solutions as a

continuing check on performance. The laboratory is required to maintain

performance records that define the quality of the data that are generated.

9.2 INITIAL DEMONSTRATION OF PERFORMANCE

9.2.1 The initial demonstration of performance is used to characterize

instrument performance (determination of LCRs and analysis of QCS)

and laboratory performance (determination of MDLs) prior to

performing analyses by this method.

9.2.2 Linear Calibration Range (LCR) -- The LCR must be determined

initially and verified every six months or whenever a significant change

in instrument response is observed or expected. The initial

demonstration of linearity must use sufficient standards to insure that

the resulting curve is linear. The verification of linearity must use a

minimum of a blank and three standards. If any verification data

exceeds the initial values by ±10%, linearity must be reestablished. If

any portion of the range is shown to be nonlinear, sufficient standards

must be used to clearly define the nonlinear portion.

9.2.3 Quality Control Sample (QCS) -- When beginning the use of this

method, on a quarterly basis or as required to meet data-quality needs,

verify the calibration standards and acceptable instrument performance

with the preparation and analyses of a QCS. If the determined

concentrations are not within ±10% of the stated values, performance of

the determinative step of the method is unacceptable. The source of

the problem must be identified and corrected before either proceeding

with the initial determination of MDLs or continuing with on-going

analyses.

9.2.4 Method Detection Limit (MDL) -- MDLs must be established for all

analytes, using reagent water (blank) fortified at a concentration of two

(6)

to three times the estimated instrument detection limit. To determine

MDL values, take seven replicate aliquots of the fortified reagent water

and process through the entire analytical method. Perform all

calculations defined in the method and report the concentration values

in the appropriate units. Calculate the MDL as follows:

where, t = Student's t value for a 99% confidence level

and a standard deviation estimate with n-1

degrees of freedom [t= 3.14 for seven replicates]

S = standard deviation of the replicate analyses

MDLs should be determined every six months, when a new operator

begins work or whenever there is a significant change in the

background or instrument response.

9.3 ASSESSING LABORATORY PERFORMANCE

9.3.1 Laboratory Reagent Blank (LRB) -- The laboratory must analyze at least

one LRB with each batch of samples. Data produced are used to assess

contamination from the laboratory environment. Values that exceed the

MDL indicate laboratory or reagent contamination should be suspected

and corrective actions must be taken before continuing the analysis.

9.3.2 Laboratory Fortified Blank (LFB) -- The laboratory must analyze at least

one LFB with each batch of samples. Calculate accuracy as percent

recovery (Section 9.4.2). If the recovery of any analyte falls outside the

required control limits of 90-110%, that analyte is judged out of control,

and the source of the problem should be identified and resolved before

continuing analyses.

9.3.3 The laboratory must use LFB analyses data to assess laboratory

performance against the required control limits of 90-110%. When

sufficient internal performance data become available (usually a

minimum of 20-30 analyses), optional control limits can be developed

from the percent mean recovery (x) and the standard deviation (S) of

the mean recovery. These data can be used to establish the upper and

lower control limits as follows:

UPPER CONTROL LIMIT = x + 3S

LOWER CONTROL LIMIT = x - 3S

The optional control limits must be equal to or better than the required

control limits of 90-110%. After each five to 10 new recovery

measurements, new control limits can be calculated using only the most

recent 20-30 data points. Also, the standard deviation (S) data should

be used to establish an on-going precision statement for the level of

concentrations included in the LFB. These data must be kept on file

and be available for review.

9.3.4 Instrument Performance Check Solution (IPC) -- For all determinations

the laboratory must analyze the IPC (a mid-range check standard) and

a calibration blank immediately following daily calibration, after every

tenth sample (or more frequently, if required) and at the end of the

sample run. Analysis of the IPC solution and calibration blank

immediately following calibration must verify that the instrument is

within ±10% of calibration. Subsequent analyses of the IPC solution

must verify the calibration is still within ±10%. If the calibration cannot

be verified within the specified limits, reanalyze the IPC solution. If the

second analysis of the IPC solution confirms calibration to be outside

the limits, sample analysis must be discontinued, the cause determined

and/or in the case of drift, the instrument recalibrated. All samples

following the last acceptable IPC solution must be reanalyzed. The

analysis data of the calibration blank and IPC solution must be kept on

file with the sample analyses data.

9.4 ASSESSING ANALYTE RECOVERY AND DATA QUALITY

9.4.1 Laboratory Fortified Sample Matrix (LFM) -- The laboratory must add a

known amount of analyte to a minimum of 10% of the routine samples.

In each case the LFM aliquot must be a duplicate of the aliquot used

for sample analysis. The analyte concentration must be high enough to

be detected above the original sample and should not be less than four

times the MDL. The added analyte concentration should be the same

as that used in the laboratory fortified blank.

9.4.1.1 If the concentration of fortification is less than 25% of the

background concentration of the matrix the matrix recovery

should not be calculated.

9.4.2 Calculate the percent recovery for each analyte, corrected for

concentrations measured in the unfortified sample, and compare these

values to the designated LFM recovery range 90-110%. Percent

recovery may be calculated using the following equation:

where, R = percent recovery

C = fortified sample concentration

C = sample background concentration

s = concentration equivalent of analyte added to sample

9.4.3 Until sufficient data becomes available (usually a minimum of 20-30

analysis), assess laboratory performance against recovery limits for

Method A of 80-120% and 75-125% for Method B. When sufficient

internal performance data becomes available develop control limits

from percent mean recovery and the standard deviation of the mean

recovery.

9.4.4 If the recovery of any analyte falls outside the designated LFM recovery

range and the laboratory performance for that analyte is shown to be in

control (Section 9.3), the recovery problem encountered with the LFM is

judged to be either matrix or solution related, not system related.

9.4.5 Where reference materials are available, they should be analyzed to

provide additional performance data. The analysis of reference samples

is a valuable tool for demonstrating the ability to perform the method

acceptably.

9.4.6 In recognition of the rapid advances occurring in chromatography, the

analyst is permitted certain options, such as the use of different

columns and/or eluents, to improve the separations or lower the cost of

measurements. Each time such modifications to the method are made,

the analyst is required to repeat the procedure in Section 9.2.

9.4.7 It is recommended that the laboratory adopt additional quality

assurance practices for use with this method. The specific practices that

are most productive depend upon the needs of the laboratory and the

nature of the samples. Field duplicates may be analyzed to monitor the

precision of the sampling technique. When doubt exists over the

identification of a peak in the chromatogram, confirmatory techniques

such as sample dilution and fortification, must be used. Whenever

possible, the laboratory should perform analysis of quality control

check samples and participate in relevant performance evaluation

sample studies.

9.4.8 At least quarterly, replicates of LFBs should be analyzed to determine

the precision of the laboratory measurements. Add these results to the

on-going control charts to document data quality.

9.4.9 When using Part B, the analyst should be aware of the purity of the

reagents used to prepare standards. Allowances must be made when

the solid materials are less than 99% pure.

10.0 CALIBRATION AND STANDARDIZATION

10.1 Establish ion chromatographic operating parameters equivalent to those

indicated in Tables 1A or 1B.

10.2 For each analyte of interest, prepare calibration standards at a minimum of

three concentration levels and a blank by adding accurately measured volumes

of one or more stock standards (Section 7.5) to a volumetric flask and diluting

to volume with reagent water. If a sample analyte concentration exceeds the

calibration range the sample may be diluted to fall within the range. If this is

not possible then three new calibration concentrations must be chosen, two of

which must bracket the concentration of the sample analyte of interest. Each

attenuation range of the instrument used to analyze a sample must be

calibrated individually.

10.3 Using injections of 0.1-1.0 mL (determined by injection loop volume) of each

calibration standard, tabulate peak height or area responses against the

concentration. The results are used to prepare a calibration curve for each

analyte. During this procedure, retention times must be recorded.

10.4 The calibration curve must be verified on each working day, or whenever the

anion eluent is changed, and after every 20 samples. If the response or

retention time for any analyte varies from the expected values by more than

±10%, the test must be repeated, using fresh calibration standards. If the

results are still more than ±10%, a new calibration curve must be prepared for

that analyte.

10.5 Nonlinear response can result when the separator column capacity is exceeded

(overloading). The response of the detector to the sample when diluted 1:1,

and when not diluted, should be compared. If the calculated responses are the

same, samples of this total anionic concentration need not be diluted.

11.0 PROCEDURE

11.1 Tables 1A and 1B summarize the recommended operating conditions for the

ion chromatograph. Included in these tables are estimated retention times that

can be achieved by this method. Other columns, chromatographic conditions,

or detectors may be used if the requirements of Section 9.2 are met.

11.2 Check system calibration daily and, if required, recalibrate as described in

Section 10.0.

11.3 Load and inject a fixed amount of well mixed sample. Flush injection loop

thoroughly, using each new sample. Use the same size loop for standards and

samples. Record the resulting peak size in area or peak height units. An

automated constant volume injection system may also be used.

11.4 The width of the retention time window used to make identifications should

be based upon measurements of actual retention time variations of standards

over the course of a day. Three times the standard deviation of a retention

time can be used to calculate a suggested window size for each analyte.

However, the experience of the analyst should weigh heavily in the

interpretation of chromatograms.

11.5 If the response for the peak exceeds the working range of the system, dilute

the sample with an appropriate amount of reagent water and reanalyze.

11.6 If the resulting chromatogram fails to produce adequate resolution, or if

identification of specific anions is questionable, fortify the sample with an

appropriate amount of standard and reanalyze.

Note: Retention time is inversely proportional to concentration. Nitrate and

sulfate exhibit the greatest amount of change, although all anions are affected

to some degree. In some cases this peak migration may produce poor

resolution or identification.

11.7 The following extraction should be used for solid materials. Add an amount

of reagent water equal to 10 times the weight of dry solid material taken as a

sample. This slurry is mixed for 10 minutes using a magnetic stirring device.

Filter the resulting slurry before injecting using a 0.45 µ membrane type filter.

This can be the type that attaches directly to the end of the syringe. Care

should be taken to show that good recovery and identification of peaks is

obtained with the user's matrix through the use of fortified samples.

11.8 It has been reported that lower detection limits for bromate (≈7 µg/L) can be

obtained using a borate based eluent

(7)

. The use of this eluent or other eluents

that improve method performance may be considered as a minor modification

of the method and as such still are acceptable.

11.9 Should more complete resolution be needed between peaks the eluent (7.3) can

be diluted. This will spread out the run but will also cause the later eluting

anions to be retained longer. The analyst must determine to what extent the

eluent is diluted. This dilution should not be considered a deviation from the

method.

12.0 DATA ANALYSIS AND CALCULATIONS

12.1 Prepare a calibration curve for each analyte by plotting instrument response

against standard concentration. Compute sample concentration by comparing

sample response with the standard curve. Multiply answer by appropriate

dilution factor.

12.2 Report only those values that fall between the lowest and the highest

calibration standards. Samples exceeding the highest standard should be

diluted and reanalyzed.

12.3 Report results in mg/L.

12.4 Report NO

as N

HPO

as P

13.0 METHODS PERFORMANCE

13.1 Tables 1A and 2A give the single laboratory (EMSL-Cincinnati) MDL for each

anion included in the method under the conditions listed.

13.2 Tables 2A and 2B give the single laboratory (EMSL-Cincinnati) standard

deviation for each anion included in the method in a variety of waters for the

listed conditions.

13.3 Multiple laboratory accuracy and bias data (S ) and estimated single operator

values (S ) for reagent, drinking and waste water using Method A are given

for each anion in Tables 3 through 9. Data from 19 laboratories were used for

this data.

13.4 Some of the bias statements, for example chloride and sulfate, may be

misleading due to spiking small increments of the anion into large naturally

occurring concentrations of the same anion.

14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the

quantity or toxicity of waste at the point of generation. Numerous

opportunities for pollution prevention exist in laboratory operation. The EPA

has established a preferred hierarchy of environmental management techniques

that places pollution prevention as the management option of first choice.

Whenever feasible, laboratory personnel should use pollution prevention

techniques to address their waste generation. When wastes cannot be feasibly

reduced at the source, the Agency recommends recycling as the next best

option.

14.2 Quantity of the chemicals purchased should be based on expected usage

during its shelf life and disposal cost of unused material. Actual reagent

preparation volumes should reflect anticipated usage and reagent stability.

14.3 For information about pollution prevention that may be applicable to

laboratories and research institutions, consult "Less is Better: Laboratory

Chemical Management for Waste Reduction," available from the American

Chemical Society's Department of Government Regulations and Science Policy,

1155 16th Street N.W., Washington, D.C. 20036, (202) 872-4477.

15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rules and

regulations. Excess reagents, samples and method process wastes should be

characterized and disposed of in an acceptable manner. The Agency urges

laboratories to protect the air, water, and land by minimizing and controlling

all releases from hoods and bench operations, complying with the letter and

spirit of any waste discharge permit and regulations, and by complying with

all solid and hazardous waste regulations, particularly the hazardous waste

identification rules and land disposal restrictions. For further information on

waste management consult the "Waste Management Manual for Laboratory

Personnel", available from the American Chemical Society at the address listed

in Section 14.3.

16.0 REFERENCES

1. "Determination of Inorganic Disinfection By-Products by Ion Chromatography",

J. Pfaff, C. Brockhoff. J. Am. Water Works Assoc., Vol 82, No. 4, pg 192.

2. Standard Methods for the Examination of Water and Wastewater, Method

4110B, "Anions by Ion Chromatography", 18th Edition of Standard Methods

(1992).

3. Dionex, System 4000 Operation and Maintenance Manual, Dionex Corp.,

Sunnyvale, California 94086, 1988.

4. Method Detection Limit (MDL) as described in "Trace Analyses for

Wastewater", J. Glaser, D. Foerst, G. McKee, S. Quave, W. Budde,

Environmental Science and Technology, Vol. 15, Number 12, page 1426,

December, 1981.

5. American Society for Testing and Materials. Test Method for Anions in Water

by Chemically-Suppressed Ion Chromatography D4327-91. Annual Book of

Standards, Vol 11.01 (1993).

6. Code of Federal Regulations 40, Ch. 1, Pt. 136, Appendix B.

7. Hautman, D.P. & Bolyard, M. Analysis of Oxyhalide Disinfection By-products

and other Anions of Interest in Drinking Water by Ion Chromatography. Jour.

of Chromatog., 602, (1992), 65-74.

17.0 TABLES, DIAGRAMS, FLOWCHARTS AND VALIDATION DATA

TABLE 1A. CHROMATOGRAPHIC CONDITIONS AND DETECTION LIMITS

IN REAGENT WATER (PART A)

Analyte Peak #

Retention Time

(min)

MDL

(mg/L)

Fluoride 1 1.2 0.01

Chloride 2 1.7 0.02

Nitrite-N 3 2.0 0.004

Bromide 4 2.9 0.01

Nitrate-N 5 3.2 0.002

o-Phosphate-P 6 5.4 0.003

Sulfate 7 6.9 0.02

Standard Conditions:

Columns: as specified in Sesction 6.2.2.1

Detector:

as specified in Section 6.2.4 Pump Rate: 2.0 mL/min.

Eluent: as specified in Section 7.3 Sample Loop: 50 µL

MDL calculated from data system using a y-axis selection of 1000 ns and with a

stripchart recorder with an attenuator setting of 1 uMHO full scale.

*See Figure 1

TABLE 1B. CHROMATOGRAPHIC CONDITIONS AND DETECTION LIMITS

IN REAGENT WATER (PART B)

Analyte Peak #

Retention Time

(min)

MDL

(mg/L)

Chlorite 1 2.8 0.01

Bromate 2 3.2 0.02

Chlorate 4 7.1 0.003

Standard Conditions:

Column:

as specified in Section 6.2.2.2

Detector: as specified in Section 6.2.4 Pump Rate: 1.0 mL/min.

Eluent: as specified in Section 7.3 Sample Loop: 50 µL

Attentuation - 1

y-axis - 500 ns

See Figure 2

TABLE 2A. SINGLE-OPERATOR ACCURACY AND BIAS OF STANDARD ANIONS

(METHOD A)

Mean

Recovery

Standard

Deviation

(mg/L)

Sample

Type

Known Conc.

(mg/L)

Number

of Replicates Analyte

Bromide RW 5.0 7 99 0.08

DW 5.0 7 105 0.10

SW 5.0 7 95 0.13

WW 5.0 7 105 0.34

GW 5.0 7 92 0.34

SD 2.0 7 82 0.06

Chloride RW 20.0 7 96 0.35

DW 20.0 7 108 1.19

SW 10.0 7 86 0.33

WW 20.0 7 101 5.2

GW 20.0 7 114 1.3

SD 20.0 7 90 0.32

Fluoride RW 2.0 7 91 0.05

DW 1.0 7 92 0.06

SW 1.0 7 73 0.05

WW 1.0 7 87 0.07

GW 0.4 7 95 0.07

SD 5.0 7 101 0.35

Nitrate-N RW 10.0 7 103 0.21

DW 10.0 7 104 0.27

SW 10.0 7 93 0.17

WW 10.0 7 101 0.82

GW 10.0 7 97 0.47

SD 10.0 7 82 0.28

Nitrite RW 10.0 7 97 0.14

DW 10.0 7 121 0.25

SW 5.0 7 92 0.14

WW 5.0 7 91 0.50

GW 10.0 7 96 0.35

SD 2.0 7 98 0.08

o-Phosphate-P RW 10.0 7 99 0.17

DW 10.0 7 99 0.26

SW 10.0 7 98 0.22

WW 10.0 7 106 0.85

GW 10.0 7 95 0.33

Sulfate RW 20.0 7 99 0.40

DW 50.0 7 105 3.35

SW 40.0 7 95 1.7

WW 40.0 7 102 6.4

GW 40.0 7 112 3.2

TABLE 2A. SINGLE-OPERATOR ACCURACY AND BIAS OF STANDARD ANIONS

(METHOD A)

Mean

Recovery

Standard

Deviation

(mg/L)

Sample

Type

Known Conc.

(mg/L)

Number

of Replicates Analyte

RW = Reagent Water WW = Mixed Domestic and Industrial

Wastewater

DW = Drinking Water GW = Groundwater

SW = Surface Water SD = USEPA QC Solid (shale)

TABLE 2B. SINGLE-OPERATOR ACCURACY AND BIAS OF BY-PRODUCT

(PART B)

Analyte Type

Sample

(mg/L)

Spike

of Replicates

Number

Recovery

Mean

(mg/L)

Deviation

Standard

Bromide RW 5.0

1.0

0.1

0.05

103

155

122

0.07

0.04

0.005

0.01

DW 5.0

1.0

0.1

0.05

0.04

0.02

0.005

Chlorate RW 5.0

1.0

0.1

0.05

101

100

119

0.06

0.01

0.05

DW 5.0

1.0

0.1

0.05

101

115

121

110

0.04

0.01

0.005

0.01

Chlorite RW 5.0

1.0

0.1

0.05

100

0.04

0.01

DW 5.0

1.0

0.1

0.05

100

0.03

0.02

0.00

0.01

RW = Reagent Water

DW = Drinking Water

TABLE 3. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

FLUORIDE

Amount

Added

mg/L

Amount Found

mg/L

Bias

% Water S

Reagent 0.26 0.25 0.08 0.11 -3.8

0.34 0.29 0.11 -14.7

2.12 2.12 0.07 0.12 0.0

2.55 2.48 0.14 -2.7

6.79 6.76 0.20 0.19 -0.4

8.49 8.46 0.30 -0.4

Drinking 0.26 0.24 0.08 0.05 -7.7

0.34 0.34 0.11 0.0

2.12 2.09 0.18 0.06 -1.4

2.55 2.55 0.16 0.0

6.79 6.84 0.54 0.25 +0.7

8.49 8.37 0.75 -1.4

Waste 0.26 0.25 0.15 0.06 -3.8

0.34 0.32 0.08 -5.9

2.12 2.13 0.22 0.15 +0.5

2.55 2.48 0.16 -2.7

6.79 6.65 0.41 0.20 -2.1

8.49 8.27 0.36 -2.6

TABLE 4. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

CHLORIDE

Amount

Added

mg/L

Amount Found

mg/L

Bias

% Water S

Reagent 0.78 0.79 0.17 0.29 +1.3

1.04 1.12 0.46 +7.7

6.50 6.31 0.27 0.14 -2.9

7.80 7.76 0.39 -0.5

20.8 20.7 0.54 0.62 -0.5

26.0 25.9 0.58 -0.4

Drinking 0.78 0.54 0.35 0.20 -30.8

1.04 0.51 0.38 -51.0

6.50 5.24 1.35 1.48 -19.4

7.80 6.02 1.90 -22.8

20.8 20.0 2.26 1.14 -3.8

26.0 24.0 2.65 -7.7

Waste 0.78 0.43 0.32 0.39 -44.9

1.04 0.65 0.48 -37.5

6.50 4.59 1.82 0.83 -29.4

7.80 5.45 2.02 -30.1

20.8 18.3 2.41 1.57 -11.8

26.0 23.0 2.50 -11.5

TABLE 5. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

NITRITE-NITROGEN

Amount

Added

mg/L

Amount

Found

mg/L

Bias

Water S

Reagent 0.36 0.37 0.04 0.04 +2.8

0.48 0.48 0.06 0.0

3.00 3.18 0.12 0.06 +6.0

3.60 3.83 0.12 +6.4

9.60 9.84 0.36 0.26 +2.5

12.0 12.1 0.27 +0.6

Drinking 0.36 0.30 0.13 0.03 -16.7

0.48 0.40 0.14 -16.7

3.00 3.02 0.23 0.12 +0.7

3.60 3.62 0.22 +0.6

9.60 9.59 0.44 0.28 -0.1

12.0 11.6 0.59 -3.1

Waste 0.36 0.34 0.06 0.04 -5.6

0.48 0.46 0.07 -4.2

3.00 3.18 0.13 0.10 +6.0

3.60 3.76 0.18 +4.4

9.60 9.74 0.49 0.26 +1.5

12.0 12.0 0.56 +0.3

TABLE 6. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

BROMIDE

Amount

Added

mg/L

Amount

Found

mg/L

Bias

% Water S

Reagent 0.63 0.69 0.11 0.05 +9.5

0.84 0.85 0.12 +1.2

5.24 5.21 0.22 0.21 -0.6

6.29 6.17 0.35 -1.9

16.8 17.1 0.70 0.36 +1.6

21.0 21.3 0.93 +1.5

Drinking 0.63 0.63 0.13 0.04 0.0

0.84 0.81 0.13 -3.6

5.24 5.11 0.23 0.13 -2.5

6.29 6.18 0.30 -1.7

16.8 17.0 0.55 0.57 +0.9

21.0 20.9 0.65 -0.4

Waste 0.63 0.63 0.15 0.09 0.0

0.84 0.85 0.15 +1.2

5.24 5.23 0.36 0.11 -0.2

6.29 6.27 0.46 -0.3

16.8 16.6 0.69 0.43 -1.0

21.0 21.1 0.63 +0.3

TABLE 7. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

NITRATE-NITROGEN

Amount

Added

mg/L

Amount

Found

mg/L

Bias

% Water S

Reagent 0.42 0.42 0.04 0.02 0.0

0.56 0.56 0.06 0.0

3.51 3.34 0.15 0.08 -4.8

4.21 4.05 0.28 -3.8

11.2 11.1 0.47 0.34 -1.1

14.0 14.4 0.61 +2.6

Drinking 0.42 0.46 0.08 0.03 +9.5

0.56 0.58 0.09 +3.6

3.51 3.45 0.27 0.10 -1.7

4.21 4.21 0.38 0.0

11.2 11.5 0.50 0.48 +2.3

14.0 14.2 0.70 +1.6

Waste 0.42 0.36 0.07 0.06 -14.6

0.56 0.40 0.16 -28.6

3.51 3.19 0.31 0.07 -9.1

4.21 3.84 0.28 -8.8

11.2 10.9 0.35 0.51 -3.0

14.0 14.1 0.74 +0.4

TABLE 8. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

ORTHO-PHOSPHATE

Amount

Added

mg/L

Amount

Found

mg/L

Bias

% Water S

Reagent 0.69 0.69 0.06 0.06 0.0

0.92 0.98 0.15 +6.5

5.77 5.72 0.36 0.18 -0.9

6.92 6.78 0.42 -2.0

18.4 18.8 1.04 0.63 +2.1

23.1 23.2 0.35 +2.4

Drinking 0.69 0.70 0.17 0.17 +1.4

0.92 0.96 0.20 +4.3

5.77 5.43 0.52 0.40 -5.9

6.92 6.29 0.72 -9.1

18.4 18.0 0.68 0.59 -2.2

23.1 22.6 1.07 -2.0

Waste 0.69 0.64 0.26 0.09 -7.2

0.92 0.82 0.28 -10.9

5.77 5.18 0.66 0.34 -10.2

6.92 6.24 0.74 -9.8

18.4 17.6 2.08 1.27 -4.1

23.1 22.4 0.87 -3.0

TABLE 9. MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR

SULFATE

Amount

Added

mg/L

Amount

Found

mg/L

Bias

% Water S

Reagent 2.85 2.83 0.32 0.52 -0.7

3.80 3.83 0.92 +0.8

23.8 24.0 1.67 0.68 +0.8

28.5 28.5 1.56 -0.1

76.0 76.8 3.42 2.33 +1.1

95.0 95.7 3.59 +0.7

Drinking 2.85 1.12 0.37 0.41 -60.7

3.80 2.26 0.97 -40.3

23.8 21.8 1.26 0.51 -8.4

28.5 25.9 2.48 -9.1

76.0 74.5 4.63 2.70 -2.0

95.0 92.3 5.19 -2.8

Waste 2.85 1.89 0.37 0.24 -33.7

3.80 2.10 1.25 -44.7

23.8 20.3 3.19 0.58 -14.7

28.5 24.5 3.24 -14.0

76.0 71.4 5.65 3.39 -6.1

95.0 90.3 6.80 -5.0