METHOD 557: DETERMINATION OF HALOACETIC ACIDS, 

BROMATE, AND DALAPON IN DRINKING WATER BY ION 

CHROMATOGRAPHY ELECTROSPRAY IONIZATION 

TANDEM MASS SPECTROMETRY (IC-ESI-MS/MS) 

Anndrdreeww W. B W. Brrei eidenbach EnEnvviirroonnmenttaall RReesseeararch CCeenntter er

Cinci Cincinna nnati, Ohio ti, Ohio

Office of Water (MLK 140) EPA Document No. 815-B-09-012 September 2009 www.epa.gov/safewater 
METHOD 557 DETERMINATION OF HALOACETIC ACIDS, BROMATE, AND 

DALAPON IN DRINKING WATER BY ION CHROMATOGRAPHY 

ELECTROSPRAY IONIZATION TANDEM MASS SPECTROMETRY 

(IC-ESI-MS/MS) 

Version 1.0 

September 2009 

A. D. Zaffiro and M. Zimmerman (Shaw Environmental, Inc.)
 

B. V. Pepich (U.S. EPA, Region 10 Laboratory)
 

Rosanne W. Slingsby, R. F. Jack and Christopher A. Pohl (Dionex Corporation)
 

D. J. Munch (U.S. EPA, Office of Ground Water and Drinking Water)
 

TECHNICAL SUPPORT CENTER
 

OFFICE OF GROUND WATER AND DRINKING WATER
 

U. S. ENVIRONMENTAL PROTECTION AGENCY 

CINCINNATI, OHIO 45268 

557-1
 
 

 

METHOD 557 

DETERMINATION OF HALOACETIC ACIDS, BROMATE, AND DALAPON IN DRINKING
 

WATER BY ION CHROMATOGRAPHY ELECTROSPRAY IONIZATION TANDEM MASS
 

SPECTROMETRY (IC-ESI-MS/MS)
 

1. SCOPE AND APPLICATION 

1.1	 Method 557 is a direct-inject, ion chromatography, negative-ion electrospray ionization, 

tandem mass spectrometry (IC-ESI-MS/MS) method for the determination of haloacetic acids 

in finished drinking water. Bromate and dalapon (2,2-dichloropropionic acid) may be 

measured concurrently with the haloacetic acids. Real time, chromatographic separation of 

common anions in drinking water (matrix elimination) is a key feature of this method. 

Acceptable method performance has been demonstrated for matrix ion concentrations of 320 

mg/L chloride, 250 mg/L sulfate, 150 mg/L bicarbonate and 20 mg/L nitrate. Method 557 

requires the use of MS/MS in Multiple Reaction Monitoring (MRM) mode to enhance 

selectivity. Precision and accuracy data have been generated for the detection of nine 

haloacetic acids, bromate, and dalapon in reagent water, synthetic sample matrix, and finished 

drinking water from both ground water and surface water sources. The single laboratory 

Lowest Concentration Minimum Reporting Level (LCMRL) has also been determined in 

reagent water. Method 557 is applicable for the measurement of the following analytes: 

Chemical Abstracts Services 

Analyte Registry Number (CASRN) 

Bromate (BrO3

-

) 15541-45-4 (BrO3

-

 anion) 

Bromochloroacetic acid (BCAA) 5589-96-8 

Bromodichloroacetic acid (BDCAA) 71133-14-7 

Chlorodibromoacetic acid (CDBAA) 5278-95-5 

Dalapon 75-99-0 

Dibromoacetic acid (DBAA) 631-64-1 

Dichloroacetic acid (DCAA) 79-43-6 

Monobromoacetic acid (MBAA) 79-08-3 

Monochloroacetic acid (MCAA) 79-11-8 

Tribromoacetic acid (TBAA) 75-96-7 

Trichloroacetic acid (TCAA) 76-03-9 

1.2	 The chromatographic and MRM mass spectrometry conditions described in this method were 

developed using commercially available IC-ESI-MS/MS systems. 

1.3	 The single laboratory LCMRL is the lowest spiking concentration such that the probability of 

spike recovery in the 50% to 150% range is at least 99%. Single laboratory LCMRLs for the 

analytes in this method ranged from 0.042 to 0.58 microgram per liter (μg/L), and are listed in 

Table 5. The procedure used to determine the LCMRL is described elsewhere.1 

557-2
 
 

 

1.4	 Laboratories using this method are not required to determine LCMRLs, but they must 

demonstrate that the Minimum Reporting Level (MRL) for each analyte meets the 

requirements described in Section 9.2.4. 

1.5	 Detection Limit (DL) is defined as the statistically calculated minimum concentration that can 

be measured with 99% confidence that the reported value is greater than zero.2 The DL is 

dependent on sample matrix, fortification concentration, and instrument performance. 

Determining the DL for analytes in this method is optional (Sect. 9.2.6). DLs for method 

analytes fortified into reagent water ranged from 0.015 to 0.20 μg/L (Table 6). 

1.6	 This method is intended for use by analysts skilled in the operation of IC-ESI-MS/MS instrumentation and the interpretation of the associated data. 

1.7 METHOD FLEXIBILITY – The laboratory is permitted to select IC columns, eluent 

compositions, eluent suppression techniques, and ESI-MS/MS conditions different from those 

utilized to develop the method. However, the basic chromatographic elements of the method 

must be retained. In order to avoid the effects of matrix suppression, the method analytes 

must be substantially resolved chromatographically from common anions in drinking water. 

Samples must be analyzed by direct injection. Filtering and pretreatment by use of solid 

phase extraction are not permitted. At a minimum, the four internal standards prescribed in 

this method must be used. Changes may not be made to sample collection and 

preservation (Sect. 8) or to the quality control (QC) requirements (Sect. 9). Method 

modifications should be considered only to improve method performance. Modifications that 

are introduced in the interest of reducing cost or sample processing time, but result in poorer 

method performance, may not be used. In all cases where method modifications are proposed, 

the analyst must perform the procedures outlined in the Initial Demonstration of Capability 

(IDC, Sect. 9.2), verify that all QC acceptance criteria in this method (Tables 11 and 12) are 

met, and verify method performance in a real sample matrix (Sect. 9.4). 

NOTE: Single quadrupole instruments are not permitted. 

2. SUMMARY OF METHOD 

Residual chlorine present in drinking water samples is reacted with ammonium chloride to form 

chloramines, effectively preventing chlorine-mediated formation of method analytes during 

storage. In addition, the combined chlorine residual prevents microbial degradation in the sample. 

Prior to analysis, isotopically enriched analytes (monochloroacetic acid-2-13C, monobromoacetic 

acid-1-13C, dichloroacetic acid-2-13C, and trichloroacetic acid-2-13C) are added to the samples as 

internal standards. An aliquot of the sample is injected without cleanup or concentration onto an 

ion exchange column specifically designed to separate method analytes from the following 

common anions (matrix components) in drinking water: chloride, carbonate, sulfate, and nitrate. 

The matrix components in the column eluate are monitored via conductivity detection and then 

diverted to waste; the analytes of interest are directed into the ESI-MS/MS system. Acetonitrile is 

added post-column to enhance desolvation of the method analytes in the ESI interface. Each 

557-3
 
 

method analyte is qualitatively identified via a unique mass transition, and the concentration is 

calculated using the integrated peak area and the internal standard technique. 

3. DEFINITIONS 

3.1	 ANALYSIS BATCH – A sequence of samples, analyzed within a 30-hour period, including 

no more than 20 field samples. Each Analysis Batch must also include all required QC 

samples, which do not contribute to the maximum field sample total of 20. The required QC 

samples include: 

Laboratory Reagent Blank (LRB),
 

Continuing Calibration Check (CCC) Standards, 

Laboratory Fortified Sample Matrix (LFSM), and 

Laboratory Fortified Sample Matrix Duplicate or Laboratory Duplicate (LFSMD or LD).
 

3.2	 CALIBRATION STANDARD – An aqueous solution of the method analytes prepared from 

the Primary Dilution Standard (Sect. 3.21) solution. The calibration standards are used to 

calibrate the instrument response with respect to analyte concentration. 

3.3	 CONTINUING CALIBRATION CHECK – A calibration standard containing the method 

analytes and internal standards, which is analyzed periodically to verify the accuracy of the 

existing calibration. 

3.4	 DETECTION LIMIT (DL) – The minimum concentration of an analyte that can be 

identified, measured, and reported with 99% confidence that the analyte concentration is 

greater than zero. This is a statistical determination (Sect. 9.2.6), and accurate quantitation is 

not expected at this level. 

3.5	 DIVERT WINDOW – The period of time during which the column eluate is directed to 

waste for the purpose of diverting matrix components away from the ESI-MS/MS system. 

3.6	 ELUTION WINDOW – The period of time during which the column eluate is directed to the 

ESI-MS/MS system for the purpose of measuring the method analytes. 

3.7	 INTERNAL STANDARD – A pure compound added to all standard solutions and samples 

in a known amount. Each internal standard is assigned to a specific analyte or multiple 

analytes, and is used to measure relative response. 

3.8	 ION SUPPRESSION/ENHANCEMENT – An observable loss or increase in analyte 

response in complex (field) samples as compared to the response obtained in standard 

solutions. 

3.9	 LABORATORY DUPLICATES (LDs) – Two sample aliquots (LD1 and LD2) taken in the 

laboratory from a single sample bottle, and analyzed separately with identical procedures. 

By cancelling variation contributed from sample collection, preservation, and storage 

557-4
 
 

procedures, Laboratory Duplicates provide an estimate of precision associated specifically 

with the analytical determination. 

3.10	 LABORATORY FORTIFIED BLANK (LFB) – An aliquot of reagent water, containing the 

method preservative, to which known quantities of the method analytes are added. The LFB 

is used during the IDC to verify method performance for precision and accuracy. 

3.11	 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – An aliquot of a field sample to 

which known quantities of the method analytes are added. The LFSM is processed and 

analyzed as a sample, and its purpose is to determine whether the sample matrix contributes 

bias to the analytical results. 

3.12	 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) – A second 

aliquot of the field sample used to prepare the LFSM which is fortified and analyzed 

identically to the LFSM. The LFSMD is used instead of the Laboratory Duplicate to assess 

method precision when the method analytes are rarely found at concentrations greater than 

the MRL. 

3.13	 LABORATORY FORTIFIED SYNTHETIC SAMPLE MATRIX (LFSSM) – Aliquots of the 

Laboratory Synthetic Sample Matrix (Sect. 3.15) fortified with known quantities of the 

method analytes. The LFSSM is analyzed at the beginning of each Analysis Batch to verify 

that the matrix components elute within the divert windows, and to ensure that no portion of 

an analyte peak is inadvertently diverted to waste. The LFSSM also serves as a QC sample 

for the purpose of estimating precision and accuracy during the IDC. 

3.14	 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water that contains the 

preservative and internal standards. The LRB is used to determine if the method analytes or 

other interferences are introduced from the laboratory environment, the reagents or 

glassware, and to test for cross contamination. 

3.15	 LABORATORY SYNTHETIC SAMPLE MATRIX (LSSM) – For this method, the LSSM is 

a solution of common anions prepared at high concentrations relative to their typical 

occurrence in drinking water. Guidance for preparation of the LSSM is provided in Section 

7.2. 

3.16	 LOWEST CONCENTRATION MINIMUM REPORTING LEVEL (LCMRL) – The single 

laboratory LCMRL is the lowest spiking concentration such that the probability of spike 

recovery in the 50% to 150% range is at least 99%.1 

3.17	 MATERIAL SAFETY DATA SHEETS (MSDS) – Written information provided by vendors 

concerning a chemical’s toxicity, health hazards, physical properties, fire and reactivity data, 

storage instructions, spill response procedures, and handling precautions. 

3.18	 MINIMUM REPORTING LEVEL (MRL) – The minimum concentration that can be 

reported by a laboratory as a quantified value for the method analyte in a sample following 

analysis. This concentration must meet the criteria defined in Section 9.2.4 and must be no 

557-5
 
 

 

 

lower than the concentration of the lowest calibration standard for each method analyte. A 

laboratory may be required to demonstrate a specific MRL by a regulatory body if this 

method is being performed for compliance purposes. 

3.19	 MULTIPLE REACTION MONITORING (MRM) – A mass spectrometric technique in 

which a precursor ion (Sect. 3.20) is first isolated, then subsequently fragmented into a 

product ion(s) (Sect. 3.23). Quantitation is accomplished by monitoring a specific product 

ion. As described in Section 10.2.2, MS parameters must be optimized for each precursor 

ion and product ion. 

3.20	 PRECURSOR ION – The precursor ion is the gas-phase species corresponding to the method 

analyte produced in the ESI interface. In MS/MS, the precursor ion is mass selected and 

fragmented by collision-activated dissociation to produce distinctive product ions of smaller 

mass/charge (m/z) ratio. 

3.21	 PRIMARY DILUTION STANDARD (PDS) – An aqueous solution containing the method 

analytes (or internal standards) prepared from Stock Standard Solutions and diluted as 

needed to prepare calibration standards and sample fortification solutions. 

3.22	 PROCEDURAL CALIBRATION – A calibration technique in which calibration standards 

are processed through the entire method, including sample preparation and addition of 

preservatives. 

3.23	 PRODUCT-ION – For the purpose of this method, a product ion is one of the fragment ions 

produced in MS/MS by collision-activated dissociation of the precursor ion. 

3.24	 QUALITY CONTROL SAMPLE (QCS) – A solution containing the method analytes at a 

known concentration, which is obtained from a source external to the laboratory and different 

from the source of calibration standards. The purpose of the QCS is to verify the accuracy of 

the primary calibration standards. 

3.25	 REAGENT WATER – Purified water that does not contain any measurable quantity of the 

method analytes or interfering compounds at or above 1/3 the MRL. 

3.26	 STOCK STANDARD SOLUTION (SSS) – A concentrated solution containing one or more 

of the method analytes that is prepared in the laboratory using assayed reference materials or 

purchased from a reputable commercial source, so that the concentration and purity of 

analytes are traceable to certificates of analysis. 

4. INTERFERENCES 

4.1	 GLASSWARE – During method development, no problems with stability of the method 

analytes, interferences, or cross contamination related to glass containers were observed. 

Sample collection bottles and vials containing samples and standards may be reused after 

thorough rinsing with reagent water. Dry glassware in an oven or air dry. Teflon-faced 

septa, if not punctured, may be cleaned and reused. Vials containing PDS solutions must be 

557-6
 
 

 

 

rinsed with methanol before reuse and the septa discarded. It is recommended that 

autosampler vials and septa be discarded after a single use. 

4.2	 REAGENTS AND EQUIPMENT – Method interferences may be caused by contaminants in 

solvents and reagents (including reagent water). All laboratory reagents must be routinely 

demonstrated to be free from interferences (less than 1/3 the MRL for the method analytes) 

under the conditions of the analysis. This may be accomplished by analyzing LRBs as 

described in Section 9.3.1. 

4.3	 MATRIX INTERFERENCES – Matrix interferences are caused by contaminants that are 

present in the sample. The extent of matrix interferences will vary considerably from source 

to source depending upon the nature of the water. Matrix components may directly interfere 

by producing a signal at or near the retention time of an analyte peak. Matrix components 

may also suppress or enhance the signal of the method analytes. (Suppression and 

enhancement effects occur during the ionization process in the electrospray source when a 

co-eluting contaminant influences the ionization of the analyte of interest.) Common anions 

present in drinking water matrices, which would cause matrix suppression, are diverted from 

the MS. In addition, the internal standards recommended in this method performed well in a 

variety of matrices. However, these measures may not compensate for all potential matrix 

effects. The analysis of Laboratory Fortified Sample Matrix (Sect. 9.3.5) provides evidence 

for the presence (or absence) of matrix effects. 

4.4	 INTERFERENCE FROM SYSTEM CONTAMINANTS – Contaminants in the mobile 

phase, autosampler, column, or other system components may produce a signal at or near the 

retention time of a method analyte. Such an interfering signal may be observed as a shoulder 

on an analyte peak or detected as an analyte peak in the Laboratory Reagent Blank. If this 

occurs, attempt to eliminate the interference. If unsuccessful, investigate alternate MRM 

transitions. 

4.5	 INTERFERENCE FROM INTERNAL STANDARDS – Depending on the source and 

purity, labeled haloacetic acid internal standards may contain a small percentage of the 

corresponding native analyte. Usually, such contributions are insignificant when performing 

the method within the normal calibration range of 0.25 to 20 μg/L. However, the 

contribution may be significant when attempting to determine LCMRLs and DLs. The 

labeled internal standards must meet the purity requirements stated in the IDC (Section 

9.2.1). 

4.6	 BREAKDOWN OF DALAPON, CDBAA, AND TBAA IN AQUEOUS MEDIA – Under 

the conditions described in Section 8, the method analytes are stable in aqueous media within 

the stated holding time. However, during method development, dalapon, CDBAA, and 

TBAA—in both standards and drinking water samples—degraded while awaiting analysis in 

conventional autosamplers that may reach temperatures between 25° and 30 °C during 

operation. For this reason, refrigerated autosamplers, capable of maintaining samples at a 

temperature of less than or equal to 10 °C, are required for use with Method 557. 

557-7
 
 

 

 

 

4.7	 ION SUPPRESSION IN THE PRESENCE OF CHLORITE – The chlorite anion (ClO2

-

) may 

be present in drinking water distribution systems employing chlorine dioxide (ClO2) as a 

disinfectant. During method development studies, severe signal suppression of MCAA and 

excessive band broadening of the MCAA chromatographic peak profile were observed in the 

presence of 1 mg/L ClO2

-

, the maximum contaminant level (MCL). As depicted in Figure 4, 

the ClO2

-

anion co-eluted with MCAA. Method 557 is not applicable to drinking water 

treated with ClO2 unless the laboratory demonstrates alternate chromatographic conditions 

(other than those used to develop the method, Section 17, Table 1) that eliminate the 

suppression. That is, chlorite must be resolved chromatographically from MCAA and the 

other method analytes. Alternately, the laboratory must demonstrate that the chlorite anion is 

not present in the sample matrix. 

4.8	 SIGNAL SUPPRESSION DUE TO EXCESSIVE BACKGROUND CONDUCTIVITY – 

The ESI interface is sensitive to the background conductivity of column eluate. The analyst 

should observe the background conductivity prior to starting an analysis sequence each day. 

If using a concentration gradient, make this observation at the initial eluent concentration. At 

the maximum concentration in the gradient, the background conductivity will increase 

compared to the conductivity at the initial concentration. In this region of the chromatogram, 

the potential for suppression from the background conductivity is greatest. Such suppression 

may be evidenced by difficulty detecting TBAA, or by peak areas that are low compared to 

historical values when the background conductivity was lower. Section 11.3.2 provides 

guidance on corrective action if background conductivity is problematic. 

4.9	 PEAK TAILING – Peak tailing may be observed as the column ages. Peak tailing will limit 

the analyst’s ability to separate matrix components from the method analytes. Peak tailing 

should be minimal with a properly configured ion chromatography system when using a new 

column. (See Figure 2.) If tailing is observed with continued column use, original 

performance can usually be restored by replacing the guard column. 

4.10	 EFFECT OF TEMPERATURE ON ANALYTE STABILITY – MBAA CDBAA, and TBAA 

degrade readily in aqueous eluent at high pH. Such conditions may exist in the mobile phase 

of ion exchange columns. The reaction is temperature dependent. For this reason, the 

separation is performed at subambient temperature, specifically 15 °C. At 15 °C, 

degradation in the column eluent is minimized. 

4.11	 MANAGING DIVERT WINDOWS – Analyte retention times may slowly shift toward 

lower values as the column ages or becomes fouled. Because this method employs multiple 

divert windows, the analyst must monitor peak locations on a daily basis to ensure that each 

analyte peak elutes entirely within the MS/MS elution windows. Guidance for verifying 

elution/divert windows is provided in Section 10.2.5. To avoid loss of column capacity, 

follow the manufacturer’s instructions for proper operating temperature and for storage 

conditions when the column is not in use. 

4.12	 BAND BROADENING AND RETENTION TIME (RT) SHIFTS IN HIGH IONIC 

STRENGTH MATRICES – Method performance has not been evaluated for matrix ion 

concentrations exceeding 320 mg/L chloride, 250 mg/L sulfate, 150 mg/L bicarbonate and 20 

557-8
 
 

mg/L nitrate. Near these limits, the analyte peaks will widen, peak height will decrease, and 

retention times will decrease slightly. These effects are compound dependent, but affect all 

analytes to some degree. Such effects were minimal in the drinking water matrices 

evaluated, but were more pronounced in Laboratory Synthetic Sample Matrix. [Compare 

Figure 3 (fortified tap water) and Figure 4 (fortified synthetic matrix).] Note that the 

concentrations of common anions in the LSSM are at the limits listed above. This method 

requires the analyst to verify method performance in LSSM during the IDC, and to verify 

elution/divert windows on a daily basis in LFSSM to ensure that these windows are properly 

set to compensate for the potential effects of high ionic strength matrices. 

5. SAFETY 

5.1 The toxicity and carcinogenicity of each reagent used in this method has not been precisely 

defined. Each chemical should be treated as a potential health hazard and exposure to these 

chemicals should be minimized. Each laboratory is responsible for maintaining an awareness 

of OSHA regulations regarding safe handling of chemicals used in this method.3

 The OSHA 

laboratory standards can be found online at 

http://www.osha.gov/SLTC/laboratories/standards.html. A reference file of MSDSs should be 

made available to all personnel involved in the chemical analysis. 

5.2 Pure standard materials and stock standard solutions of the method compounds should be 

handled with suitable protection for skin, eyes, etc.4 

6. EQUIPMENT AND SUPPLIES 

References to specific brands or catalog numbers are included as examples only and do not imply 

endorsement of the product. Such reference does not preclude the use of other vendors or 

suppliers. 

6.1 SAMPLE CONTAINERS – Amber glass bottles fitted with polytetrafluoroethylene (PTFE) 

-lined screw caps with sufficient volume to allow preparation of all required sample and QC 

aliquots. 

6.2	 VIALS FOR SAMPLE PREPARATION – Amber glass vials with PTFE/silicone septa for 

use preparing field samples and QC samples. Forty-milliliter (mL) volatile organic analysis 

(VOA) vials (I-Chem Cat. No. S146–0040 or equivalent) were used during method 

development. 

6.3	 AUTOSAMPLER VIALS – Glass vials with PTFE/silicone septa. 

6.4	 MICRO SYRINGES – Suggested sizes include 50, 100, and 1000 microliters (μL). 

6.5	 VOLUMETRIC PIPETTES – Class A, for preparing calibration standards, and for measuring 

aliquots of field samples and QC samples. 

6.6	 AUTOMATIC PIPETTE – Electronic, with polypropylene tips (Eppendorf Research Pro or 

equivalent). An automatic pipette is recommended for fortifying samples with internal 

standards. 

557-9
 
 

 

 

6.7	 ANALYTICAL BALANCE – Capable of weighing to the nearest 0.0001 gram (g). 

6.8	 TOP-LOADING BALANCE – Capable of weighing to the nearest 0.01 g. A top-loading 

balance and disposable pipettes may be used to measure aqueous sample volumes and to 

prepare aqueous calibration standards. 

6.9	 DESOLVATION GAS – High-purity gas (nitrogen or zero-air) for use in the ESI interface. 

The specific type of gas, purity and pressure requirements will depend on the instrument 

manufacturer’s specifications. 

6.10	 COLLISION GAS – High-purity gas (nitrogen or argon) for use in the collision cell of the 

mass spectrometer. The specific type of gas, purity, and pressure requirements will depend 

on the instrument manufacturer’s specifications. 

6.11	 DISPOSABLE PASTEUR PIPETTES – Borosilicate glass, used to transfer samples to 

autosampler vials and for sample preparation. 

6.12	 ION CHROMATOGRAPHY ELECTROSPRAY IONIZATION TANDEM MASS 

SPECTROMETRY SYSTEM (IC-ESI-MS/MS) – The following specifications are based on 

use of a Dionex Corporation AS24 ion exchange column and a hydroxide-based eluent 

system. Other columns and eluent systems are permitted providing that the basic 

chromatographic elements of the method are retained (Sect. 1.7). 

6.12.1 IC SYSTEM WITH SUPPRESSED CONDUCTIVITY DETECTION – An analytical 

system (Dionex ICS-3000 or equivalent) consisting of a refrigerated autosampler, pump 

module, anion trap, guard column, anion separator column, a six-port injection valve, 

sample loop, conductivity suppressor, conductivity detector, post-column divert valve, 

and a data acquisition and management system. The laboratory must be able to acquire 

and store conductivity data for the purpose of monitoring matrix components and 

establishing elution/divert windows. 

6.12.1.1 ELUENT GENERATION – Reagent-free electrolytic eluent generation (Dionex ICS3000 EG or equivalent) or manually prepared reagents may be used. Care must be 

exercised with manually prepared hydroxide eluent to prevent formation of carbonate 

in the eluent from exposure to the atmosphere, which could cause analyte retention 

times to drift. 

6.12.1.2 ANION TRAP – A continuously regenerated anion trap column (Dionex CR-ATC or 

equivalent). 

6.12.1.3 SAMPLE LOOP – 100-μL size. A 100-μL sample loop was used to generate the data 

presented in this method. Smaller injection volumes may be used as long as the 

Initial Demonstration of Capability (Sect. 9.2), calibration, and sample analyses are 

performed using the same injection volume. The laboratory must be able to meet the 

MRL verification criteria (Section 9.2.4) using the selected injection volume. 

557-10
 
6.12.1.4 GUARD COLUMN – IonPac® AG24, 2 x 50 millimeters (mm) (Dionex Part 

No. 064151 or equivalent). The guard column is generally packed with the same 

resin as the analytical column. 

6.12.1.5 ANALYTICAL COLUMN – IonPac® AS24, 2 x 250 mm (Dionex Part No. 064153 

or equivalent). Any column that provides on-line separation of common anions 

(chloride, carbonate, sulfate, and nitrate) from the method analytes and symmetrical 

peak shapes may be used. The column must have sufficient capacity to minimize 

retention time shifts in high ionic strength matrices. 

6.12.1.6 COLUMN COMPARTMENT – Temperature controlled and capable of subambient 

operation. 

6.12.1.7 CONDUCTIVITY SUPPRESSOR – An electrolytic suppressor operated with an 

external source of regeneration water (Dionex Anion Self Regenerating Suppressor 

Model No. ASRS®-300, 2-mm, Part No. 064555 or equivalent). Chemical 

conductivity suppressors, although not prohibited, have not been evaluated for use 

with Method 557. 

6.12.1.8 CONDUCTIVITY DETECTOR – A flow-through detector with an internal volume 

that does not introduce analyte band broadening. 

6.12.1.9 POST-COLUMN DIVERT VALVE – A two-position, six-port valve may be used. 

All wetted parts must be of polyetheretherketone (PEEK) construction. The proper 

placement of the divert valve in the sample path is illustrated in Figure 1. 

6.12.2 AUXILIARY PUMP – Pump capable of precisely delivering flow rates between 0.2 and 

0.3 mL/minute. This pump is used to mix acetonitrile into the suppressed eluent postcolumn. (Dionex high performance metering pump, Model No. AXP-MS or equivalent). 

See Figure 1 for placement of the pump in the sample path. 

6.12.3 STATIC MIXING TEE – High pressure, microbore mixing tee. (Upchurch Scientific, 

Oak Harbor, WA, Part No. U-466 or equivalent). The proper placement of the mixing tee 

in the sample path is illustrated in Figure 1. 

6.12.4 ELECTROSPRAY IONIZATION – TANDEM MASS SPECTROMETER (ESI – 

MS/MS) – The mass spectrometer interface must be able to operate in the negative-ion 

electrospray ionization mode. The system must be capable of performing MS/MS to 

produce unique product ions for the method analytes within specified retention time 

windows. Method performance data presented in Section 17 were collected using a 

Waters Quattro Premier XE ESI-MS/MS system. 

6.12.5 MS/MS DATA SYSTEM – An interfaced data system is required to acquire, store, and 

output MS data. The computer software must have the capability of processing stored 

data by recognizing a chromatographic peak within a given retention time window. The 

software must allow integration of the ion abundance of any specific ion between 

557-11
 
specified time or scan number limits. The software must be able to construct a linear 

regression or quadratic calibration curve and calculate analyte concentrations using the 

internal standard technique. 

7. REAGENTS AND STANDARDS 

7.1	 REAGENTS AND SOLVENTS – Reagent grade or better chemicals must be used. Unless 

otherwise indicated, it is intended that all reagents will conform to the specifications of the 

Committee on Analytical Reagents of the American Chemical Society (ACS), where such 

specifications are available. Other grades may be used if all the requirements of the IDC are 

met when using these reagents. 

7.1.1	 ACETONITRILE (CAS No. 75-05-8) – Post-column organic modifier. High purity, 

demonstrated to be free of analytes and interferences (Honeywell Burdick & Jackson 

Brand®, Catalog No. 015 or equivalent). 

7.1.2 METHYL-TERTIARY-BUTYL ETHER (MtBE, CAS No. 1634-04-4) – Highperformance liquid chromatography-grade (Sigma-Aldrich Catalog No. 34875 or 

equivalent). MtBE is used to prepare dilutions of neat standard materials. 

7.1.3 AMMONIUM CHLORIDE (NH4Cl, CAS No. 12125-02-9) – Method preservative. 

7.1.4 SODIUM BICARBONATE (CAS No. 144-55-8) – Laboratory Synthetic Sample Matrix 

component. 

7.1.5 SODIUM CHLORIDE (CAS No. 7647-14-5) – Laboratory Synthetic Sample Matrix 

component. 

7.1.6 SODIUM NITRATE (CAS No. 7631-99-4) – Laboratory Synthetic Sample Matrix 

component. 

7.1.7 SODIUM SULFATE (CAS No. 7757-82-6) – Laboratory Synthetic Sample Matrix 

component. 

7.2	 LABORATORY SYNTHETIC SAMPLE MATRIX (LSSM) – Prepare the LSSM at the 

concentrations listed in the table below. The required concentrations of nitrate (20 mg/L), 

bicarbonate (150 mg/L), chloride (250 mg/L), and sulfate (250 mg/L) are based on the mass 

of the anion, not the sodium salt. The NH4Cl preservative is included in the matrix. LFSSM 

QC samples (Sect. 3.13) can be prepared by diluting the Analyte PDS (Sect. 7.3.2.2) with the 

synthetic matrix solution. 

557-12
 
 

 

 

 

 

 

Compound 

Empirical 

Formula 

Salt 

(gfw)a 

Anion 

(gfw) 

Salt Mass 

(mg) H2O, L 

Conc. Stock 

(mg/L)b 

Conc. LSSM 

(mg/L)c 

Ammonium chloride 

(preservative) NH4Cl 53.49 500 1000 100 

Nitrate anion NO3 

-

 84.99 62.00 137 200 20 

Bicarbonate anion HCO3 

-

 84.01 61.02 1030 0.5 1500 150 

Chloride anion Cl­

 58.44 35.45 2060 2500 250 

Sulfate anion SO4 

-­ 142.04 96.06 1850 2500 250 a 

b 

gfw = gram formula weight of the sodium salt. 

Stock concentration = (salt mass)(gfw anion)/(gfw salt)(0.5 L). c 1:10 dilution of stock (e.g., 50 mL to 500 mL), LSSM = Laboratory Synthetic Sample Matrix. 

7.3 STANDARD SOLUTIONS – Solution concentrations listed in this section were used to 

develop this method and are included only as examples. Guidance on the storage stability of 

Primary Dilution Standards and calibration standards is provided in the applicable sections 

below. 

NOTE: When preparing aqueous solutions from MtBE stock solutions, do not add more 

than 0.5% of MtBE relative to the total water volume. MtBE has limited water solubility 

(~5%). 

7.3.1	 INTERNAL STANDARDS – This method requires four isotopically enriched internal 

standards. The following table lists the required internal standards and current sources. 

Internal Standard CASRNa Neat Materials 

Catalog No. 

Solution Standards 

(1000 μg/mL in MtBE), Cat. No. 

Monochloroacetic acid-2­

13C 1633-47-2 Sigma-Aldrich 488526 Dionex Corp. 069406 

Monobromoacetic acid-1­

13C 57858-24-9 Sigma-Aldrich 279331 Dionex Corp. 069407 

Dichloroacetic acid-2­

13C 286367-78-0 Sigma-Aldrich 485489 Dionex Corp. 069408 

Trichloroacetic acid-2­

13C Not available Custom synthesisb

 Dionex Corp. 069409 a CASRN = Chemical Abstract Registry Number. 

b Isotec, a member of the Sigma-Aldrich Group (www.sigma-aldrich.com/isotec). 

NOTE: TCAA[1-13C] may NOT be substituted for TCAA[2-13C]. TCAA[1-13C] has been 

demonstrated to convert to the native TCAA analyte in the ESI interface, theoretically via gasphase exchange with carbon dioxide-12C in the ionization region of the source. The process is 

temperature dependent (desolvation gas temperature) and was observed on all MS/MS 

platforms evaluated during method development. 

7.3.1.1 INTERNAL STANDARD STOCK STANDARDS (ISSS) (1000 μg/mL) – Prepare 

individual solutions of MCAA[2-13C], MBAA[1-13C], DCAA[2-13C], and TCAA[2­

13C] by weighing 15 mg of the solid material into a 15-mL vial and adding 15 mL of 

MtBE. Alternately, obtain the internal standards from outside suppliers as solutions 

in MtBE at 1000 μg/mL. 

7.3.1.2	 INTERNAL STANDARD PRIMARY DILUTION STANDARD (Internal Standard 

PDS) (1.0 μg/mL) – Prepare the Internal Standard PDS by adding enough of each 

ISSS to a known volume of reagent water to make the final concentration 1.0 μg/mL 

(e.g., combine 100 μL of each ISSS into 100 mL reagent water). Store the PDS in a 

557-13
 
 

 

glass vial with a PTFE/silicone septum. During method development, addition of 160 

μL of the Internal Standard PDS to each 40-mL field sample, QC sample, or 

calibration standard produced a final concentration of 4.0 μg/L. Analysts are 

permitted to use other PDS concentrations and volumes provided all field samples, 

QC samples, and calibration standards contain the same amount of internal standard, 

the concentration of the internal standard added provides adequate signal to maintain 

precision (as defined in the IDC), and the volume added has a negligible effect on the 

final concentration. The aqueous Internal Standard PDS is stable for 60 days when 

stored at 4 °C. 

7.3.2 ANALYTE STANDARD SOLUTIONS 

7.3.2.1 ANALYTE STOCK STANDARD SOLUTION (1000 μg/mL) – Obtain the 

haloacetic acid analytes listed in the table in Section 1.1 as certified solutions in 

MtBE. Obtain bromate as a certified aqueous standard. Obtain dalapon as a certified 

standard in MtBE or in methanol. Representative sources are listed in the table in 

Section 7.3.2.2. 

7.3.2.2 ANALYTE PRIMARY DILUTION SOLUTION (Analyte PDS) (1.0 μg/mL) – 

Prepare the Analyte PDS by diluting of the Analyte Stock Standard solutions into 

reagent water. Store the PDS in a glass vial with a PTFE/silicone septum. The 

Analyte PDS is used to prepare calibration standards, and to fortify QC samples with 

the method analytes. An example preparation of the Analyte PDS that was used to 

collect data presented in Section 17 is provided in the table below. 

Analyte 

Stock 

Catalogue 

Number 

Stock 

Concentration 

(μg/mL) 

Stock 

Volume 

(mL) 

Final Volume 

(mL reagent 

water) 

Analyte PDS 

Concentration 

(μg/mL) 

Bromate, 

aqueous 

Ultra Scientific 

Cat. No. ICC-010 

1000 as bromate 

anion 0.05 

50 1.0 

Dalapon in 

methanol 

Ultra Scientific 

Cat. No. HB-140 100 0.50 

Haloacetic 

acids in 

methyl-tertbutyl ether 

Restek Cat. 

No. 31896 1000 0.05 

NOTE: Storage stability of the Analyte PDS was evaluated during method 

development at a single concentration of 1.0 μg/mL. The aqueous Analyte PDS is 

stable for 60 days when stored at 4 °C. Other PDS concentrations may be selected. 

However, it is recommended that the laboratory independently assess the stability of 

the aqueous PDS to determine safe storage time. 

7.3.2.3 CALIBRATION STANDARDS – This method uses a procedural calibration 

technique. Prepare procedural calibration standards by diluting the Analyte PDS into 

reagent water containing 100 mg/L NH4Cl (preservative). A calibration range of 0.25 

to 20 μg/L is recommended as a starting point and is adequate for most drinking 

water sources. The lowest concentration calibration standard must be at or below the 

557-14
 
 

 

 

 

MRL. A constant amount of each internal standard is added to each calibration 

standard. The calibration standards may also be used as CCCs. An example of the 

dilutions (starting with the Analyte PDS) necessary to prepare the calibration 

standards is provided in the table below. 

Dilution Aliquot 

Starting 

Concentration 

(μg/L) 

Final Volume (mL, 

100 mg/L ammonium 

chloride, aqueous) 

Final 

Concentration 

(μg/L) 

Internal Standard 

Concentrationa 

(μg/L) 

2 mL Analyte PDS 1000 50 40 (WS)a

 4.0 

20 mL of WS 40 40 20 4.0 

10 mL of WS 40 40 10 4.0 

5 mL of WS 40 40 5.0 4.0 

2 mL of WS 40 40 2.0 4.0 

1 mL of WS 40 40 1.0 4.0 

4 mL of 5 μg/L std. 5.0 40 0.50 4.0 

2 mL of 5 μg/L std. 5.0 40 0.25 4.0 a

 Internal standards added at the rate of 160 μL to 40 mL by use of an Eppendorf Research Pro pipette: 

(0.16 mL)(1.0 μg/mL)/(0.040 liter) = 4.0 μg/L internal standard concentration 

b WS = working standard; not analyzed. 

NOTE: The stability of calibration standards was evaluated during method 

development at concentrations of 2.0 and 5.0 μg/L. The aqueous calibration 

standards are stable for 14 days when stored at 4 °C in glass vials with PTFE/silicone 

septa. It is recommended that the laboratory independently assess the stability of the 

aqueous calibration standards to determine safe storage time. 

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE 

The preservation requirements for Method 557 are identical to those stipulated in EPA Method 

552.3, Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid 

Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection.

5 

8.1	 SAMPLE BOTTLE PREPARATION 

8.1.1 SAMPLE CONTAINERS – Amber glass bottles with PTFE-lined screw caps and 

sufficient capacity to allow subsequent preparation of all required sample and QC 

aliquots. 

8.1.2	 ADDITION OF PRESERVATIVE – Prior to shipment to the field, add crystalline or 

granular NH4Cl to the sample containers to produce a concentration of 100 mg/L in the 

field sample. For example, a 250-mL sample requires 25 mg of NH4Cl. 

8.2	 SAMPLE COLLECTION – Grab samples must be collected in accordance with conventional 

sampling practices.6

 Fill sample bottles taking care not to flush out the ammonium chloride. 

Because the method analytes are not volatile, it is not necessary to ensure that the sample 

bottles are completely headspace-free. 

557-15
 
 

 

 

 

8.2.1	 SAMPLING FROM A TAP – When sampling from a cold water tap, remove the aerator, 

open the tap, and allow the system to flush until the water temperature has stabilized 

(approximately three to five minutes). Collect a representative sample from the flowing 

system using a beaker of appropriate size. Use this bulk sample to generate individual 

samples as needed. Invert the vials several times to mix the sample with the preservation 

reagent. 

8.3	 SAMPLE SHIPMENT AND STORAGE – Samples must be chilled during shipment and 

must not exceed 10 °C during the first 48 hours after collection. Samples must be confirmed 

to be at or below 10 °C when they are received at the laboratory. In the laboratory, samples 

must be stored at or below 6 °C and protected from light until analysis. Samples must not be 

frozen. 

8.4	 SAMPLE HOLDING TIMES – Samples must be analyzed within 14 days of collection. 

Chlorinated field samples that are preserved in accordance with the method guidance should 

not exhibit biological degradation of analytes during the allotted 14-day storage time. The 

residency time in the autosampler must be included when calculating the holding time 

from collection until analysis. 

9. QUALITY CONTROL 

9.1	 QC requirements include the IDC and ongoing QC requirements. This section describes each 

QC parameter, its required frequency, and the performance criteria that must be met in order 

to satisfy EPA quality objectives. The QC criteria discussed in the following sections are 

summarized in Section 17, Tables 11 and 12. These QC requirements are considered the 

minimum acceptable QC program. Laboratories are encouraged to institute additional QC 

practices to meet their specific needs. 

9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC) – The IDC must be successfully 

performed prior to analyzing any field samples. The IDC must be repeated if changes are 

made to analytical parameters not previously validated during the IDC, for example, selection 

of an alternate MRM transition or changing the internal standard assignment of an analyte. 

Prior to conducting the IDC, the analyst must verify proper timing of elution windows and 

divert windows (Section 10.2.5), and meet the calibration requirements outlined in Sections 

10.2 and 10.3. 

9.2.1	 DEMONSTRATION OF LOW SYSTEM BACKGROUND – Analyze an LRB. 

Confirm that the blank is free of contamination as defined in Section 9.3.1. 

NOTE: Depending on the source and purity, labeled haloacetic acid internal standards 

may contain a small percentage of the corresponding native analyte. Therefore, the 

analyst must demonstrate that the internal standards do not contain the unlabeled analytes 

at a concentration >1/3 of the MRL when added at the appropriate concentration to 

samples. An internal standard concentration of 4.0 μg/L was used during method 

development. Lower concentrations may be used providing the internal standard QC 

criteria (Sect. 9.3.4) are met. 

557-16
 
 

 

 

 

NOTE: The method must be checked for cross contamination (commonly referred to in 

the environmental laboratory community as “carryover”) by analyzing an LRB 

immediately following the highest calibration standard. If this LRB does not meet the 

criteria outlined in Section 9.3.1, then carryover is present and the cause must be 

identified and eliminated. 

9.2.2	 DEMONSTRATION OF PRECISION – Prepare and analyze seven replicate LFBs and 

seven replicate LFSSMs. Fortify these samples near the midrange of the initial 

calibration curve. The NH4Cl preservative must be added to the LFBs as described in 

Section 8.1.2. The percent relative standard deviation (RSD) of the concentrations of the 

replicate analyses must be ≤20% for all method analytes. 

Standard Deviation of Measured Concentrations % RSD =	 ×100 

Average Concentration 

9.2.3	 DEMONSTRATION OF ACCURACY – Using the same sets of replicate data generated 

for Section 9.2.2, calculate the average percent recovery. The average percent recovery 

of the replicate analyses must be within +30% of the true value. 

Average Measured Concentration % Recovery =	 ×100 

Fortified Concentration 

9.2.4	 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION – Establish a target 

concentration for the MRL based on the intended use of the method. Analyze an initial 

calibration following the procedures in Section 10.3. The lowest calibration standard 

used to establish the initial calibration (as well as the low-level CCC) must be at or below 

the concentration of the MRL. Establishing the MRL concentration too low may cause 

repeated failure of ongoing QC requirements. Confirm the MRL following the procedure 

outlined below. 

9.2.4.1	 Fortify and analyze seven replicate LFBs at or below the proposed MRL 

concentration. The LFBs must contain the method preservative as specified in 

Section 8.1.2. Calculate the mean (Mean) and standard deviation for these replicates. 

Determine the Half Range for the Prediction Interval of Results (HRPIR) using the 

equation 

HRPIR = 3.963S 

where S is the standard deviation and 3.963 is a constant value for seven replicates.1 

9.2.4.2	 Confirm that the Upper and Lower limits for the Prediction Interval of Results (PIR = 

Mean + HRPIR) meet the upper and lower recovery limits as shown below. 

The Upper PIR Limit must be ≤150 percent recovery. 

557-17
 
 

 

 

Mean + HR PIR	 × 100 ≤ 150% FortifiedConcentration 

The Lower PIR Limit must be ≥50 percent recovery. 

Mean − HR PIR	 × 100 ≥ 50% FortifiedConcentration 

9.2.4.3	 The MRL is validated if both the Upper and Lower PIR Limits meet the criteria 

described above. If these criteria are not met, the MRL has been set too low and must 

be confirmed again at a higher concentration. 

NOTE: These equations are only valid for seven replicate samples. 

9.2.5	 QUALITY CONTROL SAMPLE (QCS) – Analyze a mid-level Quality Control Sample 

(Sect. 9.3.7) to confirm the accuracy of the primary calibration standards. 

9.2.6	 DETECTION LIMIT DETERMINATION (optional) – While DL determination is not a 

specific requirement of this method, it may be required by various regulatory bodies 

associated with compliance monitoring. It is the responsibility of the laboratory to 

ascertain whether DL determination is required based upon the intended use of the data. 

Analyses for this procedure must be done over at least three days. Prepare at least seven 

replicate LFBs at a concentration estimated to be near the DL. This concentration may be 

estimated by selecting a concentration at two to five times the noise level. The NH4Cl 

preservative must be added to the samples as described in Section 8.1.2. Process the 

seven replicates through all steps of Section 11. 

NOTE: If an MRL confirmation data set meets these requirements, a DL may be 

calculated from the MRL confirmation data, and no additional analyses are necessary. 

Calculate the DL using the following equation: 

DL = S x t(n-1,1-α = 0.99) 

where 

t(n-1,1-α = 0.99) = Student's t value for the 99% confidence level with n-1 degrees of 

freedom (for seven replicate determinations, the Student’s t value 

is 3.143 at a 99% confidence level), 

n = number of replicates, and 

S = standard deviation of replicate analyses. 

NOTE: Do not subtract blank values when performing DL calculations. 

557-18
 
 

 

9.3	 ONGOING QC REQUIREMENTS – This section describes the ongoing QC elements that 

must be included when processing and analyzing field samples. Table 12 summarizes these 

requirements. 

9.3.1	 LABORATORY REAGENT BLANK (LRB) – Analyze an LRB during the IDC and 

with each Analysis Batch. The LRB must contain the NH4Cl preservative and the 

internal standards at the same concentration used to fortify all field samples and 

calibration standards. Background from method analytes or contaminants that interfere 

with the measurement of method analytes must be <1/3 the MRL. If method analytes are 

detected in the LRB at concentrations equal to or greater than this level, then all data for 

the problem analyte(s) must be considered invalid for all samples that yielded a positive 

result. Subtracting blank values from sample results is not permitted. 

NOTE: Although quantitative data below the MRL may not be accurate enough for data 

reporting, such data are useful in determining the magnitude of background interference. 

Therefore, blank contamination levels may be estimated by extrapolation when the 

concentration is below the MRL. 

9.3.2	 CONTINUING CALIBRATION CHECK (CCC) – Analyze CCC standards at the 

beginning of each Analysis Batch, after every ten field samples, and at the end of the 

Analysis Batch. See Section 10.4 for concentration requirements and acceptance criteria 

for CCCs. 

9.3.3	 LABORATORY FORTIFIED BLANK (LFB) – Because this method utilizes procedural 

calibration standards, which are fortified reagent waters, there is no difference between 

the LFB and the Continuing Calibration Check standard. Consequently, the analysis of a 

separate LFB is not required as part of the ongoing QC; however, the term “LFB” is used 

for clarity in the IDC. 

9.3.4	 INTERNAL STANDARDS (IS) – The analyst must monitor the peak areas of the 

internal standards in all injections of the Analysis Batch. The internal standard responses 

(as indicated by peak areas) for any chromatographic run must not deviate by more than 

±50% from the average areas measured during the initial calibration for the internal 

standards. If an IS area for a sample does not meet this criterion, check the 

corresponding IS area of the most recent CCC and proceed as follows. 

9.3.4.1	 If the IS criterion is met in the CCC but not the sample, reanalyze the sample in a 

subsequent Analysis Batch. If the IS area fails to meet the acceptance criterion in the 

repeat analysis, but passes in the most recent CCC, report the sample results as 

“suspect/matrix.” 

9.3.4.2	 If both the original field sample and the CCC fail the IS area criterion, take corrective 

action (e.g., Sect. 10.4.3). After servicing the instrument, re-inject the sample in a 

subsequent Analysis Batch. If the IS area fails to meet the acceptance criterion in the 

557-19
 
 

 

 

repeat analysis, but passes in the most recent CCC, report the sample results as 

“suspect/matrix.” 

9.3.5	 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – Within each Analysis 

Batch, analyze a minimum of one LFSM. The background concentrations of the analytes 

in the sample matrix must be determined in a separate aliquot and subtracted from the 

measured values in the LFSM. If various sample matrices are analyzed regularly, for 

example, drinking water processed from ground water and surface water sources, 

performance data must be collected for each source. 

9.3.5.1	 Prepare the LFSM by fortifying a sample with an appropriate amount of the Analyte 

PDS (Sect. 7.3.2.2). Generally, select a spiking concentration that is greater than or 

equal to the native concentration for most analytes. If the native concentrations of 

method analytes do not allow this criterion to be met without exceeding the 

calibration range, dilution with reagent water containing NH4Cl (100 mg/L) is 

permitted. Selecting a duplicate aliquot of a sample that has already been analyzed 

aids in the selection of an appropriate spiking level. If this is not possible, use 

historical data when selecting a fortifying concentration. 

9.3.5.2	 Calculate the percent recovery (%R) using the equation: 

(A - B) %R = ×100 

C 

where 

A = measured concentration in the fortified sample, 

B = measured concentration in the unfortified sample, and 

C = fortification concentration. 

9.3.5.3	 Recoveries for samples fortified at concentrations near or at the MRL (within a factor 

of two times the MRL concentration) must be within +50% of the true value. 

Recoveries for samples fortified at all other concentrations must be within +30% of 

the true value. If the accuracy for any analyte falls outside the designated range, and 

the laboratory performance for that analyte is shown to be in control in the CCCs, the 

recovery is judged matrix biased. Report the result for the corresponding analyte in 

the unfortified sample as “suspect/matrix.” 

NOTE: In order to obtain meaningful percent recovery results, correct the measured 

values in the LFSM and LFSMD for the native levels in the unfortified samples, even 

if the native values are less than the MRL. This situation and the LRB are the only 

permitted uses of analyte results below the MRL. 

9.3.6	 LABORATORY DUPLICATE OR LABORATORY FORTIFIED SAMPLE MATRIX 

DUPLICATE (LD or LFSMD) – Within each Analysis Batch, analyze a minimum of one 

Laboratory Duplicate or one Laboratory Fortified Sample Matrix Duplicate. If the 

method analytes are not routinely observed in field samples, analyze an LFSMD rather 

than an LD. 

557-20
 
 

 

NOTE: The variation due to the addition of internal standards must be included in the 

precision estimate. Therefore, first split the original sample and then fortify each aliquot 

with internal standards. 

9.3.6.1	 Calculate the relative percent difference (RPD) for duplicate measurements (LD1 and 

LD2) using the equation: 

LD1 − LD2 RPD = ×100 (LD1 + LD2 )/ 2 

9.3.6.2	 RPDs for Laboratory Duplicates must be ≤30%. Greater variability may be observed 

when Laboratory Duplicates have analyte concentrations that are near or at the MRL 

(within a factor of two times the MRL concentration). At these concentrations, 

Laboratory Duplicates must have RPDs that are ≤50%. If the RPD of an analyte falls 

outside the designated range, and the laboratory performance for the analyte is shown 

to be in control in the CCC, the precision is judged matrix influenced. Report the 

result for the corresponding analyte in the unfortified sample as “suspect/matrix.” 

9.3.6.3	 If an LFSMD is analyzed instead of a Laboratory Duplicate, calculate the RPD for the 

LFSM and LFSMD using the equation: 

LFSM − LFSMD

RPD = ×100 (LFSM + LFSMD)/2 

9.3.6.4	 RPDs for duplicate LFSMs must be ≤30%. Greater variability may be observed when 

the matrix is fortified at analyte concentrations near or at the MRL (within a factor of 

two times the MRL concentration). LFSMs at these concentrations must have RPDs 

that are ≤50%. If the RPD of an analyte falls outside the designated range, and the 

laboratory performance for the analyte is shown to be in control in the CCC, the 

precision is judged matrix influenced. Report the result for the corresponding analyte 

in the unfortified sample as “suspect/matrix.” 

9.3.7	 QUALITY CONTROL SAMPLE (QCS) – A QCS must be analyzed during the IDC, and 

then at least quarterly thereafter. Fortify the QCS near the midpoint of the calibration 

range. The acceptance criteria for the QCS are the same as the mid- and high-level CCCs 

(Sect. 10.4). If the accuracy for any analyte fails the recovery criterion, prepare fresh 

standard dilutions and repeat the QCS evaluation. 

9.4	 METHOD MODIFICATION QC REQUIREMENTS – The laboratory is required to perform 

the procedures in this section if chromatographic conditions and a suppression technique are 

selected which are different from those utilized to develop the method. Any proposed 

method modifications must retain the basic chromatographic elements of this new technique 

(Sect. 1.7). Examples of method modifications include alternate IC columns, an injection 

volume less than 100 uL, and additional internal standards proposed for use with the method. 

557-21
 
 

9.4.1	 Each time method modifications are made, optimize the elution gradient to accomplish 

separation of the method analytes from matrix components, and then verify elution and 

divert windows following the guidance in Section 10.2.5. Establish an acceptable initial 

calibration (Sect. 10.3). Finally, repeat the procedures of the IDC (Sect. 9.2). 

9.4.2	 The analyst is also required to evaluate and document method performance for the 

proposed modifications in real matrices that span the range of waters that the laboratory 

analyzes. This additional step is required because modifications that perform acceptably 

in the IDC, which is conducted in reagent water and synthetic matrix, could fail ongoing 

method QC requirements in real matrices. This is particularly important for methods 

subject to matrix effects, such as IC/MS-based methods. For example, a laboratory may 

routinely analyze drinking water from municipal treatment plants that process ground 

water, surface water, or a blend of surface and ground water. In this case, the method 

modification requirement could be accomplished by assessing precision and accuracy 

(Sects. 9.2.2 and 9.2.3) in a surface water with moderate to high total organic carbon 

(e.g., 2 mg/L or greater) and a hard ground water (e.g., 250 mg/L as calcium carbonate 

(CaCO3) equivalent, or greater). 

9.4.3	 The results of Sections 9.4.1 and 9.4.2 must be appropriately documented by the analyst 

and independently assessed by the laboratory’s QA officer prior to analyzing field 

samples. When implementing method modifications, it is the responsibility of the 

laboratory to closely review the results of ongoing QC, and in particular, the results 

associated with the LFSM (Sect. 9.3.5), LFSMD (Sect. 9.3.6), CCCs (Sect. 9.3.2), and 

the internal standard area counts (Sect. 9.3.4). If repeated failures are noted, the 

modification must be abandoned. 

10 CALIBRATION AND STANDARDIZATION 

10.1	 Demonstration and documentation of acceptable MS calibration and initial analyte 

calibration are required before performing the IDC and prior to analyzing field samples. 

Prior to calibration, the analyst must verify the proper timing of divert windows as described 

in Section 10.2.5. The initial calibration must be repeated each time a major instrument 

modification or maintenance is performed. 

10.2	 IC-ESI-MS/MS CALIBRATION AND OPTIMIZATION 

10.2.1 MASS CALIBRATION – Method 557 requires the monitoring of low-mass, negatively 

charged ions within nominal m/z range of 35 to 251. Calibrate the mass spectrometer 

with the calibration compounds and procedures specified by the manufacturer. Verify the 

mass assignment accuracy for each precursor ion and each product ion by comparing the 

reported centroid mass to the theoretical mass. (Pay particular attention to the chlorine 

product ion at nominal m/z 35, actual m/z 34.97.) Low signal response could result if 

mass assignments are not centered on the detected mass peaks. If the reported masses 

differ from the calculated masses and low response is observed, the standard calibration 

procedure may be inadequate for this method. Consult the MS/MS manufacturer for an 

557-22
 
 

appropriate low-mass calibration procedure. During method development, accurate mass 

assignments were achieved after calibration via direct infusion of sodium formate 

(10 nanograms per microliter) in 90:10 2-propanol:water, rather than the sodium iodide 

and cesium iodide mixture typically employed for Waters MS/MS systems. 

10.2.2 OPTIMIZING MS PARAMETERS – Each IC-ESI-MS/MS system will have different 

optimal conditions, which are influenced by the source geometry and system design. Due 

to the differences in design, follow the recommendations of the instrument manufacturer 

when tuning the instrument. During the development of this method, instrumental 

parameters were optimized for the precursor and product ions listed in Section 17, Table 

3. Because the method analytes are relatively small molecules, the selection of precursor 

and product ions is limited. However, transitions other than those listed exist, and the 

optimum choice depends on the instrument platform as noted below. 

NOTE: Several instrument platforms were investigated during method development. 

The most abundant precursor ions differed depending on the design of the ESI interface. 

In particular, the trihaloacetic acids containing bromine tend to undergo neutral loss in 

the ESI interface. For example, the precursor ions for BDCAA, CDBAA, and TBAA 

used during method development (Table 3) are 44 mass units less than the molecular ion, 

corresponding to loss of a carboxyl group (COO-

). However, using other ESI designs, 

the m/z 207 precursor ion for BDCAA was observed, which corresponds to the mass of 

the molecular ion. BDCAA and TBAA exhibited neutral loss on all ESI-MS/MS systems 

evaluated. The most abundant product ions also differed between instruments. Although 

the mass transitions in Table 3 are provided as a guide, the analyst must empirically 

determine the most abundant precursor and product ions. 

10.2.2.1 Optimize the ESI-MS/MS at the analytical flow rate (column eluent plus post-column 

acetonitrile addition) via split infusion or flow injection analysis (FIA). Use solutions 

having concentrations between 1 and 5 μg/mL of the method analytes in reagent 

water for split infusion, and solutions having concentrations between 10 and 100 μg/L 

(0.01 and 0.1 μg/mL) in reagent water for FIA. Five- or 10-μL sampling loops are 

recommended for optimizing via FIA. Because the precursor and product ions may 

be identical for some of the haloacetic acids, individual solutions of the method 

analytes are recommended for this step. 

10.2.2.2 Using Table 3 as a guide, select the most abundant precursor ion. Optimize the 

response of the precursor ion for each analyte by infusing the prepared solutions 

(Sect. 10.2.2.1) directly into mobile phase (or via FIA). Vary the ESI parameters 

(probe orientation, capillary extension, source voltages, source and desolvation 

temperatures, gas flows, etc.) and the MS parameters until optimal analyte responses 

are determined. The method analytes may have different optima, thus requiring some 

compromise. ESI-MS/MS systems are subject to drift, which can affect run-to-run 

precision. Accordingly, the optimal conditions may be those that yield adequate 

response while minimizing the potential for drift. 

557-23
 
 

 

 

10.2.2.3 Using Table 3 as a guide, select the most abundant product ion. Optimize the 

response of the product ion for each analyte by infusing the prepared solutions (Sect. 

10.2.2.1) directly into the mass spectrometer (or via FIA). Vary the MS/MS 

parameters (collision gas pressure, collision energy, etc.) until optimal analyte 

responses are determined. 

10.2.3 ION CHROMATOGRAPHY INSTRUMENT CONDITIONS – Follow the column 

manufacturer’s guidelines for calculating the elution gradient to accomplish separation of 

the method analytes from matrix components. IC operating conditions for the Dionex 

AS24 column7

 used during method development are summarized in Section 17, Table 1. 

Establish divert windows for the matrix components and elution windows for the method 

analytes per the column manufacturer’s instructions. Figure 2 presents an example of 

these windows optimized for the Dionex AS24 column. Conditions different from those 

described in this method (e.g., IC columns and mobile phases) may be used if the QC 

criteria in Sections 9.2, 9.3 and 9.4 are met, the column provides reasonable resolution of 

the method analytes, and chromatographic separation of the method analytes from matrix 

anions (chloride, carbonate, sulfate, nitrate) is achieved. 

10.2.4 ESTABLISH IC-ESI-MS/MS RETENTION TIMES AND MRM SEGMENTS – Inject a 

mid- to high-level calibration standard under optimized IC-ESI-MS/MS conditions to 

obtain the retention times of each method analyte. Divide the chromatogram into 

segments that contain one or more chromatographic peaks. For maximum sensitivity in 

subsequent MS/MS analyses, minimize the number of MRM (Sect. 3.19) transitions that 

are simultaneously monitored within each segment. Table 2 presents the assignment of 

the method analytes and internal standards into each of the three MRM windows used 

during method development. 

10.2.5 VERIFY ELUTION AND DIVERT WINDOWS FOR MATRIX ELIMINATION – 

Conduct the following tests and verify that the timing of the elution and divert windows 

meet the stated criteria. 

10.2.5.1 Stabilize the chromatographic system and analyze an LFSSM at 10 μg/L. Locate 

the first and last analyte peak in each elution window. Display the corresponding 

conductivity trace and note the peak start and peak end times for the chloride, 

carbonate, sulfate, and nitrate matrix anions. Consider a conductivity signal of 

~5 μS as the peak end (return to baseline) after elution of a matrix anion. [Refer to 

figures 4 and 5 for an example based on use of the Dionex AS24 column. For this 

column, the chloride anion elutes between elution window 1 and elution window 2. 

Carbonate, sulfate and nitrate anions elute between elution windows 2 and 3.] 

10.2.5.2 For the first analyte in each elution window, calculate a maximum time for the 

preceding valve switch: RT – (1.5)(peak width at base of the first analyte in the 

window). For the last analyte in each elution window, calculate a minimum time for 

the following valve switch: RT + (1.5)(peak width at base of the last analyte in the 

window). Verify that the valve switch times set in step 10.2.3 do not overlap the 

calculated times. 

557-24
 
 

 

 

 

NOTE: The actual valve switch times are set in accordance with the column 

manufacturer’s guidelines (Section 10.2.3). These could be wider than the start and 

end times for the elution windows calculated using the equations in this section. 

10.2.5.3 By inspection, verify that matrix peaks have returned to baseline before the 

calculated valve switch at the beginning of each elution window. By inspection, 

verify that the valve switch at the beginning of each divert window occurs before a 

matrix component begins to elute. Finally, verify that each analyte elutes entirely 

within the established elution windows. If these conditions are not met, consult the 

column manufacturer’s guidelines for adjusting the elution gradient and reset the 

timing of the divert valve accordingly. 

NOTE: Enough time should be allowed for the baseline to stabilize between the 

valve switch that begins each elution window and the appearance of the subsequent 

analyte signal. If the valve switch is too close to the analyte, the starting point of 

the analyte peak may be difficult to distinguish from the baseline disruption, 

especially for low analyte concentrations. 

10.3 INITIAL CALIBRATION 

10.3.1 CALIBRATION STANDARDS – Prepare a set of at least five calibration standards as 

described in Section 7.3.2.3. The analyte concentrations in the lowest calibration 

standard must be at or below the MRL. Field samples must be quantified using a 

calibration curve that spans the same concentration range used to collect the IDC data 

(Sect. 9.2), i.e., analysts are not permitted to use a restricted calibration range to meet the 

IDC criteria and then use a larger dynamic range during analysis of field samples. 

10.3.2 CALIBRATION – Calibrate the IC-ESI-MS/MS system using peak areas and the internal 

standard technique. Fit the calibration points with either a linear regression or quadratic 

regression (response vs. concentration). Weighting may be used. Forcing the calibration 

curve through the origin is not recommended. The MS/MS instrument used during 

method development was calibrated using inverse concentration-weighted quadratic 

curves. 

NOTE: Internal standard assignments appropriate for the Dionex AS24 column for each 

method analyte are presented in Table 3, and the mass transitions for the internal 

standards are provided in Table 4. MCAA must always be referenced to MCAA[2-13C]. 

MBAA must always be referenced to MBAA[1-13C]. Method 557 was validated with 

bromate referenced to MBAA[1-13C]; however, MCAA[2-13C] could be used if all 

requirements in the IDC are met, as well as all ongoing QC requirements. 

10.3.3 CALIBRATION ACCEPTANCE CRITERIA – Validate the initial calibration by 

calculating the concentration of the analytes for each of the analyses used to generate the 

calibration curve by use of the regression equations. Calibration points that are ≤MRL 

must calculate to be within +50% of their true value. All other calibration points must 

557-25
 
 

 

 

 

 

 

 

calculate to be within +30% of their true value. If these criteria cannot be met, the 

analyst will have difficulty meeting ongoing QC criteria. In this case, corrective action is 

recommended such as reanalyzing the calibration standards, restricting the range of 

calibration, or performing instrument maintenance. 

10.4	 CONTINUING CALIBRATION CHECKS (CCCs) – Analyze a CCC to verify the initial 

calibration at the beginning of each Analysis Batch, after every tenth field sample, and at the 

end of each Analysis Batch. The beginning CCC for each Analysis Batch must be at or 

below the MRL. This CCC verifies instrument sensitivity prior to the analysis of samples. 

Alternate subsequent CCCs between the remaining calibration levels. 

10.4.1 Verify that the absolute areas of the quantitation ions of each of the internal standards 

have not changed by more than ±50% from the average areas measured during the initial 

calibration. If this limit is exceeded, verify that the background conductivity is in control 

following the guidance in Section 11.3.2. If the background conductivity is normal, 

remedial action may necessary (Sect. 10.4.3). 

10.4.2 Calculate the concentration of each analyte in the CCC. The CCC fortified at ≤MRL 

must calculate to be within +50% of its true value. CCCs fortified at all other levels must 

calculate to be within +30%. If these limits are exceeded, then all data for the failed 

analytes must be considered invalid. Any field samples analyzed since the last acceptable 

CCC that are still within holding time must be reanalyzed after an acceptable calibration 

has been restored. 

10.4.3 REMEDIAL ACTION – Failure to meet CCC QC performance criteria requires remedial 

action. Acceptable method performance may be restored simply by flushing the column 

at the highest eluent concentration in the gradient. Following this and other minor 

remedial action, check the calibration with a mid-level CCC and a CCC at the MRL, or 

alternatively recalibrate according to Section 10.3. If internal standard and calibration 

failures persist, maintenance may be required, such as servicing the ESI-MS/MS system 

and replacing IC columns. These later measures constitute major maintenance, and the 

analyst must return to the initial calibration step (Sect. 10.3) and verify sensitivity by 

analyzing a CCC at or below the MRL. 

11. PROCEDURE 

11.1	 This section describes the procedures for sample preparation and analysis. Important aspects 

of this analytical procedure include proper sample collection and storage (Sect. 8), ensuring 

that the instrument is properly calibrated (Sect. 10), and that all required QC elements are 

included (Sect. 9). 

11.2	 SAMPLE PREPARATION 

11.2.1 All field and QC samples must contain the preservative listed in Section 8.1.2, including 

the LRB. In the laboratory, maintain field samples, QC samples, and calibration 

557-26
 
 

 

standards at or below 6 °C at all times, including the time these are resident in the 

autosampler awaiting injection. 

11.2.2 Do not filter the samples. Add an appropriate volume of the Internal Standard PDS (Sect. 

7.3.1.2) to a known volume of sample, cap, and mix well. The concentration of the 

internal standards must be the same in the samples as in the calibration standards. 

Transfer an aliquot of each field or QC sample to an autosampler vial. For example, 

weigh 40 mL of sample into a 40-mL VOA vial using a top loading balance and a 

disposable, glass pipette. Add 160 uL of the internal standard PDS (1.0 μg/mL) to 

achieve a concentration of 4.0 μg/L in the sample. Mix well and transfer 1.5 mL to an 

autosampler vial by use a disposable pipette. 

11.3	 SAMPLE ANALYSIS 

11.3.1 Establish IC-ESI-MS/MS operating conditions per the guidance in Section 10.2. 

11.3.2 Flush the column at the highest eluent concentration in the gradient for at least 15 

minutes prior to beginning each analysis sequence. This step is especially important for 

minimizing background conductivity if the column has been installed in the system and 

held at the starting eluent concentration for extended periods. 

NOTE: During method development, the background conductivity ranged from 0.3 to 

2.2 microsiemens (μS). If an internal standard or analyte area response is low due to high 

background conductivity, flush the column at the maximum eluent concentration in the 

gradient and observe the conductivity signal until the background stabilizes at less than 

2.5 μS. Also, ensure that the suppressor is functioning properly or replace the suppressor 

to troubleshoot the problem. Occasional overnight flushing of the column will minimize 

the occurrence of high background conductivity. 

11.3.3 VERIFY ELUTION AND DIVERT WINDOWS - Analyze Laboratory Synthetic Sample 

Matrix fortified at 10 μg/L. Verify the elution and divert windows as specified in Section 

10.2.5. This verification must be done prior to beginning each Analysis Batch. 

11.3.4 THE ANALYSIS BATCH – Establish a valid initial calibration following the procedures 

outlined in Section 10.3 and confirm that the calibration is valid by analyzing a CCC at or 

below the MRL as described in Section 10.4. Alternately, verify that an existing 

calibration, established for a previous Analysis Batch, is still valid by analyzing a CCC at 

or below the MRL. Next, analyze an LRB. Continue the Analysis Batch by analyzing 

aliquots of field and QC samples at appropriate frequencies (Section 9.3), employing the 

optimized conditions used to acquire the initial calibration. Analyze a mid- or high-level 

CCC after every ten field samples and at the end each Analysis Batch. 

NOTE: Each Analysis Batch must begin with the analysis of a CCC at or below the 

MRL for each analyte that the laboratory intends to report, followed by the analysis of an 

LRB. This is true whether or not an initial calibration is analyzed. After 20 field samples 

the low-level CCC and the LRB must be repeated to begin a new Analysis Batch. The 

557-27
 
acquisition start time of the mid-level CCC at the end of the Analysis Batch must be 

within 30 hours of the acquisition start time of the low-level CCC at the beginning of the 

Analysis Batch. Do not count QC samples (LRBs, LDs, LFSMs, LFSMDs) when 

calculating the frequency of CCCs that are required during an Analysis Batch. 

12. DATA ANALYSIS AND CALCULATIONS 

12.1	 Establish an appropriate retention time window for each analyte to identify them in QC and 

field sample chromatograms. Base this assignment on measurements of actual retention time 

variation for each compound in standard solutions over the course of time. The suggested 

variation is plus or minus three times the standard deviation of the retention time for each 

compound for a series of injections. The injections from the initial calibration and from the 

IDC (Sect. 9.2) may be used to calculate the retention time window. However, the 

experience of the analyst should weigh heavily on the determination of an appropriate range. 

12.2	 At the conclusion of data acquisition, use the same software settings established during the 

calibration procedure to identify peaks of interest in the predetermined retention time 

windows. Confirm the identify of each analyte by comparison of its retention time with that 

of the corresponding analyte peak in an initial calibration standard or CCC. 

12.3	 Calculate analyte concentrations using the multipoint calibration established in Section 10.3. 

Report only those values that fall between the MRL and the highest calibration standard. 

Samples with analyte responses that exceed the highest calibration standard require dilution 

and reanalysis (Sect. 12.7). 

NOTE: In validating this method, concentrations were calculated using the product ions 

listed in Table 3 of Section 17. Other ions may be selected at the discretion of the analyst as 

discussed in Section 10.2.2. 

12.4	 Calculations must use all available digits of precision, but final reported concentrations 

should be rounded to an appropriate number of significant figures (one digit of uncertainty), 

typically two, and not more than three significant figures. 

12.5	 Prior to reporting the data, the chromatograms must be reviewed for any incorrect peak 

identifications or improper integration. 

12.6	 Prior to reporting data, the laboratory is responsible for ensuring that QC requirements have 

been met and that any appropriate qualifier is assigned. 

12.7	 EXCEEDING THE CALIBRATION RANGE – The analyst must not extrapolate beyond the 

established calibration range. If an analyte result exceeds the range of the initial calibration 

curve, the sample may be diluted using reagent water containing 100 mg/L NH4Cl with the 

appropriate amount of internal standard added to match the original level. Re-inject the 

diluted sample. Incorporate the dilution factor into final concentration calculations. The 

resulting data must be annotated as a dilution, and the reported MRLs must reflect the 

dilution factor. 

557-28
 
13. METHOD PERFORMANCE 

13.1	 PRECISION, ACCURACY, AND DETECTION LIMITS – The method performance data 

presented in Section 17 were collected using the IC conditions listed in Table 1 and the 

Waters Quattro Premier XE ESI-MS/MS system. ESI-MS/MS conditions for the Waters 

system are presented in Table 2. Tables 3 and 4 list the mass transitions for each analyte and 

internal standard, internal standard assignments, and observed retention times associated with 

the method performance results. LCMRLs and DLs are presented in Tables 5 and 6. Single 

laboratory precision and accuracy data are presented for four water matrices: reagent water 

(Table 7), LSSM (Table 8), chlorinated (finished) ground water (Table 9), and chlorinated 

(finished) surface water (Table 10). Figure 1 depicts the post-column sample path as 

previously cited in this document (Sect. 6.12). Figures 2 through 4 are chromatograms of the 

method analytes in reagent water, drinking water, and LSSM obtained under the conditions 

employed during method development. Figure 4 was acquired with the inclusion of mass 

transitions for the chlorite and chlorate anions to mark their position in the chromatogram 

relative to the method analytes. Figure 5 is a corresponding conductivity trace for the analyte 

chromatogram presented in Figure 4 showing the location of matrix anions, chlorite anion, 

and chlorate anion. 

13.2	 SECOND LABORATORY EVALUATION – The performance of this method was 

demonstrated by a second laboratory using an API 4000 triple quadrupole mass spectrometer 

(Applied Biosystems, Foster City, CA) with results similar to those reported in Section 17. 

The authors wish to acknowledge the Southern Nevada Water Authority (Las Vegas, NV) for 

their contribution to the method development effort. 

14. POLLUTION PREVENTION 

14.1	 For information about pollution prevention that may be applicable to laboratory operations, 

consult “Less is Better: Laboratory Chemical Management for Waste Reduction” available 

from the American Chemical Society’s Department of Government Relations and Science 

Policy, 1155 16th Street N.W., Washington, D.C., 20036, or online at 

http://www.ups.edu/x7432.xml. 

15. WASTE MANAGEMENT 

15.1	 The analytical procedures described in this method generate relatively small amounts of 

waste since only small amounts of reagents and solvents are used. The matrix of concern is 

finished drinking water. However, the Agency requires that laboratory waste management 

practices be conducted consistent with all applicable rules and regulations, and that 

laboratories protect the air, water, and land by minimizing and controlling all releases from 

fume hoods and bench operations. In addition, compliance is required with any sewage 

discharge permits and regulations, particularly the hazardous waste identification rules and 

land disposal restrictions. For further information on waste management, see the 

publications of the American Chemical Society’s Laboratory Environment, Health & Safety 

Task Force on the Internet at http://membership.acs.org/c/ccs/publications.htm. Additional 

557-29
 
waste management information can be found in “Laboratory Waste Minimization and 

Pollution Prevention,” Copyright © 1996 Battelle Seattle Research Center, which can be 

located at http://www.p2pays.org/ref/01/text/00779/ch05.htm. 

16. REFERENCES 

1. Winslow, S. D.; Pepich, B. V.; Martin, J. J.; Hallberg, G. R.; Munch D. J.; Frebis, C. P.; Hedrick, E. 

J.; Krop, R. A. Statistical Procedures for Determination and Verification of Minimum Reporting 

Levels for Drinking Water Methods. Environ. Sci. Technol. 2006; 40, 281-288. 

2. Glaser, J.A.; Foerst, D.L.; McKee, G.D.; Quave, S.A.; Budde, W.L. Trace Analyses for 

Wastewaters. Environ. Sci. Technol. 1981; 15, 1426-1435. 

3. Occupational Exposures to Hazardous Chemicals in Laboratories; 29 CFR 1910.1450, Occupational 

Safety and Health Administration, 1990. 

4. Safety in Academic Chemistry Laboratories; American Chemical Society Publication, Committee on 

Chemical Safety, 7th Edition: Washington, D.C., 2003. 

5. Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid 

Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection; U.S. 

EPA Method 552.3, EPA 815-B-03-002. 

6. Standard Practice for Sampling Water from Closed Conduits; ASTM Annual Book of Standards, 

Section 11, Volume 11.01, D3370-08; American Society for Testing and Materials: Philadelphia, 

PA, 2008. 

7. Application Note 217, Dionex Corp., Sunnyvale, CA. 

557-30
 
17. TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA 

TABLE 1.	 ION CHROMATOGRAPHIC CONDITIONS USED TO COLLECT METHOD 

PERFORMANCE DATA 

Parameter Conditionsa 

Column Dionex IonPac® AS24 250 mm x 2 mm i.d. 

Precolumn Dionex IonPac® AG24 50 mm x 2 mm i.d. 

Column compartment 

temperature 15 oC Autosampler tray 

temperature 4 oC 

Hydroxide gradient 7 mM for -1 to16.8 min, then 18 mM for 16.8 to 34.2 min, then 60 mM 

for 34.4 to 51.2 min, then 7 mM for 51.4 to 56 min 

Eluent flow rate 0.30 mL/min 

Post-column solvent 100% acetonitrile at 0.2 mL/min 

Suppressor Dionex ASRS®300 2 mm, external water mode 

Matrix diversion divert 

windows 0 to 8 min, 16.5 to 21.2 min, and 33 to 39.2 min 

Sample volume 100-μL loop 

a The chromatograms presented in Figures 2, 3, 4, and 5 were obtained under these conditions. 

TABLE 2. WATERS QUATTRO PREMIER XE ACQUISITION CONDITIONS USED 

TO COLLECT METHOD PERFORMANCE DATAa 

Analyte 

Transition 

(m/z) 

Dwell 

(seconds) Periods 

Cone 

(V) 

Collision 

Energy (V) 

ISb

: Monochloroacetic acid-2-13C 94/35 0.4 

MRM 

Window 1 

-15 -8 

Monochloroacetic acid 93/35 1.2 -15 -8 

IS: Monobromoacetic acid-1-13C 138/79 0.4 -15 -10 

Monobromoacetic acid 137/79 0.4 -15 -10 

Bromate 127/111 0.4 -25 -18 

Dalapon 141/97 0.5 

MRM 

Window 2 

-18 -8 

IS: Dichloroacetic acid-2-13C 128/84 0.5 -17 -10 

Dichloroacetic acid 127/83 0.5 -17 -10 

Bromochloroacetic acid 173/129 0.5 -17 -10 

Dibromoacetic acid 217/173 0.5 -18 -12 

IS: Trichloroacetic acid-2-13C 162/118 0.5 

MRM 

Window 3 

-16 -8 

Trichloroacetic acid 161/117 

163/119 0.5 -16 -8 

Bromodichloroacetic acid 163/81 1.0 -25 -10 

Chlorodibromoacetic acid 207/79 1.0 -28 -10 

Tribromoacetic acid 251/79 1.0 -28 -12 

a Source block: 120 °C, desolvation gas: 350 °C @ 940 liters/hour, capillary: -2.8 V, collision pressure: 5.5x10-3 

torr (0.15 flow @ 7 psig), cone flow: 100 liters/hour, extractor: -3 V, RF lens: -0.5 V, acetonitrile flow rate: 0.2 

mL/min. 

b IS = internal standard. 

557-31 
 

TABLE 3. IC-ESI-MS/MS ANALYTE RETENTION TIMES, PRECURSOR AND PRODUCT 

IONS 

Analyte 

Retention Timea 

(min) 

Internal Standard 

Assignment Precursor Product 

Monochloroacetic acid 12.62 MCAA[2-13C] 93 35 

Monobromoacetic acid 14.05 MBAA[1-13C] 137 79 

Bromate 14.93 MBAA[1-13C] 127 111 

Dalapon 23.33 DCAA[2-13C] 141 97 

Dichloroacetic acid 24.26 DCAA[2-13C] 127 83 

Bromochloroacetic acid 26.16 DCAA[2-13C] 173 129 

Dibromoacetic acid 28.89 DCAA[2-13C] 217 173 

Trichloroacetic acid 41.08 TCAA[2-13C] 161 117 

Trichloroacetic acid (alternate) TCAA[2-13C] 163 119 

Bromodichloroacetic acid 42.89 TCAA[2-13C] 163 81 

Chlorodibromoacetic acid 45.50 TCAA[2-13C] 207 79 

Tribromoacetic acid 49.22 TCAA[2-13C] 251 79 a Dionex AS24 column (used to collect method performance data). 

TABLE 4. IC-ESI-MS/MS INTERNAL STANDARD RETENTION TIMES, 

PRECURSOR AND PRODUCT IONS 

,nternal 6tandard 

Retention Timea 

(minutes) Precursor Product 

Monochloroacetic acid-2-13C 12.56 94 35 

Monobromoacetic acid-1-13C 14.05 138 79 

Dichloroacetic acid-2-13C 24.21 128 84 

Trichloroacetic acid-2-13C 41.08 162 118 

a Dionex AS24 column (used to collect method performance data). 

557-32
 
TABLE 5. IC-ESI-MS/MS LOWEST CONCENTRATION MINIMUM REPORTING LEVEL 

(LCMRL) 

Analyte LCMRL Fortification Levels (μg/L) 

Calculated LCMRL 

(μg/L) 

Monochloroacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.58 

Monobromoacetic acid 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 

2.0 0.19 

Bromate 0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 

1.75, 2.0 0.042 

Dalapon 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.41 

Dichloroacetic acid 0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 

1.75, 2.0 0.13 

Bromochloroacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.16 

Dibromoacetic acid 0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 

1.75, 2.0 0.062 

Trichloroacetic acid – m/z 163/119 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.25 

Bromodichloroacetic acid 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 

2.0 0.19 

Chlorodibromoacetic acid 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 

2.0 0.080 

Tribromoacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.27 

TABLE 6. IC-ESI-MS/MS DETECTION LIMITS (DL)a 

Analyte Fortification Level (μg/L) Calculated DL (μg/L) 

Monochloroacetic acid 0.25 0.20 

Monobromoacetic acid 0.10 0.064 

Bromate 0.025 0.020 

Dalapon 0.25 0.038 

Dichloroacetic acid 0.10 0.055 

Bromochloroacetic acid 0.25 0.11 

Dibromoacetic acid 0.025 0.015 

Trichloroacetic acid – m/z 163/119 0.10 0.090 

Bromodichloroacetic acid 0.050 0.050 

Chlorodibromoacetic acid 0.10 0.041 

Tribromoacetic acid 0.25 0.067 

a DLs calculated using data acquired over the course of three days (n=7 sample replicates). 

557-33
 
TABLE 7. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES 

FORTIFIED AT 1.0 AND 15 μg/L IN REAGENT WATER 

Analyte 

Fortified Conc. = 1.0 μg/L 

(n=7) 

Fortified Conc. = 15 μg/L 

(n=8) 

Mean % 

Recovery 

Relative Standard 

Deviation 

Mean % 

Recovery 

Relative Standard 

Deviation 

Monochloroacetic acid 101 3.5 101 1.7 

Monobromoacetic acid 97.5 3.7 99.8 1.8 

Bromate 93.3 2.4 104 7.8 

Dalapon 97.4 4.7 100 3.3 

Dichloroacetic acid 109 2.6 97.0 6.5 

Bromochloroacetic acid 103 2.9 107 4.4 

Dibromoacetic acid 104 9.0 111 6.7 

Trichloroacetic acid – m/z 163/119 99.1 2.3 99.8 3.2 

Bromodichloroacetic acid 105 3.7 97.7 2.2 

Chlorodibromoacetic acid 90.4 5.9 103 5.4 

Tribromoacetic acid 101 5.3 98.9 3.0 

TABLE 8. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES 

FORTIFIED AT 1.0 AND 15 μg/L IN SYNTHETIC SAMPLE MATRIX 

Analyte 

Fortified Conc. = 1.0 μg/L 

(n=8) 

Fortified Conc. = 15 μg/L 

(n=8) 

Mean % 

Recovery 

Relative Standard 

Deviation 

Mean % 

Recovery 

Relative Standard 

Deviation 

Monochloroacetic acid 109 4.8 101 4.1 

Monobromoacetic acid 97.2 5.3 99.7 4.6 

Bromate 117 11 109 11 

Dalapon 113 4.5 93.2 6.6 

Dichloroacetic acid 89.9 9.3 90.9 8.7 

Bromochloroacetic acid 84.9 9.3 82.8 10 

Dibromoacetic acid 91.0 14 84.5 10 

Trichloroacetic acid – m/z 163/119 107 5.4 101 1.1 

Bromodichloroacetic acid 91.6 4.7 91.0 4.1 

Chlorodibromoacetic acid 98.8 7.2 97.6 6.2 

Tribromoacetic acid 94.0 5.4 97.6 2.5 

557-34
 
 

TABLE 9. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES 

FORTIFIED AT 2.5 AND 10 μg/L IN CHLORINATED GROUND WATERa 

Analyte 

Native 

Conc., 

μg/L 

(n=6) 

Fortified Conc. = 2.5 μg/L 

(n=8) 

Fortified Conc. = 10 μg/L 

(n=8) 

Mean % 

Recoveryb Relative Standard 

Deviation 

Mean % 

Recoveryb Relative Standard Deviation 

Monochloroacetic acid 0.57 95.9 4.7 99.6 5.2 

Monobromoacetic acid 0.41 101 2.1 101 1.8 

Bromate 0.56 107 7.3 102 4.8 

Dalapon 0.37 95.5 3.1 98.5 3.0 

Dichloroacetic acid 4.3 99.7 6.2 106 1.7 

Bromochloroacetic acid 3.4 95.2 5.6 93.5 3.1 

Dibromoacetic acid 2.0 95.2 8.1 99.3 6.2 

Trichloroacetic acid – m/z 163/119 2.6 101 1.8 102 2.8 

Bromodichloroacetic acid 2.6 91.2 2.0 99.0 3.6 

Chlorodibromoacetic acid 1.7 103 3.6 102 7.2 

Tribromoacetic acid 0.24 97.6 1.9 95.8 1.9 

a Ground water physical parameters: pH = 7.45; total hardness = 308 milligrams/liter (mg/L) (as CaCO3); free chlorine = 

0.94 mg/L. 

b Recoveries corrected for native levels in the unfortified matrix. 

TABLE 10.	 IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES 

FORTIFIED AT 2.5 AND 8.0 μg/L IN CHLORINATED SURFACE WATERa 

Analyte 

Native 

Conc., 

μg/L 

(n=6) 

Fortified Conc. = 2.5 μg/L 

(n=8) 

Fortified Conc. = 8.0 μg/L 

(n=7) 

Mean % 

Recoveryb Relative Standard 

Deviation 

Mean % 

Recoveryb Relative Standard Deviation 

Monochloroacetic acid 2.6 97.9 3.5 98.8 3.0 

Monobromoacetic acid 0.66 99.3 1.4 101 1.6 

Bromate 0.85 99.0 8.8 103 10 

Dalapon 0.72 97.8 3.8 96.3 4.8 

Dichloroacetic acid 15 79.6 6.3 80.0 6.0 

Bromochloroacetic acid 6.4 87.2 9.0 90.2 9.2 

Dibromoacetic acid 1.6 106 10 95.8 6.0 

Trichloroacetic acid – m/z 163/119 11 95.6 2.5 97.1 1.4 

Bromodichloroacetic acid 4.7 99.9 4.6 97.9 4.9 

Chlorodibromoacetic acid 1.2 102 5.9 102 11 

Tribromoacetic acid 0.081 99.5 3.9 103 4.7 

a Surface water physical parameters: pH = 7.43; total hardness = 154 milligrams/liter (mg/L) (as CaCO3); free chlorine = 

2.7 mg/L; total chlorine = 3.7 mg/L. 

b Recoveries corrected for native levels in the unfortified matrix. 

557-35 
 

TABLE 11. INITIAL DEMONSTRATION OF CAPABILITY (IDC) QUALITY CONTROL 

REQUIREMENTS 

Method 

Reference Requirement Specification and Frequency Acceptance Criteria 

Section 

9.2.1 

Demonstration of 

low system 

background 

Analyze a Laboratory Reagent 

Blank (LRB) prior to any other 

Initial IDC steps. 

Demonstrate that all method analytes 

are <1/3 of the Minimum Reporting 

Level (MRL) and that possible 

interferences from reagents and 

glassware do not prevent the 

identification and quantitation of 

method analytes. 

Section 

9.2.1 

Test for system 

carryover 

Analyze an LRB after the high 

calibration standard during the IDC 

calibration. 

Demonstrate that the method analytes 

are <1/3 of the MRL. 

Section 

9.2.2 

Demonstration of 

precision 

Analyze 7 replicate Laboratory 

Fortified Blanks (LFBs) and 7 

Laboratory Fortified Synthetic 

Sample Matrix samples (LFSSMs) 

fortified near the midrange 

concentration. 

Percent relative standard deviation 

must be ≤20%. 

Section 

9.2.3 

Demonstration of 

accuracy 

Calculate average recovery for 

replicates used in Section 9.2.2. 

Mean recovery within +30% of the true 

value. 

Section 

9.2.4 

MRL 

confirmation 

Fortify and analyze 7 replicate LFBs 

at the proposed MRL concentration. 

Confirm that the Upper Prediction 

Interval of Results (PIR) and Lower 

PIR (Sect. 9.2.4.2) meet the 

recovery criteria. 

Upper PIR ≤ 150% 

Lower PIR ≥ 50% 

Section 

9.2.5 

Quality Control 

Sample (QCS) Analyze mid-level QCS. Results must be within +30% of the 

true value. 

557-36
 
 

 

 

TABLE 12. ONGOING QUALITY CONTROL REQUIREMENTS
 

Method 

Reference Requirement Specification and Frequency Acceptance Criteria 

Section 

11.3.3 

Verify divert 

windows 

Analyze a Laboratory Fortified 

Synthetic Sample Matrix (LFSSM) 

prior to each Analysis Batch. 

See Section 10.2.5 for acceptance 

criteria. 

Section 

10.3 Initial calibration 

Use the internal standard calibration technique to generate a 

linear or quadratic calibration 

curve. Use at least five standard 

concentrations. Validate the calibration curve as described in 

Section 10.3.3. 

When each calibration standard is 

calculated as an unknown using the 

regression equations, the lowest 

level standard must be within +50% 

of the true value. All other points 

must be within +30% of the true 

value. 

Section 

9.3.1 

Laboratory Reagent 

Blank (LRB) 

Analyze one LRB with each 

Analysis Batch. 

Demonstrate that all method analytes are below 1/3 the Minimum 

Reporting Level (MRL), and that 

possible interference from reagents 

and glassware do not prevent identification and quantitation of method 

analytes. 

Section 

10.4 

Continuing Calibration Check (CCC) 

Verify initial calibration by analyzing a low-level CCC at the 

beginning of each Analysis Batch. 

Subsequent CCCs are required 

after every 10 field samples, and 

after the last field sample in a 

batch. 

The lowest level CCC must be 

within +50% of the true value. All 

other points must be within +30% of 

the true value. 

Results for field samples that are not 

bracketed by acceptable CCCs are 

invalid. 

Section 

9.3.4 Internal standard (IS) 

Isotopically labeled internal 

standards are added to all standards 

and samples. 

Peak area counts for each IS must be 

within ±50% of the average peak 

areas in the initial calibration. 

Section 

9.3.5 

Laboratory Fortified 

Sample Matrix 

(LFSM) 

Analyze one LFSM per Analysis 

Batch. Fortify the LFSM with 

method analytes at a concentration 

greater than the native 

concentrations of most analytes. 

Calculate LFSM recoveries. 

For LFSMs fortified at concentrations <2 x MRL, the result must 

be within +50% of the true value. 

At concentrations greater than the 2 

x MRL, the result must be within 

+30% of the true value. 

Section 

9.3.6 

Laboratory Fortified 

Sample Matrix Duplicate (LFSMD) or 

Laboratory Duplicate 

(LD) 

Analyze at least one LFSMD or 

LD with each Analysis Batch. 

For LFSMDs or LDs, relative 

percent differences must be ≤30%. 

(≤50% if concentration <2 x MRL.) 

Section 

9.3.7 

Quality Control 

Sample (QCS) 

Analyze mid-level QCS at least 

quarterly. 

Results must be +30% of the true 

value. 

557-37
 
Figure 1. Divert valve placement in sample path. 

557-38
 
Figure 2. Dionex AS24 column: procedural calibration standard (5 μg/L). 

557-39
Figure 3. Dionex AS24 column: tap water fortified at 8 μg/L. 

557-40
Figure 4. Dionex AS24 column: synthetic sample matrix fortified at 5 μg/L plus chlorite (1 mg/L) and ch

557-41 
Figure 5. Dionex AS24 column: conductivity trace, synthetic sample matrix plus chlorite (1 mg/L) and c

557-42