EPA Document # EPA 815-R-03-007
METHOD 326.0 DETERMINATION OF INORGANIC OXYHALIDE DISINFECTION
BY-PRODUCTS IN DRINKING WATER USING ION
CHROMATOGRAPHY INCORPORATING THE ADDITION OF A
SUPPRESSOR ACIDIFIED POSTCOLUMN REAGENT FOR TRACE
BROMATE ANALYSIS
Revision 1.0
June 2002
Herbert P. Wagner and Barry V. Pepich, Shaw Environmental Inc
Daniel P. Hautman and David J. Munch, US EPA, Office of Ground Water and Drinking
Water
E. Salhi and Urs von Gunten, Swiss Federal Institute for Environmental Science and
Technology, EAWAG, CH-8600, Dubendorf, Switzerland
TECHNICAL SUPPORT CENTER
OFFICE OF GROUND WATER AND DRINKING WATER
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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METHOD 326.0
DETERMINATION OF INORGANIC OXYHALIDE DISINFECTION BY-PRODUCTS
IN DRINKING WATER USING ION CHROMATOGRAPHY INCORPORATING THE
ADDITION OF A SUPPRESSOR ACIDIFIED POSTCOLUMN REAGENT FOR TRACE
BROMATE ANALYSIS
1. SCOPE AND APPLICATION
1.1 This method covers the determination of inorganic oxyhalide disinfection by-
product anions in reagent water, surface water, ground water, and finished
drinking water. In addition, bromide can be accurately determined in source or
raw water and it has been included due to its critical role as a disinfection by-
product precursor. Bromide concentration in finished water can differ due to
numerous variables which can influence the concentration. Since this method,
prior to the addition of the postcolumn reagent (PCR), employs the same hardware
as EPA Method 300.1(1), the analysis of the common anions (using EPA Method
300.1, Part A1) can be performed using this instrument setup with the postcolumn
hardware attached but "off-line" and with the appropriate smaller sample loop.
Inorganic Disinfection By-products by Conductivity Detection
Analyte
Bromate
Bromide
Chorite
Chloride
Comments
report
report
report
range
report
range
values
values
values
values
> 15.0 ug/L
from source
> Minimum
> Minimum
*
and raw waters only
Reporting Level in calibration
Reporting Level in calibration
Inorganic Disinfection By-products by Absorbance Detection
Analyte
Bromate
Comments
report
values
> Minimum Reporting Level to 15.0 ug/L *
* the concentrations reported for bromate assume both detectors to be running
simultaneously.
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1.2 The single laboratory reagent water Detection Limits (Sect. 3.15) for the above
analytes are listed in Table 1. The Detection Limit 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 Detection Limit differs from, and is
lower than the Minimum Reporting Level (MRL) (Sect. 3.16). The Detection
Limit for a specific matrix may differ from those listed, depending upon the
nature of the sample and the specific instrumentation employed.
1.2.1 In order to achieve comparable detection limits on the conductivity
detector, an ion chromatographic system must utilize suppressed
conductivity detection, be properly maintained and must be capable of
yielding a baseline with no more than 5 nanosiemen (nS) noise/drift per
minute of monitored response over the background conductivity.
1.2.2 In order to achieve acceptable detection limits on the postcolumn
absorbance detector, the postcolumn reagent must be delivered
pneumatically and some form of software signal filtering or smoothing of
the absorbance signal from the absorbance detector must be incorporated.
1.3 This method is recommended for use only by or under the supervision of analysts
experienced in the use of ion chromatography and in the interpretation of the
resulting ion chromatograms.
1.4 When this method is used to analyze unfamiliar samples for any of the above
anions, anion identification should be supported by the use of a fortified sample
matrix covering the anions of interest. The fortification procedure is described in
Section 9.8.
1.5 Users of the method must demonstrate the ability to generate acceptable results
with this method, using the procedures described in Section 9.
2. SUMMARY OF METHOD
2.1 The development of this method was based upon the work of several investigators
as summarised elsewhere.(3) A volume of sample, approximately 225 |_iL (see
Note), is introduced into an ion chromatograph (1C) which includes a guard
column, analytical column, suppressor devices, conductivity detector, a
postcolumn reagent delivery system (pneumatically controlled), a heated
postcolumn reaction coil, and a ultraviolet/visible (UV/Vis) absorbance detector
(see Figure 1). After separation and suppression of the eluent, the oxyhalide
anions chlorite, chlorate, bromate >15.0 |-ig/L and bromide are measured using
conductivity detection. To facilitate low-level detection of bromate, the
suppressed effluent from the conductivity detector is combined with an acidic
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solution of potassium iodide containing a catalytic amount of molybdenum VI.
The mixture is heated at 80° C (to facilitate complete reaction) where the bromate
reacts with iodide to form the tri-iodide ion which is measured by its UV
absorption at 352 nm.
NOTE: A 225 uL sample loop can be made using approximately 111 cm (44
inches) of 0.02 inch i.d. PEEK tubing. The volume should be verified to be
within 5% by weighing the sample loop empty, filling the loop with deionized
water and re-weighing the loop assuming the density of water is 1 mg/uL.
3. DEFINITIONS
3.1 ANALYSIS BATCH - A sequence of samples, which are analyzed within a 30
hour period and include no more than 20 field samples. An 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 Standards (CCCs)
• Laboratory Fortified Blank (LFB)
• Laboratory Fortified Sample Matrix (LFSM), and
• Either a Field Duplicate (FD) or a Laboratory Fortified Sample
Martix Duplicate (LFSMD).
3.2 SURROGATE ANALYTE (SUR) - A pure analyte, which chemically resembles
target analytes and is extremely unlikely to be found in any sample. This analyte
is added to a sample aliquot in known amount(s) before filtration or other
processing and is measured with the same procedures used to measure other
sample components. The purpose of the SUR is to monitor method performance
with each sample.
3.3 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water or
other blank matrix that is treated exactly as a sample including exposure to all
glassware, equipment, solvents and reagents, sample preservatives, and
surrogates that are used in the analysis batch. The LRB is used to determine if
method analytes or other interferences are present in the laboratory environment,
the reagents, or the apparatus.
3.4 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water or
other blank matrix to which known quantities of the method analytes and all the
preservation compounds are added in the laboratory. The LFB is analyzed exactly
like a sample, and its purpose is to determine whether the methodology is in
control, and whether the laboratory is capable of making accurate and precise
measurements.
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3.5 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) - An aliquot of an
environmental sample to which known quantities of the method analytes and all
the preservation compounds are added in the laboratory. The LFSM is analyzed
exactly like a sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background concentrations of the
analytes in the sample matrix must be determined in a separate aliquot and the
measured values in the LFSM corrected for background concentrations.
3.6 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) - A
second aliquot of the field sample used to prepare the LFSM fortified, processed
and analyzed identically. The LFSMD is used instead of the Field Duplicate to
access method precision when the occurrence of target analytes is low.
3.7 LABORATORY DUPLICATES (LD1 and LD2) - Two aliquots of the same
sample taken in the laboratory and analyzed separately with identical procedures.
Analyses of LD1 and LD2 indicate precision associated with laboratory
procedures, but not with sample collection, preservation, or storage procedures.
3.8 FIELD DUPLICATES (FD1 and FD2) - Two separate samples collected at the
same time and place under identical circumstances, and treated exactly the same
throughout field and laboratory procedures. Analyses of FD1 and FD2 give a
measure of the precision associated with sample collection, preservation, and
storage, as well as laboratory procedures.
3.9 STOCK STANDARD SOLUTION (SSS) - A concentrated solution containing
one or more method analytes prepared in the laboratory using assayed reference
materials or purchased from a reputable commercial source.
3.10 PRIMARY DILUTION STANDARD (PDS) SOLUTION - A solution
containing the analytes prepared in the laboratory from stock standard solutions
and diluted as needed to prepare calibration solutions and other needed analyte
solutions.
3.11 CALIBRATION STANDARD (CAL) - A solution prepared from the primary
dilution standard solution and/or stock standard solution, and the surrogate
analytes. The CAL solutions are used to calibrate the instrument response with
respect to analyte concentration.
3.12 INSTRUMENT PERFORMANCE CHECK SOLUTION (PC) - A solution of
one or more method analytes, surrogates, or other test substances used to evaluate
the performance of the instrument system with respect to a defined set of criteria.
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3.13 CONTINUING CALIBRATION CHECK (CCC) - A calibration standard
containing the method analytes and surrogates (s), which is analyzed periodically
to verify the accuracy of the existing calibration for those analytes.
3.14 QUALITY CONTROL SAMPLE (QCS) - A solution of method analytes and
surrogate(s) of known concentrations that is obtained from a source external to the
laboratory and different from the source of calibration standards. It is used to
check standard integrity.
3.15 DETECTION LIMIT - 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 of precision
(Sect. 9.2.4), and accurate quantitation is not expected at this level.(2)
3.16 MINIMUM REPORTING LEVEL (MRL) - The minimum concentration that can
be reported as a quantitated value for a target analyte in a sample following
analysis. This defined concentration can be no lower than the concentration of the
lowest continuing calibration standard for that analyte and can only be used if
acceptable quality control criteria for this standard are met.
3.17 MATERIAL SAFETY DATA SHEET (MSDS) - Written information provided
by vendors concerning a chemical's toxicity, health hazards, physical properties,
fire, and reactivity data including storage, spill, and handling precautions.
4. INTERFERENCES
4.1 Interferences can be divided into three different categories: direct
chromatographic coelution, where an analyte response is observed at very nearly
the same retention time as the target anion; concentration dependant coelution,
which is observed when the response of higher than typical concentrations of the
neighboring peak overlap into the retention window of the target anion; and, ionic
character displacement, where retention times may significantly shift due to the
influence of high ionic strength matrices (high mineral content or hardness)
overloading the exchange sites on the column and significantly shortening target
analyte's retention times.
4.1.1 A direct chromatographic coelution may be solved by changing columns,
eluent strength, modifying the eluent with organic solvents (if compatible
with 1C columns), changing the detection systems, or selective removal of
the interference with pretreatment. Sample dilution will have little to no
effect. The analyst must verify that these changes do not induce any
negative affects on method performance by repeating and passing all the
QC criteria as described in Section 9.
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4.1.2 Sample dilution may resolve some of the difficulties if the interference is
the result of either concentration dependant coelution or ionic character
displacement, but it must be clarified that sample dilution will alter your
Minimum Reporting Limit (MRL) by a proportion equivalent to that of the
dilution. Therefore, careful consideration of project objectives should be
given prior to performing such a dilution. An alternative to sample
dilution, may be dilution of the eluent as outlined in Section 11.2.6.
4.1.3 Pretreatment cartridges can be effective as a means to eliminate certain
matrix interferences. With any proposed pretreatment, the analyst must
verify that target analyte(s) are not affected by monitoring recovery after
pretreatment. With advances in analytical separator column technology
which employ higher capacity anion exchange resins, the need for these
cartridges has been greatly reduced.
4.2 Method interferences may be caused by contaminants in the reagent water,
reagents, glassware, and other sample processing apparatus that lead to discrete
artifacts or elevated baselines in an ion chromatogram. These interferences can
lead to false positive results for target analytes as well as reduced detection limits
as a consequence of elevated baseline noise.
4.3 Samples that contain particles larger than 0.45 microns and reagent solutions
require filtration to prevent damage to instrument columns and flow systems.
4.4 Close attention should be given to the potential for carry over peaks from one
analysis which will affect the proper detection of analytes of interest in a second
or subsequent analysis. Normally, in this analysis, the elution of sulfate (retention
time of 17.5 min.) indicates the end of a chromatographic run, but in the ozonated
and chlorine dioxide matrices, a small response (200 nS baseline rise) was
observed for a very late eluting unknown peak following the response for sulfate.
Consequently, a run time of 25 minutes is recommended to allow for the proper
elution of any potentially interfering late peaks. It is the responsibility of the user
to confirm that no late eluting peaks have carried over into a subsequent analysis
thereby compromising the integrity of the analytical results.
4.5 Any residual chlorine dioxide present in the sample will result in the formation of
additional chlorite prior to analysis. If residual chlorine dioxide is suspected in
the sample, the sample must be sparged with an inert gas (helium, argon or
nitrogen) for approximately five minutes. This sparging must be conducted prior
to ethylenediamine preservation and at the time of sample collection.
4.6 The presence of chlorite can interfere with the quantitation of low concentrations
of bromate on the postcolumn UV/Vis absorbance detector. In order to accurately
326.0-7
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quantify bromate concentrations in the range 0.5 - 15.0 |-ig/L in this postcolumn
system, the excess chlorite must be removed prior to analysis as outlined in
Section 11.1.4.
5. SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method has not been
precisely defined; each chemical compound should be treated as a potential health
hazard, and exposure to these chemicals should be minimized. The laboratory is
responsible for maintaining a current awareness file of OSHA regulations
regarding the safe handling of the chemicals specified in this method. A reference
file of MSDSs should also be made available to all personnel involved in the
chemical analysis. Additional references to laboratory safety are available/4"7'
5.2 Pure standard materials and stock standards of these compounds should be
handled with suitable protection to skin and eyes. Care should be taken not to
breathe the vapors or ingest the materials.
5.3 The following chemical has the potential to be highly toxic or hazardous. The
Material Safety Data Sheet (MSDS) should be consulted.
5.3.1 Sulfuric acid - used to prepare regenerant solution (Sect. 7.1.8) for the
second suppressor (Dionex AMMS or Ultra ASRS-1 used in the chemical
mode) and to for pretreatment of the samples for chlorite removal (Sect.
7.1.7,11.1.4)
6. EQUIPMENT AND SUPPLIES
6.1 ION CHROMATOGRAPH - Analytical system complete with ion
chromatographic pump and all required accessories including syringes, analytical
columns, compressed gasses, suppressors, conductivity detector, mixing "tee",
postcolumn reagent delivery system, reaction coil, reaction coil heater, UV/Vis
absorbance detector (Figure 1) and a computer-based data acquisition and control
system.
NOTE: Because the KI PCR solution is susceptible to oxidation, resulting in a
yellow colored solution, the PCR MUST be flushed from the suppressor, reaction
coil and detector cell with reagent water upon completion of the final analysis and
prevented from draining through the reaction coil by gravity once the system is
shut down. This can be accomplished either manually or by incorporating a
column switching valve in combination with a reagent water flush.
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6.1.1 ANION GUARD COLUMN - Dionex AG9-HC 4 mm (Cat.#: 51791 or
equivalent). This column functions as a protector of the separator column.
If omitted from the system the retention times will be shorter.
6.1.2 ANION SEPARATOR COLUMN - Dionex AS9-HC column, 4 mm
(Cat.#: 51786 or equivalent, see Note). The AS9-HC, 4-mm column using
the conditions outlined in Table 1 produced the separations shown in
Figures 2 and 3.
NOTE: The use of 2-mm columns is not recommended. A 50-uL sample
loop would be required with the 2-mm columns. This reduced injection
volume would decrease the "on-column" bromate and negatively affect
PCR reactivity and the subsequent absorbance response. As well, the 2-
mm columns require a flow rate approximately 4 times less than the 4-mm
columns. At the lower flow rates, band broading may become an issue and
it would be difficult to accurately maintain the appropriate reduced flow
rate for the PCR.
6.1.3 ANION SUPPRESSOR DEVICES - The data presented in this method
were generated using a Dionex Ultra-1 Anion Self Regenerating
Suppressor (4 mm ASRS, Cat.#: 53946) for electrolytic suppression of the
eluent and a second Ultra -1 ASRS was used in the chemical mode to
acidify the PCR just prior to addition to the mixing tee. Equivalent
suppressor devices maybe utilized providing comparable conductivity
detection limits are achieved and adequate baseline stability is attained as
measured by a combined baseline drift/noise of no more than 10 nS per
minute over the background conductivity. Alternative suppressor
evaluations subsequent to this method development work have indicated
that improved detection limits and precision and accuracy can be obtained
for bromate by conductivity detection(8). If conductivity analytes below
10 ug/L are to be reported, the combined baseline drift/noise will be
required to be no greater than 5 nS per minute over the background
conductivity. The suppressor must be able to withstand approximately 80
-120 psi back pressure which results from connecting the postcolumn
hardware to the "eluent out" port of the suppressor. The suppressor used
to acidify the PCR must be capable of continuous operation using 150 mN
sulfuric acid as the regenerant.
6.1.3.1 - The conductivity suppressor was set to perform electrolytic
suppression at a current setting of 100 mA using the external water mode.
Insufficient baseline stability was observed on the conductivity detector
using an ASRS in recycle mode.
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6.1.4 CONDUCTIVITY DETECTOR - Conductivity cell (Dionex CD20 or
equivalent) capable of providing data as required in Section 9.2.
6.1.5 ABSORBANCE DETECTOR - Absorbance detector (Dionex AD20 or
equivalent with 10-mm cell pathlength, equipped with a deuterium source
bulb, or equivalent and capable of measuring absorbance at 352 nm)
capable of providing data as required in Section 9.2.
6.1.6 POSTCOLUMN REAGENT DELIVERY SYSTEM -Delivery system
(Dionex PC-10 or equivalent) capable of pneumatically delivering the
postcolumn reagent to the "eluent in" port of the suppressor to acidify the
PCR prior to entering the mixing tee (see Note). The pressure settings will
need to be established on an individual basis for each specific instrument
configuration and at a level which yields the prescribed PCR flow rates.
NOTE: Since KI is photosensitive, the KI/Mo PCR solution was observed
to develop a light yellow color with time, even when stored under helium
in the opaque plastic PC-10 delivery container inside the PC-10
pressurization vessel. Purging the KI/Mo solution with helium
immediately after preparation to remove all oxygen did not completely
eliminate the problem. Consequently, in order to facilitate overnight (24
hours) operation, the external wall of the PC-10 plastic pressurization
vessel was wrapped with an opaque tape, or other light impervious
material, to prevent any light exposure to the KI/Mo PCR (care must be
exercised to leave about 1/16th of an inch at both the top and bottom of the
vessel free of tape to allow for proper sealing of the top and bottom. The
generation of the tri-iodide ion is pH dependant and the second suppressor
is used to acidify the PCR just before entering the reaction coil. Prior to
initiating any analysis batch, to ensure that the pH of the reaction mixture
is below 2, the effluent from the absorbance detector should be monitored
using pH test strips.
6.1.7 REACTION COIL - 500-uL internal volume, knitted, potted and
configured to fit securely in the postcolumn reaction coil heater. (Dionex
Cat.#: 39349 or equivalent).
6.1.8 POSTCOLUMN REACTION COIL HEATER - Capable of maintaining a
temperature of 80 °C (Dionex PCH-2 or equivalent).
6.2 DATA SYSTEM - The Dionex Peaknet Data Chromatography Software was used
to generate all the data in the attached tables. Other computer-based data systems
may achieve approximately the same Detection Limits, but the user must
demonstrate this by the procedure outlined in Section 9.2.
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6.3 ANALYTICAL BALANCE - Used to accurately weigh target analyte salts for
stock standard preparation (±0.1 mg sensitivity).
6.4 TOP LOADING BALANCE - Used to accurately weigh reagents to prepare
eluents (±10 mg sensitivity).
6.5 WEIGH BOATS - Plastic, disposable, used to weigh eluent reagents.
6.6 SYRINGES - Plastic, disposable, 10 mL, used during sample preparation.
6.7 PIPETS - Pasteur, plastic or glass, disposable, graduated, 5 mL and 10 mL.
6.8 BOTTLES - Opaque, high density polyethylene (HDPE) or amber glass, 30 mL,
125 mL, 250 mL - used for sample collection and storage of calibration solutions.
Opaque bottles are required due to the photoreactivity of the chlorite anion.
6.9 MICRO BEAKERS - Plastic, disposable, used during sample preparation.
6.10 PARTICULATE FILTERS - Gelman ion chromatography Acrodisc 0.45 urn
(Cat.#: 4485 or equivalent) syringe filters. These cartridges are used to remove
particulates and [Fe(OH)3(s)] which are formed during the oxidation-reduction
reaction between Fe (IT) and C1O2" (see Sect. 11.1.4).
6.11 HYDROGEN CARTRIDGES - Dionex OnGuard-H cartridges (Cat.#: 039596 or
equivalent). These cartridges are conditioned according to the manufacturer's
directions and are used to protect the analytical column and the suppressor
membrane by removing excess ferrous iron [Fe (n)]. The ferrous iron is added to
field samples to reduce chlorite levels prior to analysis of chlorine dioxide
disinfected water samples for trace levels of bromate (see Sect. 11.1.4).
7. REAGENTS AND STANDARDS
7.1 REAGENTS AND SOLVENTS - Reagent grade or better chemicals should be
used. Unless otherwise indicated, it is intended that all reagents shall conform to
the specifications of the Committee on Analytical Reagents of the American
Chemical Society, where such specifications are available. Other grades may be
used, provided it is first determined that the reagent is of sufficiently high purity
to permit its use without lessening the quality of the determination.
7.1.1 REAGENT WATER - Distilled or deionized water 18 M Q or better, free
of the anions of interest. Water should contain particles no larger than
0.20 microns.
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7.1.2 ELUENT SOLUTION - Sodium carbonate (CAS#: 497-19-8) 9.0 mM.
Dissolve 1.91 g sodium carbonate (NajCOg) in reagent water and dilute to
2L.
7.12.1 This eluent solution must be sparged for 10 minutes with helium
prior to use to remove dissolved gases which may form micro
bubbles in the 1C compromising system performance and adversely
effecting the integrity of the data. Alternatively, an in-line degas
apparatus may be employed.
7.1.3 ETHYLENEDIAMINE (EDA) PRESERVATION SOLUTION (100
mg/mL) - Dilute 2.8 mL of ethylenediamine (99%) (CAS#: 107-15-3) to
25 mL with reagent water. Prepare fresh monthly.
7.1.4 AMMONIUM MOLYBDATE SOLUTION - A 2.0-mM solution of
ammonium molybdate tetrahydrate [(NH 4)6Mo7O244H2O, CAS#:
12027667, Fluka Cat.#: 09878 or equivalent] is prepared by dissolving
0.247 g in 100 mL of reagent water. This reagent is stored in an opaque
plastic storage bottle and prepared fresh monthly.
7.1.5 POSTCOLUMN REAGENT (0.26 M KI, 43 uM ammonium molybdate
heptahydrate) -The postcolumn reagent is prepared by adding 43.1 g of
potassium iodide (KI, CAS#: 7681110, Fluka Cat.#: 60400 or equivalent)
to a 1-L volumetric flask containing about 500 mL of reagent water. Two
hundred and fifteen |jL of the ammonium molybdate solution (Sect. 7.1.4)
is added to the volumetric flask and diluted to volume with reagent water.
The PCR is sparged with helium for 20 minutes to remove all traces of
dissolved oxygen and immediately placed in the PC-10 delivery vessel and
pressurized with helium. The reagent is stable for 24 hours if properly
protected from light (Sect. 6.1.6).
7.1.6 FERROUS IRON SOLUTION [1000 mg/L Fe(II)] - Dissolve 0.124 g
ferrous sulfate heptahydrate (FeSO4.7H2O, CAS#: 7782630, Sigma Cat. #:
F-7002 or equivalent) in approximately 15 mL reagent water containing
6 uL of concentrated nitric acid and dilute to 25 mL with reagent water in
a volumetric flask (final pH ~2). The Fe (II) solution must be prepared
fresh every two days.
7.1.7 SULFURIC ACID (0.5 N) - Dilute 1.4 mL of concentrated sulfuric acid
(Fisher Scientific Certified ACS Plus, A 300-500) to 100 mL.
7.1.8 SULFURIC ACID (0.15 N) - Dilute 8.5 mL of concentrated sulfuric acid
(Fisher Scientific Certified ACS Plus, A 300-500) to 2000 mL.
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7.2 STANDARD SOLUTIONS - Standard Solutions may be prepared from certified,
commercially available solutions or from solid compounds. Compounds used to
prepare solutions must be 96% pure or greater and the weight may be used
without correction for purity to calculate the concentration of the stock standard.
Solution concentrations listed in this section were used to develop this method
and are included as an example. Even though stability times for standard
solutions are suggested in the following sections, laboratories should use
standard QC practices to determine when Standard Solutions described in
this section need to be replaced.
7.2.1 ANALYTE STANDARD SOLUTIONS (1000 mg/L) - Stock standard
solutions may be purchased as certified solutions or prepared from ACS
reagent grade, potassium or sodium salts as listed below, for most
analytes. Certified chlorite standard solutions are commercially available.
If these are not used, chlorite requires careful consideration as outlined
below in Section 7.2.1.1.4.
7.2.1.1 ANALYTE STOCK STANDARD SOLUTIONS - Individual
Analyte Stock Standards Solutions are prepared as described
below.
7.2.1.1.1 Bromide (Br) 1000 mg/L - Dissolve 0.1288 g sodium
bromide (NaBr, CAS#: 7647-15-6) in reagent water and
dilute to 100 mL in a volumetric flask.
7.2.1.1.2 Bromate (BrO3') 1000 mg/L - Dissolve 0.1180 g of
sodium bromate (NaBrO3, CAS#: 7789-38-0) in reagent
water and dilute to 100 mL in a volumetric flask.
7.2.1.1.3 Chlorate (CIO,') 1000 mg/L - Dissolve 0.1275 g of
sodium chlorate (NaClO3, CAS#: 7775-09-9) in
reagent water and dilute to 100 mL in a volumetric
flask.
7.2.1.1.4 Chlorite (C1O2') 1000 mg/L - Prepare from
commercially available standards or as described below.
If the amperometric titration of the technical grade
sodium chlorite (NaClO2), as specified in the Note
below, had indicated the purity of the salt to be 80.0 %
NaClO2, the analyst would dissolve 0.1676 g of sodium
chlorite (NaClO2, CAS#: 7758-19-2) in reagent water
and dilute to 100 mL in a volumetric flask.
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Note: High purity sodium chlorite (NaCIO 2) is not
currently commercially available due to its potential
explosive instability. Recrystallization of the technical
grade (approx. 80%) can be performed but it is labor
intensive and time consuming. The simplest approach
is to determine the exact purity of the NaCIO 2 using the
iodometric titration procedure.(9) Following titration,
an individual component standard of chlorite must be
analyzed to determine if there is any significant
contamination (greater than 1% of the chlorite weight)
from chlorate, bromate or bromide (as other method
target anions) in the technical grade chlorite standard.
7.2.1.2 ANALYTE PRIMARY DILUTION STANDARD (Analyte PDS)
SOLUTION - Prepare two Analyte PDSs by diluting the Analyte
Stock Standard Solutions with reagent water containing EDA (at a
final concentration of 50 mg/L) in volumetric glassware. The
dilutions used to prepare these solutions during the method
development studies are provided below as an example. Prior to
using mixed standards for calibration or spiking solutions, ensure
that the individual Analyte Stock Standard Solutions do not contain
any appreciable concentrations of the other target analytes.
Dilutions of these Analyte PDSs, referred to as Solution A and B
below, are used to prepare the calibration solutions (Sect. 7.2.3)
and the continuing calibration check solutions (Sect. 10.3) for both
detectors.
Analyte PDS Solution A
Analyte
Chlorite
Bromide
Chlorate
Initial Cone.
(mg/L)
1000
10000
1000
Volume
(mL)
2.5
0.25
2.5
Final Volume
(mL)
25
25
25
Final Cone.
(mg/L)
100
100
100
Analyte PDS Solution B
Analyte
Bromate
Initial Cone.
(mg/L)
1000
Volume
(mL)
1.0
Final Volume
(mL)
100
Final Cone.
(mg/L)
10
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7.2.2 SURROGATE ANALYTE (SUR) SOLUTION, DICHLOROACETATE
(DCA, CAS#: 19559-59-2)
7.2.2.1 SURROGATE STOCK SOLUTION (0.50 mg/mL) - Prepare a
surrogate stock solution by dissolving 0.065 g of dichloroacetic
acid, potassium salt (C12CHCO2K) in reagent water and diluting to
100 mL in a volumetric flask. This solution is used to fortify all
field samples, QC samples and calibration standards by adding a
20-uL aliquot of the Surrogate Stock Solution to 10 mL of the
sample. This solution must be prepared fresh every 3 months or
sooner if signs of degradation are present.
7.2.2.1.1 Dichloroacetate is potentially present in treated drinking
waters as the acetate of the organic disinfection
byproduct, dichloroacetic acid (DCAA). Typical
concentrations of DCAA rarely exceed 50 |-ig/L, which
would represent only a five percent increase in the
observed response over the fortified concentration of
1.00 mg/L. Consequently, the upper recovery limit for
the surrogate (90% to 115%) has been increased to
allow for this potential background.
7.2.2.1.2 If the analyst is exclusively interested in monitoring
trace bromate using the PCR and the UV/VIS
absorbance detector, suppression of the eluent prior to
reaction with the PCR MUST be incorporated. In
addition, the surrogate must also be included and meet
the QC requirements as outlined in Section 9.7.1.
7.2.2.2 SURROGATE PRIMARY DILUTION STANDARD - A
Surrogate PDS is not prepared since the Surrogate Stock (Sect
7.2.2.1) is used to fortify samples.
7.2.3 CALIBRATION STANDARDS (CAL) - At least 5 calibration
concentrations are required to prepare the initial calibration curve (Sect.
10.2) for each detector. Prepare the calibration standards over the
concentration range of interest from dilutions of the Analyte PDSs A and
B in reagent water containing EDA (50 mg/L). The lowest concentration
calibration standard must be at or below the MRL, which may depend
upon system sensitivity. The calibration standards for the development of
this method were prepared by adding aliquots of the two Analyte PDSs
(Analyte PDS Solution A and B described above in Sect. 7.2.1.2) as shown
in the tables below to a volumetric flask, containing the listed volume of
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EDA solution, and diluting to volume with reagent water. These standards
may be also be used as CCCs.
Conductivity Detector CAL and CCC Standards
Cal
Std.
1*
2
3*
4
5*
Stock A
(HL)
10
25
75
200
500
Stock B
(HL)
100
250
500
750
1000
EDA
Volume
(uL)
50
50
50
50
50
Final
Volume
(mL)
100
100
100
100
100
C1O2, Br, C1O3
Final Cone.
(l-ig/L)
10
25
75
200
500
Bromate
Final Cone.
(l-ig/L)
10
25
50
75
100
*Prepared in larger volume and used as CCCs
Absorbance Detector CAL and CCC Standards
Cal
Std.
1*
2
3
4*
5
6*
Stock B
(jiL)
5
10
20
50
100
150
EDA
Volume
(uL)
50
50
50
50
50
50
Final
Volume
(mL)
100
100
100
100
100
100
Bromate
Final Cone.
(l-ig/L)
0.5
1.0
2.0
5.0
10.0
15.0
*Prepared in larger volume and used as CCCs
7.2.3.1 Fortify each CAL or CCC standard by adding a 20 uL aliquot of
the Surrogate Stock Standard Solution (Sect. 7.2.2.1) to a 20 mL
disposable plastic micro beaker containing 10.0 mL of the
calibration standard (or CCC) and mix. These volumes may be
adjusted to meet specific laboratory autosampler volume
requirements.
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8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 SAMPLE COLLECTION
8.1.1 Samples should be collected in opaque plastic or amber glass bottles. All
bottles must be thoroughly cleaned and the volume collected should be
sufficient to ensure a representative sample, allow for replicate analysis
and laboratory fortified matrix analysis, if required, while minimizing
waste disposal.
8.1.2 When collecting a field sample from a treatment plant employing chlorine
dioxide, the field sample must be sparged with an inert gas (helium or
nitrogen) prior to addition of the EDA preservative at time of sample
collection. The sample should be collected in a clean wide mouth flask
(such as an Erlenmeyer flask). The sparging gas can be obtained by using
a lecture bottle of nitrogen or helium fitted with a regulator and connected
to a disposable glass Pasteur pipette with PVC tubing. The gas flow
should be adjusted to produce a steady flow of bubbles. After 10-15
minutes of sparging, all traces of chlorine dioxide should be removed from
the sample. It can then be poured from the flask into the sample bottle that
contains the ethylenediamine (EDA) preservative. In order to eliminate
potential cross contamination problems, it is recommended that a clean
Erlenmeyer flask and a new disposable pipette be used at each sampling
point.
8.1.3 Add a sufficient volume of the EDA preservation solution (Sect. 7.1.3)
such that the final concentration is 50 mg/L in the sample. This would be
equivalent to adding 0.5 mL of the EDA preservation solution to 1 L of
sample.
8.2 SPECIAL SAMPLING REQUIREMENTS AND PRECAUTIONS FOR
CHLORITE
8.2.1 Sample bottles used for chlorite analysis must be opaque plastic or amber
glass to protect the sample from light.
8.2.2 When preparing the LFSM, be aware that chlorite is an oxidant and may
react with the natural organic matter in an untreated drinking water matrix
as a result of oxidative demand. If untreated water is collected for chlorite
analysis, and subsequently used for the LFSM, EDA preservation will not
control this demand and reduced chlorite recoveries may be observed.
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8.3
8.2.3 Chlorite is susceptible to degradation both through catalytic reactions with
dissolved iron salts and reactivity towards free chlorine which exists as
hypochlorous acid/hypochlorite ion in most drinking water as a residual
disinfectant/10' EDA serves a dual purpose as a preservative for chlorite by
chelating iron as well as any other catalytically destructive metal cations
and removing hypochlorous acid/hypochlorite ion by forming an
organochloramine. EDA preservation of chlorite also preserves the
integrity of chlorate which can increase in unpreserved samples as a result
of chlorite degradation. EDA also preserves the integrity of bromate
concentrations by binding with hypobromous acid/hypobromite ion which
is an intermediate formed as a by-product of the reaction of either ozone or
hypochlorous acid/hypochlorite ion with bromide ion. If hypobromous
acid/hypobromite ion is not removed from the matrix, further reactions
may form bromate ion.
SAMPLE SHIPMENT AND STORAGE - All 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. Samples stored in the lab must be held at or below 6 °C and protected
from light until analysis. Samples should not be frozen. Sample preservation and
holding times for the anions are as follows:
Analyte
Bromate
Chlorate
Chlorite
Bromide*
Preservation
50 mg/L EDA, store at < 6 °C
50 mg/L EDA, store at < 6 °C
50 mg/L EDA, store at <6 °C
50 mg/L EDA, store at <6 °C
Holding Time
28 days
28 days
14 days
28 days
*Source and raw water only.
9. QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal quality control
(QC) program. The requirements of this program consist of an initial
demonstration of laboratory capability (IDC), and subsequent analysis in each
Analysis Batch (Sect. 3.1) of a Laboratory Reagent Blank (LRB), Continuing
Calibration Check Standards (CCCs), Laboratory Fortified Blank (LFB),
Instrument Performance Check Standard (IPC), Laboratory Fortified Sample
Matrix (LFSM) and either Laboratory Fortified Sample Matrix Duplicate
(LFSMD) or a Field Duplicate (FD) Sample. This section details the specific
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requirements for each of these QC parameters for both the conductivity and
absorbance detectors used in this application. Although the Detection Limits and
MRLs may differ, the QC requirements and acceptance criteria are the same for
both detectors. The QC criteria discussed in the following sections are
summarized in Section 17, Tables 4 and 5. These criteria are considered the
minimum acceptable QC criteria, and laboratories are encouraged to institute
additional QC practices to meet their specific needs.
9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC) - Requirements for the
Initial Demonstration of Capability are described in the following sections and
summarized in Section 17, Table 4.
9.2.1 INITIAL DEMONSTRATION OF LOW SYSTEM BACKGROUND -
Before any field samples are analyzed, and any time a new set of reagents
is used, it must be demonstrated that a laboratory reagent blank is
reasonably free of contamination and that the criteria in Section 9.4 are
met.
9.2.2 INITIAL DEMONSTRATION OF ACCURACY - Prior to the analysis of
the IDC samples, verify calibration accuracy with the preparation and
analysis of a mid-level QCS as defined in Section 9.11. If the analyte
recovery is not + 15% of the true value, the accuracy of the method is
unacceptable. The source of the problem must be identified and corrected.
After the accuracy of the calibration has been verified, prepare and analyze
7 replicate LFBs fortified at a recommended concentration of 20 ug/L for
the conductivity detector or near the mid-range of the initial calibration
curve. For the absorbance detector, prepare 7 replicate LFBs fortified at a
recommended concentration of 2.0 ug/L bromate. Sample preservatives as
described in Section 8.1.3 must be added to all LFBs. The average
recovery of the replicate values must be within ± 15% of the true value.
9.2.3 INITIAL DEMONSTRATION OF PRECISION - Using the same set of
replicate data generated for Section 9.2.2, calculate the standard deviation
and percent relative standard deviation of the replicate recoveries. The
percent relative standard deviation (%RSD) of the results of the replicate
analyses must be < 20%.
9.2.4 DETECTION LIMIT DETERMINATION - Prepare and analyze at least 7
replicate LFBs at a concentration estimated to be near the Detection Limit
over at least 3 days using the procedure described in Section 11. This
fortification level may be estimated by selecting a concentration with a
signal of 2 to 5 times the noise level. The appropriate concentration will
be dependent upon the sensitivity of the 1C system being used. Sample
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preservatives as described in Section 8.1.3 must be added to these
samples. Calculate the Detection Limit using the equation
Detection Limit = St(n. ^ ^. alpha = 099)
where
t(n-u-aipha = o.99)= Student's t value for the 99% confidence level with n-1
degrees of freedom,
n = number of replicates, and
S = standard deviation of replicate analyses.
NOTE: Calculated Detection Limits need only be less than V3 of the
laboratory's MRL to be considered acceptable. Do not subtract blank
values when performing Detection Limit calculations. The Detection
Limit is a statistical determination of precision only.(2) No precision and
accuracy criteria are specified.
9.3 MINIMUM REPORTING LEVEL (MRL) - The MRL is the threshold
concentration of an analyte that a laboratory can expect to accurately quantitate in
an unknown sample. The MRL should not be established at an analyte
concentration that is less than either three times the Detection Limit or a
concentration which would yield a response less than a signal-to-noise (S/N) ratio
of five. Depending upon the study's data quality objectives it may be set at a
higher concentration. The lowest calibration standard must be at or below the
MRL and therefore, the MRL must never be established at a concentration
lower than the lowest calibration standard.
9.4 LABORATORY REAGENT BLANK (LRB) - A LRB is required with each
Analysis Batch (Sect. 3.1) of samples to determine any background system
contamination. If within the retention time window of any analyte, the LRB
produces a peak that would prevent the determination of that analyte, determine
the source of contamination and eliminate the interference before processing
samples. Background contamination must be reduced to an acceptable level
before proceeding. Background from method analytes or contaminants that
interfere with the measurement of method analytes must be below 1/3 the MRL.
If the target 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 in the analysis batch.
9.4.1. EDA must be added to the LRB at 50 mg/L. By including EDA in the
LRB, any potential background contamination from the EDA will be
identified.
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9.4.2 When the PCR method is used for low level bromate analysis on samples
from public water systems (PWSs) which employ chlorine dioxide
disinfection, the matrix must be pretreated to remove the potentially
interfering chlorite anion (Sect. 11.1.4). When these types of pretreated
samples, or any type of pretreatment is applied to field samples included as
part of an analysis batch, a second LRB must be prepared, pretreated and
analyzed to confirm no background effects of the pretreatment are present.
If the analysis batch contains only pretreated samples, then only a
pretreated LRB is required.
9.5 CONTINUING CALIBRATION CHECK (CCC) - CCCs are prepared in the
same manner as the Calibration Standards (Sect. 7.2.3), using reagent water and
EDA as described in Section 8.1.3. They are analyzed during an analysis batch at
a required frequency to confirm that the instrument meets initial calibration
criteria. See Section 10.3 for concentration requirements, frequency requirements,
and acceptance criteria.
9.6 LABORATORY FORTIFIED BLANK (LFB) - A LFB is required with each
analysis batch to confirm acceptable method accuracy. Since calibration solutions
are prepared in large volumes and can be used over an extended period of time,
the integrity of the concentration of the solution used to fortify the LFSM is
checked by preparing the LFB using the same Analyte Stock Standard Solutions
used to prepare the LFSM fortification solution. The fortified concentration of the
LFB should be rotated between, low, medium, and high concentrations from batch
to batch. The low concentration LFB must be as near as practical to, but no more
than two times the MRL. Similarly, the high concentration should be near the
high end of the calibration range established during the initial calibration (Sect.
10.2). The recovery of all analytes fortified at the low concentration must be 75-
125% of the true value, and 85-115% when fortified at the medium and high
concentrations. If the LFB recovery for an analysis batch does not meet these
recovery criteria, the data are considered invalid, and the source of the problem
must be identified and resolved before continuing with analyses.
LFB Fortified Concentration Range
MRL to 2 x MRL
2 x MRL to highest calibration level
LFB Recovery Limits
75-125 %
85-115%
9.7 SURROGATE RECOVERY - The surrogate standard is fortified into all samples,
blanks, CCCs, QDCSs, LRBs, and LFSMs and LFSMDs prior to analysis. It is
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also added to the calibration curve and calibration check standards. The surrogate
is a means of assessing chromatographic method performance.
9.7.1 Surrogate recoveries must fall between 90-115% for proper instrument
performance and analyst technique to be verified. The recovery range for
the surrogate is extended to 115% to allow for the potential contribution of
trace levels of dichloroacetate as ahalogenated organic disinfection by-
product (DBF) of dichloroacetic acid (DCAA). Background levels of this
organic DBF are rarely observed above 50 |-ig/L (0.05 mg/L) which
constitutes only 5% of the 1.00 mg/L recommended fortified
concentration.
9.7.2 When surrogate recovery from a sample, blank, or CCC is less than 90%
or greater than 115%, check (1) calculations to locate possible errors, (2)
standard solutions for degradation, (3) contamination, and (4) instrument
performance. If those steps do not reveal the cause of the problem,
reanalyze the sample.
9.7.3 If the reanalysis meets the surrogate recovery criteria, report only data for
the reanalyzed sample.
9.7.4 If the sample reanalysis fails the 90-115% surrogate recovery criteria, the
analyst should check the calibration byre-injecting the most recently
acceptable calibration standard. If the calibration standard fails the criteria
of Section 10.3, recalibrate as described in Section 10.2. If the calibration
standard is acceptable, preparation and analysis of the sample should be
repeated provided the sample is still within the holding time. If this
sample reanalysis also fails the recovery criteria, report all data for that
sample as suspect due to surrogate recovery.
9.7.5 If a laboratory chooses to monitor exclusively for trace bromate using PCR
and the UV/VIS absorbance detector, suppression of the eluent MUST be
used and the surrogate added and monitored on the conductivity detector
and the appropriate QC criteria for the surrogate as outlined in Section
9.7.1 must be met.
9.8 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) - Analysis of LFSMs
are required in each analysis batch and are used to determine that the sample
matrix does not adversely affect method accuracy. Additional LFSM
requirements, as described in Section 9.8.4, apply when the PCR system is used
for low level bromate in waters disinfected with chlorine dioxide. If the
occurrence of target analytes in the samples is infrequent, or if historical trends are
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unavailable, a second LFSM, or LFSMD (Sect. 9.9), must be prepared, and
analyzed from a duplicate of the field sample used to prepare the LFSM to assess
method precision. Analytical batches that contain LFSMDs will not require the
analysis of a Field Duplicate (Sect. 9.9). If a variety of different sample matrices
are analyzed regularly, for example, drinking water from groundwater and surface
water sources, method performance should be established for each. Over time,
LFSM data should be documented for all routine sample sources for the
laboratory.
9.8.1 Within each analysis batch, a minimum of one field sample is fortified as a
LFSM for every 20 samples processed. The LFSM is prepared by spiking
a sample with an appropriate amount of the appropriate Analyte PDS
(Sect. 7.2.1.2). Select a spiking concentration at least twice the matrix
background concentration, if known. Use historical data or rotate through
a range of concentrations when selecting a fortifying concentration.
Selecting a duplicate bottle of a sample that has already been analyzed aids
in the selection of appropriate spiking levels.
9.8.2 Calculate the percent recovery (%R) for each analyte using the equation
%R= (*"B)
where
A = measured concentration in the fortified sample
B = measured concentration in the unfortified sample, and
C = fortification concentration.
9.8.3 Analyte recoveries may exhibit a matrix bias. For samples fortified at or
above their native concentration, recoveries should range between 75 -
125%. If the accuracy of any analyte falls outside the designated range,
and the CCC performance for that analyte is shown to meet the acceptance
criteria, the recovery is judged to be matrix-biased. The result for that
analyte in the unfortified sample is labeled suspect/matrix to inform the
data user that the results are suspect due to matrix effects.
9.8.4 When the PCR method is used for low level bromate analysis on field
samples from PWSs which employ chlorine dioxide disinfection and
consequently contain chlorite, a LFSM must be prepared, exclusively for
trace bromate, for each of these field samples. Initially, the field sample is
analyzed and chlorite, chlorate and bromide levels are determined. Then,
a second aliquot of field sample is pretreated to remove chlorite, as
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described in Section 1 1 .1 .4, and analyzed to determine native bromate
concentration. A third aliquot of the field sample then must be fortified
with bromate, pretreated as described in Section 1 1.1.4 to remove chlorite,
and analyzed to assess bromate recovery from that matrix. This additional
QC is required to rule out matrix effects and to confirm that the laboratory
performed the chlorite removal step (Sect. 11.1.4) appropriately. This
LFSM should be fortified with bromate at concentrations close to but
greater than the level determined in the native sample. Recoveries are
determined as described above (Sect. 9.8.2). Samples that fail the LFSM
percent recovery criteria of 75 - 125% must be reported as suspect/matrix.
9.9 FIELD DUPLICATE OR LABORATORY FORTIFIED SAMPLE MATRIX
DUPLICATE (FD or LFSMD) - Within each analysis batch, a minimum of one
Field Duplicate (FD) or Laboratory Fortified Sample Matrix Duplicate (LFSMD)
must be analyzed. Duplicates check the precision associated with sample
collection, preservation, storage, and laboratory procedures. If target analytes are
not routinely observed in field samples, a LFSMD should be analyzed rather than
aFD.
9.9. 1 Calculate the relative percent difference (RPD) for duplicate
measurements (FD1 and FD2) using the equation
RPD-
(FD1+FD2)/2
9.9.2 If a LFSMD is analyzed instead of a Field Duplicate, calculate the relative
percent difference (RPD) for duplicate LFSMs (LFSM and LFSMD) using
the equation
RPD- \LFSM-LFSMD\ ^QQ
(LFSM+ LFSMD)/2
9.9.3 RPDs for FDs and duplicate LFSMs should fall in the range presented in
the table below for samples fortified at or above their native concentration.
Greater variability may be observed when LFSMs are spiked near the
MRL.
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Concentration Range
MRL to 5 x MRL
5 x MRL to highest calibration level
RPD Limits
± 20 %
± 10 %
If the accuracy of any analyte falls outside the designated range, and the
laboratory performance for that analyte is shown to meet the acceptance
criteria in the LFB, the recovery for that analyte is judged to be matrix
biased. The result for that analyte in the unfortified sample is labeled
suspect/matrix to inform the data user that the results are suspect due to
matrix effects
9.10 INSTRUMENT PERFORMANCE CHECK - The low-level CCC Standard is
evaluated in each analytical batch in order to confirm proper instrument
performance (Sect. 10.3). This analysis confirms the MRL and demonstrates
proper chromatographic performance at the beginning of each analysis batch.
Chromatographic performance is judged by calculating the Peak Gaussian Factor
(PGF), which is a means to measure peak symmetry and monitor retention time
drift in the surrogate peak over time. The PGF, as determined below, must fall
between 0.80 and 1.15, and the retention time for the surrogate must be at least
80% of the initial retention time when the 1C column was new. If these criteria
are not met, corrective action must be performed prior to analyzing additional
samples. Major maintenance such as replacing columns requires repeating the
IDC determination (Sect. 9.2).
9.10.1 The PGF is calculated using the equation
PGF =
where
W(l/2) is the peak width at half height, and
W (V10) is the peak width at tenth height.
NOTE: Values for WO/2) and W (V10) for each peak can be attained
through most data acquisition software packages.
9.10.2 Small variations in retention time can be anticipated when a new solution
of eluent is prepared but if sudden shifts of more than 5% are observed in
the surrogate retention time, some type of instrument problem should be
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suspected. Potential problems include improperly prepared eluent,
erroneous method parameters such as flow rate or some other system
problem. The chromatographic profile (elution order) of the target anions
following an ion chromatographic analysis should closely resemble the
profile displayed in the test chromatogram that was shipped when the
column was purchased. As a column ages, it is normal to see a gradual
shift and shortening of retention times, but if after several years of use,
extensive use over less than a year, or use with harsh samples, this
retention time has noticeably shifted to any less than 80% of the original
recorded value, the column requires cleaning or replacement, especially if
resolution problems are beginning to occur between previously resolved
peaks. A laboratory should retain a historic record of retention times for
the surrogate and all the target anions to provide evidence of an analytical
column's efficiency.
9.10.3 If a laboratory chooses to monitor exclusively for trace bromate using PCR
and the UV/VIS absorbance detector, suppression of the eluent MUST be
used and the surrogate added and monitored on the conductivity detector
and the appropriate QC criteria for the surrogate as outlined in Section
9.7.1 must be met.
9.11 QUALITY CONTROL SAMPLE (QCS) - Each time new Calibration Standards
(Sect. 7.2.3) are prepared, or at least quarterly, analyze a QCS from a source
different from the source of the calibration standards. The acceptance criteria for
the QCS is 85-115% of the true value. If measured analyte concentrations are not
of acceptable accuracy, check the entire analytical procedure to locate and correct
the problem source.
10. CALIBRATION AND STANDARDIZATION
10.1 Demonstration of acceptable initial calibration is required prior to performing the
IDC and before any samples are analyzed. It is also required intermittently
throughout sample analysis to meet required QC performance criteria summarized
in Tables 4 and 5. Initial calibration verification is performed using a QCS (Sect.
9.11) as well as with each analysis batch using Continuing Calibration Check
Standards. The procedure for establishing the initial calibration curve is
described in Section 10.2. The procedure to verify the calibration with each
analysis batch is described in Section 10.3.
10.2 INITIAL CALIBRATION
10.2.1 Establish ion chromatographic configuration and operating parameters
equivalent to those indicated in Table 1 and Figure 1.
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10.2.2 Estimate the calibration range over which the instrument response is
linear. On the conductivity detector for the four target analytes (chlorite,
bromate, bromide and chlorate) the linear range should cover the expected
concentration range of the field samples and should not extend over more
than two orders of magnitude in concentration. The method development
data were collected on single linear calibrations that spanned 5 to 500 ug/L
for chlorite, bromide and chlorate and 5 to 100 ug/L bromate for the
conductivity detector and 0.5 to 15.0 ug/L for bromate on the absorbance
detector.
10.2.2.1 If quantification is desired over a larger range, then two or more
separate calibration curves must be prepared.
10.2.2.2 A minimum of five Calibration Standards (Sect. 7.2.3) should be
prepared for each calibration. It is recommended that at least
four of the Calibration Standards are at a concentration > the
MRL. Because high concentrations of chlorite can interfere with
the postcolumn analysis of low levels of bromate, the
conductivity and absorbance detectors must be calibrated
separately.
10.2.2.3 When quantitated using the initial calibration curve, each
calibration point, except the lowest point, for each analyte should
calculate to be 85-115% of its true value. The lowest point
should calculate to be 75-125% of its true value. Failure to meet
this criteria may indicate future difficulty in meeting CCC QC
requirements during the analysis batch.
10.2.2.4 Since the concentration ranges in actual field samples by
conductivity detection for chlorite, bromide and chlorate are
expected to cover two orders of magnitude, the use of calibration
standards in the range 5 - 500 |-ig/L is recommended.
10.2.2.5 Bromate concentrations are expected to be significantly lower. It
is suggested that the conductivity detector be calibrated using
bromate calibration standard levels in the range 5-100 |-ig/L.
Additionally, report values for bromate by conductivity ONLY
when they are measured by the PCR above 15.0 ug/L. The
conductivity detector may exhibit a response for bromate at
concentrations below 15.0 ug/L, but these should not be reported.
When using both detectors, PCR results for bromate in this range
(5-15 ug/L) will have far better precision and accuracy.
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10.2.3 Prepare a set of at least 5 calibration standards as described in Section
7.2.3. The lowest concentration calibration standard must be at or below
the MRL, which may depend on system sensitivity.
10.2.4 Inject 225 |_iL of each calibration standard and tabulate peak area responses
against the concentration for the four target analytes, the surrogate from
the conductivity detector, and bromate from the postcolumn absorbance
detector. Prepare calibration curves using linear regression analysis for
each analyte on the conductivity detector and using a quadratic polynomial
function for bromate on the absorbance detector.
10.2.4.1 Use of peak areas are strongly recommended since they have
been found to be more consistent, in terms of quantitation, than
peak heights. Peak height can tend to be suppressed as a result of
high levels of common anions in a given matrix which can
compete for exchange sites leading to peak broadening.
However, poorly drawn baselines can have a more significant
influence on peak areas than peak heights. It is the analyst's
responsibility to review all chromatograms to ensure accurate
baseline integration of target analyte peaks.
10.2.5 After establishing (or re-establishing) calibration curves, the accuracy of
this calibration must be verified through the analysis of a QCS or an
externally prepared second source standard. The QCS should be prepared
at a concentration near the middle of the calibration range. As specified in
Section 9.11, determined concentrations must fall within ± 15% of the
stated values.
10.3 CONTINUING CALIBRATION CHECK (CCC) - Initial calibrations may be
stable for extended periods of time. Once the calibration curves have been
established for both the conductivity and absorbance detectors, they must be
verified for each analysis batch prior to conducting any field sample analyses
using CCCs. The first CCC each day must be at or below the MRL in order to
verify instrument sensitivity prior to any analyses. Subsequent CCCs must be run
after every 10 field samples and should alternate between a mid- and high-level
CCC. LRBs, CCCs, LFSMs and LFSMDs are not counted as field samples.
10.3.1 A low-level CCC must be determined to be valid each day prior to
analyzing any samples by injecting an aliquot of the appropriate CCC
under the same instrumental conditions used to collect the initial
calibration. Since two detectors are incorporated in this method, this must
be accomplished by using a mixed calibration check standard for the four
conductivity analytes and a separate low-level bromate CCC for the
326.0-28
-------
absorbance detector. The low-level CCC for both detectors must be at or
below the MRL. Percent recovery for the low-level CCC must be in the
range of 75 - 125% before the analyst is allowed to analyze samples.
10.3.2 Additional CCC standards must be analyzed after every tenth field sample
and at the end of the analysis batch. If more than 10 field samples are
included in an analysis batch, the analyst should alternate between the
mid- and high-level CCC Standards. Percent recovery for the mid- and
high-level CCCs must be in the range of 85 - 115%.
10.3.3 If the calibration verification criteria listed above are not met, or the
retention times shift more than ± 2% from the last acceptable initial or
continuing calibration check standard for any analyte, then all samples
analyzed after the last acceptable calibration check standard are considered
invalid and must be reanalyzed. The source of the problem must be
identified and resolved before reanalyzing the samples or continuing with
the analyses.
10.3.2.1 In the case where the end calibration failed to meet performance
criteria, but the initial and middle calibration check standards
were acceptable, the samples bracketed by the acceptable
calibration check standards may be reported. However, all field
samples between the middle and end calibration check standards
must be reanalyzed.
11. PROCEDURE
11.1 SAMPLE PREPARATION
11.1.1 For refrigerated or field samples arriving at the laboratory cold, ensure the
samples have come to room temperature prior to conducting sample
analysis by allowing the samples to warm on the bench for at least 1 hour.
11.1.2 Prepare a 10.0-mL aliquot of surrogate fortified sample which can be held
for direct manual injection or used to fill an autosampler vial. This is done
by adding 20 |_iL of the surrogate solution (Sect. 7.2.2) to a 20-mL
disposable plastic micro beaker. Next, place a 10.0-mL aliquot of sample
in the micro beaker and mix. These volumes may be adjusted to meet
specific laboratory autosampler volume requirements provided the
fortified surrogate concentration is at the prescribed concentration of 1.0
mg/L. The sample is now ready for analysis.
326.0-29
-------
NOTE: The less than 1% dilution error introduced by the addition of the
surrogate is considered insignificant. If a laboratory chooses to monitor
exclusively for trace bromate using PCR and the UV/VIS absorbance
detector, suppression of the eluent MUST be used and the surrogate added
and monitored on the conductivity detector and the appropriate QC criteria
for the surrogate as outlined in Section 9.7.1 must be met.
11.1.3 Using a Luer lock, plastic 10-mL syringe, withdraw the sample from the
micro beaker and attach a 0.45-|_im particulate filter (demonstrated to be
free of ionic contaminants) directly to the syringe. Filter the sample into
an autosampler vial (if vial is not designed to automatically filter) or
manually load the injection loop injecting a fixed amount of filtered, well
mixed sample. If using a manually loaded injection loop, flush the loop
thoroughly between sample analysis using sufficient volumes of each new
sample matrix.
11.1.4 CHLORINE DIOXIDE - TREATED WATERS CONTAINING
CHLORITE - Treatment plants that use chlorine dioxide as part of their
treatment process can produce high levels of chlorite in samples. Since
chlorite can interfere with the postcolumn quantitation of low levels of
bromate as described in Section 4.6, chlorite must be removed from these
samples prior to analysis/11' The oxidation-reduction reaction between
ferrous iron and chlorite(12) is used to remove chlorite without any adverse
affects on the bromate concentration/13'
11.1.4.1 Place a 10-mL aliquot of sample in a 20-mL micro beaker and add
35 uL of 0.5 N sulfuric acid (Sect. 7.1.7). After mixing, verify the
pH is between 5 and 6 using pH test strips, add 40 uL of ferrous
iron solution (Sect. 7.1.6), mix and allow to react for 10 minutes.
Filter the reaction mixture using a 0.45 micron particulate filter
(Sect. 6.10) attached to a 10-mL syringe into the barrel of a second
syringe to which a pre-conditioned hydrogen cartridge (Sect. 6.11)
is attached. Pass the solution through a hydrogen cartridge at a
flow rate of approximately 2 mL per minute. Discard the first 3
mL, and collect an appropriate volume (depending on autosampler
vial size) for analysis. Add the respective volume of surrogate
solution, depending on the volume collected. The sample is ready
for analysis (Sect. 11.2).
NOTE: Pretreated samples can be held for no more than 30 hours
after initial pretreatment. If this time has expired, the pretreatment
steps must be repeated on a second aliquot of both the field sample
matrix and the respective LFSM.
326.0-30
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11.1.4.2 In order to ensure data quality, all samples from PWSs which
utilize chlorine dioxide which have been pretreated to remove
chlorite, MUST also be used to prepare a pretreated LFSM specific
to trace bromate. This LFSM should be fortified with bromate at
concentrations close to but greater than the level determined in the
native sample. Initially, the field sample is analyzed and chlorite,
chlorate and bromide levels are determined. Then, a second
aliquot of field sample is pretreated to remove chlorite, as
described above and analyzed to determine native bromate
concentrations. A third aliquot of the field sample then must be
fortified with bromate, pretreated to remove chlorite, and analyzed
to assess bromate recovery from that matrix. This additional QC
is required to rule out matrix effects and to confirm that the
laboratory performed the chlorite removal step appropriately. If
the bromate recovery falls outside the acceptance range of 75 -
125% (Sect. 9.8), that particular sample should be reported as
suspect/matrix.
11.1.4.3 All samples from PWSs that utilize chlorine dioxide, which have
been pretreated to remove chlorite, MUST also include an
additional pretreated LRB in the analytical batch (Sect. 9.4.2).
11.1.4.4 Suppressor devices which have had long term exposure to iron
cations may have reduced method performance in other
applications, such as the determination of certain common
inorganic anions. If reduced peak response is observed,
particularly for fluoride or phosphate, the suppressor should be
cleaned according to the manufacturer's recommendations.
11.2 SAMPLE ANALYSIS
11.2.1 Table 1 summarizes the recommended operating conditions for the ion
chromatograph and delivery of the postcolumn reagent. Included in this
table are the actual retention times and Detection Limits that were
determined during the development of this method. Other columns or
chromatographic conditions maybe used if the requirements of Section 9 are
met.
11.2.2 Establish a valid initial calibration as described in Section 10.2 and complete
the IDC (Sect. 9.2). Check system calibration by analyzing a low-level
CCC (Sect. 10.3.1) as part of the initial QC for the analysis batch and, if
required, recalibrate as described in Section 10.2.
326.0-31
-------
11.2.3 Inject 225 |_iL of each sample. Use the same size loop for standards and
samples. An automated constant volume injection system may also be used.
11.2.4 The width of the retention time window used to make identifications should
be based upon measurements of actual retention time variations of standards
measured over several days. Three times the standard deviation of retention
time can be used to calculate a suggested window size for each analyte.
However, the experience of the analyst should weigh heavily in the
interpretation of chromatograms.
11.2.5 If the response of a sample analyte exceeds the calibration range, the sample
must be diluted with an appropriate amount of EDA fortified reagent water
and reanalyzed.
11.2.6 Should more complete resolution be needed between any two coeluting
peaks, the eluent (Sect. 7.1.2) can be diluted. This will extend the run,
however, and will cause late eluting anions to be retained even longer. The
analyst must verify that this dilution does not negatively affect performance
by repeating the IDC (Sect. 9.2), and by reestablishing a valid initial
calibration curve (Sect. 10.2). As a specific precaution, upon dilution of the
carbonate eluent, a peak for bicarbonate may be observed on the
conductivity detector within the retention time window for bromate which
will negatively impact the analysis.
11.2.6.1 Eluent dilution will reduce the overall response of an anion due to
chromatographic band broadening which will be evident by
shortened and broadened peaks. This will adversely effect the
Detection Limit for each analyte.
11.3 AUTOMATED ANALYSIS WITH METHOD 326.0
11.3.1 Laboratories conducting analyses on large numbers of samples often prepare
large analysis batches that are run in an automated manner. When
conducting automated analyses, careful attention must be paid to all
reservoirs to be certain sufficient volumes are available to sustain extended
operation. Laboratories must ensure that all QC performance criteria are
met as described in preceding sections to ensure their data are of acceptable
quality.
11.3.1.1 Special attention must be paid when the PCR reservoir is refilled.
The PCR is stable for only 24 hours and consequently the reservoir
must be regularly filled with freshly prepared reagent. Since this is
a pneumatically driven system, the baseline will require a
326.0-32
-------
minimum often minutes to restabilize after the reservoir has been
refilled and the bottle repressurized.
11.3.2 Because this method has two detectors that require independent calibration,
analysis sequences must be carefully constructed to meet required QC
specifications and frequency (Sect. 17, Table 5). To help with this task, an
acceptable sequence for a sample analysis batch, with all the method-
required QC, is shown in Table 6. This schedule is included only as an
example of a hypothetical analysis batch where the analyst desires to collect
data using both detectors. Within the analysis batch, references to exact
concentrations for the CCCs are for illustrative purposes only. The analyses
for sample #14 provides an example of the QC requirements for a complete
conductivity and trace bromate PCR analysis of a sample from a PWS
employing chlorine dioxide disinfection.
12. DATA ANALYSIS AND CALCULATIONS
12.1 Identify the method analytes in the sample chromatogram by comparing the
retention time of the suspected analyte peak to the retention time of a known analyte
peak in a calibration standard. If analyte retention times have shifted (generally
towards shorter times) since the initial calibration, but are still within acceptance
criteria and are reproducible during the analysis batch, the analyst should use the
retention time in the daily calibrations to confirm the presence or absence of target
analytes.
12.2 Compute sample concentration using the initial calibration curve generated in
Section 10.2.
12.3 Report ONLY those values that fall between the MRL and the highest calibration
standard. Samples with target analyte responses exceeding the highest standard
must be diluted and reanalyzed. When this is not possible the alternate calibration
procedures described in Section 11.2.5 must be followed.
12.3.1 Report bromate concentrations using the postcolumn UV/Vis absorbance
detector when they fall between the MRL and 15.0 ug/L. When bromate
concentrations exceed 15.0 ug/L, as detected by UV/Vis absorbance, either
report by conductivity, calibrate the postcolumn UV/Vis absorbance detector
to a higher bromate concentration, or dilute the sample.
12.4 Report analyte concentrations in |_ig/L (usually with two significant figures).
12.5 Software filtering of the postcolumn UV/Vis absorbance signal is recommended to
improve the precision of peak measurements, minimize non-random noise and
326.0-33
-------
improve peak appearance, ensuring that all QC requirements for the method are
met. Olympic smoothing (25 points, 5 seconds with 1 iteration) was chosen using
peak area for quantitation because it was determined to have minimal effect on peak
height and/or area.(14) The use of alternate smoothing routines is acceptable
providing all QC criteria are met.
13. METHOD PERFORMANCE
13.1 Table 1 lists the standard conditions, typical retention times and single laboratory
Detection Limits in reagent water, as determined for each of the inorganic oxyhalide
DBFs and bromide.
13.2 Table 2 shows the precision and accuracy of the trace bromate measurement,
evaluated on both detectors, at two fortified concentrations, in reagent water (RW),
a simulated high ionic strength water (HIW) and a simulated high organic (HOW)
content water. The mean recovered bromate concentration (accuracy relative to the
fortified level) and the precision (expressed as %RSD of the replicate analyses) are
tabulated. The HIW was designed to simulate a high ionic strength field sample and
the HOW designed to simulate a high organic content field sample. The HIW was
prepared from reagent water which was fortified with the common anions of
chloride at 100 mg/L, carbonate at 100 mg/L, nitrate at 10.0 mg/L as nitrogen,
phosphate at 10.0 mg/L as phosphorous, and sulfate at 100 mg/L.(1) The HOW was
prepared from reagent water fortified with 1.0 mg/L humic acid.(1)
13.3 Table 3 summarizes the single laboratory accuracy (%Recovery) and precision (%
RSD) for each anion included in the method in a variety of waters for the standard
conditions identified in Table 1.
14. POLLUTION PREVENTION
14.1 For information about pollution prevention that may be applicable to laboratories
and research institutions, consult "Less is Better: Laboratory Chemical Management
for Waste Reduction," available from the American Chemical Society's Department
of Government Regulations and Science Policy, 1155 16th Street N.W.,
Washington D.C. 20036, (202) 872-4477.
15. WASTE MANAGEMENT
15.1 The analytical procedures described in this method generate relatively small
amounts of waste since only small amounts of reagents are used. The matrices of
concern are 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
326.0-34
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controlling all releases from fume hoods and bench operations. Also, 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, consult "The Waste Management Manual for
Laboratory Personnel" also available from the American Chemical Society at the
address in Section 14.1.
16. REFERENCES
1. U.S. EPA Method 300.1. "Determination of Inorganic Anions in Drinking Water by
Ion Chromatography". EPA Document number: EPA/600/R-98/118. NTIS number
PB98-169196INZ.
2. Glaser, J.A., D.L. Foerst, G.D. McKee, S.A. Quave, and W.L. Budde, "Trace
Analyses for Wastewaters," Environ. Sci. Technol. 1981, 15, 1426-1435.
3. Wagner, H..P., Pepich, B.V., Hautman, D.P. and Munch, D.J. "US Environmental
Protection Agency Method 326.0, a New Method for Monitoring Inorganic
Oxyhalides and Optimization of the Postcolumn Derivatization for the Selective
Determination of Trace Levels of Bromate." L Chro. A, 2002, 956, 93-101.
4. "OSHA Safety and Health Standards, General Industry," (29CFR1910).
Occupational Safety and Health Administration, OSHA 2206, (Revised, Jan. 1976).
5. ASTM Annual Book of Standards, Part II, Volume 11.01, D3370-82, "Standard
Practice for Sampling Water," American Society for Testing and Materials,
Philadelphia, PA, 1986.
6. "Carcinogens-Working with Carcinogens," Publication No. 77-206, Department of
Health, Education, and Welfare, Public Health Service, Center for Disease Control,
National Institute of Occupational Safety and Health, Atlanta, Georgia, August
1977.
7. "Safety In Academic Chemistry Laboratories," 3rd Edition, American Chemical
Society Publication, Committee on Chemical Safety, Washington, D.C., 1979.
8. Wagner, H..P., Pepich, B.V., Hautman, D.P. and Munch, D.J. "Improving the
Performance of EPA Method 300.1 for Drinking Water Compliance Monitoring."
J. Chrom. A.. Special Edition of the 2002 International Ion Chromatography
Smyposium (in press).
326.0-35
-------
9. Standard Methods for the Examination of Water and Wastewater, "Method 4500-
C1O2,C Amperometric Method I (for the determination of Chlorine Dioxide)," 19th
Edition of Standard Methods (1995).
10. Hautman, D.P. & Bolyard, M. "Analysis of Oxyhalide Disinfection By-products and
other Anions of Interest in Drinking Water by Ion Chromatography."_L Chrom. A,
1992, 602,65-74.
11. Wagner, H..P., Pepich, B.V., Hautman, D.P. and Munch, D.J. "Analysis of 500 ppt
Levels of Bromate in Drinking Waters Using Direct Injection Suppressed Ion
Chromatography with a Single, Pneumatically Delivered Postcolumn Reagent."_L
Chrom. A, 1999, 850, 119-129.
12. latrou, A. and Knocke, W.R. "Removing Chlorite by the Addition of Ferrous Iron".
Journal of the AWWA. Research and Technology, (November, 1992), 63-68.
13. Wagner, H..P., Pepich, B.V., Hautman, D.P. and Munch, D.J. "Eliminating the
Chlorite Interference in US Environmental Protection Agency Method 317.0 Permits
the Analysis of Trace Bromate Levels in all Drinking Water Matrices." L Chrom..
A, 2000, 882, 309-319.
14. Schibler, J.A., " Improving Precicion and Accuracy with Software-based Signal
Filtering". American Laboratory. (December, 1997), 63-64.
326.0-36
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17. TABLES. DIAGRAMS. FLOWCHARTS AND VALIDATION DATA
TABLE 1. CHROMATOGRAPHIC CONDITIONS AND METHOD DETECTION LIMITS IN
REAGENT WATER FOR THE INORGANIC OXYHALIDE DISINFECTION BY-
PRODUCTS AND BROMIDE.
Standard Conditions and Equipment(a):
Ion Chromatograph:
Sample Loop:
Eluent:
Eluent Flow:
Columns :
Typical System Backpressure:
Conductivity Suppressor:
PCR Suppressor:
Detectors:
Postcolumn Reagent Flow:
Postcolumn Reactor Coil:
Postcolumn Heater:
Postcolumn Regenerant
Total analysis time:
Dionex DX500
225 jiL
9.0 mM NajCOg
1.3 mL/min
Dionex AG9-HC / AS9-HC, 4 mm
2300 psi
ASRS-1, external water mode, 100 mA current for conductivity
ASRS-1 used with sulfuric acid regenrant to acidify the PCR
Dionex CD20 suppressed conductivity detector, background
conductivity: 24 [iS
Dionex AD20 Absorbance Detector, 10 mm cell path length, set at
352 nm (deuterium lamp)
0.4 mL/min
knitted, potted for heater, 500 uL internal volume
80 °C
150 mN H2SO4, 2.5 mL/min, effluent pH < 2
25 minutes
Analyte Retention Times and Detection Limits :
Analyte
Chlorite
Bromate (c)
Bromate (d)
Surrogate: DCA
Bromide
Chlorate
Retention Time
-------
TABLE 2. SINGLE LABORATORY PRECISION IN VARIOUS MATRICES FOR
BROMATE BY ABSORBANCE DETECTION.
Matrix Detection
Reagent Absorbance
Water
Absorbance
High Ionic Absorbance
Water
Absorbance
High Absorbance
Organic
Water Absorbance
PRECISION
Fortified
Cone.
(ng/L)
1.0
5.0
1.0
5.0
1.0
5.0
# of Reps.
8
8
8
8
7
8
Mean
(ng/L)
1.1
5.2
1.1
5.2
1.1
5.2
%
RSD
4.4
2.1
4.2
2.0
3.4
3.2
Standard Conditions: Same as listed in Table 1.
326.0-38
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TABLE 3. SINGLE-LABORATORY PRECISION AND RECOVERY FOR THE
INORGANIC DISINFECTION BY-PRODUCTS, BROMIDE AND
SURROGATE.
Analyte
Chlorite
Bromate by
Conductivity
Bromide
Chlorate
Surrogate
Matrix
RW
HIW
HOW
RW
HIW
HOW
RW
HIW
HOW
RW
HIW
HOW
RW
HIW
HOW
Fortified
Cone.
(ug/L)
100
500
100
500
100
500
10.0
25.0
10.0
25.0
10.0
25.0
10.0
25.0
10.0
25.0
10.0
25.0
100
500
100
500
100
500
1.00
1.00
1.00
#of
Replicates
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
Mean
% Recovery
107
108
102
106
99.3
107
102
99.8
103
92.9
101
97.6
97.5
104
108
104
104
99.7
111
104
99.0
100
101
105
108
106
103
105
108
108
%RSD
3.0
1.2
2.0
0.71
2.7
0.49
4.6
4.3
3.8
11
8.1
5.9
5.3
5.1
4.8
5.0
6.1
3.7
1.7
0.97
2.3
0.66
2.8
1.1
6.1
4.7
1.3
2.1
4.4
4.0
RW = Reagent Water; HIW = High Ionic Strength Water; HOW = High Organic Water
326.0-39
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TABLE 4. INITIAL DEMONSTRATION OF CAPABILITY QC REQUIREMENTS.
Reference
Requirement
Specification and Frequency
Acceptance Criteria
Sect. 9.2.1
and 9.4
Initial
Demonstration
of Low System
Background
Analyze a method blank (LRB) and
determine that all target analytes are
below l/2 of the proposed MRL prior to
performing the IDC
The LRB
concentration must be
< 1/3 of the proposed
MRL
Sect. 9.2.2
Initial
Demonstration
of Accuracy
(IDA)
Run mid-level QCS and determine
recovery.
Conductivity: analyze 7 replicate LFBs
recommend fortify at 20 ug/L
Absorbance: analyze 7 replicate LFBs
recommend fortify with bromate at 2.0
ug/L Calculate average recovery of IDA
replicates
QCS recovery must be
± 15% of true value.
Mean % recovery for
IDA replicates must
be± 15% of true
value.
Sect. 9.2.3
Initial
Demonstration
of Precision
(IDP)
Calculate the %RSD of the IDA
replicates.
%RSDmustbe<20%
Sect. 9.2.6
Detection Limit
Determination
Select a fortifying level at 3-5 times the
estimated instrument detection limit at or
lower than the MRL. Analyze 7
replicate LFBs
Calculate over at least 3 days using
equation in Section 9.2.6 - do not
subtract blank
Detection Limit must
be < 1/3 the MRL
326.0-40
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TABLE 5. QUALITY CONTROL REQUIREMENTS (SUMMARY).
Reference
Requirement
Specification and Frequency
Acceptance Criteria
Sect. 8.3
Sample Holding
Time /
Preservation
Bromate 28 days, refrig. at <6 °C /
EDA Preservation
Bromide 28 days, EDA Permitted
Chlorate 28 days, refrig. at <6 °C /
EDA Preservation
Chlorite 14 days, refrig. at <6 °C /
EDA Preservation
Holding time and
temperature must not be
exceeded. EDA added to all
samples
Sect. 9.4
Laboratory
Reagent Blank
(LRB)
Include LRB with every analysis
batch (up to 20 samples)
Analyze prior to analyzing field
samples
All analytes must be
< 1/3 MRL
Sect. 9.4.2
(specific
to PCR)
PRETREATED
Laboratory
Reagent Blank
REQUIRED in any analysis batch
which includes samples which have
been pretreated to remove chlorite
prior to PCR measurement of trace
bromate.
PCR measured bromate
< 1/3 MRL
Sect. 9.6
Laboratory
Fortified Blank
(LFB)
Laboratory must analyze LFB in
each analysis batch following the
first CCC. Calculate %REC prior to
analyzing samples
LFB recovery fortified at:
>MRLto5XMRL
= 75 - 125%
>5X MRL to highest CCC
= 85-115%
Sample results from batches
that fail LFB are invalid
Sect. 10.2
Initial
Calibration
Conductivity: generate calibration
curve using at least 5 standards
Absorbance: generate calibration
curve using at least 5 bromate
standards
The lowest calibration
standard MUST be at or
below the MRL
4 CAL standards should be
above the MRL
Sect. 9.5
and Sect.
10.3
Continuing
Calibration
Check (CCC)
Verify initial calibration by
analyzing a low level CCC prior to
analyzing samples. CCCs are then
injected after every 10 samples and
after the last sample, rotating
concentrations to cover the
calibrated range of the instrument.
Recovery for each analyte
must be 85-115% of the true
value for all but the lowest
level of calibration. The
lowest calibration level CCC
must be 75-125% of the true
value
All acceptable data MUST
be bracketed by valid CCCs
326.0-41
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TABLE 5. QUALITY CONTROL REQUIREMENTS (SUMMARY CONTINUED).
Reference
Requirement
Specification and Frequency
Acceptance Criteria
Sect. 9.7
Surrogate
Dichloroacetate is added to all blanks,
samples and standards
Surrogate recovery must
be 90-115%.
Samples that fail
surrogate recovery must
be reanalyzed. If second
analysis fails label result
as suspect/matrix
Sect. 9.8
Sect.
11.1.4.3
Laboratory
Fortified
Sample Matrix
(LFSM)
Must add known amount of each target
analyte to a minimum of 5% of field
samples or at least one within each
analysis batch for both detectors
LFSM must be fortified above the
native level and at no greater than 5 x
the highest field sample concentration
Calculate target analyte recovery using
formula (Sect. 9.8.2)
When field samples from chlorine
dioxide plants which contain chlorite
are pretreated prior to the PCR
measurement of trace bromate, an
additional LFSM must be prepared for
each pretreated field sample (Sect.
9.8.4)
Recovery should be
75 - 125%
If fortified sample fails
the recovery criteria,
label both as
suspect/matrix.
Sect. 9.9
Field Duplicate
(FD)
or
Laboratory
Fortified
Sample Matrix
Duplicate
(LFSMD)
Analyze either a FD or LFSMD for a
minimum of 5% of field samples or at
least one within each analysis batch for
both detectors.
Calculate the relative percent difference
(RPD) using formula in Section 9.9.1
The RPD for
concentrations at MRL
to 5 x MRL should be ±
20% on both detectors,
and ± 10% on both
detectors for
concentrations at 5 x
MRL to highest CCCs. If
this range is exceeded,
label both as
suspect/matrix
Sect. 9.10
Instrument
Performance
Check (IPC)
Calculate Peak Gaussian Factor (PGF)
using equation (Sect. 9.10.1) and
monitor retention time for surrogate in
the initial CCC each day
PGF must fall between
0.80 and 1.15
Ret. Time (RT) for
surrogate must remain
80% of initial RT when
column was new
326.0-42
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TABLE 6. EXAMPLE SAMPLE ANALYSIS BATCH WITH QUALITY CONTROL
REQUIREMENTS
Injection
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Sample
Description
Laboratory reagent blank (LRB)
ICCS conductivity detector (5.0 |j,g/L)
ICCS absorbance detector (0.5 ng/L)
Laboratory Fortified Blank (LFB) -
conductivity detector
LFB - absorbance detector
Field sample 1
Field sample 1 - Laboratory Duplicate (LD) (a)
Field sample 2
Field sample 2 - Laboratory Fortified Sample Matrix
(LFSM) (a) at concentrations specific for conductivity
detector
Field sample 2 - LFSM specific for trace bromate on the
absorbance detector
Field sample 3
Field sample 4
Field sample 5
Field sample 6
Field sample 7
Field sample 8
Field sample 9
Field sample 1 0
CCCS conductivity detector (75.0 jig/L)
CCCS absorbance detector (5.0 ug/L)
Field sample 1 1
Acceptance
Criteria
< 1/3 MRL
3.75 to 6.25 ng/L
0.375 to 0.625 (ig/L
± 25 % fortified level
± 25 % fortified level
± 15%RPD
± 25% fortified level
± 25% fortified level
63.8 to 86.3 (ig/L
4.25 to 5.75 ng/L
326.0-43
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22
23
24
25
26
27
28
29
30
31
32
33
34
Field sample 12
Field sample 1 3
Field sample 14 - (finished water from PWS using chlorine
dioxide)
Pretreate (Sect. 9.3.1.2) using the acid/Fe(II) chlorite
removal procedure (Sect. 11.1.4)
Field sample 14 (b) - (finished water from PWS using
chlorine dioxide) pretreated with acid/Fe(II) (Sect. 1 1.1.4)
Field sample 14 - (finished water from PWS using chlorine
dioxide) LFSM specific for trace bromate on the
absorbance detector, pretreated with acid/Fe(II) (Sect.
11.1.4.2)
Field sample 1 5
Field sample 1 6
Field sample 1 7
Field sample 1 8
Field sample 19(b)
ECCS conductivity detector (500.0 ug/L)
ECCS absorbance detector (15.0 ug/L)
< 1/3 MRL
± 25% fortified level
425 to 575 ug/L
12.8 to 17.3 ug/L
(a) If no analytes are observed above the MRL for a sample, an alternate sample which contains
reportable values should be selected as the laboratory duplicate. Alternately, the LFSM can be
selected and reanalyzed as the laboratory matrix duplicate ensuring the collection of QC data for
precision.
(b) Field sample #19 was the final field sample permitted in this batch but 20 total field samples were
analyzed.
Field sample #14 was analyzed both initially and as a acid/Fe (II) pretreated sample, therefore, it
accounted for two "field sample analyses" toward the maximum of twenty in an analysis batch (Sect.
3.1).
326.0-44
-------
Sample loop
1C System
(9.0mMCOj)
1C Guard & Analytical Columns
Conductivity
Suppressor
Autos ampler
PCR
Suppressor
PCR
Delivery
(Pneumatic)
Regenerant
(150mNH2SQ0
Regenerant to waste
Conductivity
Detector
Reaction coil @
Absorb ance
Detector
(352 nm)
Effluent to waste
Figure 1: Schematic detailing the configuration of postcolumn hardware addition to an ion
chromatograph. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use. If the requirements found in Section 9 are
met, equivalent products or hardware can be employed.
NOTE: In a typical Method 300.1 hardware configuration, a backpressure coil is
included after the conductivity cell as part of the waste stream when this
manufacture's equipment is used. These backpressure coils are not required when the
Method 326.0 instrument configuration is employed since the additional PCR system
components, placed in-line, function in the same capacity and provide sufficient
backpressure.
326.0-45
-------
0.500-r
0.400-
0.300-
0.200-
0.100-
0-
-0.100-
Suppressed Conductivity Detection
-0.200
r
0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0
Minutes
8.OOxlOT -•
4.00x10" -•
2.00x10- -•
UV/Vis Absorbance Detection
BrO,
\i
2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0
Minutes
Figure 2: Reaent water fortified with bromate at 10 ug/L on both detectors.
326.0-46
-------
Suppressed Conductivity Detection
0.500-
0.400-
0.300-
0.200-
C/l
i
0.100-
0-
-0.100-
-0.200-
(
|Br,(
u-ic\fii
Hp
1
^
L
1 ao3
;VliMLJl
3 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0
Minutes
UV/Vis Absorbance Detection
8.00xl03-r
e.ooxio3-
4.00x1 03 -
2.00xl03-
o-
2. OOxl O3-
0
C1O2
[
^E
r-v-^
rr\
I I V_^Q
' I
11
2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0
Minutes
Figure 3: Reagent water fortified with inorganic oxyhalide disinfection by-products and
bromide at 20.0 ug/L and bromate at 10 ug/L on both detectors.
326.0-47
------- |