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Haloacetic Acids – Standard Operating Procedure
PARAMETER
This SOP for the measurement of haloacetic acids (HAAs) follows a modified version of
Standard Method 6251B.1 It is required that Standard Method 6251B and “Quantification
of Nine Haloacetic Acids Using Gas Chromatography with Electron Capture Detection”
by Brophy, et. al., be studied along with this SOP prior to performance of the analysis.
This SOP applies to samples of surface water, ground water, finished water and water at
any intermediate drinking water treatment stage.
Haloacetic Acid Analyte
Bromochloroacetic Acid (BCAA)
Bromodichloroacetic Acid (BDCAA)
Chlorodibromoacetic Acid (CDBAA)
Dibromoacetic Acid (DBAA)
Dichloroacetic Acid (DCAA)
Monobromoacetic Acid (MBAA)
monochloroacetic Acid (MCAA)
Tribromoacetic Acid (TBAA)
Trichloroacetic Acid (TCAA)
CAS No.
5589-96-3
7113-314-7
5278-95-5
631-64-1
79-43-6
79-08-3
79-11-8
75-96-7
76-03-9
PRINCIPLE
The determination of HAAs in water samples is accomplished by liquid-liquid extraction,
derivatization and gas chromatography with micro electron capture detection. A 30 mL
volume of sample is adjusted to pH of less than 0.5 to extract the nondissociated acidic
compounds with 3 mL of methyl tert-butyl ether (MtBE). The extracted compounds are
methylated with diazomethane solution to produce methyl ester or ether derivatives.
The target analytes are identified and measured by capillary column gas
chromatography using a micro electron capture detector (GC/ECD). Analytes are
quantified using procedural standard quantification.
SAMPLE COLLECTION, PRESERVATION AND STORAGE
Vial Preparation
Use a clean and labeled 40 mL amber EPA vial with a TFE-lined screw cap. A clean vial
has been soap washed, rinsed with MQ and then baked. Add 65 mg of ammonium
chloride to the clean vial. This amount produces an ammonium chloride concentration
of 1625 mg/L in the sample.
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Sample Collection
Collect all samples in duplicate. Completely fill the vial with sample (headspace free) to
just overflowing, but take care not to flush out the buffer/dechlorination reagents. No air
bubbles should be trapped in the sample when the vial is sealed. This can be best
achieved by filling the sample vial just above the top and slip the septa on from the side.
Cap vials tightly.
Sample Storage
Until analysis, samples must be stored at 4°C with minimal exposure to light and
atmosphere. The sample storage area must be free of organic solvent vapors. Store
extract samples in a freezer until analysis. Extract all samples within 14 days of
collection and analyze within 7 days following extraction.
APPARATUS AND REAGENTS
Apparatus
Sample containers/extraction vials: 40 mL amber EPA vial with a TFE-lined screw cap.
Autosampler Vials: 2.0 mL vials with screw or crimp cap and a teflon-faced seal.
Standard solution storage containers: 10-20 mL glass vials with teflon lined-screw caps.
Pasteur pipets: Glass, disposable.
Solvent Repipetor: up to 10.0 mL delivery range
Volumetric flasks: 2mL, 10 mL.
Micro syringes: 10 µL, 25 µL, 50 µL, 100 µL, 250 µL and 500 µL.
Transfer pipets: 10 mL pipetor with disposable tips.
Orbital Mixer
Balance: analytical, capable of weighing to 0.001 g.
Gas chromatograph: Analytical system complete with gas chromatograph equipped for
electron capture detection, split/splitless capillary or direct injection, temperature
programming, differential flow control, and with all required accessories including
syringes, analytical columns and ultra high purity nitrogen gas. A data system is
recommended for measuring peak areas. An autoinjector is recommended for
improved precision of analyses. The gases flowing through the electron capture
detector should be vented through the laboratory fume hood system.
Primary GC column: DB-1 [fused silica capillary with chemically bonded
(Dimethlypolysiloxane)] column, 30m x 0.45m ID, 1.27 µm film thickness.
Diazomethane reaction chamber
Diazomethane reaction chamber holder: 500 mLerlenmeyer flask
Diazomethane reaction chamber ice bath: 800-1000 ml plastic beaker & 3 L crushed ice
Plastic syringe: 1 ml
Luer lock needle: 25 gauge, 5/8”
Erlenmeyer flask: 25 mL
Teflon tape
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Reagents
Reagent water -- Reagent water is defined as a water in which an interference is not
observed > than the MDL of each analyte of interest. A Millipore Milli-Q water system is
used to generate deionized reagent water.
Methanol -- High purity, demonstrated to be free of analytes and interferences. Maintain
records of the reagent’s manufacturer.
HAA standards – The stock standard solution used is purchased as an ampulized
solution in methanol from Supelco (Catalog # 4-7787)
Surrogate – The stock standard solution (2-bromopropionic acid) used is purchased as
an ampulized solution in MTBE from AccuStandard Inc. (# M-552.1-SS).
Ammonium chloride, NH4Cl -- ACS reagent grade, used to convert free chlorine to
monochloramine.
Sodium sulfate, Na2SO4 – ACS reagent grade (granular, anhydrous). If interferences are
observed, it may be necessary to heat the sodium sulfate in a shallow tray at 400°C for
up to 4 hours to remove phthalates and other interfering organic substances. Store in a
capped glass bottle rather than a plastic container.
Methyl tert-butyl ether – High purity, demonstrated to be free of analytes and
interferences. Maintain records of the reagent’s manufacturer.
MNNG - 1-methyl-3-nitro-1-nitrosoguanidine
Sodium hydroxide, NaOH – ~5 N NaOH
QC PROCEDURES
Initial Demonstration of Capability (IDC)
The IDC is performed at least once, by each analyst, before analysis of any sample, to
demonstrate proficiency to perform the method. The following procedures are based on
Section 6 of the DBP/ICR Analytical Methods Manual2.
Initial Demonstration of Low System Background: Analyze a Method Blank (MB) to
verify that no contamination exists above ½ the minimum reporting levels (MRLs). The
MRL for each of the HAAs is listed in the following table.
Analyte
MBAA
DCAA
TCAA
BCAA
DBAA
BDCAA
MCAA
CDBAA
TBAA
MRL
1.0 g/L
2.0 g/L
4.0 g/L
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Initial Demonstration of Precision: Analyze a total of five samples of reagent water
fortified with each of the haloacetic acids at a concentration of 20 µg/L (Required
concentration non given in the ICR Methods Manual for the three additional HAAs:
BDCAA, CDBAA and TBAA). These five samples must be analyzed on five separate
days and must be of separate extraction and analysis batches. The relative standard
deviation (RSD) must be less than 20%.
Initial Demonstration of Accuracy: Calculate the average recoveries of the replicates in
the Initial Demonstration of Precision. The averages must be within +/- 20% of the
theoretical amount.
Method Detection Limit (MDL) Determination
Prepare a sample with fortifying concentrations at the MRLs for each of the HAAs. The
following procedure is based from Standard Methods 1030 C1. Analyze seven portions
of this solution over a period of at least 3 d to ensure that MDL determination is more
representative than measurements performed sequentially. Calculate the standard
deviation to the replicate analysis. From a table of the one-sided t distribution select the
value of t for 7 – 1 = 6 degrees of freedom and at the 99% confidence level. This value
is 3.14. The product of 3.14 times the standard deviation is the MDL.
Method Blank
Each time a set of samples is extracted or reagents are changed, a method blank (MB)
must be analyzed. If the MB (Milli-Q) produces an interference peak within the retention
time window of any analyte that would prevent the determination of that analyte or a
peak of concentration greater than ½ the MRL for that analyte, the analyst must
determine the source of contamination and eliminate the interference before processing
samples. Field samples of an extraction set associated with an MB that has failed the
specified criteria are considered suspect.
Matrix Spike
Chlorinated water supplies will usually contain significant background concentrations of
several method analytes. The concentrations may be equal to or greater than the
fortified concentrations. Relatively poor accuracy and precision may be anticipated
when a large background must be subtracted. For many samples, the concentrations
may be so high that fortification may lead to a final extract with instrumental responses
exceeding the linear range of the electron capture detector. If this occurs, the extract
must be diluted. In spite of these problems, sample sources should be fortified and
analyzed as described below. By fortifying sample matrices and calculating analyte
recoveries, any matrix induced analyte bias is evaluated.
The laboratory must add known concentrations of analytes to 10 % of the samples. The
concentrations should be equal to or greater than the background concentrations in the
sample selected for fortification. Acceptable fortification concentrations according to the
ICR Methods Manual are 20 µg/L and 40 µg/L.
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Calculate the mean percent recovery, R, of the concentration for each analyte, after
correcting the total mean measured concentration, A, from the fortified sample for the
back-ground concentration, B, measured in the unfortified sample, i.e.:
R = 100 (A - B)/C
where C is the fortifying concentration. U.S.EPA Method 551.1 requires the recoveries of
all analytes must fall within 80-120%. If a recovery falls outside of this acceptable range,
a matrix induced bias can be assumed for the respective analyte and the data for that
analyte must be reported to the data user as suspect.
Surrogate
The surrogate standard is fortified into the aqueous portion of all samples and laboratory
reagent blanks. The surrogate is used to measure the efficiency of the sample
derivatization and extraction. U.S.EPA Method 552.2 lists acceptance criteria of 70130%.
When surrogate recovery from a sample, blank or calibration check is outside these
limits check (1) calculations to locate possible errors, (2) standard solutions for
degradation, (3) possible sources for contamination, and (4) instrument performance. If
those steps do not reveal the cause of the problem, reanalyze the extract. If the extract
reanalysis meets the surrogate recovery criterion, report only data for the reanalyzed
extract. If the extract reanalysis fails the recovery criterion, the analyst should check the
calibration by analyzing the most recently acceptable calibration check standard. If the
calibration check fails criteria, recalibration is in order. If the calibration check is
acceptable, it may be necessary to extract another aliquot of sample. If the sample reextract also fails the recovery criterion, report all data for that sample as suspect.
Duplicate Analysis
Ten percent (10%) of samples will be analyzed in duplicate. Duplicate results must not
reflect a relative percent difference (RPD) greater that 25% for any one analyte and the
RPD for 90% of the analytes being determined must be less than 20%. If this criteria is
not met the analysis must be repeated.
Solvent Blank
Each analysis run must be started with an MTBE solvent blank. This is a check on the
extraction solvent as well as on the instrument system.
Second Source Calibration
An additional calibration standard is extracted and analyzed alongside every calibration
curve that is to be used. This additional calibration standard is purchased from a supplier
different from the one used to purchase the standards used in preparation of the
calibration curve. Percent recoveries are calculated for the second source calibration
standard. These recoveries must fall within the range of 70-130 % in order for the initial
calibration curve to be considered valid.
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Calibration Check
If an initial calibration is not run on a particular analysis day, the calibration check must
be run and matched to the previous calibration curve to ensure that the instrument is still
within calibration. In order for the calibration check to be considered valid, recoveries
must fall between 50% and 150% for all the target analytes when quantified using the
previous calibration curve. Furthermore, a calibration check must be analyzed after
every tenth sample analysis, after the final sample analysis and recoveries must fall
between 80% and 120% for all the target analytes to be considered acceptable. At least
one calibration check must be extracted with each set of samples. Calibration check
standards need not necessarily be different extracts but can be injections from the same
extract as long as the holding time requirements are met.
STANDARDS AND CALIBRATION
Preparing a Primary Standard
The primary dilution standard is prepared by diluting the ampulized stock standard
solution in methanol. The species concentrations in the ampulized stock standard
solution are listed in the following table.
HAA Species
TCAA, DBAA
MBAA, BCAA, BDCAA
MCAA, DCAA
DBCAA
TBAA
Ampulized Stock Standard
Concentration (g/L)
200,000
400,000
600,000
1,000,000
2,000,000
Primary Standard
Concentration (g/L)
20,000
40,000
60,000
100,000
200,000
Rinse syringe with small amount of high concentration standard. Dispense 500 µL into a
5 mL volumetric flask partially filled with methanol. Ensure the needle is submerged in
methanol at bottom of flask. Fill the flask with methanol to the 5 mL mark. Mix by
inversion. The species concentrations in the primary dilution standard are listed in the
above table. Methanol is used due to its miscibility with water. But the primary
standard is only good for 24 hours due to the spontaneous methylation of haloacetic
acids when stored in methanol.
Preparing Secondary Standards
Secondary standards are prepared by the addition of specific volumes of the primary
dilution standard to separate 72 mL volumes of reagent water. These aqueous
standards are treated, including extraction, in the same manner as the samples.
Fill clean and labeled 72 mL clear bottles with Milli-Q reagent water to top so no
headspace is present. This can be best achieved by filling the sample bottle just above
the top and slip the septa on from the side. Cap bottles. Bottles do not exactly contain
72 mL. So to determine exact volumes, weigh the capped labeled bottle (w/ septa)
before and after adding reagent water and then determine the actual contained volume
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by using the density of H2O. Place a 5/8” – 25 guage needle in the septa of the vial. The
following table lists the required primary standard volumes assuming the total secondary
standard volume in the vials are 72 mL.
Level
Level 0
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Standard
Volume
(mL)
72
72
72
72
72
72
72
72
Primary Standard
Volume to add
(L)
0
1.8
3.6
18
36
72
144
288
Syringe
to Use
TCAA
DBAA
N/A
10
10
25
50
100
250
500
0
0.5
1.0
5.0
10
20
40
80
Secondary Standards (g/L)
MBAA
MCAA DBCAA
BCAA
DCAA
BDCAA
0
0
0
1.0
1.5
2.5
2.0
3.0
5.0
10
15
25
20
30
50
40
60
100
80
120
200
160
240
400
TBAA
0
5.0
10.0
50
100
200
400
800
Level 1 represents concentrations near the MRL for each analyte. Levels 3 and 4 are
used as calibration checks.
Inject the appropriate dose with the injection needle plunged to the bottom of the sample
bottle. The liquid injected will rise, due to initial density differences between methanol
and H2O, so start the injection with the bottle inverted. Then rotate the bottle during
injection to ensure better mixing and to ensure that no dosing solution exits the exhaust
needle. The dose volume will displace an equal amount of sample out the 5/8” needle.
5/8” exhaust needle
Injection syringe
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Surrogate Standard Solution
The surrogate stock standard solution (2-bromopropionic acid) is purchased from
AccuStandard (# M-552.1-SS) at a concentration 1,000,000 g/l. in MTBE. From this
stock standard solution, a primary dilution standard is prepared in methanol at a
concentration of 25,000 µg/l. A volume of 30 µL of this primary dilution standard is
spiked into each blank, sample, calibration standard and QC sample, to a final
concentration of 25 µg/l.
Matrix Spiking Standard Solution
A volume of 20 or 40 µL of the primary standard is used in the fortification of the
duplicate sample. Consideration should be given to attempting to fortify at
concentrations above those expected in the sample.
Calibration of Instrument
Each analysis run should be started with an MtBE solvent blank. This is a check on the
extraction solvent as well as on the instrument system. If this run is acceptable, the
extracts for the calibration curve are analyzed (2 µL injection volume). The
Chemstation Chromatography Software System is used to generate a calibration curve
by plotting the areas (Aan) against the concentrations (Can). The curve can be defined as
either first or second order. Correlation coefficients must be greater than 0.990.
ANALYTICAL PROCEDURE
Diazomethane Preparation Procedure
PRECAUTIONS!!!
MNNG and the gas produced are very dangerous! ALWAYS handle in hood with proper
personal protection equipment and training!
1. Tilt reactor so hole in reactor stem is facing up. It is important to make sure all
additions to the reactor stem do not go through the hole.
2. Add the MNNG to the base of the reactor stem up to the fill line (~1 g)
Reactor Stem
Fill line
MNNG
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3. Add ~1 ml MQ water to reactor stem to moisten the MNNG and firmly screw on cap
w/ septa.
4. Add 6 ml MtBE to reactor base
5. Place reactor stem in the reactor base with O-ring sandwiched in between glass
flange. Wrap Teflon tape around the reactor at the O-ring and clamp tightly. Wrap
Teflon tape around the cap.
6. Prepare an ice bath in a 800 ml plastic beaker. Place reactor in ice bath and allow
reactor to reach thermal equilibrium
7. Plunge ~25 gauge needle through septa in reactor stem. Add ~1 ml of NaOH very
slowly in a drop wise fashion (until all MNNG is gone). [Reaction is Extremely
Exothermic!]. Be sure to keep pressure on the syringe since significant pressure
builds up inside reactor. Be sure to maintain good heat transfer to the ice bath.
8. Allow ~30 minutes for reaction completion while in the ice bath. The outside MtBE
solution should turn a moderate or deep yellow. If this does not occur, the solution is
no good.
9. Allow the pressure to slowly release by loosening the cap first. Transfer
diazomethane to 25 ml erlenmeyer flask. Keep the diazomethane cold and use as
soon as possible after preparation. If bubbles form following addition of the
diazomethane to the sample, then diazomethane solution is good!
Extraction Procedure
1. Remove the samples from storage and allow them to equilibrate to room
temperature.
2. Remove the aqueous sample to the prescored 30 mL mark on each sample vial.
3. Add 30 L of the surrogate standard (25,000 g/L 2-bromoacetic acid in methanol).
Mix by slowly and carefully inverting the sample vial two times with minimal sample
agitation.
4. Adjust the pH to less than 0.5 by adding 1 ml of concentrated sulfuric acid via a glass
pipette.
5. Add 13.0 g of sodium sulfate and 3.0 ml of MTBE (via bottle top pipetor). Sodium
sulfate is added to increase the ionic strength of the aqueous phase and thus further
drive the haloacetic acids into the organic phase. The addition of the salt should be
done quickly so that the heat generated from the addition of the acid will help
dissolve the salts.
6. Recap vial and mix for 30 seconds on an orbital mixer (until most of the salts are
dissolved).
7. Let stand for ~ 15 minutes for separation.
8. Transfer exactly 2 ml of the top organic layer with a pasteur pipette and add to a 2
ml volumetric flask.
Organic Layer
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9. Place the 2 mL volumetric flask containing the sample into the freezer for 25-30
minutes.
10. Add 250 mL of diazomethane via the glass syringe and mix gently by inverting once.
11. Place sample in 4C refrigerator for 15 minutes during esterification.
12. Remove sample and allow it to reach room temperature for 15 minutes.
13. Add approximately 10 mg of silica gel to sample to stop reaction (when bubbles stop
forming upon the addition of silica gel, the reaction is complete)
14. Transfer sample to GC vial and cap.
15. Analyze samples as soon as possible.
Remove 10 ml
13 g Na2SO4
1 mL H2SO4
3 ml MtBE
30 L
Surrogate
1)
2)
3)
1)
2)
~2 ml organic
layer
Cap vial
Mix 30 sec.
Stand 15 min.
250 l diazomethane
mix by 1 inversion
25-30 min.
in freezer
15 min. in
4oC frig.
~2 ml organic
layer
~10 mg
silica gel
15 min. room
temp
equilibration
transfer to
GC vial
Gas Chromatography
1. The temperature program utilized is as follows: 50°C initial temperature, 1 minute
hold time, then a 4°C/minute ramp to 158°C with a 0 minute hold time, and finally a
4°C/minute ramp to 230°C final temperature with a 5 minute hold time. This represents
a 34.8 minute run time.
2. Calibrate the system daily by either the analysis of a calibration curve or a continuing
calibration check.
3. Inject 2 µL of the sample extract. Use the Chemstation chromatography system to
record the resulting peak sizes in area units.
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4. If the response for the peak exceeds the calibration curve or the working range of the
detector, dilute the extract and re-analyze. The analyst must not extrapolate beyond the
calibration range established.
DATA REDUCTION, VALIDATION AND REPORTING
Identify sample components by comparison of retention times to retention data from the
calibration standard analysis. If the retention time of an unknown peak corresponds,
within limits, to the retention time of a standard compound, then the identification is
considered positive. Calculate analyte concentrations from the calibration curve.
Retention time windows are given as +/- three times the standard deviation obtained in
calculating the average retention time of the initial calibration curve. However, the
experience of the analyst should weigh heavily in the interpretation of the chromatogram.
PREVENTATIVE MAINTAINANCE
Gas purge flow should be left on at all times, with or without GC use to prevent the inflow
of oxygen and resulting contamination/oxidation of parts. The flow can be lowered
though in times of dormancy. The oven can be shut off if the GC is not used for an
extended period of time (i.e. months).
Short term Maintenance (Every time)
Compressed ultra high purity nitrogen gas tanks are checked daily for content (pounds
per square inch-psi) and are replaced when the contents fall below 500 psig. Every time
a gas tank is changed out, this should be noted on the oxygen trap, which has a limited
capacity.
Long term Maintenance (Months)
Glass liner: The glass liner, located in the injection inlet, should be replaced ~ once a
year or when used up. When it is used the glass wool inside it will have a darker color
Rubber injection seal: The rubber seal, located at the top of the injection inlet, should be
replaced every 3-4 months
Gold seal: The gold seal, located at the bottom of the injection inlet under the glass
liner, should be checked ~ every 6 months for carbon build-up. It is accessed from
inside the oven.
Column Burn: The column should be burned off every 3-12 months, depending on use.
This elutes off any constituents that may be more difficult to remove. A chromatogram is
produced showing eluted constituents. A 5-7 hour burn is sufficient. The burn temp
should be ~50o C less than the max column temperature reported on the box.
Very Long term Maintenance (Years)
Moisture Trap: will need regeneration when exhausted
Oxygen Trap: the high capacity (2 L of oxygen) trap will need replacement after ~18
tanks of gas used
ECD Detector: will need servicing every 3-10 or so years.
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Gas flow rates: should be checked annually.
Specific maintenance on an improperly functioning part is recorded on the GC
Maintenance Form.
SAFETY
1. The toxicity or carcinogenicity of each reagent used in this method has not been
precisely defined, however, each chemical compound must be treated as a potential
health hazard. From this viewpoint, exposure to these chemicals must 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 material safety data sheets should also be made available to all
personnel involved in the chemical analysis.
2. The toxicity of the extraction solvent, MtBE, has not been well defined. Susceptible
individuals may experience adverse affects upon skin contact or inhalation of vapors.
Therefore protective clothing and gloves should be used and MtBE should be used only
in a chemical fume hood or glove box. The same precaution applies to pure standard
materials.
INTERFERENCES
1. Method interferences may be caused by contaminants in solvents, reagents,
glassware and other sample processing apparatus that lead to discrete artifacts or
elevated baselines in chromatograms. All reagents and apparatus must be routinely
demonstrated to be free from interferences under the conditions of the analysis by
analyzing method blanks. Subtracting blank values from sample results is not permitted.
2. The use of high purity reagents and solvents helps to minimize interference
problems. Solvent blanks should be analyzed for each new bottle of solvent before use.
An interference free solvent is a solvent containing no peaks yielding data at > MDL and
at the retention times of the analytes of interest.
3. Interfering contamination may occur when a sample containing low concentrations of
analytes is analyzed immediately following a sample containing relatively high
concentrations of analytes. Routine between-sample rinsing of the sample syringe and
associated equipment with MtBE can minimize sample cross-contamination. After
analysis of a sample containing high concentrations of analytes, one or more injections
of MtBE should be made to ensure that accurate values are obtained for the next
sample.
4. Matrix interferences may be caused by contaminants that are co-extracted from the
sample. The extent of matrix interferences will vary considerably from source to source,
depending upon the water sampled.
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DEFINITIONS
1. SURROGATE ANALYTE -- A compound which is added to a sample aliquot in known
amount(s) before extraction or other processing and is measured with the same
procedure used to measure other sample components. The purpose of the surrogate is
to monitor method performance with each sample.
2. LABORATORY DUPLICATES -- Two aliquots of the same sample designated as
such in the laboratory. Each aliquot is extracted, derivatized and analyzed separately
using identical procedures. Analysis of these duplicates indicates the precision
associated with laboratory procedures, but not with sample collection, preservation or
storage procedures.
3. FIELD DUPLICATES -- Two separate samples collected at the same time and place
under identical circumstances and treated exactly the same throughout field and
laboratory procedures. Analysis of these duplicates gives a measure of the precision
associated with sample collection, preservation and storage, as well as with laboratory
procedures.
4. METHOD BLANK (MB) -- An aliquot of reagent water or other blank matrix that is
treated exactly as a sample including exposure to all glassware, equipment, solvents,
reagents, internal standards, and surrogates that are used with other samples. The MB
is used to determine if method analytes or other interferences are present in the
laboratory environment, the reagents, or the apparatus.
5. MATRIX SPIKE (MS) -- An aliquot of an environmental sample to which known
quantities of the method analytes are added in the laboratory. The MS 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 MS corrected for background concentrations.
6. STOCK STANDARD – Neat material or a commercially purchased concentrated
solution used in the calibration process
7. PRIMARY DILUTION STANDARD -- A solution of the target analyte(s) prepared in
the laboratory from stock standard solutions and diluted as needed to prepare
secondary standards.
8. SECONDARY STANDARD -- A solution prepared from the primary dilution standard
and used to calibrate the instrument response with respect to analyte concentration.
9. SECOND SOURCE STANDARD – A solution of method analytes of known
concentration which is used to fortify an aliquot of reagent water. It is obtained from a
source different from that of the standards used to calibrate and is used as a check on
the accuracy of standards being used to calibrate the analytical instrumentation.
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10. METHOD DETECTION LIMIT (MDL) -- The minimum concentration of an analyte
that can be identified, measured and reported with 99% confidence that the analyte
concentration is greater than zero.
11. 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.
XI
INSTRUMENT SOFTWARE AND OPERATION
The Agilent GC Chemstation software (Rev. A.08.03 [847]) is used for data acquisition.
Method files are named as follows:
Sequence files are named as follows:
Data files are named as follows:
HAAMMDD.M
MMDDA.S
MMDDA00X.D
where MM = Month, DD = Day, X represents consecutive numbering
REFERENCES
1 APHA,
AWWA and WEF (1998) Standard Methods for the Examination of Water and
Wastewater 20th Edition, Washington, D.C.
2 USEPA
(1996) DBP/ICR Analytical Methods Manual, Office of Water, Cincinnati, OH.
3 USEPA
(1995) Method 552.2: Determination of haloacetic acids and dalapon in
drinking water by liquid-liquid extraction, derivatization and gas chromatography with
electron capture detection, In Methods for the Determination of Organic Compounds in
Drinking Water-Supplement III, EPA/600/R-95/131. Cincinnati, Ohio: National Exposure
Research Laboratory, USEPA Office of Research and Development.
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