Method 631
The Determination of Benomyl
and Carbendazim in Municipal
and Industrial Wastewater
-------
Method 631
The Determination of Benomyl and Carbendazim in Municipal and
Industrial Wastewater
1. Scope and Application
1.1 This method covers the determination of benomyl and carbendazim. The following
parameters can be determined by this method:
1.2 Benomyl cannot be determined directly by this method. Benomyl is hydrolyzed to
carbendazim, and both compounds are measured and reported as carbendazim.
1.3 This is a high-performance liquid chromatographic (HPLC) method applicable to the
determination of the compounds listed above in industrial and municipal discharges as
provided under 40 CFR 136.1. Any modification of this method beyond those expressly
permitted shall be considered a major modification subject to application and approval
of alternate test procedures under 40 CFR 136.4 and 136.5.
1.4 The method detection limit (MDL, defined in Section 15) for each parameter is 8.7 Hg/L.
The MDL for a specific wastewater may differ from those listed, depending upon the
nature of interferences in the sample matrix.
1.5 This method is restricted to use by or under the supervision of analysts experienced in
the use of liquid chromatography and in the interpretation of liquid chromatograms.
Each analyst must demonstrate the ability to generate acceptable results with this method
using the procedure described in Section 8.2.
1.6 When this method is used to analyze unfamiliar samples for either of the compounds
above, compound identifications should be supported by at least one additional
qualitative technique.
2. Summary of Method
2.1 A measured volume of sample, approximately 1 L, is acidified if necessary to hydrolyze
benomyl to carbendazim. The total carbendazim is extracted with methylene chloride
using a separatory funnel. The extract is dried and exchanged to methanol during
concentration to a volume of 10 mL or less. HPLC conditions are described which permit
the separation and measurement of total carbendazim in the extract by HPLC with a UV
detector.1,2
Parameter
Benomyl
Carbendazim
Storet No.
CAS No.
17804-35-2
10605-21-7
-------
Method 631
3. Interferences
3.1 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 liquid chromatograms. All reagents and apparatus must be routinely demonstrated
to be free from interferences under the conditions of the analysis by running laboratory
reagent blanks as described in Section 8.5.
3.1.1 Glassware must be scrupulously cleaned.3 Clean all glassware as soon as possible
after use by thoroughly rinsing with the last solvent used in it. Follow by
washing with hot water and detergent and thorough rinsing with tap and reagent
water. Drain dry, and heat in an oven or muffle furnace at 400°C for 15 to 30
minutes. Do not heat volumetric ware. Thermally stable materials, such as PCBs,
may not be eliminated by this treatment. Thorough rinsing with acetone and
pesticide-quality hexane may be substituted for the heating. After drying and
cooling, seal and store glassware in a clean environment to prevent any
accumulation of dust or other contaminants. Store inverted or capped with
aluminum foil.
3.1.2 The use of high-purity reagents and solvents helps to minimize interference
problems. Purification of solvents by distillation in all-glass systems may be
required.
3.2 Matrix interferences may be caused by contaminants that are coextracted from the
sample. The extent of matrix interferences will vary considerably from source to source,
depending upon the nature and diversity of the industrial complex or municipality
sampled. Unique samples may require cleanup approaches to achieve the MDL listed
in Section 1.
4. Safety
4.1 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 reduced to the lowest possible
level by whatever means available. 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 data handling sheets should also
be made available to all personnel involved in the chemical analysis. Additional
references to laboratory safety are available and have been identified4 6 for the
information of the analyst.
5. Apparatus and Materials
5.1 Sampling equipment, for discrete or composite sampling.
5.1.1 Grab-sample bottle: Amber borosilicate or flint glass, 1-L or 1-quart volume,
fitted with screw-caps lined with TFE-fluorocarbon. Aluminum foil may be
substituted for TFE if the sample is not corrosive. If amber bottles are not
available, protect samples from light. The container and cap liner must be
-------
Method 631
washed, rinsed with acetone or methylene chloride, and dried before use to
minimize contamination.
5.1.2 Automatic sampler (optional): Must incorporate glass sample containers for the
collection of a minimum of 250 mL. Sample containers must be kept refrigerated
at 4°C and protected from light during compositing. If the sampler uses a
peristaltic pump, a minimum length of compressible silicone rubber tubing may
be used. Before use, however, the compressible tubing must be thoroughly rinsed
with methanol, followed by repeated rinsings with reagent water to minimize the
potential for contamination of the sample. An integrating flow meter is required
to collect flow-proportional composites.
5.2 Glassware. (All specifications are suggested. Catalog numbers are included for
illustration only.)
5.2.1 Separatory funnel: 250-mL, with TFE-fluorocarbon stopcock, ground-glass or TFE
stopper.
5.2.2 Drying column: Chromatographic column 400 mm long by 19 mm ID with
coarse-fritted disc.
5.2.3 Concentrator tube, Kuderna-Danish: 10-mL, graduated (Kontes K-570050-1025 or
equivalent). Calibration must be checked at the volumes employed in the test.
Ground-glass stopper is used to prevent evaporation of extracts.
5.2.4 Evaporative flask, Kuderna-Danish: 500-mL (Kontes K-570001-0500 or
equivalent). Attach to concentrator tube with springs.
5.2.5 Snyder column, Kuderna-Danish: Three-ball macro (Kontes K-503000-0121 or
equivalent).
5.2.6 Vials: Amber glass, 10- to 15-mL capacity with TFE-fluorocarbon-lined screw-cap.
5.3 Boiling chips: Approximately 10/40 mesh. Heat at 400°C for 30 minutes or perform a
Soxhlet extraction with methylene chloride.
5.4 Water bath: Heated, with concentric ring cover, capable of temperature control (±2°C).
The bath should be used in a hood.
5.5 Balance: Analytical, capable of accurately weighing to the nearest 0.0001 g.
5.6 Liquid chromatograph: High-performance analytical system complete with high pressure
syringes or sample injection loop, analytical columns, detector and strip-chart recorder.
A guard column is recommended for all applications.
5.6.1 Column: 30 cm long by 4 mm ID stainless steel, packed with |i Bondapak C18 (10
|i) or equivalent. This column was used to develop the method performance
statements in Section 14. Alternative columns may be used in accordance with
the provisions described in Section 12.1.
-------
Method 631
5.6.2 Detector: Ultraviolet, 254 nm. This detector has proven effective in the analysis
of wastewaters and was used to develop the method performance statements in
Section 14. Alternative detectors may be used in accordance with the provisions
described in Section 12.1.
6. Reagents
6.1 Reagent water: Reagent water is defined as a water in which an interferent is not
observed at the method detection limit of each parameter of interest.
6.2 Methylene chloride, methanol: Pesticide-quality or equivalent.
6.3 Sodium sulfate: ACS, granular, anhydrous. Condition by heating in a shallow tray at
400°C for a minimum of 4 hours to remove phthalates and other interfering organic
substances. Alternatively, heat 16 hours at 450 to 500°C in a shallow tray or perform a
Soxhlet extraction with methylene chloride for 48 hours.
6.4 Sodium hydroxide solution (ION): Dissolve 40g NaOH in reagent water and dilute to
100 mL.
6.5 Sulfuric acid solution (1 + 1): Slowly add 50 mL H2S04 (sp. gr. 1.84) to 50 mL of reagent
water.
6.6 Mobile phase: Methanol/water (1 + 1). Mix equal volumes of HPLC/UV quality
methanol and reagent water.
6.7 Stock standard solution (1.00 y\g/pL): The stock standard solution may be prepared from
a pure standard material or purchased as a certified solution.
6.7.1 Prepare the stock standard solution by accurately weighing approximately 0.0100
g of pure carbendazim. Dissolve the material in HPLC/UV quality methanol and
dilute to volume in a 10-mL volumetric flask. Larger volumes may be used at the
convenience of the analyst. If compound purity is certified at 96% or greater, the
weight may be used without correction to calculate the concentration of the stock
standard. Commercially prepared stock standards may be used at any
concentration if they are certified by the manufacturer or by an independent
source.
6.7.2 Transfer the stock standard solution into a TFE-fluorocarbon-sealed screw-cap
vial. Store at 4°C and protect from light. Frequently check stock standard
solutions for signs of degradation or evaporation, especially just prior to
preparing calibration standards from them.
6.7.3 The stock standard solution must be replaced after 6 months, or sooner if
comparison with a check standard indicates a problem.
-------
Method 631
7. Calibration
7.1 Establish HPLC operating parameters equivalent to those indicated in Table 1. The
HPLC system may be calibrated using either the external standard technique (Section 7.2)
or the internal standard technique (Section 7.3).
7.2 External standard calibration procedure.
7.2.1 Prepare calibration standards at a minimum of three concentration levels by
adding accurately measured volumes of carbendazim stock standard to
volumetric flasks and diluting to volume with methanol. One of the external
standards should be representative of a concentration near, but above, the method
detection limit. The other concentrations should correspond to the range of
concentrations expected in the sample concentrates or should define the working
range of the detector.
7.2.2 Using injections of 10 |iL of each calibration standard, tabulate peak height or
area responses against the mass injected. The results can be used to prepare a
calibration curve for carbendazim. Alternatively, the ratio of the response to the
mass injected, defined as the calibration factor (CF), may be calculated for
carbendazim at each standard concentration. If the relative standard deviation
of the calibration factor is less than 10% over the working range, the average
calibration factor can be used in place of a calibration curve.
7.2.3 The working calibration curve or calibration factor must be verified on each
working shift by the measurement of one or more calibration standards. If the
response for any parameter varies from the predicted response by more than
±10%, the test must be repeated using a fresh calibration standard. Alternatively,
a new calibration curve or calibration factor must be prepared.
7.3 Internal standard calibration procedure: To use this approach, the analyst must select an
internal standard similar to carbendazim in analytical behavior. The analyst must further
demonstrate that the measurement of the internal standard is not affected by method or
matrix interferences. Due to these limitations, no internal standard applicable to all
samples can be suggested.
7.3.1 Prepare calibration standards at a minimum of three concentration levels of
carbendazim by adding volumes of stock standard to volumetric flasks. To each
calibration standard, add a known constant amount of internal standard, and
dilute to volume with methanol. One of the standards should be representative
of a concentration near, but above, the method detection limit. The other
concentrations should correspond to the range of concentrations expected in the
sample concentrates, or should define the working range of the detector.
7.3.2 Using injections of 10 |iL of each calibration standard, tabulate the peak height or
area responses against the concentration for each compound and internal
standard. Calculate response factors (RF) for each compound as follows:
-------
Method 631
RF =
Equation 1
C4) (CJ
<4 J (CJ
where
As = Response for the parameter to be measured
Ats = Response for the internal standard
Cts = Concentration of the internal standard, in jig/L
Cs = Concentration of the parameter to be measured, in jig/L
If the RF value over the working range is constant, less than 10% relative
standard deviation, the RF can be assumed to be invariant and the average RF
may be used for calculations. Alternatively, the results may be used to plot a
calibration curve of response ratios, As/Ais against RF.
7.3.3 The working calibration curve or RF must be verified on each working shift by
the measurement of one or more calibration standards. If the response for
carbendazim varies from the predicted response by more than ±10%, the test must
be repeated using a fresh calibration standard. Alternatively, a new calibration
curve must be prepared.
7.4 Before using any cleanup procedure, the analyst must process a series of calibration
standards through the procedure to validate elution patterns and the absence of
interference from the reagents.
8. Quality Control
8.1 Each laboratory using this method is required to operate a formal quality control
program. The minimum requirements of this program consist of an initial demonstration
of laboratory capability and the analysis of spiked samples as a continuing check on
performance. The laboratory is required to maintain performance records to define the
quality of data that is generated.
8.1.1 Before performing any analyses, the analyst must demonstrate the ability to
generate acceptable accuracy and precision with this method. This ability is
established as described in Section 8.2.
8.1.2 In recognition of the rapid advances occurring in chromatography, the analyst is
permitted certain options to improve the separations or lower the cost of
measurements. Each time such modifications to the method are made, the analyst
is required to repeat the procedure in Section 8.2.
-------
Method 631
8.1.3 The laboratory must spike and analyze a minimum of 10% of all samples to
monitor continuing laboratory performance. This procedure is described in
Section 8.4.
8.2 To establish the ability to generate acceptable accuracy and precision, the analyst must
perform the following operations.
8.2.1 Select a representative spike concentration for each compound to be measured.
Using stock standards, prepare a quality control check sample concentrate of
either benomyl or carbendazim in methanol, 1000 times more concentrated than
the selected concentrations.
8.2.2 Using a pipette, add 1.00 mL of the check sample concentrate to each of a
minimum of four 1000-mL aliquots of reagent water. A representative
wastewater may be used in place of the reagent water, but one or more additional
aliquots must be analyzed to determine background levels, and the spike level
must exceed twice the background level for the test to be valid. Analyze the
aliquots according to the method beginning in Section 10.
8.2.3 Calculate the average percent recovery (R), and the standard deviation of the
percent recovery (s), for the results. Wastewater background corrections must be
made before R and s calculations are performed.
8.2.4 Using the appropriate data from Table 2, determine the recovery and single-
operator precision expected for the method, and compare these results to the
values calculated in Section 8.2.3. If the data are not comparable, review potential
problem areas and repeat the test.
8.3 The analyst must calculate method performance criteria and define the performance of
the laboratory for each spike concentration and parameter being measured.
8.3.1 Calculate upper and lower control limits for method performance as follows:
Upper Control Limit (UCL) = R + 3s
Lower Control Limit (LCL) = R - 3s
where R and s are calculated as in Section 8.2.3. The UCL and LCL can be used
to construct control charts7 that are useful in observing trends in performance.
8.3.2 The laboratory must develop and maintain separate accuracy statements of
laboratory performance for wastewater samples. An accuracy statement for the
method is defined as R ± s. The accuracy statement should be developed by the
analysis of four aliquots of wastewater as described in Section 8.2.2, followed by
the calculation of R and s. Alternatively, the analyst may use four wastewater
data points gathered through the requirement for continuing quality control in
Section 8.4. The accuracy statements should be updated regularly.7
8.4 The laboratory is required to collect in duplicate a portion of their samples to monitor
spike recoveries. The frequency of spiked sample analysis must be at least 10% of all
samples or one spiked sample per month, whichever is greater. One aliquot of the
-------
Method 631
sample must be spiked and analyzed as described in Section 8.2. If the recovery for
benomyl or carbendazim does not fall within the control limits for method performance,
the results reported for that parameter in all samples processed as part of the same set
must be qualified as described in Section 13.3. The laboratory should monitor the
frequency of data so qualified to ensure that it remains at or below 5%.
8.5 Before processing any samples, the analyst must demonstrate through the analysis of a
1-L aliquot of reagent water that all glassware and reagent interferences are under
control. Each time a set of samples is extracted or there is a change in reagents, a
laboratory reagent blank must be processed as a safeguard against laboratory
contamination.
8.6 It is recommended that the laboratory adopt additional quality assurance practices for
use with this method. The specific practices that are most productive depend upon the
needs of the laboratory and the nature of the samples. Field duplicates may be analyzed
to monitor the precision of the sampling technique. When doubt exists over the
identification of a peak on the chromatogram as carbendazim, confirmatory techniques
such as chromatography with a dissimilar column, or ratio of absorbance at two or more
wavelengths may be used. Whenever possible, the laboratory should perform analysis
of standard reference materials and participate in relevant performance evaluation
studies.
9. Sample Collection, Preservation, and Handling
9.1 Grab samples must be collected in glass containers. Conventional sampling practices8
should be followed; however, the bottle must not be prerinsed with sample before
collection. Composite samples should be collected in refrigerated glass containers in
accordance with the requirements of the program. Automatic sampling equipment must
be as free as possible of plastic and other potential sources of contamination.
9.2 The samples must be iced or refrigerated at 4°C from the time of collection until
extraction.
9.3 All samples must be extracted within 7 days and completely analyzed within 40 days of
extraction.
10. Sample Extraction
10.1 Using a 250-mL graduated cylinder, measure 150 mL of well-mixed sample into a 250-mL
Erlenmeyer flask. If benomyl is a potentiality in the sample, continue with Section 10.2.
If only carbendazim is to be measured, proceed directly to Section 10.3.
10.2 Carefully add 2 mL of 1+1 sulfuric acid and a TFE-fluorocarbon covered magnetic stirring
bar to the sample. Check the sample with wide-range pH paper to insure that the pH
is less than 1.0. Stir at room temperature for 16 to 24 hours.
10.3 Adjust the sample pH to within the range of 6 to 8 with sodium hydroxide. Pour the
entire sample into a 250-mL separatory funnel.
-------
Method 631
10.4 Add 60 mL methylene chloride to the separatory funnel and extract the sample by
shaking the funnel for 2 minutes with periodic venting to release excess pressure. Allow
the organic layer to separate from the water phase for a minimum of 10 minutes. If the
emulsion interface between layers is more than one-third the volume of the solvent layer,
the analyst must employ mechanical techniques to complete the phase separation. The
optimum technique depends upon the sample, but may include stirring, filtration of the
emulsion through glass wool, centrifugation, or other physical methods. Collect the
methylene chloride extract in a 250-mL Erlenmeyer flask.
10.5 Add a second 60-mL volume of methylene chloride to the separatory funnel and repeat
the extraction procedure a second time, combining the extracts in the Erlenmeyer flask.
Perform a third extraction in the same manner.
10.6 Assemble a Kuderna-Danish (K-D) concentrator by attaching a 10-mL concentrator tube
to a 500-mL evaporative flask. Other concentration devices or techniques may be used
in place of the K-D if the requirements of Section 8.2 are met.
10.7 Pour the combined extract through a drying column containing about 10 cm of
anhydrous sodium sulfate, and collect the extract in the K-D concentrator. Rinse the
Erlenmeyer flask and column with 20 to 30 mL of methylene chloride to complete the
quantitative transfer.
10.8 Add one or two clean boiling chips to the evaporative flask and attach a three-ball
Snyder column. Prewet the Snyder column by adding about 1 mL methylene chloride
to the top. Place the K-D apparatus on a hot water bath, 60 to 65°C, so that the
concentrator tube is partially immersed in the hot water, and the entire lower rounded
surface of the flask is bathed with hot vapor. Adjust the vertical position of the
apparatus and the water temperature as required to complete the concentration in 15 to
20 minutes. At the proper rate of distillation, the balls of the column will actively chatter
but the chambers will not flood with condensed solvent. When the apparent volume of
liquid reaches 1 mL, remove the K-D apparatus and allow it to drain and cool for at least
10 minutes.
10.9 Increase the temperature of the hot water bath to 85 to 90°C. Momentarily remove the
Snyder column, add 50 mL of methanol and a new boiling chip and reattach the Snyder
column. Pour about 1 mL of methanol into the top of the Snyder column and
concentrate the solvent extract as before. Elapsed time of concentration should be 5 to
10 minutes. When the apparent volume of liquid reaches 1 mL, remove the K-D
apparatus and allow it to drain and cool for at least 10 minutes.
10.10 Remove the Snyder column and rinse the flask and its lower joint into the concentrator
tube with 1 to 2 mL of methanol and adjust the volume to 10 mL. A 5-mL syringe is
recommended for this operation. Stopper the concentrator tube and store refrigerated
if further processing will not be performed immediately. If the extracts will be stored
longer than 2 days, they should be transferred to TFE-fluorocarbon-sealed screw-cap
vials. Proceed with HPLC analysis.
11.
Cleanup and Separation
-------
Method 631
11.1 Cleanup procedures may not be necessary for a relatively clean sample matrix. If
particular circumstances demand the use of a cleanup procedure, the analyst must
determine the elution profile and demonstrate that the recovery of each compound of
interest for the cleanup procedure is no less than 85%.
12. Liquid Chromatography
12.1 Table 1 summarizes the recommended operating conditions for the liquid chromatograph.
Included in this table are the estimated retention time and method detection limit that
can be achieved by this method. An example of the separation achieved by this column
is shown in Figure 1. Other HPLC columns, chromatographic conditions, or detectors
may be used if the requirements of Section 8.2 are met.
12.2 Calibrate the system daily as described in Section 7.
12.3 If the internal standard approach is being used, add the internal standard to sample
extracts immediately before injection into the instrument. Mix thoroughly.
12.4 Inject 10 pL of the sample extract. Record the volume injected to the nearest 0.05 pL, and
the resulting peak size in area or peak height units.
12.5 The width of the retention-time window used to make identifications should be based
upon measurements of actual retention-time variations of standards over the course of
a day. Three times the standard deviation of a retention time can be used to calculate
a suggested window size for a compound. However, the experience of the analyst
should weigh heavily in the interpretation of chromatograms.
12.6 If the response for the peak exceeds the working range of the system, dilute the extract
and reanalyze.
12.7 If the measurement of the peak response is prevented by the presence of interferences,
further cleanup is required.
13. Calculations
13.1 Determine the concentration of carbendazim in the sample.
13.1.1 If the external standard calibration procedure is used, calculate the amount of
material injected from the peak response using the calibration curve or calibration
factor in Section 7.2.2. The concentration in the sample can be calculated as
follows:
-------
Method 631
Equation 2
(A) (V)
Concentration, \ig/L -
(Y) (Vs)
where
A = Amount of material injected, in ng
Vt = Volume of extract injected, in {iL
Vt = Volume of total extract, in {iL
Vs = Volume of water extracted, in mL
13.1.2 If the internal standard calibration procedure was used, calculate the
concentration in the sample using the response factor (RF) determined in Section
7.3.2 as follows:
Equation 3
(V (O
Concentration, ue/L =
(Ais) (RF) (Vo)
where
As = Response for parameter to be measured
Ats = Response for the internal standard
Is = Amount of internal standard added to each extract, in jig
V0 = Volume of water extracted, in L
13.2 If the sample was treated to hydrolyze benomyl, report the results as benomyl (measured
as carbendazim). If the hydrolysis step was omitted, report results as carbendazim.
Report results in micrograms per liter without correction for recovery data. When
duplicate and spiked samples are analyzed, report all data obtained with the sample
results.
13.3 For samples processed as part of a set where the laboratory spiked sample recovery falls
outside of the control limits in Section 8.3, data for the affected parameters must be
labeled as suspect.
-------
Method 631
14. Method Performance
14.1 The method detection limit (MDL) is defined as the minimum concentration of a
substance that can be measured and reported with 99% confidence that the value is above
zero.9 The MDL concentrations listed in Table 1 were determined by extracting 1000-mL
aliquots of reagent water with three 350-mL volumes of methylene chloride.1
14.2 In a single laboratory, West Cost Technical Services, Inc., using reagent water and
effluents from publicly owned treatment works (POTW), the average recoveries presented
in Table 2 were obtained.1 The standard deviations of the percent recoveries of these
measurements are also included in Table 2. All results were obtained using the same
experimental scale described in Section 14.1.
-------
Method 631
References
1. "Pesticide Methods Evaluation," Letter Report #17 for EPA Contract No. 68-03-2697.
Available from U.S. Environmental Protection Agency, Environmental Monitoring and
Support Laboratory, Cincinnati, Ohio.
2. "Development of Analytical Test Procedures for Organic Pollutants in
Wastewater-Application to Pesticides," EPA Report 600/4-81-017, U.S. Environmental
Protection Agency, Cincinnati, Ohio 45268. PB #82 132507, National Technical
Information Service, Springfield, Virginia.
3. ASTM Annual Book of Standards, Part 31, D3694, "Standard Practice for Preparation of
Sample Containers and for Preservation," American Society for Testing and Materials,
Philadelphia, Pennsylvania, p. 679, 1980.
4. "Carcinogens—Working with Carcinogens," Department of Health, Education, and
Welfare, Public Health Service, Center for Disease Control, National Institute for
Occupational Safety and Health, Publication No. 77-206, August 1977.
5. "OSHA Safety and Health Standards, General Industry" (29 CFR 1910), Occupational
Safety and Health Administration, OSHA 2206 (Revised, January 1976).
6. "Safety in Academic Chemistry Laboratories," American Chemical Society Publication,
Committee on Chemical Safety, 3rd Edition, 1979.
7. "Handbook for Analytical Quality Control in Water and Wastewater Laboratories,"
EPA-600/4-79-019, U.S. Environmental Protection Agency, Environmental Monitoring and
Support Laboratory, Cincinnati, Ohio, March 1979.
8. ASTM Annual Book of Standards, Part 31, D3370, "Standard Practice for Sampling
Water," American Society for Testing and Materials, Philadelphia, Pennsylvania, p. 76,
1980.
9. Glaser, J.A. et al. "Trace Analysis for Wastewaters," Environmental Science & Technology,
15, 1426 (1981).
-------
Method 631
Table 1. Chromatographic Conditions and Method Detection Limits
Retention Time Method Detection Limit (ng/L)
Parameter (min)
Benomyl (as carbendazim) — 25.0
Carbendazim 8.1 8.7
Column conditions: |i Bondapak C18 (10 |im) packed in a stainless steel column 30 cm long by
4 mm ID with a mobile phase flow rate of 2.0 mL/min at ambient temperature.
Mobile phase: methanol/water (1 + 1).
Table 2. Single-Operator Accuracy and Precision
Number
Average
Standard
Sample
of
Spike
Percent
Deviation
Parameter
Type
Replicates
(m/L)
Recovery
(%)
Benomyl (as carbendazim)
DW
7
51.5
70
15.5
MW
7
51.5
78
8.8
MW
7
103
99
6.4
Carbendazim
DW
7
50
106
5.5
MW
7
50
117
18.5
MW
7
100
108
11.3
DW = Reagent water
MW = Municipal wastewater
-------
Method 631
Carbindazim
10
Retention Time (minutes)
A52-002-62A
Figure 1. Liquid Chromatogram of Carbendazim on Column 1
(for conditions, see Table 1)
------- |